Performance of IOL calculation formulas that use measured posterior corneal power in eyes following myopic laser vision correction

PURPOSE

To compare the predictive accuracy of the biometer-embedded Barrett True-K TK and new total corneal power methods of intraocular lens (IOL) power calculation in eyes with prior laser vision correction (LVC) for myopia.

SETTING

Academic clinical practice.

DESIGN

Retrospective case series.

METHODS

IOL power formulas were assessed using measurements from a swept-source optical coherence biometer. Refractive prediction errors were calculated for the Barrett True-K TK, EVO 2.0, Pearl-DGS, and HofferQST, which use both anterior and posterior corneal curvature measurements. These were compared with the Shammas, Haigis-L, Barrett True-K No History (NH), optical coherence tomography, and 4-formula average (AVG-4) on the ASCRS postrefractive calculator, and to the Holladay 1 and 2 with non linear axial length regressions (H1- and H2-NLR).

RESULTS

The study comprised 85 eyes from 85 patients. Only the Barrett True-K TK and EVO 2.0 had mean numerical errors that were not significantly different from 0. The EVO 2.0, Barrett True-K TK, Pearl-DGS, AVG-4, H2-NLR, and Barrett True-K NH were selected for further pairwise analysis. The Barrett True-K TK and EVO 2.0 demonstrated smaller root-mean-square absolute error compared with the Pearl-DGS, and the Barrett True-K TK also had a smaller mean absolute error than the Pearl-DGS.

CONCLUSIONS

The Barrett True-K TK and EVO 2.0 formulas had comparable performance to existing formulas in eyes with prior myopic LVC.

Effect of spherical aberration on visual acuity and depth of focus in pseudophakic eyes

PURPOSE

To assess the performance of 4 intraocular lenses (IOLs) in various spherical aberration (SA) conditions, using the VAO adaptive optics simulator.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

DESIGN

Prospective case series.

METHODS

Distance-corrected visual acuities at distance (CDVA), intermediate (DCIVA), and near (DCNVA) were measured in 42 dilated pseudophakic eyes at baseline and with ocular SA ranging from -0.4 to +0.4 μm in increments of 0.2 μm (6.0-mm pupil). 4 IOL types were assessed: monofocal IOLs with zero-SA, enhanced-monofocal, extended depth-of-focus (EDOF), and continuous range-of-vision.

RESULTS

Compared with SA = 0 μm, significant changes (all P < .05) were: (1) zero-SA monofocal IOLs' DCNVA at high contrast improved by 0.13 logMAR with SA = -0.4 μm and worsened by 0.09 and 0.10 logMAR with SA = +0.2 and +0.4 μm, respectively. DCNVA at low contrast worsened by 0.09 logMAR with SA = +0.4 μm; and (2) with SA = -0.4 μm, the enhanced monofocal IOL lost 0.06 logMAR of CDVA at high contrast and gained 0.09 logMAR of DCNVA at low contrast. There were no significant changes from SA = 0 μm for EDOF and continuous range-of-vision IOLs.

CONCLUSIONS

Zero-SA and EDOF IOLs were the most and least sensitive to SA modulation, respectively. In perfect optical systems where all the optical elements are aligned, induction of targeted amounts of negative SA improved the depth of focus of some IOL types. No benefit was found with positive SA.

Outcomes of peripheral corneal relaxing incisions for residual astigmatism in patients after cataract surgery

PURPOSE

To evaluate the outcomes of peripheral corneal relaxing incisions (PCRIs) for correcting residual astigmatism in eyes after cataract surgery.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

DESIGN

Retrospective case series.

METHODS

Retrospectively, we reviewed all consecutive cases that had previous cataract surgery and subsequent PCRIs by 1 surgeon. The PCRI length was determined according to a nomogram based on age and manifest refractive astigmatism. Visual acuity and manifest refractive astigmatism before and after the PCRIs were compared. Vector analysis was performed, and net refractive changes along the incision meridian were calculated.

RESULTS

Criteria were met by 111 eyes. After the PCRIs, mean uncorrected visual acuity was significantly improved, and the percentage of eyes with uncorrected distance visual acuity of ≥20/20 increased significantly by 36%; the mean refractive astigmatism magnitude decreased significantly, and the percentages of eyes with refractive cylinder of ≤0.25 diopters (D) and ≤0.50 D increased significantly by 63% and 75%, respectively (all P < .05). The vector magnitude difference between pre- and post-operative refractive astigmatism was 0.88 ± 0.38 D. The postoperative refractive astigmatism had significantly smaller centroid and variance values than the preoperative refractive astigmatism ( P < .05).

CONCLUSIONS

PCRIs are an effective approach for correcting low amounts of residual astigmatism in patients after cataract surgery.

