More Related Content
Similar to ANATOMY & EMBRYOLOGY OF LENS- Dr. Anuj Pawar.pptx
Similar to ANATOMY & EMBRYOLOGY OF LENS- Dr. Anuj Pawar.pptx (20)
Recently uploaded
Recently uploaded (20)
ANATOMY & EMBRYOLOGY OF LENS- Dr. Anuj Pawar.pptx
- 1. DR. ANUJ PAWAR DEPT OF OPHTHALMOLOGY, J.L.N. HOSPITAL, BHILAI C.G.
- 2. Lens Lens (Lent-Latin word – lentil - similar shape) Transparent, avascular, biconvex, elliptical, crystalline body Maintain clarity To refract light To provide accommodation
- 3. Embryogenesis of Lens Starts at 22nd day of gestation Outgrowth from Prosencephalon - optic vesicle forms and enlarges to oppose with ectoderm Surface ectoderm- Lens Placode and surro. Ectoderm Mesoderm surro. Optic vesicle Visceral mesoderm of maxillary process
- 4. Lens plate formation(27-29 days) Lens pit Lens plate 27th –33rd day of gestation – lens placode or lens plate is formed, then lens vesicle is formed
- 5. Lens vesicle formation 30 days Forming lens vesicle Ectoderm Lens vesicle completed 33 days PAX6 SOX 2 FOR LENS VESCILE FORMATION
- 7. Embryonic nucleus formation (app. 40 days) Primary lens fibers (app. 35 days)
- 8. ◦ Primary lens fibers -The cells of the posterior wall of the lens vesicle rapidly elongate and get filled with proteins called crystalline, which make them transparent. The bases of these densely packed cells. ◦ Secondary lens fibers - The equatorial cells of the anterior epithelium remain active throughout the life Fetal Nucleus : 3rd to 8th month of gestation. Infantile Nucleus : Last week of Gestation till puberty Adult Nucleus : After Puberty Cortex : recently formed superficial sec lens fibers ◦ Lens capsule : True LC- membranous , noncellular envelope surro. Lens True Basement memb. – basal laminae material deposited by lens Epi. On ext . Aspect. ◦ Lens zonules
- 10. 35 – 40th day posterior epithelial cells º columnar cells º primary lens fiber (embryonic nucleus) 49th day (7th wk.) cells along the equator multiply & elongate to form secondary lens fibers (fetal nucleus)
- 12. Changes in Developing lens ◦ During initial development the lens is elongated antero-posteriorly. ◦ It is nearly spherical, soft and reddish in tint at the 18-24 mm stage. ◦ As more and more secondary lens fibers are added to the equator the lens becomes ellipsoid, a trend that continues till birth. ◦ At birth, the lens is almost spheroidal, being slightly wider in the equatorial plane. The antero- posterior diameter of lens at birth is nearly that of an adult, but its equatorial diameter is about 2/3rd of that reached in the adult.
- 13. Tunica Vasculosa Lentis 1st month of gestation- hyaloid artery gives branch to the post. surface of lens(post. Vascular artery - PVA) - (Mittendorf ’s dot)
- 14. PVA anastomoses with choroidal vein (capsulopupillary portion) It anastomose with long ciliary artery and form anterior vascular capsule (9thwk.) - (persistance pupillary membrane)
- 15. SUMMARY Begins very early in embryogenesis Days 25- optic vesicle forms from forebrain Days 27- lens plate Days 29- lens pit Day 33- lens vesicle Day 35- primary lens fiber
- 16. 7 weeks-Secondary lens fibers Develop between 2-8 months: fetal Nucleus 8 weeks- y shaped suture 3rd month - Zonular fibers are secreted by the ciliary epithelium
- 18. Coloboma Coloboma of iris Coloboma of choroid Ocular associations
- 20. Lenticonus Posterior Anterior • Posterior axial bulge • Bilateral -Lowe syndrome Asso. • Congenital cat., Mental retard. • Renal tubular dysfunction • Anterior axial bulge • Alport syndrome Asso. SNHL, RF Dot & Fleck RTNP macula
- 21. Small lens • • • Microphakia Microspherophakia • Small diameter Systemic association - Lowe syndrome • Small diameter and spherical Ectopia lentis, Glaucoma,Myopic Systemic association - Weill-Marchesani syndrome
- 22. Ectopia lentis SIMPLE( pupil may be normal) Pupil may be displaced in opposite direction (ectopia lentis et pupillae)
- 26. ANATOMY
