Retina diagnostics: how the retina is examined
The retina is the light-sensitive layer at the back of the eye. It turns light into signals that the optic nerve carries to the brain. Its centre, the macula, gives the sharp vision used for reading and recognising faces. This page explains how the retina is examined and what each test adds.
In brief
- The starting point is always a dilated examination by the doctor.
- An OCT scan shows the layers of the central retina and measures swelling.
- OCT angiography maps blood flow in the small retinal vessels without a dye injection.
- Ultra-widefield imaging records a wide photograph of the retina for comparison over time.
- The scans and photographs are painless. Plan for more than an hour, and do not drive yourself home.
Who is usually advised to have a retina evaluation
- Everyone with diabetes, at regular intervals, whether or not vision is affected.
- People with blurred, distorted or missing patches of central vision.
- People with new floaters, flashes of light, or a shadow at the edge of vision.
- People with high blood pressure or a past blockage of a retinal blood vessel.
- People who are very short-sighted.
- People with age-related macular degeneration, or a family history of it.
- People taking certain long-term medicines that their physician has said need eye monitoring.
Conditions these tests look for
- Diabetic retinopathy: damage to the small blood vessels of the retina from diabetes.
- Diabetic macular oedema: swelling at the centre of the retina.
- Age-related macular degeneration: wear of the macula with age, in a dry form and a wet form.
- Retinal vein occlusion: a blocked vein in the retina, often linked to blood pressure.
- Macular hole and epiretinal membrane: changes at the retinal surface that distort central vision.
- Retinal tears and thinning at the edge of the retina.
- Inflammation at the back of the eye.
The tests, and which question each one answers
| Test | What it shows | What it does not show |
|---|---|---|
| Dilated examination by the doctor | The whole retina, in depth, including the far edge. The doctor can look at any area from different angles. | It leaves no picture to compare later, and cannot measure fine thickness. |
| OCT scan | The central retina in cross-section: its layers, fluid and thickness, in fine detail. | The outer retina. Blood flow. |
| OCT angiography | A map of blood flow in the small retinal vessels, without a dye injection. | Leakage from vessels. Areas beyond the scanned region. |
| Ultra-widefield retinal imaging | A photograph of a wide area of the retinal surface, kept as a record. | The layers of the retina. The outermost edge is sometimes hidden by the eyelids. |
No single test covers everything, which is why they are combined. The doctor chooses the ones that fit the question in your eye.
What a retina visit involves
- History: your symptoms, how long you have had diabetes or blood pressure if you do, your recent sugar control and your medicines.
- Vision and eye pressure are measured.
- Dilating drops are put in. They take 20 to 30 minutes to work.
- The doctor examines the retina with a bright light and lenses.
- Scans or photographs are taken if they are needed.
- The doctor explains the findings and shows you the images.
How to prepare
- Arrange not to drive yourself home, and bring sunglasses. See before your visit.
- If you have diabetes, bring your recent blood sugar and HbA1c reports and your medicine list.
- Bring earlier retina reports, scans and photographs, and details of any earlier laser or injections.
- Eat normally and take your usual medicines. No fasting is needed.
What happens after the tests
What follows depends on the finding. For many people it is a date for the next check. Diabetic changes in the early stages are usually watched, alongside control of blood sugar, blood pressure and cholesterol with your physician. Swelling at the macula from diabetes or a vein blockage, and wet macular degeneration, are commonly treated with a course of intravitreal injections, which are given at the hospital. Where another form of treatment is appropriate, the doctor explains it and arranges the next step with you.
What these tests cannot do
- They describe the retina on the day of the test. Conditions such as diabetic retinopathy change over time, so a normal result does not remove the need for the next check.
- They cannot predict with certainty how a condition will behave or how an eye will respond to treatment.
- Image quality depends on a clear view. Cataract or bleeding inside the eye can limit what is seen.
- They do not replace care of the underlying condition. In diabetes, control of blood sugar and blood pressure matters as much as anything done for the eye.
Symptoms that need a same-day examination: a sudden shower of new floaters, flashes of light, a curtain or shadow across part of the vision, or sudden loss or distortion of vision. During OPD hours, call 80966 65550. The hospital is a daytime OPD clinic. When it is closed, go to the emergency department of a 24-hour hospital.
Retina diagnostics at the hospital
Dr. P. Siva Reddy Eye Hospital has OCT, OCT angiography and ultra-widefield retinal imaging on site, and intravitreal injections are given here. The doctor reads every scan and photograph together with your examination. The equipment list is on the facilities and equipment page.
Frequently asked questions
Are retina tests painful?
The scans and photographs are painless, and nothing touches the eye. Dilating drops may sting for a few seconds. The bright light used during the examination can be uncomfortable but does not harm the eye.
How long does a retina evaluation take?
Longer than an ordinary visit, so plan for more than an hour. Dilating drops take 20 to 30 minutes to work, and the examination and any scans follow.
Can I drive after a retina evaluation?
Dilating drops are almost always used, and they blur near vision and increase glare for a few hours. Arrange not to drive yourself home.
I have diabetes and my vision is fine. Do I still need a retina check?
Yes. Diabetic changes in the retina commonly cause no symptoms in the early stages. Regular retina checks are advised for everyone with diabetes, at an interval the doctor sets for you.
Will I need all of these tests?
No. The dilated examination comes first. A scan or photograph is added only when it would answer a question the examination has raised, and the reason is explained before it is done.
What happens if the tests find something?
The doctor explains what was found and what the options are. Depending on the condition, that may be observation with a repeat test, better control of diabetes or blood pressure with your physician, a course of intravitreal injections, or another treatment the doctor will discuss with you.
I have new floaters and flashes. Which test do I need?
A dilated examination of the retina by the doctor, on the same day. Scans and photographs do not replace it, because the area that needs checking is the far edge of the retina.
Related pages
Appointments and contact
You can reach Dr. P. Siva Reddy Eye Hospital on WhatsApp or by phone during OPD hours.
OPD hours: Monday to Saturday, 10 AM to 2 PM and 4:30 PM to 7 PM. Closed on Sunday.