Lens PDF

Lens It's Elastic, Transparent, Avascular & Biconvex, No nerve supply, Asymmetrical Which is suspended in its place by the suspensory ligament (zonule) (N.B) 1- its elastic in nature but it gradually lose it's elasticity with age 2- Its only intraocular struc...

Lens It's Elastic, Transparent, Avascular & Biconvex, No nerve supply, Asymmetrical Which is suspended in its place by the suspensory ligament (zonule) (N.B) 1- its elastic in nature but it gradually lose it's elasticity with age 2- Its only intraocular structure which grows throughout life 3- The lens develop from surface ectoderm  Gross anatomy Site: - Anteriorly: - iris Posteriorly: - vitreous humor Shape :- [email protected] 1 WWW. MD.LY  -Anterior surface :- less convex , it's center is called anterior pole -Posterior surface :- more convex ,it's center called posterior pole -Equator :- it's rounded edge of lens (attached to the zonule ) Equatorial diameter: - 9mm -Axis :-it's line which connect anterior &posterior pole of lens It's length 4mm Color: - young >>> Transparent Old >>> Grayish Consistency: - young >>> soft Adult >>> hard Refractive index :- 1.40 (cortex = 1.38 , nucleus = 1.42) Refractive power :- 18 D without accommodation. N.B Refractory power of eye = Refractory power of (cornea + lens) Refractory power of eye = (42D + 18D)  Refractory power of eye = 60D  Minute anatomy 1-Capsule [email protected] 2 WWW. MD.LY  -High elastic (for accommodation) -secreted by anterior sub capsular epithelium -Thickness: - anterior capsule > posterior capsule Equator > central part -Function:- 1-Accommodation 2- Protection: - of lens fiber from aqueous enzymes 3- Semi permeable membrane (nutrition IN & waste Product OUT) 2- Sub capsular epithelium -Line capsule ( anteriorly & at the equator )(posterior surface acellular) -Function :- 1-Anterior cells secrete the capsule 2- Equator cells secrete the lens fibers 3- Lens fibers -Superficial lens fiber: - peripheral, new, soft, lens fibers (cortex) -Deep lens fiber: - central, older, hard, lens fiber (nucleus)  Nutrition Before birth: - Hyaloid artery After birth: - diffusion from aqueous  Composition Water: - 65% Protein: - 34 Minerals: - 1%  Function 1- One of refractive media of the eye 2-Protect the retina from U.V rays 3- Accommodation What is accommodation?  Definition :- It's the ability of the eye to change its diopteric power to see at different distance clear  Mechanism :- Contraction of ciliary muscle (circular muscle ) >>> relaxation of zonule >>> increase curvature (become spherical) of lens & increase power of the lens N.B 1- In case of Aphakia (loss of lens in papillary area ) >>> no accommodation 2- Accommodative power decrease with age ,and totally lost by age of 60 years old [email protected] 3 WWW. MD.LY [email protected] 4 WWW. MD.LY  Cataract Definition: - It's lens opacification  Classification :- A- According to Cause 1- Congenital & developmental 2- Acquired (Senile, Traumatic, Complicated) B- According to Site:- 1-Capsular: - anterior or posterior 2-Subcapsular: - anterior or posterior 3-Cortical: - anterior or posterior 4- Nuclear C- According to Age:- 1- Soft cataract: - before 25 2- Hard cataract: - after 25 [email protected] 5 WWW. MD.LY  Congenital cataract ((Developmental cataract)) It's lens opacification at birth or shortly after birth [email protected] 6 WWW. MD.LY   Causes :- ((GHIM)) 1- Hereditary (most common cause)(AD) but may be (AR or X-Linked) 2- Myotonic dystrophy, Marfan syndrome, Down syndrome (occur in 5% of patient) 3- Maternal malnutrition 4- Maternal Drug Ingestion: - Corticosteroids, Thalidomide 5- Intra-uterine infection: - rubella (occur in 15% of patient )(1st trimester WHY?) , toxoplasmosis , cytomegalovirus , herpes simplex 6- Deficient oxygenation (Hypoxia) due to sever placental hemorrhage 7- Metabolic Galactosemia, Homocystinuria. Wilson disease, Hypocalcaemia e.g. Hypoparathyroidism  Characteristic :- 1- Usually bilateral 2- Usually stationary 3- Usually associated with other congenital anomaly 4- May be familial (AD) or non familial.  