Cataract symptoms and examination

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

A cataract changes how light passes through the eye before it reaches the retina. The lens may become more opaque, scatter light or change its refractive properties, producing symptoms that are not captured by a single high-contrast chart measurement. Someone may read several lines in a well-lit consulting room yet struggle badly with headlight glare or identifying steps. Conversely, visible lens changes may have little effect on the activities that matter to that person. Assessment therefore combines the history, measured vision and an examination that explains the likely source of impairment.

Age-related cataract usually develops slowly and often affects both eyes to different degrees. Patients may describe cloudy vision, faded colours, frequent spectacle changes or multiple images seen by one eye. Ask whether the disturbance persists when the other eye is covered: monocular ghosting has a different diagnostic meaning from binocular diplopia caused by misalignment. Gradual adaptation can hide the extent of disability, so concrete examples about reading medication labels, cooking, hobbies and mobility are often more useful than asking only whether vision is worse.

Finding cataract is not the end of the diagnostic process. Diabetes, macular disease, glaucoma, corneal abnormalities and optic neuropathy can also impair sight, and several may be present together. The clinician should establish which findings plausibly explain the symptoms, which additional tests are needed and what improvement could reasonably follow lens surgery. An unexpectedly poor result from a simple acuity test should prompt a broader examination rather than an assumption that a modest cataract has suddenly become severe.

Key points

Cataract is opacity of the natural crystalline lens and commonly causes gradual, painless visual deterioration.
Ask about glare, night driving, reading, colour perception and the effect on work or independent living.
Measure acuity in each eye with current correction and assess refraction or pinhole response, recognising their limitations.
Examine the lens with a slit lamp and assess the rest of the eye, including the fundus when visibility permits.
Lens opacity and another cause of visual loss can coexist; the presence of cataract does not establish its contribution.
Refer according to functional impact and the person's preferences rather than waiting for a fixed visual-acuity threshold.
No eye drop reverses ordinary established age-related cataract; surgery is discussed when its expected benefit justifies intervention.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Age-related lens change

Changes in lens proteins and structure accumulate with age, reducing transparency and altering light transmission. The rate, anatomical pattern and functional effect vary substantially between individuals and between the two eyes.

Ocular and systemic contributors

Diabetes, previous ocular inflammation, trauma or intraocular surgery can contribute to cataract formation. The associated condition may also affect other eye structures and influence the likely benefit or complexity of surgery.

Medicine exposure

Corticosteroid exposure can contribute to lens opacity, particularly posterior subcapsular changes. Review route, dose and duration while recognising that the underlying inflammatory illness may itself be relevant to the eye assessment.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Light scatter and reduced contrast
An opaque or irregular lens scatters incoming light, degrading retinal image contrast. Bright lights can therefore cause disproportionate glare even when high-contrast distance acuity remains relatively well preserved.
2
Changing refractive properties
Lens changes can alter refractive power and the balance between distance and near vision. A myopic shift may temporarily improve unaided near tasks while distance vision deteriorates and spectacle prescriptions become less stable.
3
Location of the opacity
Nuclear, cortical and posterior subcapsular opacities affect different portions of the lens. Their position relative to the pupil and visual axis helps explain why symptom severity does not map directly to overall lens appearance.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Symptoms and functional change

Clarify onset, progression, laterality, glare, night vision and reading difficulty. Ask which tasks have been abandoned or adapted. A relative may describe reduced confidence outdoors, but the patient's own priorities should lead the decision about further assessment and surgery.

Patterns within the lens

Nuclear opacity can accompany a myopic shift and altered colour perception. Cortical spokes may affect vision according to their relation to the pupil, while posterior subcapsular opacity often causes troublesome glare and near-vision difficulty. These patterns overlap and do not replace an assessment of the entire eye.

History that changes the interpretation

Review diabetes, uveitis, trauma, previous eye surgery and steroid treatment. Establish amblyopia, previous retinal disease and the vision before cataract developed. A lifelong poorer eye and a newly deteriorating better eye have different implications from similar recent changes in both eyes.

