Accuracy of the SRK/T Formula in Pediatric Cataract Surgery

Abstract

Purpose Determining IOL power is an important step in achieving the desired postoperative refractive target, but this determination remains challenging, as currently the used formulas were developed using IOL power calculations derived from adults. Patients and Methods This is a retrospective analytical study with the period of June 2018 to May 2019. All of the data were taken from medical records in referral tertiary eye hospital in Indonesia. All type of cataracts underwent uncomplicated surgeries and in-the-bag IOL implantation were included in this study, while aphakia, secondary IOL implantation, primary sulcus implantation, and history of ocular disorders were excluded. The data were analyzed using Wilcoxon sign-rank, paired t, and Kruskal–Wallis tests. Results Sixty-seven patients (106 eyes) were found to meet the inclusion criteria, average age was 7.35 ± 4.61 years (1.00 to 17.00 years). Average targeted refraction was 1.69 ± 2.06 D (−0.38–+6.99 D), and spherical equivalent (actual postoperative refraction) was −0.90 ± 1.45 D (−4.38 to +2.75 D). There was statistically significant difference between preoperative targeted refraction and actual postoperative refraction (p < 0.001). Mean absolute prediction error (APE) in general was 1.34 ± 1.18 D, 1.22 ± 0.88 D (in short eyes), 1.52 ± 1.37 D (in moderate eyes), and 0.69 ± 0.52 D (in long eyes) (p = 0.202). Mean APE in age group <7 years old was 1.27 ± 1.18 D and ≥7 years-old was 1.42 ± 1.19 D (p = 0.429). Conclusion SRK/T formula is fairly accurate in calculating IOL power in pediatric cataract surgery. Mean APE in this study was within the range of accurate mean APE in pediatric patients despite differentiated axial length and age.

Intraocular lens calculation using the ESCRS online calculator in pediatric eyes undergoing lens extraction

“…Others report lower predictability using the SRK/T formula as well, with a higher myopic shift, especially in young children, or short and normal eyes and lower amount of eyes within ±0.5 D from target refraction. [16][17][18][19][20][21][22] Others report a hyperopic shift for all of their tested formulas using second and third generation formulas, which is contrary to our results. 22 In previous studies, it was shown that in pediatric cataract surgery, the implantation of an IOL with posterior optic capture is the best alternative to prevent posterior capsule opacification.…”

“…Others report lower predictability using the SRK/T formula as well, with a higher myopic shift, especially in young children, or short and normal eyes and lower amount of eyes within ±0.5 D from target refraction. 16–22 Others report a hyperopic shift for all of their tested formulas using second and third generation formulas, which is contrary to our results. 22…”

Accuracy of Modern and Traditional Intraocular Lens Power Calculation Formulas in Pediatric Cataract Surgery

“…The SRK/T formulae did not show statistically significant differences in patients aged > 5 years. Irfani et al 22 studied the accuracy of SRK/T formula in pediatric cataract surgery; they reported MAE in age group < 7 years = 1.27 ± 1.18 D. The current study reported better outcomes with SRK/T with MAE = 0.73 + 0.55 D. The better results of the current study can be explained by A-constant optimization. Thanapaisal et al 23 also studied the accuracy of the SRK/T formula in pediatric cataract surgery and reported an MAE = 1.41 of 1.22 D. The reason for the higher MAE might be that they included traumatic and sulcus implantation cases.…”

“…Theoretical formulas are based on the adult schematic eye; they can be theoretically extrapolated better in children by proportionally downsizing the variables to pediatric dimensions. [20][21][22][23] In the current study, the SRK/T formula showed better results for the entire cohort. When subdividing the cases into two groups, SRK/T still showed superiority for patients aged between 2 and 5 years.…”