Types :- 1- Anterior polar 2- Posterior polar 3- Zonular 4-Total 5- Blue dot (punctuate) 6 -Coronary  Clinical picture Symptoms :- (given by mother) 1- Leukocoria (white pupil) 2- Defective vision.(depend on size & position of opacity Signs:-opacity of the lens ((one of previous types seen)).  Investigation 1-Fundus examination: - ophthalmoscope (To exclude Retinoblastoma) [email protected] 7 WWW. MD.LY 2-Visual Evoked Potential ((VEP)): - recording electrical activity of the visual cortex in response to light, which used for testing of visual acuity in young children with opacities of ocular media 3-Laboratory test:- Urine: - Galactosemia Blood: - TORCH titer, serum Calcium, phosphorous.  Complication Unilateral Amblyopia & squint Bilateral Nystagmus (as opacity interferes with foveal development) Mental retardation  Treatment 1- (Irrigation – aspiration) Principle: - Through limbal incision , anterior capsulotomy is done , this followed by aspiration of lens matter with simultaneous irrigation with saline using double way canula. Disadvantage: - posterior capsule opacity 2- Lensectomy Principle:-In which the lens is removed Advantage: - no posterior capsule opacity Disadvantage: - increase risk of retinal detachment  Visual rehabilitation (Treat refractory error) -Depend on age and laterality of aphakia 1- Glasses Useful for older children with bilateral aphakia but not for unilateral aphakia because of associated anisometropia & aniseikonia. Disadvantage:- Heavy ,Constriction of visual field , Unpleasant appearance 2- Contact lenses Can use for unilateral & bilateral aphakia, cosmetic Disadvantage: - it's complication (corneal ulcer), difficult in insertion &remove 3- IOL implantation. (At 2-3 year old) [email protected] 8 WWW. MD.LY  Senile Cataract Most common cataract  Characterized by Bilateral slowly progressive lens opacity affecting old people & not suffering from local or systemic disease  Incidence Age: - above 50 years Sex:-equal in males & female Side: - bilateral (but one eye is affected before other) Hereditary: - may be positive  Types 1-Cortical (75%) 2-Nuclear (20) 3-Corticonuclear (Total) (5%)  Etiology :- (( unknown )) But maybe due to:- 1-U.V rays 2- Smoking, alcohol 3- Decrease of Vit C, Glutathione  Symptoms of cataract in general 1- Gradual painless loss of vision 2- Fixed Musca (fixed dark spots in visual field) 3-Uniocular diplopia 4- Colored haloes around light 5-Defective vision A- defective night vision: - in cortical cataract (peripheral opacity) B-defective day vision:- in nuclear cataract (central opacity) C-defective far vision: - in nuclear cataract (index myopia ) D-defective near vision: - immature cortical cataract (index hypermetropia) 1- Senile cortical cataract  Stages 1-Immature stage (the lens is not totally opaque) 2-Mature stage (the lens is totally opaque) 3-Hypermature stage (the lens loss water & become shrink) [email protected] 9 WWW. MD.LY  Stage Immature Mature Hypermature Symptoms Vision Decrease of vision Decrease of vision Decrease of vision (counter –finger) ( Hand Movement) ( Hand Movement) Signs A/C Normal Normal Deep Iris shadow Present Absence +,- Iris Absence Absence Present tremulous Color of lens Grayish White White Red reflex Present Absent Absent Fundoscopy Present Absent Absent Complication None None 1- Displaced lens 2- Phacotoxic uveitis 3- Phacolytic glaucoma [email protected] 10 WWW. MD.LY [email protected] 11 WWW. MD.LY   Phacolytic glaucoma This is acute glaucoma in eyes with hypermature cataracts. lens protein passes through the intact lens capsule into the anterior chamber and is phagocytized. The trabecular meshwork becomes congested with protein-binding macrophages and the protein itself.  