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To identify factors associated with a high and low risk of developing multiple sclerosis after an initial episode of optic neuritis.Three hundred eighty-eight patients who experienced acute optic neuritis between July 1, 1988, and June 30, 1991, were followed up prospectively for the development of multiple sclerosis. Consenting patients were reassessed after 10 to 13 years.The 10-year risk of multiple sclerosis was 38% (95% confidence interval, 33%-43%). Patients (160) who had 1 or more typical lesions on the baseline magnetic resonance imaging (MRI) scan of the brain had a 56% risk; those with no lesions (191) had a 22% risk (P.001, log rank test). Among the patients who had no lesions on MRI, male gender and optic disc swelling were associated with a lower risk of multiple sclerosis, as was the presence of the following atypical features for optic neuritis: no light perception vision; absence of pain; and ophthalmoscopic findings of severe optic disc edema, peripapillary hemorrhages, or retinal exudates.The 10-year risk of multiple sclerosis following an initial episode of acute optic neuritis is significantly higher if there is a single brain MRI lesion; higher numbers of lesions do not appreciably increase that risk. However, even when brain lesions are seen on MRI, more than 40% of the patients will not develop clinical multiple sclerosis after 10 years. In the absence of MRI lesions, certain demographic and clinical features seem to predict a very low likelihood of developing multiple sclerosis. This natural history information is a critical input for estimating a patient's 10-year multiple sclerosis risk and for weighing the benefit of initiating prophylactic treatment at the time of optic neuritis or other initial demyelinating events in the central nervous system.

Objective: Acquired nystagmus may cause oscillopsia and in some cases decreased visual acuity. Such symptoms may be debilitating. We evaluated the efficacy of retrobulbar botulinum neurotoxin A in the visual rehabilitation of patients with acquired symptomatic nystagmus. Patients: Adults with acquired nystagmus from multiple sclerosis or brain-stem hemorrhage were recruited for this treatment study. Eligible patients were unable to perform visual tasks that they had performed prior to the onset of the nystagmus. Design and Intervention: A prospective study evaluated the results of the retrobulbar injection of 25 to 30 U of botulinum neurotoxin A. Patients underwent testing of visual function, including eye movement recordings before and after initial injections. Patients were followed up for changes in their visual function for at least 6 months following the last injection. Results: Six patients (nine eyes) with acquired nystagmus were treated with a series of 17 injections of retrobulbar botulinum neurotoxin A. Each patient had subjective and objective improvement in distance visual acuity following the injection. A reduction in the amplitude of the nystagmus was seen following each of the injections, but the frequency of the nystagmus was generally unchanged. Visual improvement usually lasted no more than 8 weeks. However, improvement persisted for 6 months after injection in two patients with oculopalatal myoclonus. Conclusion: Botulinum neurotoxin A transiently improves the visual function of patients with acquired nystagmus. For patients with oculopalatal myoclonus the improvement seems to last longer, about 6 months in two patients.

In Reply. —We appreciate Dr Kellen's comments regarding our recent publication. He is indeed correct in that we meant to say "the subarachnoid space," since he correctly indicates that this is where the cerebrospinal fluid is contained. We thank him for drawing this to our attention.

In Reply. —We would like to address each of Dr Hayreh's concerns. In NAION, is the visual loss due to blockage of the axoplasmic flow? Dr Hayreh states, and we agree, that in papilledema visual dysfunction is secondary to ischemia. Because optic nerve sheath decompression (ONSD) has been demonstrated to reverse severe visual loss in pseudotumor cerebri, 1 we considered ONSD for other optic neuropathies in which ischemia may be involved. Dr Hayreh continues that "axoplasmic flow plays no role in the conduction of nerve impulses." While this statement is true in the strict neurophysiologic sense, alteration of axoplasmic flow has produced blockage of impulse conduction in several carefully studied experimental and human conditions. First, giant axonal swellings have been produced in rats by the administration of β-β 1 -iminodipropionitrile, a toxin that disrupts the cytoskeletal elements of axons. 2 In this model, iminodipropionitrile blocks slow axonal transport more than

In Reply. —We are grateful for the opportunity to respond to the interesting comments of Drs Mutlukan and Cullen. The modified decompression procedure with multiple linear openings in the dura and lyses of "adhesions" or "trabeculations" between the meninges and the optic nerve was described and illustrated in our series of patients undergoing this surgical procedure for chronic papilledema associated with pseudotumor cerebri. 1 We are aware that the subdural space is only a potential space and that normal optic nerves demonstrate "adhesions." As we indicated in our reply to Dr Kellen, we should have specified the subarachnoid space rather than the subdural space as the source of the cerebrospinal fluid. However, with breakage of these "adhesions," we have consistently observed drainage of additional cerebrospinal fluid from areas of presumed entrapment. The possibility of an empty sella syndrome explaining the biliteral improvement experienced by two of our patients is an

In Reply. —We appreciate Dr Wilson's comments regarding our article on optic nerve sheath decompression for progressive nonarteritic ischemic optic neuropathy (NAION). Our relatively large number of patients with progressive NAION reflects the clinical activity of the Wills Eye Hospital Neuro-Ophthalmology Service, Philadelphia, Pa, where we see over 4000 patients a year. The incidence of progressive visual loss in our population correlates well with the incidence reported by Boghen and Glaser. 1 We agree with Dr Wilson that conclusive evidence is lacking to support a completely ischemic pathogenesis for NAION and believe that the alternative hypothesis proposed by Borchert and Lessell 2 may have merit. However, we doubt that an inflammatory etiology for NAION has been overlooked, because the most complete histopathologic study of this entity did not demonstrate any vascular or neural inflammation. 3 We believe that the focal ischemic neuropathies of diabetes mellitus satisfy the criteria for another

