Effect of the ratio of axial length to keratometry on SRK/T intraocular lens power calculations for eyes with long axial lengths

Effect of Intraocular Lens Power Calculation Formula Optimization in the Sum-of-Segments Optical Biometer

Purpose

We evaluated the effect of optimization of the intraocular lens (IOL) power calculation formula SRK/T and Barrett Universal II (BU II) in long eyes (≥26 mm: group L) and short eyes (≤22 mm: group S) using axial length calculated from segmented refractive indices (SRI).

Setting

Multicenter study at five sites in Japan.

Design

Retrospective observational study.

Methods

This study included 461 eyes of 461 patients (mean age 73.8 ± 8.4 years) who underwent cataract surgery. The predicted refractive error (PRE) was compared between the SRI (ARGOS) and the equivalent refractive index (ERI) biometers (IOLMasterTM700). The patients were randomly divided into two groups, a learning group and a validation group. The optimization constants were determined in the learning group, and the optimization constants were subsequently applied to the validation group and compared with the ERI biometer results.

Results

Using both SRK/T and BU II, the validation group's PRE using optimization constants for the SRI biometer in group L was significantly smaller than that using the ERI biometer (p<0.001, p<0.01). In group L, the arithmetic PRE of Barrett UII formula with SRI showed a significant improvement after optimization compared to before optimization (p<0.0001). In group S, the arithmetic PRE of SRK/T and Barrett UII formula with SRI showed a significant improvement (p<0.0001, p<0.0001).

Conclusion

In long and short eyes, the current study revealed that optimization of the SRK/T and Barrett formula constants for the SRI biometer was beneficial to achieve accurate refractive outcomes after cataract surgery.

Changes in the Ocular Parameters of Patients with Graves' Disease after Antithyroid Drug Treatment

Background and Objectives: To find the differences in ocular axial length, keratometric measurements, and intraocular lens (IOL) power in patients with Graves’ disease (GD) after treatment with a thionamide antithyroid drug (ATD), methimazole. Materials and Methods: The medical charts of 28 patients (4 males and 24 females; mean age: 47.2 ± 21.2 years) were studied. Each patient was examined twice using an IOL Master Device and keratometry at the first visit (before ATD treatment) and after 1 month of ATD treatment. The IOL power was calculated for each patient using the Hoffer Q, SRK-2, and SRK/T formulas according to axial length. Results: After 1 month, the axial length increased (right and left eyes: p < 0.001 and p = 0.05, respectively). Based on keratometry, changes in the horizontal and vertical optical power [in diopters (D)] were not statistically significant. However, the IOL power changed after 1 month of ATD treatment in 64.3% of the patients. In 14 patients (50%), there was a 0.5–1.0 D IOL power decrease in single eyes; in two patients (7.1%), an IOL power decrease of 0.5–1.0 D in both eyes; and in two patients (7.1%), a 0.5 D IOL power increase in single eyes. The calculated IOL power values were lower after ATD treatment (right and left eyes, p = 0.010 and p = 0.018, respectively). Conclusions: The IOL power changed in 64.3% of GD patients after ATD treatment. Therefore, avoiding cataract surgery at the early stage of ATD treatment would be appropriate for selecting a more accurate IOL power.