Abstract
Purpose: :
To evaluate the accuracy of intraocular pressure (IOP) measurements with Goldmann slit–lamp mounted applanation tonometry compared to Perkins hand–held applanation tonometry, taking central corneal thickness (CCT) into account.
Methods: :
A prospective study was done using patients selected randomly from our glaucoma clinic. The only inclusion criterion was that the patient was seen in the glaucoma clinic by the single examiner who took all measurements. In each patient, the right eye was the study eye unless the patient had corneal pathology or was monocular, in which case the left eye was used. One value from each device was recorded. In a subset of patients, the CCT of the study eye was also recorded. Additional data included age, ethnicity, gender, glaucoma type, and topical medications.
Results: :
A total of 31 eyes were included in the study (29 right and 2 left). Average age was 49.4 years (15–83 years). There were 2 Caucasians, 4 African–Americans, 24 Latinos, and 1 Asian. Average IOP with Goldmann applanation (17.16 mmHg) was 0.29 mmHg lower when compared to the average IOP measured with Perkins hand–held applanation (17.45 mmHg, p=0.649). IOP with Goldmann applanation ranged from 5–45 mmHg; IOP with Perkins hand–held applanation ranged from 4–55 mmHg. In 10/31 (32.3%) patients, IOPs were equal with Goldmann and Perkins applanation; in 15/31 (48.4%), IOPs were less with Goldmann than with Perkins; in 6/31 (19.4%), IOPs were greater with Goldmann than with Perkins. Of the 31 study eyes, CCT data was available for 20. Average of all CCT data was 546.9. All CCT data were divided into four groups: CCT<500, CCT = 500–555, CCT = 556–588, and CCT >588. For CCT<500, only two eyes were available for which the IOP with Goldmann and Perkins was equal (9 and 15 mmHg). For CCT = 500–555, average IOP with Goldmann (17.3 mmHg) was 1.1 mmHg greater than Perkins (16.2 mmHg, p=0.505). For CCT = 556–588, average IOP with Goldmann (20 mmHg) was 3 mmHg less than Perkins (23 mmHg, p=0.179). For CCT >588, average IOP with Goldmann (20.5 mmHg) was 1.75 mmHg greater than Perkins (18.75 mmHg, p=0.293).
Age, ethnicity, gender, glaucoma type, or ocular medication did not have a significant effect on IOP differences.
Conclusions: :
Goldmann slit–lamp mounted applanation resulted in lower (0.29 mmHg) IOP readings compared with Perkins hand–held applanation in a majority of patients (p=0.649). Additionally, CCT did not appear to have any significant effect on differences between the two devices. Demographic and ocular factors also did not have a significant effect on IOP. Perkins hand–held applanation may be an acceptable method to measure IOP.
Keywords: intraocular pressure • clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology