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

Anatomy of EYE

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Page 1: Anatomy  of EYE

LENS & CATARACT

Prof. Naimatullah Khan KundiHead, Department of Ophthalmology

Khyber Teaching Hospital Peshawar

Page 2: Anatomy  of EYE

Lens

Crystalline Lens

Position behind the iris

Refract light rays

Focuses on the retina

Page 3: Anatomy  of EYE

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

Page 4: Anatomy  of EYE

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

Page 5: Anatomy  of EYE

Lens

Biconvex

Anterior Pole – The most anterior part

Posterior Pole – The most posterior part

Equator – The peripheral area

Page 6: Anatomy  of EYE

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

Page 7: Anatomy  of EYE
Page 8: Anatomy  of EYE

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

Page 9: Anatomy  of EYE

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

Page 10: Anatomy  of EYE

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

Page 11: Anatomy  of EYE

Normal Crystalline Lens

Lens Capsule Thickest regions: Ant. & Post. Pre-equatorial zones

Thinnest regions: Central Post. Pole (2-4µ m)

Lens & Cataract Anatomy

Page 12: Anatomy  of EYE

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

Page 13: Anatomy  of EYE
Page 14: Anatomy  of EYE

Lens & Cataract Anatomy

Normal Crystalline Lens

Lens Epithelium

A single layer beneath the anterior lens capsule

Active metabolically

Page 15: Anatomy  of EYE

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

Page 16: Anatomy  of EYE

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

Page 17: Anatomy  of EYE

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)

Page 18: Anatomy  of EYE
Page 19: Anatomy  of EYE

Lens & Cataract Anatomy Normal Crystalline

Lens

Nucleus & Cortex

Lens sutures (anterior

and posterior “Y”)

Formed by

interdigitations of

apical and basal cell

process

Page 20: Anatomy  of EYE

Lens & Cataract Anatomy Normal Crystalline Lens Nucleus & Cortex

SL biomicroscopy

Shows multiple optical zones, having different optical

densities

Nucleus, epinucleues, Cortex

Page 21: Anatomy  of EYE
Page 22: Anatomy  of EYE