Optimising curve fitting techniques to look for standardisation of the analysis of defocus curves derived from multifocal intraocular lenses.

INTRODUCTION: To establish the most appropriate curve fitting method to allow accurate comparison of defocus curves derived from intraocular lenses (IOLs). METHODS: Defocus curves were plotted in five IOL groups (monofocal, extended depth of focus, refractive bifocal, diffractive bifocal and trifocal). Polynomial curves from 2nd to 11th order and cubic splines were fitted. Goodness of fit (GOF) was assessed using five methods: least squares, coefficient of determination (R2adj ), Akaike information criteria (AIC), visual inspection and Snedecor and Cochran. Additional defocus steps at -2.25 D and -2.75 D were measured and compared to the calculated visual acuity (VA) values. Area under the defocus curve and range of focus were also compared. RESULTS: Goodness of fit demonstrated variable results, with more lenient methods such as R2adj leading to overfitting and conservative methods such as AIC resulting in underfitting. Furthermore, conservative methods diminished the inflection points resulting in an underestimation of VA. Polynomial of at least 8th order was required for comparison of area methods, but overfitted the EDoF and monofocal groups; the spline curve was consistent for all IOLs and methods. CONCLUSIONS: This study demonstrates the inherent difficulty of selecting a single polynomial function. The R2 method can be used cautiously along with visual inspection to guard against overfitting. Spline curves are suitable for all IOLs, guarding against the issues of overfitting. Therefore, for analysis of the defocus profile of IOLs, the fitting of a spline curves is advocated and should be used wherever possible.

One-year post-operative comparison of visual function and patient satisfaction with trifocal and extended depth of focus intraocular lenses.

PURPOSE: To evaluate visual performance with trifocal and extended depth of focus IOL at 1 year post-operatively. SETTING: BMI Southend Hospital. DESIGN: Cohort study. METHODS: An age-matched cohort of forty subjects bilaterally implanted with the AT LISA 839MP trifocal IOL (20 patients, 40 eyes) and the Tecnis Symfony extended depth of focus IOL (20 patients, 40 eyes) were assessed at 3-6 months and 12-18 months post-operatively. Primary outcome measures were distance (6 m), intermediate (70 cm), near visual acuity (40 cm), and analysis of defocus profiles. Secondary outcomes included contrast sensitivity, Radner reading performance, quality of vision and assessment of halos. RESULTS: Distance visual acuity (VA) and defocus areas were similar (p = 0.07). No significant difference in intermediate VA was noted but the intermediate area of focus was greater in the EDoF (0.31 ± 0.12 LogMAR*m-1) compared to the trifocal (0.22 ± 0.08LogMAR*m-1) (p = 0.02). However, all near metrics were significantly better in the trifocal group. 80% of trifocal subjects were spectacle independent compared to 50% EDoF subjects. Quality of vision questionnaire found no significant differences between groups, however halo scores were greater at 3-6 months in the trifocal group (p < 0.01) but no differences were noted at 12-18 months. CONCLUSIONS: Near vision is significantly better for the trifocal, thus greater levels of spectacle independence. The range of intermediate vision was greater for the EDoF but no difference in intermediate VA. In the early period, differences in contrast sensitivity and halo size/intensity were noted, however, by one-year these measures were not significantly different.

Predicting the Postoperative Addition Power of a Multifocal Intraocular Lens at the Spectacle Plane.

PURPOSE: To establish a simple clinical method of predicting addition power achieved with a multifocal intraocular lens (IOL). METHODS: In this prospective cohort study, 41 patients were bilaterally implanted with the Bi-Flex MY multifocal IOL (Medicontur) with +3.50 diopters (D) near addition power. Monocular defocus curves were plotted for each patient and effective addition power was calculated as the dioptric difference between the distance and near inflection points of the defocus curve. Six biometry formulas (Haigis, Holladay, SRK/T, Hill RBF, Barrett Universal II, and Holladay 2) were used to predict the addition power at the spectacle plane. RESULTS: Mean effective addition power was 2.60 ± 0.29 D, with significant (P < .01) differences between the prediction methods. Significant differences were found between predicted and effective addition when the Holladay, SRK/T, Hill RBF, and Holladay 2 formulas were used. A moderate but significant correlation (r = 0.342, P = .033) was found with the Barrett formula, and this was also the method to show the least proportional bias with Bland-Altman analysis. CONCLUSIONS: The study demonstrates that the effective addition power can be predicted using the proposed simple clinical method derived using the Barrett Universal II formula. The proposed technique may have significant clinical value in screening for patients where ocular biometry may lead to aberrant addition power. [J Refract Surg. 2021;37(5):318-323.].

