RECENT TRENDS IN CATARACT SURGERY

ANAESTHESIA FOR CATARACT SURGERY: Anaesthesia for cataract surgery has progressed from general anaesthesia (1846), surface anaesthesia with cocaine (Koller, 1884), retrobulbar block (Knapp, 1884), supplemental facial blocks (Van Lint) to peribulbar block (Kelman and davis, 1985), subconjunctival (Furata et al.), topical and no anaesthesia cataract surgery.

LOCAL ANAESTHESIA: Retrobulbar and peribulbar blocks: They are preferred modes considering the motor and sensory nerves emerging and being distributed from a small area in proximity with the orbital apex. Now, the existence of a separate anatomical entity, so called “retrobulbar cone” is being questioned. So, the definition of these blocks has become blurred. Authors suggest a retrobulbar and non-retrobulbar effect of a block The factors causing a retrobulbar effect are posterior needle placement behind the equator of the eye, use of hyaluronidase and rapid injection rate.The classical retrobulbar blocks have been replaced with more anteriorly placed injections using shorter needles and smaller volume of anaesthetic, which are safer and ensure sufficient analgesia and motor paralysis. Facial nerve block: It is used as a supplemental to peribulbar block for adequate orbicularis akinesia Nadbath block: blocks facial nerve at exit from stylomastoid foramen (2mm anterior to superior border of mastoid) O’Brien block: blocks temporal facial branches as they emerge through the parotid (2mm anterior and 1mm inferior to the external auditory meatus) Atkinson block: blocks zygomatic branches (at inferior border of zygoma) Van Lint block: blocks terminal branches (1 cm lateral to lateral canthus) Modified Van Lint block: to keep the optic nerve flaccid and out of the way. Vertically 1 cm temporal to lateral canthus followed by subcutaneous infiltration of both the lids. Technique: The newer refinements were Shorter needles(30 mm as opposed to older 38 mm ) for retrobulbar effect as well as for anterior peribulbar injections. Larger gauge sharp needles replaced thicker blunt needles( which were more traumatic, less flexible with increased risk of globe perforation) Bevel of needle is kept towards the globe to decrease perforation risk. Patient is asked to look straight up, with globe in neutral positionto keep the optic nerve flaccid and out of the way. Slow injection of the drug to displace blood vessels and reduce bleeding risk. Concept of ‘painless injections’- Transconjunctival approach after topical anaesthesia and pre injection of BSS and lignocaine.

ARCHITECTURE OF CATARACT INCISION: The surgical wound is no longer just a portal of entry, but has enmerged as an important tool that influences the final attainment of good uncorrected visual acuity.

Wound construction in phacoemulsification: Technical advances have reduced the wound incision size required for safe extraction allowing the option of no-stitch cataract surgery.

Scleral tunnel incision- scleral pocket incision (With internal corneal lip) Clear corneal incision SCLERAL TUNNEL INCISION: (Richard Kratz) Two step incision that begi.s more posterior to the conventional limbal incision. Tunnel is fashioned in the sclera and corneal ledge may be created internally which makes it self-sealing. The configuration may be external or internal. EXTERNAL INCISION: Curvilinear incision: This refers to the traditional incision following the limbus. There is no support to prevent the inferior edge from falling away from the superior edge. This gape causes against- the –rule astigmatism. Straight incision: The two extreme points of the incision are secured in the sclera and the inferior edge of the incision, directly adjacent to these end points cannot sag. Eg. Koch’s basic incision and Kratz scleral pocket incision. Frown and Chevron incisions: Ends of incision superiorly in sclera, makes it more stable. In frown, the ends are swept superiorly in a curved fashion, which supports the inferior edge and prevents astigmatism. Chevron incision is fashioned using two straight incisions. CONCEPT OF ‘INCISIONAL FUNNEL’: According to Koch’s work and Sander’s analysis,the corneal astigmatism is directly proportional to the cube of the length of incision and inversely proportional to the distance of incision from the limbus. The incisional funnel is thus, an imaginary pair of curved lines diverging from the limbus, representing therelationship between the astigmatism and the incision length.Incisions made within the incision funnel are astigmatism-free. INCISIONAL GAPE: A wound gape may exist due to the scleral elasticity or scleral contraction following cautery. If the wound gapes, communicating with the anterior chamber, there is possibility of alteration in corneal shape and astigmatism. The corneal stability is provided by the internal incision and not by the external groove and the tunnel.

INTERNAL INCISION: It is the real site for corneal stability, the external incision and suturing affecting astigmatism by alteration in the internal configuration of the wound.Koch’s basic incision and Kratz scleral tunnel are located 1mm and 2mm behind limbus respectively, but have the same internal incisions (both have a small variable length of corneal lip) Scleral tunnel with internal corneal lip: 3 step incision in which dissection is carried further into the clear cornea to achieve a corneal lip sealing the entry wound. The sealing effect increases with increase in intraocular pressure. No sutures are required. Incidence of wound leak, hyphema and iris prolapse are lesser. Against the rule astigmatism may result because of scleral disinsertion due to a deep initial groove. Limitations include need for conjunctival flaps, need for cautery and long tight scleral pockets ( phaco hand pice may distort cornea and compromise view)

CLEAR CORNEAL INCISION: These self sealing 3 step corneal valve incisions

Temporal limbus-the preferred site because the distance of temporal limbus and the visual axis is the longest(flattening around the wound being less likely to cause flattening at visual axis). Also they are refractively more stable, may not require a bridle suture, provide greater access, minimal pooling of fluid, beneficial in patients with filtering bleb, decrease in surgical time and suitable for topical anaesthesia cataract surgery.

SMALL INCISION TECHNIQUES: Non- phaco small incision techniques. Phacoemulsification. Future trends.

NON-PHACO SMALL INCISION TECNIQUES: Phaco fracture technique: (Kansas) Fracturing the nucleus in the anterior chamber using vectis and nucleotome, the fragments removed via 6mm scleral pocket incision. Phacosandwich incision: (Fry) Nucleus sandwiched between a lens loop and spatula via 7 mm incision Intraocular cataract scissors: (Perkins) To divide the nucleus into smaller fragments in the anterior chamber and removed via 7.5 incision. Hydrosonic delineation: (Anis) Hydrodelineation cannula used to delineate the nucleus, the nucleus removed manually or by phacoemulsification. Blumenthal’s technique: Hydroexpression of nucleus using an anterior chamber maintainer.