Efficacy of segmented axial length and artificial intelligence approaches to intraocular lens power calculation in short eyes

PURPOSE

In short eyes, to compare the predictive accuracy of newer intraocular lens (IOL) power calculation formulas using traditional and segmented axial length (AL) measurements.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas and East Valley Ophthalmology, Mesa, Arizona.

DESIGN

Multi-center retrospective case series.

METHODS

Measurements from an optical biometer were collected in eyes with AL <22 mm. IOL power calculations were performed with 15 formulas using 2 AL values: (1) machine-reported traditional AL (Td-AL) and (2) segmented AL calculated with the Cooke-modified AL nomogram (CMAL). 1 AL method and 7 formulas were selected for pairwise analysis of mean absolute error (MAE) and root mean square absolute error (RMSAE).

RESULTS

The study comprised 278 eyes. Compared with the Td-AL, the CMAL produced hyperopic shifts without differences in RMSAE. The ZEISS AI IOL Calculator (ZEISS AI), K6, Kane, Hill-RBF, Pearl-DGS, EVO, and Barrett Universal II (Barrett) formulas with Td-AL were compared pairwise. The ZEISS AI demonstrated smaller MAE and RMSAE than the Barrett, Pearl-DGS, and Kane. K6 had a smaller RMSAE than the Barrett formula. In 73 eyes with shallow anterior chamber depth, the ZEISS AI and Kane had a smaller RMSAE than the Barrett.

CONCLUSIONS

ZEISS AI outperformed Barrett, Pearl-DGS, and Kane. The K6 formula outperformed some formulas in selected parameters. Across all formulas, use of a segmented AL did not improve refractive predictions.

A Mouse Model for Corneal Neovascularization by Alkali Burn

Corneal neovascularization (CoNV), a pathological form of angiogenesis, involves the growth of blood and lymph vessels into the avascular cornea from the limbus and adversely affects transparency and vision. Alkali burn is one of the most common forms of ocular trauma that leads to CoNV. In this protocol, CoNV is experimentally induced using sodium hydroxide solution in a controlled manner to ensure reproducibility. The alkali burn model is useful for understanding the pathology of CoNV and can be extended to study angiogenesis in general because of the avascularity, transparency, and accessibility of the cornea. In this work, CoNV was analyzed by direct examination under a dissecting microscope and by immunostaining flat-mount corneas using anti-CD31 mAb. Lymphangiogenesis was detected on flat-mount corneas by immunostaining using anti-LYVE-1 mAb. Corneal edema was visualized and quantified using optical coherence tomography (OCT). In summary, this model will help to advance existing neovascularization assays and discover new treatment strategies for pathologic ocular and extraocular angiogenesis.

Comparison of Keratoconus Specific to Standard IOL Formulas in Patients With Keratoconus Undergoing Cataract Surgery

PURPOSE

To assess the performance of multiple intraocular lens (IOL) formulas in eyes with keratoconus.

METHODS

Eyes with stable keratoconus scheduled for cataract surgery with biometry measurements on the Lenstar LS900 (Haag-Streit) were included. Prediction errors were calculated using 11 different formulas, including two with keratoconus modifiers. Primary outcomes compared standard deviations, mean and median numerical errors, and percentage of eyes within diopter (D) ranges across all eyes with subgroup analysis according to anterior keratometric values.

RESULTS

Sixty-eight eyes from 44 patients were identified. In eyes with keratometric values less than 50.00 D, prediction error standard deviations ranged from 0.680 to 0.857 D. Percentages of eyes within ±0.50 D of target ranged from 57.89% to 73.68% with no statistical differences among formulas. In eyes with a keratometric value of more than 50.00 D, prediction error standard deviations ranged from 1.849 to 2.349 D and were not statistically different with heteroscedastic analysis; percentages of eyes within ±0.50 D of target ranged from 0% to 18.18% with no statistical differences among formulas. Only keratoconus-specific formulas (Barrett-KC and Kane-KC) and the Wang-Koch axial length adjustment version of SRK/T resulted in median numerical errors not significantly different than 0, regardless of keratometric values.

CONCLUSIONS

In keratoconic eyes, IOL formulas are less accurate than in normal eyes and result in hyperopic refractive outcomes that increase with steeper keratometric values. Using keratoconus-specific formulas and the Wang-Koch axial length adjustment version of SRK/T for axial lengths of 25.2 mm or greater improved IOL power prediction accuracy compared to other formulas. [J Refract Surg. 2023;39(4):242-248.].

Optical bench evaluation of the effect of pupil size in new generation monofocal intraocular lenses

BACKGROUND

A new generation of enhanced monofocal IOLs has been introduced to slightly increase the depth of focus as compared to standard monofocal IOLs. The purpose of this study is to evaluate the effect of pupil size on the through-focus optical performance of three new enhanced monofocal IOLs, designed to improve the range of vision as compared to standard monofocal IOLs.

