Multifocal Electroretinogram Can Detect the Abnormal Retinal Change in Early Stage of type2 DM Patients without Apparent Diabetic Retinopathy

Purpose. To study retinal function defects in type 2 diabetic patients without clinically apparent retinopathy using a multifocal electroretinogram (mf-ERG). Methods. Seventy-six eyes of thirty-eight type 2 diabetes mellitus(DM) patients without clinically apparent retinopathy and sixty-four normal eyes of thirty-two healthy control (HC) participants were examined using mf-ERG. Results. Patients with type 2 DM without apparent diabetic retinopathy demonstrated an obvious implicit time delay of P1 in ring 1, ring 3, and ring 5 compared with healthy controls ( t = 5.184 , p ≤ 0.001 ; t = 8.077 , p ≤ 0.001 ; t = 2.000 , p = 0.047 , respectively). The implicit time (IT) in ring 4 of N1wave was significantly delayed in the DM group ( t = 2.327 , p = 0.021 ). Compared with the HC group, the implicit time of the P1 and N1 waves in the temporal retina zone was significantly prolonged ( t = 3.66 , p ≤ 0.001 ; t = 2.187 , p = 0.03 , respectively). And the amplitude of P1 in the temporal retina decreased in the DM group, which had a significantly statistical difference with the healthy controls ( t = − 6.963 , p ≤ 0.001 ). However, there were no differences in either the amplitude of the response or the implicit time of the nasal retina zone between DM and HC. The AUC of multiparameters of mf-ERG was higher in the diagnosis of DR patients. Conclusions. Patients with type 2 DM without clinically apparent retinopathy had a delayed implicit time of P1 wave in temporal regions of the postpole of the retina compared with HC subjects. It demonstrates that mf-ERG can detect the abnormal retinal change in the early stage of type2 DM patients without apparent diabetic retinopathy. Multiparameters of mf-ERG can improve the diagnostic efficacy of DR, and it may be a potential clinical biomarker for early diagnosis of DR.

Perceived Stability of a Scene Depending on the Gain of Motion Parallax

An observer moving in a natural environment is usually able to separate the constant changes of his retinal images in such a way that he perceives the environment and the changes of his observation point independently. The necessary and sufficient conditions to perceive a stable environment in spite of the retinal change produced by self-motion are, however, as yet unknown. We found that under certain conditions a scene that changes during observer motion can appear more stable than a rigid one. In our experiment a scene consisting of a number of LEDs distributed in a dark room was visible through a window. A mechanical device controlled by a head-tracker was used to move the LEDs during head motion to either reduce or enhance motion parallax by a predefined gain factor. The subjects rated the scene with respect to different attributes including apparent deformation and degree of motion perceived. They were also asked to adjust the parallax gain to the value of greatest apparent stability of the scene. Monocular as well as binocular trials were conducted and different fixation points were employed. The result was a general tendency in all conditions to perceive scene motion when the scene was in fact rigid and to perceive the greatest stability when the scene was distorted in such a way as to produce reduced motion parallax.