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

Clinical update in nanophthalmos: Features, diseases and complications associated

Nanophthalmos is a rare congenital condition of the eyeball that is characterised by a smaller size of the anterior and posterior segments without associated ocular malformations. Typical features that have traditionally been described in these eyes are short axial length, thickened sclera, cornea with a smaller diameter, narrow anterior chamber, and an increased lens to globe volume ratio. However, at present, there is still a lack of recognised diagnostic criteria for nanophthalmos and a classification of its severity. Its clinical relevance stems from the increased risk of multiple ocular conditions, such as high hyperopia, amblyopia, angle-closure glaucoma, retinal detachment, and cataracts. Likewise, in relation to surgery in these eyes, there are particularities in cataract and glaucoma surgery and with a greater risk of associated intra- and postoperative complications. In this way, the treatment of nanophthalmos focuses on controlling the associated eye conditions and reducing and controlling surgical complications. This review aims to update what has been published in recent years regarding nanophthalmos.

Comparison of intraocular lens power calculation formulas in patients with a history of acute primary angle-closure attack

BACKGROUND

To compare the accuracy of nine intraocular lens (IOL) power calculation formulas, including three traditional formulas (SRK/T, Haigis, and Hoffer Q) and six new-generation formulas (Barrett Universal II [BUII], Hill-Radial Basis Function [RBF] 3.0, Kane, Emmetropia verifying optical [EVO], Ladas Super, and Pearl-DGS) in patients who underwent cataract surgery after acute primary angle closure (APAC).

METHODS

In this retrospective cross-sectional study, 44 eyes of 44 patients (APAC) and 60 eyes of 60 patients (control) were included. We compared the mean absolute error, median absolute error (MedAE), and prediction error after surgery. Subgroup analyses were performed on whether axial length (AL) or preoperative laser peripheral iridotomy affected the postoperative refractive outcomes.

RESULTS

In the APAC group, all formulas showed higher MedAE and more myopic shift than the control group (all P < 0.05). In APAC eyes with AL ≥ 22 mm, there were no differences in MedAEs according to the IOL formulas; however, in APAC eyes with AL < 22 mm, Haigis (0.49 D) showed lower MedAE than SRK/T (0.82 D) (P = 0.036) and Hill-RBF 3.0 (0.54 D) showed lower MedAE than SRK/T (0.82 D), Hoffer Q (0.75 D) or Kane (0.83 D) (P = 0.045, 0.036 and 0.027, respectively). Pearl-DGS (0.63 D) showed lower MedAE than Hoffer Q (0.75 D) and Kane (0.83 D) (P = 0.045 and 0.036, respectively). Haigis and Hill-RBF 3.0 showed the highest percentage (46.7%) of eyes with PE within ± 0.5 D in APAC eyes with AL < 22 mm. Iridectomized eyes did not show superior precision than the non-iridotomized eyes in the APAC group.

CONCLUSIONS

Refractive errors in the APAC group were more myopic than those in the control group. Haigis and Hill-RBF 3.0 showed high precision in the eyes with AL < 22 mm in the APAC group.

Accuracy of 10 IOL power calculation formulas in 100 short eyes (≤ 22 mm)

BACKGROUND

To assess and compare the accuracy of 10 intraocular lens (IOL) power calculation formulas after cataract surgery in eyes with an axial length (AL) shorter than or equal to 22.00 mm.

METHODS

A retrospective case series included 100 eyes with an AL ≤ 22.00 mm that underwent uneventful cataract surgery. The refractive prediction error (PE) was calculated using 10 different IOL power calculation formulas: Barrett Universal II, EVO 2.0, Haigis, Hill RBF 2.0, Hoffer Q, Holladay 1 and 2, Kane, SRK/T and SuperLadas. The median absolute prediction error (MedAE ± SD) and mean absolute prediction error (MAE ± SD) were calculated after adjusting the mean prediction error (ME) to 0.

RESULTS

Hoffer Q obtained the lowest MedAE (0.292 D) after adjusting the ME to 0, followed very closely by EVO 2.0 (0.298 D) and Kane (0.300 D). EVO 2.0 and Kane obtained both the lowest MAE after adjusting the ME to 0 (0.386). Differences in MAE among the different formulas were not statistically significant (p > 0.05).

CONCLUSIONS

Our study reflects a tendency of the EVO 2.0 formula and the Kane formula along with the older Hoffer Q formula, to predict more accurately the refractive outcomes in short eyes that undergo cataract phacoemulsification surgery compared to the other formulas, despite this difference could not be statistically proved.

