This ppt covers anatomy, dimensions, microscopic structure, arrangement of lens fibers, ciliary muscles, Nucleus development, accommodation and its theories etc... It is useful for optometry students, educational purposes etc.. #Optometrist #OPTOMETRY #EYECARE #OPTOMETRY_STUDENTS #UPUMS #CRYSTALLINE_LENS #ACCOMMODATION

1. U.P.U.M.S.
Paramedical Vigyan
Mahavidhyalaya

2. Represented by -
Ashith Tripathi
Submitted to –
Gaurav sir

4. INTRODUCTION
The lens of the eye is a transparent,
biconvex, elliptical, semi solid,
avascular body of crystalline
appearance located between the iris
and the vitreous.
Weight of lens varies with age.

5. Equatorial diameter 6.5 mm at
birth, increases to 9 to 10 mm in
the second decade and then
remain almost constant.

6.  Thickness (axial or anterioposterior
diameter ) varies with age between 3.5 mm
(at birth ), about 4 mm at 40 years and
increase slowly to 4.75 to 5 mm in extreme
old age.
 The weight is approximately 260 mg at 70 -
80 years of age.
 In males, the lens weight more than the
aged matched females, with a mean
difference of 7.9 to 2.47 mg.

7. SURFACES
Lens has two surface-
Anterior
surface
Posterior
surface

8.  It is less convex than the posterior
surface.
 The anterior surface is the segment
of a sphere whose radius average 10
mm.
 The center of anterior surface is
known as the anterior pole, and is
about 3 mm from the back of the
cornea.
ANTERIOR SURFACE

9. It is more curved than the anterior
and present a radius of about 6
mm (4.5-7.5) .
The centre of posterior surface is
called as posterior pole.
It lies in a fossa lined by the
hyaloid membrane on the front of
the vitreous.
POSTERIOR SURFACE

10. REFRACTIVE INDEX
The refractive index of the lens is 1.39 (
nucleus 1.42, cortex 1.38 ) , which is
slightly more than that of the aqueous (
1.336 ) and vitreous humor ( 1.3349 ).
The refractive power is about 16 – 17
dioptres, out of a total of about 60 diopters
for the normal eye.

11. Accommodative power is 15 - 16 diopters,
diminishing to half of this at about 25 years of
age and to 2 diopters or less at age 50 years.

12. Structure
The lens consists of –
1. The lens capsule
2. The lens epithelium and
3. The lens cells or fibers
STRUCTURE

14. LENS CAPSULE
It is a thin, transparent, hyaline
collagenous membrane which
surrounds the lens completely.
The lens capsule is highly elastic
but does not contain any elastic
tissue.

15. CHARACTERISTICS OF THE LENS CAPSULE
The capsule completely envelops
the lens and the cells of origin are
completely contained in it.
The capsule is the basement
membrane of the lens epithelium
and is the thickest basement
membrane of the body.

16.  It is much thicker in front than behind and the
anterior and posterior portions are thicker towards
the periphery ( equator ) just within the attachment
of the suspensory ligament than at the poles.

17.  The thickness at the posterior pole is 2.8 – 4
microne meter and at anterior pole is 15.5
microne meter.
 Capsule thickness increase anteriorly with
age.
Under the light microscope the
capsule appears transparent,
homogenous.
ON MICROSCOPES

18. However, on ultramicropic
examination, it shows a lamellar
appearance.
Under electron microscope the
capsule appears to have a relatively
amorphous appearance.
There are up to 40 lamellae each of
which is 40 mm thick.

19. THE LENS EPITHELIUM
The lens epithelium consists of a
single shut of cuboidal cells spread
over the front of the lens, deep to the
capsule and extending outwards to the
equator.
There are about 500,000 cells in the
mature lens.
There cells contain all the organelles
found in a typical epithelium cell.

20. Almost all the metabolic, synthetic and transport
process of the lens occur in this layer.
EQUATOR

21. ZONES OF LENS EPITHELIUM
There are 3 zones in the lens
epithelium.
The central zone represents a stable
population of cells.
The intermediate zone is peripheral to
central zone and its cells are smaller.
The germinative zone is the most
peripheral and is located just pre
equatorially.

22. FEATURES OF LENS EPITHELIUM
The highest metabolic rate occurs
in the anterior lens epithelium,
because the content of ATP and
enzymes is highest in this area of
lens.

23. THE LENS FIBRES
 The epithelial cells elongate to form the lens
fibres are formed from the posterior
epithelium which runs from posterior to
anterior to fill the lens vesicle.
 But later on, the lens fibres are derived from
the cells of the equatorial region of the
anterior epithelium.
 These cells divide, elongate and
differentiate to produce long, thin, regularly
arranged the bulk of the lens .

24.  Mature lens fibres have no organelles or
nuclei.

25. ZONAL ARRANGEMENT OF LENS FIBRES
 The lens fibres are formed throughout life
and are arranged in zones that describe the
various development periods of the lens.
a. Nucleus
b. Cortex
a) Nucleus – It is central part containing the
oldest fibres. It consists of different zones.
Embryonic nucleus is its innermost part.
(formed at 1 to 3 months of gestation )

27. Fetal nucleus (corresponding to lens
from 3 months of gestation till birth)
Infantile nucleus ( corresponding to lens
from birth to puberty )
Adult nucleus (corresponding to the lens in
adult life)
b) Cortex – it is peripheral part of the lens
substance which lies just outside the adult nucleus.
It include the youngest lens fibres.

29. THE CILIARY ZONULES
 The ciliary zonules ( zonules
of Zinn or suspensory
ligament of lens ) consists
essentially of a series of fibres
which run from the ciliary
body and fuse into the outer
layer of the lens capsule
around the equatorial zone.
 Thus, they hold the lens in
position and enable the ciliary
muscle to act on it.

31. ACCOMMODATION
Accommodation is the ability to increase
the refractive power of eye by changing the
shape of the crystalline lens.
Accommodation is the process by which
one can focus the object at differences in a
bid to have a clear vision.
In humans the process of accommodation
is achieved by a change in the shape of
the lens.

34. ASHITH TRIPATHI
DIRECTED BY -
GUIDED BY -
MR. GAURAV DUBEY

35. SPECIAL THANKS
Gaurav sir
Thanks
 Aman Tiwari
 Himanshu Yadav
 Shiv pratap
 Dadhesh mathur
 Rajat bansal

36. DESIGN AND ANIMATED BY -
Ashith tripathi
Aman Tiwari
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