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Sushma Tejwani, Mathew Francis, Shoruba Dinakaran, Rahul Mehta, rohit shetty, Abhijit Sinha Roy; Assessment of residual effects due to topical medication on corneal stiffness in primary open angle glaucoma. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3547.
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© ARVO (1962-2015); The Authors (2016-present)
We studied whether topical medication in primary open angle glaucoma (POAG) eyes altered the corneal stiffness using air-puff applanation and a viscoelastic model.
A total of 48 POAG eyes (60 ± 10 years) on glaucoma medication and 44 normal eyes (62 ± 10 years) were analyzed using Corvis-ST (OCULUS Optikgerate Gmbh, Germany), an air-puff applanation device using high speed scheimpflug imaging to measure corneal deformation. Patients were grouped into those using prostaglandin only, beta blocker only and a combination of prostaglandin plus beta blocker. In the combination group only one medication from each type was used. A viscoelastic model was applied to corneal deformation (Figure 1), which performed explicit quantification of corneal stiffness (kc), extra-ocular tissue stiffness (kg) and viscosity (µg). These parameters were then analyzed using multivariate analysis of covariance, using intraocular pressure (IOP) and central corneal thickness (CCT) as covariates. A p<0.05 was considered statistically significant. All measurements are reported as mean ± standard error of the mean.
Mean kc was 108.92 ± 2.90 N/m, 120.87 ± 6.28 N/m, 124.24 ± 5.51 N/m and 105.45 ± 4.94 N/m in the normal, prostaglandin group, beta blocker group and combination group, respectively. Multivariate analyses showed that both IOP (p=0.001) and type of medication (p=0.02) significantly correlated with kc indicating higher stiffness in the prostaglandin group and beta blocker group. Eyes in the combination group had kc similar to normal eyes (p>0.05). CCT (p=0.25), kg (p = 0.81) and µg (p = 0.89) were similar between the groups.
The study provided clinical evidence of modulated corneal stiffness in treated POAG eyes. However, the reasons behind differential modulation of corneal stiffness only in eyes using single medication are not fully understood. Further investigation with larger sample size is required.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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