DISEASES OF LENS

ANATOMY:

unequally biconvex , transparent, avascular, crystalline.

diameter = 9-10mm; thick = 3.5[birth] 5[adult]

Power = 15D, Accommodation = 15D[birth], 7D[25 age], 1D[50age].

RI = 1.39

STRUCTURE:

1. Capsule – thicker anteriorly.
2. Anterior epithelium – cuboidal [posterior epithelium is absent since used up in filling developmental lens vesicle.
3. Lens fibres - formed from elongation of equatorial epithelial cels & arranged compactly as NUCLEUS [oldest fibres in b layers: Embryonic fibres[meet arount Ysutures], Fetal , Infantile, Adult] & young CORTEX.
4. Ciliary zonules – position lens & exert ciliary ms action.

Cortical METABOLISM:

being avascular depends on aqH chemical exchange for growth & active transport.

anaerobic glycolysis [80%], HMPshunt [15%], oxidative Kreb [little], Sorbital only in cataractproduction in DM & Galactosemia.

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CATARACT

opacification of lens fibres due to :

1. growth disturbance – CONGENITAL [central involving Embryonic / Foetal nucleus] & DEVELOPMENTAL [peripheral : infantile / adult nucleus , deep cortex, capsule]
2. degenerative from either water & electrolyte imbalance or denatured protein -ACQUIRED [Senile, Traumatic, Complicated, Metabolic, Toxic (steroids, myotics, Cu, Fe), with diseases of skin/bone/down's syndrome]

morphologically: polar, capsular, subcapsular, cortical, supranuclear, nuclear.

Etiology:

1. Dominant inheritance
2. Maternal factors – malnutrition; rubella,toxoplasmosis,CMV; steroids; radiation.
3. Foetal factors – anoxia, hypoglycemia, malnutrition, trauma, Down’s
4. 50% idiopathic.

Clinical types:

Congenital – delayed dev of anterior chamber
Acquired – contact with cornea

Clinical type of cataract	Opacity	Etiology	Vision defect
Pulverulenta /Embryonic nuclear	central round powdery	dominant inheritance
Zonular / Lamellar / Foetal nuclear (most common 50%)	ring with riders	dominant inheritance, Vit D, rubella	SEVERE.
Sutural	punctate opacities around Y sutures.
Anterior polar	plaque / pyramid / reduplicated	amterior pole (capsule +/- subcapsular)
Posterior polar (common)	circumscribed circular opacity at posterior pole	incomplete hyalloid bv regression (persistant posterior vascular capsule)
Coronary (common)	radially arranged club shaped opacities at periphery	DEVLOPMENTAL cataract involving adolescent nucleus or deep cortex
Punctate / Blue dot / cerulea	peripheral round blue dots	DEVELOPMENTAL cataract involving adolescent nucleus or deep cortex	diminished vision if associated with CORONARY cataract
Total congenital soft (common)	uni/bilateral soft / liquefied white nuclear cataract which is progressive	dominant inheritance, rubella
Congenital membranous (misdiagnosed as congenital aphakia)	thin membranous or fine transparent capsule	total or partial absorption of congenital cataract.

Rx:

• ignore if cataract is small
• iridectomy or mydriatic to improve vision in incomplete central cataract.
• remove in few wks after birth if complete cataract
• Surgical procedures – Intracapsular capsular cataract extraction [antrior capsulotomy, phacoemulcification, posterior chamber IOL implantation]
• Aphakia in child <5yr corrected with extended wear contact lens & in child with age >5yr corrected with posterior chamber IOL.

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SENILE CATARACT

age related degeneration in >50yr age & usually unequally bilateral.

