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Glaucoma

Dr Rajesh Varma

Definition

Glaucoma is associated with

  • raised intraocular pressure (IOP) and characterized by:

  • visual field defects

  • changes to the optic nerve head such as pathological cupping or pallor of the optic disc.

Key aspects of treatment

  • If a primary healthcare professional suspects a chronic glaucoma, they should refer the person to an optometrist or ophthalmologist.

  • The diagnosis is usually made by an optometrist during routine eye examinations. Typical features that may be detected by an optometrist are: increased IOP, visual field defects, a cupped optic disc, and signs of angle closure as detected by gonioscopy. 

  • The main complication of untreated glaucoma is irreversible loss of vision (partial or complete).

  • Treatment of all types of glaucoma, and of ocular hypertension when indicated, is normally initiated and monitored by specialists.

  • The mainstay of treatment is to reduce IOP.

  • The anterior chamber angle between the iris and cornea: being either open or closed.

  • A pressure between 11–21 mmHg is considered normal. However, some people develop glaucoma at a pressure below 21 mmHg, and some people have pressures well above this level without showing signs of glaucoma.

  • This is usually done with eye drops but sometimes laser or surgical treatments (laser iridotomy) are required.

Ocular hypertension

OH is consistently or recurrently raised IOP (>21mmHg) but with no signs of glaucoma (no signs of visual field defect or optic nerve head damage).
It affects 3-5% of people in the UK over 40 years. It requires monitoring as it may progress to glaucoma.

Conversely, optic nerve head damage may occur in a minority of people with normal IOP: Normal tension (pressure) glaucoma occurs in a significant minority of people with POAG where glaucoma develops with normal IOP. It seems that the optic nerve fibres are more susceptible to damage in some people with intraocular pressures considered to be normal.

Risk factors

Primary open angle glaucoma (POAG)

  • Raised intraocular pressure

  • Age

  • Family history

  • Black ethnicity

  • Corticosteroids

  • Eye size: long eyeball length (myopic/short-sightedness vision)

  • Type 2 diabetes mellitus

  • Hypertension and cardiovascular disease

Primary angle-closure glaucoma (PACG)

  • Age

  • Female sex

  • Asian ethnicity

  • Eye size: short eyeball length (hypermetropic/long-sightedness vision)

  • Family history

In open angle situations, the angle between the iris and the cornea is normal.

Primary open angle glaucoma (POAG)

POAG the most common type which mainly affects older people, occurring in about 2% of people in the UK over 40 years.

  • Is usually insidious in onset, and follows a chronic course.

  • Usually affects both eyes.

  • Is typically associated with raised IOP

In angle closure situations, the angle between the iris and the cornea is at least partially closed.

Primary angle closure glaucoma (PACG)

Primary angle closure glaucoma (PACG) mainly affects older people, occurring in about 0.4% of people in the UK over 40 years.

Risk factors include being female, Asian, long-sighted, or of older age.

Most people with PACG have asymptomatic chronic PACG.

Acute angle closure (URGENT ophthalmology assessment)

Acute angle closure (which may quickly progress to glaucoma) should be suspected with the following acute onset symptoms and signs:

Symptoms

Unilateral eye pain- severe
Photophobia

Headache, nausea and vomiting
Unilateral red eye
Blurred vision (lights are seen surrounded by haloes)


Signs

reduced visual acuity

ciliary injection

Fixed/mid-dilated pupil which is unresponsive to bright light: classically, pupil develops a vertically oval shape

Tender and hard eye (checked by mild digital pressure and measurement of intra-ocular pressure)

A precipitating factor such as
watching television in a darkened room
adopting a semi-prone position (for example, reading)
use of an adrenergic drug (for example phenylephrine or pupil-dilating phenylephrine)
use of an antimuscarinic drug (for example a tricyclic antidepressant).

Emergency treatment should be started in primary care if immediate admission is not possible.

  1. The person should lie flat with their face up and head not supported by pillows.

  2. Pilocarpine drops should be administered - one drop of 2% in blue eyes or 4% in brown eyes

  3. Oral acetazolamide 500 mg (if no contraindications)

  4. Analgesia and an anti-emetic provided, if required.

Drug treatments

Drugs used to treat glaucoma aim to reduce IOP and work by either reducing the production of aqueous humour, or increasing its outflow.

  1. A topical prostaglandin analogue (Latanoprost Travoprost, Bimatoprost)

  2. A topical beta-blocker (Timolol)

  3. Combining a topical prostaglandin analogue with a topical beta-blocker (Bimatoprost and timolol — Ganfort®, Latanoprost and timolol — Xalacom®, Travoprost and timolol — DuoTrav®)

  4. ADDING
    Topical sympathomimetic (Brimonidine tartrate 0.2%) , OR
    Topical carbonic anhydrase inhibitor (Brinzolamide, Dorzolamide; Dorzolamide and timolol 0.5% — Cosopt®)

  5. Laser or surgical procedures.

  • Selective laser trabeculoplasty (SLT) Argon laser trabeculoplasty (ALT), Micropulse laser trabeculoplasty (MLT).

  • Trabeculectomy

  • Insertion of a drainage shunt through the sclera into the anterior chamber.