24-Hour Contact Lens Sensor Monitoring of Intraocular Pressure-Related Profiles in Normal-Tension Glaucoma and Rates of Disease Progression.

PURPOSE: To determine the relationship between the rate of glaucomatous visual field loss and the amplitude of a 24-h intraocular pressure (IOP)-related profile measured using a contact lens sensor (CLS).
METHODS: This observational study included 22 patients with glaucoma and an IOP of consistently ≤21 mm Hg during office hours. All subjects underwent Goldmann tonometry, standard automated perimetry (SAP), dilated fundus examination, and had a CLS recording. A cosine function was used to obtain peak (acrophase), trough (bathyphase), and amplitude measurements. Prior rates of change in SAP mean deviation were calculated and compared to CLS parameters.
RESULTS: The patients had a mean (± SD) age of 66.6 ± 8.2 years (range 54-89 years). Mean follow-up was 6.6 ± 5.0 years with 8.3 ± 3.2 reliable SAP tests. The mean rate of change in SAP was -0.86 ± 1.0 dB per year (range -0.11 to -2.12 dB). Regression analysis suggested faster rates of prior visual field loss in eyes with higher-amplitude CLS curves, but this did not reach statistical significance (R2 = 0.174, p = 0.053). The CLS accurately identified waking and sleeping periods. 59.1% of eyes had a nocturnal acrophase (peaking between 23:00 and 07:00). There was no significant difference in rates of visual field change between patients with nocturnal or diurnal acrophase (-0.71 ± 1.17 and -1.07 ± 0.84 dB/year, respectively, p = 0.437).
CONCLUSION: CLS recordings in patients with normal-tension glaucoma (defined by office hours IOP) indicated that 60% of patients had peak IOP during nocturnal hours, which may not be captured using conventional methods of IOP measurement. Novel parameters obtained using the CLS may provide information for predicting the risk of visual field changes for patients with glaucoma.