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May 28, 2006
Acoustic Factor and Orbscan
Review Of Ophthalmologhy May 2006
Researchers from Glasgow Caledonian University say that, though Bausch & Lomb Orbscan’s acoustic correction factor is helpful in determining central corneal thickness, clinicians shouldn’t blindly rely on it when assessing more peripheral corneal locations.In an independent study, the investigators performed corneal pachymetry on 50 eyes of 25 healthy subjects. They extracted Orbscan II data at the geometric center, two mid-peripheral locations 2.5 mm to either side of the center, and peripheral locations 4.5 mm from the center along the horizontal meridian. They also obtained ultrasound readings from the same locations as Orbscan, after instillation of a drop of topical anesthetic. They took three readings at each location and averaged the measurements for each cornea.The differences between the two modalities were statistically significant at all corneal locations, and the researchers add that the customary acoustic correction factor of 0.92 didn’t correct them. Because of this, the researchers recommend using great caution when interpreting Orbscan depth measurements, especially in areas farther away from the corneal center.1326
Posted by mehdi khanlari at May 28, 2006 11:36 PM