0812 Common Eye Diseases

Question 1

What are the three most common eye diseases in Australia?

Answer 1

Cataracts (31% prevalence in over 55),
Glaucoma,
Age-related macular degeneration
closely followed by Diabetic retinopathy

Question 2

Define vision impairment.

Answer 2

any diagnosed condition of the eye or visual system that cannot be corrected to within normal limits (e.g. by prescription or surgery)

Question 3

What is legal blindness?

Answer 3

A distant visual acuity of 6/60 or worse

Question 4

What is the most common cause of blindness across all ages?

Answer 4

Macular degeneration (48% of cases) followed by glaucoma, cataracts and diabetic retinopathy.

Question 5

What is the most common eye disease in Australia?

Answer 5

Cataracts, present in 70% of Australians over 80 years.

Question 6

Define cataract. What are the 3 different types of cataracts?

Answer 6

Cataract is the loss of lens transparency.
Nuclear cataract (hardening of the core of the lens due to glutathione adducts)
Cortical cataracts (begins at margins of lens)
Capsular cataracts (affects capsule of the lens, often subsequent to eye damage)

Question 7

Why could the vision be more reddish and blurry in an individual with cataracts?

Answer 7

Because the yellow brunessence, accumulation of glutathione adducts, reduce the transmission of blue light and increase scatter.

Question 8

Describe the effect of cataracts within the Aboriginal and Torres Strait Islanders population.

Answer 8

ATSI are 3x more likely to be affected by vision loss due to cataracts tan non indigenous, due to barriers of cataract surgery existing in health-service, community and individual levels. Health service factors include infrastructure, cost, interpreters and transport. Community and individual factors include ignorance of cause and fear of surgery.

Question 9

Describe any sex discrepancy in the prevalence of cataracts.

Answer 9

Oestrogen is protective against cataracts, therefore prior to menopause there is higher prevalence in M>F, though becomes roughly equal over the typical menopause years and then the trend reverses so F>M in older years.

Question 10

Define glaucoma.

Answer 10

a spectrum of related disorders characterised by progressive loss of ganglion cells and their axons (optic nerve) it is an anterior segment disorder that has its impact on the posterior segment, and is strongly associated with increased intraocular pressure (IOP) in (50% of cases).

Question 11

Contrast open angle glaucoma to closed angle.

Answer 11

In open angle proteins accumulate in the trabecular meshwork of the canal of Schlemm, preventing reabsorption of aqueous humour.
In closed angle the pressure of fluid build-up pushes the iris forward against the canal of Schlemm, blocking the trabecular meshwork and preventing reabsorption.

Question 12

How is glaucoma initially diagnosed?

Answer 12

By assessment of the optic disc. A normal disc has a distinct margin, in glaucoma the margin becomes eroded, often inferiorly, disc becomes enlarged, and a shallow cupping of the disc also increases over time with progression of the disease.

Question 13

In glaucoma, where does the vision loss tend to start from?

Answer 13

Start from the peripheries (hence can easily go undiagnosed for some time)

Question 14

In macula degeneration, where does the vision loss tend to start from?

Answer 14

Central visual field lost first.

Question 15

List some of the signs of AMD.

Answer 15

drusen or white spots (in the retina), areas of cell loss on the macula, basal laminar deposits between the BM and RPE (prevent blood supply from the choroid)

Question 16

Contrast dry to wet AMD.

Answer 16

In dry AMD there is loss of photoreceptors and RPE in macula with a sharp transition from normal to abnormal.
In wet AMD there is a breakdown of Bruch’s membrane (BM) and sprouting of choirodal vessels which breach BM and often the RPE, leaking fluid into the eye.

Question 17

List environmental factors that increase the risk of age-related macular degeneration (AMD).

Answer 17

Smoking (increases risk by ~3X),

Poor diet, particularly high intake of saturated fat (conversely good fatty acids decrease risk)

Question 18

What are the 2 highly significant loci that are a genetic factor in the development of AMD?

Answer 18

Complement Factor H (CFH), which is involved in complement regulation and innate immune system, presence increases risk and deletions decrease risk.
HTRA1.