Relationship between Maklakov tonometry and pneumatic applanation tonometry readings after refractive surgery

PURPOSE. This study examined the relationship between Maklakov tonometry readings obtained using weights of different masses and biomechanically corrected intraocular pressure (IOP) values measured by pneumatic applanation tonometry in patients after various types of keratorefractive surgery (LASIK, FS-LASIK, and PRK).

METHODS. The study included 61 patients (121 eyes): a control group (n=31) and three postoperative groups – LASIK (n=26), FS-LASIK (n=32), and PRK (n=32). All patients underwent Maklakov tonometry using 5-, 10-, and 15-g weights. Using the Ocular Response Analyzer (ORA), corneal-compensated IOP (IOPcc), Goldmann-correlated IOP (IOPg), corneal hysteresis (CH), corneal resistance factor (CRF), and the biomechanical stress coefficient (Kbs) were measured.

RESULTS. The strongest inverse correlations between Maklakov tonometry and IOPcc were observed in the PRK group (r=−0.80 and r=−0.91 for the 5- and 10-g weights, respectively), whereas in the LASIK group the maximum association was found with the 5-g weight (r=−0.85), weakening as the weight mass increased. In the FS-LASIK group, significant correlations were predominantly observed with the 10-g weight (r=−0.67). In the control group, the 10-g weight showed no correlation with any parameter, while the 5- and 15-g weights demonstrated moderate correlations with IOPcc, IOPg, CRF, and Kbs. Corneal hysteresis correlated significantly only with the 5-g weight in the PRK group (r=−0.491).

CONCLUSION. After LASIK and PRK, Maklakov tonometry using a 5-g weight compares the best with biomechanically corrected IOP values, whereas after FS-LASIK the 10-g weight appears to be preferable. These findings underscore the need for individualized selection of weight mass when performing Maklakov tonometry in patients with altered corneal biomechanics.

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