Ophthalmology: Basics Cataract

• Basics: How the Eye Works | Eye History | Examining the Eye | Visual Acuity | Refractive Errors | Eye Drops and How They Work
• Common conditions: Cataract | What is Glaucoma? | Primary Open-Angle Glaucoma | Ocular Hypertension | Chronic Angle Closure | Dry Eye | Eyelid Problems | Floaters and Flashes
• Living with sight loss: Vision and Driving | Sight Impairment and Support | Charles Bonnet Syndrome
• Revision: Drug Reference Table | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

👁️ Eye basics — most eye problems you will see as a doctor are common and manageable: cataract, glaucoma, dry eye and eyelid problems. The skills that matter are measuring visual acuity properly, using an ophthalmoscope and fluorescein, knowing what common eye drops do (and their side effects), and recognising when a patient needs to be seen by an eye specialist today.
Your four questions for every patient: Is vision reduced — and how much (measure it)? Is the eye red or painful? Is it one eye or both, sudden or gradual? Does this need same-day eye casualty review?

How the Eye Works

• Front of the eye (anterior segment):
  • Cornea — the clear window; does most of the focusing. Damage causes pain, watering and light sensitivity.
  • Conjunctiva — the thin membrane over the white of the eye and inside the lids.
  • Sclera — the tough white outer coat.
  • Anterior chamber — filled with aqueous humour, made by the ciliary body and drained through the trabecular meshwork in the "angle" between iris and cornea.
  • Iris and pupil — control how much light gets in.
  • Lens — fine-tunes focus (accommodation); clouding is cataract.
• Back of the eye (posterior segment):
  • Vitreous — clear gel filling the eye.
  • Retina — the light-sensing layer; the macula (with the fovea at its centre) gives sharp central and colour vision.
  • Optic disc — where the optic nerve leaves the eye; the "cup" is the central pale dip.
  • Choroid — the blood supply under the retina.
• Uvea = iris + ciliary body + choroid (inflammation is uveitis).
• Blood supply — the central retinal artery (from the ophthalmic artery, the first branch of the internal carotid). So eye problems can be a warning of carotid disease.

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Eye History

• Vision:
  • One eye or both? (Cover each eye in turn.)
  • Sudden or gradual? Painful or painless?
  • Central or peripheral loss? Blurred, distorted (straight lines look wavy — macular disease), or a "curtain" (retinal detachment)?
  • Transient (amaurosis fugax) or persistent?
• Other symptoms:
  • Pain — gritty (surface), deep ache (scleritis, uveitis, angle closure), pain on eye movement (optic neuritis).
  • Photophobia (light sensitivity) — corneal disease, uveitis.
  • Discharge — sticky (bacterial), watery (viral), stringy (allergic).
  • Flashes and floaters.
  • Double vision — does it go when one eye is covered?
  • Haloes around lights (angle closure, corneal oedema).
  • Headache, jaw claudication, scalp tenderness (GCA).
• Background:
  • Contact lens wear — a big risk factor for corneal infection.
  • Trauma (including hammering metal — high-speed foreign body).
  • Previous eye surgery; glasses; lazy eye in childhood.
  • Diabetes, hypertension, autoimmune disease.
  • Drugs — steroids, hydroxychloroquine, anticholinergics, amiodarone, ethambutol.
  • Family history — glaucoma.
  • Driving and occupation.

