GLAUCOMA

Figure:Glaucoma

CONGENITAL/ DEVELOPMETAL GLAUCOMA

Types:

1. Primary dev/ cong.
2. Developmental Glaucoma with associated ocular anomalies.

Primary dev/ cong. Glaucoma:

High IOP due to dev anomaly of the angle of AC.

1. True cong. Glaucoma – 40%
2. Infantile glaucoma – 50% manifests within 3 yrs
3. Juvenile glaucoma – 10%, manifests b/w 3-16yrs of life.

WHEN THE DISEASE MANIFESTS PRIOR TP AGE 3YRS, THE EYEBALL ENLARGES AND SO THE TERM ‘BUPHTHALMOS’ (HYDROPHTHALMOS)

IS USED.

Prevalence and genetic pattern: Mostly sporadic, 10% autosomal recessive,

65% boys, 75% bilateral, may be asymmetric

Affects 1 child in 10,000 live births.

Pathogenesis:

Maldevelopment of trabeculum including the irido trabecular junction (trabeculodysgenesis) is responsible for impaired aqueous outflow resulting in raised IOP.

C/F:

1. Photophobia, blepharospasm, lacrimation. And eye rubbing.
2. Corneal signs:

i.              Corneal oedema

ii.            Corneal enlargement, normal infant cornea measures 10.5 mm diameter > 13mm confirms enlargement.

iii.           Tears and breaks in Descemet’s membrane (Haab’s sinae)

3. Sclera: thin and blue.
4. AC: deep.
5. Iris: iridodonesis, atrophic patches
6. Lens: flat, may subluxate.
7. Optic disc: variable cupping and atrophy, esp. after 3^rd yr.
8. IOP: moderately high.
9. Axial myopia and anisometropic amblyopia may develop.
10. Enlargement of globe: Buphthalmos.

Examination:

-       E U A include:

1.    Measurement of IOP

2.    Measurement of corneal diameter.

3.    Ophthalmoscopy to evaluate optic disc.

4.    Gonioscopic examination of angle of AC to detect abnormality: Trabeculodysgenesis.

D/D:

1. Keratitis.
2. Megalocornea
3. Lacrimation due to cong. NLD obstruction.
4. Retinoblastoma.

Treatment:

1. Rx is primarily surgical, after lowering of IOP by use of hyperosmotic agents, Acetazolamide, beta blockers.
2. Surgical procedures:

i.              Goniotomy

ii.            Trabeculotomy

iii.           Combined Trabeculotomy and trabeculotectomy.

PRIMARY OPEN ANGLE GLAUCOMA (POAG)/ CHRONIC SIMPLE GLAUCOMA:

Definition: Slowly progressive raised IOP associated with characteristic optic disc cupping and specific field defect in eyes with open angle of AC. There is no obvious systemic or ocular cause in rise in IOP.

Etiopathogenesis: Not known exactly.

1. PDF and risk factors:
1. Heredity: polygenic inheritance
2. Age: b/e 5^th and 7^th decade.
3. Race: common and severe in blacks.
4. Myopes: common.
5. Diabetics: higher prevalence.
6. Smoking: increased risk.
7. More prevalent in Hypertensive pts.
8. Thyrotoxicosis: more prevalence.
2. Pathogenesis of rise in IOP:

Decrease in aqueous outflow facility due to increased resistance to aqueous outflow caused by age related thickening and sclerosis of the trabeculae and absence of giant vacuoles in the cells linning the canal of Schlemm.

3. Corticosteroid responsiveness:

Pt. with POAG, offspring and siblings are likely to respond to six wks topical steroid with a significant rise in IOP.

Incidence of POAG: 1 in 100 of general population of either sex above the age of 40 yrs. Forms about one third cases of all glaucoma.

C/F of POAG:

Symptoms:

1. Insidious, usually asymptomatic.
2. Mild headache and eye ache.
3. Defect in visual field.
4. Increasing difficulties in reading and close works.
5. Frequent changes in presbyopic glasses.
6. Delayed dark adaptation.

Signs:

1. Anterior segment signs: usually normal, in late stages, corneal haze and sluggish pupil.
2. IOP: raised above 21 mm of Hg.
3. Optic disc changes:
1. Vertically oval cup.
2. Asymmetry of the cup, difference more than 0.2 b/w two eyes significant.
3. Large cup: Normal cup size, 0.3
4. Splinter hrgs on near disc margin.
5. Pallor areas on the disc.
6. Atrophy of the retinal nerve fibre layer.
7. Thinning of neuro retinal rim.
8. Nasal shifting of retinal vessels.
9. Pulsation of retinal arterioles. (pathognomic sign of raised IOP)
10. Glaucomatous optic atrophy, deeply excavated white disc.
11. Lamellar dot sign.
4. Visual field defects: Visual field defects initially observed in Bjerrum’s area (10-25degree from fixation) and correlate with optic disc changes.

i.              Isopter contraction.

ii.            Baring of blind spots.

iii.           Small wing-shaped paracental scotoma.

iv.           Seidel’s scotoma.

v.            Arcuate or Bjerrum’s scotoma.

vi.           Ring or double arcuate scotoma.

vii.          Rönne’s central nasal step.

viii.        Peripheral field defects.

ix.           Advanced field defects:

1. Tubular or tunnel vision; small central island of vision.
2. Temporal island of vision.

Investigations:

1. Tonometry
2. Diurnal variation of IOP
3. Gonioscopy
4. Documentation of optic disc changes
5. Slit-lamp exam to rule out secondary causes of POAG.
6. Perimetry
7. Nerve fiber layer analyzer.
8. Provocation test: water drinking test.

