Common Myths & Misconceptions
About Diabetic Eye Disease
Paul Chous, M.A., O.D. Doctor of Optometry
Type 1 diabetic since 1968
I
was recently asked by an interviewer to discuss common myths patients
have about their eyes and vision, and it got me thinking. Over the years,
I have compiled a mental list of patient (and physician) misunderstandings
about diabetes and its effects on the eyes, and thought I might share
at least some of them with you.
1. Good visual acuity on a chart means that a patient
with diabetes has healthy eyes. Many serious eye diseases do not affect
central vision until late in their genesis. I have examined many patients
with severe proliferative diabetic retinopathy, diabetic macular edema
and glaucoma who have had 20/20 or better visual acuity. Good eyesight
definitely does not mean there is no diabetic eye disease.
2. Patients with diabetic retinopathy should not engage
in vigorous physical activity. Although there is merit in being cautious,
it is important for patients to understand that such restrictions concerning
exercise and retinopathy apply to neither the majority of diabetics,
nor even to the majority of patients with diabetic retinopathy. In fact,
the only group of patients at risk for retinal bleeding associated with
exercise are those with untreated, recently treated or actively bleeding
proliferative diabetic retinopathy, as these patients have abnormal
blood vessels that can be broken quite easily. There is absolutely no
ophthalmic reason that people with non-proliferative retinopathy or
those with successfully treated proliferative retinopathy cannot participate
in vigorous physical activity, including moderate resistance (weight)
training, as fragile new blood vessels (neovascularization) either do
not exist or have regressed following laser therapy.
3. Poor visual acuity means that diabetes has damaged
my eyes. The main reason most people with diabetes do not see well on
an eye chart test is the same reason other people don’t see well
on the eye chart – uncorrected refractive error. Poorly controlled
diabetics are notorious for refractive fluctuations, but the vast majority
of them (including many of those with vision threatening diabetic eye
disease) are capable of seeing clearly. Such patients need to be educated
that the quality of their lens prescription depends, ultimately, on
how well they are able to control their blood sugars, as well as the
quality and consistency of eye examinations.
4. All patients with diabetes need to see an ophthalmologist,
not an optometrist. My aim here is not to augment what has often been
a contentious relationship between these professions, but to state the
facts. Optometrists are trained and licensed to diagnose and treat disorders
and diseases of the eyes and visual system through non-surgical means,
including the use of prescription eye drops (and oral medications in
most states), as well as to detect the ocular manifestations of systemic
disease and refer patients to other health care specialists for eye
surgery and/or further medical evaluation. Optometrists perform the
majority of routine eye examinations in the United States.
Becoming an optometrist requires four years of pre-medical undergraduate
education and then an additional four years of optometry school. Optometry
school education consists of courses in geometric, physical and physiological
optics, ocular anatomy and physiology, general anatomy and physiology,
general and ocular pathology, general and ocular pharmacology, ocular
manifestations of systemic disease, binocular vision, pediatric vision,
geriatric vision, refraction, cosmetic and medical contact lens applications.
The final two of four years is spent seeing patients in eye clinics
and hospitals, including externships with eye surgeons and sub-specialists,
and conducting original ophthalmic research. Three sets of national
board examinations and individual state board examinations are required
for licensure, with mandatory continuing education requirements every
one to two years. Some doctors of optometry complete an additional one-year
residency, and a few complete multi-year specialty fellowships.
In my own practice, I routinely uncover previously undiagnosed diabetes
in the course of my ocular examination. I work closely with retinal,
glaucoma, corneal and neuro-ophthalmic sub-specialists, and non-ophthalmic
specialists who treat patients with diabetes, and I receive referrals
back from them because they know of my commitment to diabetes care and
education. I talk to dozens of colleagues who are doing the same. I
attend optometric educational conferences where diabetes care routinely
commands major attention.
The truth is, most optometrists do a fine job of detecting and appropriately
managing eye complications related to diabetes. They counsel their patients
diligently, and refer them to ophthalmologists when indicated. As with
any profession, some doctors, both optometrists and ophthalmologists,
will have more knowledge, experience, and compassion than others will.
No matter which type of eye doctor a diabetic patient sees, the most
important consideration is finding someone knowledgeable about and experienced
with diabetic eye disease.
5. Patients with diabetic retinopathy should not take
aspirin. The Early Treatment of Diabetic Retinopathy Study (ETDRS) clearly
demonstrated that aspirin therapy does not worsen pre-existing diabetic
retinopathy. If a patient is experiencing actively bleeding proliferative
retinopathy with vitreous hemorrhage, it may be prudent to delay aspirin
usage for a time, depending on her macrovascular status. The bottom
line: retinopathy is not a contraindication to ASA therapy.
6. The Amsler Grid test is an effective screening
tool for diabetic maculopathy. This subjective test relies on the patient’s
ability to perceive omission (scotoma), distortion (metamorphopsia),
waviness or color change of a uniform grid of perpendicularly oriented
lines. In a patient with clinically significant diabetic macular edema
or proliferative retinopathy, the two most significant causes of serious
vision loss in diabetes, by the time such irregularities are perceived
a great deal of retinal damage has already occurred, and the prognosis
is much poorer. Dilated, stereoscopic examination of the macula is the
only reliable way to detect these conditions in their earliest, most
treatable stages. Amsler grid testing is an important tool, however,
for self-detection of subretinal neovascularization (as in exudative
macular degeneration, pathological myopia and ocular histoplasmosis).
7. A measurement of intraocular pressure determines
whether or not I have glaucoma. Elevated intraocular pressure (IOP)
is now recognized as a risk factor for glaucoma, not as a necessary
or sufficient cause. Fifty percent of all patients with definitive glaucoma
will have normal IOP at some point of the day. In addition, at least
10% of all patients with glaucoma will never have an IOP reading above
20mm Hg (“normal tension glaucoma” or NTG). Diabetics are
more likely to develop NTG, possibly due to microvasculopathy of the
optic nerve and glycation of supportive collagen.
8. Type 2 patients rarely lose vision to diabetes.
Although it is true that a higher percentage of Type 1 patients experience
microvascular diabetes complications, including retinopathy, more Type
2 patients suffer significant vision loss than do Type 1 patients in
terms of absolute numbers. Part of the reason, of course, is because
Type 2 patients outnumber Type 1 patients by a factor of nine. In addition,
Type 2 patients are more likely to develop diabetic eye diseases other
than retinopathy (e.g. cataract, glaucoma and ischemic optic neuropathy
in particular) as a function of both age and glycemic status.
Lessons
from a Diabetic Eye Doctor: How to Avoid Blindness and Get Great Eye
More Info:
Dr. Paul Chous received his undergraduate education at Brown University
and the University of California at Irvine, where he was elected to
Phi Beta Kappa in 1985. He received his Masters Degree in 1986 and his
Doctorate of Optometry in 1991, both with highest honors from the University
of California at Berkeley. Dr. Chous was selected as the Outstanding
Graduating Optometrist in 1991. He has practiced in Renton, Kent, Auburn
and Tacoma, Washington for the last 12 years, emphasizing diabetic eye
disease and diabetes education. Dr. Chous has been a Type 1 diabetic
since 1968. He lives in Maple Valley, Washington with his wife and son.
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