Twenty-three patients with chronic papilledema associated with pseudotumor cerebri underwent "modified" optic nerve sheath decompression for treatment of visual acuity and visual field loss. Instead of removing a single, rectangular section of optic nerve meninges, the operation was modified by making at least three longitudinal incisions in the sheath and then lysing arachnoid adhesions with a tenotomy hook. Twenty-one of the 23 patients demonstrated improved visual function after the initial surgery for a mean (+/- SD) follow-up of 21.5 +/- 12.3 months (median, 25 months; range, three to 45 months) without reoperation or reinstitution or oral corticosteroid and diuretic therapies. The two patients failing to improve after the first surgical procedure initially had a single meningeal window created and subsequently improved following reoperation with the modified procedure. Twelve of 21 patients with bilateral visual loss had improved visual function bilaterally after unilateral surgery. Six of the 21 patients needed bilateral surgery, and the other three had minor visual field defects in the second eye not severe enough to warrant surgery. Preoperative optic disc pallor did not predict a poor postoperative result. Optic nerve surgery improved the visual function in six patients who had failed to recover vision after one or more lumbar-peritoneal shunts.

• Fifteen patients with hemifacial spasm were treated with botulinum A toxin injections. All patients experienced relief from spasm, with the effect lasting an average of 12.2 weeks. Complications were tearing in four patients, inability to close the involved eye in three patients, corneal exposure in one patient, and ectropion in one patient. All complications were transient and deemed minor by the patients.

In Reply. —Dr Baker is correct that iophendylate is not a water-soluble material. The nature of the contrast material, however, does not invalidate the clinical syndrome we have described. We did not intend our article to be a statistical evaluation of myelography but only intended to point out this relatively rare occurrence. Our objective is to prevent further investigation of patients who are seen with this unusual, but self-limiting complication of myelography. Speculation as to the cause of this problem is presented only as a speculation.

• Twenty-one patients with lesions compromising the optic tract were reviewed. The involvement of the optic tract may be diagnosed in the presence of highly incongruous hemianopia, an afferent pupillary defect, and characteristic atrophy of the optic discs. Behr's pupil, hemianopic pupillary reaction (Wernicke's sign), and associated major neurologic deficits were encountered rarely.

Goldmann perimetry was performed on patients with pseudopapilledema. The cases were subdivided into those with ophthalmoscopically visible hyaline bodies (HB), (group 1) and those without (group 2). In group 1, 37 of 52 eyes (71%) demonstrated field abnormalities, including enlargement of the blind spot (68%) and various nerve fiber bundle defects (70%); inferior nasal defects were the single most frequent defect. In group 2, ten of 47 eyes (21%) showed only enlarged blind spots and two fields were generally constricted. No nerve fiber generally constricted. No nerve fiber bundle defects were found in this group. It is noted that field defects related to other ocular or intracranial diseases may be found in patients with intrapapillary HBs.

• Twelve patients (17 eyes) with the acute retinal necrosis syndrome were analyzed with special reference to the development of an acute optic neuropathy. Six patients (9 eyes) without acute optic nerve involvement were treated with intravenous acyclovir sodium and/or vitreoretinal surgery (group 1). Six patients (8 eyes) fulfilling absolute and relative criteria for acute retinal necrosis optic neuropathy were treated with intravenous acyclovir as well as optic nerve sheath decompression, and, in addition, some of these patients also underwent vitreoretinal surgery. Despite more pronounced initial visual loss compared with group 1, six eyes in group 2 regained visual acuity of 20/400 or better. In contrast, only 2 of 9 eyes in group 1 maintained their entry level visual acuity, and the visual acuities of the remaining 7 eyes deteriorated to counting fingers or worse. Therefore, the acute optic neuropathy complicating the acute retinal necrosis syndrome appears to benefit from prompt recognition and surgical decompression of the intraorbital optic nerve meninges in conjunction with intravenous acyclovir.

• To clarify clinical features of pseudopapilledema, 142 cases (250 eyes) were analyzed regarding sex, age, race, bilaterality, acuity, refractive error, fundus characteristics, and coincident disease. Ninety-eight cases of identifiable hyaline bodies ([HB] group 1) were compared with 44 cases of pseudopapilledema without HB (group 2). The following results were notable: marked predominance of whites; one third in group 1 were unilateral, and 14% of all pseudopapilledema was unilateral; in only one eye did HB apparently account for diminished acuity; refractive error distribution paralleled that in the general population; anomalous vascular patterns occurred in 20% of group 1 and in 31% of group 2; pigment epithelial changes were found in 33% of group 1 and in 20% of group 2; and a statistically significant association was found with retinitis pigmentosa only. Analysis of field defects is the subject of a companion report.

We compared the results of ocular pneumoplethysmography in nine patients who had a temporal artery biopsy (TAB) diagnostic of giant-cell arteritis with results of ocular pneumoplethysmography in nine patients with normal TAB results and 112 patients with anterior ischemic optic neuropathy or central retinal artery occlusion assumed to be nonarteritic. The mean +/- SD ocular pulse amplitude with ocular pneumoplethysmography was 3.9 +/- 1.8 mm in the group with abnormal TAB results and 10.6 +/- 4.0 mm in the group with normal TAB results. Every patient with abnormal TAB results had an average calculated ocular blood flow less than 0.60 mL/min, while only one patient with normal TAB results fell in this range. The average calculated ocular blood flow had a sensitivity of 100% and a specificity of 93.4% in the diagnosis of giant-cell arteritis, with a diagnostic accuracy of 93.9%. These results rival the diagnostic accuracy of the erythrocyte sedimentation rate and TAB results.