Evaluation of some factors affecting the agreement between the Proview Eye Pressure Monitor and the Goldmann applanation tonometer measurements.

BACKGROUND: Our aim was to examine whether training level and ocular factors could account for part of the difference in intraocular pressure (IOP) measured using the Goldmann applanation tonometer (GAT) and Proview Eye Pressure Monitor (PPT). METHODS: One hundred and nineteen individuals (238 eyes) were enrolled in the study. The mean age was 35.8 years (range 21 to 79). All study participants obtained IOP measurements using the PPT after hearing instructions on how to perform PPT. Glaucoma patients obtained additional IOP measurements using PPT after viewing an instructional video and after 30 days of home use. IOP was also measured using the GAT at each experimental session. RESULTS: The difference in IOP measured by the GAT and the PPT was 0.55 +/- 3.38 mmHg, 0.17 +/- 3.79 mmHg and -1.30 +/- 3.79 mmHg for myopic, emmetropic and hypermetropic groups, respectively, which were statistically significant (ANCOVA; p = 0.014). The difference in IOP between GAT and PPT was not significantly different for measurements obtained after verbal instructions, instructional video or after 30 days of home use (Repeated-ANCOVA; p = 0.30). The overall agreement between the GAT and the PPT was poor. Intra-class correlation coefficient was 0.575, and the 95% confidence interval (CI) of agreement was -6.93 to +6.73 mmHg. CONCLUSION: There was a small systematic difference in IOP measured by the GAT and PPT when comparing the different refraction groups; however, this level of difference between the groups is unlikely to be of clinical significance. The level of training in using the PPT did not influence its measurements. The limits of agreement between the PPT and the GAT were wide and long-term use of PPT did not improve its agreement.

Relationship of cerebral blood flow and central visual function in primary open-angle glaucoma.

PURPOSE: To investigate the relations between middle cerebral artery (MCA) blood flow velocities and central visual function measured by foveal cone electroretinograms (ERG) and visual field. METHODS: Fifteen primary open-angle glaucoma patients were recruited. The eye with the more severe visual field defect (full threshold 24-2) and/or optic disc damage was chosen. Measurements included brachial arterial pressure, heart rate, visual acuity (logMAR), contrast sensitivity (CSV-1000), central visual field (Humphrey SITA 10-2), foveal cone ERG, and transcranial Doppler. Pearson correlation coefficients were estimated to assess the strength of the linear relationship between the MCA flow velocity and the other measured parameters. RESULTS: Visual field was successfully completed in 12 eyes. We were unable to obtain ERG responses and MCA velocity readings for 1 patient. A significant correlation was observed between MCA mean flow velocity and focal cone ERG amplitude [r=0.69, n=13, confidence interval (CI) 0.22, 0.90, P=0.009], but correlation between mean foveal cone ERG implicit time and middle cerebral was not statistically significant (r=0.011, n=13, CI 0.47, 0.63). A significant correlation was also observed between MCA mean flow velocity and mean sensitivity (r=0.76, n=12, CI 0.32, 0.93, P=0.005), and mean defect (r=0.73, n=12, CI 0.28, 0.92, P=0.007) of the central visual field, logMAR visual acuity (r=0.57, n=14, CI 0.05, 0.84, P=0.036), and contrast sensitivity (r=0.61, n=13, CI 0.09, 0.87, P=0.027). CONCLUSIONS: Our findings suggest that in certain primary open-angle glaucoma patients diminished central visual function may be one manifestation of widespread cerebrovascular insufficiency.