Comparison of the accuracy of nine intraocular lens power calculation formulas using partial coherence interferometry

Cataract surgery is the most performed procedure in the world. To achieve the target refraction, several intraocular lens (IOL) power calculation formulas have been developed to improve the accuracy of IOL power predictions. We compared the accuracy of 9 IOL power calculation formulas (SRK/T, Hoffer Q, Holladay 1, Haigis, Barrett Universal II, Kane, EVO 2.0, Ladas Super formula and Hill-RBF 3.0) using partial coherence interferometry (PCI). We collected data from patients who underwent uncomplicated cataract surgery with implantation of 1 of 3 IOL types currently used in our center. All preoperative biometric measurements were performed using PCI. Prediction errors (PE) were deduced from refractive outcomes evaluated 3 months after surgery. The mean prediction error (ME), mean absolute prediction error (MAE), median absolute prediction error (MedAE), and standard deviation of prediction error (SD) were calculated, as well as the percentage of eyes with a PE within ± 0.25, ± 0.50, ± 0.75 and ± 1.00D for each formula. We included 126 eyes of 126 patients. Kane achieved the lowest MAE and SD across the entire sample as well as the highest percentage of PE within ± 0.50D and was shown to be more accurate than Haigis and Hoffer Q (P<001). For an axial length of more than 26.0mm, EVO 2.0 and Barrett obtained the lowest MAEs, with EVO 2.0 and Kane showing a higher percentage of prediction at ±0.50D compared to old generation formulas except for SRK/T (P=04). All investigated formulas achieved good results; there was a tendency toward better outcomes with new generation formulas, especially in atypical eyes.

Accuracy of intraocular lens power calculation formulae in short eyes: A systematic review and meta-analysis

This review article attempts to evaluate the accuracy of intraocular lens power calculation formulae in short eyes. A thorough literature search of PubMed, Embase, Cochrane Library, Science Direct, Scopus, and Web of Science databases was conducted for articles published over the past 21 years, up to July 2021. The mean absolute error was compared by using weighted mean difference, whereas odds ratio was used for comparing the percentage of eyes with prediction error within ±0.50 diopter (D) and ±1.0 D of target refraction. Statistical heterogeneity among studies was analyzed by using Chi-square test and I² test. Fifteen studies including 2,395 eyes and 11 formulae (Barrett Universal II, Full Monte method, Haigis, Hill-RBF, Hoffer Q, Holladay 1, Holladay 2, Olsen, Super formula, SRK/T, and T2) were included. Although the mean absolute error (MAE) of Barrett Universal II was found to be the lowest, there was no statistically significant difference in any of the comparisons. The median absolute error (MedAE) of Barrett Universal II was the lowest (0.260). Holladay 1 and Hill-RBF had the highest percentage of eyes within ±0.50 D and ±1.0 D of target refraction, respectively. Yet their comparison with the rest of the formulae did not yield statistically significant results. Thus, to conclude, in the present meta-analysis, although lowest MAE and MedAE were found for Barrett Universal II and the highest percentage of eyes within ±0.50 D and ±1.0 D of target refraction was found for Holladay 1 and Hill-RBF, respectively, none of the formulae was found to be statistically superior over the other in eyes with short axial length.

Comparing the accuracy of new intraocular lens power calculation formulae in short eyes after cataract surgery: a systematic review and meta-analysis

PURPOSE

Calculating the intraocular lens (IOL) power in short eyes for cataract surgery has been a challenge. A meta-analysis was conducted to identify, among several classic and new IOL power calculation formulae, which obtains the best accuracy.

METHODS

All studies aiming at comparing the accuracy of IOL power calculation formulae in short eyes were searched up in the databases of PubMed, EMBASE, Web of Science and the Cochrane library from Jan. 2011 to Mar. 2021. Primary outcomes were the percentages of eyes with a refractive prediction error in ± 0.25D, ± 0.5D and ± 1.0D.

RESULTS

Totally 1,476 eyes from 14 studies were enrolled in comparison of 13 formulae (Barrett Universal II, Castrop, Haigis, Hoffer Q, Holladay1, Holladay2, Kane, Ladas Super Formula, Okulix, Olsen, Pearl-DGS, SRK/T and T2). Pearl-DGS had the highest percentage within ± 0.25D. In the ± 0.5D range, Pearl-DGS obtained the highest percentage again, and it was significantly higher than Barrett Universal II, Haigis, Hoffer Q, Holladay1, Holladay2 and Olsen (P = 0.001, P = 0.02, P = 0.0003, P = 0.01, P = 0.007, P = 0.05, respectively). In the ± 1.0D range, Okulix possessed the highest percentage, and it was significantly higher than Barrett Universal II, Castrop, Hoffer Q and Holladay2 (P = 0.0005, P = 0.03, P = 0.003, P = 0.02, respectively).

