LENS
description
Transcript of LENS
![Page 1: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/1.jpg)
LENSIt is a highly organized
transparent spheroid structure that has evolved to perform
refraction of the light entering in the eye. It does not posses
nerve, blood vessels or connective tissue.
![Page 2: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/2.jpg)
Anatomy of LENSBiconvex LensDiameter varies from 8.8 to 9.2 (9mm)Lens grow in size continuously throughout life.
Its weight is about 60 mgm at the birth and up-to 250 mgm by 80 years of age.
Antero-posterior thickness changes with accommodation. Thickness is 4.75 – 5 mm (4.5mm) (un-accommodated) in adults.
Circumference is known as equator
![Page 3: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/3.jpg)
Anatomy of LENS
Lens is suspended in eye by Zonules which are inserted on anterior surface and equatorial lens capsule and attached to ciliary body(Pars Plicata- Ciliary Processes) .
Zonular fibres are series of fibrillin rich fibre.
![Page 4: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/4.jpg)
Anatomy of LENS
Histologically lens consists of three major components:
1. Capsule – is a thick collagenese basement membrane which is transparent, elastic acellular envelop, thick at anterior pre-equatorial region (21 micron m), thinnest at the posterior pole (4 micron m). Anterior pole is approximately 14 micron m thick.
![Page 5: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/5.jpg)
Anatomy of LENS 2. Lens Epithelium – It is a single layer of
cells lining the anterior capsule and extends to the equatorial lens bow.
Zone of epithelial cells:a. Central – cells do not actively divide,
they divide under pathological conditions only. b. Pre-equatorial germinal zone : cells
rarely divide.
![Page 6: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/6.jpg)
Anatomy of LENS
C. Germinal zone: constitute of the stem cell population. The newly formed cells from germinal zone are forced into transitional zone where they elongate and differentiate to form mass of the lens. The lens capsule regulate the transport of metabolite, nutrients and electrolytes to the lens fibers.
![Page 7: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/7.jpg)
Anatomy of LENS
3. Lens substance: It constitute the main mass of the lens. It is divided into-
a. Nucleusb. CortexNucleus: consists of(i) Embryonic nucleus (it contains
primary lens fibres that are formed in lens vesicle)
![Page 8: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/8.jpg)
Anatomy of LENS
(ii) Fetal nucleus: it contains embryonic nucleus and all fibres added to the lens before birth (iii) Infantile nucleus: it contains embryonic , fetal nucleus together with all the fibres added up-to the age of 4 years. (iv) Adult nucleus: composed of all fibres added before sexual maturation The nucleus consists of densely compacted lens fibres and higher refractive index than cortex.
![Page 9: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/9.jpg)
April 22, 2023 9
LENS Anatomy
Capsule
Cortex
3
45
6
3 – Adult Nu 4 - Infantile Nu5 – Foetal Nu6 – Embryonic Nu.
![Page 10: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/10.jpg)
Lens Cortex It is located peripherally and is composed
of secondary fibres formed continuously after sexual maturation. It is further
divided into: Deep cortexIntermediate cortexSuperficial cortex
![Page 11: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/11.jpg)
LENS- Crystalline
Lens fibres contain high concentrations of crystalline.
Crystalline represent the major protein of the lens (constitute 90% of total protein content of lens). Crystalline has the following constituents:Alpha Beta and,Gamma
![Page 12: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/12.jpg)
Lens - FunctionsThe lens serves two major
functions:Focusing of visible light rays on the
fovea Preventing damage from ultra-violet
radiation by reaching the retina
![Page 13: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/13.jpg)
Lens – Physiology Lens function and transparency is
dependant on the supply of appropriate nutrient to its various structures. Metabolic needs of a adult lens is met by the aqueous and vitreous.
There is continuous transport of ions into and out of the lens.
![Page 14: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/14.jpg)
Lens – Physiology The transparency is dependent on highly
organized structure of lens, dense packing of crystalline. Avascularity, absence of pigments and optimal hydration.
By act of accommodation it changes focusing power. Accommodation occurs by increasing the curvature of anterior surface thereby changing refractive power of lens.
Light transmission and elasticity of lens decreases with age.
![Page 15: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/15.jpg)
CATARACTAny opacity in the lens or its capsule, whether
developmental or acquired is called cataract.
Developmental opacities are usually partial and stationary, whereas acquired opacities are progressive. They progress until the entire lens is involved, but exceptions are well known in both types.
