When we approach the problem of diabetes, we immediately think of blood sugar. Diabetes, in its basic definition, is characterized by high blood sugar caused by insulin resistance. But rarely does the general consensus go beyond sugar levels, insulin injections, and diabetic shock (hypoglycemia), into the complications developed because of the disease, and the lasting effects they can have on a body.
One, among many complications covering mental health to lower limb amputation, is the connection between diabetes and the health of our eyes.
Often we attribute vision degeneration to age or sun exposure, but blood sugar levels have a strong influence on ocular health. Too much sugar causes blurring of the eye’s lens and does damage to the blood vessels that nourish the retina by cutting off blood flow. To understand what that means, let us first look at the structure and function of the eye itself.
Viewing the diagram, the parts of the eye that are most affected by diabetes are:
- the retina: light-sensitive layer of tissue that focuses and converts images for the optic nerve.
- the macula: a part of the retina that specializes in seeing sharp detail
- the aqueous humor: clear fluid that circulates between the cornea and the lens.
- the retinal blood vessels: blood vessels that nourish the retina.
- the lens: a clear structure, made of fibrous material, used to direct light to the retina.
A person with diabetes should be conscious of three possible conditions that occur because of high blood sugar.
People with diabetes are 40% more likely to suffer from Glaucoma than those without diabetes. This risk also increases with age. Glaucoma occurs when pressure builds up in the eye and slows the drainage of the aqueous humor, allowing it to build up in the anterior chamber. The building pressure then pinches the blood vessels that carry nutrients to the retina and optic nerve, leading to a gradual loss of vision. Treatment, depending on how advanced the disease becomes, can range from pharmaceuticals to surgical intervention.
People with diabetes are 60% more likely to have cataracts at a younger age which will develop more quickly than cataracts without diabetic influence. Cataracts are a clouding of the eye’s lens that begins to block light and vision clarity. The clouding is caused by the clumping of protein of which the lens is partially made. For diabetics, the most common form is subcapsular cataracts, in which the clumping occurs at the back of the lens.
If cataracts progress past a liveable point, the only reliable option is the surgical removal of the eye’s lens, which is sometimes replaced by an implant lense. The downside of removing cataracts is that the risk of glaucoma and retinopathy is increased.
Retinopathy is actually a broad term that covers any disorder of the retina caused by diabetes. The category can be broken up into two types, nonproliferative and proliferative retinopathy.
- Nonproliferative Retinopathy is the more common condition. Unfortunately, for most people with nonproliferative retinopathy, there are no noticeable symptoms until the damage was done has progressed far enough to affect vision. What goes unnoticed, however, is quite serious. Retinopathy is caused by the capillaries in the back of the eye ballooning to form pouches that progressively block the blood vessels that maintain a healthy retina.
When nonproliferative retinopathy is undetected or allowed to progress without intervention, the walls of the capillaries weaken as they balloon. These walls begin to leak a fluid between the blood and retina. When this fluid leaks into the macula (the part of the retina that specializes in sharp focus), it called macular edema, which must be treated with focal laser therapy or ocular injections to prevent vision loss.
- Proliferative Retinopathy is a less common, but much more serious progression of retinopathy that develops over years of undetected damage. At this point, the blood vessels are so damaged that they have closed off flow to the retina and macula completely, forcing the body to adapt. Since the original blood vessels are useless, new blood vessels begin to grow in the retina that are weaker and can leak blood that will impair vision. When vision is blocked by blood in this manner, it is called a vitreous hemorrhage.
When it comes to the treatment of proliferative retinopathy, photocoagulation is often used, not to cure, but to prevent further damage from being done to the eye using tiny burns made in the retina to seal leaking blood vessels and stunt further growth. The procedure is done in one of two ways, focal photocoagulation, in which a specific vessel is targeted to stop further vision blurring or scattered photocoagulation that uses hundreds of tiny burns in a polka dot pattern to reduce the risk of blindness due to hemorrhage or retinal detachment. The second of these two treatments carry the risk of peripheral vision loss.
New blood vessel growth can also cause scar tissue to form. The scar tissue eventually shrinks and pulls on the retina causing distortion or retinal detachment, a condition that separates the retinal vessels from much-needed oxygen, and can result in a permanent loss of vision if not immediately corrected with a surgical procedure called a vitrectomy. A vitrectomy is the surgical removal of scar tissue and cloudy fluid from the retina. Unfortunately, once the retina is detached, reattaching it is only successful in approximately half the cases.
At the least, there is no denying that all of these complications are unpleasant. But what’s truly unfortunate, is that changes that can be made as a diabetic to keep vision impairment at bay, are rarely acted upon. Glaucoma, cataracts, and retinopathy are not altogether avoidable, as they have causes other than diabetes through which they can become a problem. It is true that injury, illness, medication, and genetics all play a part in our overall health, but that’s exactly why it’s so important to take charge of what we can. Simple choices like diet, exercise, and paying attention to sugar levels, will be the difference between blinding ourselves and seeing the world through healthy eyes.