3. Introduction
• Asymmetric oblate spheroid
• Does not possess nerves, blood
vessels, or connective tissue
• Transparent
• Crystalline structure
4. Position of Lens
• Located between the iris and
the vitreous
– at the pupillary area
– in the saucer shaped
depression k/a patellar fossa
5. Anatomical Relation
Anterior:
– AC of the eye through the
pupillary aperture, and
– with the posterior surface of the
iris
Lateral:
– PC of the eye and to the zonules
through ciliary processes
~3 mm
6. Anatomical Relation
Posterior:
• Vitreous, separated by slit like
Retrolental/Berger’s space
filled with aqueous and
attached to the posterior
surface in a circular fashion by
ligamentum
hyaloideocapsulare (Wiegert’s
ligament)
~3 mm
7. • Derived from surface ectoderm
• First apparent at about 25 days
of gestation as a disc-shaped
thickening of surface epithelial
cells over the optic vesicle
Development of Lens
8. Lens Placode
• The cells of surface ectoderm
overlying the optic vesicles
become columnar at about 27th
day of gestation
• This area of thickened cells is
called lens plate or lens placode
9. Lens Pit
• Appears at 29th day of gestation as
a small indentation inferior to the
centre of lens plate
• Lens Pit deepens by a process of
cellular multiplication and
invaginates
10. Lens Vesicle: 33rd day
• Invagination of lens pit continues
• Resultant sphere is a single layer of cuboidal cells
encased within a basement membrane (lens capsule),
called a lens vesicle
11. Primary Lens Fibers and Embryonic
Nucleus
• Posterior cells of lens vesicles rapidly elongate obliterating
the lumen of the cavity
• By 45th day of gestation the lumen is completely
obliterated and the cells are called Primary lens fibers
• Constitute Embryonic nucleus
12. Developing Lens Epithelium
• Cells of anterior lens vesicle still remain cuboidal and
form Lens epithelium
• Subsequent growth and differentiation originates
from lens epithelium
13. Secondary lens Fibers
• Pre-equatorial cells of lens
– epithelium retain their mitotic
activity throughout life
– form the Secondary lens fibers
– Starts from the 7th week of
gestation
14. Secondary lens Fibers
• Anterior aspect of fibers
– anterior pole and
• Posterior aspect
– posterior pole of the lens
• Subsequently get displaced and
meet on the vertical planes, the
Lens sutures
15. Lens Suture and Fetal Nucleus
• Formed only during fetal life
• Fetal nucleus
– secondary lens fibers formed
between 2nd to 8th months of
gestation
• As secondary fibers are added,
the sutures become more
complex and dendriform
• Erect Y anteriorly and inverted
Y posteriorly
17. Tunica Vasculosa Lentis
• A vascular mesenchymal layer
– Posterior pupillary membrane,
• a network covering posterior surface
of the lens capsule
• Hyaloid artery
– Anterior pupillary membrane,
• a network of capillaries derived
from Ciliary vein
– Anastomosis occurs At 1st month
of gestation
18. Clinical Significance of Vasculosa lentis
Remnant of the Anterior Pupillary
Membrane Includes
Persistant Pupillary Membrane
• visible in young patients as pupillary
strands
• Minimal visual obscuration
Persistent pupillary membrane
Epicapsular star
EPICAPSULAR STAR
Star shaped distribution of tiny
golden flecks on central anterior lens
capsule
19. Remnant of Posterior Pupillary Membrane
Mittendorf Dot
• Small dense white spot located mostly inferonasally to
the posterior pole of lens
Mittendorf dot
20. Persistent Fetal Vasculature
• Rare,unilateral in 90% cases
• k/a Persistent hyperplastic
primary vitreous (PHPV)
• White fibrous, retrolental tissue in
association with posterior cortical
opacification
• Presents with white pupillary
reflex
21. Developmental Anomalies of the Lens
1. Lenticonus/Lentiglobus
2. Coloboma
3. Microphakia/
Microspherophakia
22. Lenticonus
Posterior
• Posterior axial bulge
• Unilateral - usually sporadic
• Bilateral - familial or in Lowe
syndrome, Alports syndrome
Anterior
• Anterior axial bulge
• Associated with Alport syndrome
23. • Hemispherical protrusion of the lens
• Localized deformation of the lens surface is spherical
• Symptoms include myopia and reduced visual acuity
• Appear as an "oil droplet” on retro illumination
