2. CONTACT LENSES

3. CONTACT LENSES

4. CONTACT LENSES
Optical devices placed directly in front and adjacent to cornea
To rectify refractive errors
To provide protection
To improve cosmetics

5. 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
PMMA-poly methyl metha crylate
CAB-cellulose acetate butyrate
HEMA-hydroxy ethyl metha crylate

6. 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
Toric contact lenses are used to correct cylindrical errors….
Torsion of a toric contact lens is prevented by incorporating D base down prism to weight the lower pole of the lens or by removing the lower mm of lens(truncation) to allow it to sit on the edge of the lower eyelid.

7. INDICATIONS OF CONTACT LENSES
Optical indications
Anisometropia
Unilateral aphakia
High myopia
Astigmatism
Keratoconus
Anisometropia is a condition in which both eyes have different refractive powers i.e, are in different states of myopia or hypermetropia.it can adversely affect the development of binocular vision in infants and children if there is a large difference in the clarity b/w the 2 eyes.the brain will often suppress the vision of blurred eye in a condition called Amblyopia or lazy eye.it also leads to diplopia and Aniseikonia which is difference in the size of 2 eyes images.contact lenses are useful here because they have short vertex distance n are thin so the image size is changed less as compared to spectacles.unilateral aphakia also leads to image magnification,aniseikonia,diplopia and divergent squint in adults(esotropia in children).contact lenses cause significantly less magnification than spectacles.

8. Contd Therapeutic indications(BCLs) Corneal diseases Iris 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)
Promotion of epithelial healing
Epithelial Defects can be healed more quickly by protecting the corneal regenerating epithelium from constant rubbing action of lids
Recurrent corneal erosion syndrome if associated with corneal dystrophy
Pain relief
Bullous keratopathy can be managed by soft contact lens
Filamentary keratitis – soft contact lens plus artificial tears

9. 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

10. INDICATIONS (CONTD) 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

11. Advantages over spectacles
Visual fields
Optical aberration
Accommodation and convergence
Prisms
Tint
A contact lens moves with the eye….
Good vision in all positions of gaze….
Dec peripheral distortions…..inc VF…
Inc demand for accommodation n convergence bcoz of no prismatic effect…myopic spectacles have base-in prismatic effect which reduces the amount of A n C reqd for near….
3 D of prism power to contact lens easily without making it too thick to be practical…prism is base down…impossible horizontal prismatic correction…
With scleral contact lenses,both vertical n horizontal prisms incorporated…6 prism D…

12. CLINICALLY IMPORTANT FEATURES
Field of vision
larger field
avoid peripheral distortion
Image size
Spectacle frame reduces the field of corrected vision by about 20 degrees.
Plus spectacles and contact lenses both increases the image size but contact lenses do so to lesser extent.vice versa for minus lenses.

13. CLINICALLY IMPORTANT FEATURES
Accommodation
Myopic correction– increased requirement
Hypermetropic correction– decreased requirement
Myopic spectacles base in effect.
Visual axis is directed towards B when looking at a near point A.
Contact lens correction of myopia increases the accommodative and convergence demands when focusing near objects proportional to the size of refractive error . reverse is true in hypermetropia.

14. CONTACT LENS FITTING

15. SCLERAL CONTACT LENSES
Indications
Astigmatism(keratoconus,post PKP)
Ocular surface disease
Diameter 25 mm………
Correct abnormal regular and irregular astigmatism e,g keratoconus, astigmatism after PKP
E;g tear layer disorders,trichiasis,accelerate healig of persistent epithelial defects that are refractory to all other treatment strategies

16. COMPLICATIONS
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

17. Corneal oedema Commonest and earliest corneal change
Occurs due to hypoxia of corneal epithelium.This occurs when lenses with poor oxygen transmission are worn overnight. Under the closed-eye sleeping
conditions, oxygen availability is decreased to a level where endothelial cell dysfunction occurs leading initially to stromal than epitelial edema , finally bullae formation occurs

18. Contact Lens Red Eye with pain & photophobia

19. Giant papillary conjunctivitis
is more common in patients wearing soft lenses . Immunological origin in which contact lens deposits esp protiens act as allergens.

21. Corneal neovascularization
Ch hypoxia , tight or thick lens.
Doesnot extend beyond 2 – 3mm
If severe short course of steroids

22. Microbial keratitis
The pattern of causal organisms is slightly different in contact lens wearers. There are relatively more Gram negative organisms, which reflects the alteration in commensal populations in contact lens wearers which, inturn, is due to the watery extraocular environment in which contact lenses are maintained. For the same reason, contact lens wearers are more susceptible to acanthamoeba keratitis

23. THANK YOU