This document provides information on contact lenses, including their indications, contraindications, types, fitting procedures, parameters, complications, and special considerations. It discusses rigid gas permeable, soft, therapeutic, extended wear, disposable, and cosmetic contact lenses. Key details include the materials used to manufacture different contact lens types, advantages and disadvantages, fitting considerations like base curve and power, and potential post-fitting complications.

1. CONTACT LENS

2. INDICATIONS & C/I
• Artificial device whose front surface substitutes the
anterior surface of the cornea .
• Indications • Optical • Therapeutic • Preventive •
Diagnostic • Operative • Cosmetic • Occupational
• C/I: mentaly unsound,irresposible,unable to use
hands
:eye d/s
:occupational hazards
:Nerve palsy
:poor hygeine

3. TYPES OF CONTACT LENSES
Broadly : focons & filcons
Depending upon nature of material used
• Rigid non gas Permeable Lens :PMMA
• Rigid Gas Permeable Lens :CAB,silicone
• Hydrophilic Soft Lens :hydrogel lenses

4. RIGID NON GAS PERMEABLE CL
• PMMA/acrylic lenses.
• Advantage:optical quality,stability,light weight
:excellent moulding,easy manufacturing
:non toxic,non allergic.
• Disadv :o2 impermeable
:hard->corneal abrasions
:hydrophobic nature resists wetting

5. RGP CL/SEMISOFT LENSES
• Rigid as PMMA,but o2 permeable.
• Materials used :cellulose acetate butyrate
:silicone,silicone acrylate
:styrene
:fluoropolymers

6. Rigid CL –adv & disadv
• Better Quality of vision
• Durable
• Deposit resistant
• Low risk of infection
• Less cost & easy handling
• Correction of astigmatism
• Modified in office
• Less comfortable & adaptable
• Over wearing->pain
• Spectacle blur
• Difficult to achieve on eye stability.
• Glare,photophobia

7. SOFT CL
• Made of hydrogel[co-polymerisation products of
hydrophilic monomers with ethylene glycol
dimethyl acrylate].
• Hydrogel lens materials :HEMA
:HEMA VP
:MMA-PVD
:Glycidyl methacrylate

8. Soft CL –adv & disadv
• Easy adaptation & comfortable wear.
• Over wear reactions less
• No spectacle blur
• More on eye stability
• Varible vn :spoilage,dehydration,deposits.
• Less durable
• Correction of astigmatism not good
• Deposits high
• No office modification possible
• Not suitable in tear film abn/l p/ts
• Handling difficult
• High cost

9. MANUFACTURING,DESIGN PRESCRIPTION
& PARAMETERS OF CL
• CL blank :sheet /rod of diameter 12.7 & 15.9 mm
: thickness 3.00 & 6.5 mm.
• Semifinished blank : blank with p.curve
• Semifinished lens : both a&p curvature polished
• Finished CL : individually adjusted 4 cornea
: diameter,edge,peripheral &
intermediate areas of posterior
surface modified

10. • Diameter 1. Overall diameter (OD)
PMMA:7.5-8 mm
RGP:9-9.8 mm
Soft CL:13-15 mm
2. Optic zone diameter (OZ)

11. 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)
• Blend:smooth area of transition between radii of
curvatures
:light,medium,heavy

12. • Edge : Union of the Peri.Postr.C & Peri.Antr.C of lens
: edge lift-extend to which the most peripheral
curve differs from the base curve radius
• Power : Measured in terms of posterior vertex
power in diopters
• Thickness : Measured at the centre of the lens
: Varies depending upon the postr. vertex
power of the lens
• Tint :Color of the lens

14. OPTICS OF CL
• Contact lens placed insitu has a thin fluid film in
between it & cornea & thus it eliminates surface
irregularity of cornea & cornea is no more a ref.
surface.
• Power of corneal surface is tear-air interface.
• Corneal RI :1.37,tear film RI: 1.333
• Tear lens neutralises almost 9/10th power of a.
corneal surface , it from +48D + 5.2 D.
• CL has a fluid lens & glass lens.

15. Correction of ammetropia
• Afocal lenses:
• correction is by different curvatures of fluid lens
surfaces,mainly back vertex power of fluid lens in
air(back +front surface power).
• Disadv:too many base curves needed
:poor fitting technique
• Powered lenses:
• correction is by different curvatures of contact lens
surfaces.
• P. surface curvature is already known & a.surface
curvature is decided based on an emperical
relationship to the corneal curvature.

16. Power & magnification of CL
• CL is placed on the vertex plane.so in myopes power of CL
needed is less & hyperopes needs power than their specs
power.
• +8 D specs  125 mm
• CL  125-13 =112 mm=+8.93 D
• CL produces a magnification of 7% in aphakia.
Influence of tear lens
• RGP & tear lens :power varies with BC of CL
• BC of CL =k plano power tear lens
• BC of CL steeper than k = +ve tear lens
• BC of CL flatter than k = - ve tear lens
• For every .05mm diff in BC of CL & k,power of tear lens is
0.25 D.
• Final CL power =SAM & FAP

17. CL & accomodation
• CL accomodative & convergence requirement of
myopic eyes and decrease those of hyperopic eyes
propotionally to the amount of their refractive
errors.

