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First Author: F.Esteves PORTUGAL
Co Author(s): J. Borges R. Almeida P. Neves N. Porta J. Méijome I. Cardoso
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To evaluate the differences in the biomechanical corneal properties measured with Corvis ST and Ocular Response Analyzer (ORA) in a population of young healthy people and a population of pre-cataract patients.
Ophthalmology Department of CHEDV, Feira
Eighty right eyes from 80 healthy young patients (60 females, 20 males; mean age=25ḟ5years) and 54 right eyes from 54 elderly patients scheduled for cataract surgery (32 females, 22 males; mean age=73ḟ7years) were included in the study. All patients were evaluated with Ocular Response Analyzer (ORA, Reicher, Depew, NY) and Corvis ST (Oculus, Wetzlar, Germany) in random order in the same session. Measurements were performed in the morning between 9:00 and 11:00 AM (minimum of 2 hours after awaking). Considering the normal distribution of data, comparisons were performed using independent sample T-test.
No significant differences in IOP were obtained from Corvis ST tonometry (p=0.079), while Goldmann equivalent intra-ocular pressure (IOPg) and corneal compensated intra-ocular pressure (IOPcc) values provided by ORA were significantly higher for the elderly population (p<0.001). Corneal hysteresis (CH) provided by ORA was significantly lower in the elderly population (mean diff.=2.0 mmHg; p<0.001). No differences were found in pachymetry data provided by Corvis ST between both groups. Several parameters obtained from Corvis ST presented statistically significant differences between young and elderly groups; those parameters included: time and velocity for applanation 2 being higher in younger subjects (p<0.001) as well as highest concavity peak distance being higher in youth (p=0.002) and highest concavity radius being flatter in elderly (p<0.001).
Present results show that Corvis ST and ORA are able to detect small differences in the biomechanical behavior of the cornea between young and elderly patients. Changes observed are consistent with a trend towards a flatter radius of the deformation concavity in elderly corneas and a faster recovery after deformation in younger corneas representing a trend towards a lower elasticity in elderly. Intra-ocular pressure changes present between both populations might help to explain the differences detected but changes in the homeostasis of the corneal tissue cannot be excluded.