Improved prediction of intraocular lens power using partial coherence interferometry

Accuracy of 11 intraocular lens calculation formulas in shallow anterior chamber eyes

PURPOSE

To evaluate the performance of intraocular lens (IOL) calculation formulas and the effect of anterior chamber depth (ACD), axial length (AL) and lens thickness (LT) on the prediction accuracy in shallow ACD eyes.

METHODS

This retrospective, consecutive case-series study included 648 eyes of 648 patients with an ACD < 3.0 mm who underwent phacoemulsification and IOL implantation. Eleven formulas were evaluated: Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, Hill-Radial Basis Function (RBF) 3.0, Hoffer QST, Kane, Olsen, Pearl-DGS and traditional formulas (Haigis, Hoffer Q, Holladay 1 and SRK/T). Subgroup analysis was performed based on ACD, AL and LT.

RESULTS

Overall, the Hoffer QST and Kane showed no systematic bias. The Kane, EVO 2.0, Hill-RBF 3.0 and Hoffer QST had relatively lower mean absolute error and higher percentages of prediction error within ±0.5 D. For the ACD of 2.5-3.0 mm and AL < 22.0 mm subgroup, the Pearl-DGS exhibited the lowest MAE (0.45 D) and MedAE (0.41 D). Most formulas had a significant myopic bias (-0.43 to -0.18 D, p < 0.05) in the LT < 4.3 mm subgroup and a significant hyperopic bias (0.09-0.29 D, p < 0.05) in the LT ≥ 5.1 mm subgroup.

CONCLUSION

The Kane and Hoffer QST were recommended for shallow ACD eyes. In eyes with an ACD between 2.5 and 3.0 mm and a short AL, the Pearl-DGS showed excellent performance. Clinicians need to fine-tune the target refraction according to LT in shallow ACD eyes.

Current Concepts and Recent Updates of Optical Biometry- A Comprehensive Review

One of the most recent advancements in the field of cataract surgery is optical biometry. With the advent of optical biometry ocular measurements are now simpler, quicker, and more precise. The devices have made intraocular lens (IOL) power calculations easier in difficult situations too, such as in cases with extremes of axial lengths, silicone filled eyes, cataract surgery in post-keratoplasty eyes, post Laser-Assisted in Situ Keratomileusis (LASIK) eyes, etc. The gold standard for IOL power calculation in the present day is by the use of optical biometry devices. The anatomical measurements by these devices are highly precise and because of these measurements and the incorporation of various IOL power calculation formulas the optical biometry devices give the accurate power and the post-operative visual outcome is highly satisfactory among the patients. The growing use of these devices has made cataract the most commonly performed refractive surgical procedure nowadays. In the current scenario, optical biometry has widespread acceptance in almost all countries and has many advantages over ultrasound or immersion biometry. Cataract surgeons can obtain easy and reliable measurements from these devices. Refractive surprises have also decreased considerably with their use. This article will comprehensively review the principles of the various optical biometry devices, the parameters used in each of the devices, the advantages and disadvantages, and add more like what all this article will add.

Repeatability and comparability of a new swept-source optical coherence tomographer in optical biometry

PURPOSE

To evaluate the reproducibility in the measurement of ocular biometric parameters using a new swept-source optical coherence tomographer and its comparability with an optical low coherence reflectometry biometer.

DESIGN

An observational, descriptive, cross-sectional study.

METHODS

45 right eyes of 45 patients diagnosed with cataract were included. Three successive biometric measurements with Anterion and one with Lenstar LS900 were performed on each patient. The following variables were collected: axial length (AXL), anterior chamber depth (ACD), flat K (K1), steep K (K2), central corneal thickness (CCT), lens thickness (LT) and white-to-white distance (WTW). The intrasubject standard deviation (S_w) and the coefficient of Pearson "R" were calculated in order to assess the repeatability. The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) were obtained to evaluate the comparability between devices. A Bland-Altman plot was performed for each variable.

RESULTS

The coefficient of Pearson was excellent and statistically significant in the evaluation of the repeatability in all the variables. The highest values were 0.987 (AXL), 0.983 (CCT) and 0.942 (ACD). There were no statically significant differences between repeated measurements with Anterion in all the parameters. The ICC and CCC were excellent in the evaluation of AXL, CCT and ACD, and were also good in regard to K1, K2, LT and WTW.

CONCLUSIONS

Performing biometry with the SS-OCT Anterion is a reliable and reproducible procedure, and it is comparable with the Lenstar LS900.

Autorefraction as an Objective Method to Evaluate Accuracy of Intraocular Lens Calculation Formulas

PURPOSE

To compare the spherical equivalent (SE) and astigmatic prediction error between subjective refraction (SUBref) and autorefraction (AUTOref) after cataract surgery to determine whether the latter is useful as an objective method to compare the accuracy of different methods of intraocular lens (IOL) power calculation.

METHODS

Postoperative refraction was examined using two techniques: SUBref and AUTOref. The results of these two techniques were compared. Predicted postoperative refraction for spherical outcome was calculated with the Barrett Universal II (BUII), Haigis, Holladay I, SRK/T, Hoffer Q, and BUII with measured posterior corneal astigmatism (MPCA) formulas. Predicted postoperative refraction for astigmatic outcome was calculated with the Barrett Toric calculator, vergence-based toric calculator using the Holladay 1 formula for effective lens position, and Barrett Toric calculator MPCA formulas. Formula accuracy and ranking were compared between the two methods of refraction.

RESULTS

Data were obtained from 219 eyes of 155 patients. Statistically significant differences were detected between SUBref and AUTOref for SE, J₀, and J₄₅ (P < .001). The spherical outcome formula analysis demonstrated no significant differences, whereas the predicted cylinder power analysis demonstrated significant differences within individual formulas between SUBref and AUTOref measures. The lowest median absolute error and the highest percentage of eyes achieving their refractive target for both SUBref and AUTOref were achieved with the BUII formula and the Barrett Toric calculator.

CONCLUSIONS

AUTOref is a useful method with adequate accuracy to determine spherical and astigmatic outcome and equally or more effective in being able to discriminate between spherical outcome formulas. The AUTOref method can allow valuable studies to be conducted in less-than-optimal environments and provides the ability to compare studies without the confounding factors of SUBref. [J Refract Surg. 2022;38(9):580-586.].

Different lens power calculation formulas for the prediction of refractive outcome after phacoemulsification with silicone oil removal

Background

Formulas predicting intraocular lens power have not been compared in silicone oil-tamponaded eyes. The study aims to compare six intraocular lens power assessment formulas in silicone oil-tamponaded eyes.

Methods

This prospective study included patients with silicone oil-tamponaded eyes scheduled for silicone oil removal, phacoemulsification, and intraocular lens implantation at Chongqing Aier Eye Hospital (June 2019 to December 2019). Implanted intraocular lens power was used to predict postsurgical spherical equivalence using SRK/T, Holladay 1, Holladay 2, Haigis, Hoffer Q, and Barrett Universal II, and assess those formula’s predictive accuracy with predictive error.

