Important causes of sudden visual loss in an uninflamed eye are vitreous hemorrhage, including due to proliferative diabetic retinopathy; retinal detachment; neovascular age-related macular degeneration; retinal vein occlusion; retinal artery occlusion and anterior ischemic optic neuropathy, either possibly due to giant cell arteritis; and optic neuritis. All these conditions require urgent ophthalmologic consultation. Giant cell arteritis requires emergency treatment.
Sudden loss of vision in an inflamed eye may be due to acute glaucoma or corneal ulcer, both of which require emergency treatment, or acute anterior uveitis, which requires urgent ophthalmologic assessment. Other emergencies include orbital cellulitis, gonococcal keratoconjunctivitis, and ocular trauma.
Patients with gradual loss of vision should also be referred. The principal causes are cataract, atrophic age-related macular degeneration, chronic glaucoma, diabetic maculopathy, chronic uveitis, and intraorbital and intracranial tumors.
Patients with diabetes must undergo at least annual examination for retinopathy, even in the absence of visual symptoms. Any patient with nearsightedness should be warned of the increased risk of retinal detachment and made aware of the importance of reporting relevant symptoms. Screening for glaucoma should be targeted at individuals at high risk.
Algorithms improve accuracy of diagnosis by non-ophthalmologists.
et al. The accuracy of the Edinburgh Visual Loss Diagnostic Algorithm. Eye (Lond). 2015 Nov;29(11):1483–8.
et al. The accuracy of the Edinburgh Red Eye Diagnostic Algorithm. Eye (Lond). 2015 May;29(5):619–24.