Gradual visual loss

Gradual visual loss is reduction in vision developing over weeks to years. It is usually painless and often bilateral. Most cases are due to refractive error, cataract, glaucoma, age related macular degeneration or diabetic retinopathy.

Clinical relevance. Visual impairment is a leading cause of falls, fractures, social isolation, depression and loss of independence. Many causes are treatable or preventable if found early, and glaucoma damage is irreversible.

Anatomy. Loss may arise from media opacity (cornea, lens, vitreous), retinal disease (macula, peripheral retina), optic nerve disease, or visual cortex disease.

Classification. Media and refractive causes, macular disease (central loss), optic nerve disease (colour and contrast loss, field defects), peripheral retinal disease (night blindness, tunnel vision), and neurological causes.

Key distinctions. Improvement with pinhole indicates refractive error or early cataract. Central distortion points to macular disease. Gradual peripheral field loss with a normal central acuity points to glaucoma or retinal dystrophy. Painless progressive loss with colour desaturation and an afferent pupillary defect points to optic nerve compression, until proven otherwise.

History. Rate of progression, central or peripheral loss, glare, difficulty at night or with dim light, haloes around lights, distortion, colour vision change, double vision, headache, and family history (glaucoma, macular degeneration, retinal dystrophy). Also ask about diabetes, hypertension, smoking, previous eye surgery, steroid use, trauma, systemic disease, nutritional status, alcohol, and functional impact (reading, driving, face recognition, falls).

Drug history. Corticosteroids (cataract, glaucoma), hydroxychloroquine and chloroquine, amiodarone, ethambutol, tamoxifen, phenothiazines (thioridazine), vigabatrin, topiramate, and antimuscarinic drugs.

Examination. Visual acuity (near and distance, pinhole), colour vision, contrast sensitivity, pupils, confrontation fields, intraocular pressure, slit lamp (cornea, lens opacity grade), gonioscopy by ophthalmology, dilated fundus examination (disc cupping, pallor, macular drusen, haemorrhage, exudate, pigment), Amsler grid, blood pressure, and neurological examination including cranial nerves.

Red flags

• Progressive monocular loss with relative afferent pupillary defect and disc pallor (compressive optic neuropathy)
• Bitemporal or other field defects, headache, endocrine features (pituitary tumour)
• Papilloedema with transient visual obscurations
• Rapid change in central vision with distortion (wet macular degeneration)
• Loss in a child, white pupil or squint
• Progressive loss with neurological signs or cognitive change
• Diabetes with poor control and no retinal screening
• Age over 50 with headache and jaw claudication
• Night blindness with skin and mucosal dryness (vitamin A deficiency)

Special groups. Children: refractive error, amblyopia, congenital cataract, retinoblastoma, and inherited retinal disease. Pregnancy: diabetic retinopathy progression. Older adults: cataract, glaucoma, macular degeneration and hearing and visual dual loss. Region specific: trachoma, onchocerciasis (river blindness), vitamin A deficiency, and HIV related retinitis.

Refractive and media

• Myopia, hyperopia, astigmatism, presbyopia
• Cataract (age related, steroid induced, diabetic, congenital, traumatic), posterior capsule opacification
• Corneal disease: keratoconus, corneal dystrophies, corneal scarring (trachoma, vitamin A deficiency, onchocerciasis, herpetic), dry eye
• Vitreous opacities

Retina and macula

• Age related macular degeneration (dry, wet), diabetic retinopathy and maculopathy, hypertensive retinopathy
• Chronic central serous retinopathy, epiretinal membrane, macular hole, cystoid macular oedema
• Inherited retinal dystrophies (retinitis pigmentosa, Stargardt disease, cone dystrophy), toxic retinopathy
• Retinal vein occlusion (chronic), myopic degeneration

Optic nerve and glaucoma

• Primary open angle glaucoma, normal tension glaucoma, chronic angle closure glaucoma, secondary glaucoma (steroid, uveitic, pseudoexfoliative)
• Compressive optic neuropathy (meningioma, pituitary adenoma, craniopharyngioma, aneurysm, thyroid eye disease)
• Toxic and nutritional optic neuropathy (ethambutol, tobacco alcohol amblyopia, vitamin B12 deficiency, methanol)
• Hereditary optic neuropathy (dominant optic atrophy, Leber), chronic papilloedema, optic atrophy after neuritis, ischaemic neuropathy

Visual pathway and cortex

• Pituitary and parasellar tumours (chiasmal compression), glioma, stroke sequelae, posterior cortical atrophy (Alzheimer variant), hydrocephalus

Other

• Functional visual loss, ocular melanoma or lymphoma, paraneoplastic retinopathy

Reasoning. Refract first, then examine the media, fundus and optic discs, test fields and pressure, and image the visual pathway when the cause is not ocular or the pattern is compressive.

First line. Visual acuity with refraction and pinhole, colour vision, pupils, tonometry, slit lamp, dilated fundus, visual fields, and optical coherence tomography.

Targeted tests.

