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ORIGINAL CONTRIBUTIONS

Visual Outcome in Eyes With Asymptomatic Optic Disc Edema

Almog, Yehoshua MD; Goldstein, Michaella MD

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Journal of Neuro-Ophthalmology: September 2003 - Volume 23 - Issue 3 - p 204-207
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Abstract

Patients with anterior ischemic optic neuropathy (AION) always manifest optic disc edema when presenting to the ophthalmologist with visual loss. In 1981, Hayreh (1). first described 4 visually asymptomatic patients in whom disc edema was diagnosed on a routine examination. Some of these patients, who had normal visual function, later developed typical symptomatic AION. Other patients have asymptomatic optic disc edema that resolves spontaneously. This phenomenon has been described mainly in diabetes mellitus (2) and has therefore been called “diabetic papillopathy.” There is much confusion as to whether diabetic papillopathy and AION are the same entities. In 1997, Gordon et al (3) described 2 patients who had AION in 1 eye and asymptomatic optic disc edema in the fellow eye that resolved spontaneously. Spontaneous resolution of asymptomatic optic disc edema has also been described in patients treated with amiodarone (4,5).

The conversion rate of asymptomatic optic disc edema to symptomatic AION has never been prospectively studied. It was the purpose of this study to determine this rate and to characterize the patients who undergo conversion.

METHODS

Included in the study are 23 patients who attended the neuro-ophthalmology unit in the Tel-Aviv Medical Center from November 1991 through December 2000 with the diagnosis of asymptomatic optic disc edema. Most patients were referred for disc edema as incidentally discovered on routine fundus examination performed for diabetes or hypertension. In most others, the asymptomatic disc edema was incidentally discovered in our clinic on follow-up after a diagnosis of AION in the fellow eye. One patient was followed because of a question of amiodarone-induced optic neuropathy.

The mean age of our cohort was 63 years (range 45–74 years). There were 16 men and 7 women. Diabetes mellitus was present in 19 (83%) patients, 4 of whom were being treated with insulin. Among the 19 patients with diabetes, 11 had no evidence of diabetic retinopathy. Among the eight patients who had diabetic retinopathy, it was always nonproliferative. Systemic hypertension was present in 11 (48%). Four patients (17%) were being treated with amiodarone for cardiac arrhythmia; 3 of them also had diabetes. Only 2 patients were free of atherosclerosis. History and findings suggesting old AION in the fellow eye were present in 10 (43%) patients. Bilateral asymptomatic disc edema was present in 2 patients. The cup-to-disc ratio exceeded 0.2 in only 1 patient.

All patients underwent a complete ophthalmological examination, including visual acuity, biomicroscopy, pupillary tests, color vision tests, fundoscopy, and visual field examination (Humphrey 30-2 or 24-2). Blood samples for glucose, urea, cholesterol, triglycerides, blood count, and erythrocyte sedimentation rate were drawn in all patients.

Fluorescein angiography, performed in all patients to distinguish congenital optic disc elevation from acquired edema, demonstrated abnormal staining of the involved disc in every case.

All patients had a corrected visual acuity of 20/40 or better in the eye with asymptomatic optic disc edema. Depression of visual acuity was always attributable to cataract or diabetic retinopathy. There was no relative afferent pupillary defect on the side with the disc edema. Color vision was always normal. In eyes with asymptomatic optic disc edema, there was no visual field defect other than an enlarged blind spot.

Six patients underwent computed tomography of the brain when papilledema was considered, and none had pertinent abnormalities. A temporal artery biopsy in 1 patient with an erythrocyte sedimentation rate of 70 mm/h was normal.

Patients were followed on a weekly basis for the first month, then on a monthly basis until 1 of 2 endpoints was reached: 1) complete resolution of the optic disc edema with preserved visual function, or 2) development of AION, defined by subjective visual loss and visual field defect with or without decreased visual acuity, color vision, or afferent pupillary defect.

RESULTS

Table 1 summarizes the demographic parameters, systemic medical features, current drug therapy, and clinical endpoints of eyes with asymptomatic disc edema.

