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Christopher Steven Pappa, Cynthia J Roberts, Ashraf M Mahmoud, Andrew N Springer, Robert H Small, William Bloom, Gloria Fleming; The influence of prostaglandin treatment on measurement of intraocular pressure using a pneumatonometer.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5316.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the influence of prostaglandins on the difference between measurements of intraocular pressure (IOP) using a pneumatonometer (PNT) and the PASCAL Dynamic Contour Tonometer (DCT) which is known to be less influenced by corneal biomechanical properties.
In an ongoing glaucoma study, 95 eyes of 49 subjects were divided into 2 groups: Group 1 with 51 eyes not receiving prostaglandin treatment at the time of enrollment, and Group 2 with 44 eyes receiving prostaglandin treatment. Normal individuals comprised the majority of Group 1. Both groups included diagnoses of primary open angle glaucoma, normal tension glaucoma, and ocular hypertension. Corvis ST was used to assess corneal biomechanical deformation response. Both intraocular pressure (IOP) and ocular pulse amplitude (OPA) were measured in the sitting position using the DCT and the PNT. DCT reports diastolic IOP, so mean DCT IOP (mDCT) was calculated by using the diastolic IOP value + ½OPA for comparison to PNT. Stepwise regression analysis was performed using SAS to predict the mDCT value in each group as a function of PNT IOP, PNT OPA, as well as corneal curvature (simK3mm), central corneal thickness (pachy), and stiffness parameter (SP-A1), all three measured by Corvis ST. Significance threshold was p<0.05.
Stepwise regression analysis showed the strongest predictor of mDCT based on strength of correlation in Group 1 was PNT IOP (R square 0.7184, C(p) 11.4984, p<.0001), followed second by corneal curvature (partial R square 0.0364, C(p) 5.9361, p=0.0103), and finally, pachymetry (partial R square 0.0251, C(p) 2.7306, p=0.0251). Model R square was 0.7799. Stepwise regression analysis showed the strongest predictor of mDCT in Group 2 was also PNT IOP (R square 0.5169, C(p) 16.6610, p<.0001). However, the next strongest predictor was corneal stiffness parameter (partial R square 0.0479, C(p) 13.0374, p=0.0396), followed by corneal curvature (partial R square 0.0465, C(p) 9.5831, p=0.0346), and pachymetry (partial R square 0.0621, C(p) 4.2954, p=0.0096). Model R square was 0.6735.
As expected, pneumatonometry measurement of IOP is affected by central corneal thickness in normal eyes, as well as pathologic eyes without treatment by prostaglandins, when compared to DCT. Corneal stiffness plays an additional important role in predicting DCT IOP measurement in eyes receiving prostaglandin therapy.
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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