Visual function and subjective perception of vision after bilateral implantation of monofocal and multifocal IOLs: a randomized controlled trial.

PURPOSE: To examine monocular and binocular visual function and patient-reported outcomes after implantation of multifocal IOLs (mIOLs) or monofocal IOLs, using a rigorous series of clinical assessments. SETTING: BMI Southend Hospital, United Kingdom. DESIGN: Prospective, randomized, double-masked clinical trial. METHODS: One hundred patients were randomized for bilateral implantation of either a Bi-Flex 677MY mIOL or a Bi-Flex 677AB IOL and were assessed at 3 to 6 months (V1) and 12 to 18 months (V2). Primary outcomes included distance, intermediate, and near logarithm of the minimum angle of resolution (logMAR) visual acuities (VAs) and defocus curve profile assessment. Secondary outcomes included reading speed, contrast sensitivity (CS), and the subjective perception of quality of vision. RESULTS: Forty-seven subjects with monofocal IOL and 43 mIOL subjects completed the study. Uncorrected (mIOL: 0.10 ± 0.09 logMAR; IOL: 0.09 ± 0.11 logMAR) and corrected (mIOL: 0.04 ± 0.06 logMAR; IOL: 0.01 ± 0.07 logMAR) distance VAs were comparable (P > .05). Uncorrected near VA (mIOL: 0.23 ± 0.13 logMAR; IOL: 0.55 ± 0.20 logMAR, P < .001) and distance-corrected near VA (mIOL: 0.24 ± 0.13 logMAR; IOL: 0.54 ± 0.17 logMAR, P < .001) were significantly improved with mIOLs. There was no significant difference in distance-corrected intermediate VA (mIOL: 0.38 ± 0.13 logMAR; IOL: 0.39 ± 0.13 logMAR, P = .431). Defocus curves demonstrated an increased range-of-focus among mIOLs (mIOL: 4.14 ± 1.10 diopter [D]; IOL: 2.57 ± 0.77 D). Pelli-Robson CS was different at V1 (P < .001) but similar by V2 (P = .059). Overall satisfaction was high (>90%) in both groups for distance tasks whereas significantly different for near tasks (mIOL, 18.45 ± 16.53 logUnits; IOL, 55.59 ± 22.52 logUnits). CONCLUSIONS: Uncorrected near visual acuity was demonstrably better with mIOLs and there was greater subjective satisfaction with quality of near vision. Halos reported by the mIOL group were significant compared with the IOL group but did not show an adverse effect on overall satisfaction.

Clinical outcomes with a new trifocal intraocular lens.

PURPOSE: To evaluate visual and refractive outcomes, contrast sensitivity, and quality of vision after cataract surgery with the implantation of a new modality of trifocal intraocular lens (IOL). METHODS: This case series comprised 30 patients who had bilateral implantation of the AT.LISA tri 839 MP trifocal IOL after phacoemulsification for either cataract or refractive lens exchange surgery. Uncorrected (UDVA) and corrected monocular distance visual acuity (CDVA) using a logMAR chart, binocular uncorrected (UNVA) and corrected near visual acuity (CNVA) (40 cm and patients' preferred distance) using the Radner Reading Charts, distance-corrected intermediate visual acuity (DCIVA) (70 cm), a binocular defocus curve, contrast sensitivity (CS) with the Pelli-Robson test, and subjective quality of vision by a short questionnaire were evaluated at 1, 3, and 6 months postoperatively. RESULTS: At 6 months, mean values of 0.05 ± 0.07 and -0.02 ± 0.05 logMAR were obtained for monocular UDVA and CDVA, respectively. Mean values of 0.16 ± 0.07, 0.12 ± 0.07, and 0.16 ± 0.07 logRAD were obtained for binocular UNVA, CNVA, and DCIVA, respectively. Significant changes were only detected in monocular CDVA (p<0.01) and UDVA that improved between 3 and 6 months postoperatively (p = 0.01). A visual acuity level of 0.2 logRAD could be seen in binocular defocus curves between +1.00 and -3.00 D. At 6 months, mean photopic and mesopic CS were 1.52 ± 0.11 and 1.54 ± 0.11. Regarding the questionnaire, almost all patients were satisfied with their distance, intermediate, and near vision. Difficulties associated with photic phenomena decreased significantly over time. CONCLUSIONS: The AT.LISA trifocal IOL provides excellent uncorrected distance, intermediate, and near visual outcomes.

