What a complete examination includes
Most people think of an eye test as reading letters off a chart to get a spectacle prescription. That is one part of it, and it is the part that tells you least about the health of your eyes.
A full examination covers:
Vision and refraction. Measuring how well you see and what correction you need. This establishes whether reduced vision is simply a focusing problem or something else.
Eye pressure. One of the inputs to assessing glaucoma risk — though not, on its own, a diagnosis.
Anterior segment examination. The lids, cornea, iris and lens examined on a slit lamp. This is where cataract is graded, dry eye and surface disease are picked up, and corneal problems are found.
Dilated retinal examination. Drops widen the pupil so the retina and optic nerve can be examined properly, including the far periphery where retinal tears usually occur. This is the part most commonly skipped in a quick test, and it is the part that finds serious disease.
Additional tests are added where the examination suggests them — an OCT scan, a visual field test, or retinal photography to document findings for comparison later.
Why dilation matters
Undilated, the view of the retina through a small pupil is like looking into a room through a keyhole. You can see the middle; you cannot see the corners. Retinal tears, peripheral degeneration and early diabetic changes sit in exactly the areas a keyhole view misses.
The trade-off is a few hours of blurred near vision and light sensitivity. For an examination that can detect a retinal tear before it becomes a detachment, it is a reasonable one.
Who should be checked, and how often
- Children — before starting school, and then as advised. Squint, lazy eye and refractive error treated early have a far better outcome than the same problems found at ten
- Adults under 40 — every two years if you have no symptoms and no risk factors
- Adults over 40 — annually, because glaucoma and macular disease both become more common
- Anyone with diabetes — annually from diagnosis, without exception, even with perfect vision
- Family history of glaucoma — annually from your thirties
- High myopia — annually, because the risk of retinal tears and detachment is higher
- Anyone on long-term steroids — as advised, since steroids can raise eye pressure
Symptoms that should not wait for a routine check
Book urgently, or go to an emergency service, rather than waiting for a scheduled appointment if you have:
- A sudden increase in floaters or flashes of light
- A curtain or shadow across part of your vision
- Sudden loss or blurring of vision in one eye
- Severe eye pain with redness, haloes around lights, headache or nausea
- Sudden double vision
- Any injury to the eye or chemical splash
What to bring
Bring your current glasses and any previous prescriptions or eye reports — comparison with an earlier result is often more informative than a single reading. Bring a list of your medicines, including eye drops. If you have diabetes or high blood pressure, bring your recent HbA1c and BP readings, because they change how your retina should be interpreted.
Allow a couple of hours, and arrange for someone to travel with you, since you should not drive after dilation.