Scanning laser polarimetry with variable corneal compensation in the area of apparently normal hemifield in eyes with normal-tension glaucoma.

PURPOSE

To evaluate the retinal nerve fiber layer (RNFL) in the retinal segments without visual field loss in eyes with normal-tension glaucoma (NTG) that have localized visual field defects.

DESIGN

Prospective interventional case series.

PARTICIPANTS

Fifty-six Asian glaucoma patients with localized visual field defects confined to 1 hemifield and 43 normal control participants.

METHODS

A complete ophthalmic examination, the 24-2 full-threshold test on the Humphrey Field Analyzer (HFA; Carl Zeiss Meditec, Dublin, CA), and scanning laser polarimetry with variable corneal compensation (SLP-VCC; GDx-VCC, Carl Zeiss Meditec) were performed in each participant.

MAIN OUTCOME MEASURES

We compared RNFL thickness parameters on SLP-VCC printouts and severity scores based on the SLP-VCC deviation map algorithm in retinal segments with corresponding visual field defects with those in segments without visual field defects and with those in matched segments of age-matched normal controls. Linear regression analyses were performed between the RNFL thickness parameters and the severity scores in both segments with corresponding visual field defects and those without visual field defects and HFA indices (mean deviation, corrected pattern standard deviation) in these NTG eyes.

RESULTS

Seven of 56 eyes with NTG showed abnormal RNFL thickness parameters (P<0.05) in the quadrants without visual field defects, whereas no eye showed abnormal RNFL thickness parameters (P<0.05) in the matched quadrant of the control group. The mean RNFL thickness parameter in the quadrants without visual field defects in the NTG eyes was 62.41+/-7.71, which was significantly lower than in the matched quadrants of the control group (74.57+/-9.21; P<0.001) but was significantly higher than in the quadrants with corresponding visual field defects in NTG eyes (48.01+/-9.45; P<0.001). The severity score in the matched quadrants of control eyes was 0.53+/-3.20, whereas the severity score of quadrants without visual field defects of the NTG eyes was 13.52+/-35.40 (P<0.001).

CONCLUSIONS

Perimetrically normal hemifields of NTG eyes showed significantly lower RNFL thickness parameters than the corresponding retinal regions of healthy eyes, as measured by SLP-VCC. Scanning laser polarimetry with variable corneal compensation may have potential as an ancillary diagnostic tool in the evaluation of the corresponding RNFL without visual field defects in NTG eyes with localized visual field defects.