Contact Lenses

download Contact Lenses

of 31

Embed Size (px)

description

Contact lenses - a summary

Transcript of Contact Lenses

  • 1. What is a Contact Lens ? Artificial device whose front surfacesubstitutes the anterior surface of cornea. Used for correction of:1. Refractive errors2. Irregularities on anterior surface ofcornea

2. Contact Lens pecifications Diameter1. Overall diameter [OD] - x mm2. Optical zone diameter (OZ) 3. 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 lensmovementsPower-Only in high power minus and plus lenses 4. Edge Polished and blended union of the Peripheralposterior curve & Peripheral Anterior curve of thelensPower Central anterior curve curvature determines thepower of the lens Measured in terms of posterior vertex power. Unit: Diopters [D] 5. Thickness Measured in the centre of the lens Varies depending upon the posterior vertexpower of the lensTint Color of the lens 6. TYPES OF CONTACT LENSESDepending upon nature of material used; 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. Restricts the tolerance -O2 impermeable2. Corneal Abrasions3. Stable tear film 8. RIGID GAS PERMEABLE Lens Material permeable to oxygen Popularized as Semi-Soft lenses Manufactured from a co-polymer of:1. PMMA2. Silicone containing vinyl monomer3. Cellulose acetate butyrate 9. SOFT LENS Material: HEMA(hydroxymethymethacrylate) About 1-2 mm larger than cornealdiameter Advantages: 1. Comfortable2. Well-tolerated 10. Soft Lens Disadvantages:1. Wettability2. Proteinaceous deposits3. Can get torn4. Limited life5. Inferior optical quality6. Increased risk of corneal infections7. 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 boththe inner and outer optical surfaces areportions 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 ofthe optical surfaces have the effect of acylindrical lens, usually in combination withthe effect of a spherical lens Corrects astigmatism Lens is specially weighted to conform toirregular 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 Contacts Lens New technology Made from silicone material which transmitsoxygen well Can wear for up to thirty days withoutremoving. 18. MultiFocal Contacts Lenses Can have dual focus lenses New technology More expensive Available as disposable lenses 19. Indications for use Optical Therapeutic Preventive Diagnostic Operative Cosmetic Occupational 20. Optical Indications Anisometropia Unilateral Aphakia High Myopia Keratoconus IrregularAstigmatism 21. Advantage overspectacles 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 22. Therapeutic IndicationsIndications Diseases of Cornea Non-healing corneal ulcers,filamentary keratitis and recurrent cornealerosion 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 23. Preventive Indications Prevention of symblepharon and restorationof fornices in chemical burns Exposure keratitis Trichiasis 24. Diagnostic Indications Gonioscopy Electroretinography Examination of fundus in case of irregularcorneal astigmatism Fundus photography Goldmanns 3 mirror examination 25. Operative Indications Goniotomy operation for congenitalglaucoma Vitrectomy Endocular photocoagulation 26. Cosmetic Indications Unsightly corneal scars (Coloured lenses) Ptosis (Haptic lenses) Cosmetic scleral lenses in phthisis bulbi 27. Occupational IndicationsIndications Sportsmen Pilots Actors 28. ComplicationsEyelidPtosisConjunctivaGiant papillary conjunctivitisSuperior limbic keratoconjunctivitisCorneaEpitheliumCorneal abrasionCorneal erosionContact lens acute red eye (CLARE)KeratitisCorneal ulcerCorneal stromaCorneal neovascularisationCorneal oedemaCorneal infiltratesCorneal endotheliumEndothelial polymegathism 29. 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 30. THANK YOU!