CONCLUSION

The new generation formulae, based on artificial intelligence or ray-tracing principle, are more accurate than the convergence formulae. Pearl-DGS and Okulix are the two most accurate formulae in short eyes.

Cataract Surgery in Short Eyes, Including Nanophthalmos: Visual Outcomes, Complications and Refractive Results

Background

To report the visual outcomes, complications and refractive results of phacoemulsification surgery and intraocular lens implantation in a large series of adult patients with short and nanophthalmic eyes.

Methods

The records of all patients with axial length <21.0 mm undergoing phacoemulsification with intraocular lens implantation at an adult teaching hospital were retrospectively reviewed. The main outcome measures were corrected distance visual acuity and refraction at 90 days after surgery and intra- and postoperative complications occurring during the follow-up period.

Results

A total of 71 eyes of 51 patients (median age 71 years, interquartile range 62–75.5) were included. Surgery resulted in an improvement in corrected distance visual acuity in 53 eyes (74.6%) (95% confidence interval, logMAR 0.11–0.29) and was logMAR 0.30 or better in 47 eyes (66.2%). Worsening of corrected distance visual acuity occurred in 9 eyes (12.7%). Median postoperative refractive error was −0.75 dioptres. SRK/T and Kane formula were more accurate in predicting postoperative refraction than Barrett Universal II and Hoffer Q when based on mean absolute error (P < 0.005). Complications occurred in 18 eyes (25.4%). The most frequent complications were iris prolapse, Descemet’s membrane and/or endothelial trauma, transient severe corneal edema and cystoid macular edema. There was no statistically significant difference in complication rates between senior surgeons and senior trainees (P = 0.66).

Conclusion

Cataract surgery in short and nanophthalmic eyes is challenging with a higher complication rate than routine cataract surgery, but frequently results in good visual outcomes. Postoperative refractive outcomes are more difficult to predict in this cohort.

Accuracy of intraocular lens power calculation in primary angle-closure disease: comparison of 7 formulas

PURPOSE

To assess the accuracy of intraocular lens power calculation formulas Barrett Universal II (BUII), Hill-Radial Basis Function (RBF) 3.0, Kane, Ladas Super Formula (LSF), Haigis, Hoffer Q, and SRK/T in primary angle-closure disease (PACD).

METHODS

A total of 129 PACD eyes were enrolled. Prediction refraction was calculated for each formula and compared with actual refraction. Accuracy was determined by formula performance index (FPI), median absolute error (MedAE) and percentage of eyes with a prediction error (PE) within ± 0.50D. Subgroup analysis was performed according to axial length (AL).

RESULTS

Overall, FPI was ranked as follows: Kane (0.067), RBF 3.0 (0.064), Haigis (0.062), SRK/T (0.060), BUII (0.058), Hoffer Q (0.055), and LSF (0.049). Kane got the highest (71.3%) percentage of eyes with PE within ± 0.50 D. In medium AL eyes (22 mm < AL ≤ 25 mm), FPI ranked the same as in total group. MedAEs were equal across all formulas (P = 0.121). In short eyes (AL ≤ 22 mm), FPI was Kane (0.055), RBF 3.0 (0.050), SRK/T (0.050), Haigis (0.049), BUII (0.047), Hoffer Q (0.045), and LSF (0.033). MedAEs were significantly different across all formulas (P = 0.033). Haigis showed the lowest MedAE (0.35 D), Haigis and Kane got the highest percentage (63.6%) of eyes with PE within ± 0.50 D.

CONCLUSION

Kane outperformed in total PACD eyes; RBF 3.0, Haigis, and SRK/T achieved satisfying performance. When dealing with PACD eyes shorter than 22 mm, Kane achieved the best accuracy. RBF 3.0, SRK/T, Haigis, and BUII achieved comparable outcomes. No formula showed superiority over others for medium AL PACD eyes.

Accuracy of intraocular lens calculation formulas in cataract patients with steep corneal curvature

OBJECTIVE

To compare the accuracy of five kinds of intraocular lens calculation formulas (SRK/T, Haigis, Hoffer Q, Holladay and Barrett Universal Ⅱ) in cataract patients with steep curvature cornea ≥ 46.0 diopters.

