Intraoperative Aberrometry Research Articles

Intraoperative Aberrometry for IOL Selection

To review the clinical use, advantages, and potential limitations of intraoperative aberrometry (IA) and its application in cataract surgery in the normal, astigmatic, and atypical eye. The use of IA is similar to traditional preoperative biometry methods for intraocular lens (IOL) determination in short and normal eyes. The use of IA resulted in equivalent outcomes to modern formulas with optimized axial lengths in long eyes and exceeded traditional formulas. Improved outcomes compared to traditional methods were noted with the use of IA when used for both astigmatism correction and IOL determination in patients with a history of corneal refractive surgery. The greatest value in using IA is with atypical eyes. There is a surgeon learning curve with this technology to allow for optimal, consistent, and reproducible results. Despite the increasing popularity of IA, the number of published studies on this technology is limited.

Disruptive Innovation and Refractive IOLs: How the Game Will Change With Adjustable IOLs.

The light-adjustable lens is the first Food and Drug Administration (FDA)-approved product from an entirely new category of intraocular lenses (IOLs). The 3-piece foldable silicone light-adjustable lens is implanted through a small incision after phacoemulsification. A slit-lamp-based digital light delivery device is used to adjust and then lock-in the IOL power during the first postoperative month. Up to 4.5 diopters (D) of cylindrical or spherical adjustment can be achieved. This should offer significant advantages in difficult IOL power calculation cases, such as postrefractive eyes. In addition to achieving better refractive accuracy, an adjustable IOL will now allow patients to test and elect a different refractive target postoperatively. This paradigm shift will change how cataract patients choose their refractive objectives, and how ophthalmologists will be able to achieve them. For example, adjustable IOLs may increase the popularity of pseudophakic monovision and bilateral same-day sequential surgery. For those electing adjustable IOL, preoperative patient counseling will change and certain pre- and intraoperative technologies, such as intraoperative aberrometry and digital astigmatic axis marking, would become superfluous.

Intraoperative Aberrometry Versus Preoperative Biometry for IOL Power Selection After Radial Keratotomy: A Prospective Study

To compare the accuracy of Optiwave Refractive Analysis (ORA) intraoperative aberrometry (Alcon Laboratories, Inc., Fort Worth, TX) with preoperative biometry in predicting residual refractive error after cataract surgery in eyes that underwent radial keratotomy. This was a prospective consecutive case series of patients with cataract and prior radial keratotomy. Each patient underwent a preoperative intraocular lens (IOL) power calculation using partial coherence interferometry (IOLMaster version 5; Carl Zeiss Meditec, Jena, Germany). For each eye, the Barrett True-K formula was used to select an IOL targeting emmetropia. Residual refractive error was predicted preoperatively using the SRK/T, Hoffer Q, Haigis, and Holladay formulas 1 and 2, and the ORA intraoperatively. Between 8 and 12 weeks after cataract extraction with IOL implantation, the postoperative refraction was compared with the preoperative and intraoperative predictions. The study comprised 52 eyes of 34 patients. The median absolute errors associated with each method were as follows: Barrett True-K formula (0.34), ORA aberrometer (0.53), and SRK/T (0.54), Hoffer Q (0.51), Haigis (0.54), SRK/T (0.57), and Holladay formulas 1 and 2 (0.44) (P = .08). The proportion of patients within ±0.50 diopters of the predicted error was 63.5%, 48.1%, 44.2%, 48.1%, 53.8%, 36.5%, and 57.7%, respectively (P = .03). No statistically significant difference was observed in the number of eyes with hyperopic outcomes (P = .68). In eyes with prior radial keratotomy surgery, the ORA aberrometer performance was similar to the Barrett True-K formula and all of the other established formulas, with no significant difference between median absolute error and mean absolute error. The Barrett True-K formula produced significantly more eyes within ±0.50 diopters than the SRK/T, Hoffer Q, and Holladay 1 formulas. [J Refract Surg. 2019;35(10):656-661.].

