Distorted vision

Distorted vision (metamorphopsia) is a warping of straight lines, with waviness, bending, missing segments or size change (micropsia, macropsia). It most often arises from disease of the macula that displaces the photoreceptors.

Anatomy. The fovea in the macula provides central vision. Fluid, haemorrhage, membrane or traction beneath or on the retina displaces photoreceptors and causes distortion.

Classification. Macular (age related macular degeneration, macular oedema, central serous chorioretinopathy, epiretinal membrane, macular hole, vitreomacular traction, choroidal neovascularisation, retinal detachment), optic nerve, corneal and lens, and cerebral (migraine aura, visual cortex lesions, Alice in Wonderland syndrome, drug effect).

Key distinctions. Straight lines appearing curved on an Amsler grid indicate macular disease. Distortion that persists with one eye closed is retinal or ocular; distortion only with both eyes open points to binocular causes. Distortion with flashes or curtain indicates retinal detachment.

History. Onset (sudden or gradual), eye affected, lines appearing wavy, central blur or grey patch, change in size of objects, relation to reading, previous eye disease, diabetes, hypertension, smoking, age, family history of macular degeneration, myopia, steroid use (central serous chorioretinopathy), pregnancy, stress, migraine, head injury, and drugs.

Drug history. Corticosteroids (central serous chorioretinopathy), phosphodiesterase inhibitors, hydroxychloroquine, tamoxifen, fingolimod, taxanes, nicotinic acid, prostaglandin drops (cystoid macular oedema), anticoagulants (haemorrhage), and topiramate.

Examination. Visual acuity (near and distance, pinhole), Amsler grid testing of each eye separately, colour vision, pupils, fields, slit lamp, dilated fundus examination (drusen, subretinal fluid, haemorrhage, exudate, membrane, hole, detachment, pigment epithelial detachment), and optical coherence tomography.

Red flags

• Sudden distortion or central loss in one eye (wet macular degeneration, macular haemorrhage, retinal detachment)
• Flashes, new floaters or a curtain
• Distortion with severe headache or neurological signs
• Rapid decline over days in a patient with known dry macular degeneration
• Diabetes with poor control and macular oedema
• Contralateral eye already affected
• Pain with eye movement (optic neuritis)
• Young patient with distortion and systemic symptoms (inflammatory eye disease)

Special groups. Pregnancy: central serous chorioretinopathy and diabetic macular oedema. Older adults: age related macular degeneration, macular hole, epiretinal membrane. Region specific: ocular toxoplasmosis, tuberculosis, and HIV related retinopathy.

Macular

• Age related macular degeneration (neovascular, dry with drusen), polypoidal choroidal vasculopathy, myopic choroidal neovascularisation
• Diabetic macular oedema, retinal vein occlusion with macular oedema, hypertensive retinopathy, cystoid macular oedema (post cataract surgery, uveitis, drug)
• Central serous chorioretinopathy, epiretinal membrane, macular hole, vitreomacular traction, macular telangiectasia, solar retinopathy
• Choroidal tumour, choroiditis, toxoplasma retinochoroiditis, tuberculosis, syphilitic chorioretinitis, birdshot choroidopathy
• Angioid streaks, pseudoxanthoma elasticum, retinal dystrophies (Best disease, Stargardt disease)

Other retinal and optic nerve

• Retinal detachment, serous retinal detachment, retinal artery and vein occlusion
• Optic neuritis, papilloedema (disc oedema with peripapillary folds), optic disc pit, compressive optic neuropathy

Corneal and lens

• Keratoconus, corneal scars, irregular astigmatism, dry eye, pterygium, lens subluxation, cataract

Cerebral and functional

• Migraine aura, occipital lobe lesions, temporal lobe seizures, Alice in Wonderland syndrome, psychedelic drugs, cannabis, stroke, functional

Reasoning. Test with the Amsler grid and examine the macula. Optical coherence tomography is the key test; same day or next day referral for suspected neovascular disease.

First line. Visual acuity, Amsler grid, pupils, slit lamp and dilated fundus examination, and optical coherence tomography.

Targeted tests.

• Optical coherence tomography (fluid, drusen, membrane, hole, vitreomacular traction) and optical coherence tomography angiography, fundus fluorescein angiography and indocyanine green angiography for choroidal neovascularisation, polypoidal disease, vasculitis and leakage, and fundus autofluorescence.
• Corneal topography for keratoconus; refraction.
• HbA1c and glucose, blood pressure, lipids, and full blood count for diabetic and vascular disease; syphilis serology, interferon gamma release assay, angiotensin converting enzyme, and toxoplasma serology for uveitis.
• Electroretinogram and genetic testing for suspected retinal dystrophy.
• MRI brain and orbits for suspected optic nerve or cerebral causes.

