Comparison of the Barrett Universal II, Kane and VRF-G formulas with existing intraocular lens calculation formulas in eyes with short axial lengths

Accuracy of the VRF and VRF-G Intraocular Lens Power Calculation Formulas Using Swept-Source Optical Coherence Tomography Biometry

Purpose

To collate the accuracy of two recently introduced intraocular lens (IOL) formulas (VRF and VRF-G) in cataract patients using a swept-source optical coherence tomography (SS-OCT) biometry (IOL Master 700, Carl Zeiss Meditec AG, Jena, Germany).

Patients and Methods

Data records of 295 eyes from 295 patients were included in this scrutiny. The IOLMaster 700 SS-OCT biometer was used for biometric measurements. The VRF and VRF-G formulas were compared with seven 3rd and 4th generation thin and thick-lens formulas: Haigis, Hoffer Q, Holladay 1, Holladay 2, SRK/T, T2, and Barrett Universal II. With optimized lens constants, the mean prediction error (PE) and its standard deviation (SD), the median absolute error (MedAE), the mean absolute error (MAE), and the percentage of eyes with PEs within ±0.25 D, ±0.50 D, ±0.75 D, ±1.00 D, and <±2.00 D were analyzed.

Results

Statistically significant differences were found between formulas in the whole group (Friedman test, P = 0.000). The VRF-G and Haigis formulas showed the lowest SD values (0.464 D and 0.466 D respectively). The VRF and Barrett Universal II formulas were less predictable (SD 0.471 D and SD 0.474 D respectively). The biggest proportion of eyes within ±0.50 D was found with VRF-G (76.27%), Haigis (75.59%), VRF (74.92%), and Barrett Universal II (74.92%) formulas.

Conclusion

Based on data achieved from the SS-OCT biometry, the VRF-G and Haigis methods were the more precise predictors of postoperative refraction with the biggest proportion of eyes within ±0.50 D.

Accuracy of new intraocular lens calculation formulas in Chinese eyes with short axial lengths

Purpose

To compare the measurement accuracy of new/updated intraocular lens (IOL) power calculation methods, namely, Kane, Emmetropia Verifying Optical (EVO), with existing methods (Barrett Universal II, Olsen, Haigis, Hoffer Q, Holladay 1, SRK/T) in Chinese eyes with axial lengths ≤ 22.5 mm.

Methods

The study included data from patients who underwent uneventful cataract surgery with the insertion of ZCB00 IOL. Refractive prediction errors were determined by calculating the difference between postoperative refraction and the predicted refraction using each formula. Various parameters were evaluated, including mean prediction error (ME), mean absolute error (MAE), median absolute error (MedAE), and the percentage of eyes with prediction errors (PE) within different ranges.

Results

The study enrolled 38 eyes of 38 patients, and the Barrett Universal II formula demonstrated the lowest MAE and MedAE among the tested formulas. Post hoc analysis using Wilcoxon signed-rank pairwise comparisons for non-parametric samples with Bonferroni correction revealed no significant difference in postoperative refractive prediction among all the formulas (P > 0.05). The percentage of eyes with PE within ± 0.5 D was as follows: Barrett Universal II, 81.58%; Haigis, 78.95%; EVO, 76.32%; Olsen, 76.32%; Holladay I, 73.68%; SRK/T, 71.05%; Kane, 68.42%; and Hoffer Q, 65.79%.

Conclusion

The Barrett Universal II formula was more accurate than the other formulas for Chinese eyes with AL ≤ 22.5 mm.

Accuracy of Different Lens Power Calculation Formulas in Patients With Mature Cataracts

Introduction To compare the prediction accuracy of lens power calculation formulas in patients undergoing mature cataract surgery. Methods A total of 90 operations involving the Alcon SA60AT IOL implant (Alcon, Geneva, Switzerland) were analyzed in terms of mean refractive prediction error (PE) and mean absolute prediction error (MAE) using backward calculation in a retrospective design. Results A negative PE was observed in SRK/T, Holladay 1, Holladay 2, Hoffer Q, Haigis, and Emmetropia Verifying Optical (EVO) formulas. In contrast, positive PEs were observed in Barrett Universal II (BAUII), Kane, and Radial Basis Function (RBF) formulas. Negative PE was observed with all formulas, except BAUII, in patients with a shallow anterior chamber depth (ACD). While the SRK/T, Holladay 1, BAU, Kane, and RBF formulas demonstrated positive PE, the Holladay 2, Hoffer Q, Haigis, and EVO formulas indicated negative PE. In patients with deep ACD, positive PE was observed in all formulas, barring Holladay 2 and EVO. No significant differences were identified between the formulas concerning MAE and percentages of 0.25 diopter (D), 0.50 D, 0.75 D, and 1.0 D across all study groups. Conclusion Although the new generation formulas provide very good results, achieving the best with a single formula is still impossible.

Refractive outcome and lens power calculation after intrascleral intraocular lens fixation: a comparison of three-piece and one-piece intrascleral fixation technique

PURPOSE

To evaluate the refractive prediction error of common intraocular lens (IOL) power calculation formulae in patients who underwent intrascleral IOL fixation using two different techniques.

