Abstract
Purpose :
The Continuous Loop Averaging Deconvolution (CLAD) technique is used to extract "per-stimulus" responses at stimulation rates that normally produce steady-state (SS) responses with conventional methods. This is accomplished by presenting specially designed narrow jitter stimulation sequences (Ozdamar et al., 2014, Toft-Nielsen et al., 2014). In this study, a new bideconvolution (BiCLAD) method employing two temporally jittered biorthogonal sequences to stimulate two visual fields and allow the extraction of independent responses from each hemifield was used.
Methods :
Transient (TR) and quasi-steady-state (QSS) pattern PERG-VEPs were recorded at two reversal rates (2.5, 12.5rps) from normal subjects under monocular and binocular conditions. Pattern stimuli were delivered on a rectangular field ( 28°x14°) made of 2 separate LED based displays. Stimuli were composed of 6 horizontal cycles (99% contrast). Subjects were asked to fixate along the center horizontal line on one of five fixation points. Display subunits were driven either synchronously (monofield) or asyncronously (bifield) with similar mean rates. Conventional TR and BiCLAD deconvolved PERG (N35, P50; N95) and VEP (P60; N75; P100; N135) components were analyzed using latency/amplitude measures.
Results :
Both reversal rates produced clearly distinquishable PERG and VEP waveforms with conventional components at all different gaze fixation and eye stimulation conditions. In both monocular and binocular conditions, nasal and temporal PERG responses showed small and consistent differences in amplitude and morphology. Nasal responses resembled a conventional PERG response, while temporal responses exhibited slightly bifurcated and smaller peaks. In the 12.5 rps VEP, the early positive peak (P60) was more prominent and showed binocular summation characteristics and the P100 component was of smaller amplitude. In bifield mode both PERG and VEP components showed lateralization with respect to eye fixation.
Conclusions :
Hemifield testing using BiCLAD reveals differences in temporal and nasal morphology and will help in exploring retinal topography and enhancing the diagnostic utility of the PERG in retinal disorders. Simultaneuous VEP testing will further clarify contributions of the visual pathway and cortical areas, helping in stroke and other disorders involving localized trauma to specific cortical regions.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.