Accuracy of intraocular lens power calculations in eyes with axial length <22.00 mm

BACKGROUND: To assess the accuracy of Haigis, Holladay 1, Hoffer Q and SRK/T formulae in eyes with axial length of <22.00 mm. DESIGN: Retrospective comparative analysis. PARTICIPANTS: 163 eyes of 97 patients undergoing phacoemulsification and intraocular lens (IOL) implantation. METHODS: Ocular biometry was performed using IOLMaster laser interferometry. Predicted refractive outcomes before and after lens constant adjustment were compared to actual refractive outcomes. MAIN OUTCOME MEASURES: Mean prediction (ME) and mean absolute errors (MAE) with standard deviations (±SD). RESULTS: Mean preoperative spherical equivalent was +5.44D ± 1.97D. Mean axial length was 21.20 mm ± 0.60 mm. Using standard IOL constants the MAE for Hoffer Q (0.62D, ±0.52D) and Holladay 1 (0.66D ± 0.52D) were significantly lower than SRK/T (MAE 0.91D ± 0.64D; P = <0.0005 and P = 0.001 respectively), but not Haigis (MAE 0.82D ± 0.83D, P = 0.071 and 0.22 respectively). MAEs for all formulae were significantly reduced by IOL constant adjustment (all P = <0.001). Following this there was no statistically significant difference in MAEs between formulae (range 0.50-0.57D, P = 0.57). Increasing MAE was significantly associated with reducing axial length and increasing IOL power for all formulae. For bilateral cases, prediction errors between eyes were significantly correlated across all formulae (all P = <0.0001) and explained 32-42% of the variance in prediction error between eyes. CONCLUSIONS: Prediction of postoperative refraction in patients with short axial lengths is challenging and at the limit of current, popular IOL formulae. There is now a clear need for prospective studies to assess latest generation IOL formulae such as Holladay 2 or Olsen in small eyes.