7.2 Common eye diseases

Question 1

Define visual impairment

Answer 1

Any diagnosed condition of the eye or visual system that cannot be corrected to within normal limits

Question 2

What are the most common causes of reading difficulty?

Answer 2

Refractive error
Cataract
Macular degeneration
Glaucoma

Question 3

What is the most common eye disease in Australia?

Answer 3

Cataracts

Question 4

What is cataracts?

Answer 4

a loss of transparency of the lens

Question 5

What is a nuclear cataract and what will it cause?

Answer 5

Hardening of the core of the lens that expands through the layers

Causes reduced transmittance of light (esp blue), increased scatter and increased fluorescence. Things will appear more red and blurry

Question 6

What are cortical cataracts?

Answer 6

Changes to the lens proteins that start at the margin of the lens, and spread through the more superficial layers towards the optic axis

Question 7

What are capsular cataracts?

Answer 7

Modification of the lens capsule anteriorly or posteriorly which can occur subsequent to eye surgery

Question 8

Who is more likely to have cataracts and why?

Answer 8

ATSI people (3 x more likely) 
Barriers to treatment, lack of health service, ignorance of cause, fear of surgery, difficult to access treatment as a public patient

Question 9

What is glaucoma?

Answer 9

A collection of disorders characterised by progressive loss of ganglion cells (GCs) and their axons (optic nerve)

Question 10

What is the second leading cause of blindness in the world?

Answer 10

Glaucoma

Question 11

What happens in increased IOP glaucoma?

Answer 11

The increased IOP in the anterior segment is transferred posteriorly through the vitreous. Pressure distorts the sclera at the lamina cribrosa, compressing the ganglion cell axons leading to GC death

Question 12

What causes GC loss in glaucoma?

Answer 12

Decline in the retrograde supply of neurotrophins to GC from their axon terminals

Release of excitotoxic amino acids by damaged GC cells

Apoptotic cell death

Question 13

Why does glaucoma present late

Answer 13

Tends to first affect peripheral vision ad these losses are compensated for by eye movements so go unnoticed

Question 14

What will be the appearance of the optic disc in glaucoma?

Answer 14

The margin appears eroded, often inferiorly
The disc appears enlarged and the area of pallor increases
The normal hallow cupping of the disc increases over time with progression of the disease

Question 15

What is closed angle glaucoma?

Answer 15

Pressure on the posterior aspect of the iris causes the iris to buckle, compressing the trabecular meshwork and restricting the drainage of the aqueous humour

Question 16

What is open angle glaucoma?

Answer 16

The trabecular meshwork and drainage network can become clogged and restrict the passage of aqueous humour

Question 17

What causes the changes on the disc and fundus?

Answer 17

Associated with progressive visual field loss, due to death of ganglion cells, resulting from compression of their axons

Question 18

What happens in macular degeneration?

Answer 18

There is a loss of central vision due to degeneration of the photoreceptors, specifically those in the macular region

Question 19

What will you see in dry AMD?

Answer 19

Drusen/white spots

Areas of cell loss, centred on the macula

Question 20

What are the principle cell types affected in AMD?

Answer 20

Light sensitive photoreceptors and their supporting pigmented epithelial cells

Question 21

What are the signs of emergent AMD?

Answer 21

Sub retinal deposits which prevents oxygen filtration to the photo receptors
Pigmentary disturbance
Drusen

Question 22

what is the histopathology in dry/non-exudative AMD?

Answer 22

Loss of photoreceptors and RPE cells in the macular regions
Accumulation of leucocytes in the choriocapillaries
Sharp transition into histologically normal photoreceptors

Question 23

What is the histopathology of wet/exudative AMD?

Answer 23

Breakdown of Bruch’s membrane by phagocytic cells
Sprouting of choroidal vessels which breach Bruch’s membrane and often the RPE
Choroidal neovascularisation of the retina
New choroidal vessels leak serum constituents and blood cells into outer retina promoting retinal dysfunction and loss of vision
Bleeding into retina proper

Question 24

What increases the risk of AMD?

Answer 24

Smoking

High fat and cholesterol

Question 25

What decreases the risk of AMD?

Answer 25

Hight fatty acid intake

Eating fish 1/wk

Question 26

What are the 2 genetic loci associated with AMD?

Answer 26

1q32 complement factor H

10q26

Question 27

What is the clinical diagnosis of AMD?

Answer 27

Recognition of end state degeneration of neural tissue