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Examining the Eye

• Visual acuity — always first, each eye separately, with glasses (see below).
• Inspection: Lids, redness (where is it?), discharge, pupil size and shape, corneal clarity, proptosis.
• Pupils:
  • Direct and consensual light reflex.
  • Swinging light test for a relative afferent pupillary defect (RAPD) — the affected pupil dilates when the light swings to it. Suggests optic nerve or severe retinal disease.
  • Accommodation reflex.
• Visual fields — confrontation (red pin for central field).
• Eye movements — H pattern; ask about double vision; look for nystagmus.
• Fluorescein — orange dye glows green under blue light where the corneal surface is damaged (abrasion, ulcer, dendritic ulcer).
• Ophthalmoscopy (dilate with tropicamide 1% if needed — usually safe; warn not to drive for a few hours):
  • Red reflex — absent or dull with cataract, vitreous haemorrhage, retinoblastoma (children).
  • Optic disc — colour (pale = atrophy), margins (blurred = swelling), cup size (large = glaucoma).
  • Vessels — AV nipping, emboli, haemorrhages.
  • Macula — drusen, exudates, haemorrhage.
• Specialist tests:
  • Slit lamp — magnified 3D view of the eye.
  • Tonometry — intraocular pressure (normal about 10–21 mmHg).
  • OCT (optical coherence tomography) — cross-section scans of the retina and optic nerve.
  • Formal visual fields; fluorescein angiography.

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Visual Acuity

• Snellen chart at 6 metres:
  • Recorded as a fraction — 6/6 is normal ("20/20" in the US). 6/60 means the patient sees at 6 m what a normal eye sees at 60 m.
  • Test each eye with the other covered, using their glasses.
• Pinhole — if vision improves with a pinhole, the problem is a refractive error (needs glasses), not disease.
• Very poor vision: Count fingers (CF) → hand movements (HM) → perception of light (PL) → no perception of light (NPL).
• LogMAR charts — more precise; used in clinics and research (0.0 = 6/6; 1.0 = 6/60).
• Near vision — reading chart (N-point).
• Children — picture charts or Kay pictures; preschool screening at age 4–5.

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Refractive Errors

• Myopia (short sight) — distant objects blurred; eye too long. Corrected with concave (minus) lenses. High myopia raises the risk of retinal detachment, glaucoma and myopic macular degeneration. Rising in children (more screen time, less time outdoors).
• Hypermetropia (long sight) — near objects blurred; eye too short. Convex (plus) lenses. Raised risk of angle-closure glaucoma (crowded front of the eye) and squint in children.
• Astigmatism — irregular corneal curve; blurred at all distances.
• Presbyopia — the lens stiffens with age; difficulty with near vision from about 45. Reading glasses.
• Corrections: Glasses, contact lenses, laser surgery (LASIK, PRK), lens implants.
• Contact lenses — advise no sleeping, swimming or showering in them (acanthamoeba and bacterial keratitis).

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Eye Drops and How They Work

• Dilating drops (mydriatics):
  • Tropicamide (short-acting, for examination); cyclopentolate (longer, also used for uveitis pain); atropine (long-acting); phenylephrine.
  • Risk of triggering acute angle closure in predisposed eyes (rare).
  • Blurred vision for hours — no driving.
• Local anaesthetic — proxymetacaine, oxybuprocaine, tetracaine: for examination only. Never give to take home (delays healing, hides damage).
• Steroid drops — dexamethasone, prednisolone acetate:
  • For uveitis, scleritis (with systemic treatment), after surgery.
  • Risks — raised pressure (steroid glaucoma), cataract, and worsening of herpes simplex keratitis.
  • Only start on specialist advice.
• Antibiotic drops — chloramphenicol (drops or ointment), fusidic acid, ofloxacin (for contact lens wearers), levofloxacin.
• Antivirals — ganciclovir gel or aciclovir ointment (herpes simplex keratitis).
• Antiallergy — sodium cromoglicate, olopatadine, antihistamines.
• Lubricants (artificial tears) — hypromellose, carbomer, sodium hyaluronate.
• Glaucoma drops — see below.
• Systemic absorption — drops drain to the nose and are absorbed, so timolol can cause bradycardia and bronchospasm (asthma). Teach patients to press on the inner corner of the eye for 1–2 minutes after the drop.

⚠️ Safety Pearl: Don't start steroid drops for a red eye without a slit lamp examination — they can turn a herpes simplex dendritic ulcer into a sight-threatening infection.

