Cataract lecture

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CATARACT by Ogunlaja Oluwadamilola

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Good one

Transcript of Cataract lecture

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DEFINITION A cataract is a clouding of the

lens in the eye that affects vision. Most cataracts are related to aging.A cataract can occur in either or both eyes. It cannot spread from one eye to the other

In a normal eye, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain.

The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred

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CAUSES The lens is made of mostly water and protein. The protein is

arranged in a precise way that keeps the lens clear and lets light pass through it.

But as we age, some of the protein may clump together and start to cloud a small area of the lens. Over time, the cataract may grow larger and cloud more of the lens, making it harder to see,this prevents light from passing clearly through the lens, causing some loss of vision. Since new lens cells form on the outside of the lens, all the older cells are compacted into the center of the lens resulting in the cataract

There are several causes of cataract, such as smoking and diabetes. Or, it may be that the protein in the lens just changes from the wear and tear it takes over the years

Blunt trauma causes swelling, thickening and whitening of the lens fibers. While the swelling normally resolves with time, the white color may remain. In severe blunt trauma, or injuries which penetrate the eye, the capsule in which the lens sits can be damaged

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Some drugs, such as corticosteroids, can induce cataract development

The skin and the lens have the same embryological origin and can be affected by similar diseases. Those with Atopic dermatitis and Eczema will occasionally develop shield ulcers cataracts. Ichthyosis is an autosomal recessive disorder associated with cuneiform cataracts and nuclear sclerosis

There is a strong genetic component in the development of cataracts, most commonly through mechanisms that protect and maintain the lens. The presence of cataracts in childhood or early life can occasionally be due to a particular syndrome.

Examples of Chromosome abnormalities associated with cataracts include: 1q21.1 deletion syndrome, Cri-du-chat syndrome, Down syndrome, Patau's syndrome, Trisomy 18 (Edward's syndrome) and Turner's syndrome

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CLASSIFICATION

Cataracts may be partial or complete, stationary or progressive, or hard or soft. The main types of age-related cataracts are nuclear sclerosis, cortical, and posterior subcapsular

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CLASSIFICATION BY ETIOLOGY1. Age-related cataract:

(a) Cortical Senile Cataract ◦ Immature senile cataract (IMSC): partially opaque lens, disc

view hazy ◦Mature senile cataract (MSC): Completely opaque lens, no

disc view ◦Hypermature senile cataract (HMSC): Liquefied cortical

matter: Morgagnian cataract ◦Senile Nuclear Cataract :

Cataracta brunescens cataracta nigra cataracta rubra Congenital cataract:

◦ Sutural cataract ◦ Lamellar cataract ◦ Zonular cataract ◦ Total cataract ◦ Secondary cataract

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2.Drug-induced cataract (e.g. corticosteroids)

3. Traumatic cataract ◦ Blunt trauma (capsule usually intact) ◦ Penetrating trauma (capsular rupture & leakage of lens material—calls for

an emergency surgery for extraction of lens and leaked material to minimize further damage)

CLASSIFICATION BY LOCATION OF OPACITY WITHIN LENS STRUCTURE)

◦ Anterior cortical cataract ◦ Anterior polar cataract ◦ Anterior subcapsular cataract

4. Nuclear cataract—Grading correlates with hardness & difficulty of surgical removal ◦ 1: Grey ◦ 2: Yellow ◦ 3: Amber ◦ 4: Brown/Black (Note: "black cataract" translated in some languages (like

Hindi) refers to glaucoma, not the color of the lens nucleus) ◦ Posterior cortical cataract ◦ Posterior polar cataract (importance lies in higher risk of complication—

posterior capsular tears during surgery) ◦ Posterior subcapsular cataract (PSC) (clinically common)

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SYMPTOMSSigns and symptoms vary depending on the type of cataract, though there is considerable overlapClouded, blurred or dim visionIncreasing difficulty with vision at nightSensitivity to light and glareSeeing "halos" around lightsFrequent changes in eyeglass or contact lens

prescriptionFading or yellowing of colorsDouble vision in a single eye(superimposed vision)Progressive nearsightedness in older people often

called "second sight" because they may no longer need reading glasses.

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DIAGNOSISVisual acuity test. This eye chart test measures

how well you see at various distances.Dilated eye exam(retinal examination). Drops

are placed in your eyes to widen, or dilate, the pupils. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.

Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.).

Using a slit lamp or a special device called an ophthalmoscope, your eye doctor can examine your lens for signs of a cataract.

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TREATMENT1. N-acetylcarnosine have been investigated as a medical treatment for cataracts. The drops are believed to work by reducing oxidation and glycation damage in the lens, particularly reducing crystalline crosslinking.The main treatment for cataract is surgery. The surgical methods are:1. Phacoemulsification, or phaco. A small incision is made on the side

of the cornea, the clear, dome-shaped surface that covers the front of the eye. Your doctor inserts a tiny probe into the eye. This device emits ultrasound waves that soften and break up the lens so that it can be removed by suction.

