Corneal biomechanical changes and intraocular pressure in patients with thyroid orbitopathy

AIM:To determine the relevance of the objective parameters addressing the altered biomechanical properties of cornea for glaucoma monitoring in patients with mild or moderate thyroid associated orbitopathy(TAO),and in healthy individuals.· METHODS:Twenty-five patients with TAO(group 1)and 25 healthy adults(group 2) were included to the study.Both groups were of a similar age and the ratio women:man.For each patient,the following parameters of both eyes were measured with ocular response analyzer(ORA):corneal hysteresis(CH),corneal resistance factor(CRF),Goldmann correlated intraocular pressure(IOPg) and corneal compensated intraocular pressure(IOPcc).In both groups participating in our study,all measurements were performed within minutes to reduce the diurnal effects.· RESULTS:The mean age in group 1 was 56±11y and76%were women,24%were men.The mean age in group 2 was 64±11y and 68%were women,32%were men.CH correlated negatively with IOPg in group 1(r~2=0.10,P <0.05).IOPg strongly correlated with IOPcc in both groups(group 1:r~2=0.79,P<0.0001;group 2:r~2=0.85,P<0.0001).There was positive correlation between CRF and IOPg in group 1(r~2=0.12,P<0.05) and in group 2(r~2=0.31,P<0.0001).Statistical analysis revealed no significant correlation between CRF and IOPcc in group 1(r~2=0.009,P >0.05) and also no significant correlation in group 2(r~2=0.04,P>0.05).CRF mean value in group 2(11.51±1.72 mm Hg) was higher than in group 1(10.85±1.45 mm Hg)(P<0.05).IOPg strongly correlated with IOPcc in both groups(group 1:r~2=0.79,P<0.0001;group 2:r~2=0.85,P <0.0001).There was also strong correlation between CRF and CH in both populations:group 1:(r~2=0.58,P<0.0001),group 2:(r~2=0.41,P <0.0001).· CONCLUSION:Biomechanical parameters of cornea,as quantified by CH and CRF,and measured together with IOPcc,precisely reveal glaucoma staging in TAO and thus are reliable for diagnosing and follow-up in clinical practice.