The First Results of Аssessing Changes in the Cornea Biomechanical Properties after Keratorefractive Surgery

Objective: to conduct a comparative analysis of the biomechanical consequences of keratorefractive surgery, depending on the laser treatment technique used on the corneal stroma in patients with moderate myopia.
Materials and Methods. The study included 150 patients (150 eyes) with moderate myopia, who were divided into three groups according to the type of keratorefractive surgery (KRO) performed: group 1 — 50 patients underwent Femto-LASIK; group 2 — 50 patients underwent CLEAR surgery with a 1.5 mm incision; group 3 — 50 patients underwent CLEAR surgery with a 3.0 mm incision. All patients underwent both standard and specialized ophthalmic examinations before surgery and at various follow-up time points (1 week, 1 month, and 3 months post-surgery). Particular emphasis was placed on assessing the biomechanical properties of the cornea using the Corvis ST device.
Results. The pre-operative assessment of corneal biomechanical properties revealed no statistically significant differences between the groups, with all parameters falling within the normal range. At the 3-month follow-up, the central corneal thickness (CCT) was found to be highest in group 2 (CLEAR with a 1.5 mm incision) and lowest in group 1 (Femto-LASIK) (p < 0.05). Similarly, the SP-A1 and ARTh parameters demonstrated the highest values in group 2 and the lowest in group 1 (p < 0.05). Furthermore, the IR parameter was found to be lowest in group 2 and highest in group 1 at both the 1-month and 3-month follow-up visits (p < 0.05).
Conclusion. The observed dynamics of changes collectively demonstrate remodelling of the corneal biomechanical profile in the post-operative period, regardless of whether FS-LASIK or CLEAR surgery was performed. However, patients who underwent CLEAR surgery — particularly those with a 1.5 mm incision — exhibited less pronounced corneal changes. These findings underscore the critical importance of thorough pre-operative planning, which should include assessment of the initial corneal thickness, calculation of the residual stromal bed, analysis of individual biomechanical parameters, and selection of the most appropriate surgical technique to minimize corneal structural damage.

1. Biswas S, El Kareh A, Qureshi M, Lee DMX, Sun CH, Lam JSH. The influence of the environment and lifestyle on myopia. J Physiol Anthropol. 2024;43(1):7. doi: 10.1186/s40101-024-00354-7.

2. Baird PN, Saw SM, Lanca C, Guggenheim JA, Smith Iii EL, Zhou X. Myopia. Nat Rev Dis Primers. 2020;6(1):99. doi: 10.1038/s41572-020-00231-4.

3. Wolffsohn JS, Whayeb Y, Logan NS, Weng R. International Myopia Institute Ambassador Group. IMI-Global Trends in Myopia Management Attitudes and Strategies in Clinical Practice-2022 Update. Invest Ophthalmol Vis Sci. 2023;64(6):6. doi: 10.1167/iovs.64.6.6.

4. Holden BA, Fricke TR, Wilson DA, Jong M, Naidoo KS, Sankaridurg P. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmol. 2016;123(5):1036–1042. doi: 10.1016/j.ophtha.2016.01.006.

5. Sankaridurg P, Tahhan N, Kandel H, Naduvilath T, Zou H, Frick KD. IMI Impact of Myopia. Investig. Ophthalmol. Vis. Sci. 2021;62:2. doi: 10.1167/iovs.62.5.2.

6. Chen W, Yang Z. Comparison of visual quality and optical zones after TransPRK, SMILE, and FS-LASIK myopia correction procedures. BMC Ophthalmol. 2025;25(1): 527. doi: 10.1186/s12886-025-04358-4.

7. Liu S, Zhou X, Zhao Y. Comparison of predictability in central corneal thickness reduction after SMILE and FS-LASIK for high myopia correction. Ophthalmol Ther. 2023;12(1):549–559.

8. Kanclerz P, Khoramnia R. Flap thickness and the risk of complications in mechanical microkeratome and femtosecond laser in situ keratomileusis: a literature review and statistical analysis. Diagnostics. 2021;11(9):1588.

9. Guo H, Hosseini-Moghaddam SM, Hodge W. Corneal biomechanical properties after SMILE versus FLEX, LASIK, LASEK, or PRK: a systematic review and metaanalysis. BMC Ophthalmol. 2019;19(1):167. doi: 10.1186/s12886-019-1165-3.

10. Bao F, LopesBT, ZhengX, JiY, Wang J, ElsheikhA. CornealBiomechanics LossesCaused by Refractive Surgery. Curr Eye Res. 2023;48(2):137–143. doi: 10.1080/02713683.2022.2103569.

11. Eliasy A, Chen KJ, Vinciguerra R, Lopes BT, Abass A, Vinciguerra P, Ambrósio R Jr, et al. Determination of Corneal Biomechanical Behavior in-vivo for Healthy Eyes Using CorVis ST Tonometry: Stress-Strain Index. Front Bioeng Biotechnol. 2019;7:105. doi: 10.3389/fbioe.2019.00105.

12. Gui Y, Wang S, He Y, Zhang S, Zhang Y. Progress of corneal morphological examination combined with biomechanical examination in preoperative screening for keratorefractive surgery. Indian J Ophthalmol. 2023;71(6):2369–2378. doi: 10.4103/ijo.IJO_1377_22.

13. Wu Y, Guo LL, Tian L, Xu ZQ, Li Q, Hu J, Huang YF, Wang LQ. Comparative analysis of the morphological and biomechanical properties of normal cornea and keratoconus at different stages. Int Ophthalmol. 2021;41(11):3699–3711. doi: 10.1007/s10792‑021‑01929‑4.

