Blurred vision

Blurred vision is loss of sharpness of vision, from refractive error to disease of the cornea, lens, vitreous, retina, optic nerve or visual pathway. It may be gradual or sudden, constant or transient, and monocular or binocular.

Clinical relevance. Sudden monocular loss and blurring with flashes or curtain, or with pain, needs same day assessment. Gradual blurring in diabetes may signal maculopathy. Binocular blurring suggests refractive, lens, or visual pathway causes.

Anatomy. Light passes through the tear film, cornea, aqueous, lens and vitreous to the retina; signals pass along the optic nerve, chiasm, tracts and radiations to the occipital cortex.

Classification. By onset: sudden (seconds to minutes), acute (hours to days), subacute (weeks), gradual (months to years). By laterality: monocular or binocular. By site: refractive, corneal, lens, vitreous, retinal (macular), optic nerve, and cerebral.

Key distinctions. Improvement with a pinhole indicates refractive error. Distortion (metamorphopsia) points to macular disease. Floaters and flashes point to vitreous or retinal traction. Painless sudden loss points to vascular occlusion or retinal detachment. Pain with movement points to optic neuritis.

History. Onset, speed, laterality, constant or transient, painless or painful, distortion, floaters, flashes, curtain, halos, glare, difficulty at night, double vision, headache, jaw claudication.

Also ask about previous eye disease, glasses, contact lenses, trauma, surgery, diabetes (duration, control), hypertension, cardiovascular disease, multiple sclerosis, family history (glaucoma, macular degeneration), smoking, and drug history.

Drug history. Corticosteroids (cataract, glaucoma), hydroxychloroquine and chloroquine (retinopathy), amiodarone (optic neuropathy, corneal deposits), ethambutol (optic neuropathy), isoniazid, tamoxifen, vigabatrin, topiramate (angle closure, myopic shift), sildenafil and other phosphodiesterase inhibitors, anticholinergics (blurred near vision), isotretinoin, fingolimod and other drugs causing macular oedema, and insulin or glucose fluctuations.

Examination. Visual acuity (near and distance, each eye, pinhole), colour vision, pupils (relative afferent defect), visual fields by confrontation, eye movements, red reflex, slit lamp (cornea, lens), intraocular pressure.

Also dilated fundus examination (disc, macula, vessels, periphery), Amsler grid, blood pressure and pulse rhythm, carotid bruit, and temporal arteries.

Red flags

• Sudden painless monocular visual loss (retinal artery or vein occlusion, vitreous haemorrhage, retinal detachment)
• Flashes, new floaters or a curtain (retinal tear or detachment)
• Pain with reduced vision, red eye or halos (angle closure, uveitis, keratitis, optic neuritis)
• Jaw claudication, scalp tenderness and age over 50 (giant cell arteritis)
• Transient monocular loss lasting minutes (amaurosis fugax) or neurological symptoms (stroke or transient ischaemic attack)
• Visual field defect, double vision, or headache with papilloedema
• Blurred vision with severe hypertension (hypertensive retinopathy, pre-eclampsia)
• Recent head or eye trauma
• Rapid change in diabetes control or new diabetic retinopathy
• Child with abnormal red reflex, white pupil or squint

Special groups. Children: refractive error, amblyopia, retinoblastoma, and cataract. Pregnancy: pre-eclampsia, diabetic retinopathy progression, central serous retinopathy. Older adults: cataract, macular degeneration, glaucoma, vascular occlusion and giant cell arteritis. Region specific: trachoma, onchocerciasis, vitamin A deficiency and HIV related cytomegalovirus retinitis.

