Contact lens materials, indication and complication

1. CONTACT LENS
BY DHAISY OPTOMETRIST

2. WHAT IS CONTACT LENS
 Artificial device whose front surface substitutes the
anterior surface of the cornea
 Used for correction of:
 Refractive error
 Irregularities on front surface of cornea

3. CONTACT LENS SPECIFICATIONS
 Diameter
 Overall diameter (OD)
 Optic zone diameter (OZ)

4. 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)


5.  Edge
 Union of the peripheral posterior curve and peripheral
anterior curve
 Power
 Central anterior curve determines the power of the lens
 Measured in terms of posterior vertex power in
diopters.

6.  Thickness
 Measured in the centre of the lens
 Varies depending upon the posterior vertex power of
the lens
 Tint
 Color of the lens

7. TYPES OF CONTACT LENS
 Hard Lens
 Rigid Gas Permeable Lens
 Soft Lens
 Hybrid lens (Central RGP with peripheral soft lens)
 Scleral lens

10. HARD LENS
 From PMMA (polymethylmethacrylate)
 High optical quality, stability, light weight, nontoxic,
durable and cheap
 Diameter 8.5 – 10 mm
 Disadvantages
 Restricting the tolerance
 Corneal abrasions
 Stable tear film

11. RIGID GAS PERMEABLE LENS
 Material permeable to oxygen
 Hard, but called as semisoft lenses
 Manufactured from
 Copolymer of PMMA
 Silicone containing vinyl monomer
 Cellulose acetate butyrate

13. SOFT LENS
 HEMA (hydroxyethylmethacrylate)
 About 1-2 mm larger than corneal diameter
 Advantages
 Comfortable
 Well tolerated

15. SOFT LENS
 Disadvantages
 Wettability
 Proteinaceous deposits
 Can get torn
 Limited life
 Inferior optical quality
 Increased risk of corneal infections
 Cannot correct astigmatism >2D

16. SOFT LENS
 Types
 Disposable or non-disposable
 Clear or colored
 Spherical or toric
 Extended wear
 Multifocal

17. 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

18. 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 effects of a spherical
lens.
 Corrects astigmatism
 Lens is specially weighted to conform to irregular
cornea
 More expensive than spherical
 Some are available in disposable

19. TORIC CONTACT LENS

20. DISPOSABLE SOFT LENS
 Daily two-weekly or monthly replacement
 Very simple cleaning (no cleaning for daily)
 Latest designs and materials
 Very popular

21. 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

22. EXTENDED WEAR CONTACT LENS
 New technology
 Made form silicone hydrogel material which
transmits oxygen well
 Can wear for up to thrity days without removing

23. MULTIFOCAL CONTACT LENS
 Can have dual focus lenses
 New technology – more expensive
 Available as disposable lenses

24. INDICATIONS
 Optical
 Therapeutic
 Preventive
 Diagnostic
 Operative
 Cometic
 occupational

25. OPTICAL INDICATIONS
 Anisometropia
 Unilateral aphakia
 High myopia
 Keratoconus
 Irregular astigmatism

26. ADVANTAGES OVER SPECTACLE
 Can correct irregular astigmatism
 Normal field of vision
 No aberrations binocular vision in high
anisometropia
 No condensation of rain or fog
 Cosmetically more acceptable

28. THERAPEUTIC INDICATIONS
 Diseases of Cornea (thinning and perforation)
 Diseases of Iris (aniridia)
 Glaucoma – drug delivery
 Amblyopia
 Bandage soft contact lenses

29. PREVENTIVE INDICATIONS
 Prevention of symblephron and restoration of
fornices in chemical burns
 Exposure keratitis
 trichiasis
Eposure keratitis
symplepheron
trichiasis

30. DIAGNOSTIC INDICATIONS
 Gonioscopy
 Electroretinography
 Examination of fundus in case of irregular corneal
astigmatism
 Fundus photograhy
 Goldmann’s 3 mirror examination

31. OPERATIVE INDICATIONS
 Goniotomy operation for congenital glaucoma
 Vitrectomy
 Endocular photocoagulation (retinal endo-laser)

32. COSMETIC INDICATIONS
 Unsightly corneal scars
 Ptosis
 Cosmetic scleral lenses in phthysis bulbi

33. OCCUPATIONAL INDICATIONS
 Sportsman
 Pilots
 Actors

34. CONTRAINDICATIONS
 Mental incompetence / poor motivation
 Monocularity
 Anterior segment inflammation or infection like
 Chronic blepharatis and recurrent styes
 Chronic conjunctivitis
 Dry-Eye syndrome
 Corneal dystrophies and degenerations
 Recurrent diseases like episcleritis, scleritis & iridocylitis
 Chronic dacryocystitis
 Occupational incompatibility
 Poor hygiene

35. COMPLICATION OF CONTACT LENS