PURPOSE: To study the repeatability of the biomechanical waveform parameters measured with the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, NY) device in normal eyes and eyes after refractive surgery. METHODS: This was a prospective, comparative non-interventional study of a case series. Two hundred eyes of 100 patients were divided into five groups: normal eyes of patients younger than 30 years, normal eyes of patients between 30 and 50 years old, normal eyes of patients older than 50 years, eyes of patients with a history of LASIK, and eyes of patients with a history of photorefractive keratectomy. The repeatability of the 37 waveform parameters in addition to corneal hysteresis (CH), corneal resistance factor (CRF), IOP measurement with Goldmann applanation tonometer (IOPg), and IOP evaluated with the intraclass correlation coefficient (ICC) (IOPcc) were examined. RESULTS: In addition to IOPg, IOPcc, CRF, and CH, five parameters had an ICC greater than 0.6 (substantial agreement): P1area, the area of peak 1 (ICC = 0.823); P2area, the area of peak 2 (ICC = 0.646); h1, the height of peak 1 (ICC= 0.702); P1area1, the area of peak 1 derived from the upper 50% of the applanation peak (ICC = 0.772); and h11, the height of peak1 derived from the upper 50% of the applanation peak 1 (ICC = 0.697). CONCLUSIONS: This study shows that not all parameters derived from the corneal deformation waveform signal have the same repeatability. Therefore, analysis of the waveform indices should rely on the more repeatable ones to derive consistent conclusions. Copyright 2013, SLACK Incorporated.
PURPOSE: To study the repeatability of the biomechanical waveform parameters measured with the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, NY) device in normal eyes and eyes after refractive surgery. METHODS: This was a prospective, comparative non-interventional study of a case series. Two hundred eyes of 100 patients were divided into five groups: normal eyes of patients younger than 30 years, normal eyes of patients between 30 and 50 years old, normal eyes of patients older than 50 years, eyes of patients with a history of LASIK, and eyes of patients with a history of photorefractive keratectomy. The repeatability of the 37 waveform parameters in addition to corneal hysteresis (CH), corneal resistance factor (CRF), IOP measurement with Goldmann applanation tonometer (IOPg), and IOP evaluated with the intraclass correlation coefficient (ICC) (IOPcc) were examined. RESULTS: In addition to IOPg, IOPcc, CRF, and CH, five parameters had an ICC greater than 0.6 (substantial agreement): P1area, the area of peak 1 (ICC = 0.823); P2area, the area of peak 2 (ICC = 0.646); h1, the height of peak 1 (ICC= 0.702); P1area1, the area of peak 1 derived from the upper 50% of the applanation peak (ICC = 0.772); and h11, the height of peak1 derived from the upper 50% of the applanation peak 1 (ICC = 0.697). CONCLUSIONS: This study shows that not all parameters derived from the corneal deformation waveform signal have the same repeatability. Therefore, analysis of the waveform indices should rely on the more repeatable ones to derive consistent conclusions. Copyright 2013, SLACK Incorporated.