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Shuchi Patel, Sara Duke, Andrew Logeman; A Prospective Trial Evaluating Scleral Rebound Tonometry. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3456.
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Glaucoma is known to occur in about 75% of patients following a keratoprosthesis, but accurate pressure readings to monitor for progression are not possible. Thus we sought to determine if a predictable relationship exists between Goldmann applanation tonometry (GAT) and scleral rebound tonometry (RT) to provide an accurate and reliable assessment of intraocular pressure (IOP) via scleral measurements.
A prospective non-randomized trial of individuals 18 years of age and older. Each had his/her IOP measured by GAT, next corneal RT then scleral RT on the inferotemporal sclera. The patient’s age, gender, refractive error, central corneal thickness (CCT), axial length (AL) and phakic status were recorded. Pearson’s correlation and multivariate regression were used for statistical analysis.
116 eyes from 59 patients (37-90 years old) have been examined to date. Mean GAT IOP was 15.91 mmHg (SD 4.13), mean corneal RT was 14.50 mmHg (SD 4.24) and mean scleral RT was 48.84 (SD 21.41). Mean spherical equivalent refraction (SE) was -0.21 D (SD 2.05), mean CCT was 547.68 µm (SD 45.65), mean AL was 24.06 mm (SD 1.21). 89 eyes were phakic and 27 were pseudophakic. Pearson analysis reveals a strong positive correlation between GAT and corneal RT (0.77) but weak positive correlation between GAT and scleral RT (0.22) as well as corneal RT and scleral RT (0.22). This trend persists when phakic and pseudophakic eyes are evaluated independently. In the final multiple regression model (Table 1) to evaluate the association of GAT, CCT, AL and SE with scleral RT, only CCT in pseudophakic eyes was found to have a significant positive correlation (p=0.04).
Scleral RT shows IOP measurements that are consistently higher than corneal IOP measurements by roughly 33-34 mmHg. Corneal RT correlates well to the gold standard of IOP measurement, GAT; unfortunately, scleral RT measurements have poor correlation to corneal measurements independent of phakic status. Analysis of scleral RT with relation to GAT, CCT, AL and SE concurrently fails to reveal a statistically significant regression model in either phakic or pseudophakic eyes. Our study reveals that sceral RT does not provide accurate and reliable IOP measurements.
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