Evaluating the relative value of intraoperative aberrometry versus current formulas for toric IOL sphere, cylinder, and orientation planning

To retrospectively review toric intraocular lens (IOL) outcomes and compare actual results to those expected from preoperative calculations and intraoperative aberrometry (IA) in normal eyes. Carolina Eyecare Physicians, Mt. Pleasant, South Carolina, USA. Retrospective data review of earlier clinical trial data. Toric IOL planning data and results were obtained from two previous clinical studies of normal eyes receiving toric IOL implants. Back-calculation techniques were used to estimate expected residual refractive sphere and cylinder for preoperative and IA calculations. Toric IOL planning data and clinical outcomes for 132 eyes receiving two different toric IOLs were analyzed. The mean spherical equivalent refractions expected with preoperative planning and IA were not statistically significantly different (P=.44), but a higher percentage of eyes within ±0.50 D of the intended spherical refraction was expected with preoperative calculations (P=.05). The mean expected residual refractive astigmatism based on preoperative calculations was significantly lower than for IA (P<.001), with more eyes expected to have 0.50 D or less of residual refractive astigmatism. The use of current-generation formulas for sphere power and toric IOL planning in normal eyes seems sufficient to produce clinical outcomes with toric IOLs that are as good or better than those achieved using IA.

Retrospective analysis of an intraoperative aberrometry database: a study investigating absolute prediction in eyes implanted with low cylinder power toric intraocular lenses.

PurposeTo evaluate the spherical equivalent outcomes of intraoperative aberrometry (IA) power calculations compared with the surgeons’ preoperative power calculations in eyes implanted with AcrySof® IQ T3 intraocular lenses (IOLs).Patients and methodsWe assessed data collected by an IA system from multiple centers in the United States. Data was from patients who had undergone cataract extraction by phacoemulsification with the use of the Optiwave Refractive Analysis System and whose eyes had been implanted with model SN6AT3 (1.5 diopter [D] at IOL plane) aspheric lenses. The analysis was performed in 2 stages: hypothesis generation and confirmatory testing. Confirmatory endpoints were a comparison of absolute prediction errors for IA for the implanted IOL versus preoperative formula power calculations.DesignRetrospective analysis of preoperative, intraoperative, and postoperative data concerning eyes implanted with model SN6AT3 (1.5 D) aspheric lenses from the AnalyzOR™ database.ResultsMean absolute IA prediction error was significantly lower than preoperative prediction error (paired difference: −0.06 D; p<0.0001); this was mirrored by the median paired difference of −0.04 D (p<0.0001). For eyes where the power of the implanted IOL differed from the power of the preoperatively planned lens, mean and median paired differences in prediction errors were greater: −0.13 D (p<0.0001) and −0.15 D (p<0.0001), respectively. The percentage of eyes with prediction error ≤0.50 D was significantly higher with IA (83.4%, n=5388/6460) than with the preoperative formula (76.5%, n=4942/6460, p<0.0001). When the powers of the implanted IOL and the preoperatively planned lens were different, the percentage of eyes with prediction error ≤0.50 D was 83.3% (2155/2587) for IA and 68.8% (1781/2587, p<0.0001) for the preoperative formula.ConclusionIA produces more accurate spherical equivalent outcomes for eyes implanted with a low toric IOL than the preoperative formulas.

Clinical comparison of speculum's influence on intraoperative aberrometry reading.

PurposeThe aim of this study was to evaluate the influence of four different types of speculums on aberrometry reading (OPD SCAN III [OPD]) and on intraoperative aberrometry reading (optiwave response analyzer, ORA).Patients and methodsThis prospective, controlled, comparative study of consecutive cases included the evaluation of five eyes of five patients with monofocal intraocular lens (IOL) implantation. Seventeen measures were performed on each patient: for each speculum, there were two measurements on the OPD and another two on ORA with four different types of blepharostats. A control measure was performed on the without blepharostat in the dominant eye of each patient, therefore totalizing 85 measurements. The measures with the blepharostats were as follows: without pressure (WF) or passive measure and after pressure (AF) or active measure to close the eye. The speculum used in all patients was as follows: open-edged wire (Barraquer); threaded with open blade (Lieberman), with 21 mm aperture; wired with solid blade (Barraquer); and threaded with solid blade (Lieberman) with 21 mm opening. An evaluation of the objective refractive data from the OPD and ORA and the corneal astigmatism from the OPD was performed.ResultsSpherical equivalent (SE) of the OPD with the use of blepharostat compared to the OPD without speculum presented only 37.5% of results without statistical significance. Regarding the SE of ORA with speculum usage, compared to the OPD without blepharostat, only 12.5% were not significant. Regarding the accuracy of the ORA refractive axis with the use of blepharostats, all results presented statistical significance.ConclusionThus, in the present study, we reached the conclusion between the studied blepharostats that the most suitable for use in the aphakic and pseudophakic capture of the ORA is the open blade threaded blepharostat (Lieberman).

