Actualización de los procedimientos de evaluación funcional visual mediante técnicas electrofisiológicas y su aplicación al diagnóstico clínico

Resumen

Objective: The objective of this doctoral thesis is to improve the applicability of visual electrophysiological techniques to clinical practice, through optimizing stimulus parameters for recordings of pattern electroretinography (pattern Electroretinogram, pERG) and Electrooculography (EOG). Likewise, it is intended to evaluate the diagnostic precision of multifocal Visual Evoked Potential (mfVEP) in patients with glaucoma and to find its best diagnostic indicator. Methods: To achieve the objectives, three different studies have been carried out. In the first pERG study, carried out in healthy volunteers, the signals were recorded through corneal electrodes, while stimuli of different contrast (99%, 60%), shape (checkerboard or grid), color (red-green, blue-yellow and white-black) and spatial frequency (0.08, 0.12, 0.17, 0.35 cycles per degree, [cpd]) were applied. The amplitude (V) of the P50 and N95 waves of the pERG was analyzed. In the second study, also on healthy volunteers, disposable surface electrodes were placed in the proximity of both eyes. White/black contrast stimuli were applied in the form of a horizontal, vertical and rotational scroll bar, at different frequencies (0.2/0.3/1/2/3/10 Hz) under light and dark adaptation. The stimuli were applied from a monitor using visual software of our own development. The amplitude (mV) of the generated waves was analyzed. In the third study, a systematic review with meta-analysis of quantitative studies published until June 1st 2020, was performed to evaluate the diagnostic performance of mfVEP in patients with glaucoma. The methodological quality of the included articles was assessed. We have performed the analysis for publication bias and the test for heterogeneity. We have calculated the sensitivity, specificity and diagnostic odds ratio (DOR). The area under the curve (AUC) was calculated using the summary of receiver operating characteristics (sROC). Results: In the first study, we did not find significant differences in the amplitudes of P50 and N95 waves registered before stimuli with spatial frequencies of 0.08 to 0.35 cpd. The checkerboard and grid stimulus responses did not show statistically significant differences. The white-black stimuli elicited significantly higher amplitudes of the P50 and N95 waves than the chromatic stimuli (red-green and blue-yellow), but the results obtained in response to chromatic stimuli did not show significant differences. Likewise, it was shown that stimuli with higher contrast can cause higher amplitudes of P50 and N95 waves in the pERG test. In the second study, the amplitudes of the EOG signals were higher for the light stimuli with a temporal frequency of 0.3 Hz. The amplitudes of the EOG signals caused by horizontal and vertical stimuli were significantly higher than those caused by rotational stimuli. Likewise, the amplitude of the EOG responses is statistically significantly greater in vertical movements (0.278 ± 0.014 mV) than horizontal (0.211 ± 0.012 mV) (p <0.05, t-test). Finally, the amplitudes of the EOG responses are greater under photopic than scotopic conditions. In the third study, 6 studies with 241 individuals were included according to the inclusion and exclusion criteria. The area under the sROC curve was 0.98. There was no evidence of publication bias, or threshold effect. The pooled sensitivity and pooled specificity of the mfVEP amplitude for the detection of visual field defects in all studies were 0.93 and 0.89, respectively. The positive and negative likelihood ratio of mfVEP amplitude were 6.56 and 0.08, respectively. Conclusions: Regarding the pERG test as a direct indicator of ganglion cell functionality, we propose to use the stimuli consisting of checkers or grids, with 99% white-black contrast at a spatial frequency between 0.08-0.35 cpd. Regarding EOG, the frequency for linear stimulation should be adjusted to 0.3 Hz for a better functional evaluation of eye movements. Vertical displacement stimuli are better than horizontal or rotational stimuli. The amplitude of mfVEP has shown good diagnostic accuracy in predicting visual field defects, Interocular mfVEP amplitude analysis may be a good diagnostic indicator for visual field study.