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Cataract

• What it is: Clouding of the lens. The commonest cause of treatable visual impairment, and cataract surgery is the commonest operation in the NHS.
• Causes and risk factors:
  • Age (most).
  • Diabetes.
  • Steroids (oral, inhaled at high doses, eye drops).
  • Smoking; UV light; alcohol.
  • Trauma; uveitis; previous eye surgery.
  • Radiation.
  • Congenital — rubella, galactosaemia, Down syndrome, genetic.
  • Myotonic dystrophy, hypocalcaemia, Wilson's disease (sunflower cataract).
• Symptoms:
  • Gradual, painless blurred vision.
  • Glare — dazzled by headlights at night.
  • Faded colours; frequent glasses changes (often more short-sighted — "second sight" for reading).
  • Monocular double vision.
• Signs: Reduced acuity; dull or absent red reflex; lens opacity on slit lamp.
• Treatment (NICE NG77):
  • Refer for surgery when the cataract affects quality of life (not a fixed acuity threshold).
  • Phacoemulsification — ultrasound breaks up the lens, which is removed through a small cut; an artificial intraocular lens is implanted. Day case, local anaesthetic, about 20 minutes.
  • Excellent results — most see better; second eye surgery offered on the same criteria.
• Complications:
  • Posterior capsule opacification — the commonest; vision clouds again months to years later. Easily treated with YAG laser.
  • Endophthalmitis (about 1 in 1,000) — painful red eye with falling vision days after surgery: same-day emergency.
  • Raised pressure; macular oedema (cystoid); retinal detachment; dropped lens fragments.
  • Floppy iris syndrome — tell the surgeon about tamsulosin (past or present).

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What is Glaucoma?

• Glaucoma is a group of diseases that damage the optic nerve, causing visual field loss. Raised eye pressure is the main treatable risk factor, but damage can occur at normal pressure.
• Types:
  • Open-angle (most common) — slow, painless, no symptoms until late.
  • Angle-closure — the iris blocks drainage. Acute angle closure is an emergency (see the Red Eye and Eye Emergencies chapter); chronic angle closure is silent.
  • Secondary — steroids, uveitis, trauma, diabetes (neovascular glaucoma), pigment dispersion.
  • Congenital — large, cloudy eyes in babies (buphthalmos).
• Glaucomatous optic disc:
  • Enlarged cup (cup-to-disc ratio over about 0.6, or asymmetry between eyes over 0.2).
  • Thinning of the rim; disc haemorrhages; "bayoneting" vessels.
• Field loss — starts in the mid-periphery (arcuate defects), spares central vision until late ("tunnel vision").

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Primary Open-Angle Glaucoma

• Who:
  • About 2% of people over 40, rising with age.
  • Family history (first-degree relatives — free NHS eye tests from age 40).
  • Black African or Caribbean ancestry — earlier and more severe.
  • Myopia; diabetes; high BP.
• Symptoms: None until advanced — that's why it's usually found by optometrists at routine eye tests.
• Diagnosis (NICE NG81): eye pressure, optic disc assessment (OCT), visual fields, gonioscopy (angle is open), corneal thickness.
• Treatment — aim to lower pressure to slow field loss:
  • Selective laser trabeculoplasty (SLT) — NICE now recommends offering this first line (LiGHT trial: as effective as drops, avoids daily drops).
  • Eye drops:
    • Prostaglandin analogues (latanoprost, bimatoprost, travoprost) — first-line drops, once at night. Increase outflow. Side effects: darker iris colour, longer eyelashes, red eyes, darkened eyelid skin.
    • Beta-blockers (timolol) — reduce aqueous production. Avoid in asthma, heart block, bradycardia.
    • Carbonic anhydrase inhibitors (dorzolamide, brinzolamide) — reduce production; stinging, bitter taste.
    • Alpha-2 agonists (brimonidine) — allergy common; avoid in young children (drowsiness).
    • Combination drops; preservative-free drops for sensitive eyes.
  • Surgery — trabeculectomy (a new drainage channel), drainage tubes, minimally invasive glaucoma surgery (MIGS).
• Follow-up — lifelong monitoring of pressure, discs and fields.
• Normal-tension glaucoma — damage with normal pressure; linked to low BP at night, migraine, vasospasm. Lowering pressure further still helps.

