Glaucoma

ANATOMY:

Pathophysiology revolves around AqH dynamics:

Ciliary body:

AqH production.

Anterior chamber angle

Formed by [ICSTL] iris root, ciliary body anterior, scleral spur, trabecular mesh, Schwalbe’s line[corneal descemet]

Width varies in different individuals

Visualised by Gonioscopic examination [diverts light to angle]

Shaffer’s system of angle width grading:

• 0 0degrees Closed, no structures visible
• 1 10degree chances of closure high [ICSTL]
• 2 20degree possible chances of closure [ICSTL]
• 3 20-35degrees Open angle [ICSTL]
• 4 Wide open [ICSTL]

AqH outflow system:

Trabecular mesh: sieve through which AqH leaves eye

1. UVEAL meshwork – innermost
2. CORNEOSCLERAL meshwork – middle larger portion with elliptical & smaller than uveal openings
3. JUXTACANALICULAR / ENDOTHELIAL meshwork – outermost connecting with Schlemm’s canal & narrowest offerring normal resistance to AqH outflow

Schlemm’s canal:

• oval circumferential channel in scleral sulcus
• inner endothelial cells have giant vacuoles
• Collector channels opn into outer cells

Collector channels / Intrascleral aqueous vessles:

terminate into episcleral veins

2 systems – larger ones terminate directly; smaller ones form intrascleral plexus before terminating

PHYSIOLOGY:

Aq production:

clear watery fluid whicxh maintains IOP & provides substrates & removes metabolites from avascular cornea & lens.

water [99.9], proteins [0.04], Na[144], K[4.5], Cl[110], glucose[6], lactic acid[7.4], aa[5], inositol[0.1

derived from cilliary processes at 2.3 microl/min filling anterior & posterior chambers. Mechanisms: [fluctuates diurnally; passive mechanisms altered by capillary BP, osmotic pressure, IOP; active secretion altered by vasopressin & adenylcyclase]

1. Ultrafiltration of ciliary processes’ stromal capillary plasma & accumulation behind non-pigment epithelium [BaqB].
2. Active secretion of some ions,aa, ascorbic across BaqB into posterior chamber by Na-K-ATPase pump & Carbonic anhydrase.
3. this in-turn causes osmotic diffusion of other plasma constituents into posterior chamber.

Through pupil, AqH flows from posterior to anterior chamber.

AqH drainage from anterior chamber: 2 routes

CONVENTIONAL TRABECULAR OUTFLOW [90%]-

1. giant vacuoles in inner endothelium of Schlemm’s canal trasport AqH from juxtacanalicular to collecting channels by forming intracellular transport channel.
2. 10mm pressure gradient is responsible for unidirectional flow from intraocular trabeculae to intrascleral episcleral veins

Unconventional UVEOSCLERAL outflow:[10%] from ciliary body to suprachoroidal space then into veins of choroid, sclera, ciliary body.

Maintenance of IOP: [10-21 mm]

Local factors:

1. AfH production depends on capillary permeability, osmotic pressure, IOP.
2. resistance offerred at juxtacanalicular /endothelial trabular meshwork.
3. episcleral pressure increases during valsalva & inturn rises IOP
4. in narrow anterior chamber, relative obstruction by iris during pupil dilation rises IOP.

General factors:

1. hereditary, age >40 & greater in females
2. cortisol diurnal fluctuation of 8mm]
3. postural variation & HTN
4. indirectly proportional to plasma osmotic pressure which ris high with mannitol, glycerol, uraemia & low with drinking water provacation tests.
5. general anaesthetics, anti-glaucoma drugs varyIOP. steroids, caffeine, smoking rise IOP & alcohol lowers.

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Glaucoma

gorup of disorders where IOP is raised. above tolerance limit damaging optic.N head leading to irreversible visual defects

Ocular HTN

constantly raised IOP without visual field defects.

Normal/low tension glaucoma

disc cupping +/- visual field defects

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Primary developmental glaucoma

abnormally high IOP due to congenital trabeculodysgenesis causing abscence of angle from flat/concave iris insertion to trabeculum obstructing drainage.

True congenital – if it manifests prior to birth

Infantile – if it manifetss prior to age 3

Juvenile – if it manifests between 3-16 age.

BUPHTHALMOS / Hydrophthalmos – prior to age 3, high IOP even enlarges eyeball.

75% bilateral.