METHODS

This is a retrospective study of cataract phacoemulsification combined with intraocular lens implantation in patients with steep curvature cornea (corneal curvature ≥ 46D). The refractive prediction errors of IOL power calculation formulas (SRK/T, Haigis, Holladay, Hoffer Q, and Barrett Universal II) using User Group for Laser Interference Biometry (ULIB) constants were evaluated and compared. Objective refraction results were assessed at one month postoperatively. According to axial length (AL), all patients were divided into three groups: short AL group (<22mm), normal AL group (>22 to ≤24.5mm) and long AL group (>24.5mm). Calculate the refractive error and absolute refractive error (AE) between the actual postoperative refractive power and the predicted postoperative refractive power. The covariance analysis was used for the comparison of five formulas in each group. The correlation between the absolute refractive error and AL from every formula were analyzed by Pearson correlation test, respectively.

RESULT

Total 112 eyes of 83 cataract patients with steep curvature cornea were collected. The anterior chamber depth (ACD) was a covariate in the short AL group in the covariance analysis of absolute refractive error (P<0.001). The SRK/T and Holladay formula had the lowest mean absolute error (MAE) (0.47D), there were statistically significant differences in MAE between the five formulas for short AL group (P = 0.024). The anterior chamber depth had no significant correlation in the five calculation formulas in the normal AL group and long AL group (P = 0.521, P = 0.609 respectively). In the normal AL group, there was no significant difference in MAE between the five calculation formulas (P = 0.609). In the long AL group, Barrett Universal II formula had the lowest MAE (0.35), and there were statistically significant differences in MAE between the five formulas (P = 0.012). Over the entire AL range, the Barrett Universal II formula had the lowest MAE and the highest percentage of eyes within ± 0.50 D, ± 1.00 D, and ± 1.50 D (69.6%, 93.8%, and 98.2% respectively).

CONCLUSION

Compared to SRK/T, Haigis, Hoffer Q, and Holladay, Barrett Universal Ⅱ formula is more accurate in predicting the IOL power in the cataract patients with steep curvature cornea ≥ 46.0 diopters.

Bilateral implantation of +56 and +58 diopter custom-made intraocular lenses in patient with extreme nanophthalmos

Purpose

To present the case of a 60-year-old patient with severe nanophthalmic eyes, who underwent cataract surgery with a bilateral implantation of custom-made high-power intraocular lenses (IOLs).

Observations

The axial length was 14.94 and 15.05 mm of the right and the left eye, respectively. The preoperative corrected distance visual acuity (CDVA) was +0.46 logMAR (20/63) in the right eye and +0.58 logMAR (20/80) in the left eye with rigid contact lenses of +17.5 D bilaterally. The calculated IOL power for emmetropia with different formulas ranged from +55.28 to +70.09 D. The IOL power selection was based on the average value from four formulas (Haigis, Holladay 1, Holladay 2, SRK/T) with the target refraction of emmetropia. Custom-made +56.0 and + 58.0 D Aspira-aAY IOLs (HumanOptics AG, Erlangen, Germany) were implanted without any complications. The postoperative CDVA was +0.40 logMAR (20/50) and +0.60 logMAR (20/80). The manifest refraction spherical equivalents were +0.625 D and −0.375 D.

Conclusions and importance

Even in eyes with the axial length of only 15 mm, cataract surgery can be successfully performed after adequate preparation. High-power customized IOLs allow complete correction of hyperopia but caution is required with the results from different IOL power calculation formulas, which can be misleading.

Accuracy of common IOL power formulas in 611 eyes based on axial length and corneal power ranges

AIMS

To provide clinical guidance on the use of intraocular lens (IOL) power calculation formulas according to the biometric parameters.

METHODS

611 eyes that underwent cataract surgery were retrospectively analysed in subgroups according to the axial length (AL) and corneal power (K). The predicted residual refractive error was calculated and compared to evaluate the accuracy of the following formulas: Haigis, Hoffer Q, Holladay 1 and SRK/T. Furthermore, the percentages of eyes with ≤±0.25, ≤±0.5 and 1 dioptres (D) of the prediction error were recorded.

RESULTS

The Haigis formula showed the highest percentage of cases with ≤0.5 D in eyes with a short AL and steep K (90%), average AL and steep cornea (73.2%) but also in long eyes with a flat and average K (65% and 72.7%, respectively). The Hoffer Q formula delivered the lowest median absolute error (MedAE) in short eyes with an average K (0.30 D) and Holladay 1 in short eyes with a steep K (Holladay 1 0.24 D). SRK/T presented the highest percentage of cases with ≤0.5 D in average long eyes with a flat and average K (80.5% and 68.1%, respectively) and the lowest MedAE in long eyes with an average K (0.29 D).

CONCLUSION

Overall, the Haigis formula shows accurate results in most subgroups. However, attention must be paid to the axial eye length as well as the corneal power when choosing the appropriate formula to calculate an IOL power, especially in eyes with an unusual biometry.

