Abstract
These days, accurate calculation of artificial lenses is an important aspect of patient
management. In addition to the classic theoretical optical formulae there are a number
of new
approaches, most of which are available as online calculators. This review aims
to explain the background of artificial lens calculation and provide an update on
study results based on the
latest calculation approaches. Today, optical biometry provides the computational
basis for theoretical optical formulae, ray tracing, and also empirical approaches
using artificial
intelligence. Manufacturer information on IOL design and IOL power recorded as
part of quality control could improve calculations, especially for higher IOL powers.
With modern measurement
data, there is further potential for improvement in the determination of the
axial length to the retinal pigment epithelium and by adopting a sum-of-segment approach.
With the available
data, the cornea can be assumed to be a thick lens. The Kane formula, the EVO
2.0 formula, the Castrop formula, the PEARL-DGS, formula and the OKULIX calculation
software provide
consistently good results for artificial lens calculations. Excellent refractive
results can be achieved using these tools, with approximately 80% having an absolute
prediction error within
0.50 dpt, at least in highly selected study populations. The Barrett Universal
II formula also produces excellent results in the normal and long axial length range.
For eyes with short axial
lengths, the use of Barrett Universal II should be reconsidered; in this case,
one of the methods mentioned above is preferable. Second Eye Refinement can also be
considered in this patient
population, in conjunction with established classic third generation formulae.
Key words
biometry - cataract - IOL - lens calculation - IOL formula
