Comparison of aphakic refraction formulas for secondary in-the-bag intraocular lens power estimation in children

A Bayesian network meta-analysis on comparisons of intraocular lens power calculation methods for paediatric cataract eyes

The study aimed to compare and rank the accuracy of formulas for calculating intraocular lens (IOL) power in paediatric eyes in a systematic way. A literature search was conducted in Pubmed, Web of Science, Cochrane Library, and EMBASE by December 2021. Combined with traditional and network meta-analysis, we analysed the percentages of paediatric eyes with prediction error (PE) within ±0.50 dioptres (D) and ±1.00 D as the outcome measurements among different formulas. Subgroup analyses stratified by age were also undertaken. Thirteen studies with 1781 eyes comparing 8 calculation formulas were included. For the traditional meta-analysis results, Sanders-Retzlaff-Kraff theoretical (SRK/T) (risk ratios (RR), 1.15; 95% confidence intervals (CI), 1.03-1.30) performed significantly better than the SRKII formula for the percentage of eyes with PE within ±0.50 D. In addition, SRK/T (RR, 1.10; 95% CI, 1.02-1.18) and Holladay 1(RR, 1.15; 95% CI, 1.01-1.30) both performed significantly better than the SRKII formula for the percentage of eyes with PE within ±1.00 D. Considering the ranking based on the surface under the cumulative ranking curve (SUCRA) by Bayesian method, the top four formulas were Barrett Universal II (UII), Haigis, Holladay 1, and SRK/T on the percentage of PE within ±0.50 D, whereas the top four formulas were Barrett UII, Holladay 1, SRK/T, and Hoffer Q formulas on the percentage of PE within ±1.00D. Concerning both outcome measurements of rank probabilities, the top three Barrett UII, SRK/T, and Holladay 1 formulas were considered to provide more accuracy for IOL power calculation in paediatric cataract eyes, and Barrett UII tends to perform better in older children.

Intraocular lens power calculation formula in congenital cataracts: Are we using the correct formula for pediatric eyes?

The major challenge these days in pediatric cataract surgery is not the technique of surgery or intraocular lens (IOL) used but the postoperative refractive error. Amblyopia occurring due to postoperative refractive error which the child has; destroys the benefit obtained by a near-perfect and timely surgery. Even if we settle the debate as to what should be the ideal postoperative target refraction, there is a postoperative surprise that is not explained by our conventional insights of an accurate power calculation in children. The role of IOL power calculation formulae in affecting the postoperative refractive error should not be underestimated. Therefore, which age-appropriate formula is to be used for children is unclear. This review is an update on major IOL power calculation formulas used in pediatric eyes. We have tried to define why we should not be using these formulas made for adult eyes and review the literature in this regard.

Comparison of Aphakic Refraction and Biometry-Based Formulae for Secondary In-The-Bag and Sulcus-Implanted Intraocular Lens Power Estimation in Children

PURPOSE

The aim of the study was to compare the accuracy of refractive outcomes in children undergoing secondary in-the-bag or cilliary sulcus intraocular lens (IOL) implantation, using aphakic refraction (AR)-based formulae (Hug and Khan) and biometry-based formulae (Holladay 1, Hoffer Q, SRK/T, and SRK II).

METHODS

In this retrospective study, a total of 65 eyes of 44 patients who underwent secondary in-the-bag or cilliary sulcus IOL implantation were included and divided into 2 groups: 39 eyes of the in-the-bag IOL group and the other 26 eyes of the sulcus-implanted IOL group. Holladay 1, Hoffer Q, SRK/T, and SRK II formulae were employed depending on the biometric data, while Hug and Khan formulae were used based on preoperative AR. The prediction error (PE) and the absolute value of predicted error (APE) were compared between the 2 groups and formulae.

RESULTS

In the in-the-bag IOL group, nonsignificant differences of APE were found among the 6 formulae, while the Holladay 1, Hoffer Q, SRK/T, and SRK II all demonstrated a significant hyperopic shift of median PE value compared to the Hug formula (p < 0.05, all), and Holladay 1 and SRK II also showed a significant hyperopic shift of PE compared to the Khan formula (p < 0.05, both). Higher percentages of eyes with PE <1 D were found using Hoffer Q and SRK/T. In the sulcus-implanted group, the Holladay 1, Hoffer Q, and SRK/T had a significantly smaller median value of APE than the Hug and Khan formulae (p < 0.05, all), and the SRK II had a significantly smaller median value of APE than the Hug formula (p < 0.05), while Holladay 1 had the lowest value of APE. Higher percentages of eyes within PE <1 D were found using Holladay 1, Hoffer Q, and SRK/T, while the highest one was SRK/T. Significantly larger hyperopic shifts of median PE value using all the 6 formulae were found in eyes with sulcus-implanted IOL than eyes with in-the-bag implanted IOL (p < 0.05, all). In the eyes of with in-the-bag implanted IOL, the Hug and Khan formulae had significantly smaller APE values when compared with the eyes with sulcus-implanted IOL (p < 0.05, both).

CONCLUSIONS

Whether IOL was in the bag or implanted in the sulcus, almost all the formulae showed hyperopic shift, SRK/T showed the best accuracy. Biometry-based formulae were superior to AR-based formulae in accuracy of IOL power calculation, especially when IOL was implanted in the sulcus. In-the-bag IOL implantation should always be with higher priorities, especially when using AR-based formulae in IOL power calculation.

