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Accurate patient screening reduces risk that comes with pupillary dilation

Issue: March 1996

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BIRMINGHAM, Ala.—The risk of inducing acute angle-closure glaucoma when dilating a potentially occludable angle is less than 1% when easily applied patient screening criteria are used, according to a recent study.

These findings, in addition to legal trends that favor liberal use of dilation, may ease the minds of optometrists who are reluctant to do this for fear of provoking an angle-closure attack after mydriasis.

"It is clear that dilation is part of optometry," said John G. Classé, OD, JD, a professor here at the University of Alabama at Birmingham, School of Optometry. "Angle-closure is a risk, but it is not of sufficient magnitude to deter someone from using dilation as an ongoing procedure," he said. "It is fair to say that the trend in terms of judicial interpretation is moving towards the idea that a first-presenting patient should be given a dilated fundus examination to rule out the possibility of pathology."

Simple screening factors

The authors of a study published last December in the American Journal of Ophthalmology concluded that the risk of dilating an eye with a potentially occludable angle is less than 1% when three risk factors were assessed:

1. presence of shallow anterior chamber on penlight examination,
2. history of glaucoma, and
3. blindness in at least one eye.

The researchers studied 5,308 respondents to the Baltimore Eye Survey to measure the incidence of acute angle-closure glaucoma secondary to pupillary dilation and to identify screening methods for detecting angles that are at risk of occlusion. A total of 4,870 subjects had their pupils dilated upon screening examination and none developed acute angle-closure glaucoma.

Of the 1,770 subjects who were referred for definitive eye examinations, 38 were judged to have occludable angles on the basis of gonioscopy. Eleven of the 38 displayed a shallow anterior chamber by penlight examination.

However, patients who have shallow angles are still candidates for pupillary dilation, as the authors noted: "Classifying a subject as having a potentially occludable angle means that the eye should be dilated with caution, not that the angle will occlude after a single episode of dilation."

Jimmy D. Bartlett, OD, professor at the University of Alabama at Birmingham, School of Optometry, said the study results illustrate the benefits of careful patient screening prior to a dilated examination.

"I have been dilating pupils routinely since 1974 and can count on one hand the number of mydriatic-induced angle closures I have seen," he said. "One reason for that is we screen our patients and we do not put a mydriatic in without first questioning the patient. If you do a careful screening you will identify patients who are at risk for closure."

What is protocol?

The decision to dilate every patient, however, may still not be a simple one for the practitioner, said James V. Aquavella, MD, clinical professor of ophthalmology at the University of Rochester in New York. "Whether or not you dilate depends on the nature of the visit."

An example of a situation where a dilated examination is not necessary, Aquavella said, would involve the patient who has periodic and complete examinations, but while traveling away from home loses a pair of reading glasses and sees a different practitioner for a replacement pair. "It would not be indicated to dilate this patient," Aquavella said. "It is not good medicine and you would be overtreating the patient."

However, there are many indications for a dilated fundus examination, Aquavella said: "Recom- mendations concerning dilation depend on the patient's age, medical status, ocular status and, to a certain extent, race."

Normal patients, ages 20 to 45, with the absence of specific symptoms do not need a dilated fundus examination more often than every 5 years, he said. "If the patient has hypertension, diabetes, or is taking autoimmune drugs, they need to be dilated more frequently to examine the macula and periphery."

Predetermining factors for classifying patients as having a potentially occludable angle

1. Patients are usually hyperopic, in the +3 D to +5 D range.
2. Patients have narrow angles.
3. Patients may complain that on occasion their vision "goes out" on them for about 10 minutes.
4. Under slit-lamp examination, glaukomflecken are visible on the anterior lens capsule.

Source: Joseph F. Molinari, OD