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

8.  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
Lens & Cataract Anatomy

9.  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
Lens & Cataract Anatomy

10.  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
Lens & Cataract Anatomy

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

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

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