about the human crystalline lens anatomy and some of its related disease

1. OPTICS OF THE CRYSTALLINE
LENS
PRESENTED BY
ARUNDHATI HATIKAKOTY
BSc OPTOM 2ND YEAR
ROLL NO-202
RIDLEY COLLEGE OF OPTOMETRY

2. INTRODUCTION
 The lens is a transparent biconvex, crystalline
structure placed between the iris and the vitreous in
a saucer shaped depression named THE PATELLAR
FOSSA
 The lens along with the cornea helps to refract light
so that the refracted light is focused on the retina
 The anterior side is more flatter than the posterior
side.

4. DIMENSIONS OF THE LENS
 Equatorial diameter- 6.5mm (at birth)
9-10 mm (at 2nd decade) and
then almost remains constant.
 Thickness- 3.5mm (at birth)
5mm (at extreme of age)
 Weight- 135mg (0-9 years)
255mg (40-50 years)

5. Cont…
• Two surfaces- 1) anterior 2) posterior
• ANTERIOR SURFACE- less convex, radius averages
10mm (8-14mm)
• POSTERIOR SURFACE- more curved, presents a radius
of about 6mm (4.5-7.5mm)
• The center of the anterior and posterior surface is
called anterior and posterior pole respectively.

6. Cont…
• The anterior pole is about 3mm back from the
cornea.
• Refractive index- 1.39
(nucleus -1.42)
(cortex – 1.38)
• Refractive power- 16-17 dioptres
• Accommodative power- 14-16 D (at birth)
7-8 D (at 25 years of age)

7. Cont…
1-2 D (at 50 years of age)
 The color of the lens also changes with age.
 The color of the lens becomes yellow in old age
 In young adults and infants the lens is colourless.

8. STRUCTURE OF THE LENS
The Lens Capsule
Anterior Lens Epithelium
The Lens fibres

10. THE LENS CAPSULE
 It is a thin membrane hyaline structure that
surrounds the lens completely
 It is the thickest basement membrane of the body
 The lens capsule is highly elastic but it doesn’t
contain any elastic tissues
 This layer is secreted by the basal cell area of the
elongating fibres posteriorly
 Its thickness varies with age. It is thicker anteriorly
than posteriorly and at the equator than the poles,
and is thinnest at the posterior pole

11. ANTERIOR LENS EPITHELIUM
 Single layer of cuboidal nucleated epithelial cell.
 Almost all metabolic, synthetic and transport
processes of the lens occur in this layer. It consists of
three zones- 1) Central zone
2) Intermediate zone
3) Germinative zone
 It has the highest metabolic rate

12. LENS FIBRES
 Formed by epithelial cells
 At first, the lens fibres are formed from the posterior
epithelium which runs from posterior to anterior to
fill the lens vesicle
 Later, 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 lens fibres that
constitute the bulk of the lens

13.  The lens fibres are formed throughout the life
 Mature lens fibres are cells which have lost their
nuclei
 Lens fibres are arranged compactly as nucleus and
cortex of the lens

14. NUCLEUS
 It is the central part containing the oldest fibres
 It consist of different zones
Embryonic nucleus
Fetal nucleus
Infantile nucleus
Adult nucleus

15. CORTEX
 It is peripheral part which comprises the youngest
lens fibres

16. FUNCTION OF THE LENS
Two main function of the lens is-
To focus light on the retina
To help the eyes focus on objects at
various distances

17. ROLE OF LENS IN ACCOMMODATION
• The lens, by changing shape, functions to change the
focal distance of the eye so that it can focus on
objects at various distances, thus allowing a sharp
real image of the object of interest to be formed on
the retina. This adjustment of the lens is known as
accommodation

18. LENS TRANSPARENCY
 Avascularity
 Lenscapsule: Semipermeable character
 Characteristic of the lens fibres :
Tightly-packed nature of the lens cells,
Narrow lens fibre membranes
Loss of organelles

19.  Pump mechanism of the 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

20. DISEASES OF THE LENS-
CATARACT
 Any opacity in the lens or its capsule
 It may occur either due to formation of opaque lens
fibres or due to degenerative process leading to
opacification of the normally formed transpaent lens
fibres

22. CLASSIFICATION OF CATARACT
Based on-
1) MORPHOLOGY
2)AGE OF ONSET
3)MATURITY
4)ETIOLOGY

23. 1)MORPHOLOGY-
Capsular cataract
Sub capsular cataract
Nuclear cataract
Lamellar cataract
Sutural cataract

24. 2)AGE OF ONSET-
Congenital cataract
Infantile cataract
Juveline cataract
Pre senile cataract
Senile cataract

25. 3)MATURE-
Intumescent cataract
Immature cataract
mature cataract
hypermature cataract- 1) fibrotic type
2)morganian type

26. 4)ETIOLOGY-
Congenital cataract
Acquired cataract

27. MANAGEMENT OF CATARACT
 1) Non-Surgical Measures
 2)Surgical Measures-
a)ICCE
b)ECCE
c)Manual small incision cataract surgery
d)Phacoemulsification
e) Microinision cataract surgery
f) Lensectomy
g) intra ocular lens implantation

28. DISPLACEMENT OF THE LENS
 Displacement of the lens from its normal position
results from partial or complete rupture of the lens
zonules
 May be divided into basic two types-
1)Clinico etiological types
a)congenital displacements
b)traumatic displacements
c)consecutive or spontaneous
displacement
2)Topographical types-
a)sub luxated lens
b)dislocation or luxation of the lens

29. TREATMENT
 Spectacle or contact lens correction for phakic and
aphakic area
 Lensectomy with anterior vitrectomy is performed in
desperate cases

30. CONGENITAL ANOMALIES OF THE
LENS
Coloboma of the lens
Congenital ectopia lentis
Lenticonus
Congenital cataract
microspherophakia

31. • REFERENCE-
AK Khurana, Comprehensive opthalmology 6th
edition- pg no. 179-218
AK Khurana, Anatomy and physiology of the
Eye 6th edition- pg no. 85-91

32. THANK YOU