Limitations. The Amsler grid is not sensitive for early disease. Optical coherence tomography may not show small leaks without angiography.

Neovascular age related macular degeneration (urgent: treatment within about 1 week). Intravitreal anti-vascular endothelial growth factor injections by retinal specialists: aflibercept 2 mg, ranibizumab 0.5 mg, bevacizumab 1.25 mg, or faricimab 6 mg, given monthly for the first 3 doses then by response or fixed interval (treat and extend). Stop smoking and give home Amsler grid monitoring.

Dry age related macular degeneration. Stop smoking, healthy diet, and a supplement of vitamin C 500 mg, vitamin E 400 units, zinc 80 mg, copper 2 mg, lutein 10 mg and zeaxanthin 2 mg daily for intermediate disease (benefit shown in large studies; not for smokers if beta carotene is used). Home monitoring with the Amsler grid and low vision support. Complement inhibitor intravitreal therapy (pegcetacoplan or avacincaptad pegol) for geographic atrophy by specialists in selected patients.

Diabetic macular oedema. Optimise glycaemic control (HbA1c target generally 48 to 53 mmol/mol, avoiding very rapid lowering), blood pressure under 130/80 mmHg and lipids; intravitreal anti-vascular endothelial growth factor injections, or intravitreal corticosteroid implants (dexamethasone 0.7 mg), and laser photocoagulation.

Retinal vein occlusion with macular oedema. Anti-vascular endothelial growth factor injections or corticosteroid implant, laser for neovascularisation, and systemic risk factor control.

Central serous chorioretinopathy. Observation for 3 to 4 months (most resolve), stop corticosteroids where possible, manage stress and sleep; photodynamic therapy with half dose verteporfin or subthreshold laser for persistent or recurrent disease; eplerenone 25 mg orally daily for 1 week then 50 mg daily (evidence is limited).

Epiretinal membrane and macular hole. Observation for mild symptoms; vitrectomy with membrane peeling or hole repair by retinal surgeons for significant distortion or reduced vision; ocriplasmin is rarely used.

Cystoid macular oedema after cataract surgery or uveitis. Topical prednisolone acetate 1 percent 4 times daily and ketorolac 0.5 percent or nepafenac 0.1 percent 1 drop three times daily for 4 to 12 weeks; peribulbar or intravitreal steroid for refractory cases; prostaglandin analogue cessation when relevant.

Retinal detachment. Immediate ophthalmology for surgery.

Infective and inflammatory chorioretinitis. Specialist care:

• toxoplasmosis (trimethoprim with sulfamethoxazole 160 mg/800 mg orally twice daily for 4 to 6 weeks, with prednisolone 0.5 to 1 mg/kg daily started after 2 to 3 days)
• syphilis (benzylpenicillin 3 to 4 million units IV every 4 hours for 10 to 14 days)
• tuberculosis (isoniazid 5 mg/kg, rifampicin 10 mg/kg, pyrazinamide 25 mg/kg and ethambutol 15 mg/kg daily for 2 months, then isoniazid and rifampicin for 4 months, with pyridoxine 10 to 25 mg daily)
• immunosuppression for non-infectious uveitis

Drug related maculopathy. Review and stop the culprit drug after specialist advice (hydroxychloroquine: annual screening after 5 years of use; fingolimod; taxanes).

Optic neuritis. Methylprednisolone 1 g IV daily for 3 to 5 days under neurology and ophthalmology care.

Migraine aura. Acute: sumatriptan 50 to 100 mg orally at onset (not during aura alone; contraindicated in ischaemic heart disease, stroke, uncontrolled hypertension, and with ergots or monoamine oxidase inhibitors), ibuprofen 400 to 600 mg or aspirin 900 mg. Prevention for frequent attacks: propranolol 40 mg orally twice daily increased to a usual 80 to 160 mg daily (maximum 240 mg daily).

Keratoconus. Corneal cross linking for progressive disease, specialty contact lenses, and prevention of eye rubbing.

Low vision support. Magnifiers, lighting, contrast aids, screen readers, occupational therapy, and registration for visual impairment where applicable. Advice on driving.

Monitoring. Visual acuity and optical coherence tomography at each injection visit (every 4 to 12 weeks); daily Amsler grid self testing for patients with macular disease; annual retinal screening in diabetes.

Referral and escalation. Same day or next day ophthalmology for sudden distortion or central loss. Retinal specialist for neovascular macular degeneration and diabetic macular oedema. Neurology for suspected central cause. Low vision services for established loss.

Admission criteria. Retinal detachment awaiting urgent surgery, endophthalmitis, or neurological emergency.

Discharge and safety netting. Return for any sudden change in distortion, a new blind spot, flashes, curtain, pain, or redness. Advise on home Amsler testing and smoking cessation.