DR MD FERDOUS ISLAM DEPT OF OPHTHALMOLOGY CMH,DHAKA Contact Lens
DR MD FERDOUS ISLAMDEPT OF OPHTHALMOLOGY
CMH,DHAKA
Contact Lens
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
Contact Lens Specifications Diameter 1. Overall diameter [OD] - x mm 2. Optical zone diameter (OZ)
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
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]
Thickness Measured in the centre of the lens Varies depending upon the posterior vertex
power of the lens
Tint Color of the lens
Types Of Contact LensesDepending upon nature of material used;
Hard Lens Rigid Gas Permeable Lens Soft Lens
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
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
Soft Lens Material: HEMA
(hydroxymethymethacrylate) About 1-2 mm larger than
corneal diameter Advantages: 1. Comfortable 2. Well-tolerated
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
Soft Lens Types: ▪ Disposable or Non-Disposable ▪ Clear or Colored ▪ Spherical or Toric ▪ Extended Wear ▪ Multifocal
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
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
Disposable Soft Lens Daily, two-weekly or monthly
replacement Very simple cleaning (no cleaning for
daily) Latest designs and materials Very popular
Colored Contact Lens Handling tint
Useful when inserting or removing lens
Enhancing tintMakes light coloured eyes more vivid
Opaque tintCan change colour of eyes
Colored Contact Lens
Extended Wear Contacts Lens New technology Made from silicone material which
transmits oxygen well Can wear for up to thirty days without
removing.
MultiFocal Contacts Lenses Can have dual focus lenses New technology → More expensive Available as disposable lenses
Indications For Use Optical Therapeutic Preventive Diagnostic Operative Cosmetic Occupational
Optical Indications Anisometropia Unilateral
Aphakia High Myopia Keratoconus Irregular
Astigmatism
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
Disadvantages When the pupil is dilated rigid contact
lens may produce a halo. Eye strain in presbyopic myopes.
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 microcornealperforation
Preventive Indications Prevention of symblepharon and
restoration of fornices in chemical burns Exposure keratitis Trichiasis
Diagnostic Indications Gonioscopy Electroretinography Examination of fundus in case of irregular
corneal astigmatism Fundus photography Goldmann’s 3 mirror examination
Operative Indications Goniotomy operation for congenital
glaucoma Vitrectomy Endocular photocoagulation
Cosmetic Indications Unsightly corneal scars (Coloured
lenses) Ptosis (Haptic lenses) Cosmetic scleral lenses in phthisis bulbi
Occupational Indications Indications Sportsmen Pilots Actors
ComplicationsEyelid PtosisConjunctivaGiant papillary conjunctivitisSuperior limbic keratoconjunctivitisCorneaEpithelium
Corneal abrasionCorneal erosionContact lens acute red eye (CLARE)KeratitisCorneal ulcer
Corneal stroma Corneal neovascularisationCorneal oedemaCorneal infiltrates
Corneal endothelium Endothelial polymegathism
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
THANK YOU!