Results

The analysis included 47 eyes in 47 patients (28 and 19 eyes with normal and long axial length, respectively). Postoperative spherical equivalence at 6 months in normal and long axial length eyes was − 0.6 ± 0.96 and − 0.8 ± 1.52 D, respectively. Predictive error values for SRK/T, Holladay 1, Holladay 2, Haigis, and Hoffer Q and Barrett Universal II were − 0.18 ± 0.92, − 0.15 ± 0.88, − 0.06 ± 0.94, − 0.15 ± 0.87, and − 0.05 ± 0.90 D and − 0.06 ± 0.90, respectively, for normal axial length eyes and 0.15 ± 1.16, 0.46 ± 1.17, 0.28 ± 1.11, − 0.04 ± 1.12, 0.49 ± 1.09 D and 0.11 ± 0.99, respectively, for long axial length eyes. For normal axial length eyes, predicted outcomes were similar to actual outcomes for all formulas. For long axial length eyes, predicted outcomes differed significantly from measured postsurgical values for Holladay 1, Holladay 2, and Hoffer Q (P < 0.05) but not SRK/T or Haigis or Barrett Universal II .

Conclusions

The formulas had comparable predictive accuracy in silicone oil-tamponaded eyes with normal axial length, but Haigis or SRK/T or Barrett Universal II may be preferable in long axial length eyes.

Trial registration

ChiCTR1900023215.

Influence of Dry Eye Disease on the Measurement Repeatability of Corneal Curvature Radius and Axial Length in Patients with Cataract

The influence of dry eye disease (DED) on ocular biometric measurements is unclear. We aimed to investigate the effect of DED on the repeatability of ocular biometric measurements in cataract patients. Overall, 114 eyes scheduled for cataract surgery were enrolled. Before surgery, DED parameters including tear film break-up time (BUT), corneal and conjunctival staining scores, and subjective symptoms were examined. Corneal curvature radius and axial length were assessed twice on the same day using IOLMaster-500 (Carl Zeiss Meditec), and the absolute difference between the two measurements was calculated and used as an index of measurement repeatability. The measurement repeatability of the steep meridian of corneal curvature radius was significantly worse in eyes with DED than in those without DED (p = 0.044) and was significantly associated with BUT (r = −0.206, p = 0.031). The measurement repeatability of axial length was negatively correlated with BUT (r = −0.199, p = 0.041) and positively correlated with the corneal staining score (r = 0.253, p = 0.009). In conclusion, the measurement repeatability of corneal curvature radius declined in eyes with DED. Shortened BUTs were associated with a deterioration in the measurement repeatability of corneal curvature radius and 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.

Intraocular Lens Power Calculation According to the Difference between Anterior and Total Keratometry Using Scheimpflug Imaging

Purpose: We investigated the change in the absolute error according to the difference between anterior and total keratometry, to determine the criterion for the difference in keratometry, and to determine the indication for using total keratometry. Methods: Sagittal and total refractive power were measured with 2-, 3-, and 4-mm Pentacam^® rings, and the absolute error of each was calculated in patients who underwent cataract surgery in our hospital. The correlation between the difference value the sagittal minus the total refractive power and each absolute error was analyzed by simple regression analysis. The analysis was performed by dividing the patients into two groups based on 0.6, which is the average of the difference between the sagittal and total refractive power for the 3-mm ring. Results: Sagittal power was larger than total refractive power for all rings and the absolute error obtained by applying the total refractive power was larger than the sagittal power for the 2- and 4-mm rings (<i>p</i> < 0.001). The simple regression analysis revealed that the absolute error using sagittal power was positively correlated with the difference between sagittal power and total refractive power. In the group with less than 0.6, the absolute error using the total refractive power of all rings was larger than the sagittal power (<i>p</i> < 0.001). In the group exceeding 0.6, the absolute error using the total refractive power was less than using the sagittal power for the 3 mm ring (<i>p</i> = 0.028). Conclusions: The greater the difference between sagittal and total refractive power, the greater the absolute error using sagittal power. Accuracy was higher in the group exceeding 0.6 after applying total refractive power measured at the 3 mm ring compared to sagittal power.

ASSESSING REFRACTIVE OUTCOMES AND ACCURACY OF BIOMETRY IN PHACOVITRECTOMY AND SEQUENTIAL OPERATIONS IN PATIENTS WITH RETINAL DETACHMENT COMPARED WITH ROUTINE CATARACT SURGERY

PURPOSE

To compare refractive outcomes and accuracy of modern optical biometry, swept-source optical coherence tomography, ultrasound biometry, and effect of the macula status in rhegmatogenous retinal detachment managed with either combined phacovitrectomy or sequential vitrectomy and cataract surgery compared with a control, phacoemulsification alone.

METHODS

Retrospective, comparative, consecutive study of 154 eyes; Group 1 underwent phacovitrectomy (n: 70), Group 2 underwent vitrectomy with subsequent cataract surgery (n: 41), and Group 3 underwent cataract surgery alone (n: 43).

RESULTS

No difference in the mean absolute error was found between Group 2 (0.41 ± 0.56) and Group 3 (0.41 ± 0.29); both were superior to Group 1 (0.74 ± 0.57). Between Group 1 and Group 2, no statistically significant difference in the mean absolute error was found between macula-on subgroups (P = 0.057), but this was statistically significant between macula-off subgroups (P = 0.009). Subgroup analysis by biometry showed that the difference in the mean absolute error between macula-off optical biometry Group 1 and Group 2 against our control, Group 3, were not significant (P = 0.078 and P = 0.119, respectively); the mean absolute error was significantly different when considering macula-off ultrasound biometry cases (P < 0.001 and P = 0.038, respectively).

CONCLUSION

All three groups had comparable refractive outcomes when using optical biometry. However, phacovitrectomy macula-off cases had inferior refractive outcomes when the ultrasound biometry had to be used. In macula-off rhegmatogenous retinal detachment, when optical biometry is not reliable, it is preferable to perform sequential surgery rather than phacovitrectomy.

Comparison of IOL Power Calculation Formulas for a Trifocal IOL in Eyes With High Myopia

PURPOSE

To analyze the results of new intraocular lens (IOL) formulas (Emmetropia Verifying Optical [EVO], Kane, Olsen, and Barrett Universal II), traditional formulas (Haigis and SRK/T), and modified Wang-Koch axial length adjustment formulas with the SRK/T and Holladay 1 (SRK/T_modified-W/K and H1_modified-W/K) in Chinese patients with long eyes.

METHODS

In this retrospective case series, patients with an axial length of 26 mm or greater having uneventful femtosecond laser-assisted cataract surgery with one trifocal IOL model were enrolled. The actual postoperative spherical equivalent of the manifest refraction was compared with the formula-predicted refraction based on the implanted IOL power. A subgroup analysis was performed based on the axial length.

