Influence of the anterior chamber depth on the accuracy of the intraocular lens optical power calculation in short eyes

Background. The calculation of the optical strength of the intraocular lens (IOL) in eyes with a short anterior-posterior axis presents significant difficulties due to non-standard anatomical parameters of the eye, including the anterior chamber depth. Aim: determination of the relationship between the anterior chamber depth (ACD) and the accuracy of the IOL optical power calculation in eyes with an axial length of less than 22 mm. Methods. A total of 86 patients (133 eyes) with a short axis — from 18.54 to 21.98 (20.7 ± 0.9) mm, were included in the study. Group I (n = 29, 40 eyes) consisted of patients with ACD of less than 2.5 mm. Group II (n = 30, 49 eyes) included patients with ACD from 2.5 to 2.9 mm Group III (n = 27, 44 eyes) included patients with ACD greater than 2.9 mm. The calculation of the IOL optical power was carried out according to the formula SRK/T, the retrospective comparison was performed according to the Hoffer Q, Holladay II, Olsen, Haigis and Barrett Universal II formulas. Results. In all three groups, there was an increase in UCVA and BCVA in the postoperative period. In group I, there were no significant differences when comparing MedAE for the six formulas (p < 0.05). The highest MedAE values (0.51 and 0.49 respectively) and the smaller MNE range (-0.03 ± 0.89 and -0.01 ± 0.97 respectively) are shown for the Haigis and Barrett Universal II formulas. In group II, the MedAE for the Haigis formula was 0.45, for SRK/T and Olsen it was 0.59 and 0.66. For the Haigis formula, the lowest MNE value (0.05 ± 0.69) is shown. In group III, no significant differences were found when comparing the average values of MedAE (р > 0.05). The lowest MedAE (0.17) and the best MNE values (-0.01 ± 0.58) are shown for the Haigis formula, while the SRK/T formula was characterized by the highest MedAE (0.37). In group II, the refractive index ±0.25 and ±0.50 D for the Haigis formula was significantly higher. Conclusion. For eyes with ACD of less than 2.4 mm, none of the formulas showed a significant advantage, while for ACD of 2.4–2.9 mm and higher, the use of the Haigis formula is recommended, and the SRK / T formula showed the worst result. The data obtained dictate the need to review the existing standards for calculating the IOL optical power in patients with short eyes depending on ACD.