department of ophthalmology tvmc. embryology and congenital anomalies of lens
TRANSCRIPT
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DEPARTMENT OF OPHTHALMOLOGY
TVMC
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EMBRYOLOGY AND
CONGENITAL ANOMALIES
OF LENS
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EMBRYOLOGY
The eye lens develops from the SURFACE ECTODERM
From neural tube arises the primary brain vesicles representing the prosencephalon ,mesencephalon & rhombencephalon
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3 rd week of IUL – Optic groove appears
4th week of IUL – Optic vesicle develops & lens plate appears
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Optic vesicle grows laterally & comes in contact with the surface ectoderm
Surface ectoderm overlying the optic vesicle thickens to form LENS PLACODE
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Surface ectoderm sinks below & is converted into lens vesicle
The lens vesicle seperates from surface ectoderm at 33rd day of IUL
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LENS PLACODE
LENS PIT
LENS VESICLE
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FORMATION OF LENS FIBRES
Primary lens fibres: Cells of the posterior wall of lens vesicle elongateCavity of the lens vesicle is obliteratedThis elongated posterior wall cells form the primary lens fibresFormation completes in 3rd month of IUL and
this compact core of lens is called as EMBRYONIC NUCLEUS
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Secondary lens fibres
Now the cells of the anterior epithelium which are active throught life divide continuously .
This forms the SECONDARY LENS FIBRES which give a lamellated appearance on cross section as the cells are laic concentrically
Depending on the age of fibres , the secondary lens fibres are called as:
o FETAL NUCLEUS – 3rd to 8th montho INFANTILE NUCLEUS- till pubertyo ADULT NUCLEUS- after puberty
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CONGENITAL ANOMALIES OF THE LENS
Coloboma of the lensCongenital ectopia lentisCongenital cataractLenticonusMicrospherophakia
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COLOBOMA OF LENS
Defective development of part of suspensory ligament
Notch shaped defect in the lens, usually the inferior margin
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CONGENITAL CATARACT
Opacity of lens since birthOccurs due to
disturbance of lens fibre formation
It is limited to the embryonic or foetal nucleus
Persistance of hyaloid arterial system also leads to cataract
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CAUSES OF CONGENITAL CATARACT
Hereditary 1/3 , dominant inheritanceInfections- rubella , toxoplasma, CMVMalnutrition Drugs- corticosteroids ,thalidomideRadiation exposureFoetal anoxia, galactosemia, myotonia
dystrophica, lowe’s syndrome, congenital icthyosis
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CONGENITAL CATARACT
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ECTOPIA LENTISCongenital dislocation or
subluxation of the lensSUBLUXATION- partial
dislocation of lensDISLOCATION – complete
displacement of lens.Causes: marfan’s
syndrome, ehler’s danlos syndrome, homocysteinuria, weil marchesani syndrome
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LENTICONUS
Abnormal curvature of the lens leading to a conical surface
More common posteriorly than anterior surface of the lens
Posterior lenticonus is seen in alport’s syndrome
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MICROSPHEROPHAKIA
Frequently associated with weil marchesani syndrome
In this condition the lens is spherical in shape & small in size
Spherophakia- spherical lensMicrophakia- small lens.
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THANK YOU
Presented by
Vani Narayani.K , 3rd yr MBBS