PHACOEMULSIFICATION: (Charles Kelman) The advances in surgical techniques, IOL manufacturing and better understanding of the machine has helped to make phacoemulsification a very safe and controlled technique. The small self sealing incision produces refractively stable eyes with rapid rehabilitation. PHACOEMULSIFICATION MACHINE: Cataractous lens is emulsified with ultrasonic agitation of a titanium needle.The needle makes to and fro excursion, and with each thrust, the needle point will pass into the nucleus before its inertia is overcome. This high acceleration of the needle makes it more effective than other cutting devices. The machine has 2 basic components: PHACO POWER: The cutting power is generated by the titanium needle which is the tip of the phaco probe. The phaco acts as a sophisticated transducer converting electrical to mechanical energy. The titanium oscillates at a frequency of 40 KHz per second .The excursion made by the needle is the stroke length. The stroke length and the frequency of the needle determine the cutting power.ASPIRATION SYSTEM: Three types are peristaltic pump, venture pump and diaphragm pump.Peristaltic pump works only when the port is occluded, and is self limiting, in a way. The other 2 systems do not depend on occlusion to build up vacuum, and vacuum is generated depending on the travel the foot pedal makes. It is quicker but more risky. INDICATIONS OF PHACOEMULSIFICATION: The extent of visual disability rather than the percentage loss determines the timing of surgery. All cataracts with reasonably dilated pupils may be feasible (except very brunescent and black cataracts). Patients who demand quick rehabilitation and astigmatism free vision are benefited maximum. Also preferred in elderly who want a greater wound stability in a short time. CONTRAINDICATIONS: Corneal endothelial compromise, small pupil, dense cataract and microphthalmos, microcornea are not suitable for this technique.

Advantages of phacoemulsification: Intraoperative environment is well controlled and stable, within the eye. It employs a self-sealing incision with minimal chances of uveal touch and expulsive choroidal haremorrhage. ‘No stitch’ incision produces a secure, stable wound. The induced astigmatism hence, is minimal with early stabilization Immediate rehabilitation and no postoperative restrictions. Compatible with small size implants In the bag fixation of IOL after “in situ” phacoemulsification, has been made safer after the advent of capsulorrhexis. Better understanding of the machine, surgical techniques and improved technology have made it very effective and safe.

TECHNIQUE: Self-sealing or ‘no-stitch’ small incision: A scleral tunnel incision is more popular. Initially, incision is placed through half the scleral thickness 1.5-2 mm away from the limbus. Dissection is carried out in the sclera and 1mm inside the cornea. The internal incision is made through Descemet’s membrane creating a strip of Descemet’s (which acts as a self-sealing valve). Whenever IOP rises, this valve closes the incision more effectively.

Anterior capsulotomy: Under viscoelastic, 6mm sized capsulorhexis is performed with a 26 G needle, a puncture made in the centre and then traversing to the left. A small flap is fashioned and then everted, which is pulled to create a continuous opening. It can be done with forceps. Hydrodissection: BSS injected under the anterior capsule about 1mm from rhexis margin.A fluid wave is seen traversing the cataract. This separates the cataract from capsular bag. Hydrodelineation reduces the volume of the nucleus and demarcates an epinuclear bowl around the firmer central nucleus.

The nucleus fracture techniques: Nucleus removal -soft cataract : Less phaco power and more vacuum are utilized for aspiration. A bowl of nucleus is prepared with few sculpting maneuvres. The bottom of the bowl is shaved until a very thin plate remains. Then the equatorial chunk is engaged and flipped into the phaco tip. Nucleofractis technique for firm and hard nucleus: Howard Gimbel is considered the Father of all the nuclear cracking procedures. John Shepherd extended the divide and conquer technique to quadranting. After capsulorhexis, hydrodissection and nucleus rotation, phaco is begun by aspirating the superficial cortex and preparing for sculpting. After sculpting a deep groove from 12 to 6’o clock, it is rotated by 90 deg to carve another groove. After making 4 grooves or trenches, the nucleus is cracked at the base of each groove. The 4 quadrants are brought to the papillary plane and phaco aspirated. Chip and flip technique: Devised by Howard Fine. After a cortical cleaving hydrodissection and hydrodelineation, central sculpting is done. The inner nucleus bowl is converted into a chip by removing the peripheral rim. A second instrument is introduced between the nuclear bowl (‘chip’) and outer epinuclear bowl, and is swept under the chip, elevating it in the centre of the capsular bag and is removed. The softer epinuclear bowl is displaced from the capsular fornix at 5 or 6’0 clock. Using phaco tip in aspiration mode, epinuclear bowl is loosened by pulling the rim at 5 or 6’o clock towards 12’o clock and pushing with the second instrument in the bottom of the epinuclear bowl towards 5 to 6 ‘o clock to tumble or flip the soft epinuclear bowl. By flipping the bowl away from posterior capsule, it can be removed safely by aspiration or low powers of emulsification.

Stop and chop technique: Devised by Nagahara. The nucleus is split into quadrants with the help of an instrument called phacochopper. Basically it is a modification of peripheral cracking without pregroooving. In stop and chop, like 4 quadrant cracking, an initial trench is made towards 6’o clock. The nucleus is cracked into two halves with a chopper and then is chopped. One nucleus half is rotated and phaco tip is buried into it, being held by vacuum. The chopper is buried into the periphery of the nucleus and pulled towards the phaco tip. Nucleus splits as the chopper is brought nearer the phacotip. This is repeated in the other half .Each nuclear half can be chopped into small pieces which can be removed easily by gentle emulsification using more vacuum and minimal phaco power. It can be called trench, stop and chop. In hard nucleus, crater is produced and small pieces are chopped off, which becomes crater, stop and chop.Phaco Chop:

Phaco chop divides the nucleus without sculpting and allows removal of firm-to-hard nuclei faster and with less energy compared to divide and conquer. Phaco chop is performed with either a horizontal or vertical approach and selection between the two depends on features of the cataract. Horizontal chop is used for softer nuclei as well as in high myopes, other eyes with a large anterior chamber, when there has been prior vitrectomy or if the zonules are weak. Vertical chop is performed when an epinucleus is absent since there is an increased risk of capsule rupture with horizontal chop; vertical chop approach is also preferred for very hard, dense nuclei

