Abstract
Purpose: :
This study evaluates correlation of visual field, divided into superior and inferior hemifields, to respective inferior and superior quadrant retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT).
Methods: :
A retrospective, cross–sectional study was conducted using peripapillary RNFL thickness measured by OCT within three months of visual field testing. An average decibel value for each visual hemifield (VHF) was calculated for hemifield retinal sensitivity. Correlation of superior VHF to inferior quadrant RNFL thickness and inferior VHF to superior quadrant RNFL thickness was analyzed.
Results: :
Four hundred and seventy–four eyes of 312 patients (143 glaucoma, 194 glaucoma suspect, 137 normal) were evaluated. Superior quadrant RNFL thickness was 79.6 ± 28.4 µm in glaucoma, 107.6 ± 25.0 µm in glaucoma suspect and 119.3 ± 22.6 µm in normal patients, respectively (P<0.0001). Inferior quadrant RNFL thickness was 79.1 ± 31.6 µm in glaucoma, 111.2 ± 24.2 µm in glaucoma suspect and 124.7 ± 19.7 µm in normal patients, respectively (P<0.0001). Average decibel value for superior VHF was 19.9 ± 8.4 dB in glaucoma, 26.2 ± 3.4 dB in glaucoma suspect and 28.2 ± 1.8 dB in normal patients, respectively (P<0.0001). Average decibel value for inferior VHF was 21.8 ± 7.3 dB in glaucoma, 26.9 ± 2.6 dB in glaucoma suspect and 28.6 ± 1.4 dB in normal patients, respectively (P<0.0001). In glaucoma patients, superior and inferior VHF sensitivity correlated significantly to respective inferior and superior quadrant RNFL thickness (r=0.70 and r=0.64, respectively). In comparison, the correlation of superior and inferior VHF sensitivity to respective quadrant RNFL thickness was weak in glaucoma suspect (r=0.28 and r= 0.30, respectively) and normal patients (r=0.20 and r=0.38, respectively).
Conclusions: :
Reduced superior and inferior VHF sensitivity corresponds to thinning of respective peripapillary RNFL in glaucoma patients. However, correlation of VHF sensitivity to respective RNFL thickness was weak in glaucoma suspect and normal patients. As disease progression occurs, decreasing retinal sensitivity correlates to structural damage of RNFL. However, VHF sensitivity with early structural damage in glaucoma suspects is less defined. Preperimetric structural testing is important for early detection of disease.
Keywords: imaging/image analysis: clinical • visual fields • nerve fiber layer