Accuracy of formulae for secondary intraocular lens power calculations in pediatric aphakia

Purpose

To compare the accuracy of axial length vergence formulas versus refractive vergence formulas for secondary intraocular lens (IOL) implantation in pediatric aphakia.

Methods

This retrospective comparative study, evaluated 31 eyes of 31 patients aged ≤3.5 years, who had undergone secondary IOL implantation. The median absolute error (MedAE) was compared between axial length vergence formulas (Hoffer Q, Holladay I, SRK II, and SRK/T) and refractive vergence formulas (Lanchulev, Holladay R, Mackool, and Khan) as well as between formulas within the same vergence.

Results

There was a significant difference (P = 0.010) between MedAE for axial length vergence formulas [1.19 Diopter(D)] and MedAE for refractive vergence formulas (2.48 D). The MedAE of axial length vergence formulas were comparable as to Hoffer (1.59 D), Holladay (1.27 D), SRK/T (1.23 D), and SRK II (1.30 D). Among refractive vergence formulas, Lanchulev (5.00 D) and Holladay R (2.51 D) had significantly larger MedAE as compared to Khan (2.06 D) and Mackool (2.15 D).

Conclusion

Axial length vergence formulas performed significantly better than refractive vergence formulas; however, axial length vergence formulas were comparable within the same vergence.

Pediatric cataract: challenges and future directions

Cataract is a significant cause of visual disability in the pediatric population worldwide and can significantly impact the neurobiological development of a child. Early diagnosis and prompt surgical intervention is critical to prevent irreversible amblyopia. Thorough ocular evaluation, including the onset, duration, and morphology of a cataract, is essential to determine the timing for surgical intervention. Detailed assessment of the general health of the child, preferably in conjunction with a pediatrician, is helpful to rule out any associated systemic condition. Although pediatric cataracts have a diverse etiology, with the majority being idiopathic, genetic counseling and molecular testing should be undertaken with the help of a genetic counselor and/or geneticist in cases of hereditary cataracts. Advancement in surgical techniques and methods of optical rehabilitation has substantially improved the functional and anatomic outcomes of pediatric cataract surgeries in recent years. However, the phenomenon of refractive growth and the process of emmetropization have continued to puzzle pediatric ophthalmologists and highlight the need for future prospective studies. Posterior capsule opacification and secondary glaucoma are still the major postoperative complications necessitating long-term surveillance in children undergoing cataract surgery early in life. Successful management of pediatric cataracts depends on individualized care and experienced teamwork. We reviewed the etiology, preoperative evaluation including biometry, choice of intraocular lens, surgical techniques, and recent developments in the field of childhood cataract.

Axial length measurement techniques in pediatric eyes with cataract

Globe axial length (AL) in children is commonly measured using either contact or immersion technique. Office measurement of AL can be difficult in young children and infants and must often be done under anesthesia in an eye that is unable to cooperate with precise fixation and centration. Contact A-scan measurements yield shorter AL, on average, than immersion A-scan measurements in pediatric eyes. This difference is mainly the result of the anterior chamber depth rather than the lens thickness value. During intraocular lens power calculation, if globe axial length is measured by the contact technique, it will result in the use of an average 1-D stronger IOL power than is actually required. This can lead to induced myopia in the postoperative refraction. In our studied patients, there was a significant difference in prediction error between contact A-scan biometry and immersion A-scan biometry. The immersion A-scan technique is recommended for pediatric IOL power calculation. We also provide a review of biometry in pediatric eyes. The overall mean AL of pediatric cataractous eyes is significantly different than the mean AL of non cataractous eyes. More importantly, the standard deviation is higher in eyes with cataract than in those without. Three phases of eye growth in children have been documented: A rapid, postnatal phase from birth to 6 months of age, followed by a slower, infantile phase from 6 to 18 months of age, and finally a slow, juvenile phase from 18 months forward. In our study, girls had shorter ALs than boys and African-American subjects had longer ALs than Caucasians. Eyes with unilateral cataract had shorter ALs than eyes with bilateral cataract during the earlier years, but had longer ALs during later childhood.

Refractive outcomes and prediction error following secondary intraocular lens implantation in children: a decade-long analysis

AIM

To evaluate the refractive outcomes, prediction error (PE) and factors affecting PE in children with aphakia following congenital cataract surgery undergoing secondary intraocular lens (IOL) implantation.

METHODS

We analysed the records of children less than 16 years old who underwent secondary IOL implantation for aphakia following congenital cataract surgery. PE and absolute PE for each case calculated 3 months following secondary IOL implantation were analysed. Multiple regression analysis was performed to determine the relationship between age at secondary IOL implantation, axial length, keratometry readings and PE.

RESULTS

174 eyes of 104 children were analysed. Mean age at surgery was 6.08±3.75 years. The mean PE was 1.65±2.46 dioptres (D) (range -3.25 to 7.5 D) and mean absolute PE was 2.15±1.68 D (range 0-7.5 D) at 3 months. There was a statistically significant difference in absolute PE between eyes in which IOL calculation was performed using IOL master (1.80±1.40 D) versus IOL calculation under general anaesthesia with contact method (2.43±1.83 D), p=0.01. Multiple regression analysis revealed an inverse relationship between age at secondary IOL implantation and mean absolute PE (p=0.01).

CONCLUSIONS

IOL power calculation with SRK II formula with sulcus placement of IOL gives favourable refractive outcomes. Though age-based refraction is targeted, a significant PE may be expected.