The Personalized Lens Constant (PLC) calculation is done automatically and you do not need to do anything except the obvious - entering PRE- and POST-op data. The PROGRAM automatically eliminates OUTLIERS, looks at the most recent data first, and usually takes from 30 to 50 cases for the PROGRAM to switch to the PLC and continues to UPDATE. The PROGRAM looks at the data from the time of surgery. There is no length of time for a post op in cataract surgery (no regression). If multiple post ops are entered for the same patient, the Program uses the most recent. It always looks at the data through a ‘rear view window’ so that if 1000s of cases are entered it only uses the most recent until statistical significance is reached. The FORMULA and LENS CONSTANT ANALYSIS SCREEN just shows you what is going on … you do not need to do anything. ‘PLC’ appears on the IOL CALC SCREEN (in place of Manuf CST) and on the PRINTOUT. You may look at the Formula and Lens Constant Analysis Screen and when column 3 and 5 are equal it is using the PLC
All we need is the Post OP Corrected VA and the Post OP Refraction to calculate the PLC. The Post Op K’s are necessary for calculation of the Surgically Induced Astigmatism (SIA), used in the Toric PreOp Planner
The calculation of the the PLC is done when the program starts. It doesn't happen automatically when you enter data. So closing and opening the program may be necessary. It's this calculation that is sometimes the cause of taking the program a long time to start on older computers or configurations with large datasets.
Are K's necessary?
The Post Op Refraction and IOL Power are necessary for determination of the Personalized Lens Constant (PLC), but the Ks are only important for determination of the Surgically Induced Astigmatism (SIA) from Ks.