![Page 16: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/16.jpg)
Classification of Cataract
Classification based on EtiologyClassification based on
MorphologyClassification based on MaturityClassification based on the Age
of onset
![Page 17: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/17.jpg)
Classification based on Etiology
DevelopmentalAcquired
![Page 18: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/18.jpg)
Developmental
HereditaryIntrauterine causeso Rubellao Toxoplasmosiso CMVo Steroids
![Page 19: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/19.jpg)
Acquired Cataract1. Age related (senile)2. Secondary cataract (Chronic Uveitis, ACG)3. Cataract associated with ocular diseases4. Cataract associated with systemic diseases
(pre-senile) (Diabetes, galactosemia etc)5. Traumatic Cataract6. Drug induced cataract (Steroids and others)
![Page 20: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/20.jpg)
Classification based on Morphology
Capsular (Ant and Post)Subcapsular (Ant and Post)NuclearCortical
![Page 21: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/21.jpg)
Classification based on Maturity
ImmatureMatureHypermatureMorgagnian
![Page 22: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/22.jpg)
Classification based on the Age of onset
CongenitalInfantileJuvenilePresenileSenile
![Page 23: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/23.jpg)
Risk Factors for Cataract
SenilitySunlight (specially UV –A and UV-B component)Severe Diarrheal dehydrationVitamin A,C, E deficiencyDiabetesSmokingCorticosteroidsGenetic
![Page 24: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/24.jpg)
Pathogenesis of Cataract Caused by degeneration and opacification of
existing lens fibres, formation of aberrant fibres or deposition of other material in their place.
Factors causing disturbance of critical intra – and extra-cellular equilibrium of water and electrolyte or deranges the colloid system within the fibres tends to bring about opacification.
![Page 25: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/25.jpg)
Pathogenesis of Cataract
Fibrous metaplasia of fibres (in complicated cataract)
Epithelial cell necrosis (Glaucomflecken)Deposition of abnormal products of
metabolism, drugs or metals.
![Page 26: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/26.jpg)
Pathogenesis of Cataract
Biochemical Processeso Hydrationo Denaturation of Lens Proteinso Sclerosis
![Page 27: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/27.jpg)
Pathogenesis of Cataract
The Changes in the Epithelial Cells and the Capsule
Changes in the Lenticular FibresSclerosis
![Page 28: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/28.jpg)
Symptoms of Cataract1. Blurring of vision2. Frequent change of glasses due to rapid
change in refractive index of the lens 3. Painless, progressive gradual diminution of
vision due to reduction in transparency of the lens
4. Second sight or myopic shift in case of nuclear cataract causing index myopia, improving near vision.
![Page 29: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/29.jpg)
Symptoms of Cataract
5. Loss or marked diminution of vision in bright sunlight or bright light beam in central posterior subcapsular cataract.
6. Monocular diplopia or polyopia in presence of cortical spoke opacities
7. Glare in posterior subcapsular cortical cataract due to increased scattering of light
![Page 30: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/30.jpg)
Symptoms of Cataract
8. Colored haloes around the light as seen in cortical cataract due to irregular refractive index in different parts of the lens.
9. Color shift , reds are accentuated10. Visual field loss, generalized reduction
in sensitivity due to loss of transparency
![Page 31: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/31.jpg)
Disturbances in VisionAppearance of Black SpotsReduction of Visual Fields Uni ocular PolyopiaLenticular MyopiaChanges in Colour values
![Page 32: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/32.jpg)
Differential Diagnosis of painless gradual diminution of vision
Chronic open angle glaucomaMacular degenerationOptic atrophyCorneal dystrophyRetinopathy associated with systemic
disorders (hypertension or diabetes)
![Page 33: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/33.jpg)
AssessmentVisual AcuityDirect Distant Ophthalmoscopy
(Fundal Glow)Light ReflexSlit Lamp Examination
![Page 34: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/34.jpg)
ManagementMedicalSurgical
![Page 35: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/35.jpg)
Medical ManagementRefractionDark Glasses
![Page 36: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/36.jpg)
Surgical Management
IndicationsVisual ImprovementMedical IndicationsCosmetic Indications
![Page 37: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/37.jpg)
Surgical ManagementCouchingIntracapsular Cataract Extraction
(ICCE)Extracapsular Cataract Extraction
(ECCE)Phacoemulsification
![Page 38: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/38.jpg)
Clinical Rotation of 3rd YearSurgical TechniquesComplicationsManagement of complications
![Page 39: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/39.jpg)
Ectopia LentisAquired (Trauma, Large eye ball, High
Myopia)
Hereditary o Marfans Syndromeo Homocystinuriao Weil Marchesani Syndrome
![Page 40: LENS](https://reader036.fdocuments.us/reader036/viewer/2022070500/56816868550346895dded1c2/html5/thumbnails/40.jpg)
Thanks