Download - Contact Lenses

Transcript
Page 1: Contact Lenses

CONTACT

LENSES By

Sridevi Rajeeve2008 Batch

Page 2: Contact Lenses

What is a Contact Lens ?

Artificial device whose front surface substitutes the anterior surface of cornea.

Used for correction of: 1. Refractive errors 2. Irregularities on anterior surface of cornea

Page 3: Contact Lenses

Contact Lens pecifications

Diameter 1. Overall diameter [OD] - x mm 2. Optical zone diameter (OZ)

Page 4: Contact Lenses

Curves Base curve (BC) or central posterior curve (CPC) Peripheral curves : 1. intermediate (IPC) 2. peripheral (PPC) Central anterior curve (CAC) or front curve (FC) Peripheral anterior curve (PAC) Intermediate anterior curve (IAC)

Tear reservoir+ ski for lensmovements

Power

- Only in high power minus and plus lenses

Page 5: Contact Lenses

Edge Polished and blended union of the Peripheral

posterior curve & Peripheral Anterior curve of the lens

Power Central anterior curve curvature determines the

power of the lens Measured in terms of posterior vertex power. Unit: Diopters [D]

Page 6: Contact Lenses

Thickness Measured in the centre of the lens Varies depending upon the posterior

vertex power of the lens

Tint Color of the lens

Page 7: Contact Lenses

TYPES OF CONTACT LENSES

Depending upon nature of material used; Hard Lens Rigid Gas Permeable Lens Soft Lens

Page 8: Contact Lenses

HARD LENS

From PMMA (polymethylmethacrylate) High optical quality, stability, light weight,

nontoxic, durable & cheap Diameter of 8.5-10 mm Disadvantages: 1. Restricts the tolerance -

O2 impermeable

2. Corneal Abrasions 3. Stable tear film

Page 9: Contact Lenses

RIGID GAS PERMEABLE Lens

Material permeable to oxygen Popularized as Semi-Soft lenses Manufactured from a co-polymer of:

1. PMMA 2. Silicone containing vinyl

monomer 3. Cellulose acetate butyrate

Page 10: Contact Lenses

SOFT LENS

Material: HEMA (hydroxymethymethacrylate)

About 1-2 mm larger than corneal diameter

Advantages: 1. Comfortable

2. Well-tolerated

Page 11: Contact Lenses

Soft Lens Disadvantages: 1. Wettability 2. Proteinaceous deposits 3. Can get torn 4. Limited life 5. Inferior optical quality 6. Increased risk of corneal infections 7. Cannot correct astigmatism > 2D

Page 12: Contact Lenses

Soft Lens Types: ▪ Disposable or Non-Disposable ▪ Clear or Colored ▪ Spherical or Toric ▪ Extended Wear ▪ Multifocal

Page 13: Contact Lenses

Spherical Soft Lens A spherical contact lens is one in

which both the inner and outer optical surfaces are portions of a sphere

Corrects both short- and long- sightedness

Cheapest & most comfortable Easy to get in a disposable form

Page 14: Contact Lenses

Toric Soft Lens A toric lens is one in which either or

both of the optical surfaces have the effect of a cylindrical lens, usually in combination with the effect of a spherical lens

Corrects astigmatism Lens is specially weighted to conform

to irregular cornea More expensive than spherical Some are available in disposable

Page 15: Contact Lenses

Disposable Soft Lens Daily, two-weekly or monthly

replacement Very simple cleaning (no cleaning for

daily) Latest designs and materials Very popular

Page 16: Contact Lenses

Colored Contact Lens Handling tint

Useful when inserting or removing lens

Enhancing tint Makes light coloured eyes more vivid

Opaque tint Can change colour of eyes

Page 17: Contact Lenses

Colored Contact Lens

Page 18: Contact Lenses

Extended Wear Contacts Lens

New technology Made from silicone material which

transmits oxygen well Can wear for up to thirty days

without removing.

Page 19: Contact Lenses

MultiFocal Contacts Lenses Can have dual focus lenses New technology → More expensive Available as disposable lenses

Page 20: Contact Lenses

Indications for use Optical Therapeutic Preventive Diagnostic Operative Cosmetic Occupational

Page 21: Contact Lenses

Optical Indications Anisometropia Unilateral

Aphakia High Myopia Keratoconus Irregular

Astigmatism

Page 22: Contact Lenses

Advantage over spectacles

Can correct irregular corneal astigmatism

Normal field of vision provision No aberrations – peripheral /

prismatic Binocular vision in high

anisometropia No condensation of rain or fog Cosmetically more acceptable

Page 23: Contact Lenses

Therapeutic Indications Indications

Diseases of Cornea – Non-healing corneal ulcers, filamentary keratitis and recurrent corneal erosion syndrome.

Diseases of Iris – Aniridia, coloboma and albinism (avoid glare)

Glaucoma (vehicle for drug delivery) Amblyopia (Opaque lens - Occlusion) Bandage Soft Contact Lenses – Post-keratoplasty and microcornealperforation

Page 24: Contact Lenses

Preventive Indications Prevention of symblepharon and

restoration of fornices in chemical burns

Exposure keratitis Trichiasis

Page 25: Contact Lenses

Diagnostic Indications Gonioscopy Electroretinography Examination of fundus in case of

irregular corneal astigmatism Fundus photography Goldmann’s 3 mirror examination

Page 26: Contact Lenses

Operative Indications Goniotomy operation for congenital

glaucoma Vitrectomy Endocular photocoagulation

Page 27: Contact Lenses

Cosmetic Indications Unsightly corneal scars (Coloured

lenses) Ptosis (Haptic lenses) Cosmetic scleral lenses in phthisis

bulbi

Page 28: Contact Lenses

Occupational Indications Indications

Sportsmen Pilots Actors

Page 30: Contact Lenses

ContraIndications Mental Incompetence/Poor Motivation Chronic Dacryocystitis Chronic Blepharitis and Recurrent Styes Chronic Conjunctivitis Dry-Eye Syndrome Corneal Dystrophies and Degenerations Recurrent diseases like Episcleritis,

Scleritis & Iridocyclitis

Page 31: Contact Lenses

THANK YOU!