14. Lee H, Kang DSY, Ha BJ, Choi JY, Kim EK, Seo KY, Kim TI. Biomechanical Properties of the Cornea Using a Dynamic Scheimpflug Analyzer in Healthy Eyes. Yonsei Med J. 2018;59(9):1115–1122. doi: 10.3349/ymj.2018.59.9.1115.

15. Yang K, Xu L, Fan Q, Zhao D, Ren S. Repeatability and comparison of new Corvis ST parametersin normal and keratoconus eyes. Sci Rep. 2019;9:15379. doi: 10.1038/s41598-019-51502-4.

16. Azor JA, Vega F, Armengol J, Millan MS. Optical Assessment and Expected Visual Quality of Four Extended Range of Vision Intraocular Lenses. J Refract Surg. 2022;38(11):688–697. doi: 10.3928/1081597X-20220926-01.

17. Lee JK, Chuck RS, Park CY. Femtosecond laser refractive surgery: small‑incision lenticule extraction vs. femtosecond laser‑assisted LASIK. Curr Opin Ophthalmol. 2015;26(4):260–264. doi: 10.1097/ICU.0000000000000158.

18. Izquierdo L, Sossa D, Ben‑Shaul O, Henriquez MA. Corneal lenticule extraction assisted by a low‑energy femtosecond laser. J Cataract Refract Surg. 2020;46(9):1217–1221. doi: 10.1097/j.jcrs.0000000000000236.

19. Leccisotti A, Fields SV, De Bartolo G. Refractive Corneal Lenticule Extraction With the CLEAR Femtosecond Laser Application. Cornea. 2023;42(10):1247–1256. doi: 10.1097/ICO.0000000000003123.

20. Wang M, Zhang F, Copruz CC, Han L. First experience in small incision lenticule extraction with the femto LDV Z8 and lenticule evaluation using scanning electron microscopy. J Ophthalmol. 2020;2020:6751826.

21. Järvenpää JJ. Q‑value individualized CLEAR lenticule extraction preserves corneal asphericity and minimizes spherical aberration while maintaining optical zone predictability. Sci Rep. 2025;15(1):30470. doi: 10.1038/s41598‑025‑16271‑3.

22. Azhdarova LV, Shevchuk MA, Kostenev SV, Slonimsky AYu, Gromova EG, Uyanaeva AA, Murtazalieva PK. The first clinical experience of CLEAR refractive lenticular surgery through a 1.0 mm incision. Ophthalmosurgery. 2025;3:50. doi: 10.25276/02354160-2025-3-50-58.

23. Pajic B, Cvejic Z, Pajic-Eggspuehler B. Cataract surgery performed by high frequency LDV Z8 femtosecond laser: Safety, efficacy, and its physical properties. Sensors (Basel). 2017;17:1429. doi: 10.3390/s17061429.

24. Riau AK, Liu YC, Lwin NC, Ang HP, Tan NY, Yam GH. Comparative study of nJ- and μJ-energy level femtosecond lasers: evaluation of flap adhesion strength, stromal bed quality, and tissue responses. Invest Ophthalmol Vis Sci. 2014;55(5):3186–3194. doi: 10.1167/iovs.14-14434.

25. Rajabpour M, Kangari H, Pesudovs K. Refractive error and vision related quality of life. BMC Ophthalmol. 2024;24(1):83. doi: 10.1186/s12886-024-03350-8.

26. Малюгин БЭ, Солодкова ЕГ, Балалин СВ, Куликов ВС, Лобанов ЕВ. Оценка изменения биомеханических свойств роговицы при кератэктазиях. Современные технологии в офтальмологии. 2021;5(40):179–187. doi: 10.25276/2312-4911-2021-5179-187.

27. Wu Y, Huang Y, Wang SH, Wang GQ, Yu AM, Zhao SZ. Comparative study of objective visual quality between FS-LASIK and SMART in myopia. Int J Ophthalmol. 2022 Mar 18;15(3):502–509. doi: 10.18240/ijo.2022.03.20.

28. Ahmed HM, Salem NM, Al-Atabany W. Impact of post-refractive surgeries on corneal biomechanics — a review. J Clin Eng. 2021;46(4):177–188. doi: 10.1097/JCE.0000000000000482.

29. Kulikova IL, Pikusova SM, Avershina LA. Changes in the stress-strain state of the cornea after hyperopia correction using LASIK and FS-LASIK. Modern Problems of Science and Education. 2021;2:196. doi: 10.17513/spno.30658.

30. Dracheva TV. Morphofunctional and biomechanical changes in the cornea after excimer laser vision correction using the LASIK technique. Scientific review. Pedagogical sciences. 2019;4-4:27–30.

31. Boyko EV, Togo ES, Suetov AA, Kachanov AB, Litvin IB. Direct assessment of changes in biomechanical properties of the cornea after ReLExSMILE and FemtoLASIK surgeries. Annals of ophthalmology. 2023;139(3):41–48. doi: 10.17116/oftalma202313903141.

32. Бойко ЭВ, Того ЕС, Литвин ИБ, Качанов АБ. Оценка изменений биомеханических свойств роговицы после проведения операции FemtoLASIK. Современные технологии в офтальмологии. 2021;5(40):121–125. doi: 10.25276/2312‑4911‑2021‑5‑121‑125.

33. Chuprov AD, Kanyukova YuV, Trubnikov VA. The influence of keratorefractive surgeries CLEAR and FEMTO-LASIK on biomechanical parameters of the cornea in patients with myopia in dynamics. Modern problems of science and education. 2023;4:124. doi: 10.17513/spno.32886.