a role in the early detection of this devastating disease.
of 20.8 million people, or 7% of the U.S. population has some form of diabetes,
according to the National Diabetes Information Clearing-house.1 Of these,
14.6 million have been diagnosed, while a total of 6.2 million people re-main undiagnosed.1
Further, about one in every 400 to 600 children and adolescents has Type-1 diabetes.
Regional studies and clinically based reports propose that Type-2 diabetes is being
diagnosed more often in chil- dren and adolescents, especially in those of Native
American, Af-rican American and Hispan-ic/Latino American descent.1 Also,
diabetes is the leading cause of new cases of blindness among adults ages 20 to
74, and diabetic retinopathy causes 12,000 to 24,000 new cases of blindness each
Although you are no doubt aware of
the clinical signs and symptoms of diabetic retinopathy, you should also be aware
of the clinical signs and symptoms of this entire disease, as patients may be more
likely to see you than their primary-care practitioner on a regular basis (see "Essentials
of Diabetic Retinopathy," page 31). This means you play a vital role in the early
detection of this disease and in the preservation of these patients' quality of
Here, I will provide an over-view
of diabetes and how you can screen your patients for this disease, so you can refer
them to their primary-care physicians for a definitive diagnosis in a timely fashion.
Diabetes is "a group of meta-bolic
diseases characterized by hyperglycemia (an abnormally high level of glucose in
the blood), resulting from defects in insulin secretion, insulin action or both."2
Insulin is a polypeptide hormone, produced by the beta cells of the islets of Langerhans of the pancreas. It regulates
the metabolism of glucose (which provides the body with energy) as well as other
nutrients. Glucagon, a hormone also secreted by the pancreas, opposes the effects
of insulin. These two hormones work together to maintain a homeostatic mechanism
for blood glucose levels. Insulin enters the blood stream shortly after a person
eats, particularly those food items rich in carbohydrates. When the body needs glucose,
insulin facilitates its use to meet the body's needs. Any excess glucose converts
to glycogen, which is stored in the liver or muscle or as fatty tissue.
Glucagon is secreted during the fasting
states of the body by the alpha cells of the Islet of Langerhans. Glucagon elevates
blood glucose levels by one of three mechanisms:
1. Glycogenolysis: breakdown of stored
glycogen in the liver to make glucose.
2. Gluconeogenesis: conversion of
non-glucose substrates into glucose.
3. Glucose sparing: a process in
which ketones are formed in the liver. (Ketones are substanc-es made if your diet
doesn't contain enough carbohydrates to supply the body with sugar [glucose] for
energy or if your body can't use blood sugar [glucose]
Diabetes falls into one of two categories:
Type-1 and Type-2:
Type-1 accounts for approximately
10% of all diabetes cases. Patients with Type-1 diabetes are typically young, thin
and under-go a progressive loss of endogenous insulin leading to hypergly- cemia.
The peak incidence of Type-1 diabetes: between ten and 13 years of age. In fact,
95% of patients who have Type-1 diabetes are diagnosed before age 25.3
This form of the disease is characterized by an autoimmune process, which causes
beta cell destruction, usually leading to absolute insulin deficiency.
Type-2 diabetes accounts for more
than 90% of the total disease population. Type-2 diabetes typically occurs in people
who are older than age 40, are obese and/or have a family history of diabetes.
This form of the disease involves
two major pathogenetic mechanisms: impaired islet-cell function (impaired insulin
secretion) and impaired insulin action (insulin resistance or decreased insulin
sensitivity). Insulin resistance occurs when normal concentrations of insulin elicit
a less- than-normal biologic response. When this patient eats, some insulin secretion
still occurs, but at reduced levels. Thus, the body cannot absorb and utilize all
Patients who have Type-2 diabetes
usually aren't dependent on insulin to maintain their life or prevent ketosis (when
the body burns its own fat for fuel), but insulin is commonly necessary
for them to maintain reasonable blood glucose concentrations.
Ultimately, diabetes alters the body's
ability to metabolize carbohydrates. Chronic hypergly-cemia results in fats and
proteins causing widespread damage throughout the body. This elevated blood sugar
eventually causes damage to the kidneys, nerves, heart and blood vessels and the
eyes in the form of ne-phropathy, neuropathy and leaky blood vessels.
The chronic complications of diabetes
include organ-specific degenerative processes, such as accelerated vascular disease
and neurologic deficits. The vascular disease consists of both microangiopathy and
macroangiopathy. The former is a disease of the capillaries specifically associated
with diabetes. It's characterized by thickening of capillary basement membranes
and manifests clinically mostly in the retina and kidney. The latter is an accelerated
form of atherosclerotic disease of the arteries that usually manifests clinically
in the coronary arteries, cerebral arteries and peripheral vessels of the low-er
Screening for diabetes
To screen your patients for diabetes,
include the following eight questions on your patient history
1. Do you have a first-degree relative
(sibling, parent, child) who has diabetes? If the patient answers "yes," this means
he is genetically predisposed to developing the disease.