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Ocular Hypertension

• What it is: Eye pressure over 21 mmHg with normal optic discs and fields.
• Risk: A minority go on to develop glaucoma — higher with very high pressure, thin corneas, older age and family history.
• Management (NICE NG81):
  • Offer treatment if pressure is 24 mmHg or more and there is a risk of sight loss in the person's lifetime.
  • SLT first, or a prostaglandin analogue.
  • Monitor regularly.
• Steroid responders — about a third of people get a pressure rise on steroid drops; a few on long-term systemic or inhaled steroids.

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Chronic Angle Closure

• Who: Hypermetropic (long-sighted) eyes, older age, women, East Asian ancestry, family history. The lens thickens with age and pushes the iris forward, narrowing the drainage angle.
• Features: Often silent; sometimes brief episodes of blurring, haloes and headache in the evening or in dim light (pupil dilates) that settle — warning signs of acute closure.
• Drugs that can trigger closure in narrow angles:
  • Anticholinergics — antihistamines, tricyclics, oxybutynin, ipratropium nebulisers.
  • Sympathomimetics — salbutamol, adrenaline.
  • Topiramate (and sulfonamides — cause ciliary body swelling, both eyes).
  • Dilating drops.
• Treatment:
  • Laser peripheral iridotomy — a small hole in the iris lets aqueous bypass the block (both eyes).
  • Cataract or clear lens extraction — opens the angle (increasingly first line).
  • Pressure-lowering drops.

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Dry Eye

• Very common, especially in older women and screen users.
• Causes:
  • Meibomian gland dysfunction (oily layer of the tear film) — the commonest; with blepharitis.
  • Reduced tear production — age, Sjögren's syndrome, rheumatoid arthritis.
  • Drugs — antihistamines, tricyclics, beta-blockers, isotretinoin, diuretics.
  • Screens (less blinking), air conditioning, contact lenses.
  • Poor lid closure — Bell's palsy, thyroid eye disease.
  • After laser eye surgery.
• Symptoms: Gritty, burning, tired eyes, worse later in the day; paradoxically watery eyes; fluctuating vision.
• Treatment:
  • Lubricant drops (preservative-free if used more than 4–6 times a day); gel or ointment at night.
  • Lid hygiene — warm compresses and lid cleaning.
  • Screen breaks; humidify rooms.
  • Review drugs.
  • Specialist — ciclosporin drops, punctal plugs.
• Exposure keratopathy (e.g. facial palsy, ICU patients who can't close the eyes) — lubricants, taping, and urgent review if the cornea breaks down.

