1. What is a Contact Lens? Artificial device whose front surface substitutes the antr. surface of the cornea Used for correction of: 1. Refractive error 2. Irregularities on front surface of cornea

2. Contact Lens Specifications Diameter 1. Overall diameter (OD) 2. Optic zone diameter (OZ) 3. Curves Base curve (BC) or central postr. curve (CPC) Peripheral curves 1.intermediate (IPC) 2.peripheral (PPC) Central antr. curve (CAC) or front curve (FC) Peripheral antr. curve (PAC) Intermediate antr. curve (IAC) 4. Edge Union of the Peri.Postr.C & Peri.Antr.C of the lens Power Central anterior curve determines the power of the lens Measured in terms of posterior vertex power in diopters 5. Thickness Measured in the centre of the lens Varies depending upon the postr. vertex power of the lens Tint Color of the lens 6. Types of Contact Lenses Hard Lens Rigid Gas Permeable Lens Soft Lens 7. Hard Lens From PMMA (polymethylmethacrylate) High optical quality, stability, light weight, nontoxic, durable & cheap Diameter of 8.5-10 mm Disadvantages: 1. restricting the tolerance 2. corneal abrasions 3. stable tear film 8. Rigid Gas Permeable Lens Material permeable to oxygen Hard, but called as semisoft lenses Manufactured from: 1. Copolymer of PMMA 2. Silicone containing vinyl monomer 3. Cellulose acetate butyrate 9. Soft Lens HEMA (hydroxymethymethacrylate) About 1-2 mm larger than corneal diameter Advantages: 1. comfortable 2. well tolerated 10. 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 11. Soft Lens Types: Disposable or Non-Disposable Clear or Colored Spherical or Toric Extended Wear Multifocal 12. 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 13. 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 14. Disposable Soft Lens Daily, two-weekly or monthly replacement Very simple cleaning (no cleaning for daily) Latest designs and materials Very popular 15. 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 16. Colored Contact Lens 17. Extended Wear Contact Lens New technology Made from silicone material which transmits oxygen well Can wear for up to thirty days without removing 18. MultiFocal Contact Lenses Can have dual focus lenses New technology More expensive Available as disposable lenses 19. Indications Optical Therapeutic Preventive Diagnostic Operative Cosmetic Occupational 20. Optical Indications Anisometropia Unilateral Aphakia High Myopia Keratoconus Irregular Astigmatism 21. Advantage Over Specs Can correct irregular astigmatism Normal field of vision No aberrations Binocular vision in high anisometropia No condensation of rain or fog Cosmetically more acceptable 22. Therapeutic Indications Diseases of Cornea Diseases of Iris Glaucoma Amblyopia Bandage Soft Contact Lenses 23. Preventive Indications Prevention of symblepharon and restoration of fornices in chemical burns Exposure keratitis Trichiasis 24. Diagnostic Indications Gonioscopy Electroretinography Examination of fundus in case of irregular corneal astigmatism Fundus photography Goldmanns 3 mirror examination 25. Operative Indications Goniotomy operation for congenital glaucoma Vitrectomy Endocular photocoagulation 26. Cosmetic Indications Unsightly corneal scars Ptosis Cosmetic scleral lenses in phthisis bulbi 27. Occupational Indications Sportsmen Pilots Actors 28. 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 29. Hygeine 30. Complications 31. The End