• Automated perimetry (glaucoma and chiasmal defects), optical coherence tomography of retinal nerve fibre layer and macula, fundus photography, gonioscopy and central corneal thickness for glaucoma, and fluorescein angiography for vascular disease.
• Electroretinogram and visual evoked potentials for suspected retinal dystrophy or optic neuropathy; genetic testing for inherited retinal disease after counselling.
• MRI brain and orbits with gadolinium for optic neuropathy, field defects, and papilloedema; MRI pituitary sequences for suspected pituitary tumour.
• HbA1c and glucose, blood pressure, lipids, full blood count, vitamin B12, folate, thyroid function, syphilis serology, and, when indicated, prolactin, cortisol, insulin like growth factor 1 and gonadotrophins for pituitary disease.
• Serum vitamin A (retinol) in suspected deficiency.
• Lumbar puncture with opening pressure after imaging when idiopathic intracranial hypertension is suspected.

Limitations. Perimetry is learning dependent and variable. Structural glaucoma damage may precede field loss. Normal acuity does not exclude significant field loss.

Refractive error. Spectacle or contact lens correction after refraction, and surgical correction in selected adults; children need early refraction and amblyopia treatment.

Cataract. Surgery (phacoemulsification with intraocular lens) when vision affects function and after informed discussion, with correction of coexisting disease; stop smoking and review steroid use.

Primary open angle glaucoma. Lower intraocular pressure by at least 20 to 30 percent from baseline.

• Latanoprost 0.005 percent 1 drop in the affected eye at night (or bimatoprost or travoprost).
• Timolol 0.5 percent 1 drop twice daily (avoid in asthma, heart block, bradycardia).
• Dorzolamide 2 percent 1 drop three times daily, or brimonidine 0.2 percent 1 drop twice daily.
• Laser trabeculoplasty or surgery by ophthalmology when drops fail.

Lifelong monitoring, family screening, and adherence support.

Chronic angle closure. Laser peripheral iridotomy, with lens extraction by ophthalmology as needed.

Diabetic retinopathy. Optimise glycaemic control (HbA1c target generally 48 to 53 mmol/mol, avoiding very rapid lowering), blood pressure under 130/80 mmHg, lipids, and annual retinal screening (each trimester in pregnancy); laser photocoagulation, intravitreal anti-vascular endothelial growth factor injections or vitrectomy for referable disease.

Age related macular degeneration. Stop smoking, healthy diet, and a supplement of antioxidant vitamins and zinc for intermediate disease (vitamin C 500 mg, vitamin E 400 units, zinc 80 mg and copper 2 mg, with lutein 10 mg and zeaxanthin 2 mg daily). Wet disease needs urgent intravitreal anti-vascular endothelial growth factor injections.

Hypertensive retinopathy. Controlled blood pressure reduction and cardiovascular risk management.

Compressive lesions. Neurosurgical, endocrine and oncology care. Pituitary adenoma: surgery, cabergoline 0.25 mg orally twice weekly increased by 0.25 mg every 4 weeks to a usual 0.5 to 2 mg weekly for prolactinoma (monitor for impulse control disorders and valvular heart disease), and hormone replacement.

Toxic and nutritional optic neuropathy. Stop ethambutol or other culprit drugs after specialist advice, treat vitamin B12 deficiency (hydroxocobalamin 1 mg IM on alternate days until no further improvement, up to 3 weeks, then 1 mg every 2 months), stop alcohol and tobacco, and replace thiamine and folate.

Vitamin A deficiency. Retinol (vitamin A) 200,000 units orally on days 1, 2 and 14 for adults and children over 12 months (100,000 units for 6 to 11 months; 50,000 units for under 6 months). Avoid in pregnancy except for severe deficiency under specialist direction (maximum 10,000 units daily).

Trachoma and onchocerciasis. Trachoma: azithromycin 20 mg/kg orally as a single dose (maximum 1 g), face washing, environmental measures, and surgery for trichiasis. Onchocerciasis: ivermectin 150 micrograms/kg orally as a single dose, repeated every 6 to 12 months for 10 to 15 years (do not use with Loa loa co-infection and heavy microfilaraemia without specialist advice).

Inherited retinal disease. Genetic counselling, low vision services, and gene therapy where eligible.

Low vision and safety. Low vision rehabilitation (magnifiers, lighting, contrast, screen readers), occupational therapy, falls prevention, advice on driving (stop when under the legal visual limits), certification of visual impairment where applicable, and screening for depression.

Monitoring. Visual acuity, fields and intraocular pressure at intervals set by disease (glaucoma every 3 to 12 months), optical coherence tomography for macular disease, annual diabetic screening, and annual screening for hydroxychloroquine retinopathy after 5 years of use.

Referral and escalation. Optometry for refraction and screening. Ophthalmology for cataract, glaucoma, macular disease and diabetic retinopathy. Same week for suspected wet macular degeneration. Neurology, neurosurgery and endocrinology for compressive and chiasmal lesions. Genetics for inherited disease.

Admission criteria. Rarely needed: pituitary apoplexy, hypertensive emergency, or neurosurgical emergency.

Discharge and safety netting. Return for sudden loss, new distortion, flashes, curtain, pain, double vision, severe headache, or a fall in vision despite treatment.