Patient guide

Diabetic eye exams: what is checked, and why every year

By Dr. Sam Khoury, OptometristReviewed November 20266 min read

Call the same day for sudden blurring, a sudden shower of floaters, a dark shadow or curtain, or a sudden loss of vision in either eye. Call (609) 246-0236. If the office is closed, or you cannot reach us, go to a hospital emergency room — most have an ophthalmologist on call.

Diabetes damages small blood vessels, and the retina at the back of the eye is one of the places it shows first. The early changes cause no symptoms at all. They can be present for years while vision stays perfect, and the treatments that protect sight work best when started before vision has changed. That is the whole reason for a yearly exam that feels, most years, like it finds nothing.

This guide covers what diabetes does to the eye, what the exam involves here, how often it is needed, and what the numbers you already track for your diabetes mean for your eyes.

What the exam involves

It is a comprehensive eye exam with the retina as the focus. Everything is done here, at the same visit, and the images become the baseline every later year is compared with.

• Vision and eye pressure, with pressure measured without the puff of air.
• Widefield retinal imaging, roughly 200 degrees of the retina in one image without drops, which is how small bleeds in the periphery are found and tracked year to year.
• A layer-by-layer scan of the macula (OCT), which shows swelling before it affects vision and measures it to a few thousandths of a millimeter.
• Dilation when it adds something: a first visit, a finding that needs a closer look, or a view the imaging cannot reach. Many routine yearly visits are completed without drops.
• The lens, the optic nerve and the drainage angle, because cataract and glaucoma come earlier with diabetes.

A written report goes to your primary care doctor or endocrinologist after every visit, with the stage of any retinopathy and the interval to the next exam. Tell us who manages your diabetes so it reaches the right desk.

What protects your eyes

The same things that protect the rest of you, and the evidence for them in the eye is unusually strong.

• Blood sugar. In the landmark trials, tight control cut the onset and progression of retinopathy by well over half. Every point of A1C matters, and there is no threshold below which it stops helping. The right target for you is set by the doctor who manages your diabetes.
• Blood pressure. Controlling it reduces retinopathy progression independently of sugar. The vessels are the same small vessels.
• Cholesterol. Treating it lowers the leakage that causes macular swelling.
• Not smoking. Smoking damages the same vessels from the other direction.
• The yearly exam. Because none of the above shows you what is happening inside the eye, and because the treatments work best before symptoms.

Common questions

My vision is fine. Do I really need this every year?

Yes. Perfect vision and early retinopathy coexist comfortably for years. The exam is for finding the changes while they are still silent, which is when treatment protects the most. Most years it will find nothing, and that is the result you want on record.

My primary care doctor took a photo of my retina. Is that the same?

Screening photographs in a medical office are a good safety net for people who would otherwise not be examined at all, and a normal one is reassuring. They do not replace an exam. A single photograph covers less of the retina, cannot measure macular swelling the way a scan can, and does not check pressure, the lens, or the optic nerve. If a screening photo was abnormal or unreadable, that is a reason to come in, not a diagnosis.

Will I be dilated?

Sometimes. Widefield imaging answers most of what a yearly visit is asking without drops, and many patients are not dilated. A first visit, a finding that needs a three-dimensional look, or a view the imaging cannot reach calls for dilation. If you are dilated, near vision is blurry for about four hours, so bring sunglasses.

My vision changes from day to day. Is that the retinopathy?

Usually not. Swings in blood sugar change the shape of the lens inside the eye and shift the focus for days at a time. It settles as the sugar does, and it is a reason to wait before buying new glasses. Sudden blurring with floaters or a shadow is different and is a same-day call.

I take Ozempic or Mounjaro. Does that change anything?

A rapid improvement in blood sugar can temporarily worsen retinopathy that is already there, so an exam around the time you start, and closer follow-up for the first year or so if you have retinopathy, is sensible. It is a reason to be checked, not a reason to avoid better control. More on GLP-1 medications and the eye.

Does a diabetic eye exam go through my vision plan or my medical insurance?

A diabetic eye exam is a medical visit and goes through your medical insurance, even though you are seeing an optometrist, and Medicare covers one each year. Vision plans cover routine eye exams and eyewear; medical plans cover conditions. Many patients carry both and are not sure which applies. Vision plan or medical insurance explains the difference, and a call with your plan details before you book sorts it out beforehand rather than afterwards.