RESULTS

A total of 113 eyes was enrolled. Using User Group for Laser Interference Biometry constants, the modified Wang-Koch formulas had the lowest percentage of eyes with hyperopic outcomes. The Barrett Universal II, Olsen, Kane, and EVO 2.0 formulas produced a statistically lower median absolute error than the SRK/T_modified-W/K and SRK/T formulas (P < .05). The Barrett Universal II formula produced higher percentages of eyes within ±0.50 diopters (D) of the prediction error than the SRK/T formula (P < .05). In eyes with axial lengths of less than 28 mm, there were no significant differences in the prediction accuracy of the eight formulas. In eyes with axial lengths of 28 mm or greater, the new IOL formulas yielded the lowest median absolute error, followed by the H1_modified-W/K and Haigis formulas. The SRK/T_modified-W/K formula had the highest mean absolute error and the lowest percentages of eyes within ±0.25 and ±0.50 D of endpoint. The traditional formulas yielded the highest risk of refractive surprise.

CONCLUSIONS

All formulas achieved good results in eyes with axial lengths of less than 28 mm with trifocal IOL implanted. The newer formulas tend to produce better outcomes for eyes with high myopia. The SRK/T_modified-W/K formula provided improved accuracy only in eyes with axial lengths of 30 mm or greater. [J Refract Surg. 2021;37(8):538-544.].

Refractive prediction of four different intraocular lens calculation formulas compared between new swept source optical coherence tomography and partial coherence interferometry

Purpose

To compare the biometry and prediction of postoperative refractive outcomes of four different formulae (Haigis, SRK/T, Holladay1, Barrett Universal II) obtained by swept-source optical coherence tomography (SS-OCT) biometers and partial coherence interferometry (PCI; IOLMaster ver 5.4).

Methods

We compared the biometric values of SS-OCT (ANTERION, Heidelberg Engineering Inc., Heidelberg, Germany) and PCI (IOLMaster, Carl Zeiss Meditec, Jena, Germany). Predictive errors calculated using four different formulae (Haigis, SRKT, Holladay1, Barrett Universal II) were compared at 1 month after cataract surgery.

Results

The mean preoperative axial length (AL) showed no statistically significant difference between SS-OCT and PCI (SS-OCT: 23.78 ± 0.12 mm and PCI: 23.77 ± 0.12 mm). The mean anterior chamber depth (ACD) was 3.30 ± 0.04 mm for SS-OCT and 3.23 ± 0.04 mm for PCI, which was significantly different between the two techniques. The mean corneal curvature also differed significantly between the two techniques. The difference in mean arithmetic prediction error was significant in the Haigis, SRKT, and Holladay1 formulae. The difference in mean absolute prediction error was significant in all four formulae.

Conclusions

SS-OCT and PCI demonstrated good agreement on biometric measurements; however, there were significant differences in some biometric values. These differences in some ocular biometrics can cause a difference in refractive error after cataract surgery. New type SS-OCT was not superior to the IOL power prediction calculated by PCI.

The impact of cataract progression on accuracy of intraocular lens power measurement

Purpose

The aim of this study was to assess the impact of cataract progression using the Haigis formula-calculated intraocular lens (IOL) power and investigate the accuracy of IOL power measured at different time points.

Methods

This prospective study was performed on 75 eyes of 75 patients who underwent uneventful cataract surgery. Preoperative ocular parameters including axial length (AL), keratometry (K), anterior chamber depth (ACD), corneal astigmatism, corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA) examined at the two time points, more than 3 months preoperatively and preoperative 1 day were compared. The ocular parameters measured in the two time points were used to calculate the predicted implanted IOL power and the actual IOL power was chosen on the basis of parameters measured earlier before surgery using the Haigis formula. The mean numerical error (MNE) and mean absolute error (MAE) predicted by the two time points were also compared.

Results

There were significant differences in the ACD, IOL power, UDVA and CDVA (P<0.01), but no statistical differences in AL, mean K and corneal astigmatism (P>0.05) during the average of 5.6 months before surgery. No statistically significant difference was detected in MNE (P>0.05), while the MAE had a significant difference in the two time points (P<0.05).

Conclusion

The IOL power measured earlier before surgery might result in a higher accuracy and the postoperative refractive outcome tended towards emmetropia.

Accuracy of partial coherence interferometry in patients with large inter-eye axial length difference

Background

To determine accuracy of partial coherence interferometry (PCI) in patients with large inter-eye axial eye length (AEL) difference.

Methods

Patients undergoing cataract surgery at two academic medical centers with an inter-eye axial eye length (AEL) difference of > 0.30 mm were identified and were matched to control patients without inter-eye AEL difference > 0.30 mm on the basis of age, sex, and AEL. The expected post-operative refraction for the implanted IOL was calculated using SRK/T, Holladay II, and Hoffer Q formulae. The main outcome measures were the refractive prediction error and the equivalence of the refractive outcomes between the subjects and controls.

Results

Review of 2212 eyes from 1617 patients found 131 eyes of 93 patients which met inclusion criteria. These were matched to 131 control eyes of 115 patients. The mean AEL was 24.92 ± 1.50 mm. The mean absolute error (MAE) ranged from 0.47 D to 0.69 D, and was not statistically different between subjects and controls. The refractive prediction error was equivalent between the cases and controls, with no significant difference between the MAE for any formula, nor in the number of cases vs. controls with a refractive prediction error of at least 0.50 D or 1.00 D.

Conclusions

Among eyes in our study population, good-quality PCI data was equally accurate in patients with or without an inter-eye AEL difference > 0.30 mm. Confirmatory AEL measurements using different AEL measuring modalities in patients with a large inter-eye AEL difference may not be necessary.

Intraocular lens power calculation for plus and minus lenses in high myopia using partial coherence interferometry

Purpose

We assessed the accuracy of lens power calculation in highly myopic patients implanting plus and minus intraocular lenses (IOL).

Methods

We included 58 consecutive, myopic eyes with an axial length (AL) > 26.0 mm, undergoing phacoemulsification and IOL implantation following biometry using the IOLMaster 500. For lens power calculation, the Haigis formula was used in all cases. For comparison, refraction was back-calculated using the Barrett Universal II (Barrett), Holladay I, Hill-RBF (RBF) and SRK/T formulae.

