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María Iglesias, Andrea Laiseca, Ricardo Pedro Casaroli-Marano, Bachar Kudsieh, Jeroni Nadal, Rafael I Barraquer; New experimental applanation tonometer for myopic patients after laser refractive surgery.. Invest. Ophthalmol. Vis. Sci. 2018;59(9):1387. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Controversy exists regarding Goldmann tonometer (GT) for measuring intraocular pressure (IOP) in myopic patients after laser assisted in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). In order to reduce this inaccurate measurement, we designed a new experimental GT model with an apex convexly shaped (CT). This study tested the hypothesis that IOP in this subgroup of patients can be more precisely measured with this new device.
Two different radios (r) for the convexed apex of the CT were created: CT1 (r= 12.17 mm) and CT2 (r= 13.42 mm). We present a prospective, double-blind, comparative study between GT with CT1 and CT2. One hundred and two eyes from 102 myopic patients who underwent surgery with LASIK (L) (n=73) or PRK (P) (n=29) were evaluated. IOP, spherical equivalent (EE), simulated keratometry (simk) and central corneal thickness (CCT) (Pentacam), Ocular Response Analizer (ORA), were obtained before and after surgery. Moreover, the ablation depth and the percentage of ablated tissue (PTA) were also analysed. Given IOP measured in pre-surgery with GT as gold standard, we used Bland-Altman analysis to compare GT pre-surgery IOP (GTpre) with post-surgery IOP measured with GT, CT1 and CT2 (GTpost, CT1post and CT2post respectively).
Considering together L and P patients, Bland-Altman analysis showed poor agreement between GTpre and GTpost (mean differences: -3.56 mmHg, p<0.001; limits of agreement: -8.10 – 0.96). However, a much better agreement is observed between GTpre and CT1post (mean differences: 0.32 mmHg, p=0.187; limits of agreement: -4.24 – 4.89) and CT2post (mean differences: 0.91 mmHg, p<0,001; limits of agreement: -3.85 – 5.67). Regarding subgroups L and P, mean differences present the lowest values between GTpre and CT1post, -0.19 and 1.62 respectively for LASIK and PRK. In accordance, limits of agreement for CT1post are narrower than for CT2post and GTpost. Differences between CT1post and GTpre present some bias that appear to be related to simK values (p<0,001).
Our new experimental tonometer appears to be more precise for measuring IOP comparing to GT in myopic refractive surgery patients.CT1 proved better accuracy than GT in the LASIK subgroup. Thus, we can conclude that we have developed a new version of applanation tonometer that could be used in post-surgery LASIK patients with a much accurate result than the gold standard.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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