Lamina cribrosa morphology can be studied dynamically using optical coherence tomography. This can be achieved through imaging the lamina cribrosa before and during intraocular pressure (IOP) elevation by ophthalmodynamometry. Ophthalmodynamometer is no longer available. This study evaluated repeatability and reproducibility of Proview™ eye pressure monitor for acute transient IOP elevation.
A Proview™ eye pressure monitor was modified and calibrated at different reading scales of the device. Intra-examiner repeatability of IOP elevation was examined by increasing IOP of 12 eyes of 12 subjects. Baseline IOP was first measured by a non-contact tonometer (NT-530, Nidek, Japan). One examiner gently applied the Proview™ at the lower eyelid at a device scale of 30. Non-contact IOP was measured after the applied force was maintained for one minute, followed by another IOP measurement 5 minutes after releasing the applied force. The same examiner repeated the procedures again. Inter-examiner reproducibility was examined by increasing IOP of 6 eyes by 2 examiners. After a baseline non-contact tonometry, examiner 1 gently applied the Proview™ as before. IOP was measured at 5 seconds and then one minute while the applied force was maintained. After releasing the force and rested for 5 minutes, examiner 2 repeated the same procedures.
The force generated by the Proview™ was linear between scales 16 to 34 (Figure 1). At scale of 30, the applied force was around 93g. In intra-examiner repeatability, two-way analysis of variance did not reveal significant difference in IOP between the two trials (F = 1.268, p = 0.284) while IOP was significantly different between baseline and at 1-minute (with Bonferroni adjustment, p < 0.001). IOP was also significantly different between baseline and the final IOP measurements (with Bonferroni adjustment, p = 0.016). Average results from the first attempt were 14.8±3.9mmHg at baseline, 40.9±7.7mmHg at 1-minute, and 13.5±4.6mmHg at 5-minute after releasing the applied force. In inter-examiner reproducibility, two-way analysis of variance did not reveal significant difference in IOP between the two examiners (F = 0.053, p = 0.827) while significant difference was found between baseline and at 5-second (with Bonferroni adjustment, p = 0.002), baseline and at 1-minute (with Bonferroni adjustment, p = 0.001). IOP findings were similar at 5-second and 1-minute (with Bonferroni adjustment, p = 1.0). Average results from examiner 1 was 13.5±2.5mmHg at baseline, 39.1±10.2mmHg at 5-second, and 39.2±7.8mmHg at 1-minute.
Proview™ eye pressure monitor could be modified to provide acute transient IOP elevation. Good intra-examiner repeatability and inter-examiner reproducibility were demonstrated. IOP was found lower than the baseline values after the force was released for 5 minutes, probably due to massaging effect from eyeball compression.