One of the more curious conditions in ophthalmic dispensing is diabetes. How can one's sugar level affect one's eyes? If you have been in this field for any good length of time, you would have very likely run into a patient who picked up their glasses without a hitch, only to come back some time later complaining of blurry vision. It's normal to see a child's prescription fluctuate or increase because they're still growing. An adult is a different story. As an adult, one's eye prescription doesn't fluctuate greatly without some underlying reason.

Diabetes mellitus is a disorder that affects one's metabolism. According to WebMD, diabetes is estimated to affect 18.2 million people, 5.2 million of which go undiagnosed. There are three main types of diabetes: type 1, type 2, and gestational. There are other forms of diabetes that remain difficult to classify because their underlying cause is unclear. It is important to understand the role of insulin in the body. Insulin is a hormone produced by the pancreas. The bloodstream in the presence of glucose, a simple sugar utilized by our cells and the main source of fuel in the body, utilizes insulin to let the cells know to take in the glucose.

Most people are familiar with type 1 diabetes. This form of diabetes is classified as an auto-immune disease and requires regular insulin shots in order to survive. In type 1 diabetes, the body's immune system attacks the insulin producing cells in the pancreas. There is no known reason as to why this response happens. Some symptoms include increased thirst, increased hunger, frequent urination, blurred vision and fatigue.

Type 2 diabetes has been gaining a lot of coverage in the news because of the "obesity epidemic" in this country. This type is known as insulin resistant diabetes. The pancreas in type 2 diabetes seems to produce insulin, but is resistant to the insulin produced. Today, more children are now being diagnosed with this form of diabetes in greater numbers. The majority of those who have diabetes are also obese, so a strong correlation exists between inactivity, obesity and diabetes.

Gestational diabetes is usually a transient form of diabetes that occurs during pregnancy. Even though this form of diabetes may resolve on its own, it still has potential to damage both mother and child. This type of diabetes accounts for 2%-5% of all pregnancies.

Diabetics are prone to high blood pressure and heart disease. Nerve damage may also result in the extremities. The incidence of kidney disease and stroke are higher in those who suffer from diabetes than normal.

Diabetes has some serious ocular manifestations. There are four stages of diabetic retinopathy: mild non-proliferative diabetic retinopathy (mild NPDR), moderate NPDR, severe NPDR, and proliferative diabetic retinopathy (PDR). PDR is considered to be the most advanced stage of diabetic retinopathy. It is characterized by neo-vascularization of the retina. Some of the new vessels that have grown into the retina may bleed and cause blurry vision and even cause vision loss.

Macular edema, which is a swelling of the portion of the retina responsible for our central vision, can, if left untreated, result in vision loss. Macular edema can occur at any stage of diabetic retinopathy. Age-related cataracts may form earlier in those with type 1 and type 2 diabetes. According to the National Eye Institute, a diabetic is twice as likely to develop glaucoma.

It has always struck me as odd when a patient doesn't remember what their medical history is. I find that most of my time is spent trying to gather their medical history and reinforce whatever information was said to them. When dealing with diabetic retinopathy and other issues related to diabetes, there will be two primary issues: blurred vision and permanently decreased visual acuity. As in the introduction, it is important to remind the patient that elevated blood sugar may be the cause of their blurry vision. Once the levels normalize, their glasses should correct their vision provided that there isn't a significant lapse between updates in their prescription. When dealing with permanently decreased visual acuity, I use the camera analogy. If the camera film is damaged, changing the lens on the camera will not improve the image. At this point it is imperative to reinforce the need to see an eye doctor regularly and control sugar levels.