This document provides information about contact lenses, including their specifications, types, uses, and complications. It defines a contact lens as an artificial device that substitutes for the front surface of the cornea to correct refractive errors and corneal irregularities. The main types discussed are hard, rigid gas permeable, and soft lenses. Uses include optical correction as well as therapeutic, preventative, diagnostic, operative, cosmetic, and occupational indications. Complications that can occur involve the eyelids, conjunctiva, and cornea. Contraindications for contact lens use include certain eye diseases and conditions.

2. 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

3. Contact Lens Specifications
 Diameter
1. Overall diameter [OD] - x mm
2. Optical zone diameter (OZ)

4.  Curves
 Base curve (BC) or posterior central curve (PCC)
 Peripheral curves : 1. intermediate (IPC)
 2. peripheral (PPC)
 Central anterior curve (CAC) or front curve (FC)
 Peripheral anterior curve (PAC)
 Intermediate anterior curve (IAC)
- Only in high power minus and plus lenses

5. 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]

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 Lenses
Depending upon nature of material used;
 Hard Lens
 Rigid Gas Permeable Lens
 Soft Lens

8. 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

9. 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

10. Soft Lens
 Material: HEMA
(hydroxymethymethacrylate)
 About 1-2 mm larger than
corneal diameter
 Advantages: 1. Comfortable
2. Well-tolerated

11. 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 > 2.00D

12. Soft Lens
 Types:
▪ Disposable or Non-Disposable
▪ Clear or Colored
▪ Spherical or Toric
▪ Extended Wear
▪ Multifocal

13. 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

14. 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

15. Disposable Soft Lens
 Daily, two-weekly or monthly
replacement
 Very simple cleaning (no cleaning for
daily)
 Latest designs and materials
 Very popular

16. 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

17. Colored Contact Lens

18. Extended Wear Contacts Lens
 New technology
 Made from silicone material which
transmits oxygen well
 Can wear for up to thirty days without
removing.

19. MultiFocal Contacts Lenses
 Can have dual focus lenses
 New technology → More expensive
 Available as disposable lenses

20. Indications For Use
 Optical
 Therapeutic
 Preventive
 Diagnostic
 Operative
 Cosmetic
 Occupational

21. Optical Indications
 Anisometropia
 Unilateral
Aphakia
 High Myopia
 Keratoconus
 Irregular
Astigmatism

22. Advantage Over Spectacles
 Can correct irregular corneal astigmatism
 No fall off,break
 Reducing aberrations.
 Reducing aniseikonia.
 Field of vision.
 Image magnifications.
 No distortion of image.
 No aberrations – peripheral / prismatic
 Binocular vision in high anisometropia
 No condensation of rain or fog
 Cosmetically more acceptable

23. Disadvantages
 When the pupil is dilated rigid contact
lens may produce a halo.
 Eye strain in presbyopic myopes.

24. Therapeutic 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

25. Preventive Indications
 Prevention of symblepharon and
restoration of fornices in chemical burns
 Exposure keratitis
 Trichiasis

26. Diagnostic Indications
 Gonioscopy
 Electroretinography
 Examination of fundus in case of irregular
corneal astigmatism
 Fundus photography
 Goldmann’s 3 mirror examination

27. Operative Indications
 Goniotomy operation for congenital
glaucoma
 Vitrectomy
 Endocular photocoagulation

28. Cosmetic Indications
 Unsightly corneal scars (Coloured
lenses)
 Ptosis (Haptic lenses)
 Cosmetic scleral lenses in phthisis bulbi

29. Occupational Indications
Indications
 Sportsmen
 Pilots
 Actors

30. 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

31. 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

32. THANK YOU!