applied antomy of lens and viterous.lens location, structure, refractive power, structure, lens transparency, viterous function,structure,attachments, clinical notes

1. ANATOMY
OF EYE
DR SPARSHA S K
1ST year shalakya tantra
AAMC

2. LENS
2

3. 3
The lens is a transparent,
biconvex, elliptical, semisolid,
avascular body of crystalline
appearance located between
the iris and the vitreous

4. Location
4

5. 5

6. Refractive power
6

7. Structure
1) Lens capsule
2) Anterior epithelium
3) Lens fibres
7

8. Lens capsule
It is a thin, transparent, hyaline
membrane surrounding the lens
 which is thicker over the anterior than
the posterior surface.
The lens capsule is thickest at pre-
equator regions (14 m)
thinnest at the posterior pole (3 m). 8

9. Clinical Notes
9
True exfoliation of the lens posterior capsule rupture

10. Anterior epithelium
It is a single layer of cuboidal
cells which lies deep to the
anterior capsule.
In the equatorial region these
cells become columnar
 There is no posterior
epithelium,
10

11. 11
Shield cataract in atopic
dermatitis
Glaucomflecken

12. Posterior Capsular
Opacification
Posterior subcapsular
cataract
Elschnig pearls Soemmering's ring
12

13. Lens fibres
The epithelial cells elongate to form
lens fibres
Mature lens fibres are cells which have
lost their nuclei. As the lens fibres are
formed throughout the life, these are
arranged compactly as
A. nucleus
B. cortex
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14. Nucleus
It is the central part containing the oldest fibres.
It consists of different zones,
In the beam of slit-lamp these are seen as zones of discontinuity.
14

15. Depending upon the period of development, the different zones
of the lens nucleus include
It is the innermost part of
nucleus which
corresponds to the lens
upto first 3 months of
gestation. It consists of
primary lens fibres which
are formed by elongation
of the cells of posterior
wall of lens vesicle
It lies around the
embryonic nucleus and
corresponds to the lens
from 3 months of
gestation till birth. Its
fibres meet around sutures
which are anteriorly Y-
shaped and posteriorly
inverted Y-shaped
Embryonic nucleus Fetal nucleus
corresponds to the lens
from birth to puberty
Infantile nucleus
15
Adult nucleus
lens fibres formed after
puberty to rest of the life

16. Cortex
peripheral part which comprises
the youngest lens fibres

17. Clinical point
17

18. Suspensory ligaments of lens
Suspensory ligaments of lens
(Zonules of Zinn), also called as
ciliary zonules,
Consist essentially of a series of
fibres passing from ciliary body to
the lens.
These hold the lens in position
and enable the ciliary muscle to act
on it.
18

19. 19

20. 20

21. Lens transparency
Avascularity of the lens.
Characteristic of lens fibre:
– Tightly-packed nature of lens cells,
– Narrow lens fibre membranes,
– Loss of organelles
 lens proteins.
Lens capsule: Semipermeable character.
Pump mechanism of lens fibre membranes that regulate the electrolyte and water
balance in the lens, maintaining relative dehydration
 Auto-oxidation and high concentration of reduced glutathione in the lens maintains
the lens proteins in a reduced state and ensures the integrity of the cell membrane pump
21

22. Clinical Notes
lens becomes opaque
22
Cataract

23. CONGENITALANOMALIES OF LENS
a notch in the lower
quadrant of the equator
cone-shaped elevation
of the anterior pole
Coloboma of lens Lenticonus
lens is spherical in
shape (instead of
normal biconvex) and
small in size
Microspherophakia
23

24. VITREOUS

25. Inert, transparent, jelly-like structure
that fills the posterior four-fifth of the
cavity of eyeball.
Spherical posteriorly and has a cup-
shaped depression (patellar fossa)
anteriorly.
It conforms to the contour of retina
behind and lens infront.
4 ml in volume
4 gm in weight.
25

26. Contains more than 98% of water
It has viscosity more than 2-3 times than that of water.
Refractive index 1.33
The word “vitreous” is derived from a Latin word “vitrum” which
means glass
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27. Functions
It is a hydrophilic gel that mainly serves the optical functions.
It mechanically stabilizes the volume of the globe
Is a pathway for nutrients to reach the lens and retina.
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28. Structure
The normal youthful vitreous gel is composed of a network of
randomly-oriented collagen fibrils interspersed with numerous
spheroidal macromolecules of hyaluronic acid.
 The collapse of this structure with age or otherwise leads to
conversion of the gel into sol.
two parts: the cortex and
the medulla or nucleus (the main vitreous body)
28

29. Cortical vitreous
lies adjacent to the retina posteriorly
ciliary body, zonules and lens anteriorly.
The density of collagen fibrils is greater in this peripheral part.
The condensation of these fibrils form a false anatomic membrane
which is called as anterior hyaloid membrane anterior to ora serrata
and posterior hyaloid membrane posterior to ora.
29

30. Medulla or nucleus
has a less dense fibrillar structure and is a true
biological gel.
here where liquefactions of the vitreous gel start first.
Microscopically the vitreous body is homogenous, but
exhibits wavy lines as of watered silk in the slit-lamp
beams.
Running down the centre of the vitreous body from the
optic disc to the posterior pole of the lens
30

31. Attachments
vitreous base-vitreous about 4 mm across the
ora serrata
margins of the optic disc, foveal region and
back of the crystalline lens-hyaloidocapsular
ligament of Wiegert
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32. Clinical Notes
Detachment of the Vitreous
the attachment to the retina is weak, and in
pathologic conditions the vitreous is easily
detached.
32

33. Accumulation of Fluid in the Retrolenticular
Space
retrolenticular space
Blood or exudates can accumulate in this space
in pathologic conditions.
Senile Changes in the Vitreous
degeneration and liquefaction.
vitreous detachment
predispose to retinal detachment.
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34. Refference
Comprehensive Ophthalmology by AK Khurana
BD Chaurasia’s Applied Dissection and Clinical Head and
Neck 8th edition
Clinical Anatomy of the Eye by Richard S. Snell 2nd edition
www.eoptha.com
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35. Thank you