Primary Open-Angle Glaucoma

Professor K N Jha,MS

Learning Aim

• Definition of Open-angle glaucoma

• Primary open-angle glaucoma (POAG)

• Clinical features (IOP, fundus, and field

changes) of POAG

• Treatment of POAG

Primary open-angle glaucoma(POAG)

-POAG is characterized by a chronic, slowly

progressive, optic neuropathy with a

characteristic pattern of optic nerve damage

and visual field loss.

-Angle of the anterior chamber is open.

-There are no ocular or systemic disorders.

POAG Risk factors• IOP • Race • Central corneal thickness ( CCT) • Age • Family history• Systemic and ocular associations: DM, Myopia,

HTN, CRVO

POAG: Contributory factors

• Reduced perfusion of the optic nerve head- Inadequate auto-regulation in blood vessels- Mechanical compression of capillaries

• Abnormality of axonal , or ganglion cell metabolism

• Disorders of the extracellular matrix of lamina

cribrosa.

Pathogenesis

• Increased resistance to aqueous outflow• Mechanical changes due to raised IOP

- Decreased axoplasmic flow• Optic nerve head vascular perfusion

- Inadequate autoregulation in blood vessels- Mechanical compression of capillaries

• Glaucomatous Optic atrophy

POAG: Clinical features

• Onset : Insidious, • Slowly progressive, and painless• Bilateral: initially may manifest in one eye.• Visual acuity remains unaffected until late• Diagnosis : IOP, visual fields, and optic disc

appearance.• Gonioscopy: open angles• Associations: myopia, DM, CVS disease, CRVO

Diagnosis

Characteristic optic nerve head changes

Visual field changes

Raised Intraocular pressure (IOP)

At least two of the above three.

Optic disc(ONH) changes in glaucoma

• Increased vertical cup : disc ratio

• Asymmetry of cups between two eyes

• Notching and pallor of neuroretinal rim(NRR)

• Disc hemorrhage

• Baring of circumlinear vessels

• Peripapillary retinal atrophy

Optic Nerve head changes

Normal fundus oculi Glaucomatous cupping

Visual field changes in glaucoma

• Relative paracentral scotoma: smaller/ dimmer targets are not visualized.

• Nasal step: appearance of horizontal shelf in nasal visual field

• Seidel scotoma: starting from one pole of blind spot and arches over macula without reaching horizontal meridian nasally.

• Arcuate scotoma• Double arcuate or ring scotoma• End-stage or near total field defect

POAG : Management

• Early detection and routine screening

• Meticulous documentation: IOP, optic nerve

damage and risk factors

Primary open-angle glaucoma

Treatment goal

• Modify and slow progression of optic nerve

damage.

• To lower IOP

Target pressure

• It is a range of IOP with an upper limit that is

unlikely to lead to further damage.

• Initial reduction: 20% from baseline.

• Target pressure need constant reassessment

dictated by IOP fluctuation , ONH changes,

and/or visual field progression.

Target pressure

Depends on -Initial IOP-Severity of damage-Life expectancy-Associated risk factors like , family history.

POAG: Management

• Patient education

• Cost and Compliance

• Medical or surgical therapy

• Progression and follow-up

POAG: Management

Modalities of treatment

Drug therapy

Laser

Surgery

POAG: Medical Therapy

Topical :

-Parasympathomimetics

-Adrenergic antagonists : beta-blockers

-Sympathomimetics: alpha-2 agonist

-Prostaglandin analogues and hypotensive lipids

CAH inhibitors : Acetazolamide, dorzolamide, brizolamide

Hyperosmotic agents

Primary open-angle glaucoma

• Laser therapy: Argon-laser trabeculoplasty

• Glaucoma surgery: Trabeculectomy

POAG: Prognosis

• Most patients will retain useful vision for their

entire life

• Incidence of blindness at 20 years follow-up is

27 % unilateral, 9 % bilateral.

Primary open-angle glaucoma

Summary:• Clinical features• Fundus changes• Field changes• Diagnosis• Treatment• Follow-up