Accuracy of eight intraocular lens power calculation formulas for segmented multifocal intraocular lens

AIM

To evaluate the accuracy of eight different intraocular lens (IOL) power calculation formulas for a segmented multifocal IOL.

METHODS

A total of 53 eyes of 41 adult cataract patients who underwent phacoemulsification and implantation with the SBL-3 segmented multifocal IOL between January 1, 2017 and January 31, 2019 were included in this retrospective study. Preoperative biometry measurements were obtained using an IOL Master. Manifest refraction was performed at least 4wk postoperatively. Accuracy of the eight formulas [Barrett Universal II, Emmetropia Verifying Optical (EVO), Haigis, Hill-RBF 2.0, Hoffer Q, Holladay 1, Kane, and SRK/T] was analyzed.

RESULTS

Using current lens constants, all formulas exhibited errors of slight myopic shift in refractive prediction. The Barrett Universal II formula had a significantly lower median absolute error (MedAE) than did Holladay 1 (P=0.02), Kane (P=0.001) and Hill-RBF 2.0 (P<0.001) formulas. The Haigis formula had a lower MedAE value than did the Hill-RBF 2.0 formula (P=0.005). Differences in MedAE values among SRK/T, EVO and Hoffer Q formulas were not significant. After optimizing lens constants, the MedAE values of all formulas were reduced; significant changes were noted for EVO (P=0.022), Haigis (P=0.048), Hill-RBF 2.0 (P=0.014), Holladay 1 (P=0.045) and Kane (P=0.022) formulas. All formulas performed equally well after optimization of lens constants (P=0.203).

CONCLUSION

All eight formulas tend to result in a myopic shift when using current lens constants. Optimized lens constants improve the accuracy of these formulas among adult Chinese patients.

Intraocular Lens Power Formulas, Biometry, and Intraoperative Aberrometry: A Review

The refractive outcome of cataract surgery is influenced by the choice of intraocular lens (IOL) power formula and the accuracy of the various devices used to measure the eye (including intraoperative aberrometry [IA]). This review aimed to cover the breadth of literature over the previous 10 years, focusing on 3 main questions: (1) What IOL power formulas currently are available and which is the most accurate? (2) What biometry devices are available, do the measurements they obtain differ from one another, and will this cause a clinically significant change in IOL power selection? and (3) Does IA improve refractive outcomes? A literature review was performed by searching the PubMed database for articles on each of these topics that identified 1313 articles, of which 166 were included in the review. For IOL power formulas, the Kane formula was the most accurate formula over the entire axial length (AL) spectrum and in both the short eye (AL, ≤22.0 mm) and long eye (AL, ≥26.0 mm) subgroups. Other formulas that performed well in the short-eye subgroup were the Olsen (4-factor), Haigis, and Hill-radial basis function (RBF) 1.0. In the long-eye group, the other formulas that performed well included the Barrett Universal II (BUII), Olsen (4-factor), or Holladay 1 with Wang-Koch adjustment. All biometry devices delivered highly reproducible measurements, and most comparative studies showed little difference in the average measures for all the biometric variables between devices. The differences seen resulted in minimal clinically significant effects on IOL power selection. The main difference found between devices was the ability to measure successfully through dense cataracts, with swept-source OCT-based machines performing better than partial coherence interferometry and optical low-coherence reflectometry devices. Intraoperative aberrometry generally improved outcomes for spherical and toric IOLs in eyes both with and without prior refractive surgery when the BUII and Hill-RBF, Barrett toric calculator, or Barrett True-K formulas were not used. When they were used, IA did not result in better outcomes.

[Calculation of intraocular lens power in surgical treatment of extreme hyperopia]

Accuracy of calculation of the intraocular lens (IOL) power in eyes with short axial length is inferior to one in emmetropic eyes. Most studies focus on relatively standard eyes.

PURPOSE

To assess the accuracy of power calculation for IOL used to correct extreme hyperopia and to compare available formulas based on their predictive capacity.

MATERIAL AND METHODS

Results of 13 implantations involving IOLs of at least 40 Diopters (D) in power were retrospectively evaluated. IOL power was calculated using five formulas: Haigis, Hoffer Q, HolladayI, SRKII, SRK/T. Mean numerical refractive prediction error (RPE) and mean absolute refractive prediction error (ARPE) were calculated. Mean and median ARPE were computed after optimizing the A₀ constant. Proportions of eyes within certain RPE limits were compared between the formulas.

