1. Contact lens

2. Definition Thin plastic wafer which is designed to rest over the cornea or sclera to correct refractive errors Leonardo de Vinci - Father of contact lens

3. Types 1.Hard contact lens 2.Semi soft contact lens 3.Soft contact lens

4. Hard contact lens 1.Flexibility – Very minimal 2.Material - PMMA ( Poly methyl metha acryl ate) 3.Wearing schedule : 8 – 10 hours a day 4.Ideal for keratoconus patients 5.High Astigmatism

5. Semi 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

6. Soft contact lens 1.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)

7. Indications 1.All refractive errors 2.Anisometropia 3.Anisokonia 4.Unilateral aphakia 5.Keratoconus 6.Corneal opacity 7.Aniridia 8.Nystagmus with refractive error

8. Contra Indications 1. Any inflammatory conditions in the eye 2. Dry eye 3. Allergic 4. Pregnancy women 5. Uncontrolled Diabetes

9. Advantages 1. Field of vision is high 2. Cosmetically good 3. No Diplopia 4. No peripheral aberrations 5. No chromatic aberrations 6. Sharp vision

10. Disadvantages * 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

11. Fitting 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.

12. Fitting of semi soft & Hard contact lens 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

13. Instructions to contact lens wearers 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