Light with a short wavelength damages tissues such as the retina because of its high energy. Sunglasses and yellow intraocular lenses were able to reduce this damage by filtering out high-energy light in the visible spectrum. However, since these devices have a constant filtering, they may have undesirable effects on visual function in mesopic or scotopic environments, although they are beneficial in high light.
To determine the reliability and agreement of different optical devices in terms of keratometry and pachymetry measurements in cross-linked (CXL) keratoconic eyes. Material and Methods: Thirty-eight CXL-treated keratoconic eyes were evaluated. Three repeated measurements were performed with Topcon KR-1 autorefractokeratometry, Sirius topography, Nidek AL-scan optical biometry and RTVue anterior segment optical coherence tomography (AS-OCT). The devices were compared in terms of pachymetry and keratometric values. Limits of agreement (LoA) between the devices were detected using Bland-Altman analysis. Intra-examiner reliability was obtained using the intraclass correlation coefficient (ICC). Results: While the mean central corneal thickness (CCT) and minimum corneal thickness (MCT) measured in AS-OCT were 456.37±41.52 μm and 431.89±43.37 μm, respectively, these values were 432.40±48.97 μm and 415.67±47.69 μm in topography (p<0.001). The 95% LoA between the devices were -21.7 to 69.7 μm for CCT and -17.7 to 50.1 μm for MCT. Intra-examiner reliability was excellent for both devices in relation to the CCT and MCT measurements (ICC>0.97). When devices were compared in terms of the keratometric values and corneal astigmatism measurements, there was a significant difference among devices except between autorefractokeratometry and optical biometry (p<0.05; for all). The lowest LoA among the devices was found to be 3.3 D for steep keratometry and 2.9 D for flat keratometry and 2.3 D for corneal astigmatism. Intra-examiner reliability was excellent in all three devices in terms of the keratometric measurements (ICC>0.99). Conclusion: Pachymetry and keratometry can be performed independently in each device with excellent reliability in CXL-treated keratoconic eyes. However, we consider that measurements made with different devices cannot be used interchangeably in these eyes.
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