CFs:

1. Lacrimation + photophobia + blepharospasm + eyerubbing – from raised IOP irritating corneal nerves.
2. corneal signs -
   • Corneal edema is frequently the first sign & opacities may occur.
   • Corneal enlargement >13mm with deep anterior chamber [if prior to age 3 , buphthalmos also]
   • Haab’s striae in descemet since it is less elastic than stroma.
3. thin sclera with underlying blue uveal color
4. Iridodonesis
5. flat/subluxated lens due to stretched zonules
6. cupped optic disc
7. moderately high IOP measured with PERKIN’s applanation tonometer [instead of Schiotz since low scleral rigidity in children]

D/D

• corneal trauma/interstitial keratitis/endothelial dystrophy causing corneal edema
• megalocornea
• blocked nasolacrimal duct causing lacrimation
• uveitis, keratitis causing photophobia.
• high IOP from retinoblastoma, prematuruty retinopathy, hyperplastic vitreous, other types of glaucoma.

Rx:

Primarily surgical with prior lowering of IOP with acetazolamide,mannitol, glycerol, beta-blockers.

1. GONIOTOMY
2. Trabeculotomy + trabeculectomy – when corneal clouding prevents gonioscopic examination.

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DEVELOPMENTAL GLAUCOMAS ASSOCIATED WITH SYSTEMIC/OCULAR ANOMALIES

• Iridocorneal dysgenesis – Axenfeld anomaly, Peter’s anomaly, Rieger anomaly.
• Aniridia
• Displaced lens in Marfan, homocystenuria,
• phakomatosis in sturge-weber syndrome, Von recklinghausen’s neurofibromatosis
• Lowe syndrome [oculo-cerebro-renal], microcornea, rubella syndrome.

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Primary open angle glaucoma / Chronic simple [commonest]

↑ IOP due to sclerosed thickenned trabeculae & abscence of giant vacuoles.

Predisposing factors

1. heriditary
2. old age >40yr
3. myopic
4. diabetis, smoking, HTN, thyrotoxicosis

Symptoms:

1. insidious, bilateral, asymtomatic [mild headache/eyeache]
2. after 40% visual field loss – tunnel vision which is progressive & irreversilble.
3. accommodative failure due to pressure on ciliary muscle & nerve.
4. delayed dark adaptation

Signs:

1. Anterior segment [late stage]:sluggish pupillary reflex & corneal haze.
2. IOP [tonometry]:initially exagerrated diurnal variation >8mm. contrary to closed angle glaucoma, falls during evening. In late stages, permanently >21mm.
3. Optic disc: assymetric, progressive changes so recorded [most accurate method: confocal scanning laser topography]. PATHOPHYSIOLOGY: high IOP pushes back lamina cribrosa, mechanically squeezing nerve fibres’ axoplasma + causing vascular ischaemia [no increase in glia = Cavernous optic atrophy]
   • EARLY-
     • vertical oval cup due to superior& inferior loss of neural rim.
     • bilateral assymetry >0.2
     • cup:disc >0.5 [normal=0.3-0.4]
     • splinter hmmrhges at disc margin & pallor areas on disc.
     • atrophied retinal nerve fibre layer [ganglion cells] with red free light.
   • LATE-
     • markedly enlarged cup 0.7-0.9
     • crescentic margin due to notch created from thinning of neural rim.
     • nasal shift in retinal vessels & Bayonetting sign[broken at disc margin; hidden if margin overhangs]
     • Pathognomic: arteriolar pulsations at disc margin when IOP is very high.
     • Lamellar dot sign: slit pores of lamina cribrosa at disc margin.
   • Optic atrophy- head appears white & deeply excavated.
4. Visual field defects:[confrontation test]
   • temporal sup&inf arcuate fibres are most sensitive & macular horizontal fibres are most resistant to glaucomatous damage, hence central vision lost at the end. [central optic fibres are in superficial retina while peripheral fibres in deeper retina.]
   • Natural history of progression:
     1. ISOPTER CONTRACTION- mild total field constriction.
     2. BARING OF BLIND SPOT from central field.
     3. PARACENTRAL SCOTOMA in Bjerrum’s area [above&below blind spot]- earliest clinically significant sign.
     4. SIEDEL’S SCOTOMA- sickel shaped due to joining of blind spot & paracentral.
     5. ARCUATE BJERRUM’S SCOTOMA- extension of siedel’s above&below to reach horizontal line.
     6. RING/DOUBLT ARCUATE SCOTOMA- due to joining of similar arcs.
     7. ROENNE’S CENTRAL NASAL STEP- joining of different arcs forming a right angled defect
     8. PERIPHERAL FIELD DEFECTS- may appear early or late.
     9. ADVANCED DEFECTS- tunnel vision sparing small central & temporal islands. temporal is ultimately left before total blindness.

