Absolute Visual Field Defects Research Articles

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, Fisher’s exact test). Conventional perimetry was unable to measure scotomas within 3° 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.

Usefulness of Gaze Tracking During Perimetry in Glaucomatous Eyes

Purpose: To evaluate the usefulness of a new fixation monitoring system called gaze tracking in the perimetry of glaucomatous eyes. Subjects and Method: We studied the visual field of 106 eyes in 106 persons, comprising 74 eyes with open-angle glaucoma and 32 eyes with ocular hypertension. Perimetry was performed using a Humphrey Visual Field Analyzer 740/750 with a 30-2 full threshold program. We used two parameters for gaze tracking: the percentage of the time when the subject's eye deviated from the fixation target more than 3 degrees (G 3) and 6 degrees (G 6). These parameters were assessed in three groups: those with no visual field defect (group N), those with absolute visual field defect including the blind spot (group M 1), and others (group M 0). Result: The values of G 3 and G 6 were significantly correlated with the fixation loss in groups N and M 0 ( P < .01). These values were not significantly correlated with the fixation loss in group M 1 ( P > .10). When the fixation loss was less than 20%, G 3 and G 6 values were significantly higher in group M 1 than in groups N or M 0. Conclusion: Gaze tracking is a useful fixation monitoring system particularly in the presence absolute visual field defect including the blind spot.

Laser Treatment of Retinopathy of Prematurity-Reply

In Reply. —We thank Dr Schechter for his interest in our article. Laser photocoagulation applications were placed one-half burn width apart to minimize potential complications. Confluent treatment of the avascular area, as is recommended for cryotherapy, will likely induce an absolute visual field defect in the treated region. If laser scatter treatment is applied, it is less likely that an absolute defect will be present throughout the treated area, which may vascularize after resolution of extraretinal fibrovascular proliferation. Late-onset rhegmatogenous retinal detachment is a recognized complication following cryotherapy for retinopathy of prematurity. 1 It has been suggested that retinal breaks found at the junction between the treated and untreated part of the retina in those cases occur because the firmly attached treated retina is unable to stretch adequately as the eye grows. 1 Intolerable anteroposterior tractional forces may result in tearing of the retina at the junctional zone. We believe

Wavelength discrimination in blindsight.

In the circumscribed, long-standing, clinically absolute visual field defects of three patients with vascular lesions that involved the optic radiation and visual cortex, forced-choice discrimination between coloured stimuli was tested. Paired stimuli were matched for luminous efficiency on the basis of previous measurements of increment-threshold spectral sensitivity made in the same patients and at the same retinal positions. To different extents all patients could discriminate between narrowband wavelength stimuli. The results imply that despite the effects of retrograde degeneration on thalamic and retinal colour-processing channels, neurons which process wavelength information are still functional, although the information they transmit is not consciously perceived.

Assessment of Visual-Field Changes before and after Focal Photocoagulation for Clinically Significant Diabetic Macular Edema

Visual fields were compared before and after focal photocoagulation for eyes with nonproliferative diabetic retinopathy and clinically significant diabetic macular edema. A total of 8 eyes was tested before treatment and 6-8 weeks after treatment using static automated visual fields (Octopus). The visual-field indices, mean defect (MD) and corrected loss variance, were employed as measures of retinal sensitivity. Our results show that focal photocoagulation (CLV) generally depressed sensitivity (increased MD) in the treated central 10 degrees field, whereas in the untreated control region (10-30 degrees) sensitivity generally remained stable. However, the whole-field indices indicated that overall the fields remained stable following focal photocoagulation treatment. These results suggest that although focal treatment produces local absolute visual-field defects, the effects are small relative to the global indices.

THE ROLE OF PHOTOCOAGULATION IN THE MANAGEMENT OF RETINOSCHISIS.

<h3>Introduction</h3> Retinoschisis is the term used to describe a split in the sensory retina. In this condition a new cleavage plane develops within that part of the retina derived from the inner layer of the optic cup; whereas in the retinal detachment, fluid accumulates between those parts of the retina derived from the inner and outer layers of the optic cup, between the retinal receptors (rods and cones) and the pigment epithelium. Retinoschisis can occur at any level of the sensory retina, but most commonly the cleavage takes place at the outer plexiform layer, with the accumulation of a mucopolysaccharide-rich viscous fluid within the schisis cavity. As the schisis progresses, the neural elements of the retina are at first stretched and finally lysed producing absolute visual loss in the affected areas. Clinically an absolute visual field defect corresponds to the area of retinoschisis. The diagnosis of retinoschisis is best made