Refractive and accommodative

• Myopia, hyperopia, astigmatism, presbyopia, anisometropia
• Accommodation insufficiency and drug effects, uncorrected glasses
• Transient refractive change with blood glucose swings

Ocular surface and anterior segment

• Dry eye and blepharitis, tear film instability, corneal abrasion, keratitis, corneal oedema, keratoconus
• Cataract, posterior capsule opacification
• Anterior uveitis, angle closure glaucoma, hyphaema

Vitreous and retina

• Posterior vitreous detachment, vitreous haemorrhage, asteroid hyalosis
• Retinal tear and detachment
• Diabetic retinopathy and maculopathy, hypertensive retinopathy, retinal vein occlusion, retinal artery occlusion
• Age related macular degeneration (dry and wet), central serous chorioretinopathy, macular hole, epiretinal membrane, cystoid macular oedema
• Retinitis pigmentosa, retinal dystrophies, toxic retinopathy (hydroxychloroquine)
• Infective retinitis and choroiditis (cytomegalovirus, toxoplasmosis, syphilis, tuberculosis, toxocariasis), posterior uveitis, endophthalmitis
• Retinal vasculitis, sickle cell retinopathy, Coats disease, retinoblastoma and choroidal melanoma

Optic nerve and pathways

• Optic neuritis, ischaemic optic neuropathy (arteritic and non-arteritic), toxic and nutritional optic neuropathy (ethambutol, methanol, vitamin B12 deficiency, tobacco alcohol amblyopia), compressive optic neuropathy, Leber hereditary optic neuropathy, glaucoma
• Papilloedema (idiopathic intracranial hypertension, tumour)
• Pituitary tumour and chiasmal lesions, stroke and occipital lesion, migraine aura

Functional and other

• Functional visual loss, convergence insufficiency, eye strain, uncorrected presbyopia
• Medication and toxin effects, pregnancy changes, hypoglycaemia

Reasoning. Repeat visual acuity with pinhole to identify refractive error. Examine the fundus (dilated when safe) and classify by onset and laterality. Order imaging and blood tests when optic nerve, vascular or systemic causes are likely.

First line. Visual acuity with pinhole, near vision, colour vision, pupils, confrontation fields, intraocular pressure, slit lamp and dilated fundus examination (once angle closure is unlikely), capillary glucose, and blood pressure.

Targeted tests.

• Optical coherence tomography of macula and optic nerve; fundus photography; fluorescein or OCT angiography for macular oedema, vascular occlusion and neovascularisation; B scan ultrasound when the view is poor.
• Automated visual field testing for glaucoma, chiasmal and cortical lesions.
• HbA1c, glucose, lipids, full blood count, ESR, C reactive protein (giant cell arteritis), renal function, thyroid function, syphilis serology, HIV, interferon gamma release assay, and angiotensin converting enzyme by suspicion; haemoglobin electrophoresis in sickle cell disease.
• Carotid duplex ultrasound, ECG, echocardiography and prolonged rhythm monitoring for retinal artery occlusion and transient visual loss (embolic source).
• MRI brain and orbits for optic neuritis, chiasmal and cerebral lesions; MR or CT angiography for suspected vascular disease; lumbar puncture with opening pressure for suspected idiopathic intracranial hypertension.
• Visual evoked potentials and electroretinogram for unexplained loss.

Limitations. Visual acuity does not detect early glaucoma or field loss. Normal imaging does not exclude functional loss.

Emergencies (same day ophthalmology).

