CONTACT LENSES CONTACT LENSES CONTACT LENSES Optical devices

CONTACT LENSES

CONTACT LENSES

CONTACT LENSES • Optical devices placed directly in front and adjacent to cornea – To rectify refractive errors – To provide protection – To improve cosmetics

CLASSIFICATION OF CONTACT LENSES • Anatomical position • Scleral contact lenses • Semi-scleral contact lenses • Corneal contact lenses • Nature of material • Rigid non-gas permeable contact lenses(PMMA) • Rigid gas permeable contact lenses(CAB) • Soft contact lenses(HEMA) • Mode of wear • Daily wear contact lenses(hard contact lenses) • Extended wear contact lenses(soft contact lenses) • Disposable contact lenses

CLASSIFICATION OF CONTACT LENSES • FDA contact lens classification • • Group 1 – Low water content (<50%), nonionic polymers Group 2 - high water content(>50%), nonionic polymers Group 3 - low water content(<50%), ionic polymers Group 4 - high water content(>50%), ionic polymers • Refractive correction • Spherical contact lenses • Toric contact lenses • Bifocal contact lenses(annular, segmental, diffractive, aspheric) • Color • Green • Brown • Blue • Uv blocking • With or without UV blocker

INDICATIONS OF CONTACT LENSES • Optical indications • • • Anisometropia Unilateral aphakia High myopia Astigmatism Keratoconus

Contd • Therapeutic indications(BCLs) – Corneal diseases • Non healing corneal ulcer • Recurrent corneal erosion syndrome(corneal dystrophy) • Bullous keratopathy • Filamentary keratitis – Iris diseases • Aniridia , coloboma , albinism – Other conditions • • Post surgery(corneal transplant, LASIK, PRK) Bell’s palsy Bleb leak posttrabeculectomy Lid abnormalities(Entropion, lid lag, trichiasis)

INDICATIONS OF CONTACT LENSES • Preventive indications • Symblepharon , restoration of fornices in chemical burns • Exposure keratitis • Cosmetic indications • Corneal scars • Cosmetic scleral lenses in pthisis bulbi • To change color • Occupational indications • Sportsmen • Pilots

INDICATIONS (CONTD) • Miscellaneous – Ptosis – haptic contact lens if no Bell’s phenomenon – Occluders – amblyopia in children – Vehicle for drug delivery – soaking a soft contact lens – Protection of normal corneal epithelium in trichiasis or threatened exposure keratopathy

• Advantages over spectacles • • • Visual fields Optical aberration Accommodation and convergence Prisms Tint

CLINICALLY IMPORTANT FEATURES • Field of vision larger field avoid peripheral distortion • Image size

CLINICALLY IMPORTANT FEATURES • Accommodation Myopic correction– increased requirement Hypermetropic correction– decreased requirement

CONTACT LENS FITTING

SCLERAL CONTACT LENSES • Indications Ø Ø Astigmatism(keratoconus, post PKP) Ocular surface disease

COMPLICATIONS 1. Allergic conjunctivitis 2. Giant papillary conjunctivitis 3. Corneal epithelial oedema 4. Peripheral corneal neovascularisation 5. Sterile corneal ulcerations 6. Corneal infection/microbial keratitis 7. Corneal warpage 8. Mechanical or hypoxic keratitis 9. Superficial punctate keratitis/dendritic keratitis

• Corneal oedema

Contact Lens Red Eye with pain & photophobia

• Giant papillary conjunctivitis

• Corneal neovascularization

• Microbial keratitis

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