Results

The mean axial length was 30.17 ± 2.67 mm. Barrett (80%), Haigis (87%) and RBF (82%) showed comparable numbers of IOLs within 1 diopter (D) of target refraction. Visual acuity (BSCVA) improved (p < 0.001) from 0.60 ± 0.35 to 0.29 ± 0.29 logMAR (> 28-days postsurgery). The median absolute error (MedAE) of Barrett 0.49 D, Haigis 0.38, RBF 0.44 and SRK/T 0.44 did not differ. The MedAE of Haigis was significantly smaller than Holladay (0.75 D; p = 0.01). All median postoperative refractive errors (MedRE) differed significantly with the exception of Haigis to SRK/T (p = 0.6): Barrett − 0.33 D, Haigis 0.25, Holladay 0.63, RBF 0.04 and SRK/T 0.13. Barrett, Haigis, Holladay and RBF showed a tendency for higher MedAEs in their minus compared to plus IOLs, which only reached significance for SRK/T (p = 0.001). Barrett (p < 0.001) and RBF (p = 0.04) showed myopic, SRK/T (p = 002) a hyperopic shift in their minus IOLs.

Conclusions

In highly myopic patients, the accuracies of Barrett, Haigis and RBF were comparable with a tendency for higher MedAEs in minus IOLs. Barrett and RBF showed myopic, SRK/T a hyperopic shift in their minus IOLs.

Preoperative measurements for cataract surgery: a comparison of ultrasound and optical biometric devices

PURPOSE

To evaluate differences in preoperative measurements and refractive outcomes between ultrasound and optical biometry when using the Barrett Universal II intraocular lens (IOL) power formula.

METHODS

In this consecutive case series, cataract extraction and IOL implantation cases from two surgical centers in Toronto, Canada, were recruited between January 2015 and July 2017. Differences between ultrasound (applanation or immersion A-scan) and optical biometry (IOLMaster 500) were compared for axial length (AL), anterior chamber depth and refractive outcomes. The primary outcome was the percentage of cases in each cohort within ± 0.50D of refractive error.

RESULTS

In total, 527 cataract cases underwent IOLMaster testing. Of these, 329 eyes (62.4%) were also measured by applanation A-scan, and the other 198 eyes (37.6%) received immersion A-scan testing. Applanation ultrasound led to 5.8%, 16.0% and 46.4% of eyes within ± 0.25D, ± 0.50D and ± 1.00D of refractive error, respectively, whereas the IOLMaster 500 led to 48.5%, 77.1% and 94.9%, respectively (n = 293, ± 0.50D: p < 0.001). Immersion ultrasound led to 31.2%, 57.6% and 91.2% of eyes within ± 0.25D, ± 0.50D and ± 1.00D of refractive error, respectively, whereas the IOLMaster 500 led to 42.4%, 72.0% and 92.0%, respectively (n = 125, ± 0.50D: p = 0.001). Applanation (n = 329, A-scan AL: 23.64 ± 1.67 mm, IOLMaster AL: 24.20 ± 1.70 mm, p < 0.001) and immersion ultrasound (n = 198, A-scan AL: 25.01 ± 2.06 mm, IOLMaster AL: 25.08 ± 2.13 mm, p = 0.002) yielded significantly lower AL values compared to optical biometry measurements.

CONCLUSIONS

Optical biometry yielded a significantly larger percentage of cases within ± 0.50D of refractive error compared to ultrasound biometry when using the Barrett Universal II IOL power formula.

Normative Values of Corneal Spherical Aberration, Pupil Size, and Other Key Refractive and Topographic Parameters in a Large Cohort of Egyptian Cataract Surgery Candidates

Purpose

To determine the spherical aberration, pupil size, and other key refractive and topographic parameters in a large cohort of Egyptian cataract surgery candidates, and to investigate any existent relations between the spherical aberration and other possibly related parameters.

Methods

This is a cross-sectional, descriptive study that was conducted at Ain Shams University Hospitals, Cairo, Egypt. The study was performed on the right eyes of 1658 cataract surgery candidates. The mean corneal spherical aberration [Z4] and the pupil diameter, both photopic [P. Pupil] and mesopic [M. Pupil], were measured by the Oculus Keratograph 3, while the white-to-white corneal diameter [WTW], average keratometric readings [average K], axial length measurements [AL] and Anterior Chamber Depth [ACD] were all obtained from the IOL Master 500.

Results

The mean age was 65 ± 11.3 years. The mean value of the Z4 was +0.26 ± 0.12 μm [95% Confidence Interval “CI” (0.2570–0.2681)]. The mean values of the measured parameters were: P. Pupil 2.43 ± 0.87 mm [95% CI (2.3867–2.4700)], M. Pupil 4.61 ± 0.91 mm [95% CI (4.5683–4.6557)], WTW 11.72 ± 0.44 mm [95% CI (11.6969–11.7394)], average K 43.89 ± 1.89 D [95% CI (43.7938–43.9701)], AL 24.23 ± 2.21 mm [95% CI (24.1118–24.3166)], and ACD 3.16 ± 0.43 mm [95% CI (3.1414–3.1827)]. Weak statistically significant correlations were found between the Z4 and each of age (r = 0.049, p = 0.044), average K (r = 0.191, p < 0.001), and ACD (r = 0.122, p < 0.001). Multivariate analysis showed weaker relations between Z4 and both average K (beta coefficient= 0.091) and ACD (beta coefficient= 0.130), with an r² = 0.024.

Conclusion

This is the first normative data report of corneal spherical aberration [Z4], pupil size, and related refractive and topographic parameters in an old Egyptian population. The detected correlations have a weak clinical relevance and negate the existence of significant relations between the Z4 and the studied refractive and topographic parameters.

Ratio of Axial Length to Corneal Radius in Japanese Patients and Accuracy of Intraocular Lens Power Calculation Based on Biometric Data

PURPOSE

To evaluate the features of the axial length-to-corneal radius (AL/CR) ratio in Japanese patients with cataracts and to determine the accuracy of intraocular lens (IOL) power calculation formulas according to the AL/CR features and the axial length (AL).

DESIGN

Retrospective observational case series.

METHODS

Setting was a clinical practice. Patient population was a total of 1,135 eyes (1,135 patients) with cataracts. Observation procedures included measurement of the AL and corenal radius (CR) by optical biometry and evaluation of the refractive outcomes by using the SRK/T, Holladay 1, Hoffer Q, Haigis, and Barrett Universal II formulas. Main outcome measurements were the features of the AL/CR ratio and the accuracy of IOL power calculations based on the AL/CR ratio and the AL.

RESULTS

The mean AL/CR ratio was 3.15 ± 0.19. Significant weak negative correlations were observed between the spherical equivalent (SE) and AL (r = -0.7489; P < .001) and between the SE and AL/CR ratio (r = -0.8069; P < .001); no correlation was found between the SE and CR (r = 0.0208, P = .483). For medium ALs and high AL/CR ratios, the SRK/T formula performed less accurately. For long ALs and high AL/CR ratios, the Holladay 1 and Hoffer Q formulas performed less accurately. The Barrett Universal II formula performed well across a range of ALs and AL/CR ratios.

CONCLUSIONS

The AL/CR ratio explained the total variation in the SE better than the AL alone. Surgeons should pay attention to the selection of IOL power calculation formulas in eyes with high AL/CR ratios.

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.

