PURPOSE
The study investigates the influence of changes in keratometric parameters after refractive surgery on the results of Maklakov tonometry.
MATERIAL AND METHODS
The study examined a total of 61 people (121 eyes). The patients were divided into a control group with no history of surgery (16 people, 31 eyes), a LASIK group (13 people, 26 eyes), a femtosecond-assisted LASIK (FS-LASIK) group (16 people, 32 eyes), and a photorefractive keratectomy (PRK) group (16 people, 32 eyes). The patients underwent standard examination, keratometry (Km), Maklakov tonometry with a 10 g weight, and elastotonometry with 5, 7.5, and 15 g weights.
RESULTS
In the LASIK group, the indentation diameter with 5 and 7.5 g weights correlated with Km in the central and near-paracentral zone (r=0.3—0.5). Tonometry with a 10 g weight did not correlate with anything. Tonometry with a 15 g weight inversely correlated with Km in the paracentral points (4 mm) of the strong meridian (r= –0.5 ... –0.7). In the FS-LASIK group, a significant inverse correlation with Km was observed only for the indentation diameter with a 10 g weight in the paracentral (3—4 mm) zone (r= –0.4 ... –0.5). In the PRK group, weak (r<0.4) correlations were found between Km and the indentation diameter of the 7.5 and 10 g weights for the central zone (1—2 mm). No significant correlations were found for 5 and 15 g weights.
In the control group, there were practically no correlations for 5 and 7.5 g weights. The indentation diameter of the 10 g weight evenly correlated with Km at all points (r= –0.38 ... –0.60), the indentation of the 15 g weight correlated mainly with the curvature of the horizontal meridian (r= –0.37 ... –0.49).
CONCLUSION
Tonometry readings with the 10 g weight are the most dependent on Km in different groups, and the readings with the 5 g weight are the least dependent. LASIK is characterized by the largest scatter of dependencies for weights of different masses, FS-LASIK — by the smallest. Tonometry readings with the 5 g weight correlated with Km only in the LASIK group, and this was the only direct correlation. Considering the inverse nature of most correlations, higher Km may be associated with an overestimation of tonometry results, and lower Km — with its underestimation.