Cortex removal: Peripheral cortex is aspirated using irrigation- aspiration probe. Care should be taken as this step more often causes posterior capsule rupture than nuclear fragmentation. Capsule cleaning: The anterior and posterior capsule can be cleaned by the irrigation- aspiration tip. Routine vacuum cleaning of the posterior capsule leaves behind a cleaner capsule. Endocapsular phacoemulsification: A small mini-capsulorrhexis is produced and the entire procedure is done within the capsular bag. Single handed Vs bimanual technique: The second instrument gives a better control and maneuverability. It stabilizes the lens, guides the lens fragments to the tip, rotates and maneuvers the nucleus and protects the capsule. The modern technique of cracking would require a 2 handed technique. IOL implantation: The small size PMMA lens has an optic diameter of 5 or 5.5 mm and overall size of 12mm.

The basic power settings are continuous, pulse, and burst. The continuous power setting delivers energy continuously, with variable power, depending on how long the foot pedal is depressed. The maximum power setting can be preset, thus allowing surgeons to control the maximum amount of phaco power delivered. In other words, the longer the foot pedal is depressed, the greater the phaco power.

In pulse mode, the pulses of energy dispensed have variable power, depending on how long the foot pedal is depressed. The longer it is depressed, the greater the power of each sequential pulse of energy. The defining feature of pulse mode is that after each pulse of energy is delivered, a period occurs during which no energy is supplied between increasing pulses of energy, which is the ‘‘off’’ period. Alternating between the ‘‘on’’ and ‘‘off’’ periods reduces heat and dispenses half the energy into the eye.

Finally, in burst mode, each burst of energy has the same amount of power, but the interval between each burst increases as the foot pedal is depressed. The longer the foot pedal is depressed, the shorter the ‘‘off’’ period will be between each burst. As a result, at maximum depression of the foot pedal, the delivery of energy will be continuous. Although, the basic power modulations are effective at decreasing phaco energy, they are limited in their degree of programmability. Thus, with the advanced, or hyper, settings, an additional set of options can be programmed for the pulse and burst modes. For example, in hyperpulse mode, the rate can be as high as 120 pulses per second, compared with 20 pulses per second in basic pulse mode. The

hyperpulse mode provides surgeons the feeling of continuously delivering energy. This setting also allows each burst to be set as low as 4 ms, whereas in the basic power setting, each burst is set at 80 ms.

NEWER TECHNOLOGIES IN PHACO: Sonic phacoemulsification ( Wave, STAAR surgical) : Operates on sonic frequency (40-400 Hz) with an optional ultrasound mode (25-62 Hz) No frictional heat is generated as intermolecular friction is minimal No cavitational effect.(true fragmentation rather than emulsification Suitable for p to grade 3 nucleus Neosonix (Legacy, Alcon)

"Neosonix is a hybrid technology based on a specialised handpiece that combines both conventional linear ultrasound and lowfrequency rotational oscillations of the hand-piece tip," Mean total ultrasound time is reduced in neosonix. This allows surgeons to reduce the amount of potentially harmful thermal energy that can come from exposure to too much high-frequency ultrasound. Phaco tip has a variable oscillation of up to 2 deg on either side at a frequency 120 Hz. Lower frequency reduces thermal damage of ocular structures. Therefore, it covers a larger area during fragment removal and assists in breaking the fragments with its mechanical energy. The oscillations also constantly reorient the nuclear segments at the tip , thus reducing the need fora second instrument .and doesn’t make it move away from the tip, therefore, there is a marked reduction in repulsion at the tip. The energy used is markedly reduced as there is very little wastage and chances of wound burn is reduced due to less production of heat from the wastedultrasonic energy as well as the energy produced at the wound is almost one – third.

May be used in combination with ultrasound for effective nuclear management. Micropulse (Whitestar, Allergan) A power modulation of conventional pulse mode to reduce heat generation and maximize efficiency. The duration of energy pulse is reduced and is lesser than the thermal relaxation time of the tissues. This reduces risk of corneal burns. Also enables use of phaco tip without an irrigating sleeve asa in bimanual phacoemulsification. Burst mode: Enables use of 100% phaco power in short bursts (100 millisec)Which allows efficient use of ultrasound to sculpt a hard nucleus. Lesser heat generation than in continuous and pulse mode in dense nuclear cataract.

PHACO TRENDS AND FUTIRE DIRECTIONS: There has been an increasing interest in clear corneal incisions and in topical anaeasthesia (without blocks). Smaller and smaller phaco probes have been made to enable the surgeon to operate through less than 3 mm incision.Small size foldable IOLs are increasingly popular. There are 2 exciting new areas –removal of cataract by laser or by an extremely controlled rotating magnet.

Evolution of phaco ultrasound technologyTraditional longitudinal ultrasound – micropulse cold phaco – transverse (Ellips transversal ultrasound) and torsional phaco (ozil technology)Advantages of torsional or transverse phaco

- increased cutting efficiency by emulsifying lens material in more than one direction- reduce repulsion of nuclear material - increase followability - reduce energy and trauma

cold phaco With new technologies available cataract surgeons will be performing procedures with incisions as small as 1.0mm. With traditional phaco, wound burns are often a real possibility. The new cold phaco technology reduces risk to the patent and may enable better recovery.RECENT ADVANCES IN PHACO:

• Advances in phaco motion - OZIL

• Advances in phaco incisions -

Phakonit - 1 mm incision (Amar Agarwal) MICS (Microincision cataract surgery ) – Jorge Alio Microphaco – 0.8 mm incision (Randall Olson) Microphaconit-0.7 mm (Amar Agarwal)

TECHNIQUES:

PHAKONIT : (Amar agarwal) The name PHAKONIT has been given because it shows phaco (PHAKO) being done with a needle (N) opening via an incision (I) and with the phako tip (T). This is also because it is Phako being done with a Needle Incision Technology.SYNONYMS:

1. Bimanual phaco2. Microincision cataract surgery3. Microphaco4. Bimanual microphaco5. Sleeveless phaco

Sleeveless phaco technique. The irrigation is combined with a chopping instrument which enables a parallel fluidic system. Incision size 0.9 – 1.2 mm. A thinner phaco tip enables incision of 0.7 mm. Disadvantages include corneal burns by micropulse delivery of ultrasound energy. This reduces the use of ultrasound energy to the minimum and reduces temperature rise. The fluidic requirements are only partially met using choppers ( lesser bore dimension than phaco tip) Inorder to counter the chamber fluctuations, modifications include use of an air pump which increases the irrigation pressure and fluidic alterations, to incorporate a feedback loop to prevent collapse using mechanical and difital devicesThinoptx the company that manufactures these lenses has patented technology that allows the manufacture of lenses with plus or minus 30 dioptres of correction on the thickness of 100 micronsThe lens is made from off-the-shelf hydrophilic material, which is similar to several IOL materials already on the market. The key to the Thinoptx lens is the optic design and nano-precision manufacturing. The basic advantage of this lens is that they are Ultra-Thin lenses

Another technique by which one can perform Phakonit is to use an anterior chamber maintainer. The authors started this technique. They call it THREE-PORT PHAKONIT.FUTURE TRENDS IN NUCLEAR SCULPTING: PHACOFLY (KELMAST) Kelmann electromagnetically assisted surgical technique. It involves injection of a tiny magnetic rod (magnobit) into the lens

The rod is then rotated inside the nucleus using 3 electromagnets placed at equal distances from the limbus and a fourth under the patient’s head. As the lens material is emulsified, it is aspirated out of the eye and a second rounded bead is introduced to polish the capsule. The intact capsular bag allows the injection of clear collagen till visualization of retinal vessels occurs through a lens emmetropic. LASER PHACOLYSIS: The 2 principal laser systems are the Nd YAG and Erbium YAG

Nd: YAG : (1064 nm) DODICK LASER

Principle: It is based on formation of shock waves and plasma generation resulting in ‘photodisruption’. This causes emulsification of lens matter and facilitates removal. Plasma initiation occurs when a high concentration of photons cause ionization of few molecules of a target. The released electrons are accelerated by the laser light which causes further ionization till a large number of rapidly moving molecules are produced, the “optical breakdown” phenomenon. The great velocity of the molecule cause a rise in temperature (over 20,000 K) which causes a microexplosion within the tissues and results in plasma production. Metals have a low threshold for optical breakdown and may be used to initiate plasma formation at low input energy. This principle is used in Dodick laser system by using a Titanium placed at the focal point of the laser. This causes the formation of shock waves (well over the speed of sound) and causes clinical disruption.The systems are of 2 types: Direct acting: Laser disruption of tissue is direct with a laser collecting system,which increases efficiency of energy utilization. Cooling is required to reduce heat production and prevent tissue damage. Indirect acting: This uses a Titanium target inside the tip towards which laser light is directed. The target acts as a transducer converting light energy to mechanical shock waves which disrupt the nuclear material held at the tip of the aspirating port. This allows for the safe direction of laser energy and prevents damage to surrounding tissue. So causes lesser heat production and does not require cooling arrangements. LASER: Pulsed (Q switched) Probe has an incorporated aspiration function Each pulse releases 12mJ of laser energyof 14 nanosec duration Delivery system uses a quartz fibreoptic probe.

TECHNIQUES: Preslicing and lasing (Dodick technique) : The nucleus is presliced into 3 quadrants and each quadrant lifted out, lased and aspirated. Wehner’s spoon: This involves lifting of the nucleus out of the bag and back-cracking it over the infusion cannula. This is rechopped , lased and aspirated. Divide and Conquer: (Zerdab) Central nucleus is sculpted and divided after which each hemisphere is lifted out and lased. Central nucleus ablation: (Raut’s) It is usedc for dense grade 4 nucleus pulsing the central core within the bag, followed by collapsing the walls of the epinucleus and aspirating it. No hydrodissection or hydrodelineation is performed.

ADVANTAGES: Safe for cornea, iris and posterior capsule Minimal heat production Smaller and safer wound Low cost Same tip can be used for the cortex ( no need to change tips after nucleus emulsification)

DISADVANTAGES: Difficult in harder cataracts Different surgical procedure using a bimanual technique.

Erbium : YAG (2940 nm) :

PRINCIPLE: Tissue water absorbs the laser energy as heat and at temperature greater than 100 °c which cause , vaporization of water occurs. The dramatic expansion of volume results in formaton and collapse of vapor cavities, leading to tissue damage. Acoustic transients (pressure waves) are also produced which cause secondary mechanical damage. With increasing hardness, lens proteins coagulate making phacolysis extremely difficult. Erbium : YAG It has the highest energy absorption in water for any kind of laser in clinical use. This results in high energy absorption by the high water content of ocular tissues and a reduced thermal effect on other tissues, enhancing its safety. Laser can be easily delivered using fibreoptics. Pulsed laser is used to vaporize and phacofragment high water content lens material out of the eye. Each pulse causes a rapid localised heating and vaporization creating a bubble at the tip of the fibre. The size of the bubble depends on the energy used and is about 1 mm at 1mJ. As surgery proceeds, there is continued protein coagulation resulting in hardening of the lens making tissue emulsification more difficult. The fibres are made of fluoride or Zirconium based materials. A nucleus manipulator is used to feed and stabilize the lens fragments close to the laser probe.

ADVANTAGES: Good absorption in water Safe to the surrounding tissue

DISADVANTAGES: Slow ablation Progressively hardens lens proteins (emulsification progressively more difficult) Fragile and expensive fibreoptics Not suitable for hard nuclei Temperature rise OTHERS: (under trial) Nd: YLF (1047) 1053 nm with picosec pulses Excimer lasers (193, 248, 308, 351 nm)

OZIL TECHNOLOGY :

• First introduced at the ESCRS meet at Lisbon, Portugal in 2005.

• Traditional ultrasound is inefficient in 2 ways: It constantly pushes the nuclear material away by the jackhammer effect and it performs effectively only half the time, because it emulsifies material only on forward stroke while energy is wasted on backward stroke.

• Torsional phaco (in OZIL) uses an ultrasonic oscillatory movement of the phaco tip instead of the forward-and-backward cutting action used in traditional longitudinal phaco.