2. Extracapsular surgery. Your doctor makes a longer incision on the side of the cornea and removes the cloudy core of the lens in one piece. The rest of the lens is removed by suction

3. Femtosecond laser has been used during cataract surgery. This technique known as femtosecond laser technology and originally used to cut accurate and predictable flaps in LASIK surgery, has been introduced to cataract surgery. The incision at the junction of the sclera and cornea and the hole in capsule during capsulorhexis, traditionally made with a handheld blade, needle and forceps are dependent on skill and experience of the surgeon. Sophisticated 3-D image of the eyes can be used to guide lasers to make these incisions

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4. Manual small incision cataract surgery (MSICS): This technique is an evolution of ECCE (see below) where the entire lens is expressed out of the eye through a self-sealing scleral tunnel wound. An appropriately constructed scleral tunnel is watertight and does not require suturing. The "small" in the title refers to the wound being relatively smaller than an ECCE, although it is still markedly larger than a phaco wound. Head to head trials of MSICS vs phaco in dense cataracts have found no different in outcomes, but shorter operating time and significantly lower costs with MSICS. 5. Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogen. In this technique, the cataract is extracted through use of a cryoextractor — a cryoprobe whose refrigerated tip adheres to and freezes tissue of the lens, permitting its removal. Although it is now used primarily for the removal of subluxated lenses, it was the favored form of cataract extraction from the late 1960s to the early 1980s

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PHACOEMULSIFICATIONPhacoemulsification (Phaco) is the most common

technique used by developed countries. It involves the use of a machine with an ultrasonic handpiece equipped with a titanium or steel tip. The tip vibrates at ultrasonic frequency (40,000 Hz) and the lens material is emulsified. A second fine instrument (sometimes called a "cracker" or "chopper") may be used from a side port to facilitate cracking or chopping of the nucleus into smaller pieces. Fragmentation into smaller pieces makes emulsification easier, as well as the aspiration of cortical material (soft part of the lens around the nucleus). After phacoemulsification of the lens nucleus and cortical material is completed, a dual irrigation-aspiration (I-A) probe or a bimanual I-A system is used to aspirate out the remaining peripheral cortical material.

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OPERATION PROCEDURES The surgical procedure in phacoemulsification for removal of cataract involves a number

of steps. The steps may be described as follows: Anaesthesia Exposure of the eyeball using a lid speculum, Entry into the eye through a minimal incision (corneal or scleral) Viscoelastic injection to stabilize the anterior chamber and to help maintain the eye

pressurization Capsulorhexis Hydrodissection pie Hydro-delineation Ultrasonic destruction or emulsification of the cataract after nuclear cracking or chopping

(if needed), cortical aspiration of the remanescent lens, capsular polishing (if needed) Implantation of the, usually foldable, intra-ocular lens (IOL) Viscoelastic removal Wound sealing / hydration (if needed). The pupil is dilated using drops (if the Intraocular lens is to be placed behind the iris) to

help better visualise the cataract. Pupil-constricting drops are reserved for secondary implantation of the IOL in front of the iris (if the cataract has already been removed without primary IOL implantation).

Anesthesia may be placed topically (eyedrops) or via injection next to (peribulbar) or behind (retrobulbar) the eye. Oral or intravenous sedation may also be used to reduce anxiety

The eyelids and surrounding skin will be swabbed with disinfectant. The face is covered with a cloth or sheet, with an opening for the operative eye. The eyelid is held open with a speculum to minimize blinking during surgery.

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Pain is usually minimal in properly anesthetised eyes, though a pressure sensation and discomfort from the bright operating microscope light is common. The ocular surface is kept moist using sterile saline eyedrops or methylcellulose viscoelastic.

The incision into the lens of the eye is performed at or near where the cornea and sclera meet (limbus = corneoscleral junction). Advantages of the smaller incision include use of few or no stitches and shortened recovery time.

A capsulotomy (rarely known as cystotomy) is a procedure to open a portion of the lens capsule, using an instrument called a cystotome. An anterior capsulotomy refers to the opening of the front portion of the lens capsule, whereas a posterior capsulotomy refers to the opening of the back portion of the lens capsule. In phacoemulsification, the surgeon performs an anterior continuous curvilinear capsulorhexis, to create a round and smooth opening through which the lens nucleus can be emulsified and the intraocular lens implant inserted.

Antibiotics may be administered pre-operatively, intra-operatively, and/or post-operatively. Frequently a topical corticosteroid is used in combination with topical antibiotics postoperatively.

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Most cataract operations are performed under a local anaesthetic, allowing the patient to go home the same day. The use of an eye patch may be indicated, usually for about some hours.

