Macular symmetry testing for glaucoma detection.

PURPOSE

To evaluate structural asymmetry in the macula using optical coherence tomography (OCT) in glaucomatous eyes with visual field defects localized to one hemifield.

METHODS

Complete examination, standard automated perimetry (SAP), and OCT imaging (512 A-scans) of the peripapillary retina and macula were performed. Exclusion criteria were visual acuity <20/40, diseases other than glaucoma, and SAP defects localized to both hemifields. Macular OCT images were obtained using four 5-mm radial scans centered on the foveola and passing obliquely through the macula (15 degrees superotemporally and inferotemporally). Macular measurements temporal to the fovea (T) were sub-divided into nasal (T1) and temporal (T2) segments. Macular symmetry testing (MST) was performed in T, T1, and T2 segments by comparing the mean macular thickness of the perimetrically abnormal and perimetrically normal hemi-zones (macular thickness in perimetrically normal hemi-zone/macular thickness in perimetrically abnormal hemi-zone x 100), and superior and inferior hemi-zones in normal subjects (macular thickness in superior hemi-zone/macular thickness in inferior hemi-zone x 100). MST measurements were considered to be abnormal if they exceeded the 95% limits of normal variability.

RESULTS

Forty eyes of 40 patients (20 normal, 20 glaucoma) were enrolled (mean age 60 +/- 19 years, range 21-89). All eyes with glaucoma had associated hemifield defect (average MD = -7.23 +/- 4.8 dB, range -0.9 to -15.4). In glaucomatous eyes, mean retinal thickness in T, T1, and T2 within the perimetrically abnormal hemi-zone (222 +/- 14 microm, 224+/- 17 microm, 221 +/-13 microm, respectively) was significantly less (P = 0.002, 0.008, 0.001, respectively) than the corresponding segments in the perimetrically normal hemi-zone (235 +/- 17 microm, 237 +/- 18 microm, 233 +/- 17 microm, respectively). Normal eyes showed no difference (P = 0.17, 0.20, 0.35) in T, T1, and T2 measurements within the superior hemi-zone (254 +/- 11, 249 +/- 14, 258 +/- 14) and inferior hemi-zone (252 +/- 11, 250 +/- 13, 255 +/- 13), respectively. MST values in glaucomatous eyes were outside 95% limits of normal variability in 17/20 (85%) T segments, 16 /20 (80%) T1 segments, and 16/20 (80%) T2 segments.

CONCLUSION

Localized macular thickness changes exist in glaucomatous eyes with regional visual field loss. The MST may represent a novel strategy for glaucoma diagnosis.