Comparative estimation of anterior chamber depth by ultrasonography, Orbscan II, and IOLMaster

Purpose: To assess the degree of agreement of anterior chamber depth (ACD) measurements by 2 optical devices (Orbscan II and IOLMaster) and compare them with contact ultrasound A-scan. Setting: Department of Ophthalmology at Hull Royal Infirmary, England. Methods: In this prospective study of 81 eyes of 41 consecutive patients, ACD estimation was done by 3 methods - scanning slit topography (Orbscan II), partial coherence interferometry (IOLMaster), and contact ultrasound A-scan in that order. The same observer performed all measurements. Repeated measures Analysis of Variance (ANOVA) was used to analyze difference between ACD measurements by the 3 methods. Difference in measurements between methods was assessed using the paired t test. Results: The mean ACD (±SD) by the 3 methods was 3.32 mm (0.60), 3.33 mm (0.61), and 2.87 mm (0.55), respectively. There was a statistically significant difference between measurements recorded by the 3 methods (P<.01). Mean contact A-scan measurements were 0.40 mm and 0.43 mm lower than by Orbscan II and IOLMaster respectively (P<.01). Conclusion: Applanation ultrasound gives consistently lower measurements for ACD compared to Orbscan II and IOLMaster. Although a high degree of agreement between Orbscan II and IOLMaster was noted, further studies are needed to assess the interchangeability of measurements in clinical practice.