RESULTS

Mean RPE ranged from 1.43 to 11.71 D before adjustment and from 1.08 to 5.34 D after adjustment (p<0.0001). Haigis formula produced the least RPE, and SRKII - the most. Pairwise comparison by mean ARPE after adjustment revealed no statistically significant difference between Haigis and Hoffer Q formulas. Comparison of formulas by percentage of eyes with minimal RPE identified Haigis and Hoffer Q as the most accurate, while the difference between the two was not statistically significant. The difference between the most accurate formulas (Haigis and Hoffer Q) and the least accurate (SRKII) was statistically significant.

CONCLUSION

In eyes with extremely short anterior-posterior axis, prediction errors in IOL power calculations are relatively frequent (only 31-46% of eyes are within ±0.5 D) and warrant reduction. Among the evaluated formulas, Haigis and Hoffer Q are the most accurate. In order to improve the accuracy of IOL power calculations, it is necessary to employ personalized constants.

A Randomized Controlled Trial Comparing Outcomes of Cataract Surgery in Nanophthalmos With and Without Prophylactic Sclerostomy

PURPOSE

To prospectively evaluate visual outcomes and complications during and after cataract surgery with or without prophylactic sclerostomy in nanophthalmic eyes with visually significant cataract.

STUDY DESIGN

Randomized controlled trial.

METHODS

Sixty nanophthalmic eyes of 60 patients with visually significant cataract were randomly assigned to cataract surgery alone (control group, n = 31) or cataract surgery with concomitant prophylactic sclerostomy (sclerostomy group, n = 29). Surgery was performed using phacoemulsification or manual small-incision cataract surgery (SICS) based on the LOCS III grading score. Group differences in intraoperative and postoperative complications were analyzed and risk factors assessed.

RESULTS

Fewer complications were noted in eyes receiving sclerostomy (5/29, 17.2%) as compared to control group eyes (12/31, 38.7%), though differences were marginally significant (P = .065). Four control group, but no sclerostomy group, eyes developed postoperative uveal effusions (P = .04). In multivariable models, sclerostomy decreased the odds of an intraoperative or postoperative complication by 80% (odds ratio [OR] = 0.2, 95% confidence interval [CI] = 0.04-0.92, P = .039); SICS was associated with a significantly higher risk of complications as compared to phacoemulsification (OR = 5.95, 95% CI = 1.49-23.73, P = .012), while high preoperative intraocular pressure (OR = 4.54, 95% CI = 0.99-20.9, P = .052) and greater lens thickness (OR = 3.38, 95% CI = 0.88-12.91, P = .075) demonstrated a marginally significant association.

CONCLUSIONS

Cataract surgery in eyes with nanophthalmos is associated with a high risk for vision-threatening complications. Performing a simultaneous prophylactic sclerostomy with cataract surgery reduces complication rates, particularly uveal effusions. Cataract surgery at earlier stages by phacoemulsification may be more beneficial than undergoing manual SICS.

Cataract Surgery with a New Fluidics Control Phacoemulsification System in Nanophthalmic Eyes

Purpose

To report visual outcomes and complications after cataract surgery in nanophthalmic eyes with a phacoemulsification system using the active fluidics control strategy.

Methods

This is a retrospective case series. All eyes with an axial length of less than 20 mm that underwent cataract surgery or refractive lens exchange using the Centurion Vision System (Alcon Laboratories Inc.) in Hong Kong Sanatorium and Hospital were evaluated. The visual acuity and intraoperative and postoperative complications were reported. Prior approval from the Hospital Research Committee has been granted.

Results

Five eyes of 3 patients were included. The mean follow-up period was 10.2 ± 5.3 months (range, 4–18). Two eyes (40%) had a one-line loss of corrected distance visual acuity. No uveal effusion and posterior capsular tear developed. An optic crack and haptic breakage in the intraocular lens developed in 1 eye (20%) and 2 eyes (40%), respectively. Additional surgeries to treat high postoperative intraocular pressure were required in 1 eye (20%).

Conclusion

The use of a new phacoemulsification system, which actively monitors and maintains the intraoperative pressure, facilitated anterior chamber stability during cataract surgery in nanophthalmic eyes. This minimized the risk of major complications related to unstable anterior chambers such as uveal effusion and posterior capsular tear. Development of intraoperative crack/breakage in a high-power intraocular lens was common.