METHODS

This is a prospective, randomized, longitudinal, single-site, single-surgeon study. Patients who underwent intrascleral IOL implantation using the Yamane or the Carlevale technique were followed up for a period of six months postoperatively. Refraction was measured using the best-corrected visual acuity at 4 m (EDTRS chart). Lens decentration, tilt and effective lens position (ELP) were assessed using an anterior segment optical coherence tomography (AS-OCT). The prediction error (PE) and the absolute error (AE) were evaluated for the SRK/T, Hollayday1 and Hoffer Q formula. Subsequently, correlations between the PE and axial length, keratometry, white to white and ELP were assessed.

RESULTS

In total, 53 eyes of 53 patients were included in the study. Twenty-four eyes of 24 patients were in the Yamane group (YG) and 29 eyes of 29 patients were in the Carlevale group (CG). In the YG, the Holladay 1 and Hoffer Q formulae resulted in a hyperopic PE (0.02 ± 0.56 D, and 0.13 ± 0.64 D, respectively) while in the SRK/T formula the PE was slightly myopic (- 0.16 ± 0.56 D). In the CG, SRK/T and Holladay 1 formulae led to a myopic PE (- 0.1 ± 0.80 D and - 0.04 ± 0.74 D, respectively), Hoffer Q to a hyperopic PE (0.04 ± 0.75 D). There was no difference between the PE of the same formulae across both groups (P > 0.05). In both groups the AE differed significantly from zero in each evaluated formula. The AE error was within ± 0.50 D in 45%-71% and was within ± 1.00 D in 72%-92% of eyes depending on the formula and surgical method used. No significant differences were found between formulae within and across groups (P > 0.05). Intraocular lens tilt was lower in the CG (6.45 ± 2.03°) compared to the YG (7.67 ± 3.70°) (P < 0.001). Lens decentration was higher in the YG (0.57 ± 0.37 mm) than in the CG (0.38 ± 0.21 mm), though the difference was not statistically significant (P = 0.9996).

CONCLUSIONS

Refractive predictability was similar in both groups. IOL tilt was better in the CG, however this did not influence the refractive predictability. Though not significant, Holladay 1 formula seemed to be more probable than the SRK/T and Hoffer Q formulae. However, significant outliers were observed in all three different formulae and therefore remain a challenging task in secondary fixated IOLs.

A Comparative Study on the Accuracy of IOL Calculation Formulas in Nanophthalmos and Relative Anterior Microphthalmos

PURPOSE

We sought to compare the prediction accuracy of 6 intraocular lens (IOL) formulas, namely, the Haigis, Hoffer Q, Holladay I, SRK/T, Barrett Universal II and Hoffer QST formulas, in microphthalmic eyes, including those with nanophthalmos and relative anterior microphthalmos (RAM).

DESIGN

Retrospective case series.

METHODS

Twenty-six eyes with nanophthalmos (axial length [AL] 16.84 ± 1.36 mm, range 15.25 mm-19.82 mm) and 12 eyes with RAM (corneal diameter 8.41 ± 0.92 mm, range 7.00 mm-9.50 mm) receiving cataract surgery were included. The IOL Master 500 was used for biometry; thus, lens thickness (LT) was omitted in the IOL power calculation. The mean and median arithmetic and absolute prediction errors (PEs) of the 6 original calculation formulas, the absolute PEs of the 6 formulas after optimization, and the proportion of PEs within ±0.25 diopters (D), ±0.5 D, ±1 D, and ±2 D with each formula were compared. The factors influencing PE were analyzed by multivariate regression.

RESULTS

In the nanophthalmos group, the overall prediction results were shifted to myopia. The original Haigis formula had the smallest median absolute PE (1.61 D, P < 0.001), and the optimized Haigis formula had the highest proportion of PEs within ±0.25 D, ±0.5 D, and ±1 D. In the RAM group, the overall prediction results were not significantly different from 0 (P > .05). No significant difference was found among the formulas before optimization (P = .146) and after optimization (P = .161), but the optimized Barrett Universal II formula had the highest proportion of PEs within ±1 D and ±2 D.

CONCLUSIONS

When omitting the LT parameter in the calculation, the Haigis formula was the most accurate in cataract patients with nanophthalmos (AL <20 mm) among the 6 IOL calculation formulas, and the Barrett Universal II formula had the highest accuracy in cataract patients with RAM (corneal diameter ≤9.5 mm).

Cataract surgery in adult eyes with short axial length

PURPOSE OF REVIEW

Cataract surgery in eyes of patients with short axial length (AL) can be technically challenging and is associated with a high risk of intra- and postoperative complications. Several technical and surgical strategies have been proposed to optimize the visual outcome and decrease the rate of surgical complications and it is important to understand their applications in these cases.

RECENT FINDINGS

Traditional intraocular lens (IOL) measurement formulas in eyes with short AL have reduced reliability. Novel formulas such as the Kane formula provide a better refractive prediction. Surgery can be difficult in short eyes due to the crowdedness of the anterior chamber (AC) and the associated scleral abnormalities increasing the risk of uveal effusion. Surgical techniques such as prophylactic scleral incisions, limited pars plana anterior vitrectomy, and modified hydrodissection, have been shown to facilitate surgery in extremely short eyes and decrease the rate of operative complications. Although cataract surgery improves vision in these cases, short AL and shallow AC have been associated with worse visual outcomes.

SUMMARY

Newer 4 th generation IOL formulas have improved the refractive outcomes of cataract surgery in eyes with short AL. There are multiple evolving surgical strategies for optimizing surgery in these eyes. However, studies on the surgical and visual outcomes of cataract surgery in eyes with short AL are limited by their design and sample size. With further research and continued clinical experiences, we hope to develop evidence-based algorithms for the management of these complex cases.