Scleral intraocular pressure measurement in cadaver eyes pre- and postkeratoprosthesis implantation

Purpose. We correlated scleral IOP to assigned IOP using pneumatonometry in cadaver eyes before and after Boston type I keratoprosthesis (KPro) implantation. Methods. Corneal IOP and scleral IOP at the superonasal, superotemporal, inferotemporal, and inferonasal quadrants were measured using pneumatonometry in six cadaver eyes cannulated with an infusion line with assigned IOP held at 20, 30, 40, and 50 mm Hg. Measurements of scleral IOP at the same location were repeated after a KPro was implanted. Correlations between scleral IOP and assigned IOP were analyzed for the entire group of eyes, and for each individual eye before and after KPro. One eye was tested by another masked grader for interobserver variability. Results. Scleral IOP measured higher than corneal IOP by a mean of 13.2 mm Hg. For group analysis, pre-KPro scleral IOP had a positive and linear correlation with assigned IOP in all quadrants (P < 0.00001), and this correlation was preserved after KPro implantation (P < 0.00001). There was strong interobserver agreement in all measurement sites (P < 0.001). In analyses of individual eyes, scleral IOP measured at the inferotemporal quadrant confirmed the strong linear association between scleral IOP and assigned IOP before and after KPro for all study eyes. A Bland-Altman plot showed that the difference in scleral IOP between pre- KPro and post-KPro eyes fell mostly within ±5 mm Hg. Conclusions. Scleral IOP measured by pneumatonometry may be used to estimate IOP in cadaver eyes with and without keratoprosthesis. This may be a potential modality for assessing IOP for patients with corneal pathology or keratoprosthesis.