Ultra-High Resolution Optical Aberrometry in Patients with Keratoconus: A Cross-Sectional Study

Abstract

Introduction: This study performs optical aberration assessment in patients using a novel ultra-high-resolution device. The objective of this study is to analyze optical aberrations, especially the very high order wavefront (more than 10th order of Zernike coefficients), and compare between keratoconus and healthy patients. Methods: In this cross-sectional study, we analyzed 43 eyes from 25 healthy patients and 43 eyes from 27 patients with keratoconus using corneal tomography and a very high-resolution (8.55 lm) aberrometer prototype (T-eyede) outfitted with a sensor originally developed for use in the field of astrophysics. Corneal aberration values were assessed using an optical model built with Zemax optical software, while ocular aberrations were assessed using T-eyede. In addition, image-processing analysis was performed of the wavefront phase, creating a highpass filter map. Results: We found lower values for ocular aberrations than corneal aberrations in both groups (p \ 0.001). Specifically, we found a reduction in primary astigmatism (0.145 lm) and primary coma (0.017 lm). Also, the keratoconus group showed significantly higher wavefront aberration values compared with controls (p \ 0.001). An analysis of the highpass filter map revealed 2 contrasting results: one smooth or clear, while the other presented a banding pattern. Almost all in the control group (95%) showed the first pattern, while 77% of the keratoconus group showed a banding pattern on the filtered map (chi-squared test, p \ 0.001). Conclusion: This device provides reliable, precise measurements of ocular aberrations that correlate well with corneal aberrations. Furthermore, the extraordinary high-resolution measurements revealed unprecedented micro changes in the wavefront phase of patients with keratoconus that varied with disease stage. These findings could lead to new screening or follow-up methods.

Clinical applicability of the WaveFront Phase Imaging Sensor in the Keratoconus Disease

“…This specific map has been presented for the first time in the work of Bonaque et al in a small sample with healthy eyes where each eye has different “ocular structures” (the details revealed), but there is no specific pattern 19 . However, in the subsequent study, using the initial prototype of this device to compare the aberrometry between KC and healthy eyes, we qualitatively found a characteristic pattern in most of the maps corresponding to keratoconic eyes such as dark-light alternating bands, concretely in 76.74% of this sample, meanwhile in the rest might not be detectable due to the early stage of the disease or the great decentration of the cone concerning the pupil center 20 . These bands are detectable due to the effect that they cause on the ocular phase, as they have never been seen before using the wavefront measuring technique because no other sensor had sufficient resolution to uncover them.…”

“…Regarding the quantitative analysis of the high-pass filter map, we calculated the RMS and PV of a section to reach other parameters that can help in the KC detection, obtaining for both metrics results statistically different between the control and the keratoconic group as we presented in the previous study with the RMS of astigmatism, coma, and HOA 20 . For further studies, we will consider the sample size, because the sample presented was small and unequal between disease stages, so we cannot compare the marked suspect cases with the controls or compare severe stages (III and IV) with the mid-stages (I and II) where we have more sample.…”

“…The device presented in this document is the t·eyede aberrometer, which methodology has been previously described in other works 17,19,20 . This aberrometer can obtain the ocular phase using the WaveFront Phase Imaging sensor (Wooptix S.L., La Laguna, Tenerife, Spain), whose main advantage over other phase sensors is its lateral resolution of 8.6 µm.…”

Ocular high‐order aberrations in children and adolescents

“…If we reason the hypothesis that the origin of these high frequencies could be anatomical, then it should be noted that the observed patterns present substantial inter-individual differences, which would be difficult to explain if they originated only in the retina, since the structure of the retina in healthy individuals does not present such fundamental anatomical differences. Moreover, there would be no reason for eyes with keratoconus to exhibit differences with respect to healthy eyes, as shown by Velarde-Rodriguez et al 3 Consequently, we question why these patterns differ among individuals and yet remain unchanged between different measurements. Furthermore, if the authors' hypothesis were correct, then these phenomena would not be unique to our study, as the illumination of Hartmann-Shack-based systems is identical to that used in our study.…”

“…Although the confirmation did not come from a completely independent group, the results have recently been replicated in patients with keratoconus within a hospital setting, with principal investigators unrelated to our initial study. 3 Notably, each eye again showed its own high-frequency imprint on the wavefront phase, also with substantial inter-subject differences.…”