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Eyelid Problems

• Blepharitis — chronic inflammation of the lid margins: crusty, red lids, gritty eyes. Linked to rosacea and seborrhoeic dermatitis. Lid hygiene (warm compresses, cleaning); topical or oral antibiotics (doxycycline) in severe cases. Long-term, not curable.
• Stye (hordeolum) — painful infected lash follicle (external) or meibomian gland (internal). Warm compresses; usually settles. Antibiotics only if spreading cellulitis.
• Chalazion (meibomian cyst) — painless firm lump in the lid. Warm compresses and massage; incision and curettage if persistent. A recurring chalazion in an older adult may be a cancer (sebaceous carcinoma) — biopsy.
• Entropion — lid turns in, lashes rub the cornea (painful, red). Tape the lid temporarily; surgery.
• Ectropion — lid turns out (age, facial palsy): watering, dryness. Lubricants; surgery.
• Trichiasis — misdirected lashes; epilation.
• Ptosis (droopy lid):
  • Age-related (aponeurotic) — most common.
  • Third nerve palsy — with a "down and out" eye ± dilated pupil.
  • Horner syndrome — mild ptosis, small pupil.
  • Myasthenia gravis — fatigable, variable.
  • Myotonic dystrophy; congenital.
• Xanthelasma — yellow plaques on the lids; check lipids.
• Lid lumps that may be cancer — basal cell carcinoma (the commonest; pearly edge, ulcer, loss of lashes, usually lower lid), squamous cell carcinoma, sebaceous carcinoma, melanoma. Refer.
• Watery eye (epiphora) — blocked tear duct (nasolacrimal duct), ectropion, or reflex watering from dry eye. Babies — congenital duct blockage usually clears by 12 months.
• Dacryocystitis — infected tear sac: painful swelling at the inner corner of the eye; oral or IV antibiotics.

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Floaters and Flashes

• Floaters — dots, threads or cobwebs that drift with eye movement; very common with age and short sight.
• Posterior vitreous detachment (PVD):
  • The vitreous gel shrinks and pulls away from the retina — common over 50 (earlier in myopia).
  • Sudden new floaters ± flashes (light streaks, often at the edge of vision).
  • Usually harmless, but in about 1 in 10 it causes a retinal tear, which can lead to detachment.
• Refer the same day (or within 24 hours, per local pathway) for dilated examination if there are new flashes or floaters, especially with:
  • A shadow or curtain in the vision.
  • Reduced acuity.
  • A shower of floaters (may be blood).
  • High myopia, previous detachment, or recent eye surgery or trauma.
• See the Retina and Visual Loss chapter for retinal detachment.
• Migraine aura — zigzag, shimmering lights that build up over 5–20 minutes and then go, in both eyes' field, often followed by headache.

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Vision and Driving

DVLA standards (Group 1 — cars and motorbikes):

• Read a number plate at 20 metres (with glasses if needed).
• Visual acuity of at least 6/12 (decimal 0.5) with both eyes open (or in the only eye).
• Visual field — at least 120° horizontally, with at least 50° on each side, and no significant defect in the central 20°.
• Must tell the DVLA about conditions affecting both eyes or the remaining eye (glaucoma, AMD, diabetic retinopathy treated with laser, field loss after stroke) — they may assess fields.
• Double vision — must not drive until controlled (patch or prism, then DVLA confirms).
• Loss of vision in one eye — can drive if the other eye meets the standards and the person has adapted (clinical advice).
• Homonymous hemianopia (e.g. after stroke) — usually can't meet the field standard.

Group 2 (lorries and buses) — stricter: acuity of at least 6/7.5 in the better eye and 6/60 in the worse eye, and full fields.

💡 Clinical Pearl: It is the patient's legal duty to inform the DVLA — but your duty to advise them, document it, and (if they continue to drive unsafely) inform the DVLA yourself, following GMC guidance.

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Sight Impairment and Support

• Commonest causes of sight loss in the UK:
  • Age-related macular degeneration (the leading cause of registrable sight loss).
  • Glaucoma.
  • Diabetic retinopathy (leading cause in working-age adults).
  • Cataract and uncorrected refractive error (both treatable).
  • Inherited retinal disease (leading cause in working-age adults alongside diabetes).
• Certificate of Vision Impairment (CVI) — completed by an ophthalmologist; registers the person as sight impaired (partially sighted) or severely sight impaired (blind). Gives access to social care support, benefits and concessions.
• Support:
  • Low vision clinic — magnifiers, lighting, large print.
  • Eye clinic liaison officers (ECLOs).
  • Rehabilitation (mobility training, cane, guide dogs).
  • Charities (RNIB, Macular Society).
  • Technology — screen readers, voice assistants.
• Falls and frailty — poor vision is a major falls risk; check vision and glasses in falls assessments. Avoid varifocals for walking in people prone to falls.
• Delirium — make sure glasses are on and clean in hospital.

