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The surge of premium intraocular lenses in the US has prompted an even greater emphasis on ultrasound biometry. Fortunately, there have been many advances that have increased the accuracy and reliability of A-scan equipment. Determining which device is best for your practice, however, depends on several factors.
One of the most popular optical biometers is the IOLMaster from Carl Zeiss Meditec. This machine has undergone multiple upgrades and currently allows for more accurate keratometry and anterior chamber depth. The ability to calculate and provide personalized A constants allows physicians to fine tune their refractive outcomes. A similar device which is soon to become available in the US is the Lenstar LS 900 from Haag-Streit. By using optical low-coherence reflectometry (OLCR - a similar technology to OCT) it purports to deliver highly accurate A-scans.
Contact A-scan devices have the disadvantage of being more invasive for the patient, but they also have many benefits. To begin, they are significantly less expensive and typically do not need upgrades. For Dr. Ajit Nemi, founder of Lotus Vision in Alpharetta, Georgia, the decision to select a contact A-scan device was easy. “I purchased the PalmScan AP2000 (Micro Medical Devices) over a year ago and am extremely impressed with it. To begin, the device is extremely portable. This allows me or my technician to bring it into the room where I’m examining the patient and it improves the flow of the clinic. For physicians who work in multiple offices this would also be very easy to transport between them. The platform is very easy to read and the menu system is very intuitive. As far as accuracy I prefer to preform immersion A-scans and I have not had one refractive surprise since using it. Additionally, the PalmScan doubles as a pachymeter, which makes it a terrific value.” DGH offers similar double-function with its 5100E model. Both these models may be preferable to refractive surgeons who already have topography equipment and do not require the K values provided by non-contact optical biometry devices.
There is also more variability in the options available with different A-scan equipment; Alcon’s Ultrascan allows both A and B scans to be performed on the same device. This could be very important for those practitioners who see a lot of mature cataracts that preclude adequate visualization of the posterior pole.
Ultimately, there is a wide range of available biometry equipment. Non-contact optical biometers tout their accurate K readings and refractive predictability. However, contact A-scan devices can be very reliable as well, but in smaller and more affordable packages. There is no “best device” in this category. The final decision on which device you purchase depends on the type of practice you are developing.