AUTHOR=Chen Minfeng , Zhang Ronghan , Zhu Chengwei , Peng Lulu , Zhao Sijun , Mao Xinjie 

TITLE=Analysis of corneal surface shape following overnight orthokeratology with different optical zone diameters

JOURNAL=Frontiers in Medicine

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2024.1421361

DOI=10.3389/fmed.2024.1421361

ISSN=2296-858X

ABSTRACT=<sec><title>Purpose</title><p>This study analyzed the corneal surface shape following overnight orthokeratology with different optical zone diameters.</p></sec><sec><title>Methods</title><p>A total of 82 eyes belonging to 41 myopic children who completed 1 month of the orthokeratology (ortho-k) lens wear at the Eye Hospital of Wenzhou Medical University from January 2022 to January 2023 were retrospectively analyzed. According to the size of the base curve (BC) of ortho-k lens, patients were divided into BC 5.0 and BC 6.0 groups. The changes in decentration distance and corneal refraction of the two groups after the ortho-k lens wear were analyzed. Independent sample <italic>t</italic>-tests were used to compare these two outcome measures between the two groups.</p></sec><sec><title>Results</title><p>The decentration distance of BC 5.0 group (0.37 ± 0.19 mm) was significantly lower than that of BC 6.0 group (0.49 ± 0.25 mm, <italic>t</italic> = −2.330, <italic>p</italic> = 0.022). In the BC 5.0 group, the direction of decentration was superonasal in 3 cases, inferonasal in 2 cases, inferotemporal in 21 cases, and superotemporal in 6 cases. In the BC 6.0 group, the direction of decentration was superonasal in 2 cases, inferonasal in 2 cases, inferotemporal in 27 cases, and superotemporal in 19 cases. The optical zone area (8.19 ± 2.96 mm<sup>2</sup>) and reverse curve zone area (30.05 ± 6.74 mm<sup>2</sup>) in the BC 5.0 group were significantly lower than in the BC 6.0 group (10.42 ± 2.03 mm<sup>2</sup>, <italic>t</italic> = −4.043, <italic>p</italic> &lt; 0.001; 38.21 ± 4.77 mm<sup>2</sup>, <italic>t</italic> = −6.422, <italic>p</italic> &lt; 0.001). The change in the rate of refraction in the horizontal direction in BC 5.0 group were significant higher than in BC 6.0 group.</p></sec><sec><title>Conclusion</title><p>Base curve 5.0 mm ortho-k lens is better positioned than BC 6.0 mm lens. A small BC ortho-k forms a smaller optical zone and reverse curve area, which might get a greater aiameter of alignment curve to facilitate positioning better than the traditional BC lens. In addition, a small BC lens increases positive refraction in the peripheral area, resulting in a greater negative pressure than the traditional BC lens.</p></sec>