Comparison of IOL power calculations by the IOLMaster vs theoretical calculations.
OBJECTIVE
This study evaluates the agreement between the calculations performed by IOLMaster and as performed according to the published methods, for three formulas, Holladay I, Hoffer Q, and SRK-T.


METHODS
Hypothetical and identical data were used as input variables for calculations by IOLMaster and by a computer program written in visual basic to perform calculations with the three formulas. Results were compared and statistical significance carried out.


RESULTS
Significant disagreement was found using Hoffer-Q formula between the results shown by the study program and IOLMaster, while identical results were obtained using Holladay I and SRK-T formulas. For an average eye (AL 23.45 mm and K 45D, ACD constant 6.15, vertex 12 mm), the mean difference in the predicted postoperative (postop) SE between the study-set and IOLMaster dataset was 0.13 D (+/-0.03 D), which is a measure for the systematic error (relative bias). In such eyes, the mean predicted postop ACD in IOLMaster dataset was 0.11 mm (+/-0.04 mm) less than in the study-set, and the data spread of the predicted postop ACD was much higher (+/-0.042 mm) indicating more discrepancy in predicting ACD with IOLMaster.


CONCLUSIONS
When using Hoffer-Q formula, the mean predicted postop SE with IOLMaster was 0.13 D less than the computation in this study, that is, IOLMaster was showing a consistently myopic overestimation, or, a mean undercorrection of necessary intraocular lens power by 0.13 D, or, a residual hyperopic error of 0.13 D. This translates to a consistently more anterior estimation (0.11 mm mean) of predicted postop ACD by IOLMaster, as compared with theoretical analysis.
Basu
S
S
Department of Ophthalmology, William Harvey Hospital, Kennington Road, Ashford, Kent TN24 0LZ, UK. sbasu2003@doctors.net.uk
D000465:Algorithms; D006801:Humans; D007910:Lenses, Intraocular; D008962:Models, Theoretical; D055095:Optics and Photonics; D012029:Refraction, Ocular; D012984:Software