- 27. Introduction Lens is a biconvex, transparent crystalline structure. Adds 15-20 D of plus power to 43D created by cornea.(R.I :1.386-1.41) Avascular with no lymphatics, no innervation Accommodative power and color varies with the age Continually growing throughout life
- 28. Second major refracting unit of human eye At birth, Weight:65- 90 mg Equatorial Diameter: 6.4 mm AP length: 3.5 mm Adult lens, Weight-255 mg Equatorial Diameter: 9 - 10 mm AP length: 4.5-5mm Radius of curvature: Ant surface-10 mm Post. surface -6mm
- 29. Morphology of the Lens Biconvex its more convex posteriorly Anterior surface – center is known as anterior pole Posterior surface- center portion is called posterior pole Optical axis (ap-pp) Equator (meeting point of as-ps)
- 30. Position of the Lens Located between the iris and the viterous at the pupillary area in saucer shaped Patellar fossa and attached with vitreous by ligamentum hyaloideo- capsulare
- 31. Color of lens: ◦ Transparent – Infant ◦ Colorless- Young adults ◦ Yellowish- 30+ ◦ Amber – 60+ ◦ As a result of absorbing UV-B to protect the retina from UV radiation’s accumulated effects. ◦ This increasing yellowness reduces illumination. This effect is also combined with a reduced sensitivity of the photoreceptors
- 32. 6 months 8 yrs 12 yrs 25 yrs 47 yrs 60 yrs 70 yrs 82 yrs 91 yrs 70 yrs brown NS 60 yrs with Cortical cataract Mixed NS + cortical
- 33. Structure of Lens 1. Capsule 2. Epithelium 3. Cortex,nucleus
- 36. Structure Of The Lens: Capsule: Elastic, transparent basement membrane surrounding the lens completely created by epithelial cells anteriorly & cortical fibers posteriorly Thickest near the equator and thinnest at posterior pole Thickest basement membrane in the body. composed of glycoprotein associated Type IV collagen contains Heparan Sulphate (<1%) maintains capsular clarity
- 37. Capsule of the Lens Basement membrane of the lens epithelium & thickest in the body Elastic and transparent and are arranged in lamellae – type IV collagen Along the equator – pericapsular membrane (zonular lamellae)
- 38. Functions: acts as a barrier in keeping back the vitreous as a barrier against fluorescein, bacteria, and growth factors a source of antiangiogenesis factors
- 39. Anterior Cell Epithelium : Single layer of cuboidal cells beneath the anterior capsule metabolic capacity- to carry out all normal cell activities to generate sufficient ATP to meet the energy needs At Equatorial- Columnar cells- Actively Dividing to form new lens fibers throughout the life. NO posterior lens epithelium – Used up in filling central cavity of lens
- 40. 3 zones a) central- cubical cells, stable, no mitosis b)intermediate- cylindrical c) germinative- columnar, forms lens fiber
- 42. Lens Fibers Highly organized concentric shells – Hexagonal shape Ant. – Everted Y shaped, Post.- Inverted Y shaped Little extra cellular space, InterDigitations are less complicated in Superficial zone of lens Moulding of lens during Accommodation 2 major components: crystallin 90% & cytoskeleton Lens fibres are formed throughout the life Stratification
- 43. Zonule(suspensory Ligament) Series Of Fine Fibres Passing Between The Ciliary Body And The Lens. Transmit The Force From Ciliary Body To The Lens In Unaccomodated Eye. Force Is Relaxed During Accommodation.
- 44. ◦ A) Nucleus: Central- Oldest fibers ◦ Embryonic – Innermost ◦ Size: Embryonic & Fetal- Constant ◦ Adult – Increases ◦ B) Cortex: peripheral part lies just outside nucleus ( Youngest Fibers)
- 45. ON BIOMICROSCOPIC Examination: 1. Capsule: 2. Superficial cortex : C1α- 1ST Cortical clear zone C1 β – 1st Disjunction zone C2: 2nd cortical clear Deep cortex: C3- Bright light Scattered C4- clear zone 3. Nucleus: pre natal part of lens, central part- lacks scattering of light i.e. Embryonic nucleus
- 46. Surgical Anatomy: ◦ Central hard ◦ Epi nucleus plate ◦ Cortex ◦ Capsule ◦ GRADES: I- White/ Greenish yellow ◦ II- Yellow ◦ III- Amber ◦ IV- Brown ◦
- 47. THANK YOU.
Editor's Notes
- PAX6 SOX 2 FOR LENS VESCILE FORMATION