AIM: To assess the gap between the peak of the base curve to the surface of the cornea, as well as examines the correlation between the thickness of the tear film and the fitting of the orthokeratology lens through optical coherence tomography(OCT), providing an intuitive and quantitative clinical evaluation method for the fitting of the orthokeratology lens.

METHODS: Myopia patients who fitted orthokeratology at our hospital from January to December 2023 were included. Examinations, including naked vision, slit lamp, non-contact intraocular pressure, ocular fundus, eye position, corneal diameter, corneal topography, tear film rupture time, optometry, etc., were performed on all patients before fitting. The trial lens parameter was selected according to the examination results, and fluorescein staining was performed to evaluate lens fitting state after patients adapted to wearing glasses. According to the performance of fluorescein staining, the inspected eyes are divided into three groups: lens loose group, lens fitting group, and lens tight group. In addition, the tear film thickness of three groups of subjects was measured by OCT, and the differences between the three groups of data were evaluated.

RESULTS: A total of 49 myopic patients(77 eyes)were included. The average sphere degree was -3.10±1.25 D, the average cylinder degree was -0.43(-0.75, 0)D, the average horizontal keratometry(HK)was 42.48±0.81 D, and vertical keratometry(VK)was 42.98(42.25, 43.50)D. There were 21 cases(34 eyes)in the lens fitting group, with 13 cases of bilateral eyes, 8 cases of one eye, 14 cases(22 eyes)in the lens loose group, with 8 cases of bilateral eyes, 6 cases of one eye, and 14 cases(21 eyes)in the lens tight group, with 7 cases of bilateral eyes, 7 cases of one eye. There was no statistical difference in the main basic data of the subjects in the three groups(all P>0.05). OCT showed that the tear film thickness of the lens fitting group, the lens loose group, and the lens tight group was 231.18(219.0, 243.0), 220.41(214.0, 224.3), and 249.00(241.5, 258.0)μm, respectively, and there was statistical significance in the thickness among the three groups(P<0.05).

CONCLUSION: OCT can serve as a safe and reliable method for measuring the tear film thickness, which can help evaluate the suitability of orthokeratology and provide a non-invasive, more intuitive, and quantitative evaluation method for the fitting and evaluation of orthokeratology.