Introduction to Ophthalmology • Ophthalmic symptomatology • Abnormal vision
Abnormal Vision: Blurred Vision, Peripheral Field Loss, Glare and Floaters
“Abnormal vision” is a symptom group, not a diagnosis. A patient may describe blur, dimness, missing areas, glare, halos, flashes, floaters, distortion, double vision or complete loss. The clinician’s first task is to protect sight and identify time-critical disease, then localise the problem to the optical media, retina, optic nerve, visual pathway, orbit or brain.
Urgent warning: Sudden visual loss, a new curtain or field defect, new flashes with many floaters, painful red eye with reduced vision, visual loss after trauma or chemical exposure, acute diplopia with neurological signs, or proptosis with fever requires same-day emergency assessment. Do not reassure a patient simply because the eye is not red or painful.
Learning objectives
- Define and distinguish blurred vision, reduced peripheral vision, glare/halos, floaters, flashes, distortion, diplopia and visual loss.
- Take a focused history that separates ocular, neurological, systemic, medication and functional causes.
- Recognise red flags for retinal detachment, vascular occlusion, acute glaucoma, optic neuropathy, orbital disease and stroke.
- Perform a safe first assessment: visual acuity, pupils, fields, eye movements and external examination.
- Provide first aid and referral while avoiding harmful delays, pressure or inappropriate eye drops.
- Explain hospital investigations, treatment principles, follow-up and prevention.
1. What does the patient mean by “I cannot see properly”?
| Patient description | Clinical term | Clarifying question |
|---|---|---|
| “Everything is out of focus.” | Blurred vision. | Is it near, distance, one eye or both? Does pinhole or blinking help? |
| “I cannot see to the side.” | Peripheral field loss/scotoma. | Is the missing area fixed, moving, one side of both eyes or one eye? |
| “Headlights spread and hurt.” | Glare/light scatter. | Is it worse at night, in bright light, with cataract, dry eye or contact lenses? |
| “Cobwebs or black dots move with my eye.” | Floaters/entoptic shadows. | New or longstanding? Flashes? Curtain? Trauma or myopia? |
| “Flashes of lightning.” | Photopsias. | New? Peripheral? With floaters or field loss? |
| “A curtain came down.” | Acute field loss or amaurosis. | Which eye, how long, complete or partial, and did it recover? |
| “Straight lines are bent.” | Metamorphopsia. | Central distortion? Test each eye and consider macular disease. |
| “I see two.” | Diplopia. | Does it disappear when either eye is covered? |
| “The world went dark.” | Severe visual loss/amaurosis. | Exact onset, last-known-well time and associated neurological symptoms. |
2. Focused history
- Onset and time: exact time, sudden versus gradual, transient versus persistent, first episode or recurrent.
- Laterality: right, left or both. Ask the patient to cover each eye separately during symptoms.
- Pattern: central, peripheral, general dimness, patch/scotoma, distortion, movement-related or position-related.
- Severity and function: reading, faces, walking, driving, colour, light perception and occupational tasks.
- Pain and inflammation: pain, pain on eye movement, photophobia, redness, discharge, headache, nausea/vomiting.
- Retinal symptoms: flashes, shower of floaters, curtain, field defect, night blindness.
- Neurological symptoms: weakness, numbness, speech difficulty, imbalance, altered consciousness or severe headache.
- Trauma/exposure: blunt or penetrating injury, grinding/welding, chemical splash, foreign body, recent surgery or injection.
- Risk factors: myopia, diabetes, hypertension, sickle-cell disease, vascular disease, migraine, glaucoma, autoimmune disease, infection, pregnancy, smoking and immunosuppression.
- Medicines: steroids, anticholinergics, glaucoma drops, hydroxychloroquine, ethambutol, topiramate, anticoagulants and drugs causing sedation or visual disturbance.
- Contact lenses: type, overnight wear, hygiene, water exposure, replacement schedule and current use.
- Family and eye history: retinal detachment, glaucoma, macular disease, previous surgery, amblyopia or one-eyed status.
3. Immediate assessment at first contact
| Assessment | How to do it safely | Why it matters |
|---|---|---|
| Airway, breathing, circulation and disability | Stabilise life threats first; check glucose when altered or neurological. | Stroke, hypoglycaemia, seizure and trauma can present with visual symptoms. |
| Visual acuity | Test each eye separately with usual correction; record chart and distance, then pinhole if appropriate. | Objective baseline and major triage discriminator. |
| Pupils | Size, shape, equality, direct/consensual responses and swinging-light test. | RAPD suggests optic-nerve or severe retinal dysfunction. |
| Visual fields | Confrontation by eye, noting central/peripheral defects. | Identifies retinal, optic-pathway and neurological patterns. |
| Eye movements | Versions/ductions, pain, nystagmus, diplopia and restriction. | Localises cranial-nerve, muscle, orbit or brainstem disease. |
| External eye | Lids, conjunctiva, cornea clarity, pupil, proptosis, trauma and discharge. | Red eye, open globe, orbital disease and infection can be visible. |
| IOP/fluorescein | Only when open-globe injury is not suspected and trained equipment/protocol is available. | Helps identify glaucoma or epithelial injury without causing harm. |
Never press on a suspected open globe. Do not force the eyelids open, remove an embedded object, patch tightly, perform tonometry or instil drops before specialist advice. Use a rigid shield, avoid food if anaesthesia may be needed and arrange urgent ophthalmology.
