it is about embryology of the human eye lens and developmental defects with in the lens..

1. EMBRYOLOGY
AND
DEVELOPMENTAL DEFECTS OF LENS
-Dr. T.Anitha

2. EMBRYOLOGY :
• The CNS is developed from the neural groove which invaginates
to form the neural tube(precursor of forebrain) running
longitudinally down the dorsal surface of the embryo.
• At either side from the lateral aspect of neural tube, a thickening
appears at an early stage, called the optic plate, which then grows
outwards as a diverticulum at approximately 25 days of gestation,
called optic vesicles.
.

3. • The proximal part of the
optic vesicles becomes
constricted & elongated to
form the optic stalk.
• As the optic vesicles
enlarge and extend
laterally, they become
closely apposed & adherent
to the surface ectoderm, a
single layer of cuboidal
cells.

4. Lens Placode:
• The ectodermal cells, that overlie the optic vesicles
become columnar at approximately 27 days of gestation.
•This area of thickened cells is called the lens placode.
Growth factors of the bone morphogenetic protein (BMP)
family are required for formation of the lens placode.

5. Lens Pit:
• The lens pit appears at 29 days of gestation as an
indentation (in folding) of the lens placode.
•The lens pit deepens and invaginates to form the
lens vesicle.

6. Lens Vesicle :
• As the lens pit continues to invaginate, the stalk of cells
connecting it to the surface ectoderm degenerates by
programmed cell death (apoptosis), thereby separating the
lens cells from the surface ectoderm.
•The resultant sphere is called the lens vesicle(0.2mm),
formed at 30 weeks of gestation.

7. • At the same time that the lens vesicle is forming, the
optic vesicle is invaginating to form the 2-layered optic
cup.
• The margins of the optic cup grows over upper and
lateral sides of lens to enclose it.
•However, such an overgrowth doesn’t take place on
inferior aspect of lens.

8. • As a result of which ,the wall of the cup shows a
deficiency in the inferior aspect of lens, that extends for
some distance along the inferior surface of optic stalk,
called as choroidal or fetal fissure.

10. Primary Lens Fibers and the Embryonic Nucleus :
• The cells in the posterior layer of the lens vesicle stop
dividing and begin to elongate.
•As they elongate, they begin to fill the lumen of the lens
vesicle.
• At approximately 40 days of gestation, the
lumen of the lens vesicle is obliterated. The elongated
cells are called the primary lens fibers.

11. • As the fibre cells mature, their nuclei and the other
membrane bound organelles undergo degradation.
•The primary lens fibers make up the embryonic nucleus
that will ultimately occupy the central part of the adult
lens.

12. •The cells of the anterior lens vesicle remain as a
monolayer of cuboidal cells, the lens epithelium.
•Subsequent growth of the lens is due to proliferation
within the epithelium.
•The lens capsule develops as a basement membrane
elaborated by the lens epithelium anteriorly and by lens
fibers posteriorly.

13. Secondary Lens Fibers:
• After they proliferate, the epithelial cells near the lens
equator elongate to form secondary lens fibers.
•The anterior aspect of each developing lens fiber extends
anteriorly beneath the lens epithelium, toward the anterior
pole of the lens.

14. •The posterior aspect of each developing lens fiber
extends posteriorly along the capsule, toward the
posterior pole of the lens.
•In this manner, new lens fibers are continually formed,
layer upon layer.
•The secondary lens fibers formed between 2 and 8
months of gestation make up the fetal nucleus.

15. Lens Sutures and the Fetal Nucleus :
• As lens fibers grow anteriorly and posteriorly, a pattern
emerges where the ends of the fibers meet and
interdigitate with the ends of fibers arising on the opposite
side of the lens, near the anterior and posterior poles.
•These patterns of cell association are known as sutures.

16. • Y-shaped sutures are recognizable at approximately 8
weeks of gestation, with an erect Y suture appearing
anteriorly and an inverted Y-suture posteriorly.
• The human lens weighs approximately 90 mg at birth,
and it increases in mass by approximately 2 mg per year
as new fibers form throughout life.

19. Tunica Vasculosa Lentis :
• Around 1 month of gestation, the hyaloid artery, which
enters the eye at the optic nerve ,branches to form a
network of capillaries, the tunica vasculosa lentis, on the
posterior surface of the lens capsule.

20. •These capillaries grow toward the equator of the lens,
where they anastomose with a second network of
capillaries, called the anterior pupillary membrane,
which derives from the ciliary veins and covers the
anterior surface of the lens.

21. • At 9 weeks of gestation, the capillary network
surrounding the lens is fully developed; it disappears by
programmed cell death before birth.
• Sometimes a remnant of the tunica vasculosa lentis
persists as a small opacity or strand, called a Mittendorf
dot, on the posterior aspect of the lens.

22. Congenital Anomalies and Abnormalities :
Anomalies of the eye and orbit are apparent on
ultrasonography before birth.
A)Congenital Aphakia :
• Lens is absent.
• 2 types of congenital aphakia
-primary aphakia  the lens placode fails to form
from the surface ectoderm in the developing embryo.
-secondary aphakia mc type, the developing lens
spontaneously absorbed.