Ocular associations:

high myopia, fuch’s ED, retinitis pigmentosa, CRVO, retinal detachment.

Diagnosis:

1. Established POAG: cupping/visual field defects with IOP>21mm.
2. Glaucoma suspect / Ocular HTN: IOP>21mm.
   A suspect must be categorised as established case if :
   • IOP>30mm
   • diurnal variation>8mm
   • +Provocation test
   • assymmetry of cups>0.2mm
   • splinter hmrrges near disc.
   • family history
   • DM
   • high myopia
   • Anterior chamber pigment changes
3. NT glaucoma: normal IOP but with cupping+/-visual field defects.
   Etiology- chronic low perfusion makes OPitc.N succeptible to even normal IOP.
   Rx- frustrating

Rx:

1. Good baseline examination – for periodic supervision to prevent further vision loss while lowering IOP.
   • visual acuity, fundus photography, perimetry
   • applanation tonometry, diuranl variation, provocation test
   • slit lamp ex of anterior chamber, goniscopy
   • Nerve fibre layed analyzer – early detection before cup/field changes.
2. Medical therapy to lower IOP- 1st choice topical drug, if ineffective/intolerable shift to 2nd choice drug, if insufficient combination therapy.
   1. beta blockers [↓ AqH secretion]- 1st choice
      Systemic ADRs by absorption through higly vascular nasal mucosa from NLD ∴ CI: asthma, bradycardia
      • timolol, levobunolol [longest action]
      • betaxolol [beta1 selective] – cardiopulmonary case
      • cartiolol – hyperlipidemic
   2. CAinhibitors [dorzolamide - ↓ AqH secretion] – 2nd choice
   3. PG [latanoprost - ↓ uveal outflow] – most used adjuvant but expensive
      low ADRs – ↑ eyelash growth& iris melanin
   4. short-term adjuvants :
      1. acetazolamide [CAinh]
      2. pilocarpine [ciliary spasm opens trabeculae] – CI- older pt with axial lenticular opacities & chronic use in young since myopia&headache.
   5. alpha2 adrenergic [brimonidine- ↓ Aq production] – last resort adjuvant since allergic rxn & tachyphylaxis.
3. Laser trabeculoplasty – shrinking collagen in trab mesh ↑ outflow.
   Indications- noncompliance or failure of medical Rx.
   Complications-
   • transient ↑ IOP if no pretreatment with acetazolamide/pilocarpine
   • inflamm – treat with steroids
   • hmmrg
   • synechiae
   • ↓ accommodation
4. Fistulizing filtration surgery [trabeculectomy]- creates a new ouflow channel from anterior chamber to subconjunctival space.
   Indications- advanced disease or uncontrolled IOP or unavailability of laser trabeculoplasty
   Complications- visual risks

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Primary angle closure glaucoma

↑ IOP due to narrow angle blocking AqH outflow.
Mid-dilated pupil → pupil block → iris bombe [from built up AqH in posterior chamber] → iridocorneal angle closure → transient ↑ IOP → peripheral anterior synechiae causes a chronic ↑ IOP.

Predisposers:

1. Anatomical:
   • hypermetropia, antrerioly placed lens, plateau iris configuration
   • small cornea, small eyeball
   • large lens, large ciliary body
2. General: 50age female, anxiety, familiar, rainy season, SEasian
3. Ppt: dim light, emotional or physical stress, mydriatrics.

