The electroretinogram (ERG) is composed of slow (i.e., a-, b-waves) and fast (i.e., oscillatory potentials: OPs) components. OPs have been shown to be preferably affected in some diseases (such as diabetic retinopathy), while the a- and b-waves remain relatively intact. The purpose of this study was to determine the contribution of OPs to the building of the ERG and to examine whether a signal mostly composed of OPs could also exist. DWT analyses were performed on photopic ERGs (flash intensities: −2.23 to 2.64 log cd·s·m−2 in 21 steps) obtained from normal subjects (n = 40) and patients (n = 21) affected with a retinopathy. In controls, the %OP value (i.e., OPs energy/ERG energy) is stimulus- and amplitude-independent (range: 56.6–61.6%; CV = 6.3%). In contrast, the %OPs measured from the ERGs of our patients varied significantly more (range: 35.4%–89.2%; p < 0.05) depending on the pathology, some presenting with ERGs that are almost solely composed of OPs. In conclusion, patients may present with a wide range of %OP values. Findings herein also support the hypothesis that, in certain conditions, the photopic ERG can be mostly composed of high-frequency components.
Purpose: To investigate whether adding accelerated under-flap corneal cross-linking to hyperopic laser in situ keratomileusis (LASIK-ufCXL) affects postoperative stability and regression, visual and refractive outcomes, and subjective quality of vision. Methods: This prospective comparative contralateral eye study included 51 patients with hyperopia (102 eyes) who received LASIK-ufCXL in the eye with highest defocus equivalent (DEQ) or randomized when DEQ equal, with the contralateral control eye receiving LASIK alone. After excimer ablation, 0.25% riboflavin was instilled on the stromal bed for 3 minutes. The flap was repositioned, followed by a total irradiation dose of 3.24 J ultraviolet A (UV-A) light administered to the corneal surface, using 18 mW/cm 2 UV-A for 3 minutes. Postoperative hyperopic regression (stability) was the primary outcome measure, defined by the difference in spherical equivalent (SEQ) at 1 week and 24 months postoperatively. Secondary measures reported uncorrected distance visual acuity, corrected distance visual acuity, cylinder vector analysis, subjective quality of vision, subjective night vision disturbances, and corneal haze. Results: At 24 months, the SEQ stability ( P = .4273) and the magnitude of hyperopic regression ( P = .5613) did not significantly differ between groups, with a small trend showing hyperopic regression of 0.50 diopters or greater being less frequent in LASIK-ufCXL eyes. There were no significant differences in accuracy, efficacy, and safety ( P > .05), with a small trend of more residual refractive astigmatism in the LASIK-ufCXL group ( P = .3216, Cohen's d : −0.29). Subjective quality of vision trended inferior in LASIK-ufCXL eyes ( P = .2237, Cohen's d : −0.25), with a greater haze grading ( P = .0466, Cohen's d : 0.41). Conclusions: Postoperative regression and stability were statistically equivalent between hyperopic LASIK vs LASIK-ufCXL, with identical safety. There were small clinical trends of lower efficacy, accuracy, and subjective quality of vision in LASIK-ufCXL eyes. [ J Refract Surg . 2022;38(12):770–779.]
Purpose PRDD, such as Retinitis Pigmentosa, are accompanied with a gradual reduction of ERG signal to non‐measurable amplitudes. We compared alternative means of quantifying normal and pathological ERGs. Methods Photopic ERGs (DTL electrode, background 30 cd.m‐2; flash stimuli: ‐2.62 to 0.64 log cd.sec.m‐2 in 17 steps of ~ ‐0.2 log‐unit) were recorded from 85 normal subjects and 55 patients with PRDD. In a subset of 6 normal subjects, focal ERGs (fERGs) were obtained with the use of a eye patch to restrict the stimulus centrally and at 20o or 40o nasally. ERG descriptors, obtained with Direct Wavelet Transform D(WT) of the ERGs, were compared to the traditional amplitude measurements. Results In normal, the ERG amplitude gradually decreased from 131.42±31.27µV (Vmax) to 0.71±0.12 µV (dimmest flash used) in two distinct pseudo‐asymptotical steps of ‐15.2±2.0µV.s (step 1) and ‐0.42±0.1µV.s per decrement respectively (9 steps each). Pathological ERGs as well as normal focal ERGs could always be fitted to this model. Furthermore, while the traditional measurements frequently failed to quantify residual ERGs, including the normal fERGs, the DWT was always able to extract quantifiable and comparable information from the residual response, thus permitting a more favourable prognosis. Conclusion Analysis of the ERG response in the time and frequency domain (such as DWT) allows for a more precise quantification of the ERG signal especially when it reaches residual amplitudes such as that observed in end‐stage PRDD. Our results suggest that modeling ERG attenuation with the DWT improves the staging and prognosis of patients affected with severe PRDD. Supported by FFB (USA).
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