Hybrid Approach to Intraocular Lens Calculations Recommended in Keratoconus

Cataract lens
Cataract Lens at the Tip of the Tweezers
Researchers sought to evaluate IOL calculation methods for patients with keratoectatic disorders and found a hybrid approach may be ideal.

Based on new study results, researchers recommend a hybrid approach to intraocular lens (IOL) calculations for patients with keratoectatic conditions undergoing cataract surgery. 

Intraocular lens calculations in patients with keratoconus and other keratoectatic disorders remain challenging for cataract surgeons due to the way the disease process affects keratometry readings,, according to the authors of a study published in Current Opinion in Ophthalmology.. The Researchers evaluated a number of studies in which different IOL formulas and calculations were used for patients with keratoectatic disorders undergoing cataract surgery.

They revealed that the Barrett II Universal calculation may be the most accurate calculation to use for eyes with mild to moderate keratoconus, whereas the SRK/T formula may provide the most reliable calculations overall. In one study of 73 eyes, the Barrett II Universal formula had the highest percentage of eyes within 0.5 D of predicted in stage 1 and stage II keratoconus (52% and 50%) compared with other formulas that had stage 1 and stage II accuracy scores of 40% and 20%. In another study of 41 eyes, the SRK/T formula produced a rate of 61.90% within 0.5 D of the target in stage I keratoconus, which decreased significantly to 30.77% in stage II. Researchers also learned that the accuracy of IOL calculations decreases with increasing keratoconus severity.

The study researchers concluded that a hybrid approach using the Barrett II Universal and SRK/T formulas should be adopted for IOL calculations in patients with keratoconus undergoing cataract surgery and that further research on newer IOL calculations may be needed to confirm their efficiency.


Smith RG, Knezevic A, Garg S. Intraocular lens calculations in patients with keratoectatic disordersCurr Opin Ophthalmol. 2020;31(4):284-287. doi: 10.1097/ICU.0000000000000671