Cataract surgery in the small eye

The surgical management of cataract in the small eye presents the ophthalmic surgeon with numerous challenges. An understanding of the anatomic classification in addition to a thorough preoperative assessment will help individualize each case and enable the surgeon to better prepare for the obstacles that might be encountered during surgery. Small eyes are especially challenging in terms of intraocular lens (IOL) calculations and possible current limitations of available IOL powers, which could necessitate alternative means of achieving emmetropia. Surgical strategies for minimizing complications and maximizing good outcomes can be developed from knowledge of the anatomic differences between various small-eye conditions and the pathologies that may be associated with each. A thorough understanding of the challenges inherent in these cases and the management of intraoperative and postoperative complications will ensure that surgeons approaching the correction of these eyes will achieve the best possible surgical results.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Performance of the SRK/T formula using A-Scan ultrasound biometry after phacoemulsification in eyes with short and long axial lengths

BACKGROUND

The SRK/T formula is one of the third generation IOL calculation formulas. The purpose of this study was to evaluate the performance of the SRK/T formula in predicting a target refraction ±1.0D in short and long eyes using ultrasound biometry after phacoemulsification.

METHODS

The present study was a retrospective analysis, which included 38 eyes with an AL < 22.0 mm (short AL), and 62 eyes ≥24.6 mm (long AL) that underwent uncomplicated phacoemulsification. Preoperative AL was measured by ultrasound biometry and SRK/T formula was used for IOL calculation. Three different IOLs were implanted in the capsular bag. The prediction error was defined as the difference between the achieved postoperative refraction, and attempted predicted target refraction. Statistical analysis was performed with SPSS V21.

RESULTS

In short ALs, the mean age was 65.13 ± 9.49 year, the mean AL was 21.55 ± 0.45 mm, the mean K1 and K2 were 45.76 ± 1.77D and 46.09 ± 1.61D, the mean IOL power was 23.96 ± 1.92D, the mean attempted (predicted) value was 0.07 ± 0.26D, the mean achieved value was 0.07 ± 0.63 D, the mean PE was 0.01 ± 0.60D, and the MAE was 0.51 ± 0.31D. A significant positive relationship with AL and K1, K2, IOL power and a strong negative relationship with PE and achieved postoperative was found. In long ALs, the mean age was 64.05 ± 7.31 year, the mean AL was 25.77 ± 1.64 mm, the mean K1 and K2 were 42.20 ± 1.57D and 42.17 ± 1.68D, the mean IOL power was 15.79 ± 5.17D, the mean attempted value was -0.434 ± 0.315D, the mean achieved value was -0.42 ± 0.96D, the mean PE was -0.004 ± 0.93D, the MAE was 0.68 ± 0.62D. A significant positive relationship with AL and K1, K2 and a significant positive relationship with PE and achieved value, otherwise a negative relationship with AL and IOL power was found. There was a little tendency towards hyperopic for short ALs and myopic for long ALs. The majority of eyes (94.74 %) for short ALs and (70.97 %) for long ALs were within ±1 D of the predicted refractive error. No significant relationship with PE and IOL types, AL, K1, K2, IOL power, and attempted value, besides with MAE and AL, K1, K2, age, attempted, achieved value were found in both groups.

CONCLUSION

The SRK/T formula performs well and shows good predictability in eyes with short and long axial lengths.

Mensurações do bulbo ocular e cálculo do poder dióptrico da lente intraocular em miniporcos

Objetivou-se com este trabalho determinar o poder dióptrico da lente intraocular (LIO) em miniporco e as dimensões do bulbo do olho. Foram utilizados 17 miniporcos, sadios, adultos, machos e fêmeas, com peso médio de 70kg. Em todos os olhos foram realizadas a ultrassonografia modo A, a ceratometria e a medida da distância limbo a limbo. O cálculo do poder dióptrico da LIO foi obtido utilizando-se as fórmulas Haigis, Hoffer Q, SRK/T, Holladay I e Holladay II e o software Holladay IOL Consultant(r). Na comparação entre o sexo e a lateralidade do olho, não houve diferença nas variáveis biométricas e poder da LIO. A aplicação das fórmulas (Haigis, Holladay II, Holladay I, SRK/T e Hoffer Q) possibilitou o cálculo do poder da LIO. A Holladay II, fórmula que melhor individualiza o bulbo do olho do miniporco, estima valor dióptrico ao redor de 41 D. Os miniporcos têm potencial como modelo experimental em oftalmologia, relacionado ao seu menor porte e à facilidade no manejo, especialmente em experimentos de longa duração.

Gender differences in biometry prediction error and intra-ocular lens power calculation formula

PURPOSE

To analyze changes over time in biometry prediction error (BPE) after cataract surgery with special reference to the impact of gender and the intra-ocular lens (IOL) calculation formula.