à 8 mm of Hg or more rises in IOP diagnostic of POAG.

Diagnosis of POAG:

1. POAG: IOP>21 mm Hg.

àGlaucomatous optic disc cupping and or visual field defects.

2. Ocular HTN or Glaucoma suspect:

àIOP>21mm Hg. No change in optic disc or visual field.

3. Normal tension or Low tension Glaucoma (NTG, LTG):

àTypical glaucomatous disc cupping, with or without visual field changes.

Mx of POAG:

General consideration:

Baseline evaluation and grading of severity of glaucoma.

Aim: To lower IOP to a level where further visual loss does not occur.
Therapeutic choices:

1. Medical therapy: initial choice.
2. Argon or diode laser trabeculoplasty, and
3. Filtration surgery, last resort.

A. Basic principles of medical therapy of POAG:

1. Identification of target pressure below which glaucomatous damage is not likely to progress.

     Mild to moderate damage: target pressure 12-14mm Hg,

     Severe damage: target pressure, 12-14 mm Hg, even lower in    

     NTG/ LTG.

2. Single drug therapy.
3. Combination therapy.
4. Monitoring of therapy.

Treatment regimens:

1. Single drug therapy:

i.              Topical beta blockers: these lower IOP by reducing aqueous secretion due to their effect on beta receptors in the ciliary processes.

Timolol maleate: 0.25, 0.5%: 1-2 times a day.

C/I: BA or heart block.

ii.            Pilocarpine: 1, 2, 4%- 3-4 times daily.

M/A – contracts longitudinal muscle of ciliary body and opens spaces in trabecular meshwork, thereby mechanically increasing aqueous outflow.

iii.           Latanoprost: 0.005%; once daily

A PG analogue decreases IOP by increasing uveo-scleral outflow of aqueous.

                iv.        Dorzolamide: 2%; 2-3 times a day.

                            Topical CA inhibitor lowers IOP by decreasing aqueous        

                            secretion.

2. Combination topical therapy: If one drug is not effective; Add one drug which decreases aqueous production, e.g.- Timolol, Brimonidine or dorzolamide, and other drug which increases aqueous outflow. E.g.- Latanoprost, Pilocarpine.
3. Role of oral CA inhibitor in POAG: Acetazolamide may be added for short term to control IOP; long term use is not recommended because of their side effects.

B. Argon or diod laser trabeculoplasty (ALT or DLT):

Indication:

-       Uncontrolled IOP despite maximal tolerated medical therapy.

-       As primary therapy where there is non compliance to medical therapy.

C. Surgical therapy:

Indications:

-       Uncontrolled glaucoma despite maximal medical therapy and laser trabeculoplasty.

-       Non compliance of medical therapy.

-       Eyes with advanced cupping and advanced field loss.

-       As a primary line of Rx by some workers.

Type of Surgery:

Fistulizing (Filtration) surgery makes a new channel for aqueous outflow and successfully controls IOP.

TRABECULOTECTOMY IS THE MSOT EFFECTIVE FILTRATION SURGERY FREQUENTLY PERFORMED.

PRIMARY ANGLE CLOSURE GLAUCOMA:

Definition: Type of primary glaucoma wherein there is no obvious systemic or ocular cause, in which rise in IOP occurs due to blockage of aqueous humour outflow by closure of a narrower angle of the AC.

Etiology:

1. PDF risk factors-

i.              Anatomical factors. Anatomically predisposed eyes to develop PACG:

-       Hypermetropic eyes with shallow AC

-       Anteriorly placed iris-lens diaphragm.

-       Eyes with narrow angle of AC may be due to small eyeball, smaller diameter of cornea, relatively larger lens or bigger size of ciliary body.

-       Plateau iris contiguration

ii.            General factors:

-       Age: common in 5^th decade.

-       Sex: F:M=4:1

-       Type of personality: Nervous individuals with unstable vasomotor system.

-       Family history: believed to be inherited.

-       Race: Common in Caucasians, South-East Asians, uncommon in blacks.

2. Precipitating factors:

-       Dim illumination.

-       Emotional stress.

-       Use of mydriatic drugs, atropine, cyclopentolate, Tropicamide, Phenylephrine etc.

Mechanism of rise in IOP:

-       Anatomically predisposed eye.

-       Effect of precipitating factors.

-       Mild dilatation of pupil

-       Increases amount of apposition b/w iris and lens.

-       Relative pupil block

-       Aqueous collects in PC

-       Pushes peripheral flaccid iris anteriorly, iris bombe.

-       Appositional angle closure due to iridocorneal contact,

-       -Rise in IOP begins, may be transient.

