Which ONE of the following conditions is NOT a cause of acute painless uniocular visual loss?
Answer: B: In optic neuritis, the eye pain is associated with unilateral visual loss or reduction in over 90% of patients. It is an acute demyelinating condition affecting the optic nerve and a large proportion of these patients develop multiple sclerosis subsequently. Other causes include viral infections (measles, mumps, varicella, Epstein-Barr virus), bacterial infections (tuberculosis, cryptococcus, syphilis), sarcoidosis, post vaccination in children, and idiopathic. Eye pain with eye movements and afferent pupillary defect are typical features in optic neuritis. Visual acuity in the affected eye could be greatly decreased and colour vision may be affected. Although the classic visual field defect is central scotoma, other focal visual field defects may be found. Features of optic disc swelling (anterior optic neuritis) can be seen in approximately one-third of patients. In others the optic disc will appear normal (retrobulbar neuritis). The symptoms will improve over the course of several weeks even without treatment. Use of intravenous steroids is controversial.
All the other conditions cause painless acute visual loss.
References:
Regarding assessment and management of central retinal artery occlusion (CRAO) and central retinal vein occlusion (CRVO), which ONE of the following statements is INCORRECT?
Answer: C: In both CRAO and CRVO the unilateral visual loss is abrupt and painless. In CRVO the visual loss may be present when the patient wakes up in the morning. It can range from blurred vision to complete loss. Optic disc and diffuse retinal haemorrhages can occur in CRVO (in contrast to optic neuritis) due to venous stasis oedema, hence the term ‘blood and thunder’ has been given to this appearance on funduscopy. Unlike in papilloedema, the unaffected fundus appears normal. Immediate referral to the ophthalmology is indicated in CRAO but there is no specific treatment available for CRVO, and a patient with CRVO can be seen by ophthalmology within a few days. The medical therapies, which are described, can be used in the ED for CRAO; however, they have not been shown to be highly beneficial.
Regarding central retinal artery occlusion, which ONE of the following statements is TRUE?
Answer: A: CRAO is an ischaemic stroke involving the retina due to emboli. Carotid artery atherosclerosis is present in approximately half of the patients and a cardiac source for embolism is found in up to 20% of cases. The features include:
CRAO is devastating to the vision. Less than one-third of patients recover to gain a reasonable visual acuity in spite of adequate emergent care. The recommended emergent care is aimed at increasing perfusion to the retina and dislodging the clot. They include:
None of the above therapies have been investigated for their effectiveness. Both intravenous and intraarterial thrombolysis have been attempted but currently there is not enough evidence to support or refute their use.
A 65-year-old woman presents to the ED with an isolated dilated pupil on the left side. There is no history of significant head injury. All of the following are likely causes of her isolated dilated pupil EXCEPT:
Answer: C: Horner’s syndrome causes constriction of the pupil on the affected side. It occurs due to damage to the sympathetic fibres on the affected side. Therefore, the affected pupil is constricted and the normal pupil on the opposite side may appear ‘dilated’. Isolated third nerve palsy presenting as an isolated dilated pupil (without ophthalmoplegia and/or ptosis) is a rare event. More common emergency presentations of an isolated dilated pupil include:
Up to 20% of the population have minor (up to 1 mm difference) anisocoria. Adie’s tonic pupillary defect affects more females (70%) than males. In this condition parasympathetic fibres are affected after leaving the ciliary ganglion. Adie’s tonic pupil presents as an isolated dilated pupil on the affected side. It affects the accommodation of the eye, therefore the patient may have blurred near vision with relative sparing of the distant vision. Half of these patients usually will recover within 2 years. Orbital blunt trauma can cause mydriasis. Acute angle closure glaucoma is another cause of isolated dilated pupil.
Isolated third nerve palsy can be classified based on ‘the rule of the pupil’:
Patients presenting with pupil-involving isolated third nerve palsy should be urgently imaged using MRI/ MRA or CT angiography to diagnose posterior circulation aneurysms and also to identify an alternative cause when an aneurysmal cause is not present. Posterior circulation aneurysms have the highest rates of rupture (2.5–50% per year) among all the cerebral aneurysms.
Reference:
Regarding ED management of acid and alkali injuries to the eye, which ONE of the following is the LEAST appropriate option?
Answer: A: Unless strong acids and alkali are involved, initial examination and visual acuity are often normal. Even with strong acids rapid complete loss of epithelium of the cornea may occur and this may mask the severity of the injury. Most ophthalmologists advise continuous irrigation with normal saline until normal pH is restored. The pH should be checked every 30 minutes while irrigation is done and 30 minutes after the restoration of normal pH. This is especially important in an alkali injury because further injury may occur from alkali deposited in the inaccessible areas of the conjunctival sac. (There is a wide variation in normal tear pH – approximately 6.5–7.5 – and this is partly dependent on the measurement technique as well. Except very minor exposures all patients should be referred for ophthalmology follow-up as initial assessment may not reveal the full extent of the injury.
Click to expand