Features suggesting another process

Pain, substantial redness, sudden onset, new field loss or neurological symptoms are not the usual presentation of uncomplicated cataract. Metamorphopsia or a relative afferent pupillary defect should widen the assessment. Monocular ghosting can arise from optical causes, but binocular diplopia requires evaluation of alignment and neurological causes.

Red flags requiring action

Sudden visual loss, a new curtain-like field defect or painful redness requires urgent ophthalmic assessment rather than attribution to an existing cataract.
New headache, scalp tenderness or jaw claudication with visual symptoms in an older adult raises concern for giant cell arteritis and needs immediate assessment.
A definite relative afferent pupillary defect or visual loss disproportionate to the lens opacity should prompt assessment for retinal or optic nerve disease.
A child with an absent or white red reflex needs the urgent paediatric ophthalmology pathway; adult age-related cataract advice does not apply.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Monocular visual acuity and refractive assessmentFirst step
Why
Quantify vision and identify a component that improves with optical correction.
Interpretation and limitations
Test each eye separately with the usual spectacles and document the chart and correction used. Pinhole can suggest a refractive contribution, but incomplete improvement is nonspecific and a favourable response does not exclude early cataract. Ask about near vision and binocular function as well.
02
Slit-lamp lens and anterior-segment examination
Why
Confirm lens opacity and identify other anterior eye abnormalities.
Interpretation and limitations
Assess the cornea, anterior chamber, iris, pupil and lens before attributing symptoms to cataract. Dilated examination helps define lens changes when safe. Document opacity type and density alongside signs of inflammation, previous surgery or zonular instability that may affect management.
03
Pupil examination and intraocular pressure
Why
Identify findings suggesting optic nerve dysfunction or pressure-related disease.
Interpretation and limitations
A clear afferent pupillary abnormality needs an explanation beyond ordinary uncomplicated cataract. Pressure and anterior-chamber assessment also inform the safety of pharmacological dilation; a narrow angle requires appropriate specialist judgement before a mydriatic is used.
04
Dilated fundus examination and targeted imaging
Why
Assess retinal and optic nerve disease that may limit vision or surgical benefit.
Interpretation and limitations
Inspect the macula, optic disc and peripheral retina when possible. OCT may clarify suspected macular pathology; it is not a substitute for the clinical examination. If a dense lens blocks the view, ultrasound can assess gross posterior pathology, but cannot guarantee normal macular function.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Uncorrected refractive error

An inaccurate spectacle prescription can cause blur without visually important cataract. Refraction or a helpful pinhole response identifies a correctable component, although refractive error and lens opacity may coexist.

Macular disease

Central distortion, difficulty recognising faces or a central scotoma may arise from retinal pathology. Examine the macula and use appropriate imaging when symptoms or fundus findings suggest a contribution beyond the lens.

Corneal or ocular surface disease

An unstable tear film, corneal irregularity or oedema can produce fluctuating blur and glare. Slit-lamp findings and symptom variation with blinking or time of day help direct further assessment.

Glaucoma or optic neuropathy

Optic nerve disease may reduce the visual field, colour function or acuity and can coexist with cataract. Disc assessment and pupil findings help identify when lens opacity is an incomplete explanation.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01Initial assessmentEstablish the likely source of visual impairmentFirst stepA patient reports gradually worsening vision without an acute ocular warning symptom.

1Describe the functional problem, measure corrected vision in both eyes and review relevant ocular, systemic and medicine history.
2Examine the anterior segment and lens, assess pupils and pressure and inspect the fundus when safe and possible.
3Investigate additional findings that the cataract does not adequately explain, rather than treating lens opacity as a complete diagnosis.
4Explain the findings and distinguish changes amenable to spectacles from limitations likely to persist while the cataract remains.

02Mild functional effectSupport vision and arrange reassessmentCataract is present but current activities remain acceptable to the patient.