23. B)Lenticonus and Lentiglobus :
•Lenticonus is a localized, cone-shaped deformation of the
anterior or posterior lens surface.
•Posterior lenticonus is more common than anterior
lenticonus & is usually unilateral.
•Anterior lenticonus is often bilateral and may be
associated with Alport syndrome.

25. • Posterior lentiglobus is more common than anterior
lentiglobus and is often associated with posterior polar
opacities.
• Retinoscopy through the center of the lens reveals a
distorted and myopic reflex in both lenticonus and
lentiglobus.
•These deformations can also be seen in the red reflex,
where, by retro illumination, they appear as an “oil
droplet.”

26. Fig: Posterior lenticonus/lentiglobus. (A) Early clear
defect in central posterior capsule(oil droplet) and (B)
early opacification of central defect. (C), Ultrasound
biomicroscopy of advanced posterior lenticonus

27. C)Lens Coloboma:
• Anomaly of lens shape.
• -Primary coloboma  wedge-shaped defect due to
indentation of the lens periphery.
-Secondary coloboma  lack of ciliary body or zonular
development.
• Located inferonasally.
• Associated with colobomas of the iris, optic nerve, or
retina.

28. D)Mittendorf Dot:
•Mittendorf dot is a common anomaly observed in many
healthy eyes.
•A small, dense white spot generally located inferonasal to
the posterior pole of the lens.
•Remnant of the posterior pupillary membrane of the
tunica vasculosa lentis.

29. •It marks the place where the hyaloid artery came into
contact with the posterior surface of the lens in utero.
•Sometimes a Mittendorf dot is associated with a fibrous
tail or remnant of the hyaloid artery projecting into the
vitreous body.

30. E)Epicapsular Star:
• Another very common remnant of the tunica vasculosa
lentis is an epicapsular star.
• As its name suggests, this anomaly is a star-shaped
distribution of tiny brown or golden flecks on the central
anterior lens capsule.
• It may be unilateral or bilateral

31. F)Peters Anomaly :
• Known as anterior segment dysgenesis syndrome or
neurocristopathy or mesodermal dysgenesis.
• Characterized by a central or paracentral corneal opacity
(leukoma)associated with thinning or absence of adjacent
endothelium and Descemet membrane.
-Peters anomaly type 1  iris strands adherent to the
cornea.
-Peters anomaly type 2  the lens is adherent to the
posterior cornea.

32. • Anomaly is due to absence of separation of lens vesicle
from surface ectoderm(future corneal epithelium).
• associated with mutations in or deletion of 1 allele of the
genes normally involved in anterior segment development,
including the transcription factors PAX6, PITX2, and
FOXC1.

33. • Patients with Peters anomaly type 2 may also display
the following lens anomalies:
anterior cortical or polar cataract.
a misshapen lens displaced anteriorly into pupillary
space and the anterior chamber.
Microspherophakia.

34. Fig: Cloudy cornea in both
eyes
A) B)
C) D)
Fig: Anterior
segment OCT
showing
corneolenticular
& iridocorneal
adhesions

35. G)Microspherophakia :
• Lens is small in diameter and spherical. The spherical
shape of the lens results in increased refractive power, &
eye will be highly myopic.
• Due to faulty development of the secondary lens fibers
during embryogenesis.

36. • The spherical lens can block the pupil, causing secondary
angle-closure glaucoma.
• Cycloplegics are the medical treatment of choice to
break an attack of angle-closure glaucoma.
• A laser iridotomy may also be useful in relieving angle
closure.
 Inherited as an autosomal recessive trait.

37. •Associated with
Weill-Marchesani syndrome
Peters anomaly
Marfan syndrome
Alport syndrome
Lowe syndrome
congenital rubella.

39. H)Congenital Cataract :
• present at birth or that develop within the first year of
life.
• occur in 1 of every 2000 live births.
• unilateral or bilateral.
• Metabolic diseases tend to be more commonly
associated with bilateral cataracts.

40. • Congenital cataracts occur in a variety of
morphologic configurations, including
a. lamellar
b. polar
c. sutural
d. coronary
e. cerulean
f. nuclear
g. capsular
h. complete
i. membranous

42. 1)Lamellar cataract:
• Most common type.
• Bilateral and symmetric.
• Inherited as an autosomal dominant trait.
• Clinically, the cataract is visible as an opacified layer that
surrounds a clearer center and is itself surrounded by a
layer of clear cortex.

43. • Arcuate opacities within the cortex straddle the equator
of the lamellar cataract; these horse shoe-shaped
opacities are called riders.

44. 2)Polar cataract :
• Opacities involve the subcapsular cortex and capsule of
the anterior or posterior pole of the lens.
• Anterior polar cataracts  small, bilateral, symmetric,
nonprogressive opacities that do not impair vision.
• Posterior polar cataracts  associated with more
profound decrease in vision than, because they tend to be
larger and are positioned closer to the nodal point of the
eye.