Factors influencing onset & maturation:

1. genes
2. UVrays
3. diet – proteins, Vit E C riboflavin , essential elements
4. severe dehydration

CORTICAL / SOFT cataract	NUCLEAR / HARD cataract
PATHOGENESIS: diminished active transport causing decrease in proteins & [K]+ but increase in [Na]+&water which denatures colloid into soft lens.	PATHOGENESIS & MATURATION: increased sclerosis causing dehydration-compaction & increased insoluble proteins which make the lens hard progressing from centre to periphery except for a cortical rim.
MATURATION STAGES
Reversible lamellar separation of cortex due to fluid	hard lens is inelastic leading to decrease in accommodation / increased myopia & obstructing light.
INCEPIENT cataract has small early opacities with clear areas inbetween. 2 types: CUNEIFROM [70%]- peripheral & radially arranged wedge opacities initially in inferior nasal [late vision loss] CUPULIFORM [5%] – posterior subcapsular cataract causing early vision loss due to axial rays obstruction.	25% common
IMMATURE cataract is irregularly diffuse opacity of both nucleus & cortex but with inbetween clear cortex [thus iris shadow] still visible. INTUMESCENT cataract sometimes forms due to continued hydration & swelling up of lens with water clefts in cortex. [shallow anterior chamber]	Grey opacity or pigmented [brown, black, red]
MATURE / RIPE cataract is a complete pearly white opacification of lens.
Hypermature: MORGAGNIAN – milky liquefication of cortex & brown nucleus settles at bottom. SCLEROTIC – disintegration of cortex + water leakage causes the lens to shrink & the capsule is wrinkled+thickened.

Symptoms:

1. earliest symptom – Glare [intolerance to bright light]
2. other early symtoms – Blurring & polyopia due to variable RI.
3. Colored halos due to refraction thr water in lens.
4. Black spots.
5. Slow painless progression of vision loss to end light perception only
   1. early in Cupiliform [day blindness]
   2. late in Cuneiform [night blindness]
   3. second sight in Nuclear [increased near vision]

Signs:

1. Visual acuity
2. Oblique ight beam on pupil -
   1. in immature cataract [clear cortex still seen] a crescentic pupillary iris margin is seen on grey opacity of lens [absent if lens is completely trasparent or opaque]
   2. reveals color of lens in pupillary area.
3. Distant direct ophthalmoscopy shows a black shadow of partial cataract on red fundal reflex.
4. Slit lamp examination in a mydriatic eye shows morphology of opacity.

Non-surgical Rx:

1. treating cause of acquired cataract – DM, uveitis, steroids, miotics, radiation
2. Delay progression with [I]- salts, vitE, aspirin
3. Improve vision in Incipient & Immature cataract by
   1. correcting refraction
   2. varying illumination [bright for peripheral opacity; dull /dark goggles for central]
   3. mydriatic [phenylepherine, tropicamide] for Cupuliform axial cataract

Surgical Rx:

Indications for surgery:

1. visual acuity < 6/36
2. lens induced glaucoma, phacoanaphylactic endophthalmitis, Dretinopathy, Retinal detachment
3. cosmetic reason for black pupil

Pre-operative evaluation:

1. no DM, HTN, cardiac disease, obstructive lung disease, infection in gums/UT
2. no local infection in conj, meibom, bleph, lacrimal
3. Intact retinal function
   • positive light perception
   • negative Marcus Gunn pupillary response due to defective afferrent pathway
   • positive for Projected rays for peripheral retina function
   • 2 light discrimation [2" apart & 2ft far] for macular function
   • positive perception of distant bright light as red line with Maddox rod
   • color perception for optic.N
   • ectopic visualization – point light on closed eyelids perceived as black retinal bv
   • Objective tests – laser interferometry, ultrasonic, ERG, EOG, VER, Indirect ophthalmoscopy
4. Slit lamp examination of anterior segment for KPs, corneal endothelium condition
5. measure IOP

Pre-operative medication:

1. Endophthalmitis prophylaxis – topical tobramycin [QD 3days], i.m Gentamycin [night & morning before]
2. lower IOP – stat acetazolamide/mannitol/glycerol
3. dilate pupil – anti-PG drops [indomethacine, flubriprofen TD 1day + evry 30min 2hrs before] , mydriatic [tropicamide, phenylephrine every 10min for 1hr]]

Surgery : done under local anaesthesia.