Lentiglobus
24. Lens Coloboma
Primary:
• Wedge shaped defect or
indentation of the lens in
periphery. It mostly
occurs as an isolated
anomaly
Secondary:
• A flattening or indentation
of the lens periphery
caused by lack of ciliary
body or zonular
development
• These are typically inferior
and may be associated
with colobomas of uvea
25. • Lens small in diameter and
spherical in shape
• High myopia
• Due to faulty development of
secondary lens fibers
• May be Isolated or associated with
Weill-Marchesani syndrome, Peters
anomaly , Marfan’s syndrome,
Alport syndrome
Microspherophakia
Microphakia–lens is small than
normal diameter
26. Congenital Aphakia
• Very rare
• Complete absence of lens
• May be primary or secondary
• Primary:
– lens placode fails to develop from the surface
ectoderm
– Occurs only with gross malformations like
anophthalmia or microphthalmia
• Secondary:
– More common, developing lens is spontaneously
absorbed
27. Polar cataract:
Small opacities of
the lens capsule &
adjacent cortex on
the anterior or
posterior pole of
the lens
Congenital cataract
28. Small opacifications
of the lens
epithelium and
anterior lens
capsule that spare
the cortex
Capsular Cataract:
29. • Opacities of embryonic
nucleus alone or both
embryonic or fetal
nuclei
• Usually bilateral
Nuclear cataract:
31. • Group of club-shaped
opacities in the
cortex.
• Arranged around the
equator of the lens
like a crown, or
corona
Coronary Cataracts:
32. Blue Dot Cataract:
• Punctate opacities in the
form of rounded bluish
dots
• Lies in the peripheral part
of adolescent nucleus &
deeper layer of the cortex
34. Dimensions
1. Anterior surface of lens:
- radius of 10 mm (8-14 mm)
2. Posterior surface:
- radius of 6 mm (4.5-7.5 mm)
3. Anterior pole:
-3 mm from back of cornea
4. Equatorial diameter:
-birth around ( 6.5mm)
-adult ( 9-10mm)
35. 5. Axial width:
at birth – 3.5-4 mm
of adult – 4.75-5mm
6. Refractive index of lens:
as a whole – 1.39
of nucleus - 1.42
of cortex – 1.38
7. Refractive power: 16-17 D
8. Weight of lens: at birth – 65 mg & at extreme of age –
258 mg
36. 9. Accommodative power:
at birth – 14-16 D
at 25 yrs – 7-8 D
at 50 yrs – 1-2 D
10. Color of lens:
at birth ,of infants, adults – colorless
at about 30 yrs – yellow tinge
old age – amber color
Cortex is softer as compared to nucleus
37. Structure of The Lens
• Lens Capsule
• Anterior Lens
Epithelium
• Lens Fiber
38. Lens capsule
• Thin transparent, collagen membrane
• Surrounds lens completely
• Elastic in nature but contain no any elastic tissue
• Anteriorly secreted by lens epithelium and
posteriorly by basal cells of elongating fibers
40. Clinical Significance
True Exfoliation
• Superficial zonular lamella of the
capsule splits off from the deeper layer
• Exposure to infrared radiation
PsedoExfoliation
• Basement membrane-like
fibrillogranular white material
deposited on the lens, cornea, iris,
anterior hyaloid face, ciliary processes,
zonular fibers and trabecular
meshwork
41. Voissius Ring
• Imprinted iris pigments in the
anterior surface of anterior lens
capsule due to blunt trauma to eye
Radiation Induced Cataract
• Punctate opacities within posterior
lens capsule
• Feathery anterior sub capsular
opacities radiating towards the
equator
Voissius ring
Ionizing radiation
induced catarct
42. Anterior lens Epithelium
• Single layer below the lens capsule
• Formed of cuboidal cells
• Become columnar at equatorial region
43. Anterior lens Epithelium
• Actively dividing and elongating to form the lens fiber
• Metabolically active layer
Posterior lens Epithelium absent because
Used in filling the central cavity of lens vesicle during
development period
44. Zones of lens Epithelium
Central Zone:
• Consists of cuboidal cells & do not mitose
Intermediate zone:
• Consists of comparatively smaller and cylindrical
cells located peripheral to central zone
Germinative zone:
• Consists of columnar cells which are most peripheral
& located just pre-equatorial
• Are actively dividing to form lens fiber
45. Clinical Significance
Anterior Subcapsular Cataract
Metaplasia occurring in the central zone
• Shield cataract in atopic dermatitis
• Glaukomflecken after an attack of acute