46. 3)Sutural cataract :
• Opacification of the Y-sutures of the fetal nucleus.
• Does not impair vision.
• Bilateral and symmetric .

47. 4)Coronary cataract :
• Club-shaped cortical opacities that are arranged around
the equator of the lens like a crown, or corona.
• Seen when the pupil is dilated.
• Do not affect visual acuity.

48. 5)Cerulean cataract :
•Also known as blue-dot cataracts.
• Small bluish opacities located in the lens cortex.
• Non progressive and usually do not cause visual
symptoms.

49. 6)Nuclear cataract :
•Opacities of the embryonic nucleus alone or of both
embryonic and fetal nuclei.
• Usually bilateral.
• Associated with microphthalmia.

50. 7)Capsular cataract :
• Small opacifications of lens epithelium and anterior lens
capsule.
• Do not affect vision.

51. 8)Complete cataract :
• All of the lens fibers are opacified.
• The red reflex is completely obscured.
• The retina cannot be seen with either direct or indirect
ophthalmoscopy.
• Complete cataracts may be unilateral or bilateral, and
they cause profound visual impairment.

52. 9)Membranous cataract:
• Occur when lens proteins are resorbed from either an
intact or a traumatized lens.
•This allows the anterior and posterior lens capsules to
fuse into a dense white membrane, causing significant
visual disability

53. 10)Rubella cataract:
• Maternal infection with the rubella virus, an RNA
togavirus, can cause fetal damage, in first trimester of
pregnancy.
• Cataracts resulting from congenital rubella syndrome are
characterized by pearly white nuclear opacities.
• Other ocular manifestations of CRS include diffuse
pigmentary retinopathy, microphthalmos, glaucoma, and
transient or permanent corneal clouding.

54. Developmental Defects of lens:
a)Ectopia Lentis:
• Displacement of the lens.
• A subluxated lens is partially displaced from its normal
position but remains in the pupillary area.
•A dislocated, lens is completely displaced from the pupil,
implying separation of all zonular attachments.

55. • Clinical features:
decreased vision,
marked astigmatism,
 monocular diplopia,
iridodonesis (tremulous iris).
• Dislocation of lens into the anterior chamber- pupillary
block and angle-closure glaucoma.
• Dislocation into the vitreous cavity - has no adverse
sequelae.

57. b)Marfan syndrome:
• Heritable disorder with ocular, cardiovascular, and
skeletal manifestations.
• Autosomal dominant trait.
• Caused by mutations in the fibrillin gene on chromosome
15.
• 50%-80% of patients with Marfan syndrome exhibit
ectopia lentis .

58. •Other ocular abnormalities associated with Marfan
syndrome include
 axial myopia
retinal detachment.
 Open-angle glaucoma(dislocation into anterior
chamber).
Amblyopia may develop in children(if RE remains
uncorrected in childhood).
•The lens subluxation tends to be bilateral, symmetric
usually superior and temporal.

59. Fig: Superio-temporal subluxation of lens in
Marfans syndrome

60. c)Homocystinuria:
• Inborn error of methionine metabolism,transmitted in an
autosomal recessive pattern.
•Serum levels of homocysteine and methionine are
elevated.
•Lens dislocation tends to be bilateral and symmetric. The
dislocation appears in infancy in approximately 30% of
affected individuals.

61. • Lens subluxated inferiorly and nasally.
• Infants with homocystinuria treated with
-low methionine
-high cysteine diet
-vitamin supplementation with the coenzyme pyridoxine
(vitamin B6) therapy
reduced incidence of ectopia lentis, in some patients.

62. Fig: inferio-nasal subluxation of lens in
homocystinuria.

63. Hyperlysinemia:
• Inborn error of metabolism of the amino acid lysine, is
associated with ectopia lentis.
•Affected individuals also show cognitive impairment and
muscular hypotony.

64. Ectopia Lentis et Pupillae:
• Autosomal recessive disorder.
•The lens and the pupil are displaced in opposite
directions.
•The pupil is irregular, usually slit shaped.
•The dislocated lens may bisect the pupil or may be
completely absent from the pupillary space.

65. Associated ocular anomalies include :
Axial myopia
Retinal detachment
Enlarged corneal diameter
Cataract.

66. Fig: Ectopia lentis et pupillae

67. Persistent Fetal Vasculature:
• Also known as persistent hyperplastic primary vitreous
(PHPV).
• Nonhereditary ocular malformation that frequently
involves the lens.
• A white, fibrous retrolental tissue is present, often in
association with posterior cortical opacification.

68. Other abnormalities associated with PFV
include:
Elongated ciliary processes
Prominent radial iris vessels
Persistent hyaloid artery.

69. Monoyer chart. Reading
upwards on both ends
(ignoring the last line), the
name "Ferdinand Monoyer"
can be seen.
French ophthalmologist, known for
introducing the DIOPTRE in 1872.
Do you know who is the inventor of basis of model of eye
examination(visual acuity)? He is Ferdinand Monoyer.