Clinical course	CFs	Diagnosis	Rx
Latent Glaucoma / Prodromal phase transient(seconds) ↑ IOP due to ppt factors	blurred vision, colored halos, mild headache corneal edema, shallow anterior chamber, narrow angle	colored halos around bright lights due to corneal edema [D/D: acute purulent conjunctivitis [discharge] & immature cataract [Fincham's test segmented halos when viewed thr stenopic slit] Gonioscopy -grade 1or 2 Slit-lamp grading against conreal thickness Provocation tests – darkroom [1hr & awake for dilated pupil], mydriatric test + → succeptible to spontaneous closure - → doesn’t rule out closure so warn for symptoms	pre-operative pilocarpine + both eyes : iridectomy / laser iridotomy
Intermittent Glaucoma / Constant instabaility phase recurrent (min-hrs) regular ↑ IOP followed by bright light/sleep induced miosis	impaired vision, colored halos, eyeache/ frontal headache dilated pupil corneal edema, shallow anterior chamber, narrow angle	similar to above	similar to above
Acute congestive/angle closure Glaucoma sudden total angle closure causing high ↑ IOP for days	sudden severe pain [with vomiting, prostration] rapid progressive vision impairment redness lacrimation, photophobia edema of lids, conj, cornea very shallow anterior chamber, total angle closure pupil is mid-dilated : vertically oval, fixed optic disc : edema, hyperaemia fellow eye : shallow anterior chamber, narrow angle	D/D: acute red eye: conjunctivitis, iridocyclitis secondary acute congestive glaucomas: neovascular, phacomorphic, glaucomatocyclitic	temporary emergency medical therapy: stat analgesic [pethidine] injection topical drugs to lower IOP: initially [mild drugs since iris is ischaemic]- hyperosmotics[mannitol, glycerol], acetazolamide later- pilocarpine, beta blockers inflmm- steroid drops synechiae causing <50%angle closure- iridectomy / laser iridotomy to bypass pupil block >50% synechiae or uncontrolled IOP- fistualization filtration surgery [trabeculectomy] prophylactic surgery on fellow eye
Chronic closed angle Glaucoma constant ↑ IOP due to extensive peripheral anterior synechiae formed from intermittent or gradual[creeping] angle closure	permanently red & painful except in creeping[white, painless] visual field defects similar to POAG ↓ visual acuity gonioscopy: angle closure due to peripheral anterior synechiae optic disc cupping	D/D of creeping synechiae: POAG	for synechiae: ↓ IOP with medical therapy + filtration surgery prohylactic surgery in fellow eye
Absolute Glaucoma due to untreated chronic phase	completely blind painful eye perilimbal red-blue zone due to dilated anterior ciliary veins; later caput medusae initial corneal insensitivity → later hazy, bullous keratopathy / filamentous keratitis very shallow anterior chamber atrophic iris pupil : dilated, fixed, green disc atrophy stony hard eyeball due to high IOP	-	for pain- destroy ciliary ganglion with retrobulbar alcohol inj lower IOP- destroy secretory ciliary epithelium with cyclocryotherapy / diathermy/ photocoagulation failed conservativeRx / malignant progression- enucleation
Complications	corneal ulcer staphyloma from bulged out atrophic sclera from high IOP atrophic bulbi from ciliary body degeneration	-	-

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Scondary glaucomas

Phacogenic glaucomas	MOA	Rx
Phacomorphic [angle/pupil block]	altered lens morphology intumescent [swollen] anterior subluxated / dislocated spherophakia	medical to ↓ IOP & lens extraction surgery
Phacolytic	morgagnian hypermature cataractous lens leaks fine white protein thr lens capsule → phagocytosed by macrophages → clog trabe mesh	medical therapy to ↓ IOP & lens extraction surgery
Lens particle	disloged lens particles after trauma → clog trabe mesh	medical therapy to ↓ IOP & apsirate lens particle
Phacogenic uveitis	lens induced uveitis → lens particles & inflm cells clog trabe mesh	medical therapy to ↓ IOP uveitis- steroids & cycloplegics aspirate lens particles
Phacoanaphylaxis	fulminating inflm from antibody attacks to lens protein	medical to ↓ IOP steroids

Inflammatory glaucomas Glaucomas associated with uveitis	MOA & CFs	Rx
Acute anterior uveitis	clogged trabe mesh from inflm cells exudate turbid AqH edema ↑ IOP	steroids, cycloplegics & ↓ IOP with medical therapy
Post-inflmmatory	pupil block from annular synechiae or iris bombe angle closure from organization of inflmm debris	synechiae prophylaxis – steroids&cycloplegics &darrIOP with medical therapy [CI-miotics] pupil block – iridectomy angle closure – trabeculectomy
Specific HTNisve uveitis syndromes	Fuch’s uveitis syndrome Glaucomatocyclitic crisis	-

Pigmentary glaucoma [young myopic male]	pigment shedding from mechanical rubbing of iris & zonules → clog trabe mesh krukenberg’s spindle on posterior cornea zonules lens SAMPAOLESI’s line [inferior schwalbe's line] Pathognomic: iris shows radial slits in mid-periphery on trans-illumination	Rx: similar to POAG

