Optimization of crystalline lens refractive index to improve the accuracy of intraocular lens power calculation in patients with dense cataract.

PURPOSE: To evaluate effects of crystalline lens refractive index (LRI) on prediction error (PE) and suggest the optimal LRI in cases of dense cataract.

SETTING

Chukyo Hospital, Aichi, Japan.

DESIGN

Retrospective consecutive case series study.

METHODS

Patients who underwent cataract surgery were enrolled and allocated into Group A (nuclear hardness ≤III) and B (nuclear hardness ≥IV) based on the Emery-Little classification. The swept-source optical biometer was used for biometric measurements. Assuming the postoperative axial length (AL) to be the valid value, a corrected LRI (CLRI) was calculated to make the preoperative AL equivalent to the postoperative one. In the validation group, the PE of the SRK/T formula and Barrett Universal II (BUII) were evaluated using the precorrection and postcorrection refractive indices.

RESULTS

Of the 5196 enrolled eyes, 1084 were evaluated. In Group A, there was no significant difference between the preoperative and postoperative ALs ( P = .07). In Group B, the mean postoperative AL (24.09 ± 2.05 mm) was significantly shorter than the mean preoperative AL (24.12 ± 2.06 mm) ( P < .001). The average CLRI in Group A and B were 1.41 and 1.42, respectively. In the validation group, the PEs using CLRI (SRK/T, 0.10 ± 0.48 diopters [D]; BUII, 0.03 ± 0.35 D) were significantly smaller than those using LRI (SRK/T, 0.18 ± 0.49 D; BUII, 0.12 ± 0.36 D) ( P < .001).

CONCLUSIONS

In cases of high lens nucleus hardness, the use of proposed CLRI demonstrated potentials for reducing PE.