18. Fitting procedure 4 rigid CL
• H/O :r/o medical C/I
Reason 4 CL wearing
General & emotional status of p/t.
• Ocular examination:
 s/l examination:conjunctival,limbal,corneal injection
 TBUT
 blink characteristics noted
 measure – corneal diameter,pupil diameter & palpebral width
4 deciding CL diameter.
Refraction :retinoscopy,subjective refraction,back vertex
distance.
Keratometry 4 measuring corneal curvature in 2 principle
meridia
Trial lens fitting:with 2 diff diametre lenses of 0.25 D in BC.

19. • Diameter : 9mm in a p/t with avg corneal diameter &
palpebral aperture.
• BC  usually flatter k reading.
• Astigmatism: BC is steeper than flatter k.
• 0.5-1 D BC 0.25 D steeper than flatter k.
• 1.0-2.0 D BC 0.5 D steeper than flatter k.
• >2D 1/3RD toricity shud b added to k 4 BC.
K1=44 K2=47, BC= 44 + [ 47-44]
3
• Power of trial lens=spectacle power in minus cylinder form
corrected 4 zero vertex distance.
Specs power : -9.25/+0.50x90⁰
Minus power form : -8.75/-0.50x 180⁰
Vertex distance : 15 mm
CL power : -7.75/ -0.50X180⁰

20. • After adaptation period evaluate trial lens for
• Position of lens: High ride
• Low ride
• Horizontal decentering
• BC determination :flat
:steep
:ideal
• Finalisation of diameter
• Finalisation of power

26. • POST FITTING MANAGEMENT
• BC radius in mm
• Optic zone & overall diameter in mm
• First back peripheral zone in mm
• 1st & 2nd peripheral curve radius in mm.
• Power of the lens in D
• BC:OZD/1ST PC r:1ST BPZ/2ND PC r :overall diameter, power (D).
• EXAMINING ORDERED LENS:
• EVALUATION OF ORDERED LENS FIT
• EDUCATE THE P/T
care
wearing schedule
how to insert & remove
recentration
• POST FIT FOLLOWUP

29. SOFT CL FITTING
• CORNEAL DIAMETER: measured with transparent
ruler.
• : HVID
• TRIAL LENS FITTING :3 choices of BC & overall
diameter ids provided from which 1 is chosen.
• INITIAL TRIAL LENS SELECTION:BC
:overall diameter
:power
• EVALUATION OF TRIAL LENS FIT.
• POST FITTING P/T MANAGEMENT
• ORDERING SOFT LENSES
• EXAMINING ORDERED LENSES & EVALUATE FIT.
• EDUCATING P/T

30. EXTENDED WEAR LENSES
• Worn day n night even for months
EXTENDED SOFT CL
• Elderly p/ts with handling problems
• Young p/ts to avoid frequent handling
• Low compliance to DWL
• Irregular work shifts
• habitual over wearers
• eg: low,high ,medium water content lenses
EXTENDED RGP CL
• Metabolic,allergic,visual problems with soft CL
• toric bifocal /high plus/minus power lenses

31. DISPOSABLE CL
• Lenses used on daily wear basis,disinfected with H2O2
overnight & disposed weekly/fortnight.
• Adv:lens deposits,preservative induced
keratitis,infectious keratitis are less
THERAPEUTIC CL
• Wound healing,mechanical support,maintain surface
hydration in dry eyes,reduce corneal surface
disorders,as a drug delivery system
COSMETIC soft CL
• tinted cl used to alter the appearance of n/l eyes
• Used in disfigured cornea,vision disturbing conditions
needing CL,occlusion therapy,to change eye colour

32. Types of cosmetic CL
• Disadv:toxic effect of tint,corneal edema
,deposits,drying of lens,blanching of vessels

33. SPECIAL CASES 4 CL USE
ASTIGMATISM
• RGP : spherical lenses
:with toric peripheral curve
:bitoric RGP
:Front surface with toric RGP
• Soft CL :Spherical soft CL
:toric soft CL
APHAKIA
• RGP :Single cut lenses
:large lenticular lenses
• Soft CL :EWCL
:Lathe cut lenticular design

34. Keratoconus
• RGP with 3 point touch technique
• Soper lenses
• Mc Guine CL
• Rose k lens
• Piggy back lens
• Hybrid lenses
• Scleral RGP lens
• Custom toric soft CL
Presbyopia
• Monovivsion CL
• Modified monovision CL
• Binocular bifocal CL

35. Complications of CL use
conjunctival complicaions
• Allergic conjunctivits
• Giant papillary conjunctivitis
• Superior limbic keratoconjunctivitis
Corneal complications
• Epithelial edema,microcysts
• Corneal abrasions
• 3 - 9 o clock staining
• Sterile corneal infiltrates
• Corneal neovascularisation
• Microbial keratitis
• corneal warpage
• Endothelial changes
CL related complications
• Physical damage to CL,CL discolouration,deposits