angle closure glaucoma
Posterior Capsular Opacification (PCO)
• Migration of equatorial cells toward
posterior capsule
46. Lens Fibers
• Hexagonal in cross-section
• Primary lens fibers are formed from
posterior epithelium during
embryogenesis
• Formed constantly throughout life by
elongation of lens epithelium at equator
from germinative cells
• As the lens fibers are formed
throughout life, these are arranged
compactly as Nucleus & Cortex of the
lens
47. Nucleus
-central part containing the oldest fibers
- Depending upon the period of development different
zones of nucleus are:
– Embryonic nucleus
– Fetal nucleus
– Infantile nucleus
– Adult nucleus
48. Embryonic nucleus –
It is the innermost part of
nucleus ( 3 months of
gestation)
It consists of primary lens
fibers
Fetal nucleus –
lie around the embryonic
nucleus & corresponds to the
lens from 3 months of
gestation till birth
Its fibers meet around sutures
which are anteriorly Y shaped
& posteriorly inverted Y shape
49. • Infantile nucleus : lens
from birth to puberty
• Adult nucleus : lens
fibers formed after
puberty to rest of the
life
51. Zonules of zinn
– Series Of fine fibers passing
between the Ciliary Body and
the Lens
– Hold the lens in position and
Enables the ciliary muscle to
act on lens during
accommodation
– Originates from the basal
lamina of the non pigmented
epithelium of pars plana and
pars plicata of ciliary body
52. Zonules of zinn
• Fibers arise from the non
pigmented epithelium of Ciliary
Body and are distributed
– as the Anterior fibers
– as the Equatorial fibers and
– as Posterior fibers
53. Ectopia lentis
• Displacement of lens from its normal position
• May be congenital, developmental or acquired
• May be dislocated or subluxated
Clinical Significance
55. Ectopia lentis
Developmental
• Deficient development of zonules causes ectopia lentis
in association with other conditions
• Presents with:
– decreased vision
– marked astigmatism
– monocular diplopia
– iridodonesis
Acquired Lens Displacement
Most commonly due to trauma
58. Water
• 66% of the lens wet weight
• Low amount of water to maintain the refractive
index
• Lens dehydration maintained by active sodium pump
• Cortex more hydrated than nucleus
59. Proteins
• 33% of lens wet weight
• Majority in lens fibers
• Two Major groups:
a) Water soluble (80%)
crystallin – alpha(32%), beta(55%) and
gamma(1.5%)
b) Water insoluble: 2 fractions
soluble in urea
insoluble in urea
60. Function of Crystallin
• Refractive function
• Change of shape during cell differentiation
• Stress-resistant & oxidative properties
• Chaperone-like functions
• to prevent insolubilization of heat denatured
proteins
• to facilitate the renaturation of proteins that have
been chemically denaturated
61. Carbohydrates
1. Glucose
Source is aqueous humor
20-120 mg%
2. Fructose
produced from glucose
3. Glycogen
very high in lens
located in the nucleus
4. Inositol
5. Sorbitol
62. Lens Lipids
Cholesterol (50-60%)
Phospholipids - sphingomyelin
Glycolipids
Functions-
• principal constituents of lens cell membrane
• also associated with lens epithelial cell division
64. Electrolytes
• Potassium is the predominant cation. Varying 114-
130 mEQ/kg lens matter
• Sodium concentrates about 10-50% of potassium
concentration between 14-25 mEQ/kg lens matter
• Calcium lowest of all tissue calcium level with a mean
value of 0.14 mg /mg dry weight
• The main anion are chloride, bicarbonate, phosphate
& sulphates
65. Glutathione
• Is a tripeptide compounds
• Content varies form 3.5 - 5.5 mg/g wet weight of lens
• Lens epithelium contains high levels of glutathione
• More than 95% of glutathione is in reduced state
66. Lens Physiology
• Main site – lens epithelium
• Main Aims
1. Maintenance of lens transparency
2. Accommodation
3. Carbohydrate metabolism
4. Regulation of lens electrolyte balance to maintain
the normal hydration of the lens
5. Protection of the lens from oxidative damage
67. Lens Transparency
Normally transmits 80% light energy
Result of:-
1. Single(thin) layer of Epithelial cells
2. Semi permeable lens capsule
3. Highly packed structure of lens fibers (zones of
discontinuity much smaller than the wavelength of
