Paul Chous, M.A., O.D. Doctor of Optometry
Type 1 diabetic since 1968
The
undeniable standard of care for ocular examination of patients with
diabetes includes dilation of the pupils to facilitate optimal examination
of the retina and other ocular structures. Current ADA, ophthalmologic
and optometric guidelines recommend that all Type 1 patients receive
dilated eye examination within 3-5 years after diagnosis and each year
thereafter, and that all Type 2 patients be dilated upon diagnosis and
each subsequent year. Upon diagnosis of retinopathy in particular, the
frequency of subsequent dilated examinations may be greater, depending
upon the degree of severity.
Nonetheless, recent CDC analysis demonstrates that as many as 40%
of diagnosed diabetics do not receive annual dilated eye exams. A 2000
paper appearing in the Journal of the American Medical Association suggested
that annual dilated examination of many “low risk” diabetics
could not be justified based on cost/benefit analysis, and recommended
a laxer protocol, a position which the ADA panel of ophthalmic experts
has rejected in its most recent position statement. Given this backdrop,
it is useful to consider some of the key issues surrounding pupillary
dilation in general, and for persons with diabetes in particular.
The typical pupil is 3-4mm in diameter in normal room illumination,
whereas a dilated pupil is 7-8mm. This difference yields a three to
seven times greater area through which to examine the internal eye;
this means that the entire retina can be visualized through a dilated
pupil with relative ease, while examination of the entire retina is
very difficult, at best, through undilated pupils. Perhaps more important
is the fact that dilated pupils allow the examiner to obtain three-dimensional,
stereoscopic views of the retina and optic nerve, something critical
in the detection and management of both diabetic macular edema and glaucoma.
Pupillary dilation of diabetic patients is especially important for
detection and appropriate treatment of all diabetic eye disease, save
extraocular muscle palsy associated with diabetic cranial neuropathy.
The case for detection of retinopathy, retinal vascular occlusive disease
and optic nerve disease (both glaucoma and ischemic optic neuropathy)
is obvious. For both diabetic keratopathy (corneal disease) and cataract,
a dilated pupil provides greater anatomic access (in the case of the
crystalline lens and cataract) and an ideal visual background for viewing
certain types of cataract and many corneal abnormalities (i.e. the optically
“dark” pupil improves the visibility of abnormalities within
the transparent ocular media).
Moreover, many patients with diabetes have smaller than average pupils
(due to both normal aging and sympathetic pupillary autonomic neuropathy),
a factor that makes dilated examination all the more obligatory. It
must also be noted that diabetics are no less susceptible to many “non-diabetic”
eye diseases than the general population (e.g. age-related macular degeneration
and retinal break/detachment), that much eye pathology is age-related,
and that a majority of diabetic patients are over the age of 60 years.
For all these reasons, routine dilated examination of all patients is
indicated, but most especially for those with diabetes.
Patients frequently voice concern about the after-effects of pupillary
dilation, which include blurred vision (especially for farsighted persons),
light sensitivity, and diminished depth perception. Instillation of
eye drops typically stings (including, paradoxically, topical anesthetics),
and some patients are, of course, quite phobic about anything near their
eyes. Occasionally, patients experience hypersensitivity and, very rarely,
true allergic reactions. Many of these concerns can be allayed with
good patient education and preparation, and through good technique coupled
with optimal selection of pharmacologic agents.
Dilating drops may be broadly classified as “sympathomimetic”
(e.g. phenylepherine, cocaine, and hydroxyamphetamine) or “parasympatholytic”
(e.g. tropicamide and atropine). The former drugs stimulate the iris
dilator muscles, while the latter block action of the iris sphincter
muscle - as well as the ciliary muscle responsible for near focus (accommodation).
A common strategy is to employ both for maximal pupillary dilation (for
example, tropicamide is frequently administered with phenylepherine).
For detection of eye disease, dilation (mydriasis) is required, but
not loss of accommodation (cycloplegia).
The duration of action and degree of cycloplegia may be controlled
by manipulating drug selection and concentration. I have had particularly
good results with a combination agent called Paramyd (hydroxyamphetamine,
an indirect acting sympathomimetic, in combination with a mere 0.25%
short-acting parasympatholytic, tropicamide) in tandem with the commonly
used sympathomimetic, 2.5% phenylepherine; this duo results in relatively
fast onset, ample dilation of most (but not all) pupils, and minimal
cycloplegia. From personal and clinical experience, I have noted that
phenylepherine (especially at a 10% concentration) raises blood glucose
levels and may precipitate tachycardia, effects that may be minimized
by occluding patients’ punctal openings (thereby limiting nasopharyngeal
absorption via the tear ducts).
It is incumbent upon eye care providers to warn patients, prior to
examination and prior to drop instillation, about the effects of pupillary
dilation. Patients should be encouraged to bring dark glasses for photophobia,
a driver, or ideally, both. Most visually bothersome effects of routine
dilation dissipate within two hours, and patients should be discouraged
from driving until they feel safe to do so. A new pharmacologic agent
that shortens anticholinergic recovery from topical ocular agents is
also available (dipiprazole, trade named RevEyes). Provision of disposable
dark glasses and thorough patient education emphasizing the highly beneficial
risk/benefit ratio of pupillary dilation goes a long way toward turning
anxious patients into enthusiastic allies in the dilation process.
Vijan S, Hofer TP, Hayward RA: Cost-utility analysis of screening
intervals for diabetic retinopathy in patients with type 2 diabetes
mellitus. JAMA 283:889–896, 2000
Diabetes Care 26:S99-S102, 2003
About the Author
Dr. Paul Chous is the recent author of a critically acclaimed book
for patients and health care providers on diabetes and the eye, Diabetic
Eye Disease: Lessons From A Diabetic Eye Doctor – How To Avoid
Blindness and Get Great Eye Care (Fairwood Press). He may be reached
via his web site at http://www.diabeticeyes.com.
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.
Book Description
Diabetes affects every part of the eye, not just the retina. Presenting
critical information about seven different kinds of diabetic eye disease
as well as important steps all diabetics must take to preserve vision,
Dr. Chous clearly and comprehensively guides you through the fundamentals
of good diabetes management and great eye care. Written by an eye doctor,
diabetes educator and patient advocate, this book is dedicated to helping
you or someone you love avoid blindness and other complications by taking
charge of your diabetes
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