METHODS

Optical bench testing in white light was performed for different pupils, using an average cornea eye. Distance image quality was evaluated using Modulation Transfer Function (MTF) measurements. Through-focus Visual Acuity (VA) was simulated from these measurements (sVA). Three enhanced monofocal IOLs (ICB00, ISOPure, and RayOne-EMV) and three standard monofocal IOLs: two aspheric (ZCB00 and SN60WF) and one spherical (AAB00) were included.

RESULTS

The enhanced monofocal IOLs provided an improvement in the intermediate sVA as compared to standard monofocal IOLs. For ICB00, the improvement was independent of the pupil size, while for the ISOPure and RayOne-EMV, the intermediate sVA improved with increased pupil size. Similar to the spherical monofocal IOL, the ISOPure and RayOne-EMV showed a strong correlation between improvement in intermediate sVA and reduction of distance sVA and MTF, and increasing pupil size. ICB00 provided the same distance sVA as the aspheric monofocal IOLs and the lowest variability in MTF with pupil size.

CONCLUSION

Optical bench results showed that the ISOPure and RayOne-EMV provide similar performance to a spherical monofocal IOL, with a strong pupil dependency for distance and intermediate vision. The other enhanced monofocal IOL, ICB00, provided a sustained improvement in simulated intermediate VA and maintained distance image quality comparable to that of the standard aspheric monofocal IOLs, even for larger pupils.

Comparison of accuracy of a toric calculator with predicted vs measured posterior corneal astigmatism

PURPOSE

To compare the accuracy of postoperative residual astigmatism prediction using the Barrett toric calculator with predicted vs measured posterior corneal astigmatism (PCA).

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas.

DESIGN

Retrospective case series.

METHODS

We included 602 eyes with monofocal nontoric intraocular lens implantation. Biometry and PCA were obtained from the IOLMaster 700. Anticipated postoperative refractive astigmatism was calculated with the Barrett toric calculator for predicted and measured PCA, and the astigmatism prediction errors (PEs) for each were calculated using vector analysis. The vector PE magnitudes and percentage of eyes within certain amounts of vector PEs were compared between 2 methods.

RESULTS

Compared with the Barrett toric calculator with predicted PCA, the Barrett toric calculator with measured PCA produced significantly smaller mean vector PE (0.54 diopter [D] vs 0.57 D) and higher percentage of eyes with vector PE of ≤0.5 D (57.6% [347/602] vs 52.5% [316/602]) (both P < .05). In eyes with predicted residual astigmatism of ≥0.5 D, the Barrett toric calculator with measured PCA again yielded a significantly higher percentage of eyes with vector PE of ≤0.5 D (51.2% [226/441] vs 44.7% [197/441], P < .05).

CONCLUSIONS

Accuracy of residual astigmatism prediction is improved using the Barrett toric calculator with measured PCA rather than predicted PCA.

Evaluating the prediction accuracy of the Hill-RBF 3.0 formula using a heteroscedastic statistical method

PURPOSE

To evaluate the accuracy of the Hill-RBF 3 formula, with and without direct measurements of total corneal power, using a heteroscedastic statistical method for analysis.

SETTING

Department of Ophthalmology, Shaare Zedek Medical Center, Jerusalem, Israel.

DESIGN

Retrospective, consecutive case series.

METHODS

Records of consecutive patients who underwent routine cataract surgery between February 2018 and June 2020 were retrospectively reviewed. The prediction accuracy of the Hill-RBF 3.0 formula was compared with that of the Barrett Universal II, Emmetropia Verifying Optical 2.0, Haigis, Hill-RBF 2.0, Hoffer Q, Holladay 1, Holladay 2, Kane, Olsen, and SRK/T formulas, based on biometry measurements by swept-source optical coherence tomography (SS-OCT) with standard keratometry (K), SS-OCT with total keratometry (TK), and an optical low-coherence reflectometer (OLCR). Statistical analysis was applied according to a heteroscedastic statistical method with SD of prediction errors as the main parameter for formula performance.

RESULTS

The study included 153 eyes of 153 patients. The SD values that were obtained by Hill-RBF 3.0 (0.266 to 0.285 diopters [D]) were significantly lower compared with those by Hill-RBF 2.0 (0.290 to 0.309 D), Hoffer Q (0.387 to 0.407 D), Holladay 1 (0.367 to 0.385 D), Holladay 2 (0.386 to 0.401 D), and SRK/T (0.377 to 0.399 D) formulas (P < .036). The prediction accuracy of the Hill-RBF 3.0 was similar across the SS-OCT (K), SS-OCT (TK), and OLCR methods of measurement (P > .51).

CONCLUSIONS

The Hill-RBF 3.0 was more accurate than the Hill-RBF 2.0 and older generation formulas and had similar prediction accuracy compared with new generation formulas. The use of TK did not provide significant improvement to its prediction accuracy.

