Abstract
Purpose: :
To assess the sensitivity of ocular coherence tomography (OCT), patients with field defects confirmed on both conventional perimetry and multifocal visual evoked potentials (mfVEP) were studied.
Methods: :
Twenty patients with glaucomatous defects in at least one eye, as determined by an abnormal disc and abnormal Humphrey 24–2 visual fields (HVF), underwent OCT3 (RNFL), mfVEP and 24–2 HVF tests. The average 24–2 MD of the more affected eye was –8.3+/–6.9 dB. 20 control subjects had 24–2 HVF and OCT3. mfVEPs were obtained using the VERIS system (EDI), and three channels of recording. Monocular and interocular plots were analyzed with custom software.[1,2] For the mfVEP and 24–2 HVF (total deviation plot), a hemifield was defined as abnormal if 2 or more contiguous points had p<0.01, or 3 or more contiguous points had p<0.05 with at least one of these points with p<0.01.[3] For the HVF, only one point could be on the rim. The OCT was considered abnormal if one of the 5 sectors within a hemifield (sectors at 3 and 9 o'clock were excluded) was at < 1% or two sectors at < 5%. A criterion of one sector at <5%, marginally increased sensitivity, but markedly decreased specificity.
Results: :
Overall, 49% (mfVEP), 58% (HVF) and 59% (OCT) of the 80 hemifields were abnormal. For the 32 hemifields in which the mfVEP and HVF were both abnormal, the OCT was abnormal in all but 1 (96.9%). For the 27 hemifields with normal mfVEP and HVF, the OCT was abnormal in 9 (33.3%). And, for the 21 hemifields in which the mfVEP and HVF disagreed, the OCT was abnormal in 10 (47.6%). Only 1 of the 80 hemifields (1.3%) of the controls was abnormal on OCT.
Conclusions: :
OCT showed excellent sensitivity in detecting abnormal hemifields confirmed on the two functional tests. Further, OCT was abnormal in 33% of the hemifields in which both functional tests were normal. Given the low false positive rate in the control group, this suggests that OCT might be more sensitive than the functional tests in detecting damage. 1. Hood & Zhang (2000); 2. Hood & Greenstein (2003); 3. Chauhan et al (1998).
Keywords: nerve fiber layer • visual fields • electrophysiology: clinical