INTRACAPSULAR CATARACT EXTRACTION	EXTRACAPSULAR CATARACT EXTRACTION
removal of cataract with capsule	removal of cataract but leaving behind intact posterior capsule
Indications: zonule rupture due to marked subluxated & dislocated lens >50 age with weak zonules when microsurgery / trained surgeon unavailably [developing countries]	Indications: posterior chamber IOL implantation high myopia & degenerated vitreous <40age with strong zonules H/O vitreous prolapse , aphakic retinal detachment
Contra-indications: <40age with strong zonules	Contra-indications ruptured zonules in subluxated & dislocated lens
Complications: endophthalmitis cystoid macular edema retinal detachment vitreous herniation into anterior chamber, pipillary block, touch syndrome	Complications: posterior capsule opacification

ECCE:

1. down gaze fixed with superior rectus bridle suture
2. conjunctival flap to expose limbus
3. heat cautery for haemostasis
4. limbal partial thickness groove [10-2 O'] with razor blade knife
5. anterior capsulotomy
   • can-opener technique – 360. radial cuts with cystitome
   • linear / envelope – only 10-2 incision
   • capsulorrhexis – torn circularly
6. Removal of anterior capsule with Kelman-Mc Pherson forceps
7. Corneo-scleral section [10-2] with enlarging scissors
8. Hydro-dissection with balanced salt soln to separate anterior capsule from lens
9. Removal of nucleus with pressure-counterpressure or irrigating wire vectis loop
10. Cortex aspiration with 2way irrigating aspirating canula
11. Close incision with 5-7 interrupted sutures
12. Conj flap reposited with 2sutures
13. subconj inj of dexamethosone & gentamycin
14. patching with pad & bandage

Phacoemulsification:

1. 3mm corneo-scleral section which is self-sealing.
2. anterior capsulotomy with capsulorrhexis
3. hydro-dissection [separate anterior capsule] & hydro-delineation [separate nucleus]
4. phaco-emulsification with ultrasonic vibrator using divide into 4quadrants & conquer rule.
5. cortex aspiration

IOL implantation:

IOL power is calculated with biometer of A-scan ultrasound machine.

Indications – [PRIMARY] unilateral catarcat removal in developing countries, [SECONDARY] correcting aphakia

foldable IOL is made of silicone / acrylic

most commonly used is Posterior chamber modified C loop IOL [central optic + superior&inferior haptics]- horizontally placed behind iris supported in posterior capsular bag

post-operative complications are high for anterior chamber IOL[in front of iris supported in angle] & iris supported IOL [fixed on iris with sutures,loops, claws].

Post-operative measurs:

3hrs still on back without oral intake

diclofenac inj if mod-severe pain

next morning check for complications after removing bandage

cyclopentolate+antibiotic+steroid oint for 3days

tinted glass + antibiotic-steroid drops for tapered from 4 to 1 times/day for 2wks each

after 6wks remove sutures

after 8wks final spectacles

COMPLICATIONS:

Preoperative	Mangement
anxiety	diazepam at bedtime
nausea/gatritis from acetazolamide, glycerol	antacids, omission of cause
allergic/irritative conjunctivitis from topical antibiotics	withdraw cause potpone surgery for 2days
corneal abrasion from tonometry	antibiotic patching 1day postpone surgery for 2days
retrobulbar local anaesthesia may cause retrobulbar haemorrage oculocardiac reflex perforation subconj haemorrgae posterior dislocation during massage due to degenerated zonules with hypermature cataract	pilocarpine + immediate pressure bandage + surgery posponed 1wk atropine i.v prevent by peribulbar blunt-needle anaesthesia minor so ignore removed by vitrectomy only if it causes uveitis/glaucoma
Operative	Management
superior rectus laceraton from bridle suture	ignore
excessive bleeding from conj flap or incision into anterior chamber	cautery
irregular incision from blunt instruments causes coaptation of wound
sharp instrument during anterior chamder entry may injure cornea, iris, lens	gentle handling with hypotony
vitreous loss due to posterior capsule rupture[most serious complication]	prevent with preoperative hyperosmotic [mannitol, glycerol], lower IOP [acetazolamide, massage], better anaesthesia. minimise external pressure by gentle handling during surgery. fleringa ring in myopic to prevent scleral collapse anterior hyaloid face rupture form unavoidable high IOP can be prevented by posterior sclerotomy with vireous drainage from pars plana. after vitreous loss, partial anterior vitrectomy for clearance from anterior chamber & preventing post-operative complications [updrawn pupil, iris prolapse, touch syndrome]
choroidal haemorrhage [most serious complication]in HTN, arteriosclerosis. occurs immediately / postoperatively [gaping followed by expulsion of lens, citreous, retina, uvea, blood.	drain blood with equatorial sclerotomy; most times eye is lost requiring evisceration.
Early postoperative	Management
hyphaema from minor trauma	if spontaneously not absorbed & causes IOP rise, acetazolamide , mannitol, glycerol ; after a wk Paracentesis.
Iiris prolapse from inadequate suturing	if small & early, reposited & sutured. if large & late, abscission & suturing.
Striate keratopathy [mild corneal edema + descemet folds] due to endothelial damage	if spontaneouslt does not disappear n a wk, hypertonic saline + steroids. penetrating keratoplasty for bullous keratopathy.
flat anterior chamber [rare] due to woundleak >associated hypotony diagnosed with SEIDEL’s test [fluorescein into lower fornix + blink ---> incision seen as diluted AqH in slit-lamp cobalt blue. ciliochoroidal detachment [brown convex mass] pupil block due to vitreous bulge leads to iris bombe —> peripheral anterior synechiae —> angle closure glaucoma	pressure bandage + acetazolamide. If persisting, air is injected in anterior chamber + resuture wound. pressure bandage + acetazolamide. If persisting, suprachoroidal drainage + inject air into anterior chamber. initially with mydriatic +hyperosmotic + acetazolamide. later bypass by peripheral iridectomy.
Bacterial endophthamitis [most dreaded, incidence <0.5] from contamination with flora. ‘[pain, diminished vision, lid edema, conj chemosis, circumciliary congestion, corneal edema, pupil exudates, hypopyon, diminished red reflex]	emergency – frill evisceration to prevent intracranial spread.
Late post-operative [after wks,yrs]	Management
Cystoid macular edema [significant only if dimished vision, diagnosis: fundoscopy - honeycomb pattern of cycstic loculi fluoroscein angiography - flower petal pattern due to perifoveal capillaries dye leak.	Prophylaxis pre& post-operative anti-PGs [indometh, flurbip]
Retinal detachment
Conj epithelial ingrowth
Vitreous touch syndrome [corneal edema -->bullous keratopahty] [IRVINE GASS syndrome = triad of vitreous touch, bullous keratopathy, cystoid macular edema]
Fibrous downgrowth due to imperfect wound apposition —> glaucoma, anterior segment disorganisation, phthisis bulbi.
After cataract = secondary opacification after catarcat lens extraction due to residual opaque lens matter thickened posterior capsule dense membranous Soemmering’s ring between capsules Elschnig’s pearls along posterior capsule as clusters of vacuolated epithelial cells	capsulotomy membranectomy If central posterior capsule is clean, no treatment is required. capsulotomy
Glaucoma in aphakia
IOL related	Management
high with ACIOL & ISIOL: cystoid macular edema, corneal damage, glaucoma, uveitis
Malpositioned IOL : subluxated – sunset, sunrise syndromes. dislocation into vitreous – lost lens syndrome small IOL placed vertically – windshield wiper syndrome
Toxic lens syndrome [uveitis] from sterilizing agent or implanted lens material itself