Graves Orbitopathy Affects Corneal Biomechanical Parameters

Corneal biomechanical measurements vary according to clinical severity in patients with Graves orbitopathy (GO) and are different from those of healthy individuals, says a study published in International Ophthalmology.

Researchers conducted a prospective cross-sectional observational study to determine the changes between corneal biomechanical parameters and different clinical stages of GO in adult patients. 

The team measured corneal biomechanical properties (corneal hysteresis and corneal resistance factor), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) and classified the clinical severity stages of patients using clinical activity score (CAS) in accordance with the recommendations of European Group On Graves’ Orbitopathy. They compared ORA measures of patients with GO with those of healthy control individuals.

A total of 132 eyes of 66 patients with GO and 108 eyes of 54 healthy individuals in a control group participated in the study. The investigators classified 64 eyes as having a high CAS (≥3) and 68 eyes as having a low CAS (<3). 

The researchers reported mean corneal hysteresis values of 9.6±1 mm Hg in the high-CAS group, 10.2±0.9 mm Hg in the low-CAS group, and 11.4±1.7 mmHg in the control group (P <.001). With post hoc analysis, they found the mean corneal hysteresis was significantly lower in the high-CAS group than the low-CAS group (P <.001) and control group (P <.001). 

They reported mean corneal resistance factor values of 10.5±2.1 in the high-CAS group, 10.4±2.2 in the low-CAS group, and 10.43±2.0 in the control group and found no significant difference between the groups (P =.959). 

They reported mean IOPcc and IOPg values of 17.1±3.6 and 16.5±4.1 mmHg in the high-CAS group, 15.8±4.0 and 15.4±3.6 mmHg in the low-CAS group, and 15.2±4.1 and 14.9±3.9 mmHg, respectively, in the control group (P =.009 and P =.027, respectively, between all groups). 

“In conclusion, corneal biomechanical properties are different in [in patients with Graves’ orbitopathy] when compared with healthy individuals,” wrote the authors. “The severity of inflammation may be related to corneal biomechanical changes in [these patients].”

The primary limitation of the study was its small sample size.