4. Blurred vision
Blur may originate anywhere from tear film to visual cortex. The pattern and associated findings are more informative than the word “blur.”
| Category | Examples | Clues |
|---|---|---|
| Optical/refractive | Myopia, hyperopia, astigmatism, presbyopia. | Gradual, often painless; improves with pinhole or correct lenses; no RAPD. |
| Ocular surface/cornea | Dry eye, abrasion, keratitis, ulcer, oedema, scar. | Fluctuation, pain, photophobia, foreign-body sensation, staining or opacity. |
| Lens | Cataract, lens displacement, postoperative change. | Glare, gradual painless decline, reduced red reflex; trauma may be acute. |
| Retina/macula | Diabetic oedema, macular degeneration, detachment, haemorrhage. | Distortion, central scotoma, floaters, flashes or field loss. |
| Optic nerve | Optic neuritis, ischaemic optic neuropathy, compression. | Colour desaturation, RAPD, central field loss, pain on movement or sudden loss. |
| Neurological | Stroke, occipital lesion, migraine aura, seizure. | Field pattern, neurological signs, transient/recurrent features. |
| Systemic/metabolic | Hypoglycaemia, severe hypertension, anaemia, toxic medication effects. | Systemic symptoms or bilateral fluctuation; still assess the eyes. |
| Functional/non-organic | Visual symptoms without an anatomical explanation. | Diagnosis of exclusion after respectful examination; never assume malingering. |
5. Reduced peripheral vision and visual-field defects
Peripheral vision is the ability to detect objects outside the point of fixation. Field loss may be retinal, optic-nerve, chiasmal, retrochiasmal or cortical. Patients may describe bumping into objects, missing people approaching from one side, difficulty driving or a “tunnel.”
| Pattern | Possible localisation | Examples/next step |
|---|---|---|
| Monocular peripheral defect | Retina or optic nerve before the chiasm. | Retinal detachment, glaucoma, optic neuropathy; test each eye separately. |
| Bitemporal hemianopia | Optic chiasm, especially crossing nasal fibres. | Sellar/parasellar mass; urgent neurological and ophthalmic evaluation. |
| Homonymous hemianopia | Optic tract, radiations or occipital cortex behind the chiasm. | Stroke, tumour or trauma; activate neurological pathway if acute. |
| Altitudinal defect | Retinal vascular or optic-nerve disease. | Ischaemic optic neuropathy or vascular occlusion; urgent assessment. |
| Arcuate scotoma | Retinal nerve-fibre layer damage. | Glaucoma is a major consideration; formal perimetry and optic-disc assessment. |
| Central scotoma | Macula or optic nerve. | Macular disease, optic neuritis or toxic optic neuropathy. |
| Constriction/tunnel vision | Advanced glaucoma/retinal disease, neurological or functional causes. | Document objectively and avoid assuming a single cause. |
Assessment
- Ask the patient to fixate centrally and test each eye by confrontation; compare quadrants and test a red target if useful.
- Check for neglect, inattention and neurological deficits; a patient may deny a field loss.
- Formal automated or kinetic perimetry maps the defect and monitors progression.
- Optic-disc examination, retinal assessment, OCT and neuroimaging are selected according to the pattern.
6. Glare, halos and light sensitivity
Glare is disability or discomfort from bright light or scattered light. Halos are rings around point lights. Photophobia is painful light sensitivity. They overlap but are not interchangeable.
| Cause category | Examples | Clues |
|---|---|---|
| Ocular-surface scatter | Dry eye, tear-film instability, corneal abrasion or scar. | Fluctuation, burning, foreign-body sensation, pain or staining. |
| Lens scatter | Cataract, posterior capsule opacity. | Gradual blur, night-driving difficulty and glare; usually little pain. |
| Corneal oedema/raised IOP | Acute angle-closure glaucoma. | Halos with severe pain, red eye, headache, nausea/vomiting and reduced vision. |
| Intraocular inflammation | Anterior uveitis, keratitis, endophthalmitis. | Photophobia, ciliary flush, cells/flare, hypopyon or severe reduction. |
| Neurological/migraine | Migraine aura, meningitis, concussion. | Visual phenomena with headache or neurological symptoms; eye may appear normal. |
Management is cause-directed: improve the ocular surface when appropriate, correct refractive/lens problems, urgently treat inflammation or pressure disorders, and address neurological causes. Do not mask a painful red eye with topical steroid or anaesthetic outside a supervised protocol.