Clinically relevant differences in the selection of toric intraocular lens power in normal eyes: preoperative measurement vs intraoperative aberrometry.

Purpose: To assess the value of intraoperative aberrometry (IA) in determining toric intraocular lens (IOL) power in eyes with no previous ocular surgery.Patients and methods: This was a retrospective data review at one US clinical site of eyes that underwent uncomplicated cataract surgery with toric IOL implantation where standard preoperative and IA measurements were available. Calculated IOL sphere and cylinder powers and orientation were compared based on the measurement method and the postoperative refraction, using both actual and simulated (back-calculated) results. Comparisons were between the surgeon’s preoperative calculations, IA measurements, the actual IOL implanted and results from the Barrett toric calculator.Results: There was no significant difference (p>0.7) in the number of eyes expected to have, or having, a spherical equivalent refraction within 0.50D of the target between Actual (92%), IA (93%) or Preoperative calculation results (86%). The percentage of eyes with expected residual refractive astigmatism ≤0.50D was significantly higher for the IA vs Preoperative calculations (75% vs 53%, p<0.01). There was no significant difference in expected results between the Actual, IA and Barrett toric calculations (p>0.65).Conclusion: Modern IOL calculations for sphere produced results comparable to those achieved with IA. The value of IA in determining IOL cylinder power and orientation was more evident when comparing expected results between IA and a preoperative method based on measured total corneal astigmatism than when comparing to expected results from the Barrett toric calculator.

Correcting astigmatism at the time of cataract surgery: Toric IOLs and corneal relaxing incisions planned with an image-guidance system and intraoperative aberrometer versus manual planning and surgery

To compare the outcomes of the combination of an image-guided system and intraoperative aberrometer with the surgeon's standard of care in correcting astigmatism using toric intraocular lenses (IOLs) or corneal incisions. Single site in United States. Prospective case series. Contralateral eyes of patients having uncomplicated bilateral cataract surgery and astigmatism correction were randomly assigned to Group A or Group B. Group A received the surgeon's preferred standard of care. Group B had preoperative planning using an image-guidance system (VERION), intraoperative aberrometry (ORA System with VerifEye+), and femtosecond laser-assisted cataract surgery. The primary endpoint was the residual refractive astigmatism at 3months. Thirty-eight eyes were treated with toric IOLs and 40 eyes with corneal astigmatic incisions. On average, toric IOLs resulted in almost 0.25 diopter (D) less cylinder than corneal astigmatic incisions (P<.01), with no difference between groups (P=.41). There was no statistically significant difference in the mean spherical equivalent refraction by group (P=.51). At 3months, the IOL in 4 eyes (11%) (2 in Group A and Group B each) was more than 10 degrees of absolute orientation from the intended orientation. The mean keratometry was 0.16 D higher with the image-guided system compared with optical biometry (Lenstar). The vector difference between the 2 measurements was 0.5 D or lower in all eyes. The combined use of an image-guided system and intraoperative aberrometer did not significantly improve outcomes compared with the surgeon's standard of care. Based on keratometry, there was good agreement in corneal astigmatism measurements between the image-guided system and the optical biometer.

Intraoperative aberrometry versus preoperative biometry for intraocular lens power selection in short eyes

To compare the accuracy of preoperative biometry-based formulas to intraoperative aberrometry (IA) with respect to predicting refractive outcomes after cataract surgery in short eyes. Private practice and community-based ambulatory surgery center. Retrospective consecutive case series. Eyes with an axial length (AL) shorter than 22.1mm underwent cataract extraction and intraocular lens (IOL) implantation. The predicted residual refractive error was calculated preoperatively using Hoffer Q, Holladay 2, Haigis, Barrett Universal II, and Hill-RBF formulas and intraoperatively using IA. The postoperative spherical equivalent (SE) was compared with the predicted SE to evaluate the accuracy of each aforementioned method. Fifty-one eyes from 38 patients met criteria to be included in the analysis. Without optimizing the formulas specifically for short eyes, the mean numerical errors (MNEs) associated with Hoffer Q, Holladay 2, Haigis, Barrett Universal II, Hill-RBF, and IA were -0.08 (95% confidence interval [CI], -0.30 to 0.13), -0.14 (95% CI, -0.35 to 0.07), +0.26 (95% CI, 0.05 to 0.47), +0.11 (95% CI, -0.10 to 0.32), +0.07 (95% CI, -0.14 to 0.28), and +0.00 (95% CI, -0.21 to 0.21), respectively (P<.001). The proportion of eyes within ±0.5 diopter (D) of the predicted SE were 49.0%, 43.1%, 52.9%, 52.9%, 60.8%, and 58.8%, respectively (P=.06). The prediction outcomes from IA were statistically better than Haigis, but not other formulas. When formula and IA predictions differed by 0.5 D or more, IA's ability to recommend a more emmetropic outcome was no better than chance (50%). Intraoperative aberrometry is not significantly different from the best preoperative biometry-based methods available for IOL power selection in short eyes.