Occasionally, a peripheral iridectomy may be performed to minimize the risk of pupillary block glaucoma. An opening through the iris can be fashioned manually (surgical iridectomy) or with a laser (called Nd-YAG laser iridotomy). The laser peripheral iridotomy may be performed either prior to or following cataract surgery.

An antibiotic/steroid combination eye drop is put and an eye shield may be applied on the operated eye, sometimes supplemented with an eye patch.

After the surgery, the patient is instructed to use anti-inflammatory and antibiotic eye drops for up to two weeks (depending on the inflammation status of the eye and some other variables). The eye will be mostly recovered within a week, and complete recovery should be expected in about a month.

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Intraocular lens implantation: After the removal of the cataract, an intraocular lens(IOL) is usually implanted into the eye, either through a small incision (1.8 mm to 2.8 mm) using a foldable IOL, or through an enlarged incision, using a PMMA (polymethylmethacrylate) lens. The foldable IOL, made of silicone or acrylic material of appropriate power is folded either using a holder/folder, or a proprietary insertion device provided along with the IOL. The lens implanted is inserted through the incision into the capsular bag within the posterior chamber (in-the-bag implantation).

Sometimes, a sulcus implantation (in front or on top of the capsular bag but behind the iris) may be required because of posterior capsular tears or because of zonulodialysis. Implantation of posterior chamber IOL (PCIOL) in patients below

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1 year of age is controversial due to rapid ocular growth at this age and the excessive amount of inflammation, which may be very difficult to control. Optical correction in these patients without intraocular lens (aphakic) is usually managed with either special contact lenses or glasses. Secondary implantation of IOL (placement of a lens implant as a second operation) may be considered later. New designs of multifocal intraocular lens are now available. These lenses allow focusing of rays from distant as well as near objects, working much like bifocal or trifocal eyeglasses.

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COMPLICATIONS1. PVD — Posterior vitreous detachment does not directly threaten

vision. Even so, it is of increasing interest because the interaction between the vitreous body and the retina might play a decisive role in the development of major pathologic vitreoretinal conditions. PVD may be more problematic with younger patients, since many patients older than 60 have already gone through PVD. PVD may be accompanied by peripheral light flashes and increasing numbers of floaters.

2. Posterior capsular tear may be a complication during cataract surgery. The rate of posterior capsular tear among skilled surgeons is around 2% to 5%. It refers to a rupture of the posterior capsule of the natural lens. Surgical management may involve anterior vitrectomy and, occasionally, alternative planning for implanting the intraocular lens, either in the ciliary sulcus, in the anterior chamber (in front of the iris), or, less commonly, sutured to the sclera.

3. Retinal detachment is an uncommon complication of cataract surgery, which may occur weeks, months, or even years later.

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4 Toxic Anterior Segment Syndrome or TASS is a non-infectious inflammatory condition that may occur following cataract surgery. It is usually treated with topical corticosteroids in high dosage and frequency.

5 Endophthalmitis is a serious infection of the intraocular tissues, usually following intraocular surgery, or penetrating trauma. There is some concern that the clear cornea incision might predispose to the increase of endophthalmitis but there is no conclusive study to corroborate this suspicion.

6 Some people can develop a posterior capsular opacification (PCO, also called an after-cataract). As a physiological change expected after cataract surgery, the posterior capsular cells undergo hyperplasia and cellular migration, showing up as a thickening, opacification and clouding of the posterior lens capsule which is left behind when the cataract was removed, for placement of the IOL). This may compromise visual acuity and the ophthalmologist can use a device to correct this situation. It can be safely and painlessly corrected using a laser device to make small holes in the posterior lens capsule of the crystalline. It usually is a quick outpatient procedure that uses a Nd-YAG laser(neodymium-yttrium-aluminum-garnet) to disrupt and clear the central portion of the opacified posterior lens capsule (posterior capsulotomy)..

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7 Glaucoma may occur and it may be very difficult to control. It is usually associated with inflammation, specially when little fragments or chunks of the nucleus get access to the vitreous cavity. Some experts recommend early intervention when this condition happens (posterior pars plana vitrectomy). Neovascular glaucoma may occur, specially in diabetic patients. In some patients, the intraocular pressure may remain so high that blindness may ensue.

8 Swelling or edema of the central part of the retina, called macula, resulting in macular edema, can occur a few days or weeks after surgery. Most such cases can be successfully treated

9 Other possible complications include: Swelling or edema of the cornea, sometimes associated with cloudy vision, which may be transient or permanent (pseudophakic bullous keratopathy). Displacement or dislocation of the intraocular lens implant may rarely occur. Unplanned high refractive error (either myopic or hypermetropic) may occur due to error in the ultrasonic ecobiometry (measure of the length and the required intra-ocular lens power). Cyanopsia, in which the patient sees everything tinted with blue, often occurs for a few days, weeks or months after removal of a cataract. Floaters commonly appear after surgery

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