Background and objective: It has been suggested that the clinically detectable changes of the blue-on-yellow (B/Y) visual field and retinal nerve fiber layer (RNFL) may precede standard white-on-white (W/W) visual field defects in the progression of glaucoma. The aim of this study was to test the relationship between the results of B/Y visual fields and semiquantitative RNFL evaluation in corresponding areas and to determine how the B/Y visual fields and RNFL scores label the normal W/W perimetry hemifields in patients with glaucoma and ocular hypertension.
Design: A cohort study.
Participants and methods: Monochromatic RNFL photographs of 32 normal subjects and 29 patients with ocular hypertension and different stages of glaucoma were assessed in a masked fashion. The B/Y and W/W visual fields (program 30-2) were examined with a Humphrey perimeter. The results of both visual fields were adjusted for the patients' age and lens transmission index measured with a lens fluorometer.
Main outcome measure: Mean deviation (MD) of visual field and semiquantitative score of RNFL loss were measured.
Results: The total and hemifield MD values of B/Y and W/W visual field showed a statistically significant correlation with diffuse and overall score of RNFL loss in corresponding areas. The hemifield MD values of B/Y perimetry obtained from "normal" W/W hemifields of patients with early glaucoma were well correlated (r = -0.56) with respective RNFL loss scores found to be abnormal in 84% of hemispheres. The difference between the hemifield MD values of B/Y perimetry obtained from normal W/WAN hemifields of patients with ocular hypertension and patients with early glaucoma was not statistically significant (analysis of variance). The respective B/Y hemifield data of normal subjects were statistically significantly different from the data of patients with ocular hypertension and early glaucoma.
Conclusions: The hemifield MD values of B/Y perimetry correlate well with semiquantitative scores of RNFL loss obtained from the corresponding hemisphere. The B/Y perimetry as well as RNFL assessment may show glaucomatous defects in a hemifield found to be normal on W/W perimetry. In subjects with ocular hypertension, the functional damage detected by B/Y perimetry may, in some cases, precede RNFL defects on conversion to glaucoma.