Studying the added effect of sum-of-segments biometry to modern intraocular lens power calculation formulas for short
Hany Ahmed Helaly1, Mohamed Hassan Elkhawaga2, Mohamed Sobhy El-Mansy2
1Ophthalmology Department, Faculty of Medicine, Alexandria University, 30 Roshdy Street, Roshdy, Alexandria, Egypt. hany209209@yahoo.com.
Purpose:
To study the added effect of sum-of-segments (SOS) biometry to modern intraocular lens power calculation formulas for eyes with short axial length.
Methods:
This was a retrospective case series that included 99 eyes from 99 patients. Preoperative AXL measurements were conducted utilizing the ARGOS biometer (Alcon, Inc., Fort Worth, TX). The following formulas were used: Barrett Universal II (BUII), Cooke K6, EVO 2.0, and PEARL-DGS formulas. Additionally, the Barrett formula has been updated and is now incorporated into the ARGOS biometer, introducing the Barrett true axial length (BTAL) formula.
Results:
EVO 2.0sos and PEARL-DGSsos formulas had the highest cases within ± 0.25 D of the intended refraction (45.45% and 42.42%, respectively). The PEARL-DGSsos was the only formula to show a myopic mean prediction error (-0.25 ± 0.36 D). The Cooke K6 formula showed the highest hyperopic mean prediction error (0.55 ± 0.35 D), followed by EVO 2.0, Cooke K6sos, and BUII formulas. BTAL had mean prediction error of 0.15 ± 0.47 which is less hyperopic than BUII (0.43 ± 0.39 D). Subgroup analysis of eyes with AXL 21 mm or shorter (n = 57) was done. Again, the PEARL-DGSsos formula showed the only myopic mean prediction error (-0.23 ± 0.37 D).
Conclusion:
PEARL-DGSsos was the only formula to show a myopic mean prediction error. Using BTAL and SOS option in Cooke K6, EVO 2.0, and PEARL-DGS formulas decreased the undesirable hyperopic shift in the mean prediction error. This effect was more evident in shorter eyes ≤ 21.0 mm.
