Jiaonan Ma1, Yan Wang2,3, Weiting Hao1, Vishal Jhanji4. 1. Clinical College of Ophthalmology, Tianjin Medical University, No. 4. Gansu Road, He-ping District, Tianjin, 300020, China. 2. Clinical College of Ophthalmology, Tianjin Medical University, No. 4. Gansu Road, He-ping District, Tianjin, 300020, China. wangyan7143@vip.sina.com. 3. Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Nankai University Affiliated Eye Hospital, Tianjin, China. wangyan7143@vip.sina.com. 4. UPMC Eye Center, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Abstract
PURPOSE: To compare the difference between biomechanically corrected intraocular pressure (bIOP) and noncontact IOP measurement (IOPNCT) and to investigate the effect of corneal biomechanical properties on IOP. METHODS: IOP was evaluated in 1046 myopic eyes (544 subjects) using a conventional noncontact tonometer and a novel corneal visualization Scheimpflug technology (Corvis ST). Corneal biomechanical parameters were measured using the Corvis ST. RESULTS: The mean IOPNCT and bIOP values were significantly different (15.59 ± 2.56 mmHg and 15.89 ± 1.75 mmHg, respectively; P < 0.001). The bIOP showed a less correlation with central corneal thickness (CCT), compared with IOPNCT (P < 0.01). The IOPNCT was lower than the bIOP when the thickness of cornea was ≤ 550 μm but higher than bIOP when it was ≥ 550 μm (P < 0.01). A strong association was found between IOPNCT and deflection amplitude and deflection area at the highest concavity (HC DefA and HC DefArea), stiff parameter, maximum deformation amplitude (DAmax), and maximum deflection amplitude (DefAmax), as well as for bIOP (r > 0.500, P < 0.001). The bIOP could be calculated based on IOPNCT according to different values of CCT (P < 0.01). CONCLUSIONS: The bIOP was less affected by CCT as compared to IOPNCT. IOPNCT may be underestimated when the cornea is thinner and overestimated when the cornea is thicker because of the difference in corneal biomechanics.
PURPOSE: To compare the difference between biomechanically corrected intraocular pressure (bIOP) and noncontact IOP measurement (IOPNCT) and to investigate the effect of corneal biomechanical properties on IOP. METHODS: IOP was evaluated in 1046 myopic eyes (544 subjects) using a conventional noncontact tonometer and a novel corneal visualization Scheimpflug technology (Corvis ST). Corneal biomechanical parameters were measured using the Corvis ST. RESULTS: The mean IOPNCT and bIOP values were significantly different (15.59 ± 2.56 mmHg and 15.89 ± 1.75 mmHg, respectively; P < 0.001). The bIOP showed a less correlation with central corneal thickness (CCT), compared with IOPNCT (P < 0.01). The IOPNCT was lower than the bIOP when the thickness of cornea was ≤ 550 μm but higher than bIOP when it was ≥ 550 μm (P < 0.01). A strong association was found between IOPNCT and deflection amplitude and deflection area at the highest concavity (HC DefA and HC DefArea), stiff parameter, maximum deformation amplitude (DAmax), and maximum deflection amplitude (DefAmax), as well as for bIOP (r > 0.500, P < 0.001). The bIOP could be calculated based on IOPNCT according to different values of CCT (P < 0.01). CONCLUSIONS: The bIOP was less affected by CCT as compared to IOPNCT. IOPNCT may be underestimated when the cornea is thinner and overestimated when the cornea is thicker because of the difference in corneal biomechanics.
Authors: Anjali M Bhorade; Mae O Gordon; Brad Wilson; Robert N Weinreb; Robert N Weinrab; Michael A Kass Journal: Ophthalmology Date: 2009-02-25 Impact factor: 12.079