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Charles Bonnet Syndrome

• What it is: Vivid visual hallucinations in people with significant sight loss (e.g. AMD) — the brain "fills in" missing input.
• Features:
  • Complex images — faces, people in costume, animals, patterns, buildings.
  • The person knows they are not real (insight is kept).
  • No other psychiatric symptoms; normal cognition.
  • Often silent — patients fear being thought "mad", so ask directly.
• Management:
  • Reassurance — explaining it is common and not a mental illness helps most.
  • Tips — blink, move the eyes, change lighting, look at the image directly.
  • Optimise vision (cataract surgery, treat AMD).
  • Rarely, medication for distressing cases (specialist).
• Differential — delirium, Lewy body dementia, Parkinson's medication, migraine, seizures.

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Drug Reference Table

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Spot the Diagnosis

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Exam-style Scenarios

1. A 76-year-old has 2 years of gradually blurred vision in both eyes, trouble driving at night, and has stopped reading. Acuity 6/24 right, 6/18 left. Red reflexes are dull.
Answer: Bilateral cataracts affecting quality of life.

• Refer for cataract surgery (phacoemulsification with lens implant).
• Ask about tamsulosin (floppy iris) and anticoagulants.
• Advise on driving: acuity below the DVLA standard — must not drive until corrected.

2. A 58-year-old man of Caribbean descent is referred by his optometrist with pressures of 28 mmHg and enlarged cups. His brother has glaucoma. He has asthma.
Answer: Suspected primary open-angle glaucoma.

• Ophthalmology assessment (fields, OCT, gonioscopy).
• SLT laser first line, or prostaglandin analogue drops.
• Avoid timolol (asthma).
• First-degree relatives get free eye tests from age 40.

3. A 65-year-old has sudden onset of floaters and flashing lights in the right eye. Acuity is normal; no field loss.
Answer: Probable posterior vitreous detachment.

• Same-day or next-day dilated retinal examination to exclude a retinal tear.
• Safety-net: return immediately with a curtain or shadow, or worsening vision.

4. An 82-year-old with advanced AMD describes seeing small children in Victorian dress in her living room. She knows they aren't real. Cognition is normal.
Answer: Charles Bonnet syndrome.

• Reassure and explain; coping strategies.
• Exclude delirium and Lewy body dementia; review drugs.
• Low vision support; check registration (CVI).

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Key Points

• Always measure visual acuity in each eye; improvement with a pinhole means refractive error.
• RAPD suggests optic nerve or severe retinal disease.
• Never send patients home with local anaesthetic drops; don't start steroid drops without a slit lamp examination.
• Topical timolol can cause bronchospasm and bradycardia.
• Cataract: gradual painless blurring and glare; operate when quality of life is affected.
• Endophthalmitis after cataract surgery is a same-day emergency.
• Open-angle glaucoma is silent until late — found at routine eye tests; SLT laser or prostaglandin drops first line.
• Hypermetropia, older age and East Asian ancestry raise the risk of angle closure; anticholinergics and topiramate can trigger it.
• New flashes and floaters need urgent dilated examination to exclude a retinal tear.
• DVLA Group 1: read a number plate at 20 m, acuity 6/12, 120° horizontal field.
• Charles Bonnet syndrome: vivid hallucinations with sight loss and preserved insight — reassure.

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Guidelines and Further Reading

• NICE NG77: Cataracts in adults — management
• NICE NG81: Glaucoma — diagnosis and management
• DVLA: Assessing fitness to drive — a guide for medical professionals (visual disorders)
• The Royal College of Ophthalmologists (RCOphth) — clinical guidelines and patient information
• College of Optometrists — Clinical Management Guidelines
• RNIB and Macular Society — patient support
• BNF — for current doses

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