Effect of manual capsulorhexis size and position on intraocular lens tilt, centration, and axial position

PURPOSE

To evaluate the influence of a manual capsulorhexis size, shape, and position on postoperative axial position, tilt, and centration of intraocular lenses (IOLs).

SETTING

Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective cases series.

METHODS

Patients had cataract surgery and had follow-ups 1 hour and 3 months after surgery. Postoperatively, patients were divided into 3 groups according to the capsulorhexis shape and size as follows: control, symmetrical capsulorhexis between 4.5 mm and 5.5 mm; small group, capsulorhexis smaller than 4.5 mm; and eccentric, all other capsulorhexes. At both follow-ups, a retroillumination image, partial coherence interferometry measurements, and Purkinje meter measurements were performed.

RESULTS

This study comprised 255 eyes. The mean postoperative absolute anterior chamber depth shift in the control, eccentric capsulorhexis, and small capsulorhexis groups was 0.31 mm ± 0.27 (SD), 0.36 ± 0.24 mm, and 0.26 ± 0.24 mm, respectively (P = .419). The mean tilt in the control, eccentric capsulorhexis, and small capsulorhexis groups was 4.08 ± 2.13 degrees, 3.66 ± 2.04 degrees, and 2.82 ± 1.67 degrees, respectively (P = .370), and the mean decentration was 0.38 ± 0.23 mm, 0.40 ± 0.21 mm, and 0.17 ± 0.08 mm, respectively (P = .027).

CONCLUSIONS

Capsulorhexis size and shape had little effect on the capsular bag performance of modern IOLs. Only eyes with a severely malformed capsulorhexis had a slightly decentered IOL.

Effect of fixation stability during biometry measurements on refractive prediction accuracy in highly myopic eyes

PURPOSE

To assess the effect of preoperative biometry fixation stability on postoperative refractive errors in highly myopic cataractous eyes.

SETTING

Eye and ENT Hospital of Fudan University, Shanghai, China.

DESIGN

Prospective cohort study.

METHODS

Eyes of highly myopic patients and emmetropic controls were included. Routine ophthalmologic examinations and measurement of fixation stability in the 63% and 95% bivariate contour ellipse areas (BCEAs) were conducted preoperatively. The refractive error from prediction was calculated 1 month postoperatively with the SRK/T and Holladay 1 formulas. Univariate and multivariable analyses were performed to identify the factors associated with postoperative refractive errors.

RESULTS

The refractive errors were more widely distributed in the 45 highly myopic eyes than in the 40 emmetropic control eyes: SRK/T, +0.15 diopter [D] ± 0.80 [SD] and -0.16 ± 0.35 D, respectively; Holladay 1, +0.54 ± 0.79 D and -0.23 ± 0.34 D, respectively. In the highly myopic group, 63% BCEA was correlated with axial length (AL) (P = .021) and posterior subcapsular opacity grade (P = .040). With both formulas, refractive errors and absolute refractive errors were positively correlated with 63% BCEA: SRK/T, P = .010 and P = .001, respectively; Holladay 1, P = .006 and P = .003, respectively. Backward multiple linear regression analysis showed that with both formulas, AL and 63% BCEA were significantly associated with postoperative refractive errors.

CONCLUSION

Poor preoperative biometry fixation stability correlated with long AL and severe posterior subcapsular opacity contributed to significant deviation of refractive errors after cataract surgery in highly myopic eyes.

Clinical and biometric determinants of actual lens position after cataract surgery

PURPOSE

To evaluate the preoperative clinical and biometric determinants associated with the actual lens position after cataract surgery.

SETTING

Department of Ophthalmology, University Hospital of Montpellier, France.

DESIGN

Prospective longitudinal cohort study.

METHODS

The data collected included clinical factors (age, sex, history of vitrectomy) and biometry factors (axial length [AL], anterior chamber depth [ACD], lens thickness, white-to-white [WTW] distance) that might affect actual lens position. Each patient had optical low-coherence reflectometry biometry (Lenstar) preoperatively and 1 month postoperatively. The actual lens position was measured as the postoperative position of the center of the intraocular lens (IOL). Patients were stratified into 3 groups by type of IOL: Acrysof SN60WF or SN6AT (Group 1), Tecnis ZCB00 or ZCT (Group 2), and Asphina 409 MV (Group 3).

RESULTS

The study comprised 168 eyes (mean age 73.3 years ± 9.8 [SD]). The mean actual lens position was 4.88 ± 0.29 mm, 5.01 ± 0.29 mm, and 5.05 ± 0.32 mm in Group 1 (n = 67 eyes), Group 2 (n = 52 eyes), and Group 3 (n = 49 eyes), respectively. In the overall population, AL, ACD, anterior segment depth, and WTW distance were correlated with actual lens position (r = 0.48, P < .0001; r = 0.64, P < .001; r = 0.58, P < .0001; r = 0.39, P < .001, respectively).

CONCLUSIONS

The AL, ACD, anterior segment depth, and WTW distance correlated with actual lens position after cataract surgery. The integration of these data in IOL formulas could help improve refractive outcomes after the surgery.

Comparison of a new Scheimpflug imaging combined with partial coherence interferometry biometer and a low-coherence reflectometry biometer

PURPOSE

To evaluate the repeatability of a new biometer using Scheimpflug technology combined with partial coherence interferometry (PCI) (Pentacam AXL) and its agreement with a device based on optical low-coherence reflectometry (OLCR), the Allegro Biograph.

SETTING

Oftalvist Centro Integral Ocular Jerez, Jerez de la Frontera, Spain.

DESIGN

Evaluation of a diagnostic test.

METHODS

The mean keratometry (K), central corneal thickness (CCT), anterior chamber depth (ACD), and axial length (AL) were measured with the 2 devices 3 times by the same examiner in 2 groups (patients with cataract and patients without cataract). The repeatability was determined using the within-subject standard deviation, test-retest repeatability, coefficient of variation, and intraclass correlation coefficient. The correlation was evaluated with the Pearson coefficient and interchangeability with the Bland-Altman plot.

RESULTS

Eighty eyes (40 eyes in each group) of 80 patients were analyzed. Significant differences were found between the Scheimpflug-PCI device and the OLCR device for mean K in the normal group (P < .001) and for CCT in the normal group (P < .05) and the cataract group (P < .001). There were no differences between devices in ACD and AL in either group. The repeatability between devices was similar. Although a significant correlation between devices was found for all measurements (all P < .001), wide limits of agreement were found in both groups for all biometric parameters.

CONCLUSIONS

The Scheimpflug-PCI and OLCR devices showed excellent intravisit repeatability and high correlation for mean K, CCT, ACD, and AL in healthy and cataractous eyes. No differences were found in AL; however, the 2 devices might not be interchangeable.

Analysis of the effect of repair materials for orbital blowout fracture on complications

AIM

To investigate the effect of repair materials for orbital blowout fractures on the occurrence of postoperative complications.

