Comparing IOP Measurements in the Iraqi Population: Goldmann Applanation Tonometer vs. Topcon CT-80 Air Puff Tonometer

Accurate measurement of intraocular pressure (IOP) is crucial for diagnosing and managing glaucoma, a sight-threatening condition. This study aimed to compare IOP measurements obtained using Goldmann applanation tonometry (GAT) and Topcon CT-80 air puff tonometer (NCT) in Iraqi patients with varying IOP levels. A total of 98 patients (196 eyes) were included, spanning ages 5 to 80 years, with both genders represented. IOP was measured using both devices, and differences between measurements were analyzed. NCT readings, averaged from three measurements, were taken before GAT to avoid bias. To prevent significant intraocular pressure (IOP) reduction, contact with the applanation probe during GAT was limited to under 5 seconds. Subjects were categorized by age, gender, and IOP range. The mean IOP values obtained by GAT and NCT were 20.56 mmHg and 21.34 mmHg, respectively, with NCT yielding slightly higher readings. Younger age groups demonstrated significant differences between GAT and NCT measurements. Gender-based comparisons showed no significant differences in IOP readings. When stratified by IOP range, NCT overestimated IOP in low and normal ranges but produced similar measurements to GAT in high IOP ranges. Bland-Altman analysis revealed a broad range of agreement between the two devices. The correlation coefficient between GAT and NCT measurements was moderate. In conclusion, the Topcon CT-80 NCT provides easy and comfortable IOP measurement, but it tends to overestimate IOP in low and normal ranges while performing comparably in high IOP ranges. The study recommends caution in interchanging the two modalities due to their wide range of agreement limits.