Utilizing intraoperative aberrometry and digital eye tracking to develop a novel nomogram for manual astigmatic keratotomy to effectively decrease mild astigmatism during cataract surgery.

PURPOSE:The purpose of the study is to develop a novel nomogram and validate with a retrospective comparative study for manual astigmatic keratotomy (MAK) with the assistance of intraoperative aberrometry (Optiwave Refractive Analysis [ORA]) and digital eye tracking (VERION) in mild astigmatic correction enhancement.SETTING:The study was conducted in Honolulu, Hawaii.DESIGN:This was a single-surgeon comparative study with retrospective data collection.METHODS:Sixty consecutive adult cataract surgery cases with regular astigmatism of 1.25 D or less were included for study from April 2016 to April 2017. VERION was used preoperatively in all cases. MAK was performed before phacoemulsification according to the surgeon's own nomogram. ORA then was utilized to obtain the axis and remaining cylinder power after phacoemulsification and intraocular lens implant implantation. MAK extension was performed for eyes with 1 D or more of remaining cylinder. Extensions were carried out slowly and slightly until the amount of cylinder was 1½ D or less under ORA. The mean degrees of extension plus the original MAK plan were calculated to develop the new nomogram. Sixty consecutive similar cases by the same surgeon using the surgeon's nomogram without using ORA/VERION for enhancement were reviewed from April 2015 to April 2016 for comparison. All patients included in this study signed the consent form.RESULTS:Using Alpins vector analysis for comparison, the proportion of patients with cylinder <0.5 D 3 months postoperatively was 87% in the ORA/VERION group compared to 70% in the non-ORA/VERION group (P < 0.05). Better than 20/25 best-corrected visual acuity was achieved more in the ORA/VERION group compared to non-ORA/VERION group.CONCLUSIONS:This novel nomogram developed by the surgeon may have better outcomes than the old surgeon's own nomogram. Further prospective control study is needed to validate the efficacy. If validated, those surgeons who do not have ORA/VERION can hopefully use this nomogram with greater success.

Biometry in cataract surgery: a review of the current literature.

To review the literature in 2017 and 2018 pertaining to biometry for cataract surgery and report pertinent findings. New devices using swept-source ocular coherence tomography can measure axial length in dense cataracts more frequently than common biometers. Computer-assisted registration may be superior to intraoperative aberrometry for toric intraocular lens (IOL) placement. Soft contact lenses may not require removal as long before biometry as previously thought. The Barrett Universal II IOL formula has been found to perform well at all axial lengths. New swept-source ocular coherence tomography biometers are more frequently successful at measuring axial length in dense cataracts which promises to improve refractive outcomes. Accuracy in toric IOL placement is likely to increase with improved devices. It may not be necessary to have patients remove soft contact lens any more than 2 days prior to biometry. The Barrett Universal II IOL formula may be used confidently for most eyes. Advancements acknowledged, purchasing new equipment will not be necessary for all surgeons.