Morgagnian cataract It's hypermature cataract in which total liquefaction of cortex has allowed nucleus to sink down to lower part of capsule. [email protected] 12 WWW. MD.LY   Intumescent lens It's immature cataract in which the process of hydration suddenly exaggerated lead to swelling of lens Symptoms decrease of vision (counter finger) Signs A/C :- shallow Iris shadow :- may present [email protected] 13 WWW. MD.LY Iris tremulous: - absent Red reflex: - seen Complication 1- Phacomorphic glaucoma (by producing pupillary block) 2-Senile nuclear cataract Lens opacity affecting nucleus (central part).  Symptoms 1- Gradual painless diminish of vision 2- Index myopia (increase refractive index of nucleus) 3- Defective day vision (due to miosis)  Signs Central disc shaped opacity Red reflex:-dark central area with large clear ring of red reflex [email protected] 14 WWW. MD.LY   Treatment of senile cataract Surgical (cataract extraction) with IOL implantation Traumatic Cataract Most common cause of unilateral cataract in young individual. Causes 1- Direct penetrating injury. 2- Concussion (blunt trauma) A-Vossius ring due to "imprinting" of iris pigment on anterior lens capsule B-Rosette cataract (flower – shape cataract) 3- Electrical shock & lightning 4- Ionizing radiation: - X-ray, U.V ray 5- Heat (Infrared radiation) 6- Foreign body intraocular:- A-Siderotic cataract Iron foreign body B-Sunflower cataract Copper foreign body Treatment 1- Cataract extraction with IOL implantation [email protected] 15 WWW. MD.LY [email protected] 16 WWW. MD.LY [email protected] 17 WWW. MD.LY  Complicated (Secondary) cataract It's lens opacity due to local disease of eye or systemic disease  Types 1-Complicated cataract due to local cause:-mainly unilateral 2-Complicated cataract due to systemic cause: - mainly bilateral  Complicated cataract due to local cause :- ((HR - GUT – KILL)) High myopia Glaucoma Keratitis Retinitis pigmentosa Uveitis Intra-ocular tumor Topical drug Lens displaced Long standing retinal Detachment Topical drug: - Steroid, strong miotic drops such as phospholine iodide.  Complicated cataract due to systemic cause:-(HMADA -TMC -GM) Hypoparathyroidism sysTemic drug Galactosemia Myotonic dystrophy Mongolism Marfan syndrome Atopic dermatitis Cretinism Diabetes mellitus Ankylostoma Systemic drug: - Steroid, Busulphan, Amiodarone, Gold, Allopurinol, Chlorpromazine  Treatment Cataract extraction + IOL Subcapsular Cataracts Types 1-Anterior subcapsular. 2-Posterior subcapsular. ((Posterior subcapsular cataracts are more common than Anterior subcapsular cataracts (PSC).))  Posterior subcapsular cataract  Symptoms [email protected] 18 WWW. MD.LY People with PSC have difficulty with glare (problems seeing in a bright light in day or night) and more difficulty with near vision than with distance vision. Even when the cataract is small in size, it can still create a significant amount of interference with the activities of daily living. But see well in dim illumination.  Causes 1- Diabetes Mellitus ((DM)) 2- Steroid Medication 3- Retinitis pigmentosa ((RP)) 4- Other Causes Myopia & Hypermetropia, Chronic uveitis, Trauma, Radiation Treatment of cataract ((Only Surgical treatment))  Indication (TIME) of cataract surgery 1- Visual improvement (Most common indication) -If cataract cause difficult to performing daily essential activity. -If patient job need good vision like driver. 2- Medical indications -when cataract affecting health of eye e.g. Glaucoma phacomorphic, glaucoma phacolytic (Lens induce glaucoma) -to improve the clarity of ocular media may also be required in the context of fundal pathology (e.g. diabetic retinopathy) requiring monitoring or treatment with laser photocoagulation. 3- Cosmetic Are rare, such as when as mature cataract in blind eye is removed to restore black pupil.  