Evaluation of intraocular pressure at the end of cataract surgery.

PURPOSE: To assess the accuracy of estimating intraocular pressure (IOP) at the end of cataract surgery and to suggest a method of verifying this value. SETTING: University hospital in a suburban area. METHODS: Sixty-nine eyes having phacoemulsification cataract surgery without complications were studied. In stage 1, the surgeon estimated IOP using digital pressure at the end of cataract surgery while a second investigator checked the actual IOP using a handheld tonometer. The estimated and true values were compared. In a second group of patients, the IOP was measured at the end of surgery in 30 eyes using a specifically designed tonometer, the Ocular Kasaby Barraquer 20/30 (OKBT-20/30) (Ocular Instruments, Inc.). The true values were then measured using the handheld tonometer to verify the accuracy of the OKBT-20/30. RESULTS: In stage 1, 37.7% of the estimates were outside the "acceptable" IOP range of 10 mm Hg or higher to 30 mm Hg or lower. Accuracy of estimates decreased toward the extremes of IOP. This suggests that eyes with IOP values outside the acceptable range are likely to be left as such at the end of surgery. In stage 2, when the IOP was measured with the new instrument and rechecked with the electronic tonometer, 93.3% of eyes had an IOP within the reference range of 20 to 30 mm Hg; 62.3% of eyes had an IOP within this range when estimated. CONCLUSIONS: Because the digital estimate can be misleading, the OKBT-20/30 tonometer or a similar device should be used routinely to ensure each eye is left with a desirable IOP at the end of cataract surgery.

Functional vision with bilateral ReZoom and ReSTOR intraocular lenses 6 months after cataract surgery.

PURPOSE: To compare the visual outcomes in patients with bilateral implantation of AcrySof ReSTOR multifocal intraocular lenses (IOLs) (Alcon Laboratories) or ReZoom multifocal IOLs (Advanced Medical Optics) 6 months after cataract surgery. SETTING: Orsett and Southend Hospital, Essex, United Kingdom. METHODS: This study comprised patients who had uneventful bilateral cataract extraction with implantation of ReZoom (n = 50) or ReSTOR (n = 50) multifocal IOLs. Parameters analyzed included binocular uncorrected distance, intermediate, and near acuities; spectacle independence; subjective visual symptoms; and patient satisfaction. All parameters were evaluated 6 months after second-eye surgery. RESULTS: All patients had binocular uncorrected distance visual acuity of 20/32 or better; there was no statistically significant difference between the 2 groups. The mean binocular uncorrected near acuity was 20/26 (J1.22) in the ReSTOR group and 20/34 (J2.34) in the ReZoom group (P<.0001). The mean binocular uncorrected intermediate visual acuity was 20/42 and 20/34, respectively (P = .003). Patients in the ReZoom group reported greater satisfaction with intermediate vision (P = .04). No statistically significant difference was found in satisfaction with near vision. Eighty-six percent of ReSTOR patients and 70% of ReZoom patients did not wear glasses for daily activities; the overall satisfaction was not statistically significantly different between groups. There was no significant difference between groups in photic phenomena. CONCLUSIONS: The ReSTOR IOL provided better near vision and the ReZoom IOL better intermediate vision. Both multifocal IOLs gave excellent distance vision. Photic phenomena were comparable and clinically acceptable. ReSTOR patients had greater spectacle independence for near vision and ReZoom patients for intermediate vision. Overall spectacle independence was not statistically significantly different.