Key points 25

Question 1

What are the associations of optic nerve hypoplasia?

Answer 1

septo-optic dysplasia (de Morsier’s syndrome)
aniridia
fetal alcohol syndrome
maternal exposure to: LSD, quinine, and phenytoin

Question 2

Potential complications of PRP include:

Answer 2

CNVM
tractional RD
ERM
angle-closure glaucoma (secondary to choroidal effusion)
vitreous haemorrhage
nerve fiber bundle defects
incidental foveal burns
retinal vascular occlusions

Question 3

Which modality of treatment uses infrared light:

Answer 3

Transpupillary thermotherapy (TTT) uses infrared light to heat the treated area (up to 40 degrees Celsius). It is used in the treatment of choroidal melanoma.

Question 4

Idiopathic epiretinal membranes are bilateral in what proportion of affected patients?

Answer 4

Epiretinal membranes are bilateral in 10-20% of patients.

Question 5

When tested with a Maddox rod held over the affected eye with its cylinders running horizontally, a patient with new-onset excyclotropia will perceive:

Answer 5

In excyclotropia, the superonasal retinal quadrant is rotated vertically toward the 12-o’clock position, and the inferotemporal quadrant is rotated toward the 6-o’clock position. The vertical line from the Maddox rod will run superonasal to inferotemporal on the retina and be perceived the same way.

Question 6

What is the antidote for the crisis caused by an overdose of edrophonium (Tensilon)?

Answer 6

Tensilon prolongs the effect of acetylcholine in the synaptic cleft, causing a cholinergic crisis (sweating, nausea and vomiting, salivation, fever). Atropine blocks acetylcholine receptor sites on the postsynaptic terminal.

Question 7

What are the features of congenital 4th nerve palsy?

Answer 7

This patient has congenital fourth nerve palsy. Longstanding fourth nerve palsy results in ocular torticollis with a compensatory head tilt away from the side of the palsy that can lead to facial asymmetry of the dependent side.

These patients have large vertical fusional amplitudes that help differentiate them from acquired fourth nerve palsies. (Normal vertical fusional amplitude is 2-3 prism dioptres).

Question 8

The major histocompatibility antigen complex in humans (human leukocyte antigen HLA system) is coded for by genes located on chromosome:

Answer 8

The human leukocyte antigen (HLA) complex governs immune response and surveillance and is encoded for by genes on chromosome 6.

Question 9

The most common primary malignant tumor of the lacrimal sac is:

Answer 9

Lacrimal sac squamous carcinoma