METHODS

The clinical data and follow-up data of 54 subjects with orbital blowout fractures were retrospectively analyzed. The study was divided into three groups according to the used repair materials: titanium mesh (16 cases), Medpor (12 cases), and Medpor titanium mesh (26 cases). All test data were analyzed using the SPSS version 23.0 statistical software. The mean age and duration of disease between the groups were compared through one-way analysis of variance. The Chi-square (χ ²) test was used to compare the number of males and females, different fracture types, and different surgical approaches among groups. The χ ² test was used to compare the frequencies for complications in each group.

RESULTS

The baseline characteristics of age and gender in each group were matched (F=1.763, P=0.172; χ ²=0.026, P=0.987). In addition, there was no difference in the type of fracture and surgical approach (χ ²=0.460, P=0.977; χ ²=0.691, P=0.952), or the incidence of complications (χ ²=0.081, P=0.960) between the three groups.

CONCLUSION

Although there is no difference in effect of various repair materials on the incidence of complications, the effect of repair materials on postoperative complications of orbital blowout fractures should not be ignored.

Comparison of six methods for the intraocular lens power calculation in high myopic eyes

PURPOSE

The aim of this study was to compare the accuracy of Barrett Universal II and Hill-Radial Basis Function with other four popular formulas for the calculation of intraocular lens power in high myopic eyes.

METHODS

A total of 56 eyes with an axial length of more than 26.0 mm were retrospectively reviewed. Six intraocular lens power calculation methods, including Barrett Universal II, Hill-Radial Basis Function, SRK/T, Haigis, Holladay 2 and Holladay 1, were evaluated. The difference between the postoperative actual refraction and the refraction predicted by the six methods was evaluated as the prediction error. The absolute prediction error was also calculated.

RESULTS

The mean numerical prediction error ± standard deviation of the six intraocular lens power calculation methods, in order of lowest to highest, was Barrett Universal II (0.37 ± 0.54 D), Hill-Radial Basis Function (0.40 ± 0.56 D), SRK/T (0.44 ± 0.56 D), Haigis (0.53 ± 0.54 D), Holladay 2 (0.88 ± 0.62 D) and Holladay 1 (1.00 ± 0.60 D). The median absolute errors predicted by the Barrett (0.46 D), Hill-Radial Basis Function (0.47 D), SRK/T (0.53 D) and Haigis (0.58 D) were significantly lower than those of the Holladay 1 (0.90 D) and Holladay 2(1.10 D; all p < 0.001). There was no significant difference among the median absolute errors of Barrett, Hill-Radial Basis Function, SRK/T and Haigis (all p > 0.05).

CONCLUSION

The prediction errors differed for each method in the selection of intraocular lens power for the long eyes. In terms of overall accuracy, the Barrett Universal II formula provided the lowest prediction error. The Hill-Radial Basis Function method was comparable to the theoretical formulas, such as SRK/T and Haigis.

Improved Refractive Outcomes of Small-Incision Extracapsular Cataract Surgery after Implementation of a Biometry Training Course

PURPOSE:

To determine whether a biometry training course could improve refractive outcomes of patients undergoing manual small-incision extracapsular cataract surgery (SICS).

MATERIALS AND METHODS:

This was a prospective, interventional, cohort study at the Pacific Eye Institute, Fiji. SICS refractive outcomes were evaluated before and after a structured biometry teaching course. Eyes that underwent evaluation and subsequent SICS with placement of a posterior chamber intraocular lens (IOL) were included. Axial length measurements were obtained using A-scan applanation ultrasound and keratometry with a handheld keratometer. Main outcome measures included mean absolute prediction error of IOL calculations, percentage of eyes within ±0.5 D and ±1.0 D of intended spherical equivalent, and proportion of eyes with ≥6/18 uncorrected visual acuity.

RESULTS:

A total of 240 eyes were analyzed: 120 eyes before and 120 eyes after the structured biometry training. The mean absolute prediction error was 50% lower following the training (1.13 ± 0.84 D pre vs. 0.56 ± 0.44 D post; P < 0.001). A higher percentage of the eyes had a postoperative spherical equivalent within ±0.5 D (26.7% pre vs. 52.5% post; P < 0.001) and ±1.0 D (55.0% pre vs. 90.0% post; P < 0.001) of the intended target. A higher proportion of the eyes achieved ≥6/18 uncorrected visual acuity (77.5% pre vs. 91.7% post, P = 0.004), while the proportion with ≥6/18 corrected visual acuity was similar (94.4% pre vs. 98.3% post; P = 0.28).

CONCLUSIONS:

A structured biometry training course may improve the accuracy of preoperative IOL calculations to achieve the postoperative refractive target. Ophthalmology training programs should include structured biometry teaching in their curricula.

Intraocular lens power formula accuracy: Comparison of 7 formulas

PURPOSE

To assess the accuracy of 7 intraocular lens (IOL) power formulas (Barrett Universal II, Haigis, Hoffer Q, Holladay 1, Holladay 2, SRK/T, and T2) using IOLMaster biometry and optimized lens constants.

SETTING

Public hospital ophthalmology department.

DESIGN

Retrospective case series.

METHODS

Data from patients having uneventful cataract surgery with Acrysof IQ SN60WF IOL implantation over 5 years were obtained from the biometry and patient charts. Optimized lens constants were calculated for each formula and used to determine the predicted refractive outcome for each patient. This was compared with the actual refractive outcome to give the prediction error. Eyes were separated into subgroups based on axial length (AL) as follows: short (≤22.0 mm), medium (>22.0 to <24.5 mm), medium long (≥24.5 to <26.0 mm), and long (≥26.0 mm).

RESULTS

The study included 3241 patients. The Barrett Universal II formula had the lowest mean absolute prediction error over the entire AL range (P < .001, all formulas) as well as in the medium (P < .001, all formulas), medium-long (P < .001, except Holladay 1 and T2), and long AL (P < .001, except T2) subgroups. No statistically significant difference was seen between formulas in the short AL subgroup. Overall, the Barrett Universal II formula resulted in the highest percentage of eyes with prediction errors between ±0.25 diopter D, ±0.50 D, and ±1.00 D.

