Correlation between fractional clearance and optical outcomes of LASIK myopia correction

  • Milorad Milivojević Military Medical Academy, Clinic for Ophthalmology, Belgrade
  • Snežana Knežević Academy of Applied Studies Polytechnic, Department of medical Sciences, Belgrade, Serbia https://orcid.org/0000-0001-9137-2122
  • Bojan Radojičić Higher School of Health and Sanitation of Vocational Studies "Visan", Belgrade
  • Rada Zečević Special Eye Hospital "Belgrade Ophthalmology Center", Belgrade
  • Ivan Marjanović University of Belgrade, Faculty of Medicine, Belgrade; University Clinical Centre of Serbia, Belgrade
Keywords: fractional clearance, optical zone, LASIK, higher-order optical aberrations

Abstract


Excimer laser pulses using the LASIK method ablate the corneal stroma, achieving its remodeling to desired optical characteristics. Besides correcting ametropia, it is desirable to minimize the induction of higher-order optical aberrations (HOA), as they affect the occurrence of glare and halos in night vision conditions. Fractional clearance (FC) represents the ratio of the treated optical zone (OZ) diameter to the pupil diameter in scotopic lighting conditions. The aim of this study is to examine the relationship between the enlargement of the treated OZ diameter and the increase in FC index on postoperative HOA levels. A prospective study included 37 subjects (74 eyes) with myopia treated with the LASIK method. The eye with higher residual stromal bed value was treated with an OZ diameter of 7.0 mm, and the other eye of the same patient with an OZ diameter of 6.5 mm. After 6 months, objective evaluation of optical outcomes was performed using an Analyzer device. The mean FC value in the group of eyes treated with OZ 6.5 mm is 2.138 (SD 0.30), and in the group treated with OZ 7.0 mm is 2.325 (SD 0.37), with a statistically highly significant difference (t=3.64; p<0.001). A smaller induction of all measured HOA was found when a wider OZ of 7.0 mm was treated, with the statistically most significant reduction observed in spherical aberration induction. The increase in FC index is proportional to the enlargement of the treated OZ diameter. With an increase in FC value, the level of all HOA decreases after the LASIK procedure, with the most significant reduction observed in spherical aberration induction. Enlargement of OZ to 7.0 mm, when corneal structural characteristics allow it, improves postoperative optical outcomes.

Author Biography

Snežana Knežević, Academy of Applied Studies Polytechnic, Department of medical Sciences, Belgrade, Serbia

Lecturer at the Academy of Applied Studies Polytechnic and Head of the Department of Medical Sciences, Belgrade (2022). Lecturer at the University of Kragujevac, Faculty of Hotel Management and Tourism in Vrnjačka Banja. PhD in Management and Business and Medicine. Master Manager in the Health Care System. Accredited educator of health workers for domestic violence (UNFPA Serbia) (2019). Member of the Scientific Board of the Serbian Medical Society (Section of General Medicine) (2019). Member of the Editorial Board of the Journal of General Medicine (2020). Author of over 170 scientific research papers and presentations at international and domestic conferences. European recipient of the Montegut Global Scholars Programme award for the improvement of primary health care (2019). Member of EGPRN, EPCCS, WONCA SIGFV, and SIG LM. National coordinator of IMOCAFV and EURODATA projects (2020). Reviewer of papers for scientific journals, national and european and world conferences of general and family medicine physicians (WONCA).

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Published
2026/07/04
Issue
Vol. 31 No. 101 (2026)
Section
Original Scientific Paper