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Brittany Simmons, Mengchen Xu, Qiuzhi Ji, Amy L. Lerner, Geunyoung Yoon; Isolated elevation of intraocular pressure and its impact on ocular aberrations in healthy eyes. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2443.
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To evaluate the feasibility of a non-contact method to temporarily elevate intraocular pressure (IOP) and to investigate the influence of an induced IOP on ocular aberrations.
Healthy volunteers (n=5) without a previous history of intraocular disease, trauma, or surgery were recruited for the study. An inversion table (Teeter Hang Ups, Puyallup, WA) was utilized to elevate IOP. Tono-Pen XL (Reichert, Buffalo, NY) was used to monitor the IOP of each subject’s right eye under three conditions: baseline (sitting upright) and two inversion angles of 135 degrees (D1) and 165 degrees (D2). A custom developed Shack-Hartmann wavefront sensor was then used to concurrently measure ocular aberrations under each condition. 0.5% tropicamide was used to dilate the pupil and paralyze accommodation prior to obtaining baseline measurements. Repeat measurements of ocular aberrations and IOP were taken at baseline and each inversion angle.
A significant (P<0.01) increase in IOP was observed within 1 minute after subjects achieved each inversion position. Repeat measurement confirmed a stable IOP elevation. From baseline to D1, IOP increased from 14.8 ± 1.9 mmHg to 23.7 ± 2.6 mmHg. A smaller increase was found from D1 to D2, with a highest IOP of 29.7 ± 3 mmHg. When subjects returned to the baseline position, IOP returned to normal values within 1 minute. Changes in ocular aberrations induced by the elevated IOP were observed in radially symmetric term, defocus (Z20) and asymmetric terms including astigmatism (Z2-2, Z22 ), trefoil (Z3-3, Z33), coma (Z3-1, Z31) and quadrafoil (Z4-4) of the eye. For pupil sizes ranging from 6 to 8 mm, the total wavefront root mean squared (RMS) value was 0.96 ± 0.69μm from baseline to D1 and 0.6 ± 0.24μm from baseline to D2. The difference in RMS between D1 and D2 was not statistically significant (P=0.80). In addition, a large inter-patient variability was observed in the magnitudes of changes in ocular aberrations among subjects.
In vivo IOP can be temporarily elevated in a safe, efficient, non-contact manner using an inversion table. IOP elevation caused significant changes in ocular aberrations in healthy eyes. Despite inter-subject variability, the statistically significant changes in the asymmetric wavefront aberrations might suggest spatially-varying collagen fibril distribution across normal human corneas.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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