Pre-operative assessment (1)- Local examination 1- Lid: - should be free from infection, (blepharitis, Stye) 2-Lacrimal: - (regurgitation test) should be –ve 3-Convunctiva: - should be free from infection (Conjunctivitis) 4-Cornea: - should be free from infection (keratitis) 5-Iris: - should be free from infection (Iritis) [email protected] 19 WWW. MD.LY 6-Lens: - for stage of cataract & lens position 7-Intra-ocular pressure: - to exclude Glaucoma 8-Fundus: - to evaluate the retina & optic nerve (Immature cataract) In ((mature cataract or hypermature cataract)) Retinal function tests:- (1) Macular function tests (cone function), (central retinal function) Visual acuity, Colour vision (colour differentiation) (2) (Peripheral retinal function) Light projection (3) Visual pathway (optic nerve ) Pupillary reaction (Light reflex) (2) General examination 1- Dental & ENT examination: - for any septic foci. 2-Medical examination:- (A)- Chest examination for Chronic cough. (B)- Cardiological examination for Hypertension. (C)- Abdominal examination for Constipation (D)- Urological examination for senile prostatic enlargement (3)- Investigation 1- CBC for Infection 2- Viral screen for Hepatitis, HIV 3- Blood sugar for DM 4- Urine analysis for UTI (urinary tract infection) 5- Coagulation test for bleeding time 6- X-ray for Pulmonary infection (4)- Take consent from patient & explain to patient procedure & complication. (5)- Most adult cataract surgery is done under local anaesthesia. ((General anaesthesia used for young and uncooperative patients.))  Types of surgery 1-Intra-capsular cataract extraction with peripheral iridoectomy +IOL anterior chamber 2-Extra-capsular cataract extraction + IOL posterior chamber 3-Phacoemulsification +IOL posterior chamber [email protected] 20 WWW. MD.LY Surgery Intra Capsular Extra Capsular Phacomulsification Cataract Extraction Cataract Extraction ((ICCE)) ((ECCE)) ((PHACO)) Principle Complete removal of Opening the anterior This technique consist of lens within its capsule, remove nucleus breaking down of capsule and cortex, leaving part cataractous lens by of anterior capsule and application of ultrasonic whole posterior vibration capsule. Advantage 1-No after cataract 1-Low degree 1-Very small incision (3mm) astigmatism 2- Less tissue injury 2- Low risk of 3- Faster healing A-Vitreous loss 4-More rapid visual B-Retinal detachment rehabilitation C-Macular edema 5- Minimum or No 3- Posterior chamber astigmatism IOL is possible 6-Less expulsive hemorrhage 7-Less corneal endothelium damage Disadvantage 1-High degree 1- After cataract 1- Machine dependent astigmatism 2-Expensive technique 2- High risk of 3-Longer learning period A-Vitreous loss 4-Complication are common B-Retinal while learning detachment 5- Difficult with hard nucleus C-Macular edema 6- After cataract 3- Posterior chamber IOL is not possible Only anterior IOL Indication 1-Lens sublaxation 1-young patient below 1-young patient below 40 2-Lens dislocation 40 years old due to years old due to strong strong zonule zonule 2-complicated cataract 2-complicated cataract of of high myopia high myopia Contra- 1-young patient 1-Lens sublaxation 1-Lens sublaxation indication below 40 years old 2-Lens dislocation 2-Lens dislocation due to strong zonule 2-complicated Cataract of high Myopia [email protected] 21 WWW. MD.LY   Complication of cataract extraction Pre- operative 1-Retrobulbar hematoma proptosis complication 2- Perforation of globe (complication of 3-Intra-arterial injection of xyolcain convulsion local anesthesia) 4- Optic nerve damage blindness Intra-operative 1-Hyphema 2-Expulsive hemorrhage Complication 3-Corneal injury 4-Iris prolapse , Iridodialysis 5-**Rupture of Posterior capsule vitreous loss Vitreous loss lead to (post-operative) Excessive astigmatism Bullous keratopathy Drawn up pupil Glaucoma Cystoid macular edema Retinal detachment Expulsive hemorrhage (suprachoroidal hemorrhage) 6-Lens dislocation fragments 7-IOL displacement Early post operative 1-**Corneal edema complication 2-Wound leakage (shallow anterior chamber) 3-Iris prolapse 4-Anterior synechiae 5-Iridocyclitis (Anterior uveitis) 6-Expulsive hemorrhage 7-Infection: - ((Acute post-operative endophthalmitis)) 8-Increase of IOP (Glaucoma) 9-Choroidal detachment 10- Wrong IOL power Late post operative 1-Corneal decompensation complication 2-Aphakic glaucoma 3-**After cataract (ECCE & PHACO) 4-IOL displacement 5-Post-operative astigmatism 6-Choroidal & retinal detachment 7-Cystoids macular edema ((CME)) ((Irvine-Gass syndrome)) 7-Infection: - ((Chronic post-operative endophthalmitis)) [email protected] 22 WWW. MD.LY [email protected] 23 WWW. MD.LY [email protected] 24 WWW. MD.LY  After cataract After cataract = Secondary membrane = Posterior capsular opacification It's lens opacity in the pupillary area ((posterior capsule)) seen after ECCE or phacomulsification.  