A large retrospective database analysis comparing outcomes of intraoperative aberrometry with conventional preoperative planning

To evaluate differences between the absolute prediction error using an intraoperative aberrometry (IA) device for intraocular lens (IOL) power determination versus the error that would have resulted if the surgeon's preoperative plan had been followed. Multiple centers in the United States. Retrospective analysis of data collected using an IA device. The database information was limited according to predetermined inclusion/exclusion criteria. Primary endpoints included the difference between mean and median absolute prediction error with IA use versus preoperative calculation, and the percentage of cases were compared when the prediction error was 0.5 diopters (D) or less. A total of 32 189 eyes were analyzed. The IA mean absolute prediction error was lower than the preoperative calculation, 0.30 D ± 0.26 (SD) versus 0.36±0.32 D (P<.0001). The aberrometry absolute median prediction error was lower than the preoperative calculation, 0.24 D versus 0.29 D (P<.0001). There was a significantly greater percentage of eyes with an aberrometry absolute prediction error of 0.5 D or less than eyes with a preoperative absolute prediction error of 0.5 D or less (26 357 [81.9%] of 32 189 vs. 24 437 [75.9%] of 32 189, P<.0001). In addition, in those cases in which power of the IOL implanted was different than the preoperatively planned IOL power, significantly more eyes had an aberrometry absolute prediction error of 0.5 D or less (10 385 [81.3%] of 12 779 vs. 8794 [68.8%] of 12 779, P<.0001). In a database of more than 30 000 eyes, calculations incorporating IA outperformed preoperative calculations. The difference was more pronounced in those cases in which the preoperatively planned IOL power was different than the power of the IOL implanted.

Factors Associated With Residual Astigmatism After Toric Intraocular Lens Implantation Reported in an Online Toric Intraocular Lens Back-calculator.

To evaluate factors associated with residual astigmatism after toric intraocular lens implantation based on data from an online toric intraocular lens (IOL) back-calculator. This was a retrospective data review of an online toric IOL back-calculator, which allows users to input preoperative toric planning information and postoperative lens orientation and refractive results. These data were used to determine the optimal orientation of the IOL to minimize residual refractive astigmatism. Aggregate data were extracted from this calculator to investigate factors associated with relative magnitudes of residual astigmatic refractive error after implantation of toric IOLs. A total of 3,159 validated records with an average reported postoperative refractive astigmatism of 1.85 diopters (D) were analyzed; 566 included data allowing calculation of surgically induced astigmatism. The relative magnitude of reported residual astigmatism appeared similar whether a femtosecond laser system was used or not. Significant differences relative to the use of intraoperative aberrometry were observed, as were differences by toric calculator. Higher measured surgically induced astigmatism was most associated with higher levels of reported residual astigmatism. A significant potential decrease in the mean refractive astigmatism was expected with IOL reorientation; in 1,416 cases (44.8%), the expected residual refractive astigmatism after lens reorientation was less than 0.50 D, with a mean reduction of 56% ± 31%. When present after cataract surgery, higher levels of residual refractive astigmatism were most associated with large differences in measured preoperative to postoperative keratometry. To a lesser degree, intraoperative aberrometry was associated with lower levels. [J Refract Surg. 2018;34(6):366-371.].

Clinical outcomes with distance-dominant multifocal and monofocal intraocular lenses in post-LASIK cataract surgery planned using an intraoperative aberrometer.

ImportanceStudies evaluating the clinical benefits of intraoperative aberrometry (IA) in cataract surgery are limited.BackgroundThe study was designed to determine whether IA improved clinical outcomes of post‐laser in situ keratomileusis (LASIK) cataract surgery with different intraocular lenses (IOLs) implanted.DesignA retrospective chart review of clinical outcomes from one surgeon at one surgical centre was conducted. It included post‐LASIK cataract surgeries where IA was used for the confirmation of IOL power, with either a distant‐dominant multifocal IOL or a monofocal IOL implanted.ParticipantsRecords for 44 eyes of 31 patients were analysed.MethodsDifferences in visual acuity (VA) and refractions by lens type were compared, and the effects of IA were evaluated.Main Outcome MeasuresUncorrected distance VA and the percentage of eyes with a spherical equivalent refraction within 0.5D of the intended correction were the primary outcome measures.ResultsThere was no statistically significant difference in the percentage of eyes with uncorrected distance VA of 20/25 or better between IOL groups (P = 0.41). More eyes in the multifocal group had a refraction within 0.50D of intended (P = 0.03). In 39% of cases, the preoperative and IA power calculations suggested the same IOL power. When not equal, the IA results were not significantly more likely to be ‘best’ (P = 0.08).Conclusions and RelevanceResults suggest that a history of previous LASIK is not a contraindication to use of distant‐dominant multifocal IOLs. IA did not appear to improve clinical outcomes in post‐LASIK eyes, although a positive trend was evident.

