Diabetes and the Eye Return

Diabetes can lead to numerous vision problems. When diabetes is poorly controlled, there is an excess amount of sugar in the blood, causing the vessels that supply the eye with blood to thicken and harden, which prevents them from doing their job properly.

In the eye, diabetes affects primarily:

• The iris: located on the surface of the eye, it gives the eye its colour.
• The crystalline lens: suspended behind the iris, this biconvex structure acts like a lens, directing and focusing the light on the retina.
• The vitreous humour: a transparent jelly-like substance that gives the eye its round shape and helps the flow of oxygen to the eye.
• The retina: a thin layer of cells lining the back of the eye, it senses images, colours, shapes and motion;
• The optic nerve: situated at the back of the eye, it transmits the images captured by the eye to the brain.

Diabetes is not a primary cause of cataracts or glaucoma. However, these eye diseases tend to appear prematurely in people with diabetes.

Diabetes complications mainly affect:

• the retina (retinopathy)
• the crystalline lens (cataracts)
• the iris (rubeosis)
• internal eye pressure (glaucoma)

When to see your doctor

Regular eye exams are essential since the effect of diabetes on the eye usually produces no symptoms until well advanced. The recommended frequency of eye exams is as follows:

Recommandations adapted from Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Treatment of Diabetes in Canada.

If you have retinopathy, the frequency of your eye exams will vary depending on the severity of the disease.

Signs to watch out for

In addition to annual eye exams, consult an optometrist or ophthalmologist if you have the following symptoms:

• Blurred vision that changes from one day to the next
• Dry eyes
• Double vision, sudden onset
• Problems distinguishing colours
• Night vision that suddenly becomes much worse (when driving)
• Vision loss (very blurry, as if seeing through a mist)

Prevention

The best way to prevent or delay the onset of eye diseases is still optimal control of your blood glucose (sugar) levels.

It is also beneficial to:

• control your blood pressure
• control the levels of fat (cholesterol) in your blood
• quit smoking

See also:

Book available in the online store: Diabetic Retinopathy

Research and text: Diabetes Québec Team of Health Care Professionals

June 2014

References:

Boyd et al. (2013) “Retinopathy,” Canadian Diabetes Association 2013 Clinical Practice Guidelines for the Prevention and Treatment of Diabetes in Canada, (Canadian Journal of Diabetes, vol. 37, pp. S513-S517), Canadian Diabetes Association.
Arbour, J. D. and Labelle, P. (2013), La rétinopathie diabétique, Montréal: Annika Prance Éditeur.

Macular edema is a complication of diabetic retinopathy (proliferative or nonproliferative) characterized by a thickening of the retina in a very specific spot, the macula, located at the back of the eye and responsible for visual acuity.

In macular edema, the retinal tissue absorbs liquid leaking from abnormal and swollen blood vessels. This causes image distortion and blurred vision. Fatty deposits may form, particularly in people with high cholesterol. Central vision is affected, causing an inability to read or recognize faces.

Prevention

Macular edema is a complication of retinopathy, which is a completely preventable disease.

Treatment

There are currently three treatment options:

• laser
• injections
• surgery

Laser

The doctor uses a laser to “plug” the abnormal leaks causing the edema. This slows the progression of the edema or makes it disappear if it is very small and localized. The laser is used on a tiny area of the macula. This type of treatment reduces the risk of vision loss by about 50%.

Injections of antiangiogenic drugs

These injections inside the eye decrease abnormal blood leakage and repair the blood vessels. This technique is based on the same principle as the laser but has proven to be superior. The primary goal is to stabilize vision.

Also used to treat macular degeneration, these drugs have proven effective in stopping macular edema. Although these drugs are not always effective when the edema has been present for a long time, more and more patients are responding well to injections. They are not painful or complicated, but require several sessions every four to six weeks.

Surgery

Macular edema can be aggravated by the presence of scars, which a surgeon can remove with a vitrectomy (removal of the eye’s inner, vitreous gel).

Adapted from: Benhaberou-Brun, Dalila, Nurse, M.Sc. (Autumn 2011),” La prunelle de vos yeux,” Plein Soleil, Diabète Québec, pp. 22-24.

Optometrists play an important role in the detection of diabetes. During a complete eye exam for vision and eye health, they are often the first to notice signs of diabetes. An optometrist may then refer a person to a family doctor, or to an ophthalmologist for more advanced eye treatment.

How an eye exam is conducted

    1. Vision test

The eye exam of a diabetic person or a suspected diabetic is no different from that of a non-diabetic person. However, the examiner pays particular attention to the following:

• muscle balance or binocular vision, to make sure that the eyes are properly coordinated and that the muscles are not affected;
• the presence of a visual defect that fluctuates over time;
• an inability to focus at different distances (accommodation);
• abnormal colour vision.

This exam also results in recommendations for the best vision correction.

When diabetes is undiagnosed or unstable, a person’s vision often fluctuates. The need to frequently change your prescription for eyeglasses over a very short time period is sign of diabetes or poor diabetes control.

    2. Eye-health exam

The eye exam also looks for the presence of eye diseases. The optometrist dilates the pupils with eye drops to get a better view of all the inner parts of the eye.

The eye exam can detect the presence of diabetes by examining:

• the retina, for signs of retinopathy;
• the optic nerve, for signs of glaucoma;
• the crystalline lens, for early signs of cataracts;
• the inner structure of the eye, the iris and cornea, to detect the presence of abnormal blood vessels and signs of glaucoma;
• eye pressure, combined with an assessment of the visual field, to detect the presence of glaucoma.

Retinopathy affects 20% of people with type 2 diabetes by the time they are diagnosed, and most type 2 diabetics will develop it after living with the disease for 15 years.

If these preliminary tests indicate a problem, additional tests using imaging equipment may be recommended to study the retina in more depth. When necessary, a person with diabetes will be referred to an ophthalmologist for the required treatments.

Research and text: Diabetes Québec Team of Health Care Professionals

Scientific review: Langis Michaud, O.D., M.Sc. FAAO (Dipl)

July 2014