Treatment YAG laser capsulotomy [email protected] 25 WWW. MD.LY  (( Complications of this technique include a transient rise in IOP, damage to IOL, and rupture of the anterior Hyaloid face with forward displacement of vitreous into the anterior chamber, potentially leading to rhegmatogenous RD or CME.)) Aphakia Definition Complete absence of lens from pupillary area Causes 1- Congenital 2- Acquired: - trauma (posterior dislocation), surgical remove Symptoms Decrease of vision Signs Scar of surgery AC: - deep Iris: - iridodenesis Pupil: - jet black One purkinje image [email protected] 26 WWW. MD.LY Treatment Unilateral: - contact lens, IOL Bilateral: - contact lens, IOL, glasses **N.B 1-Aphakia may lead to Anisometropia & Aniseikonia 2-Pseudophakia: An eye that has had a cataract removed and artificial IOL implanted. Displacement of lens ((Ectopia lentis))  Types 1. Dislocation of lens :-Complete displacement of lens from pupillary area 2. Sublaxation of lens: - Partial displacement of lens from pupillary area. [email protected] 27 WWW. MD.LY [email protected] 28 WWW. MD.LY  Sublaxation of lens Causes 1- Congenital A- Marfan syndrome (Bilateral),(upper – temporal) ,(AD). B- Homocystinuria (Bilateral),(infra – nasal) ,(AR). C- Associated with buphthalmos, macro-cornea, Aniridia D- Familial Ectopia lentis (Bilateral )(AD),(upper-temporal),(NO systemic abnormality) [email protected] 29 WWW. MD.LY  E- Ehler-danlos syndrome F- Sturge-weber syndrome just for MCQ G- Stickler syndrome 2-Aquired A-Trauma (most common cause) B-High myopia C-Hypermature cataract Symptoms 1-defective vision due to artificial myopia and astigmatism 2- Uniocular diplopia (if edge of lens crosses the pupil) Signs 1- AC: - irregular depth 2- Iridodenesis 3- Lens: - edge of lens can be seen through the pupil & phacodenesis Complication 1- Complete dislocation 2- Cataract 3- Iridocyclitis 4- 2ry glaucoma Treatment 1- Correct refractory error 2- If there any complication: - Remove lens Dislocation of lens It's complete displacement of lens from pupillary area Causes: - as in sublaxation  Clinical types (1)- Anterior dislocation (in the anterior chamber) Appear as globe of oil  Complication As in sublaxation + corneal edema & opacity  Treatment [email protected] 30 WWW. MD.LY  Remove the lens (2)- Posterior dislocation (in the vitreous cavity) Same like aphakia  Investigation Fundoscopy, Ultrasound B  Treatment If no complication: - correct refractive error If complication: - remove lens (3)- Sub-conjunctival dislocation (sever trauma lead to cut of sclera) IOL (Intra-Ocular lens) Types 1-Anterior chamber IOL (A/C IOL) 2-Posterior chamber IOL (P/C IOL) Indication 1-Monocular cataract with good vision in other eye 2-Patient with local condition unsuitable for contact lens 3- Patient unsuitable for glasses facial deformity Contraindication A-absolute 1-Patient does not want IOL 2-Recurrent ocular inflammation 3-Retinal detachment 4-Rubeosis iridis B-relative 1-High myopia 2-IOL failure in other eye 3-One eye patient 4-Presence of uncontrolled glaucoma Complication of 1-Uveitis 2-2ry glaucoma 3-Displacment of IOL IOL 4-Hyphema >>> IOL A/C 5-Corneal edema >>>IOL A/C Calculation of ( SRK formula) lens power P = A - 2.5L - 0.9K A= axial length >>> measured by ULTRASOUND A L= constant K= curvature of anterior corneal surface >>> measured by KERATOMETRY [email protected] 31 WWW. 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