• It is the oscillatory movement of the torsional tip that creates a shearing motion that results in more constant contact of the tip with the nucleus

Adv of torsional phaco are-

• minimizes repulsion or chatter of nuclear material, thereby increasing followability

• Improved effectiveness- Torsional phaco is performed with ultrasound operating at about 32 KHz, lower than the 40 KHz used in traditional phaco, but because of constant contact with the nucleus and no backward stroke, every cut can shear away lens material while reducing repulsion at the same time.

• The geometry of the Kelman tip ensures that the rotational movement at the incision is only half that of traditional phaco. Hence only half the energy is used in OZIL as compared to traditional phaco and only one third heat production occurs

• Better for flaccid iris as there is excellent followability allowing the Phacotip to stay in the center preventing chaffing of the iris

• No learning curve in shifting from traditional to torsional phaco and no pulse or burst modes required.

PHACOTMESIS :

• Introduced by Aziz Anis

• uses both longitudinal and rotational motion at the handpiece tip

• It combines a piezoelectric handpiece with a hollow shaft motor that creates motion similar to a vitreous cutter.

MICROINCISION CATARACT SURGERY: Uses incision size smaller than 1 mm ( 1000 microns) MICS has revolutionized cataract surgery by providing advantages of wound stability, improved control and reduced chamber turbulence resulting in early visual rehabilitation ( lesser induced optical aberrations) and improved results. It offers the benefits of a parallel fluidic system which provides a safer micro-environment within the eye. It is used as a tool to manipulate nuclear fragments and makes it safer than the coaxial system with fewer complications such as posterior capsular rupture and corneal endothelial damage. TECHNIQUES:

PHAKONIT : (Amar agarwal) The name PHAKONIT has been given because it shows phaco (PHAKO) being done with a needle (N) opening via an incision (I) and with the phako tip (T). This is also because it is Phako being done with a Needle Incision Technology.SYNONYMS:

6. Bimanual phaco7. Microincision cataract surgery8. Microphaco

9. Bimanual microphaco10. Sleeveless phaco

Sleeveless phaco technique. The irrigation is combined with a chopping instrument which enables a parallel fluidic system. Incision size 0.9 – 1.2 mm. A thinner phaco tip enables incision of 0.7 mm. Disadvantages include corneal burns by micropulse delivery of ultrasound energy. This reduces the use of ultrasound energy to the minimum and reduces temperature rise. The fluidic requirements are only partially met using choppers ( lesser bore dimension than phaco tip) Inorder to counter the chamber fluctuations, modifications include use of an air pump which increases the irrigation pressure and fluidic alterations, to incorporate a feedback loop to prevent collapse using mechanical and difital devices

LASER PHACOLYSIS: It is done using incision size of 1.2 mm. Advantages include lack of temperature rise and reduced risk of corneal burns.

AQUALASE: This uses a jet of fluid to emulsify the hard nucleus and allow aspiration through a small incision. A small pulse of preheated fluid at 57 deg emulsifies the nuclear fragments.. The tip used has a flare of 1.1 mm with an outer diameter of 1.32 m. Pulses are upto 100 per second. Temperature rise is avoided using irrigation fluid 2 deg celsius lower than normally used. The risks of posterior capsular rupture is lower as it avoids micro-implosions and turbulence seen in phacoemulsification.

HACC TECHNIQUE: (High Aspiration Controlled Chop) It is independent of energy based phacolysis. It is a pre-chop, zero phaco technique which allows easy removal of dense nuclear cataracts. This has no risk of thermal burns, endothelial cell loss and posterior capsular rupture. This is a sub millimeter technique which may be done just by using an irrigation-aspiration device. There is no need for phaco hand piece, allowing a low cost surgery. INTRAOCULAR LENSES- RECENT ADVANCES:

THE EVOLUTION:

TYPE

I Original Ridley’s posterior chamber PMMA IOL

II Early rigid anterior chamber lenses

III Iris supported lenses

IV Modern anterior chamber lenses

V Posterior chamber lenses

VI Refractive IOLs (capsular IOLs)

1. Haptic material: Polypropylene haptics were replaced by PMMA. Polypropylene causes greater inflammation by complement activation and it promotes the adherence of microorganisms. Also it has less “plastic memory” resulting in decentration. Other haptic materials are Polyamide, Dacron, Mersilene and polyimide.

2. Single piece all PMMA lenses: These are lathe cut from a single sheet of PMMA.

It has excellent centration due to increased rigidity and plastic memory. Lack of optic-haptic junction results in lesser inflammatory cells adhering to the lens.

3. Haptic configuration: Available designs include J shaped, modified J and C shaped.The broad haptic contact with the equator of the lens capsule reduces wrinkling and decentration. Foldable IOLs have plate haptics with fixation holes

4. Optic design: Biconvex design reduces spheric and chromatic aberrations and internal reflections. The posterior convex portion is in contact with the posterior capsule and helps prevent PCO. Larger optic size 6-7mm is forgiving for decentration, less chance of pupillary capture and prevents optical aberrations due to deflection of light from lens edge.

5. Lens edge design:Square edge optic design is associated with a lower rate of PCO.

Square back edge abuts into the surface of the capsule and preventing cells from proliferating across the capsule beneath the lens. A rounded front edge reduces internal reflections and sloping side edge minimizes edge glare.

6. Laser ridge: Complete or incomplete ridges rimming the posterior optic. It was initially introduced to reduce migration of lens epithelium posteriorly. This barrier was found ineffective and may actually enhance PCO due to lack of contact inhibition. It provides a space between optic and the posterior capsule and facilitates Nd: YAG capsulotomy by separating the capsule from the lens surface, avoiding pit marks.

7. Posterior angulation of IOL: Angulation of 3-10° was introduced to reduce the incidence of pupillary capture and iris chaffing.

8. Ultraviolet absorbing chromophores:

Also called ‘blue blockers’ and have been incorporated into the material of the IOL to reduce the incidence of retinal damage Eg. Benzophenone & benzotriazole

9. Suture fixation lenses: For scleral fixation of the IOL in the ciliary sulcus These lenses have eyelets moulded into the inside curve of the haptic to facilitate suture attachment.

10. Special use IOLs with opaque flanges: It helps to reduce glare in conditions like aniridia and coloboma.

11. Surface modification :(With heparin / fluorine) Reduced the incidence of cell & pigment deposits on the lens surface following postoperative inflammation.

