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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
• 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
INDICATIONS (CONTD)
• 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 Astigmatism(keratoconus,post PKP) Ocular surface disease
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
COMPLICATIONS
• Corneal oedema
Contact Lens Red Eye with pain & photophobia
• Giant papillary conjunctivitis
• Corneal neovascularization
• Microbial keratitis
THANK YOU