contact lens

Contact lensContact lens

DefinitionDefinition

• Thin plastic wafer which is designed to rest over the cornea or sclera to correct refractive errors

• Leonardo de Vinci - Father of contact lens

TypesTypes

1. Hard contact lens

2. Semi soft contact lens

3. Soft contact lens

Hard contact lensHard contact lens

1. Flexibility – Very minimal2. Material - PMMA ( Poly methyl metha acryl

ate)3. Wearing schedule : 8 – 10 hours a day4. Ideal for keratoconus patients5. High Astigmatism

Semi soft contact lensSemi soft contact lens

1. Flexibility (Moderate -less than soft)

2. Material :Cellulose acetyl butyrate(CAB) Fluoro silicon

3. Wearing schedule : 8-10 hours a day

Soft contact lensSoft contact lens1. Good flexibility

2. HEMA ( Hydroxyl ethyl metha acryl ate)

3. Wearing schedule : 10-12 hours a day

4. Corrects Astigmatism < 1.25 diopter only

Types

(a)Cosmetic - Regular & colour lenses

(b)Prosthetic - Corneal opacity,Leucoma cases

(C)Therapeutic - Treatment purpose (Bullous

Keratopathy)

d)Toric - For Astigmatism ( Below Sph -6

Cyl-3.25)

IndicationsIndications

1. All refractive errors

2. Anisometropia

3. Anisokonia

4. Unilateral aphakia

5. Keratoconus

6. Corneal opacity

7. Aniridia

8. Nystagmus with refractive error

Contra IndicationsContra Indications

1. Any inflammatory conditions in the eye

2. Dry eye

3. Allergic

4. Pregnancy women

5. Uncontrolled Diabetes

AdvantagesAdvantages

1. Field of vision is high

2. Cosmetically good

3. No Diplopia

4. No peripheral aberrations

5. No chromatic aberrations

6. Sharp vision

DisadvantagesDisadvantages

* Lack of dextrity in old patients• Foreign body sensation• Lens spoilage( due to loss breakage

dislodgement etc..) leading to high recurrent expenditure.• Corneal complication – like erosions,

ulceration, edema, vascularisation etc.. may be troublesome* Light spectacles are required for reading, and

for distance vision

Fitting TechniquesFitting Techniques

• For soft contact lens

a) The diameter of soft contact lens should be 1.5mm more than the limbus .

b) The base curve of soft contact lens should be

1.25 mm flatter then the flattest keratometric value .

c) It should have equal coverage in all meridians and shoud have ideal movement of 1mm atleast .

Fitting of semi soft & Hard contact Fitting of semi soft & Hard contact lenslens

• Usually the diameter of semi soft & hard contact lens should be lesser then the cornea

• The fitting of semi soft & hard contact lens is entirely based on keratomery value

• But as for the selection of first trial lens,the base curve must fall on the mean keratometric value

• Fluorescein pattern can be studied for fitting evaluation

Instructions to contact lens Instructions to contact lens wearerswearers

a)Always wash your hands with soap before using contact lens

b)Remove your contact lenses while sleeping.

c)Apply cosmetics after insertion of contact lens

d)Clean your lenses regularly with the prescribed solution

e) Consult your ophthalmologist When you feel any problem with your eyes