-       Appositional angle closure is converted into synechial angle closure: PAS

-       Attack of rise in IOP may last long.

Clinical presentation of PACG:

5 different clinical entities:

   -  Latent PACG (PACG suspect)

   -  Sub acute (Intermittent PACG)

   -  Acute PACG

   -  Post congestive ACG

   -  Chronic PACG

   -  Absolute glaucoma.

LATENT PACG (Suspect):

Symptoms: Absent

Signs:

-       Anatomically predisposed eye.

-       Routine slit lamp examination.

-       Pt. presenting with attack of PACG in one eye.

Diagnosis:

Clinical signs:

Provocative test:

1. Prone-darkroom tests
2. Mydriatic provocative tests: IOP rises > 8 mm Hg, positive.

Treatment: Prophylactic laser iridotomy in both eyes.

ACUTE PACG (ACUTE CONGESTIVE GLAUCOMA):

-       Slight threatening emergency

-       Sudden total angle closure

-       Severe rise in IOP

-       Lasts for many days unless treated.

-       Profound loss of vision.

C/F of acute PACG:

Symptoms:

-       Pain: sudden severe pain in the eye radiates along the branches of 5^th nerve.

-       Nausea, vomiting, and prostration.

-       Rapidly progressive impairment of vision.

-       Redness, photophobia, lacrimation.

-       Past history: about 5% pt, typical previous intermittent attacks of sub acute ACG, coloured halos around light.

Signs:

-       Lids: oedematous

-       Conjunctiva: chemosed and congested. Ciliary and conjunctival congestion.

-       Cornea: Oedematous and insensitive.

-       AC: Shallow, Aqueous flare and cells may be seen.

-       Angle of AC: completely closed seen on Gonioscopy.

-       Iris: discoloured.

-       Pupil: Semi dilated, vertically oval and fixed.

-       IOP: Markedly elevated, b/w 40-70 mm Hg.

-       Optic disc: Oedematous and hyperemic

-       Fellow eye: Shallow AC with narrow angle. Features of latent ACG.

Dx of acute PACG: Obvious from clinical features.

D/D:

1. From other causes of red eye:

i.              Acute conjunctivitis

ii.            Acute iridocyclitis.

2. From secondary ACG:

i.              Phacomorphic glaucoma

ii.            Acute neovascular glaucoma

iii.           Glaucomatocyclitic crisis.

Mx of Acute PACG:

Essentially surgical

Emergency medical therapy to prepare the eye for surgery.

1. Medical therapy:
1. Systemic hyperosmotic agent: IV mannitol, 1gm/kg body wt. to lower IOP
2. Acetazolamide: 500 mg IV followed by250 mg tab 3 times a day.
3. Analgesics and anti emetics
4. Pilocarpine eye drops 2% every 30 minutes for 1-2 hrs and then 6 hrly.
5. Beta blocker: 0..5% Timolol maleate BD
6. Corticosteroid: Betamethasone or dexamethasone 4 times a day to reduce inflammation.
2. Surgical Rx:
1. Peripheral iridotomy (PI) PAS if < 50%, LASER iridotomy is a good alternative.
2. Filtration surgery: IOP not controlled with best medical therapy, PAS is >50%, Trabeculectomy, method of choice.
3. Clear lens extraction by phacoemulsification with IOL implantation has recently been recommended by some workers.

SECONDARY GLAUCOMAS:

- Group of disorders

- Rise of IOP, associated with primary ocular or systemic disease.

- C/F comprises that of primary disease and effects of raised IOP.

PHACOLYTIC GLAUCOMA (LENS PROTEIN GLAUCOMA):

Pathogenesis:

Type of secondary open angle glaucoma in which trabecular meshwork is clogged by the lens proteins and macrophages which have phagocytosed the lens proteins.

Leakage of lens proteins occurs through an intact capsule of hypermature or Morgagnian cataract.

C/F of phacolytic glaucoma:

-       Features of congestive glaucoma, acute rise of IOP, eye having a hypermature cataract.

-       Deep AC, aqueous may contain fine white protein particles.

Mx:

-       Lower IOP by medical therapy.

-       Extraction of lens with PCIOL implantation.

STEROID INDUCED GLAUCOMA:

Secondary open angle glaucoma.

Develops following topical and rarely systemic steroid therapy.

Etiopathogenesis:

-       Steroid responsiveness genetically determined.

-       Rise of IOP after 6wks topical steroid.

-       5% general population, high responders.

Precise mechanism for rise in IOP not known.

Theories are:

1. Glycosaminoglycans (GAG): Accumulation of GAG in trabecular meshwork decreases aqueous outflow.
2. Endothelial cell theory: Suppression of phagocytic activity of living endothelial cells of Schlemm’s cana;.
3. Prostaglandin theory: Steroid inhibits synthesis of PGE and PGF thereby decreases aqueous outflow.

C/F: Resembles POAG, Develops following wks of topical steroid..

Mx:

Treatment:

-       Discontinuation of steroid.

-       Medical therapy: 0.5% Timolol maleate.

-       Trabeculectomy, in intractable cases.

Prevention:

-       Judicious use of steroids.

-       Regular monitoring of IOP when on steroids.