• Retinal artery occlusion: immediate ophthalmology and stroke service assessment as a transient ischaemic attack equivalent; lie flat, ocular massage and anterior chamber paracentesis by ophthalmology within 24 hours.
• Retinal artery occlusion, further measures: aspirin 300 mg orally daily and investigation for embolic source; consider thrombolysis within 4.5 hours by stroke or ophthalmology teams.
• Retinal tear or detachment: urgent ophthalmology (laser, cryotherapy, vitrectomy).
• Vitreous haemorrhage: ophthalmology and exclusion of tear; upright position.
• Giant cell arteritis: prednisolone 40 to 60 mg orally each morning started before biopsy with aspirin 75 mg daily; methylprednisolone 500 mg to 1 g IV daily for 3 days if visual loss; same day specialist review.
• Acute angle closure: acetazolamide 500 mg IV or orally, timolol 0.5 percent, apraclonidine 1 percent, and pilocarpine 2 percent once pressure is falling.
• Optic neuritis: methylprednisolone 1 g IV daily for 3 to 5 days under neurology and ophthalmology care.
• Hypertensive emergency with retinopathy: controlled reduction of blood pressure by specialist care (labetalol 20 mg IV bolus then 20 to 80 mg every 10 minutes or infusion 0.5 to 2 mg/minute, reducing mean arterial pressure by no more than 25 percent in the first hour).
• Pre-eclampsia: magnesium sulphate 4 g IV over 5 to 15 minutes then 1 g/hour, with obstetric care.
• Retinal vein occlusion and wet macular degeneration: urgent ophthalmology for intravitreal anti-vascular endothelial growth factor therapy (ranibizumab, aflibercept, or bevacizumab by injection monthly then by response).

Refractive error. Spectacle or contact lens correction after refraction by an optometrist, and refractive surgery in selected adults. Children: early refraction and amblyopia treatment (patching or atropine 1 percent penalisation).

Dry eye. Lubricants (hypromellose 0.3 percent or sodium hyaluronate 0.1 to 0.2 percent, 1 drop 4 to 6 times daily, preservative free when frequent), lid hygiene, and ciclosporin 0.05 percent drops twice daily for moderate to severe disease.

Cataract. Surgical removal when visual function affects daily life, with preoperative assessment and IOL implant; stop smoking; correct refractive error in the interim.

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

Glaucoma. Lifelong topical treatment: prostaglandin analogue (latanoprost 0.005 percent, 1 drop at night), beta blocker (timolol 0.5 percent twice daily; avoid in asthma, heart block and bradycardia), or other classes by ophthalmology, with laser and surgery as needed.

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

Toxic and nutritional optic neuropathy. Stop the offending drug (ethambutol), correct deficiency (hydroxocobalamin 1 mg IM on alternate days until no further improvement, up to 3 weeks, then every 2 months; folic acid only after B12), and abstain from alcohol and tobacco.

Infective retinitis. Specialist treatment:

• toxoplasmosis (pyrimethamine, sulfadiazine, or trimethoprim with sulfamethoxazole 160 mg/800 mg orally twice daily for 4 to 6 weeks, with folinic acid)
• cytomegalovirus retinitis (valganciclovir 900 mg orally twice daily for 21 days then 900 mg daily, adjusted for creatinine clearance; ganciclovir 5 mg/kg IV every 12 hours)
• syphilis (benzylpenicillin 3 to 4 million units IV every 4 hours for 10 to 14 days)
• antiretroviral therapy

Idiopathic intracranial hypertension. Weight loss, acetazolamide 500 mg orally twice daily increased by 500 mg each week to a maximum of 4 g daily as tolerated (halve when creatinine clearance is 10 to 50 mL/min), serial visual field testing, and urgent neurosurgical or ophthalmic intervention for threatened vision.

Visual hygiene and safety. Stop driving when vision does not meet the legal limits for visual acuity and field set by local rules, falls prevention, adequate lighting, and low vision services.

Monitoring. Repeat acuity and fields at each review, optical coherence tomography for macular disease, intraocular pressure for glaucoma, annual screening in diabetes, and monitoring for drug toxicity (hydroxychloroquine annual screening after 5 years).

Referral and escalation. Same day ophthalmology for sudden loss, flashes, curtain, pain, or red flags. Neurology or stroke team for transient monocular loss and neurological signs. Optometry for refractive correction. Diabetic eye screening for all patients with diabetes.

Admission criteria. Retinal artery occlusion within the thrombolysis window, giant cell arteritis with visual loss, endophthalmitis, orbital cellulitis, hypertensive emergency, or intracranial pathology.

Discharge and safety netting. Return urgently for sudden loss, flashes, curtain, new floaters, pain, double vision, headache with visual disturbance, or worsening vision.