METHODS

About 65% of Swedish cataract surgery units participating in the outcome registration of the National Cataract Register (NCR) were included in this prospective register study. Data for planned and postoperative refraction and keratometry during the month of March 2004-2013 were analyzed, divided by gender. The newly introduced variables axial length and IOL calculation formula were analyzed for March 2013. Gender differences in BPE with correct sign (BPESign ) and absolute biometry prediction error (BPEAbs ) were compared for the Haigis' and Sanders-Retzlaff-Kraff T (SRK/T) formulas.

RESULTS

The BPEAbs decreased throughout the study period. In 2004-2006, the BPEAbs was larger in women than in men (p < 0.05), but this difference disappeared from 2007. For 2004 through 2009, the mean BPESign was -0.105 ± 0.79D for women, but -0.003 ± 0.73D for men. After 2009, this myopic error for women gradually diminished. The Haigis' formula performed better in women than the SRK/T formula (p < 0.001); the SRK/T formula rendered a BPESign similar to that from 2004 to 2009 in women. Women had steeper corneas and shorter axial lengths than men (p < 0.001).

CONCLUSION

The myopic BPE in women - associated with steeper corneas and shorter axial lengths - is decreasing, possibly owing to an increased use of the Haigis' formula. Using the Haigis' formula to a higher extent can potentially further reduce the BPEs after cataract surgery.

Gender differences in refractive prediction in refractive lens exchange surgery

PURPOSE

To compare the refractive outcomes after refractive lens exchange (RLE) surgery with regards to gender and intraocular lens (IOL) power calculation formula.

METHODS

A cohort of consecutive patients operated with bilateral same-day RLE surgery at a private eye clinic (n = 512) was studied. Target refraction was emmetropia in all cases and Haigis formula was used for all IOL power calculations. One month after surgery, subjective refraction was assessed and the absolute refractive prediction error (RPEAbs), as well as the refractive prediction error with correct signs (RPESign), was calculated, as were the refractive outcomes with the SRK/T formula.

RESULTS

For the whole cohort, the Haigis formula rendered a significantly smaller RPEAbs than the SRK/T formula (0.16 ± 0.26 D vs 0.32 ± 0.30 D; p&lt;0.001). No gender difference in RPEAbs was seen. A slight myopic error was seen with the SRK/T formula in women, and a slight hyperopic error in men (-0.06 ± 0.47 D vs + 0.16 ± 0.39 D; p&lt;0.001). No similar gender difference was seen with the Haigis formula (+0.05 ± 0.29 D vs +0.05 ± 0.31 D; p = NS). Axial length, anterior chamber depth, and corneal steepness differed significantly between the sexes.

CONCLUSIONS

The Haigis formula generally performed better in this RLE cohort. The SRK/T formula generates a small myopic error in women and a hyperopic error in men, associated with flatter corneas, longer axial lengths, and deeper anterior chambers in the latter.

Predictability of intraocular lens power calculation formulae in infantile eyes with unilateral congenital cataract: results from the Infant Aphakia Treatment Study

PURPOSE

To compare accuracy of intraocular lens (IOL) power calculation formulae in infantile eyes with primary IOL implantation.

DESIGN

Comparative case series.

METHODS

The Hoffer Q, Holladay 1, Holladay 2, Sanders-Retzlaff-Kraff (SRK) II, and Sanders-Retzlaff-Kraff theoretic (SRK/T) formulae were used to calculate predicted postoperative refraction for eyes that received primary IOL implantation in the Infant Aphakia Treatment Study. The protocol targeted postoperative hyperopia of +6.0 or +8.0 diopters (D). Eyes were excluded for invalid biometry, lack of refractive data at the specified postoperative visit, diagnosis of glaucoma or suspected glaucoma, or sulcus IOL placement. Actual refraction 1 month after surgery was converted to spherical equivalent and prediction error (predicted refraction - actual refraction) was calculated. Baseline characteristics were analyzed for effect on prediction error for each formula. The main outcome measure was absolute prediction error.

RESULTS

Forty-three eyes were studied; mean axial length was 18.1 ± 1.1 mm (in 23 eyes, it was <18.0 mm). Average age at surgery was 2.5 ± 1.5 months. Holladay 1 showed the lowest median absolute prediction error (1.2 D); a paired comparison of medians showed clinically similar results using the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Comparison of the mean absolute prediction error showed the lowest values using the SRK/T formula (1.4 ± 1.1 D), followed by the Holladay 1 formula (1.7 ± 1.3 D). Calculations with an optimized constant showed the lowest values and no significant difference between the Holladay 1 and SRK/T formulae (median difference, 0.3 D). Eyes with globe AL of less than 18 mm had the largest mean and median prediction error and absolute prediction error, regardless of the formula used.

CONCLUSIONS

The Holladay 1 and SRK/T formulae gave equally good results and had the best predictive value for infant eyes.