Preoperative measurement vs intraoperative aberrometry for the selection of intraocular lens sphere power in normal eyes.

PurposeThis study aimed to assess the value of intraoperative aberrometry (IA) in determining the intraocular lens (IOL) sphere power in eyes with no previous ocular surgery.Patients and methodsWe conducted a retrospective review of patients who underwent uncomplicated cataract surgery where standard preoperative (Preop) measurements and IA were performed. Calculated IOL sphere powers and postoperative refractions, both actual and theoretical, were compared based on the measurement method and lens type; lens types included multifocal, toric and aspheric single-vision non-toric IOLs.ResultsA total of 160 eyes of 112 patients were analyzed. The Preop lens power calculated was the same as the IA lens power 46% of the time, though this percentage was lower for multifocal IOLs. Across all lens types, there was a statistically significant bias (chi-square test, P<0.01) toward the IA method suggesting a lower powered lens. Actual postoperative refractive errors were not statistically significantly different when categorized by measurement method. Calculated errors by measurement method showed no statistically significant differences in expected outcomes. There were 63 cases where the Preop calculation and the intraoperative aberrometer calculation differed by 0.5 D. In 56% (35/63) of these cases, the IA result was a better option, and in 44% (28/63) of cases, the Preop calculation was better; this was not statistically significantly different from random expectation (50/50, P=0.53). In the three cases where calculated powers differed by 1.5 D, there appeared to be a positive effect of adjusting the Preop power toward the IA power.ConclusionThe use of IA for the determination of sphere power in eyes with no previous ocular surgery does not appear to improve overall expected clinical outcomes, but it may be helpful in cases where the difference between IA and Preop calculations is high.

Toric outcomes: Computer-assisted registration versus intraoperative aberrometry

To compare refractive outcomes of intraoperative computer-assisted registration and intraoperative aberrometry for the reduction of cylinder during toric intraocular lens (IOL) placement. Bowie Vision Institute, Bowie, Maryland, USA. Prospective randomized case series. The patients were divided into 2 groups that had toric IOL implantation after phacoemulsification. The intraoperative computer-assisted registration group (Group 1) had preoperative toric calculations. The aberrometry group (Group 2) was guided by a vergence formula and intraoperative pseudophakic cylindrical measurements to determine the final IOL power and intended orientation. The primary outcome measure was the mean postoperative remaining refractive astigmatism, and it was compared with the predicted amount of cylindrical correction with the IOL. Fifty-two patients (104 eyes) had sequential cataract surgery. The mean amount of cylinder correction was 1.60 diopters (D)±0.70 (SD) (range 0.75 to 3.08 D) in Group 1 and 1.74±0.79 D (range 0.72 to 3.08 D) in Group 2. The mean remainingrefractive astigmatism was -0.29±0.22 D in Group 1 and -0.46±0.25 D in Group 2 (P=.0003). A difference vector of 0.1 @ 87 degrees (0.31 D arithmetic mean) was calculated in Group 1 and 0.0 @ 82 degrees (0.44 D arithmetic mean) in Group 2. The correction index was 1.03 in Group 1 and 0.95 in Group2. Intraoperative markerless computer-assisted registration and biometric guidance summarily yielded less remaining refractive cylinder than toric IOL placement guided by intraoperative aberrometry.

Intraoperative aberrometry versus preoperative biometry for intraocular lens power selection in axial myopia

To compare the accuracy of intraoperative wavefront aberrometry (ORA) and the Hill-radial basis function (RBF) formula with other formulas based on preoperative biometry in predicting residual refractive error after cataract surgery in eyes with axial myopia. Private practice, Harrisburg, Pennsylvania, USA. Retrospective consecutive case series. Eyes with an axial length (AL) greater than 25.0mm had cataract extraction with intraocular lens implantation. For each eye, the 1-center Wang-Koch AL-optimized Holladay 1formula was used to select an IOL targeting emmetropia. Residual refractive error was predicted preoperatively using theSRK/T, Holladay 1 and 2, Barrett Universal II, and Hill-RBF formulas and intraoperatively using wavefront aberrometry. The postoperative refraction was compared with the preoperative and intraoperative predictions. The study comprised 37 patients (51 eyes). The mean numerical errors ± standard error associated with using the SRK/T, Holladay 1, AL-optimized Holladay 1, Holladay 2, Barrett Universal II, and Hill-RBFformulas and intraoperative wavefront aberrometry were 0.20±0.06 diopters (D), 0.33±0.06 D, -0.02±0.06 D, 0.24±0.06 D, 0.19±0.06 D, 0.22±0.06 D, and 0.056±0.06D, respectively (P<.001). The proportion of patients within ±0.5 D of the predicted error was 74.5%, 62.8%, 82.4%, 79.1%, 73.9%, 76.7%, and 80.4%, respectively (P=.090). Hyperopic outcomes occurred in 70.6%, 76.5%, 49.0%, 74.4%, 76.1%, 74.4%, and 45.1% of the eyes, respectively (P=.007). Intraoperative wavefront aberrometry was better than all formulas based on preoperative biometry and as effective as the AL-optimized Holladay 1 formula in predicting residual refractive error and reducing hyperopic outcomes. The Hill-RBF formula's performance was similar to that of the fourth-generation formulas.