light)
68. 4. Characteristic arrangement of lens protein
5. Pump mechanism of lens fibers(which regulates the
electrolyte and water balance)
6. Avascularity
7. Auto-oxidation (ensuring integrity of membrane
pumps)
69. Accommodation
• The mechanism by which the eye changes focus from
distant to near images
• Produced by a change in lens shape as a result of the
action of the ciliary muscle on the zonular fibers
• Lens- most malleable during childhood & the young
adult years
70. Mechanism of Accommodation in Human
Explained by relaxation theory
In unaccommodated state
- the ciliary muscle relax
- the suspensory ligament is at its greatest tension,
- lens take its flattest curves &
- retina is conjugate with far point
71. In accommodated state
- ciliary muscle is constricted in a sphincter like mode,
- zonules of zinn relaxes
- allows the lens to make a more convex form &
- is conjugate with near point
72. Metabolism
• Lens requires a continuous supply of energy
(ATP) for :
• Active transport of ions & amino acids
• Maintenance of lens dehydration
• And for a continuous protein & GSH synthesis
73. Source of nutrient supply
Is an avascular structure
Takes nutrients from two sources by diffusion
1. Aqueous humour (main source)
2. Vitreous humour
74. Pathway and Energy Production
Anaerobic Glycolysis 80%
2 molecules of net ATP per glucose molecule
TCA Cycle (Aerobic Glycolysis) 3%
36 molecules of net ATP per glucose molecule
25 % of the lens ATP
77. Sorbitol pathway
Glucose +NADPH+H+ Sorbitol +NADP+
Fructose +NADH+H+
Polyol dehydrogenase
Aldolase Reductase
High levels of sorbitol and fructose
Stimulation of HMP shunIncrease in osmotic pressure
Indrawing of waterSwelling of fibers, disruption of cytoskeletal structures
Lens opacification
Sorbitol+NAD+
Glucose +NADPH+NAD+
Fructose +NADP++NADH
78. Diabetes
Juvenile
white punctate or snowflake
posterior or anterior opacities
May mature within few days
Adult
Cortical and subcapsular
opacities
May progress more quickly
than in non-diabetics
79. Galactose Metabolism
Galactose +ATP Galactose-1-phosphate +ADP
UDP Glucose
UDP Galactose +glucose-1-phosphate
UDP glucose
Galactokinase
Galactose-1-phosphate uridyl
transferase
UDP-galactose-4-epimerase
Galactitol
Increased osmolarity
Influx of water Osmotic damage to lens CATARACT
80. Galactosemia is a/w development of B/L opacification
k/a oil droplet central lens opacities
81. Age Related Changes
• Morphological Changes
• Mass & dimension of the lens increases
• Epithelial cells becomes flatter & density decreases
• Cholesterol:phospholipid ratio increases
• Increased light absorbance
• Increased light scatter
• Metabolic Changes
• Decreased proliferative capacity of lens epithelium
• Decreased enzymatic activity (superoxide dismutase
and glucose-6-phosphate DH)
82. • Changes in Crystallin
– Increased insolubility
– loss of gamma-crystallins
– Increased disulfide bonds in gamma-crystallins
• Changes in Plasma Membrane and Cytoskeletal
– loss of hexagonal cross-section
– loss of membrane proteins, lipids and cytoskeletal
proteins
– Increased lens sodium and calcium with subsequent
hydration
83. Cataractogenesis
• Disturbance in transparency of lens leads to its
opacification
• Occurrence of an optical discontinuity in the lens of
such magnitude as to cause a noticeable dispersion
of light
• May be congenital or acquired
84. Age Related Cataract
• Commonest type of cataract
• Usually above 50 years
• Usually bilateral
• Multifactorial
85. Nuclear Sclerosis
Exaggeration of normal
ageing changes
Increased yellowish hue
Cortical Cataract
Involves anterior, posterior or
equatorial cortex
Spokes like opacities
86. Subcapsular Cataract
Anterior Subcapsular
• Lies directly under the lens capsule
• Fibrous metaplasia of lens
epithelium
Posterior Subcapsular
• Lies in front of posterior capsule
• Vacuolated, granular or plaque
like
87. Posterior sub capsular opacities are associated with the use
of topical as well as systemic steroids
Initially posterior subcapsular
Systemic or topical steroids
Central, anterior capsular granules
Chlorpromazine
Drug Induced Cataract
Other drugs
Long-acting miotics
