M.S Opthalmology

1. Dr. Aayush Tandon
Anatomy of the Crystalline lens

2.  It is a highly organised system of specialsed cells.
 It constitutes an important component of the optical
system of the eye.
Introduction
1. It allows the passage of incident light to the
retina as it is transparent.
2. It enables the eye to focus the images of the
objects on the retina lying at distances from near
to infinity ( accomodation)
3. Lens helps in refraction of light and it constitutes
one fourth of total diopteric power of the eye.

3. Anatomy
 It is a transparent, avascular, biconvex,semisolid,intraocular,
crystalline structure placed between the iris and vitreous in a
saucer shaped depression the patellar fossa.
 It is attached posteriorly to the vitreous in a circular manner
with Ligamentum Hyaloideocapsulare also called Wiegerts`s
ligament.
 Between the hyaloid face and lens capsule there there is a
small potential space called retrolental or Bergers space.
 It is supported in its position by zonules of zinn or suspensory
ligaments.

5.  Like any other lens the crystalline lens has 2 surfaces , anterior and
posterior
 Anterior surface is less convex as compared to the posterior surface
 The centre of anterior and posterior surfaces is called as the
anterior and posterior pole respectively.
 The anterior pole is about 3mm from the back of cornea

6.  The lens is unique among organs in that is contains cells solely
of a single type , in various stages of cytodifferentiation and
retains within it all the cells formed during life time .
 As cells become older and more embedded they undergo several
changes, losing organelles and to some extent their structural
integrity and becoming progressively more inert metabolically.
 As no cells are shed the lens demonstrates cells at varying states
of senescence.

7. Dimensions
1. Radius of anterior surface - 10 mm (8-14mm)
2. Radius of posterior surface - 6 mm (4.5- 7.5mm)
3. Anterior pole- 3 mm from the back of cornea.
4. Equatorial diameter
 6.5mm at birth
 10mm in adults

8. 6. Axial width ( AP width)
 At birth- 3.5-4 mm
 In adults- 4.75- 5 mm
7.Refractive index of lens
 As a whole – 1.39
 Nucleus – 1.42
 Cortex- 1.38
8. Refractive power – 16-17 D
9. Weight of lens
 at birth- 65 mg
 at around 10 years 135 mg
 at extremes of age- 258 mg

9. 10. Accomodative power
 at birth - 14-16 D
 at 25 yrs - 7-8 D
 at 50 yrs - 1-2 D
11. Colour of lens
 Infants – Transparent
 Young adults - Colourless
 After about 30 yrs of age - yellowish tinge
 Old age- amber colour
12. Consistency of lens- Semisolid cortex is softer as compared to the
nucleus

10.  It is composed of 64% water,35% proteins and 1 %
lipids, carbohydrates and other trace elements.
Structure of lens:
1. Lens capsule
2. Lens epithelium
3. Lens Fibres

11. Lens capsule
 It is a thin , transparent, hyaline collagenous membrane which
surrounds the lens completely.
 It is secreted by the basal cells of anterior lens epithelium anteriorly and by
the basal area of elongating lens fibers posteriorly.
 It is the thickest basement membrane of body.
 It is an inverted basement membrane facing inside of closed cavity.
 It is more thick anteriorly than posteriorly and at equator than poles.
 It is thinnest at the posterior pole.
 It is mainly made up of of type-IV collagen and Glycomaminoglycans.

13.  Capsule thickness increases anteriorly with age but there is little change
at the posterior pole.
 On microscopy the capsule appears as a homogenous, transparent
structure showing a Lamellar appearance with fibres arranged parallel to
its surface

14.  There are upto 40 lamellae , each of which is about 40 nm thick .
 The lamellar structure becomes modified with age since it
disappears from the posterior pole during the first decade and
from the anterior aspect four to five decades later.
 Basement membrane origins of the capsule are displayed by a
positive PAS reagent which stains the glycoprotein matrix
 The capsule is permeable to water, ions and other small molecules
and offers a barrier to large protein molecules.

15. Anterior lens
epithelium
 It is a single layer of cuboidal nucleated epithelial cells.
 Contains all the organelles found in a typical epithelial cell
 Cells have a high metabolic rate ( content of ATP and enzymes
highest in this area of lens
 Almost all metabolic, synthetic and transport process of lens occurs
here.
 In the equatorial region these cells become columnar and are
actively dividing and elongating to form new lens fibres through out
life
 There is no corresponding posterior epithelium

16.  There are about 500000 epithelial cells in a mature
lens .
 These cells have a prominent well characterised
cytoskeleton network consisting of Actin , myosin.
Alpha actinin , vimentin , spectrin & microtubules .
 This well defined cytoskeleton compartmentalizes the
cell interior .
 The cytoskeletal network is in the form of polygonal
array of geodomes located subjacent and attached to
their apical membrane .

