Myth.

The Pharmacy Department at Repatriation General Hospital in Daw Park (Adelaide) in South Australia have recently published a very interesting bulletin on the systemic effects of topical ophthalmic preparations.

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Central retinal vein occlusion

With thanks to Yusuf.

Causes: thrombosis of the central retinal vein due to venous stasis secondary to diabetes / hypertension  / cardiovascular disease; hypercoagulable states; vasculitis; glaucoma; compression of the central retinal vein in orbital pathology (tumour, thyroid exophtalmos)

– 2 types – perfused (nonischaemic) – 75%, and nonperfused (ischaemic) – 25%

Symptoms: monocular loss of vision that develops over minutes; painless; the degree of vision loss is variable, milder in non-ischaemic CRVO and severe in ischaemic CRVO

Examination: decreased VA; prominent afferent pupillary defect in ischaemic CRVO; fundoscopic exam: diffuse retinal hemorrhages and optic disc edema (the “blood and thunder” fundus) and tortuous retinal veins with cotton wool spots.

Complications are delayed and include neovascularization of the retina and iris and neovascular glaucoma.

There is no known effective medical treatment available. They all need urgent Ophtalmology referral and medical workup for the underlying cause.

Central retinal artery occlusion

With thanks to Yusuf.

The central retinal artery is the first branch of the ophtalmic artery, which is the first intracranial branch of the internal carotid artery.

Causes

emboli – thrombotic, fat, amniotic fluid, air – AGE

thrombosis

vasculitis

compression in the orbit – retroorbital haematoma; thyroid exophtalmos

trauma

sickle-cell crisis

Symptoms: severe loss of vision that develops over seconds; painless

Examination: decreased VA; prominent afferent pupillary defect; fundoscopic exam: macular cherry red spot (fovea – sparred) with a pale retina and less pronounced arteries

Treatment: depends on the cause

Thromboembolic causes: aim to dislodge the clot from the main artery to one of its branches:

–  digital massage (digital pressure through closed eyelids for 10 – 15 sec then sudden release)

– vasodilation (by increasing pCO2 – rebreathing into a paper bag)

– lowering intraocular pressure – topical Bblockers; iv acetazolamide; anterior chamber paracentesis

Vasculitis: corticosteroids (1 – 2 weeks to loss of vision in the other eye if not treated)

Sickle-cell crisis: iv fluids, reverse precipitant cause

Decompression sickness: hyperbaric therapy

They all need urgent Ophtalmology referral.

Causes of unilateral vision loss

Painful

• acute angle-closure glaucoma
• optic neuritis
• open-globe injuries
• orbital cellulitis / endophtalmitis / panophtalmitis

 Painless

• central retinal artery occlusion (CRAO)
• central retinal vein occlusion (CRVO)
• retinal detachment
• retinal break
• vitreous hemorrhage
• macular disorders (macular degeneration / trauma / infective – toxoplasmosis, CMV)
• optic nerve ischaemic neuropathy (giant cell arteritis, diabetes, compression by mass)
• optic nerve toxic neuropathy (methanol)
• chiasmal visual loss – pituitary tumours / craniopharyngioma / meningioma
• neuro-ophtalmologic causes (pathology involving post-chiasmal optic tract – occipital lobe: infarction / tumour / AVMs)
• functional (hysteria / malingering)

With thanks to Yusuf.