Introduction
Can be due to a variety of factors:
- Pseudoexfoliation
- Pigmentary dispersion
- Neovascularisation
- Trauma
- Steroids
- Uveitis
Pseudoexfoliation Syndrome
- Deposition of extracellular, fibrillar material in the body, which can occur in eyes, liver, lungs and kidneys
- Prevalence increases with age, affecting 5-20% of people >60 years
- Highest in Northern Europeans.
- The most common cause of SOAG
- The material and pigment deposition obstruct aqueous outflow, leading to IOP rise. This causes glaucomatous optic nerve damage.
Pigment Dispersion Syndrome
- Prevalent in 2% of the population, usually diagnosed at age 20-40, affecting males and females. Associated wtih myopia
- About 20-50% develop glaucoma
- Primarily due to the posterior bowing of the iris, creating a concave shape that rubs against the lens and lens zonules.
- This is known as a reverse pupillary block, as the contact between the iris and lens causes increased pressure in the anterior chamber.
1. Pigment overload at TM endothelial cells cause dysfunctional aqueous outflow
2. TM cells die, collapsing the outflow channel
3. IOP elevates causing pigmentary glaucoma
4. Burnout regresses the pigmentary glaucoma as the iris moves away from the zonules, decreasing IOP and then removing pigmentation
Neovascular Glaucoma
- Primarily due to iris neovascularisation and angle fibrovascular membrane due to VEGF release
- Increase IOP due to obstruction of outflow
- Glaucomatmous neuropathy onset and optic nerve damage
- The neovascularisation usually starts at the pupillary border, before migrating to the angle. The fibrovascular tissue contracts, causing angle closure through anterior synechiae.
Angle Recession Glaucoma
- Follows blunt trauma, such as sports and assault.
- Widening of the angle occurs due to tear in longitudinal and ciliary muscles.
- About 6% develop glaucoma
- Higher risk if >180 degrees of recession
Steroid Related Glaucoma
- Follows from periocular, topic, intravitreal or intravenous administration of steroids or corticosteroids
- Amount of IOP increase and onset related to potency, dosage, duration, route of administration
- Inhibited degradation of ECM in TM (such as glycosaminoglycan, fibronectin, elastin, collagen)
- Decreased outflow facility due to ECM accumulation, leading to swelling, narrowing and increased resistance
- Only glaucoma if IOP rise, ON and VF defects
Uveitic Glaucoma
- 10-46% have increased IOP
- 10-20% develop secondary glaucoma
- Reduced aqueous outflow from damaged ciliary body and also increased uveoscleral outflow
- ECM material accumulates in TM
- TM undergoes inflammation
- Steroid therapy for uveitis makes glaucoma worse
Dead Giveaways
Pseudoexfoliation Syndrome: (Refer to pseudoexfoliation in anterior eye diseases)
White flaky substance on the anterior lens capsule, pupillary border and occasionally corneal endothelium
Also found on the zonules and ciliary body
Two concentric rings form, with a region of no flaky substances due to rubbing.
The pigmentary deposits occur on the corneal endothelium, trabecular meshwork, and Schwalbe's line (Sampaolesi line)
Pigmentary Dispersion Syndrome: (Refer to PDS in anterior eye diseases)
Pigmentary cells appear on the corneal endothelium, forming thin pigmentary lines known as Krukenberg Spindles
Iris transillumination defects in the periphery/mid-periphery has a spoke like pattern
Increased pigmentation of TM
Angle Recession Specific Pathophysiology:
Initially, following trauma, IOP falls due to decreased aqueous production
2 weeks or so later, accumulation of blood, inflammatory cells and pigment will cause an IOP rise at the angle
Chronic TM scarring and fibrosis occur, damaging the ciliary body which controls aqueous ouflow. This causes IOP to rise
Glaucoma then affects the contralateral eye (50%)
diagnostic features
Neovascular Glaucoma
A very severe and aggressive subset of glaucoma with very poor visual prognosis, characterised by the neovascularisation and fibrovascular membrane formation on the anterior iris and angle
Typically associated with posterior segment ischaemia
CRVO (2 weeks -> 2 years but more commonly 3 months)
Proliferative DR
Ocular ischaemic syndrome
CRAO (as early as 2 weeks)
Angle Recession Glaucoma
Can occur within weeks to 10 years
Is glaucoma ONLY IF damage to ONH and rise in IOP is observed
Steroid Induced Glaucoma
66% of population has <6mmHg of increase in IOP (low)
29% of population has 6-16mmHg of increase in IOP (intermediate)
5% of population has >16mmHg of increase in IOP (high)
Risk:
Glaucoma, suspect or family history
High myopia
Rheumatoid arthritis
T1DM
Children < 6years
Older people > 65 years
Uveitic Glaucoma:
Higher risk in chronic uveitis
Posner-Schlossman syndrome (recurrent attacks of mild acute uveitis)
Fuch's heterochromic iridocyclitis
HSV/VZV uveitis
Acute causes high IOP (herpetic + Posner-Schlossman)
Chronic causes gradual IOP rise over time (HLA-B27 associated)
Chronic causes high IOP first that gradually decreases over time (Fuch's)