Intraocular Lens Power Calculation Formulas In High Refractive Errors…. What To Choose And When?
A-scan formulas: comparision in high refractive error
Keywords:
Cataract surgery, High myopia, High hypermetropia, A scan , Intraocular lens power calculationsAbstract
Background & Objectives: Before performing the cataract surgery high level of expertise and
knowledge is required to fulfil the ever increasing demands of patients. This makes a surgeon carry out
detailed evaluation of a case and formulate a ‘customized IOL’. Accurate IOL power calculation is the most
important part of planning a cataract surgery. Most of the formula works well with normal axial length, but
with high refractive errors, there are many discrepancies for selection of IOL formula. Methods: Study
included 80 high myopic eyes divided into three groups and 20 high hypermetropic eyes divided into two
groups according to various A scan formulas utilised. Post-operative spherical equivalent in relation to various
formulas for all groups compared. Results: Performance of all 3 formulas in high myopic group showed SRK/T
formula to be most accurate with smallest Mean Absolute Error (MAE) in all axial length subcategories above
24mm, followed by Haigis, and Holladay I respectively. In high hypermetropic patients, among 2 formulas, the
lowest MAE was found with Hoffer-Q (-0.03D) compared to SRK/T (-0.96D) Interpretation & Conclusion:
Erroneous IOL power calculation can spoil high quality results expected by patients in terms of post-operative
vision in spite of excellent surgery.
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