7. Floaters and flashes
Floaters are perceived shadows from vitreous opacities; photopsias are flashes generated by mechanical or electrical stimulation of the retina or visual pathways. Longstanding stable floaters may be benign, but new symptoms can signal a retinal tear.
| Presentation | Likely possibilities | Urgency |
|---|---|---|
| Longstanding few floaters, unchanged | Vitreous syneresis or stable opacities. | Routine eye review unless symptoms change. |
| Sudden shower of floaters | Posterior vitreous detachment, vitreous haemorrhage or retinal tear. | Same-day dilated retinal assessment. |
| Flashes in peripheral vision | Vitreoretinal traction or retinal tear. | Urgent assessment, especially with floaters. |
| Floaters plus curtain/field loss | Retinal detachment until excluded. | Emergency retinal pathway. |
| Floaters with pain/redness | Uveitis, endophthalmitis or severe inflammation. | Urgent ophthalmic assessment. |
| Dark spots after trauma | Vitreous haemorrhage, retinal injury or intraocular foreign body. | Emergency evaluation; protect the eye. |
8. Dangerous causes of abnormal vision
Retinal detachment
Retinal separation may cause flashes, new floaters and a curtain or progressive field defect. Risk is higher with myopia, previous eye surgery, trauma and a history in the other eye. Do not allow driving; arrange urgent dilated retinal examination and surgical/laser treatment as indicated.
Retinal vascular occlusion
Acute painless monocular loss can result from retinal arterial or venous obstruction. Record last-known-well time, assess vascular risk and neurological status, and activate urgent ophthalmic/stroke evaluation. Do not wait for routine review.
Acute angle-closure glaucoma
Severe eye pain, blurred vision, halos, red eye, headache, nausea/vomiting and a mid-dilated poorly reactive pupil are warning signs. Avoid mydriatic drops and urgent delay; seek immediate ophthalmology management and monitor systemic status.
Optic neuropathy
Reduced acuity, colour desaturation, central scotoma and RAPD suggest optic-nerve dysfunction. Pain on movement may occur in optic neuritis; sudden painless loss may be ischaemic. Urgent assessment is required.
Stroke-related visual field loss
Sudden homonymous loss, neglect, speech difficulty, weakness, ataxia or altered consciousness needs an acute stroke pathway. Test each eye but do not delay brain imaging and reperfusion assessment where indicated.
9. Immediate first aid and initial management
- Stabilise first: manage airway, breathing, circulation, glucose and major trauma before the eye symptom when life-threatening problems coexist.
- Chemical exposure: begin immediate copious irrigation with clean water or saline; remove contact lenses if easily removable; continue according to local protocol and urgent ophthalmic advice. Do not wait for pH strips or a detailed history.
- Suspected open globe: do not press, irrigate forcefully, remove embedded objects or instil drops; place a rigid shield, provide analgesia/antiemetic according to protocol, keep the patient nil by mouth if surgery may be required and refer urgently.
- Blunt trauma: protect from further injury, assess vision/pupils and look for hyphema, orbital fracture and retinal symptoms; avoid aspirin/NSAIDs when bleeding risk is significant unless directed by a clinician.
- Contact-lens symptoms: remove lenses, do not reinsert, retain the lens/container for assessment if infection is suspected and arrange urgent review for pain, photophobia or reduced VA.
- New floaters/flashes: do not reassure or prescribe routine lubricants until retinal tear/detachment is excluded; arrange same-day examination.
- Acute neurological symptoms: document last-known-well time and activate stroke/neurological emergency processes.
10. Hospital evaluation and treatment principles
| Investigation/step | When useful | Safety and interpretation |
|---|---|---|
| Repeat VA/pupils/fields | Any significant change, referral or deterioration. | Trend matters; document each eye and time. |
| Slit-lamp/fluorescein | Red eye, pain, foreign-body sensation, trauma and photophobia. | Look for abrasion, ulcer, infiltrate, cells/flare and Seidel leak; do not press an open globe. |
| Tonometry | Suspected glaucoma or selected ocular conditions. | Avoid if open-globe injury is possible; interpret with cornea and optic-nerve findings. |
| Dilated fundus examination | Floaters/flashes, visual loss, diabetes, vascular disease and field defects. | Essential for retinal tear/detachment/haemorrhage and optic-disc assessment. |
| OCT/ocular ultrasound | Macular disease, optic nerve, vitreous opacity or obscured fundus. | Selected by ophthalmology; ultrasound is not a reason to delay emergency referral. |
| Neuroimaging/vascular studies | Acute field loss, optic neuropathy, trauma or neurological signs. | Follow stroke/trauma protocols and check contraindications. |
| Laboratory tests | Inflammatory, infectious, metabolic or vascular differential. | Targeted testing is better than indiscriminate panels. |
Management principles
- Optical/refractive: refraction and corrective lenses after urgent disease is excluded.
