[Correlation between glaucomatous hemifield scotomas in white-on-white perimetry and blue-on-yellow perimetry using the oculus twinfield perimeter]

Abstract

Introduction: The "Twinfield Perimeter" can be used for white-on-white and blue-on-yellow perimetry. Since the normative database which is used fort the calculation of the visual field indices for both strategies is based on data from white-on-white perimetric evaluations of normal persons using the "Tübinger Automatikperimeter", the validity of this approach may be questioned. In the study presented here we compared the correlation of white-on-white (W/W) and blue-on-yellow (B/Y) visual fields in glaucoma patients with a hemifield scotoma.

Patients and methods: One eye each from 40 normal persons and from 40 glaucoma patients was included in the study. Both W/W-perimetry and B/Y-perimetry was performed using the "Twinfield Perimeter" (Oculus, Modell 56 900, Wetzlar, Germany). From the sensitivity values determined with the 30/2 strategy, we calculated the mean sensitivity (MS), mean deviation (MD) of the total field and of both hemifields (HMS bzw. HMD) separately. Normal values derived from the normal persons of the present study were compared with the normal values used by the Twinfield Perimeter. To determine the strength of the association of B/Y- and W/W-hemifield scotoma, we calculated the linear correlation coefficient (Pearson's R) between the HMD of B/Y und W/W-hemifields.

Results: MS of both glaucoma patients and normal persons were determined to be significantly higher for B/Y visual fields (14.17 +/- 4.15 and 20.97 +/- 3.56) when compared with W/W-visual fields (10.70 +/- 3.19 or 15.98 +/- 3.3). When normal values from the Twinfield Perimeter were applied, the MD for normal persons was calculated to be - 4.69 +/- 3.22 compared with 0 +/- 3.6 when the MD was calculated with the normal values from the study. For both normal values we confirm a strong correlation between HMD-values of W/W- and B/Y-visual fields.

Conclusions: Since the mean sensitivity of B/Y visual fields is higher than the mean sensitivity of W/W visual fields, calculations of the MD of B/Y visual fields of glaucoma patients should be based on normative databases which are derived from B/Y visual fields of normal persons.