TABLE 1
TABLE 1:
Clinical data in 23 patients with asymptomatic optic disc edema

In 9 (36%) eyes, disc edema progressed to overt AION with sudden and persistent loss of vision. In these eyes, the mean time lag between the identification of the asymptomatic disc edema and the development of AION was 16.8 weeks (range 2–80 weeks). If the 1 patient who developed AION after 80 weeks (Patient 16) is excluded, the mean time lag for development of AION was 9 weeks (range 2–18 weeks).

Optic disc edema resolved without visual loss in 16 (64%) of eyes. In these eyes, the mean time for resolution of the optic disc edema was 15.5 weeks (range 4–44 weeks).

Among 10 patients (43%), history and ocular findings were consistent with the diagnosis of AION in the fellow eye. In this group, 4 (40%) demonstrated progression to overt AION, and 6 (60%) demonstrated resolution of the edema without visual loss.

The conversion rate to AION in other subgroups was 6 (31%) of 19 patients with diabetes, 3(43%) of 7 patients with diabetic retinopathy, and 0 (0%) of 4 patients treated with amiodarone. Among 2 patients with binocular asymptomatic disc edema, 1 patient progressed to AION in both eyes, and the other patient had 1 eye resolve without visual loss and the fellow eye develop classic AION.

Among the 9 eyes that progressed to AION, the mean visual acuity was 0.63 log Mar (range 0.2–1.3). Among the 6 eyes who underwent threshold visual field testing after converting to AION, the mean of the mean deviation was −15.3 dB (range −8.1 to −27.7 dB).

DISCUSSION

Our study found that asymptomatic disc edema resolved without visual loss in 64% of eyes with a mean latency of 15.5 weeks (range 4–44 weeks). In 36% of eyes, optic disc edema progressed to AION with a mean latency of 16.8 weeks (range 2–80 weeks). Among those who progressed to AION, most had diabetes mellitus, but the rate of progression to AION was not dependent on the presence of diabetic retinopathy, nor did a history of AION in the fellow eye particularly predispose to the conversion to AION in the asymptomatic eye.

Our study is the first to prospectively follow a sufficient number of patients with asymptomatic disc edema to estimate the rate of developing AION in these patients, as well as the latency of conversion.

The optic disc edema in this group of patients may represent a state of disc ischemia not severe enough to cause loss of axonal function. AION is associated with systemic diseases such as hypertension, diabetes mellitus, and atherosclerotic cardiovascular and cerebrovascular disease (6–9). The fact that all but two of our patients had systemic diseases that are associated with atherosclerosis suggests that asymptomatic optic disc edema may be a preinfarctive state in these patients. Almost half of our patients had past AION in the fellow eye, suggesting that their asymptomatic disc edema may be considered an impending AION. Another argument to imply that asymptomatic disc edema in these patients is related to ischemia and AION was the small cup-to-disc ratio in all but one of them (10).

We were surprised at the high prevalence of diabetes (83%) in our group. It could be argued that the asymptomatic disc edema was incidentally discovered in patients with diabetes because they undergo regular fundus examinations, but we have not observed this entity as frequently in other groups of patients who undergo comparable periodic eye examinations, such as those with high myopia, previous retinal detachment, retinal artery or vein occlusion, age-related macular degeneration, or prior AION in one eye. In their case–control study, Jacobson et al (9) concluded that diabetes is a major risk factor for the development of nonarteritic AION. Moster (11) found as well that the vascular effects of diabetes contribute to nonarteritic AION. We therefore assume that the incidental finding of asymptomatic disc edema might be related, although not exclusively, to diabetes.

Diabetic papillopathy, first described in patients with juvenile-type insulin-dependent diabetes mellitus (12–15), is now recognized to occur in subjects with adult-onset non-insulin-dependent diabetes as well (2,16). In 1995, Regillo et al (2) found that all patients with diabetic papillopathy had at most only mild loss of vision, that their optic disc edema generally resolved after a few months without permanent severe visual loss, and that most had small cup-to-disc ratios. However, these authors excluded patients who developed AION, a fact that could artificially separate diabetic papillopathy from AION. We believe there is much similarity between our group of patients and those described in the past as having diabetic papillopathy. Perhaps such patients actually have an asymptomatic disc edema that has not evolved into full-blown AION.

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