- Surface/corneal disease: lubrication, antimicrobial therapy or other treatment only after examination and according to local protocol; contact-lens keratitis needs urgent specialist-directed antimicrobial care.
- Retinal detachment/tear: laser, cryotherapy, pneumatic retinopexy, scleral buckle or vitrectomy may be used by specialists depending on anatomy.
- Vascular events: urgent ophthalmic and vascular/stroke assessment, risk-factor management and cause-directed treatment.
- Glaucoma/inflammation: emergency pressure-lowering or anti-inflammatory treatment should be directed by trained clinicians; avoid unsupervised steroid or mydriatic use.
- Neurological causes: manage the underlying stroke, raised intracranial pressure, seizure, migraine or toxic/metabolic cause with the appropriate team.
11. Prevention and patient education
- Use protective eyewear for grinding, drilling, chemicals, welding and high-velocity work; ordinary spectacles may not protect from impact.
- Follow contact-lens hygiene, avoid sleeping/swimming in lenses unless specifically approved and replace cases as advised.
- Control diabetes, hypertension and vascular risk; attend retinal screening when eligible.
- Do not rub a painful eye or use another person’s drops. Avoid topical anaesthetic use outside supervised examination because it delays healing and masks deterioration.
- Teach patients with one functioning eye to use protection and seek rapid care for any new symptoms.
- Return urgently for worsening pain, decreased vision, new flashes/floaters, curtain, vomiting, fever, proptosis or neurological symptoms.
12. Applied cases
Case 1: Sudden floaters and field loss
A 55-year-old highly myopic patient sees a “shower of black dots,” flashes and a grey curtain. Record acuity and pupils, avoid driving, keep the patient safe and arrange same-day dilated retinal assessment. The priority is retinal tear/detachment, not reassurance or a new spectacle prescription.
Case 2: Night glare
A 70-year-old has gradual blur and severe headlight glare but no pain or red eye. Assess acuity, red reflex, pupils, ocular surface and diabetes/medication history. Cataract, tear-film disease and refractive error are common possibilities, but sudden change or pain changes urgency.
Case 3: Field loss with weakness
A patient suddenly misses objects on the left and has left arm weakness. Test both eyes quickly to establish a homonymous field pattern, check glucose and activate the stroke pathway. Do not delay neuroimaging for a detailed ophthalmic examination.
Case 4: Chemical splash
A cleaner splashes alkaline product into one eye. Start irrigation immediately, remove contaminated clothing/contact lens if easily possible, continue flushing according to protocol and arrange emergency ophthalmic assessment. Do not neutralise with another chemical or wait for a written diagnosis.
13. Self-test
- What is the difference between blurred vision and visual-field loss?
- List four red flags in a patient with floaters.
- Why is sudden painless visual loss still an emergency?
- How do you distinguish monocular from binocular diplopia?
- When should tonometry be avoided?
- What are the immediate priorities after a chemical eye injury?
- Name three causes of glare and halos.
- What findings suggest optic-nerve dysfunction?
- What should a patient with suspected retinal detachment be told about driving?
- Why should unsupervised topical steroids be avoided in an undiagnosed red eye?
Answers
- Blur is reduced clarity of the image; field loss is missing vision in a region despite possible clarity in the remaining field.
- Sudden onset, shower of floaters, flashes, curtain/field loss, trauma, high myopia, pain/redness or reduced acuity.
- Retinal artery occlusion, retinal detachment, optic-nerve ischaemia and stroke can be painless but permanently damaging.
- Monocular persists when one eye is covered; binocular disappears when either eye is covered.
- When open-globe/penetrating injury is possible.
- Immediate copious irrigation, remove lens if easy, protect the eye, assess after initial flushing and obtain urgent ophthalmic care.
- Cataract/lens scatter, dry-eye/corneal irregularity and acute corneal oedema from angle closure.
- Reduced acuity/colour, RAPD, central scotoma, pain on movement or a characteristic field defect.
- They should not drive; arrange urgent supervised transport for same-day retinal assessment.
- Steroids can worsen infection such as herpes or fungal keratitis, delay healing and mask progression.
Key takeaways
- Clarify exactly what “abnormal vision” means and document each eye separately.
- Measure acuity, pupils, fields and movements early; these are high-yield localisation tools.
- New flashes/floaters with a curtain, sudden loss, painful red eye and trauma are emergencies.
- Irrigate chemical injury immediately and never press a suspected open globe.
- Management is cause-directed; do not use unverified drops to mask an undiagnosed sight-threatening condition.
