Toshie Hirai

Loss of stereopsis with optic chiasmal lesions and stereoscopic tests as a differential test.

OBJECTIVE To identify and characterize the loss of stereopsis observed in patients with lesions of the optic chiasm. STUDY DESIGN Cross-sectional study. PARTICIPANTS Forty-three patients who had good visual acuity with orthophoria and without strabismologic histories were divided into two groups. Group 1 consisted of 13 patients with lesions involving the optic chiasm (regardless of their visual field loss) diagnosed by magnetic resonance imaging findings. Group 2 (control group) consisted of 30 patients who had large absolute visual field defects as a result of other causes, including 11 intracranial disorders other than optic chiasmal lesions, 11 cases of open-angle glaucoma, and 8 patients with lesions of the retina. METHODS The stereoacuity and visual field in each case in group 1 (before and after surgery) and group 2 were assessed, and the results were compared. MAIN OUTCOME MEASURES Stereoacuity was assessed by the Titmus stereo test (normal value for circle, 6/9; 80 seconds of arc) and by Lang-stereotest (normal value for circle, 3/3; 350 seconds of arc). Visual field was evaluated by Goldmann and Humphrey perimetry (conventional perimetry), the starlight test (binocular visual field test), and scanning laser ophthalmoscopic microperimetry (microperimetry). RESULTS Before surgery, 11 of 13 cases (85%) in group 1 failed stereo tests, and after surgery, 5 of 13 cases (38%) in group 1 failed stereo tests. Before surgery, four patients who failed stereo tests showed no absolute scotoma by Humphrey or Goldmann analysis; after surgery, one patient who failed stereo tests showed no absolute scotoma by Humphrey or Goldmann analysis. However, starlight testing showed complete bitemporal hemianopsia only under binocular conditions, and microperimetry demonstrated a relative bitemporal hemianopsia at the fixating point. No patient failed in the Titmus circle test, but one patient in group 2 failed the Lang test (3%). The patients with chiasmal lesions significantly lost the ability of stereopsis compared with other diseases (group 1 [before or after surgery] vs. group 2, P < 0.001, Fishers exact test). Conventional perimetry was unable to measure scotomas within 3 degrees of the fixation point, which is the key area for acute foveal stereopsis, because of an attached observational mirror. CONCLUSIONS The difficulty with stereopsis in patients with lesions of the optic chiasm is most likely caused by the compression of the decussating optic nerve fibers resulting in the loss of an overlapping visual field at the fixation point. Stereo tests were demonstrated to be simple and effective adjunctive tests for suspected chiasmal compression.

Development of Stereoscopic Acuity: Longitudinal Study Using a Computer-based Random-dot Stereo Test

PurposeTo investigate the development of stereoscopic acuity (stereoacuity) in children longitudinally.MethodsSeven full-term normal infants whose age at the beginning of the study was between 12 and 23 weeks were studied. A computer-based random-dot test of stereoscopic vision (TV-Random Dot Stereo Test) was used to measure stereoacuity. The test was repeated at 2- to 3-month intervals until the children reached 2 years of age, and then every 6 to 12 months until they reached 5 years of age.ResultsAll of the infants were found to have a stereoacuity of 2480 seconds of arc (2480″) with this test by 26 weeks of age. The first reliable measurement of stereoacuity was obtained from a 16-week-old infant. Stereoacuity did not improve significantly between 6 and 12 months, but it improved rapidly after 12 months. All children had a stereoacuity of 100″ with the Titmus Stereo Tests at 5 years of age, but the best stereoacuity with the TV-Random Dot Stereo Test was 229″ at 28.9 months.ConclusionsThe development of stereoacuity studied longitudinally was similar to that obtained by cross-sectional studies. The TV-Random Dot Stereo Test is a useful program for measuring stereopsis in preverbal children. Jpn J Ophthalmol 2005;49:1–5

Interexaminer differences in the traction test of the superior oblique tendon.

PurposeThe traction test of the superior oblique tendon is used for the manual evaluation of the looseness or tightness of the tendon. Because of the subjective nature of this test, knowledge of other clinical findings may lead to a bias in its interpretation. We studied interexaminer differences in the results of the test to assess the reliability of this traction test.MethodsExaminer A examined all of the patients and collected all clinical findings, including the results of magnetic resonance imaging. Each of the nine noninformed examiners participated in one or more traction tests without prior information regarding the clinical findings of the patient. The traction tests were performed on 31 patients under general anesthesia. The examiners performed the traction test alternately with examiner A and evaluated the laxity and tightness in the tendon based on a nine-step scale (−4 to +4). The results were recorded in a masked manner, and later a comparison between the evaluation results of examiner A and those of the other examiners was made.ResultsExaminer A and the other examiners were in agreement within one grading step on 27 of the 31 (87.1%) traction tests.ConclusionsWe demonstrated that the interexaminer differences in the interpretations of the traction test were acceptable, and that after the noninformed examiners had performed the test several times, their interpretations became closer to those of examiner A. Jpn J Ophthalmol 2005;49:216–219© Japanese Ophthalmological Society 2005