1Offer an up-to-date refraction where useful and discuss lighting, contrast, magnification or practical adaptations according to the task.
2Agree an appropriate review through the local optometry or ophthalmology pathway and explain what change should prompt earlier contact.
3Discuss driving and other safety-critical activities in relation to current visual ability and applicable standards without assuming a cataract diagnosis alone determines fitness.
4Make clear that sudden pain or visual deterioration needs a different urgent pathway even while routine follow-up is planned.

03Meaningful disabilityRefer for a cataract-surgery discussionLens-related symptoms interfere with activities and the patient wishes to consider treatment.

1Record the person's visual goals, corrected acuity, ocular findings and relevant comorbidities in the referral.
2Explain that surgery replaces the cloudy natural lens with an artificial lens, while other eye disease may limit the eventual improvement.
3Do not restrict referral solely by a numerical visual-acuity threshold; base discussion on impact, risks, benefits and preference.
4Arrange assessment before a very dense cataract creates avoidable complexity, while respecting an informed decision to defer surgery.

Key medicines and prescribing safety1 treatment · regimens, roles and cautions

Dilates the pupil to support examination of the lens and posterior segment when the assessment indicates that this is appropriate.

Tropicamide 1% for diagnostic dilation

The cited adult single-dose product uses one drop into the eye to be examined, followed by a second drop after five minutes; a further drop may be given after thirty minutes if required.

It is contraindicated with narrow-angle glaucoma or a narrow filtration angle because acute closure can occur. Assess pressure and anterior-chamber depth before use; compress the lacrimal sac for one minute to reduce systemic absorption. Explain temporary blur and light sensitivity and avoid driving until vision is suitable. In pregnancy, use only when the assessing physician considers it essential.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Functional visual disability

Progressive impairment can interfere with reading, mobility, driving and daily independence. The consequences depend on binocular function, environmental demands and other disabilities rather than a chart score alone.

Obscured posterior examination

A dense cataract can prevent a useful view of the retina or optic nerve, limiting assessment of coexisting pathology. Further imaging or specialist planning may be needed before discussing the expected outcome.

Lens-related pressure or inflammation

An advanced lens abnormality can occasionally contribute to an acutely painful pressure rise or intraocular inflammation. Such a presentation requires urgent specialist treatment and differs from uncomplicated gradual cataract progression.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

At follow-up, reassess what the patient can do as well as acuity, noting whether glare, falls concerns or difficulty managing medicines has changed.
Reconsider the contribution of retinal, optic nerve or surface disease when the clinical course does not fit the previously documented cataract.
Check whether practical visual support remains adequate and whether the person now wishes to discuss surgery; preferences can change as disability accumulates.
After diagnostic dilation, explain urgent symptoms such as severe ocular pain, headache, nausea or marked visual deterioration that require prompt eye assessment.
Ensure a person awaiting surgery knows how to report a significant change and is not left assuming that every new eye symptom is part of the cataract.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Acuity and glare measure different problems

A chart usually tests recognition of high-contrast letters under controlled conditions. Real environments include bright headlights, low contrast and multiple competing objects, so a reasonable chart result can coexist with substantial disability.

Second sight has limits

A nuclear lens change may reduce the need for near spectacles through a myopic shift, but this is not restoration of a healthy lens. Explain that distance clarity, contrast and later progression may still worsen.

Cataract can hide another diagnosis

When the fundus is difficult to view, describe that uncertainty explicitly. A reassuring ultrasound excludes some large structural problems but cannot predict how well an unseen macula or optic nerve will function after surgery.

Bilateral assessment changes priorities

Similar lens opacities may have very different consequences depending on the fellow eye. Explore amblyopia, retinal disease and reliance on one eye before advising how quickly a surgical assessment might be useful.

11Common pitfallsFrequent interpretation and management errors.

01
Using a fixed Snellen threshold as the sole reason to decline discussion of symptomatic cataract.
02
Attributing all visual impairment to a visible lens opacity without examining the macula and optic nerve.
03
Interpreting improved near vision as proof that the eye is recovering.
04
Using dilation drops without considering a narrow angle or explaining the temporary effect on vision.
05
Leaving sudden visual change on an elective pathway because the patient already has a cataract diagnosis.