Extrafoveal photostress recovery test in glaucoma and idiopathic central serous chorioretinopathy

Abstract

Background/aims: A photostress recovery test was designed to differentiate macular diseases from optic nerve disorders, but recently an abnormal recovery time was reported in glaucoma. The purpose of this study was to search for the difference in abnormality of the photostress recovery test between glaucoma and idiopathic central serous chorioretinopathy (ICSC).

Methods: This study involved 21 normal subjects, 14 patients, with ICSC and 10 patients with primary open angle glaucoma (POAG). A scanning laser ophthalmoscope (SLO) was used with microperimetry for bleaching the test point and measuring the recovery of sensitivity. Photostress recovery time (SLO-PSRT) could be measured at extrafoveal points outside and inside the affected area. The initial sensitivity change and the time constant of recovery after bleaching were calculated by fitting an exponential equation to the data.

Results: In normal subjects, neither the initial sensitivity change nor the time constant were correlated with the location of the test point. In 14 patients with ICSC, the initial sensitivity change in the detached area was significantly smaller than that in the unaffected area which was not significantly different from that in the age matched normal subjects. The time constant in the detached area was significantly longer than that in the unaffected area, which was not significantly different from that in the normal subjects. In 10 patients with POAG, the initial sensitivity change inside and outside the scotoma was not significantly different from that of age matched normal subjects. The time constant inside the scotoma was significantly longer than that outside the scotoma, which was not significantly different from that of the age matched normal subjects.

Conclusion: Both ICSC and POAG showed a prolonged time constant of recovery, but the initial sensitivity change was reduced only in ICSC. The difference in our results between ICSC and POAG may be caused by the difference of the retinal pathology. Further, the SLO-PSRT is very useful when the lesion is located outside the fovea.

Figure 1

(A) The image on the fundus monitor of a SLO during extrafoveal bleaching. The area with stripes was covered with a Wratten filter. A cross indicates a fixating target and "A" indicates a testing point. (B) The image of the fundus monitor during foveal bleaching. Four crosses indicate fixating targets and "A" indicates a testing point.

Figure 2

(A) Location of the testing points for 12 normal subjects. The recovery times were measured at the points, 7.5° temporally, nasally, above and below from the fovea, 15° temporally and at the fovea. (B) Location of the testing points in idiopathic central serous chorioretinopathy (ICSC) group. (C) Location of the testing points in primary open angle glaucoma (POAG) group.

Figure 3

The recovery times to test spots of five intensities at 7.5° temporal point in normal subjects.

Figure 4

The initial sensitivity change(A), the time constant (B), and the threshold for the red target (C) at six points in 12 normal subjects.

Figure 5

The initial sensitivity change (A) and the time constant (B) in normal control group, and outside and inside the lesion in ICSC group. The closed circles indicate individual datum points.

Figure 6

The initial sensitivity change (A) and the time constant (B) in normal control group, and outside and inside the lesion in POAG group. The closed circles indicate individual datum points.