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C. Yu, A. Shrivastava, D. Cartagena, U. Mian; Differences of Ocular Measurements by Nonimmersive Contact A-Scan versus IOL-Master in Patients With Cataracts. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1093.
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To investigate the difference of preoperative measurements of anterior chamber depth and axial length in patients with cataracts by non-immersive contact A-scan versus non-contact laser (IOL Master).
The anterior chamber depth(ACD) and axial length(AL) of 79 eyes from 44 preoperative patients with cataracts were measured by nonimmersive contact A-scan (Sonomed A-2500, USA) and non-contact laser (Carl Zeiss IOL MasterTM V.3.01, Germany) respectively. All measurement were taken by the same investigator (Ms. Cartagena, COA). The two sets of ACD and AL measurements were then analyzed.
The ACD was significantly deeper by 0.10 mm by A-Scan relative to the measurement taken by the IOL Master (p=0.015). The axial length was significantly smaller by 0.05 mm as measured by A-Scan relative to the measurement taken by the IOL Master (p=0.049). Clinically, this represents approximately a 0.15 diopter difference between the two techniques.
The anterior chamber depth and axial length measurements made by non-immersive contact A-scan and IOL Master were significantly different. The anterior chamber depth was surprisingly deeper in the contact technique, in which one would expect a shallower measurement due to compressive effects of the probe. The axial length was smaller as measured by the contact technique when comparing with the IOL Master. While this difference appears to be clinically insignificant (0.15D), it may become pertinent when implanting multifocal lenses.
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