New Developments in Cataract Surgery

Recent technological innovations in cataract surgery have made the procedure even more precise and safe and the odds of having a highly satisfied patient even higher. These innovations include visualisation systems - such as intraoperative aberrometry - which are particularly helpful when it comes to implanting toric IOLs, where even a slight rotation or misalignment can significantly reduce the postoperative visual quality. Another way to ensure the exact positioning of a toric IOL is to create a mark by making an intrastromal incision using the femtosecond laser. The latter technology has increased the precision of capsulotomy and other steps of the operation and has been successfully employed in patients with a challenging clinical profile, including paediatric and hypermature cataracts. The femtosecond laser, however, induces an increase in intraocular prostaglandins, which can lead to miosis. Applying topical NSAIDs before starting surgery has proved to be effective in coping with the consequences of the increase in prostaglandins. Good vision without using glasses for near, intermediate and far distances remains a goal for many patients. IOLs with extended depths of focus (EDOF) technology can provide this comfort - to some but not all patients. An intraocular sensor, Eyemate, that is implanted during cataract surgery, enables the glaucoma patient to check his or her IOP at any time and improves the management of glaucoma and its main risk factor, elevated IOP. Several methods - drugs or nutritive agents - are said to prevent cataractogenesis. These studies have probably to be taken with the proverbial grain of salt.

Update on optical biometry and intraocular lens power calculation

Intraocular lens (IOL) power calculation is the single most important determinant of functionally improved result of a technically precise cataract surgery. We have discussed recent advances in the field of optical biometry and IOL power calculation formulae as a means to achieve better postoperative visual outcome. The use of automated optical biometry device, the current 'gold standard' of IOL power calculation, dates back to 1999. We have highlighted the evolution of newer optical biometry devices and the technology they are based on, and their advantages and limitations. We have done technical comparison of contemporary biometers and have included contextual current review of literature. We have described newer generation IOL power formulae, IOL power calculation in high to extreme myopia, toric calculators and intraoperative aberrometry, and concluded our discussion with a note on future prospects of IOL power calculation.

Optimizing outcomes with toric intraocular lenses.

Toric intraocular lenses (IOLs) are the procedure of choice to correct corneal astigmatism of 1 D or more in cases undergoing cataract surgery. Comprehensive literature search was performed in MEDLINE using “toric intraocular lenses,” “astigmatism,” and “cataract surgery” as keywords. The outcomes after toric IOL implantation are influenced by numerous factors, right from the preoperative case selection and investigations to accurate intraoperative alignment and postoperative care. Enhanced accuracy of keratometry estimation may be achieved by taking multiple measurements and employing at least two separate devices based on different principles. The importance of posterior corneal curvature is increasingly being recognized in various studies, and newer investigative modalities that account for both the anterior and posterior corneal power are becoming the standard of care. An ideal IOL power calculation formula should take into account the surgically induced astigmatism, the posterior corneal curvature as well as the effective lens position. Conventional manual marking has given way to image-guided systems and intraoperative aberrometry, which provide a mark-less IOL alignment and also aid in planning the incisions, capsulorhexis size, and optimal IOL centration. Postoperative toric IOL misalignment is the major factor responsible for suboptimal visual outcomes after toric IOL implantation. Realignment of the toric IOL is needed in 0.65%–3.3% cases, with more than 10° of rotation from the target axis. Newer toric IOLs have enhanced rotational stability and provide precise visual outcomes with minimal higher order aberrations.