Comparison of Intraocular Pressure Measured by Non Contact Air Puff versus Goldmann Applanation Tono meters in Gas-Filled Vitrectomized Eyest
DIREK PAT IKULSILA, MD*, SRISUDA T A WEEMANKONGSAB, MD*, SUPOB NGAMTIPAKORN, BSc*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand. t Presented at the Mahidol Day Meeting, Faculty of Medicine, Chiang Mai University, September 24, 2002.
Objective : To compare intraocular pressure (lOP) measured by two different instruments, air puff tonometer (APT) versus Goldmann applanation tonometer (GAT), in gas-filled vitrectomized eyes.
Design : Three-month, prospective, comparative trial. Participants : Thirty-eight patients (38 eyes), who underwent a pars plana vitrectomy (PPV) with gas injection, were enrolled in the study. Intervention: The lOP was measured by an APT, followed by GAT within 10 minutes by two different, masked investigators. Main outcome measures : lOPs were measured by two methods and then were compared. =
Results : Overall, there was a high correlation between both measurements (r 0.908, p < 0.05). Using the paired t-test, lOPs measured by the APT (21.69 ± 9.28 mmHg) and GAT (22.84 ± 9.84) were not significantly different (p > 0.05). By a subgroup analysis of 17 eyes with lOP measured by a GAT of 21 mmHg or less, the APT readings (15.28 ± 4.81) and GAT readings (14.4 7 ± 3.89) were not significantly different (p > 0.05). Of 21 eyes, with lOP measured by a GAT of 22 mmHg or more, the APT readings (26.88 ± 8.81) were significantly lower than those obtained by the GAT (29.62 ± 7.69) (p < 0.05).
Conclusion : In gas-filled vitrectomized eyes, lOP measurements obtained by an APT corre lated well with those obtained by GAT, especially when the lOP was within normal range. However, in eyes with elevated lOP, the APT significantly underestimated the lOP measurement when compared to the gold standard, GAT.
Keywords : Intraocular Pressure, Goldmann Applanation Tonometer, Air Puff Tonometer, Non Contact Tonometer