18. Central zone :-
 It consists of cuboidal cells.
 These cells are stable and their number reduces with the age.
 Normally, these cells do not mitose.
 But can do so in response to various insults like uveitis, atopic dermatitis.
Intermidiate zone :-
 It contains small but more cylindrical cells.
 They can mitose occasionally.
Germinative zone :-
 It consists of coloumnar cells.
 These are actively dividing and elongating to form new lens fibres.
 Very susceptible to irradiation.

20. PSC

21. Lens fibres
 Anterior lens epithelium elongates to form the lens fibres.
 They form the main bulk of the lens
 They are long thin transparent cells firmly packed with diameter of
4-7 micron and length upto 12mm
 New cell fibres are laid on the older deeper fibres
 Superficial new fibres are nucleated with elongation of the cell
 The nuclei assume a more anterior position
 Anterior shifted nucleus of the newly formed cells form the line
convex forward at equator, called as nuclear or lens bow.

23.  On cross section the lens fibres are hexagonal in shape and are bound
together by ground substance .
 The cytoplasm of lens fibres are devoid of nuclei with very few organelles

24.  There are interlocking processes between cells as ball-and-socket and
tongue-and-groove interdigitations.
 Interdigitations are less complicated in superficial zone to permit
moulding of the lens in accomodation.
 Lens fibers exhibit numerous gap junctions

25.  Initial fibres forming the foetal nucleus terminate with two Y-shaped
sutures, anteriorly upright Y and posteriorly inverted Y.

26.  In adults continuously forming fibres are arranged compactly as nucleus
and cortex.
 With further growh there is symmetrical branching of sutures forming
the 9 point star of the mature cortex

27. Nucleus :
 Central part containing the oldest fibres
Parts of nucleus-
1. Embryonic nucleus (1-3 months of
Gestation)
1. Fetal nucleus (3 months – birth)
2. Infantile nucleus (Birth- puberty)
3. Adult nucleus.

28. Cortex
 Peripheral part
 It has the youngest fibres.
 Histologically ,section through the equator shows the hexagonal structure
of lens fibres and bound together by ground substance.

29. Surgical Anatomy

30. Grading of nucleus hardness
Grade 1 – Green yellow
Grade 2 – Yellow
Grade 3 – Amber
Grade 4 –Brown
Grade 5 – Black

31. Ciliary Zonules
 The ciliary zonules ( Zonules of Zinn or Suspensory ligaments )
consist of a series of stiff, non elasitic fibres which run from ciliary
body and fuse into the outer later of the lens capsule
 The ciliary epithelial cells of the eye probably synthesize portions of
the zonules
 The zonules are primarily made of fibrillin, a connective tissue
protein
 Each zonular fibre has a diameter of about 0.35 – 1 microns
 It is composed of microfibrils, glycoproteins and
mucopolysaccharides
 They hold the lens in postion and enable the ciliary muscles to act on
it

32. Gross appearance
 Grossly, the ciliary zonules from a complete ring of fibres, which extend
from ciliary body to the lens equator circumferentially.
 On cut section the ciliary zonules appear to be arranged in a triangular
form.

33.  The base of the triangle is towards the equator of the lens and apex towards
the ciliary body .
 As the zonular fibres insert on the lens capsule a narrow space is created
around the equator which is called the ‘The canal of Hanover

35. Structurally , 3 different types of fibres-
 1) First type fibres- thick,wavy and lie near
vitreous.
 2) second type fibres-thin and flat.
 3) third type fibres- very fine & run circular
course.

36. Arrangement of zonular fibres

38. THANK YOU

39. Arrangement of zonular fibres (New
concept)
> Majority of zonules arise from the posterior end of the pars plana upto 1.5 mm from the ora serrata
> They run a continues course from ora serrata to the edge of lens

40. Applied Anatomy
1. Capsule
2. Superficial cortex :
a) C1α- subcapsular clear zone
b) C1β- first zone of disjunction seen as bright,
narrow, scattering zone of discontinuity
c) C2 – second cortical clear zone.
3. Deep cortex :
a) C3 – bright light scattering zone
b) C4- clear zone of cortex.
4. Nucleus.

41.  In a can opener capsulotomy, improper joining of the radial cuts can lead
to a pull on the still attached capsule, as it is removed causing a posterior
extension of the tear
 Extension of the tear to the periphery may occur if the attempted rhexis
size is larger than 6mm.
 If the CCC created is larger than the proposed optic size ,the odds of
posterior capsular opacification are higher
 Creation of small rhexis (less than 4mm) carries a risk of fluid entrapment
while performing hydrodissection leading to ruptureof the posterior
capsule .
 Nucleus rotation in case of inadequate hydroprocedures can lead to
zonular dialysis