Tonometry after Laser in Situ Keratomileusis Treatment: A Preliminary Study in Thai Patients
Ngamkae Ruangvaravate, MD*, Atiporn Thuangtong, MD*, Panida Kosrirukvongs, MD*, Pinnita Prabhasawat, MD*, Wipawee Booranapong, MD*, Sabong Srivannaboon, MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Siriraj Hospital, Mahidol University
Objective : To evaluate the change in intraocular pressure (IOP) measurement by Goldmann applanation
tonometer after Laser in Situ Keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the
correlation between the changes of IOP reading and the reduction of central corneal thickness (CCT) after
LASIK in Thai patients.
Study
Design : Prospective correlational study.
Materials and Methods : LASIK was performed on 65 eyes of 33 patients for correction of myopia and myopic
astigmatism. IOP was measured by Goldmann applanation tonometer before and 3 months after LASIK. The
correlation between the change in IOP reading and the change in central corneal thickness were evaluated.
Results : IOP reading was significantly reduced by mean of 2.9 + 2.5 mmHg (p = 0.0001). The authors used
Pearson analysis to study the correlation between the change in IOP and the reduction of CCT. In subgroup
analysis the patients were divided by degree of myopia: group 1, myopia less than -3 diopters (D) (n = 14);
group 2, myopia -3 to -6 D (n = 31); group 3, myopia greater than -6 D (n = 20)). The result showed more
correlation in higher myopia group (Pearson; r = 0.158 in group 3, r = -0.098 in group 2 and r = -0.102 in
group 1).
Conclusion : Goldmann applanation tonometry underestimates the IOP in thin cornea. Variability in CCT is
a potent confounder of this tonometry technique. Therefore, it has important implications for considering
CCT measurement incorporated with Goldmann applanation tonometry for glaucoma diagnosis especially
in myopic patients who undergo LASIK surgery.
Keywords : Goldmann applanation tonometry, Intraocular pressure, Laser in Situ Keratomileusis, Central corneal thickness