CONCLUSION

In eyes with an AL longer than 22.0 mm, the Barrett Universal II formula was a more accurate predictor of actual postoperative refraction than the other formulas.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Predictive accuracy of partial coherence interferometry and swept-source optical coherence tomography for intraocular lens power calculation

The purpose of this study is to compare the predictive accuracy of intraocular lens (IOL) calculations made with partial coherence interferometry (PCI, IOLMaster, version 5) and swept-source optical coherence tomography (SS-OCT, Argos). Axial length (AL), mean keratometry value (K), and anterior chamber depth (ACD) were obtained using PCI and SS-OCT optical biometers. Intraocular lens (IOL) power calculations were made using the Barret-Universal II, Haigis, Hoffer Q, SRK/T, and T2 formulas and compared the predictive accuracy between biometers. In 153 eyes (153 patients), axial length measurements made with PCI (24.65 ± 2.35 mm) and SS-OCT (24.62 ± 2.29 mm) were significantly different (P < 0.001). Corneal power (P = 0.97) and anterior chamber depth (P = 0.51) were not significantly different between biometer. The mean absolute error was not significantly different between the five IOL power calculation formulas for either PCI or SS-OCT measurements. When AL was 24.5–26.0 mm, mean absolute error derived from SS-OCT was smaller than mean absolute error derived from PCI for all five IOL power calculation formulas (all P < 0.05). In conclusion, predictive accuracy of PCI and SS-OCT were nearly the same. However, in medium-long eyes, the predictive accuracy of SS-OCT for IOL calculations was higher.

Intraoperative optical coherence tomography measurements of aphakic eyes to predict postoperative position of 2 intraocular lens designs

PURPOSE

To evaluate intraoperative anterior chamber depth (ACD) measurements of the aphakic eye to predict the postoperative ACD and compare 2 intraocular lens (IOL) designs.

SETTING

Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective study.

METHODS

In this prospective study, patients scheduled for cataract surgery received a plate-haptic IOL (Asphina, Carl Zeiss Meditec AG) or an open-loop haptic IOL (ZCB00, Johnson & Johnson). Preoperatively, optical biometry (IOLMaster 700, CZM, or Lenstar, Haag-Streit) was performed. Intraoperatively, a prototype setup was used to perform time-domain OCT scans of the anterior eye segment (Visante connected to OPMI Lumera 200, both CZM). The intraoperative ACD was measured and used to predict the postoperative IOL position. Optical biometry and subjective refraction and autorefraction (RM 8800, Topcon) were performed 2 months postoperatively.

RESULTS

The study comprised 203 eyes of 203 patients. A partial least-square regression model for ACD generated 2 months postoperatively showed that the predictive power of the intraoperative ACD (0.48) was highest followed by the axial eye length (0.45) and then the preoperatively measured ACD (0.30). These findings were confirmed in a bootstrapping model. Regression models combining the preoperative ACD and intraoperative ACD resulted in further significant improvement.

CONCLUSIONS

Intraoperative ACD measurements predicted the postoperative position of open-loop IOLs and plate-haptic IOLs better than preoperative ACD measurements. Combining preoperative and intraoperative ACD measurements further improved the prediction.

Comparison of optical biometry versus ultrasound biometry in cases with borderline signal-to-noise ratio

Purpose

To ascertain if optical biometry determination of axial length (AL) and intraocular lens (IOL) power is significantly different compared to ultrasound (US) biometry in cases with borderline signal-to-noise ratio (SNR).

Patients and methods

Sixty patients who had cataract and IOL Master biometry with borderline SNR (1.6–2.0) were included. A retrospective chart review was performed to compare data collected with optical biometry and US biometry in cataract cases with borderline SNR.

Results

Results showed that optical biometry IOL and AL measurements were not significantly different from the US measurements. Analysis also demonstrated good agreement between the two methods.

Conclusion

Our study suggests that, in cases of borderline quality data, IOL power and AL measurements with optical biometry are still useful in surgical planning and that additional US measurements may be used more as a corroborative tool.

Effect of Cycloplegia on Optical Biometry in Pediatric Eyes

PURPOSE

To study the effect of cycloplegia on optical biometry parameters in pediatric eyes using the Lenstar LS 900 (Haag-Streit, Koeniz, Switzerland).

METHODS

In this observational and comparative study, 56 normal eyes and 20 cataractous eyes in children between 5 and 15 years of age were included. Measurements were taken before and after cycloplegia using 2% homatropine drops. Parameters studied were axial length, central corneal thickness, keratometry, anterior chamber depth, and lens thickness. The Wilcoxon test was used to compare the effects of cycloplegia on all parameters.

RESULTS

Cycloplegia resulted in a statistically significant decrease in axial length (P < .05), central corneal thickness (P < .05), and lens thickness (P < .001) and an increase in the anterior chamber depth (P < .001) in normal eyes. In the cataract group, cycloplegia resulted in an increase in anterior chamber depth (P < .001) and decrease in lens thickness (P < .001).

CONCLUSIONS

Biometry measurements have to be carefully interpreted in pediatric eyes where cycloplegia is an important part of the examination. [J Pediatr Ophthalmol Strabismus. 2018;55(4):260-265.].

Post-operative Refractive Prediction Error After Phacovitrectomy: A Retrospective Study

Introduction

Many authors have reported on a myopic post-operative refractive prediction error when combining phacoemulsification with pars plana vitrectomy (phacovitrectomy). In this study we evaluate the amount of this error in our facility and try to elucidate the various factors involved.

Methods

This was a retrospective study which included 140 patients who underwent phacovitrectomy (39 with macular holes, 88 with puckers, and 13 with floaters). Post-operative refractive error was defined as the difference between the actual spherical equivalent (SEQ) and expected SEQ based on the SRK/T and Holladay-II formulas. Both univariate (paired t test, independent t test, one-way analysis of variance, or Mann–Whitney test) and multivariate (regression analysis) statistical analyses were performed.

Results

Overall, a refractive error of − 0.13 dpt (p = 0.033) and − 0.26 dpt (p < 0.01) were found in the SRK/T and Holladay-II formulas, respectively. For the independent diagnoses, only macular holes showed a myopic error with the SRK/T (− 0.31 dpt; p < 0.01) and Holladay-II (− 0.44 dpt; p < 0.01) formulas. In univariate analysis, significant factors involved in myopic refractive error were macular hole as diagnosis (p < 0.01 for SRK/T and Holladay-II), gas tamponade (SRK/T p = 0.024; Holladay-II p = 0.025), pre-operative myopia (p < 0.01 for SRK/T), and optical technique for axial length measurement (SRK/T and Holladay-II p < 0.01). In the multivariate analysis, pre-operative axial length (p = 0.026), optical technique for axial length measurement (p < 0.01), and pre-operative SEQ (p < 0.01) were independent predictors for myopic refractive error in the SRK/T formula. For the Holladay-II formula, optical technique for axial length measurement (p < 0.01) and pre-operative SEQ (p = 0.04) were predictive.

Conclusion

Various factors are involved in determining the myopic refractive error after phacovitrectomy. Not every factor seems to be as important in each individual patient, suggesting a more tailored approach is warranted to overcome this problem.

Adolf Friedrich Fercher: a pioneer of biomedical optics

Adolf Friedrich Fercher, an outstanding pioneer of biomedical optics, passed away earlier this year. He was a brilliant and visionary researcher who pioneered various fields of biomedical optics, such as laser speckle flowgraphy, tissue interferometry, and optical coherence tomography (OCT). On the occasion of the 25th anniversary of OCT, this paper reviews and commemorates Fercher's pioneering work.

