Anterior chamber depth in relation to refractive status measured with the Orbscan II Topography System

To evaluate the anterior chamber depth (ACD) according to refractive status, assess the reliability of repeated ACD measurements using the Orbscan II Topography System (Bausch and Lomb), compare Orbscan II and IOLMaster (Carl Zeiss Meditec AG) ACD measurements, and investigate the correlation between refraction, axial length (AL), and ACD.

Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

In this clinical study, 60 patients with a mean age of 43.8 years +/- 18.74 (SD) were assigned to 1 of 3 groups of 20 patients each according to refraction: emmetropia group; hyperopia group (mean +4.84 +/- 1.60 diopters [D]); myopia group (mean -9.64 +/- 3.79 D). Using the Orbscan II system, 3 consecutive ACD measurements (apex and 3.0 mm zone) were performed. The IOLMaster was used to measure ACD and AL.

The mean ACD (from epithelium) with the Orbscan II and IOLMaster, respectively, was 3.61 +/- 0.24 mm and 3.61 +/- 0.24 mm in the emmetropia group, 3.03 +/- 0.21 mm and 3.06 +/- 0.24 mm in the hyperopia group, and 3.72 +/- 0.26 mm and 3.73 +/- 0.23 mm in the myopia group. The standard deviation of the repeated Orbscan II measurements increased from 13 to 15 microm from the apex to the 3.0 mm zone. The difference between the apex and 3.0 mm zone of the cornea in all groups ranged from 0.1 to 0.12 mm. The mean AL was 23.52 +/- 0.82 mm in the emmetropia group, 22.14 +/- 0.64 mm in the hyperopia group, and 27.44 +/- 1.67 mm in the myopia group. There was a significant correlation between the spherical equivalent and AL (r = 0.94).

Significantly lower ACD values were found in the hyperopia group than in the other 2 groups. There was no difference in ACD between the emmetropia and myopia groups even though the AL in the myopia group was 4.0 mm longer. No statistical difference in ACD measurements was found between the Orbscan II and IOLMaster.