Abstract
Abstract: :
Purpose:To quantify characteristics of the optic nerve circulation in patients with unilateral nonarteritic anterior ischemic optic neuropathy (NAION) or optic neuritis (ON) and in healthy control subjects in order to assess the potential of laser Doppler blood speed measurements as a means of differentiating between patients with NAION or ON. Methods:A total of 33 consecutive patients with unilateral NAION, and 26 with unilateral ON, diagnosed at Massachusetts Eye & Ear Infirmary, along with 52 age-matched control subjects were studied. All patients and subjects underwent a full neuro-ophthalmologic evaluation. Laser Doppler measurements at two to five sites of the optic nerve head tissue in both eyes were obtained. Measurement sites were on the temporal and nasal sides of the nerve head in regions free of surface vessels. The mean capillary blood speed was deduced from the width of Doppler-broadened frequency spectra (DB). DB was compared between similar sites in affected and unaffected eyes of the patients, and between similar sites in the affected and unaffected eyes of the patients and in the eyes of the control subjects in a case-control analysis. Results:A polynomial regression fit best described the variation of DB with age in the control subjects. In NAION, there was a statistically significant decrease in DB at temporal sites of the nerve head in affected eyes compared to unaffected eyes (-16.9%, p=0.0001) and to control eyes (-16.2%, p=0.0001). In ON, there was also a statistically significant decrease in DB on the temporal side in affected eyes compared to unaffected eyes (-9.8%, p=0.0004) and to control eyes (-10.3%, p=0.0001). On the nasal side, however, only patients with NAION had significant decreases in DB in affected eyes compared to unaffected eyes (-10.5%, p=0.0005), and to control eyes (-10.0%, p=0.0001). The normal variation of temporal side DB with age was not present in affected eyes of NAION or ON patients. Significant differences in DB between affected eyes of NAION patients and ON patients on both the temporal side (p=0.010) and nasal side (p=0.012) were found. Decreases in DB were greater in NAION compared to ON. Conclusion:Local capillary blood speed characteristics differ in patients with NAION compared to patients with ON. Such measurements may help to differentiate these two most common non-glaucomatous optic neuropathies.
Keywords: 487 neuro-ophthalmology: optic nerve • 448 ischemia • 486 neuro-ophthalmology: diagnosis