Predictability of Biometry in Patients Undergoing Cataract Surgery

PURPOSE

To compare measurements of axial length (AL), anterior chamber depth (ACD), keratometry (K), and the refractive predictability of the Aladdin and IOLMaster biometry devices in cataract surgery patients.

METHODS

A retrospective observational study of eyes undergoing cataract surgery. Data were retrieved on AL, ACD, and K measurements obtained by the Aladdin and the IOLMaster. Furthermore, the postoperative refractive prediction errors were compared between the devices.

RESULTS

The study included 127 consecutive eyes of 127 patients undergoing cataract surgery. Mean measurements of AL were not significantly different between the Aladdin (24.18 ± 1.89 mm) and IOLMaster (24.18 ± 1.89 mm) (p = 0.792). Mean K measurements were different between Aladdin (43.84 ± 1.56 D) and IOLMaster (43.97 ± 1.61 D) (p < 0.001). For AL, Aladdin measurements correlated strongly with IOLMaster measurements (r = 0.9997). For K, Aladdin measurements correlated strongly with IOLMaster measurements (r = 0.9912). Fifty-eight of the 127 eyes underwent cataract surgery with a monofocal intraocular lens. For these, mean absolute error (MAE) in predicting refraction relative to the measured postoperative refraction differed between Aladdin (MAE = 0.54 ± 0.40D) and IOLMaster (MAE = 0.49 ± 0.41D) (p = 0.001). After adjustment for the systematic difference in K measurements, the difference in MAE was no longer significant (p = 0.601). The ACD measurements did not differ significantly (p = 0.873) and were well correlated (r = 0.8327).

CONCLUSIONS

A very good correlation was found in AL, K, and ACD measurements between the Aladdin biometer and the IOLMaster. Minimal adjustment for the constant difference in keratometry measurements matched the refractive predictability of both devices.

Intraocular Pressure, Axial Length, and Refractive Changes after Phacoemulsification and Trabeculectomy for Open-Angle Glaucoma

PURPOSE

To compare changes in intraocular pressure (IOP), axial eye length (AEL), and refractive outcome in primary open-angle glaucoma patients undergoing cataract surgery and trabeculectomy in dependence of the sequence of surgeries.

MATERIALS AND METHODS

We retrospectively analysed 48 eyes. The changes in refraction, intraocular pressure, and axial eye length were analysed after surgery. In group A (21 subjects), phacoemulsification was performed before trabeculectomy, and in group B (27 subjects), trabeculectomy was performed before phacoemulsification with a minimum time span between interventions of 6 months.

RESULTS

The reduction in IOP and the decrease in AEL after trabeculectomy were significant after 6 and 12 months postsurgery (p < 0.001 each). The decrease in AEL was 0.42 ± 0.11% at 6 months after surgery and 0.40 ± 0.13% after 12 months from surgery; this decrease in AEL was comparable between the groups. The refractive outcome was significantly different between the groups (group A: 0.35 ± 0.75 dpt, group B: -0.05 ± 0.36 dpt, p = 0.018); in group A, trabeculectomy caused a hyperopic shift of 0.34 ± 0.44 dpt (p = 0.002) at 12 months postsurgery.

CONCLUSION

IOP reduction after trabeculectomy causes AEL shortening. The effect on refractive outcome depends on the sequence of surgeries. Better refractive outcome is achieved if phacoemulsification is performed after trabeculectomy.

Predicting the refractive outcome and accuracy of IOL power calculation after phacoemulsification using the SRK/T formula with ultrasound biometry in medium axial lengths

PURPOSE

To evaluate the accuracy of the SRK/T formula using ultrasound (US) biometry in predicting a target postoperative refraction of ±1.00D in eyes with medium axial length (AL) that underwent phacoemulsification.

METHODS

The present study was a retrospective analysis, which included 538 eyes with an AL from 22.0 to 24.60 mm that underwent phacoemulsification and foldable intraocular lens (IOL) implantation (six different IOLs) in the bag. Preoperative AL was measured by US biometry and IOL power (IOLp) was calculated with the SRK/T formula. Patients had a complete ophthalmic examination, preoperatively and 1, 7, and 30 days after surgery. The achieved spherical equivalent (SE) and the prediction error (PE) were calculated. The prediction error was defined as the difference between attempted predicted target refraction and the achieved postoperative SE refraction. Statistical analysis was performed with SPSS V21.

RESULTS

The mean age of the patients was 66.96±9.67 years, the mean AL was 23.29±0.62 mm, the mean K1 was 43.62±1.49D, the mean K2 was 43.69±1.53D, the mean IOL power was 21.066±1.464D, the mean attempted (predicted) SE was -0.178±0.266D, and the mean achieved SE was -0.252±0.562D. The mean PE (difference between predicted and achieved SE) showed a relatively hyperopic shift (mean ± standard deviation: 0.074±0.542D, ranging from -1.855 to 2.170D, P=0.001). A total of 93.87% of eyes were within ±1.00D of the PE and 92.75% of eyes within ±1.00D of achieved postoperative refraction. A total of 39 eyes (7.25%) had a refractive surprise. A total of 32 of 39 eyes were more myopic than -1.00D and 7 of them were more hypermetropic than +1.00D. There was no correlation between the mean PE and IOL type, AL, K1, K2, and IOLp. There were a positive statistically significant correlation between PE and age (r=0.095; P=0.028) and a negative statistically significant correlation between achieved SE and AL (Spearman's r=-0.125; P=0.04), and age (r=-0.141; P=0.01).

CONCLUSION

The IOLp calculation using the SRK/T formula with US biometry may demonstrate very good postoperative refractive outcomes in medium eyes with a few refractive surprises.

Accuracy of optical biometry combined with Placido disc corneal topography for intraocular lens power calculation

PURPOSE

To investigate the accuracy of a new optical biometer for intraocular lens (IOL) power calculation in eyes undergoing cataract surgery.

METHODS

Consecutive eyes of patients undergoing cataract surgery with the same IOL model were enrolled in a prospective cohort study. Axial length (AL) and corneal power were measured with an optical biometer based on optical low-coherence interferometry and Placido-disc corneal topography. IOL power was calculated with the Hoffer Q, Holladay 1 and SRK/T formulas. For each formula the lens constant was optimized in retrospect in order to achieve a mean prediction error (PE) of zero (difference between the predicted and the postoperative refraction). Median absolute error (MedAE) and percentage of eyes with PE ±0.50 D were calculated.

RESULTS

Seventy-four eyes of 74 cataract patients were enrolled. The MedAE was 0.25 D with all formulas. A PE within ±0.50 D was obtained in 89.04% of cases with the Hoffer Q and SRK/T formulas, and in 87.67% of cases with the Holladay 1 formula.

CONCLUSIONS

The optical biometer investigated in the present study provides accurate measurements for IOL power calculation.