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Contact Lenses

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Contact lenses - a summary

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Contact Lenses

  1. 1. 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
  2. 2. Contact Lens pecifications  Diameter 1. Overall diameter [OD] - x mm 2. Optical zone diameter (OZ)
  3. 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 lens movements Power -Only in high power minus and plus lenses
  4. 4. 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]
  5. 5. Thickness  Measured in the centre of the lens  Varies depending upon the posterior vertex power of the lens Tint  Color of the lens
  6. 6. TYPES OF CONTACT LENSES Depending upon nature of material used;  Hard Lens  Rigid Gas Permeable Lens  Soft Lens
  7. 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 impermeable 2. Corneal Abrasions 3. Stable tear film
  8. 8. 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
  9. 9. SOFT LENS  Material: HEMA (hydroxymethymethacrylate)  About 1-2 mm larger than corneal diameter  Advantages: 1. Comfortable 2. Well-tolerated
  10. 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. 11. Soft Lens  Types: ▪ Disposable or Non-Disposable ▪ Clear or Colored ▪ Spherical or Toric ▪ Extended Wear ▪ Multifocal
  12. 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. 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. 14. Disposable Soft Lens  Daily, two-weekly or monthly replacement  Very simple cleaning (no cleaning for daily)  Latest designs and materials  Very popular
  15. 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. 16. Colored Contact Lens
  17. 17. Extended Wear Contacts Lens  New technology  Made from silicone material which transmits oxygen well  Can wear for up to thirty days without removing.
  18. 18. MultiFocal Contacts Lenses  Can have dual focus lenses  New technology → More expensive  Available as disposable lenses
  19. 19. Indications for use  Optical  Therapeutic  Preventive  Diagnostic  Operative  Cosmetic  Occupational
  20. 20. Optical Indications  Anisometropia  Unilateral Aphakia  High Myopia  Keratoconus  Irregular Astigmatism
  21. 21. 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
  22. 22. 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 microcorneal perforation
  23. 23. Preventive Indications  Prevention of symblepharon and restoration of fornices in chemical burns  Exposure keratitis  Trichiasis
  24. 24. Diagnostic Indications  Gonioscopy  Electroretinography  Examination of fundus in case of irregular corneal astigmatism  Fundus photography  Goldmann’s 3 mirror examination
  25. 25. Operative Indications  Goniotomy operation for congenital glaucoma  Vitrectomy  Endocular photocoagulation
  26. 26. Cosmetic Indications  Unsightly corneal scars (Coloured lenses)  Ptosis (Haptic lenses)  Cosmetic scleral lenses in phthisis bulbi
  27. 27. Occupational Indications Indications  Sportsmen  Pilots  Actors
  28. 28. Complications Eyelid Ptosis Conjunctiva Giant papillary conjunctivitis Superior limbic keratoconjunctivitis Cornea Epithelium Corneal abrasion Corneal erosion Contact lens acute red eye (CLARE) Keratitis Corneal ulcer Corneal stroma Corneal neovascularisation Corneal oedema Corneal infiltrates Corneal endothelium Endothelial polymegathism
  29. 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. 30. THANK YOU!

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