Customisation of 'A' constants
Customisation of 'A' constants has been proven to substantially improve the outcome of cataract surgery, thus improving patient care. The Royal College of Ophthalmologists' recommends that all departments should regularly audit their refractive outcomes and customise their 'A' constants.
Medisoft Ophthalmology stores the IOL model type, power, predicted post-operative refraction and formula used for every cataract procedure entered onto the system. When seen in a post-op clinic the actual refractive outcome of patients then automatically feeds back the necessary information to customise the 'A' constant for each IOL model.
When enough results have been collected (various exclusion criteria are applied so that only 'normal' operations are used) the program can automatically calculate the new recommended 'A' constants.
IOL Models are supplied with a manufacturer's 'A' constant for use in calculating the correct IOL power to use. However, there are substantial differences when measuring eyes using ultrasound rather than partial coherence interferometry (i.e. the Zeiss® IOL Master) which can cause refractive error in patients. Many surgeons already make manual adjustments to the IOL power calculations to adjust for these differences.
It is, therefore, very useful to be able to customise 'A' constants separately for ultrasound and PCI biometry methods for the best possible results. For each IOL model Medisoft Ophthalmology calculates recommended 'A' constants for both ultrasound and PCI biometry. For reference it also shows a breakdown of recommended 'A' constants for each formula used.