Changes in Intraocular Pressure After Laser in situ Keratomileusis

Abstract

PURPOSE: To evaluate changes in intraocular pressure (IOP) measurements by Goldmann applanation tonometry after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the accuracy of Goldmann applanation tonometry measurements after LASIK in these eyes. METHODS: LASIK was performed on 166 eyes of 93 patients for correction of myopia and myopic astigmatism. Intraocular pressure was measured by Goldmann applanation tonometry at the central and temporal parts of the cornea before and at 1, 3, 6, and 12 months after LASIK. The amount of change in IOP was computed and its relation to different variables was evaluated by regression analysis. RESULTS: Intraocular pressure measured at the center of the cornea was reduced by a mean of 3.69 ± 1.63 mmHg after LASIK Multiple regression analysis showed that the decrease in IOP was related to the preoperative IOP and the change in central corneal thickness after LASHC Measurements of IOP at the temporal part of the cornea were also reduced by a mean of 2.39 ± 1.71 mmHg. There was wide variability in the amount of difference between the temporal and central measurements after LASHi (temporal measurements were higher than central by 0 to +4 mmHg). CONCLUSION: LASIK for myopia produced underestimation of IOP measured by Goldmann applanation tonometry at the central part of the cornea by a mean of 3.69 ?1.63 mmHg. The decrease of IOP was related to preoperative IOP and the change in central corneal thickness after LASHi. Temporal Goldmann applanation tonometry measurements, although decreased after LASHi, were less reliable. [J Refract Surg 2001;17:420-427]

Photorefractive surgery with excimer laser and its impact on the diagnosis and follow-up of glaucoma. A review

“…Therefore, it is almost impossible to measure the IOP in a non-treated corneal area. Indeed, the differences between postoperative central and peripheral IOP measurements found by Park et al, [18] who used ablation zones 5.30 to 6.80 mm, and by Rashad & Bahnassy, [35] who mentioned an optical zone between 5.00 to 6.00 mm (both studies performed some years later than the study by Schipper et al) were less noticeable. This might possibly be related to the change of the optical zones that occurred in the period of time between the studies [17,18,35].…”

“…Schipper and co-authors in 1995 reported that there was a decrease of 2 to 3 mmHg in the value found with applanation tonometry in the central area of the cornea, after myopic ablation with PRK, but that this decrease was not found when taking the pressure measurement in the temporal periphery of the cornea [17]. Similarly, in 2001 Park et al [18] and also Rashad & Bahnassy [35] found less underestimation of the IOP when measured in the nasal peripheral cornea than in the central area. Therefore, the possibility of measuring the IOP in the periphery with an applanation tonometer, although technically challenging, seemed to be a plausible partial solution in these patients.…”

“…This is a critical factor in ablative corneal refractive surgery, which, along with other biomechanical changes induced by the procedure, affects the measurement of the IOP after the procedure. The underestimation of IOP after photorefractive surgery using Goldmann applanation tonometry, has been documented in many studies [17,[18][19][20]23,24,[27][28][29]31,32,[35][36][37][38].…”

“…Many formulas have been designed in order to calculate the real IOP based on postoperative IOP measurements, some of which are shown in Table 2. In 2016 De Bernardo et al, after testing several of these formulas in a group of 121 eyes of patients who underwent PRK, concluded that the best results were obtained by applying the formulas of Rashad, Chihara, Rosa and Duch [25,28,[35][36][37]. However, the first two require knowledge of the intraocular pressure measured before refractive surgery, which is rarely available.…”

“…Secondarily, it alters the precision of the IOP measurement, especially with applanation tonometers. Goldman tonometry has been widely shown to underestimate IOP after corneal photorefractive surgery [17,19,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. This underestimation of IOP may at some point delay the diagnosis of de novo glaucoma in patients with a history of refractive surgery [39][40][41][42][43][44].…”