12. Piggy back IOLs was introduced by Gayton in 1993 in a case of microphthalmos. Can provide optical correction for patients requiring high IOL power Secondary correction of undesirable optical results after cataract surgery and IOL implantation. (ADD-ON LENS) Used in infantile eyes after cataract surgery to manage the changing refractive status of these eyes Higher power lens is placed more posterior in the capsular bag & the lower power lens is in the bag or sulcus.

Facilitates lens exchange for refractive adjustment postoperatively. PMMA or flexible IOLs can be used.

Complications include Hyperopic shift Interlenticular opacification ( “red rock syndrome”)

PMMA LENS: PMMA is an inert polymer manufactured through polymerization of methacrylic acid and

methylester.

Specific gravity-1.19 and refractive index-1.497

It is hard, to be inserted through large incision, hydrophobic & may damage corneal endothelium.

PMMA lenses melt with heat sterilization; sterilized using ethylene oxide.

It can be manufactured by: Lathe cutting Compression molding Compression polymerization Cast molding Injection molding

FOLDABLE IOL : Thomas Mazzocco introduced the first foldable lens in 1984 made of silicone by

STAAR Surgical, Monrovia.

The initial design was an oblong lens with round optic bracketed between 2 webbed square haptics. When placed in the capsular bag, the lens tended to elbow out with contraction of capsular space.

The initial material (STAAR RMX 1) was opalescent with a high particulate content distorted the He-Ne beam during YAG procedures making capsulotomy difficult. This was exacerbated with the proximity of silicone lens to the posterior capsule which damaged the lens. A newer clearer material (STAAR RMX -3) was developed with plate haptics for sulcus fixation. But it led to “propelling” of the lens with pigment dispersion and secondary glaucoma.

Different materials available now are silicone elastomers, hydrogel acrylic (or hydrogels), and non-hydrogel acrylic (or acrylics)which differ in their refractive indices, water content, surface properties, clarity and mechanical strength.

SILICONE LENSES:o Synthetic polymers having a linear, repeating silicon-oxygen backbone. They

belong to a group called polyorgano-siloxanes.o Certain organic groups like methyl, phenyl or fluoroalkyl can be linked to

manufacture a variety of products.o High chemical inertness, thermal stability & resistance to oxidation.o Silicone oils are linear chains of Poly Dimethyl Siloxane (PDMS) and silicone

gels have lightly crosslinked polysiloxane networks swollen with PDMS fluid to produce a cohesive mass.

o Silicone elastomer, with little PDMS fluid is created by crosslinking, catalysed by Platinum and has a mol wt of 7000.

o Light transmission 91. It is hydrophobic and hence can be easily folded for insertion through a small incision.

Advantages: Autoclavable Decreased trauma to intraocular structures Compressible & excellent memory (ability to return to original shape after deformation)

Disadvantages:• Low tensile strength ( to be handled carefully to avoid tearing)• Low refractive index (1.41-1.46), hence thicker with uncontrolled opening inside

the eye.• Discolouration to tan brown.• CI in diabetic retinopathy patients who are likely to undergo vitrectomy with

silicone oil injection (Which tends to adhere to the lens).

Hydrogel lenses: (HYDROPHILIC ACRYLIC)o ‘Hydrogel’ refers to a coherent 3 D polymeric network that can imbibe huge

quantities of water without dissolution.o These are based on poly 2-hydroxyethyl methacrylate (or pHEMA)

with 38% water content.o Rigid and brittle in dry state, become soft & pliable on hydrationo Resistant to biodegradation and spontaneous oxidation &

can withstand sterilization by chemical and thermal methods.o Must be kept hydrated until implantation because of their water content.o Refractive index-1.47 and specific gravity-1.19

Advantages:

Hydrophilic, less harmful to corneal endothelium Autoclavable , less expensive than silicone lens Less inflammation and cellular precipitation

Single piece: no irregularities at optic-haptic junction Fold and unfold faster than hydrophobic acrylic lenses More controllable than silicone lenses

Drawbacks:

• Extreme flexibility and low tensile strength • High rate of decentration• Lack of adhesive property to the capsular sac• Decreased resistance to capsular contraction (dislocation and C

deformity)• Can’t be used for sulcus or scleral fixation

Flexible acrylic lenses: (HYDROPHOBIC ACRYLIC)

Formed from monomers that are esters of acrylic acid with phenyl ethyl side group substitution• Unique mechanical (foldablity, strength) features• Optical (high refractive index) properties without compromising the biocompatibility,

chemical & physical stability • They possess a temperature dependent viscoelasticity, being softer at body temperature

than at room temperature. Eg. Acrysof (Alcon) And sensar (AMO)

Advantages:

High refractive index (1.55) Thinner lens optic Gentle and controlled unfolding Decreased endothelial cell damage Decreased YAG induced damage PCO rates are less

Drawbacks:

Stickier, tends to adhere to surgical instruments and posterior capsule: “tackiness”

(hence to be rinsed in warm BSS before insertion) Susceptible to mechanical damage by forceps or folder Little clinical experience with undemonstrated

biocompatibility. High surgical skill required

SMART LENS:

Uses thermodynamic hydrophobic acrylic material that is packaged as a solid rod 30mm long and 72mm wide

Developed by Medennium Inc. Rod is transformed at body temperature into soft gel Full sized biconvex material that completely fills the capsular bag

Advantages of foldable lenses:

Small size of incision: Maintains integrity of wound constructed for phacoemulsification

Earlier visual and physical rehabilitationLesser post op astigmatism

(Largest incisions are associated with 6mm acrylic and 3-piece silicone) Cellular response:

Lesser cellular adhesion Lesser endothelial cell lossSoft cushioning effect on uveal tissues results in lesser pigment dispersion, inflammation, iris chaffing & atrophy.