Neovascular intractable glaucoma 3 stgaes: rubeosis iridis pretrabecular neovascular membrane → open angle glaucoma goniosynechiae [contacture of neovasc membrane] → zipper angle closure glaucoma	Etiology: retinal ischaemia in D.retinopathy CRVO, CRAO Sickle cell retinopathy Eale’s disease Intraocular – chronic inflm, tumor R.detachment	Rx: curb neovasc → Pan-retinal photocoagulation ↓ intractableIOP with Artificial drainage shunt [seton valve implant]

Intraocular tumors [MalignantMelanoma (iris, choroid, ciliary body) Retinoblastoma]	tumor cell invasion or clogging of trabe mesh neovasculariztn of angle vortex venous stasis from obstruction anterior subluxation of iris	Rx: enucleation

Pseudo-exfoliative / Glaucoma capsulare	amorphous grey dandruff like material deposition on: anterior lens posterior iris zonules ciliary processes	Rx: similar to POAG

Glaucomas-in-aphakia	conditions: poat-operative ↑ IOP due to hyphaema, inflm, chymotrypsin, vitreous in anterior chamber angle closure due to flat anterior chamber pupil block from anterior synechiae / vitreous herniation pre-existing POAG steroids for post-operative cataract post-operative epithelial ingrowth into trabe mesh aphakic malignant glaucoma

Steroid induced glaucoma [topical/systemic]	inn a genetically determined[40%] patient may cause mucopolysaccharides deposition in trabe mesh	Rx: monitoring IOP while steroid use discontinue steroids & treat glaucoma with timolol filtration surgery if glaucoma is intractable after 1mos

Traumatic glaucoma	blunt/perforating injury causes the following conditions which ↑ IOP: uveitis hmmrg ruptured lens anterior synechiae adherent leucoma epithelial/fibrous ingrowth trabe disruption & fibrosis causing angle recession	Rx: ↓ IOP with medical therapy treat the causative conditions

Malignant glaucoma / Ciliary block glaucoma [rare early post-operative complication of any intraocular surgery esp PACG - peripheral iredectomy / trabeculectomy]	Ciliary block of AqH flow at: cilio-lenticular in phakic cilio-vitreal in aphakic which causes AqH to collect posteriorly as vitreous pockets & ↑ IOP: persistent flat anterior chamber negative Seidel’s test unresponsive to miotics	Rx: atropine to dilate ciliary ring acetazolamide & timolol to ↓ AqH production i.v mannitol to shrink vitreous posterior sclerotomy if unresponsive to medical Rx for 5days aspirate fluid from vitreous inject air into anterior chamber

Intraocular hmmrges [hyphaema, vitreous]

types of glaucoma: Red cell glaucoma – trabe clogged by RBCs in fresh massive traumatic hyphaema [after few days corneal blood staining occurs] Hemolytic glaucoma – trabe clogged by macrophages with lysed RBC Ghost cell glaucoma [vitreous hmmrg in aphakia]- after 2wks RBCs turn khaki colored ghost cells which clog trabe Hemosiderin glaucoma [rare]- sclerosis induced by iron from trabe’s endothelial cells’ phagocytosed Hb.

Iridocorneal endothelial syndromes progressive iris atrophy [iris hole] chandler’s syndrome [corneal edema] cogan reese syndrome [iris pigmented lesions]	usually seen in a middle aged female with abnormal corneal endothelium → proliferates forming a membrane in angle → contraction causes synechiael angle closure glaucoma

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Surgical procedures for glaucoma:

1. Peripheral Iridectomy- Rx+prophylaxis for PACG
2. Fistulization guarded filtering surgery – trabeculectomy [partial thickness fistula] – [post-operative complications: hyphaema, iritis, endophthalmitis, cataract]
   1. POAG
   2. >50% synechiae in PACG
   3. congenital&dev glaucomas where trabeculotomy&goniotomy fail
   4. secondary glaucoma
3. Antimetabolites[fluprpuracil,mitomycinC] + trabeculectomy:
   1. previous failed fistula
   2. glaucoma in aphakia
   3. some secondary glaucomas [inflmm,trauma]
   4. >3yr medical Rx for glaucoma
4. Artificial drainage shunt [seton's valve implant] – neovascular glaucoma, glaucoma with aniridia, intractable primary/secondary glaucomas
5. Cyclocryotherapy – destroy secretory ciliary epithelium in Absolute glaucomas.

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