The comprehensive eye examination: what it covers
The difference between a sight test and a comprehensive eye examination is not how long it takes. A sight test tells you how well you see today; a comprehensive examination tells you what state the eye is in — a different question entirely, because most serious eye disease begins quietly.
Why an eye examination is not just a sight test
Most people come for an eye test when something is blurred, expecting to leave with a prescription. But most of the eye diseases that matter do not begin with blurring. Glaucoma damages peripheral vision years before the centre is affected. Diabetic retinopathy develops in complete silence until an advanced stage. Early macular degeneration is visible on examination long before it is felt.
Hence the distinction: a sight test answers how well you see today. A comprehensive eye examination answers what state the eye is in — and what to expect.
What a comprehensive examination covers
- History — the complaint, background conditions (diabetes, hypertension, autoimmune disease), medications, previous eye surgery, and a family history of glaucoma, macular degeneration or retinal detachment. A large share of the diagnosis is settled here.
- Visual acuity — distance and near, each eye separately.
- Refraction — measuring the focusing power of the eye and establishing the right prescription.
- Intraocular pressure — a brief measurement, and the central test for detecting glaucoma.
- Slit-lamp examination — a microscope that allows the eyelids, conjunctiva, cornea, iris and lens to be examined under magnification. This is where dryness, inflammation, cataract and signs of intraocular inflammation are identified.
- Dilated fundus examination — the part that cannot be skipped when the question concerns the retina. Only with dilation can the full periphery of the retina be reviewed, which is where most tears form.
Imaging: what each test shows
- OCT — a non-invasive, painless optical scan taking seconds, showing a cross-section of the retinal layers to within microns. It identifies swelling, fluid, epiretinal membrane, macular hole, and thinning of the nerve fibre layer in glaucoma. It is also the main tool for follow-up, because it allows precise comparison between visits.
- Fundus photography — a colour record of the retina, a baseline for comparison over years.
- Angiography — imaging of the retinal blood vessels, used where leakage, occlusion or new vessels are suspected.
- Visual fields — functional mapping, mainly in monitoring glaucoma.
- Ultrasound — where bleeding or opacity prevents a direct view of the retina.
The drops take effect over about 20 minutes, and the effect lasts between four and eight hours. During that time near vision is blurred and the eyes are very sensitive to light.
Do not drive after an examination with dilating drops. Come with someone and bring sunglasses, and do not plan work that requires reading immediately afterwards.
Who should be examined, and how often
These are general guidelines. The right interval is set individually, according to the findings:
- People with diabetes — a retinal examination at least once a year, even when vision is excellent. This is the most important recommendation on this list.
- From age 50 — periodic examination, even without complaints.
- A family history of glaucoma, macular degeneration or retinal detachment — earlier and more regular monitoring.
- High myopia — periodic retinal review, because of the raised risk of tears.
- After eye surgery or trauma — as directed by the treating doctor.
- Long-term steroid or certain other medications — under dedicated monitoring.
- Any sudden change — regardless of age or of the monitoring interval.
What to bring
- Photo ID and a referral, if you have one.
- The glasses or lenses you currently use.
- Summaries of previous visits to an ophthalmologist.
- Previous imaging — OCT, retinal photographs or angiography, even if done elsewhere. A comparison with last year is sometimes worth more than any new test.
- An up-to-date list of medications, drops included.
- Someone to accompany you, if dilation is expected.
Flashes of light, a sudden shower of floaters, a shadow or curtain in the visual field, a sudden drop in vision, a red painful eye with light sensitivity, or sudden double vision — all of these require immediate attention rather than waiting for a scheduled examination.
And what a single examination cannot do
One examination is a snapshot. Some diagnoses — glaucoma, macular degeneration and inherited retinal disease foremost among them — are made precisely by comparing examinations over time. Keeping the records, and returning at the intervals agreed, is worth more than a single examination however thorough.
The information in this article is general information only. It does not constitute medical advice or a diagnosis, and it is not a substitute for examination by a doctor. Every case is different, and nothing here should be relied on for medical decisions. In the event of a sudden loss of vision, flashes of light, a sudden shower of floaters or a shadow falling across your vision, seek urgent medical care immediately.