Weight:Low specific gravity hence lighterBeneficial in compromised zonular support

Optical quality and visual function:No finishing or polishing required after manufacture and as such residual chemicals are not presentOptical quality is good

Laser effects:Silicone IOLs have a low threshold for laser damage than PMMA lenses Hydrogel and acrylic lenses are less damaged than PMMA (Acrylic has a discrete locus of damage while other lenses exhibit a collateral damage)

Lens epithelial migration:Lesser migration, lesser PCO esp.with Acrylic

Disadvantages of foldable lenses:

Implantation damage:Due to soft and pliable natureDegradation from stresses of folding and unfolding.Acrylic lenses are more resistant and maintain optical quality

Discolouration: Original silicone lenses had an opalescence (capsulotomy difficult)

There are reports of lens discolouration after use of fluorescein. Glistenings and vacuoles:

Related to denaturation associated with heating and autoclaving Biocompatibility: Not fully known esp in paediatric cases, requires further study

MULTIFOCAL INTRAOCULAR LENSES:

Following cataract surgery, reading glasses are required for near work. To address this issue multifocal IOLs that provide refractive correction for near and distance are now available.

This concept is termed “PRELEX” or presbyopic lens exchange which describes the use of Array Multifocal IOL for refractive surgery (hyperopia and presbyopia) CNS adaptation is required to get adjusted to these IOLs These lenses use the principle of ‘simultaneous vision’ in which different areas of the IOL are designed with different focal plane, one portion of it is capable of focusing distant objects & one portion for near objects. If the distance portion is in focus on the retina there will be a ghost near focus and vice versaThey produce images by DIFFRACTIVE or REFRACTIVE optics

Disadvantages:

Loss of contrast sensitivity Loss of best corrected visual acuity Glare and haloes Requires patient counseling Requires very accurate biometry and IOL calculation

Inappropriate in patients with astigmatism Adaptation takes 6 months to 1 year NdYAG capsulotomy for PCO is difficult Not useful in low myopes, tend to have good near vision without spectacles

preoperatively.

Exclusion criteria:

o Monofocal lens in the other eye as adaptation is difficult o Unilateral cataract in youngo High ametropia as it is difficult to calculate accurate IOL powero Irregular astigmatism or high degrees of regular astigmatismo Low tolerance to glare and brightnesso Patients requiring laser therapy in future(DM, ARMD, risk of RD) as multifocal

may interfere with focusing laser beamo Behaviour disturbance, worrying , demanding, and impatient personality as it

needs a longer adaptation time.

Surgical considerations:

Precise emmetropic IOL power calculation is needed using immersion biometry or IOL master. 3rd generation formulae like SRK-T, Holladay, and Hoffer Q are recommended.

Each surgeon should have personalized “A’’constant Uncomplicated surgery with sub 3mm temporal clear corneal incision (minimize

astigmatism), in the bag placement of IOL with good centration by good rhexis overlap of 0.5mm over optic.

Good cortical clean up is important Adjunctive treatment of corneal astigmatism using limbal relaxing incisions Pupil diameter should be larger than 2.5mm so that atleast 2 refractive zones are

exposed. Postoperatively patient counselling and encouragement to adapt to the simultaneous

vision.

Types of multifocal IOLs:

Refractive optics multifocal IOLs:

These lenses have concentric rings of different powersTwo zone type:

Central near vision segment surrounded by a distance vision segment. When pupil constricts during near focus, central 2mm is used and when pupil dilates

during distance viewing peripheral segment is exposed. Disadvantageous in bright light when pupil constricts and blocks the distant segment.

Annulus type: Central portion of optic contains distance vision refraction and there is a near vision ring outside it, which in turn is surrounded by another distance vision ring. Eg. Array & Rezoom design (5 zone multifocal IOLs)

Diffractive optics multifocal IOLs:

Both the near & distance correction is put in each of the concentric rings. The lens design produces 2 diffractive orders in which the incoming waves of light will be in phase resulting in discrete optical foci of equal intensity.

Even if lens is decentered or pupil eccentric, the portion of the lens within the pupil will supply power for distance and near vision.

Eg. Technis IOL(AMO) and ReSTOR Lens (Alcon) The lens design produces 2 diffractive orders in which the incoming waves of light will be

in phase resulting in discrete optical foci of equal intensity

ACCOMODATIVE INTRAOCULAR LENSES:

These lenses were based on the proposal that replacement of crystalline lens with a lens that responds to ciliary body contraction should restore accomodative function.

AT45 CRYSTALENS: Modified silicone plate haptic lens made of solid silicone ‘biosil’ Lens has a hinge at the junction of haptic and optic to facilitate forward movement of the optic , and T shaped polyamide haptics at the end of the plates. Contraction of ciliary body during accomodation, increases vitreous cavity pressure and a decrease in anterior chamber pressure tends to push the IOL optic anteriorly

TETRAFLEX IOL: It is similar with a single optic designed to vault anteriorly in the accomodated state.

1CU INTRAOCULAR LENS: One-piece 3D, foldable acrylic lenses with 5.5mm optic. It fills the bag in 3 dimensions which allows the capsular bag to assume its pre-operative shape Modified haptics allow anterior movement of the lens optic upon contraction of ciliary muscle VISIOGEN DUAL OPTIC FOLDABLE SILICONE accomodating IOL – An innovative design that depends on the dynamic separation of 2 optics to create a variable accomodative effect.

FLUIDVISION LENS : It acts by moving fluid from the periphery of the lens to the central actuator under the anterior surface of the IOL.

NULENS: It is made of a flexible material contained between 2 rigid plates. The anterior plate has a central aperture through which the flexible material bulges during accomodation and increases the power of the lens

Advantages of accomodating IOL Produces a single image consistent with normal vision, meaning patients do not need to neuroadapt to viewing multiple images. Patients also do not need to tolerate or adjust to high levels of halos and glare often associated with multifocal IOLs.

IMPLANTS THAT CORRECT THE OPTICAL ABERRATIONS OF THE EYE: (ASPHERIC IOLS) Most of the modern IOLs have an aspheric design to prevent aberrations & form a clear image on the retina bringing all light to a precise focal point on the retina The spherical aberrations of an individual eye are calculated using wavefront aberrometer

Curvatures on either the front or back surface of the lens implant are manufactured so as to correct these aberrations.

The lens implant could be optically “made to measure” for each individual eye. A knowledge of the average aberrations of the eye at a given age could be used to produce an “off the peg” aberration correcting lens implant. Such a lens is commercially available now.

