Ophthalmology: acute loss of vision Flashcards
DDx for acute loss of vision Unilaterally
Amaurosis fugax Central retinal artery occlusion Central retinal vein occlusion Vitreous haemorrhage Retinal detachment GCA Optic neuritis Non-arteritic ischaemic optic neuropathy
DDx for acute bilateral loss of vision
severe bilateral papilloedema (malignant HTP and highr ICP)
rapid progression of lesion compressing optic chiasm
bilateral infarcts in occipital lobes
Bilateral optic nerve damage: methanol
bilateral optic neuritis - rare
NON-ARTERITIC ANTERIOR ISCHAEMIC OPTIC NEUROPATHY is caused by?..
is caused by occlusion of the short posterior ciliary arteries. This results in infarction of the optic nerve head.
risk factors for nAION
- Male
- Systemic arteriopathy
- 40-60 years of age
- Small hypermetropic optic discs
- Hypertension
- Diabetes
Hx Ex for nAION
- Establish when vision loss occurred and in which eye
- Assess cardiovascular risk factors
- Exclude features of giant cell arteritis
- Palpate the temporal artery (unlike GCA expect them to be palpable and non tender)
- Measure visual acuity
- Examine the pupil reactions for an RAPD
- Test visual fields (typically unilateral altitudinal hemianopia)
- Examine the optic discs with an ophthalmoscope, ideally dilated.
Features of nAION
- Painless, monocular, sudden loss of vision
- Sometimes asymptomatic if good vision in fellow eye (as can still see)
- Moderate to severely ↓ visual acuity in affected eye (typically 6/12 to 6/60)
- A sector or all of the optic nerve may be swollen with splinter or flame shaped haemorrhages
- Relative afferent pupillary defect
- Visual field defect corresponding to the area of optic disc swelling. The most common is an inferior altitudinal defect
Mx of nAION
Refer to Ophthalmology urgently, to exclude giant cell arteritis with examination /ESR/CRP
Review and treat all cardiovascular risk factors
Consider aspirin
Prognosis of nAION
30% make substantial improvement (gain of 3 lines on a Snellen vision chart)
15-50% risk to fellow eye
The optic disc swelling gradually resolves, leaving optic disc pallor (due to loss of neural tissue)
what is GCA
It usually effects >50 y/o females
GCA is a vasculitis of the medium and large arteries. It often affects arteries around the temple, scalp, head and neck. The optic nerve head blood supply is compromised, producing anterior ischaemia optic neuropathy. Therefore it has a similar presentation to non-arteritic anterior ischemic optic neuropathy, but is more likely to have pain and raised ESR/CRP
Sx of GCA
- Sudden painful severe monocular loss of vision, possibly preceded by transient episodes of vision loss
- Headache
- Scalp tenderness
- Jaw claudication
- Loss of appetite
- Weight loss
- Visual acuity often severely reduced e.g. count fingers
- Usually non-pulsatile tender temporal arteries
- Swollen optic disc & RAPD
- May have flame shaped haemorrhages & cotton wool spots indicating retinal nerve fibre layer infarction
Mx of GCA
- Emergency referral to ophthalmology
- Inflammatory markers (ESR/CRP)
- High-dose systemic steroids
- Temporal artery biopsy, usually within no more than a few days of starting steroids
Aqueous humor physiology
Aqueous production and drainage is balanced to maintain an appropriate intraocular pressure. Aqueous humor is produced by the ciliary body in the posterior chamber. It circulates to the anterior chamber, through the pupil, and leaves the eye through the trabecular meshwork.
mechanism of AACG
Usually caused by failure of aqueous humor to pass through the pupil and drain out through the trabecular meshwork.
This can be caused by:
The iris being pushed forward against the trabecular meshwork
A pupil-block, whereby the aqueous fails to pass through the pupil
The result is often markedly raised intraocular pressure.
A glaucomatous optic neuropathy can follow→severe & permanent vision loss.
Usually presents with acute, painful loss of vision.
Caused by an acute rise in IOP
risk factors for acute angle closure glaucoma
- Hypermetropia
- Family history
- Narrow anterior chamber angles
- Age >30 years of age
- Race
- Women
Sx of acute angle closeure glaucoma
Sx • Unilateral loss of vision (can be 6/36 or worse) • Halos around lights • Unilateral red eye • Painful eye • Nausea and vomiting • Can be asymptomatic • +/- previous intermittent symptoms Reduced visual acuity Corneal oedema ↑ IOP (eye may feel ‘rock hard’ to palpation through lids) Oval unreactive pupil Hypermetropia (the anterior chamber is shallower and hence greater susceptibility to AACG)