2. Have you recently given birth
to a baby weighing more 9 lbs? If the patient answers "yes," this means she is at
high risk for diabetes because women with elevated blood sugar tend to have large
3. Were you diagnosed with gestational
diabetes during your pregnancy? If the patient an-swers "yes," this is important
because women who've suffered from gestational diabetes are more likely to develop
diabetes later in life.
4. Do you have hypertension? If the
patient answers "yes," this is important, as patients who have hypertension are
at higher risk for developing diabetes.
5. Do you have high cholesterol?
If the patient answers "yes," this is significant, as a high-density lipoprotein
level of 35mg per (deciLiter) dL (0.90mmol per L) or lower and/or a triglyceride
level of 250mg per dL (2.83mmol per L) or higher puts a person at great risk for
6. Have you been experiencing an
increase in thirst (polydipsia)?
Have you been experiencing an increase in appetite (polyphagia)?
8. Have you been urinating more frequently
"Yes" answers to questions six through
eight indicate the classic triad symptoms of Type-1 diabetes. These patients are
prone to ketoacidosis, a life-threatening complication caused by severe insulin
deficiency, which can cause diabetic coma and death.4
Unlike Type-1 diabetes, in which
the symptoms are pro-nounced, the onset of Type-2 diabetes
is gradual. Therefore, primary-care physicians often diagnose Type-2 diabetes in
asymptomatic patients during routine physical examinations when these patients'
blood work shows elevated blood glucose levels.
If a patient older than age 45 presents
for his annual exam, make screening for diabetes a yearly routine. This is because
younger patients are less likely to develop adult-onset diabetes. If the patient's
answers to the screening questions indicate he isn't a suspect for diabetes, repeat this screening at three-year intervals,
as this is standard protocol.
If however, this patient or any other
patient answers "yes" to any of the history questions, consider referring him or
her to a primary-care physician for diagnostic testing for diabetes.
Because patients may be more likely
to see you than their primary-care practitioner on a regular basis, you have the
oppor- tunity to detect diabetes in these patients early by educating yourself on
all the clinical signs and symptoms of this disease, passing this information to
your patients, and including the necessary questions in your patient history form.
Remember: Learning all you can about the systemic diseases that have ocular manifestations
makes you a true pri- mary-care optometrist that patients will seek.
1. National Diabetes Information
Clearinghouse (NDIC). National Diabetes Statistics. http://diabetes.niddk.nih. gov/dm/pubs/statistics/
(Accessed January 9, 2007).
2. The expert committee on the diagnosis
and classification of diabetes mellitus. Report of the expert committee on the diagnosis
and classification of diabetes mellitus. Diabetes Care 2003 Jan;26 (Supp 1):s5-20.
3. Saydah SH, Loria CM, Eberhardt
MS, Brancati FL. Subclinical states of glucose intolerance and risk of death in
ESSENTIALS OF DIABETIC
retinopathy is the result of chronic elevation of blood glucose levels. It's usually
more common in patients with uncon-trolled diabetes or those who have long-standing
The production of "free
radical" reactive oxygen species by the mitochondria generates several harmful biochemicals,
such as vascular endothelial factor (VEGF), protein kinase C (PKC) and advanced
glycosalated end products. The end result: damage to the integrity of retinal capillaries,
causing them to become leaky.
The hallmark signs of diabetic
retinopathy include microaneurysms, dot-and-blot intraretinal
hemorrhages and hard exudates. Many patients also demonstrate cotton-wool spots,
intraretinal micro-vascular abnormalities (IRMA), neovascularization of the disc
(NVD), neovascularization elsewhere (NVE) and diabetic macular edema.
The classification of diabetic
retinopathy has historically been based on the Early Treatment Diabetic Retinopathy
Study (ETDRS), in which diabetic retinopathy was classified into "no diabetic retinopathy,"
"background retinopathy," "pre-proliferative and proliferative." the International
Clinical Diabetic Retinopathy Disease Severity Scale is the newer classification
(visit www.icoph.org/standards/pdrclass. html).
Proper management of diabetic
retinopathy is heavily dependent on the stage of the disease. So, it ranges from
regular monitoring to photo-documentation to laser intervention. Your underlying
management is to prevent or minimize diabetic retinopathy in all diabetic patients
via sufficient control of blood glucose levels and proper control of blood pressure
and blood lipids.
Optometric Management, Issue: February 2007