PHAKIC IOLs: (duophakia/artiphakia)

Increased interest in refractive surgery and appreciation of significant disabilities of high refractive errors (myopic and hypermetropic) have been recognized as therapeutic options for the correction of refractive errors without concomitant cataract. Satisfactorily correct high myopia(-12 to -14D) and hyperopia(+5 to +6D) Lens can be exchanged in the event that the patient is overcorrected or undercorrected. It allows the crystalline lens to retain its function and possibly protect against the vitreoretinal side effects of clear lens extraction( Retinal detachment) Acquisition of surgical skill is easier for those experienced in cataract surgery. Overcomes the limitations of corneal refractive surgeries like

Residual errorUnstable cornea(keratectasia)Tear film abnormalitiesPoor contrast sensitivityLimitation in night vision

Problems related to any intraocular surgery is present IOL power calculation depends on

Diopteric power of cornea at its apexDepth of ACRefraction

Overall diameter of the lens is chosen by adding 0.5-1.0mm to the horizontal corneal diameter (white to white distance).

Criteria for implantation: High stable refractive errors beyond -12D or +4D Age >21 and <50 yrs AC depth atleast 3.2mm IOP between 8 and 21mmHg Normal pupil function Central corneal endothelial count atleast 2,250 cells/mm² Ammetropia not correctable with excimer laser surgery(CCT <480µ, Residual bed

<270µ, KeratoConus- forme fruste) Unsatisfactory vision with /intolerance of contact lens or spectacles No ocular pathology( corneal disorders, cataract, uveitis, glaucoma, maculopathy etc) No previous ocular surgery

Complications : Endothelial cell loss Pupil ovalisation Cataract Uveitis and pigment dispersion Pupillary block glaucoma. (resistance in the retropupillary space prevents the

physiological flow of aqueous through the pupil, pushing forward the iris and closing the iridocorneal angle)

Contraindications:o Glaucoma, pigment dispersion syndromes, PXFo Presence of lens opacities/nuclear sclerosiso Uveitiso Rubeosis iridiso Nanophthalmoso Corneal dystrophy and keratitis

1 or 2 Prophylactic LI or surgical PI must be done in all cases away from the haptic placement

3 Design types: Angle supported Iris fixated Posterior chamber phakic IOLs

Several models that have been approved by the FDA are:

Visian implantable contact lens (ICL, STAAR surgical) Artisan lens (ophtec B.V) Verisyse Iris claw PhIOL (AMO

TORIC IOLs: This is an option to treat preexisting corneal regular astigmatism at the time of cataract surgery.

Useful in cases where Limbal relaxing incisions are contraindicated like keratoconus, peripheral corneal pathology, autoimmune or rheumatoid disease etc.

Keratometry must be done to determine magnitude and axis of corneal cylinder Surgeon must know his or her incision impacts on corneal curvature Mydriasis should be good in order to visualize the toric implant axis marks on the

periphery of the lens for correct positioning. The IOL has a plate haptic design with correction cylinder added along the long axis

of IOL Axis is marked along the surface of IOL The surgeon has to mark the eye pre/intraoperatively and carefully rotate the lens to

align with the IOL marks. For toric design to be stable the lens should not rotate within the eye after

implantation

Eg. STAAR toric IOL (silicon) & Alcon Acrysof (acrylic) toric IOL

Disadvantages: Patient cannot be corrected for presbyopia Lenses may rotate They do not correct the problem at source Residual astigmatism may be present

LASER ADUSTABLE IOLs: Power of IOL could be adjusted postoperatively with laser. Silicone IOL is embedded with photosensitive macromeres which polymerise after being hit by low energy laser(UV light-365nm) Polymerization at the centre :leads to an increase in IOL power (hyperopia), while polymerization at the periphery leads to decrease in IOL power (myopia). Currently existing lens is a 3 piece silicone lens with modified c shaped PMMA haptics known as ‘ Calhoun light adjustable lens’. Range of adjustment is 4D (-2 to +2D)

The LAL contains photosensitive silicone molecules that enable precise and noninvasive

postoperative adjustment of refractive power using ultraviolet light. The LAL formulation consists

of four basic components: silicone matrix polymer, photoreactive macromer, photoinitiator, and

UV absorber. The LAL material design has been described previously, and is based upon the

principles of photochemistry and diffusion whereby photoreactive macromers dispersed within the

cross-linked silicone lens matrix are photopolymerized upon exposure to UV light (365 nm) of a

select spatial intensity profile. Upon irradiation, the photoinitiator initiates polymerization of the

macromer photoreactive groups to form an interpenetrating polymer within the lens matrix.

Diffusion of the remaining unirradiated macromer into the irradiated areas induces a change in

shape or refractive index, or both, to produce a predictable power change.

Silicone was selected as the lens matrix because of its optical clarity, ability to be folded through

a small incision during insertion, high diffusibility (ie, a low glass transition temperature), and

history of safe use in IOLs. In addition to the UV-absorbing properties of the LAL, the posterior

surface of each lens is molded with a 50-μm-thick higher-UV-absorbing layer to impart the

pseudophakic patient with additional UV protection for the retina during the irradiation treatment

procedure. By controlling the irradiation dosage (ie, beam intensity and duration), spatial intensity

profile, and target area, physical changes in the radius of curvature of the lens surface are

achieved, thus modifying the refractive power of an implanted LAL to add or subtract spherical

power, eliminate astigmatic error, or correct higher-order aberrations. Once the appropriate power

adjustment is achieved, the entire lens is irradiated in a second irradiation procedure, referred to

as “lock-in.” By irradiating the entire lens, any remaining unreacted macromer is polymerized and

macromer diffusion is prevented; thus, no change in lens power results.

Clinically, changes in LAL power are accomplished using a digital light delivery (DLD) system

engineered by Carl Zeiss-Meditec (Jena, Germany). The DLD) consists of a UV light source,

projection optics, and control interface built around a standard slit lamp. The light source

employed is a mercury (Hg) arc lamp delivered to the projection optics through a liquid-filled light

guide. The light source includes a narrow bandpass interference filter producing a narrow-

wavelength beam with a center wavelength of 365 nm. The DLD contains a digital mirror device,

which is a pixelated, micromechanical spatial light modulator formed monolithically on a silicon

substrate. The advantage of the digital mirror device is the ability to easily define a specific high-

resolution spatial intensity profile, program this into the digital mirror device, and then irradiate the

LAL.