This presentation is orginaly uploaded to http://kpkmedicalcolleges.tk by Dr.Suleman

1. LENS & CATARACT
Prof. Naimatullah Khan Kundi
Head, Department of Ophthalmology
Khyber Teaching Hospital
Peshawar

2. Lens
 Crystalline Lens
 Position behind the iris
 Refract light rays
 Focuses on the retina

3. Lens
 Functions




Maintains its own clarity
Provides refractive power (by contributing
to the optical system of the eye)
Provides accommodation - Allows the eye
to clearly focus objects (within a 6 m
range)
Absorbs UV light

4. Lens
 Aphakia – absence of the lens
 Results in loss of 20 D of refractive
power
 A vascular – Obtains nutrition from the
surrounding fluids
 Glucose – provides the lens with
chemical energy required to continue
growth and maintain transparency

5. Lens
 Biconvex
 Anterior Pole – The most anterior part
 Posterior Pole – The most posterior part
 Equator – The peripheral area

6. Lens & Cataract
Anatomy
 Normal Crystalline Lens

Transparent , Biconvex, Avascular

Refractive Power:

Axis: Imaginary line between Ant. & Post.
15-20 of convergence
Poles of the lens

Equater: Greatest circuference

Meridians: Lines on the surface from one pole
to the other

8. Lens & Cataract
Anatomy
 Normal Crystalline Lens (Cont’d)

Zonular Fibers: From CB to Lens (Ant. & Post.)

Capsule: BM that Encloses the nucleus, Cortex
and Lens epithelium

Growth: Grows Continuously through life
 At birth: Wt. 90mg, AP – 3.5 mm, Equatorially –
3.5mm
 Adult: Wt. 225 mg, AP – 5 mm, Equatorially – 9mm

9. Lens & Cataract
Anatomy
 Normal Crystalline Lens (Cont’d)

Older lens:
 More Curved – More refractive power
 Refractive index decrease with age (?
Increased insoluble proteins)
 Eye – Hyperopic / Myopic with age
depending upon the balance of these
opposing changes

10. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Lens Capsule

Elastic, Transparent,

BM (Type IV Collagen, Laid down by epithelial cells)

Moulds the lens substance during the accommodative
changes

Outer layer (zonular lamella) serves as the point of
attachment of zonular fibers

11. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Lens Capsule

Thickest regions:
Ant. & Post. Pre-equatorial zones

Thinnest regions:
Central Post. Pole (2-4µ m)

12. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Zonular Fibers

Support the lens

Origin: Basal lamina of non-pigmented epithelium of
Pars Plana & Pars Plicata of CB

Insertion:
Equatorial region
1.5 mm onto Ant. & Post. Capsule

Equatorial zonular fibers regress with age,
leaving triangular area

14. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Lens Epithelium
 A single layer beneath the anterior lens capsule
 Active metabolically

15. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Lens Epithelium
 Newly formed lens cells migrate toward equator 
 Change to lens fibers
 In the bow region begins the process of terminal
differentiation into lens fibers

16. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Lens Epithelium
 The cells loose organells (mitochondria, nuclei,
ribosomes)
 Lens fibers dependent on glycolysis for energy
production
 Advantage: No light absorption/scatter

17. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Nucleus & Cortex
 New lens fibers laid down through out the life
 Thus crowding and compression of older fibers
 Embryonic and fetal nuclei oldest
 Outer most fibers recent (cortex)

19. Lens & Cataract
 Normal Crystalline
Lens
 Nucleus & Cortex
 Lens sutures (anterior
and posterior “Y”)
 Formed by
interdigitations of
apical and basal cell
process
Anatomy

20. Lens & Cataract
Anatomy
 Normal Crystalline Lens
 Nucleus & Cortex
 SL biomicroscopy
 Shows multiple optical zones, having different optical
densities
 Nucleus, epinucleues, Cortex