Refractive and keratometric outcomes of supervised novice surgeon-performed limbal relaxing incisions: 1-year results

PURPOSE

To report refractive and keratometric astigmatism outcomes of resident-performed limbal relaxing incisions (LRIs) during cataract surgery.

SETTING

Tertiary care academic teaching hospital.

DESIGN

Retrospective case series.

METHODS

The length, location, and number of LRIs were determined preoperatively using an online calculator. Variables studied were preoperative keratometry and postoperative uncorrected and corrected distance visual acuity, refraction, and keratometry at 1-month, 3-month, and 12-month visits (POM1, POM3, and POM12, respectively). Subgroup analysis was performed on amount and type of astigmatism. The astigmatism double-angle plot tool and analysis of with-the-wound (WtW) and against-the-wound (AtW) changes were used to assess the effect of astigmatism correction at POM1, POM3, and POM12 visits.

RESULTS

In 118 eyes, a higher percentage of eyes demonstrated refractive astigmatism 0.25 diopter (D) or less, 0.50 D or less, 0.75D or less, and 1.0 D or less at POM1 and POM12 (all P < .05) compared with preoperative keratometric astigmatism. Subgroup analysis showed improvement in all groups and types of astigmatism (P < .01). Patients achieved a statistically significant reduction of keratometric astigmatism at POM1, POM3, and POM12 (all P ≤ .0001) relative to baseline, and changes differed significantly based on the preoperative amount of astigmatism (all P ≤ .0001, with greater reductions associated with higher baseline astigmatism) but not by location of the steep meridian. There were significant WtW-AtW changes at POM1, POM3, and POM12. Regression of effect after 1 month was approximately 0.11 D.

CONCLUSIONS

Resident-performed LRIs achieved effective and sustained reduction of both refractive and keratometric astigmatism regardless of meridian or magnitude of astigmatism for at least 1 year postoperatively.

Comparison of intraocular lens power calculation formulas in Chinese eyes with axial myopia

PURPOSE

To assess the accuracy of intraocular lens (IOL) power calculation formulas in Chinese eyes with axial lengths (ALs) longer than 26.0 mm.

SETTING

Department of Cataract Surgery, Shanxi Eye Hospital, China.

DESIGN

Prospective case series.

METHODS

This study evaluated (1) two new formulas (Barrett Universal II and Hill-RBF 2.0), (2) three vergence formulas (Haigis, Holladay 1, and SRK/T), and (3) the original and modified Wang-Koch AL adjustment formulas with Holladay 1 and SRK/T. The User Group for Laser Interference Biometry lens constants were used for IOL power calculation. The refractive prediction error was calculated by subtracting the predicted refraction from the actual refraction postoperatively. The mean numerical error (MNE), percentage of eyes with hyperopic outcomes, and mean absolute error (MAE) were determined.

RESULTS

The study comprised 136 eyes. The Barrett and Hill-RBF formulas had MNEs close to zero (-0.09 D to 0.03 D), the Haigis, Holladay 1, and SRK/T produced hyperopic MNEs (0.25 to 0.70 D), and the original and modified Wang-Koch AL adjustment formulas induced myopic MNEs (-0.48 to -0.22 D). The original Wang-Koch formulas produced significantly lower percentages of eyes with hyperopic outcomes (15% to 18%) than all other formulas (28% to 91%). There were no significant differences in MAEs between the Barrett, Hill-RBF, Haigis, and original and modified Wang-Koch adjustment with the Holladay 1 (0.32 to 0.41 D).

CONCLUSION

The performances of the Barrett and Hill-RBF were comparable in long eyes. The incidence of hyperopic outcome with the Wang-Koch AL adjustment formula was significantly lower than other formulas.

Cost-Effectiveness of Preoperative OCT in Cataract Evaluation for Multifocal Intraocular Lens

PURPOSE

To determine the cost effectiveness of an adjunctive screening OCT during the preoperative evaluation of a patient considering cataract surgery with a multifocal intraocular lens (IOL) implantation.

DESIGN

Cost-effectiveness analysis.

PARTICIPANTS

A 67-year-old man with 20/60 vision undergoing evaluation for first-eye cataract surgery.

METHODS

The cost-effectiveness analysis of the reference patient undergoing a preoperative cataract examination with and without a screening OCT was performed, evaluating for vitreoretinal diseases including an epiretinal membrane, age-related macular degeneration, vitreomacular traction, and cystoid macular edema. It was assumed that patients with macular pathologies detected before surgery would receive a monofocal IOL and be referred to a retina specialist for evaluation and management. The Medicare reimbursable cost of an OCT was $41.81. All costs and benefits were adjusted for inflation to 2019 United States dollars and discounted 3% per annum over a 16-year time horizon. Probability sensitivity analyses and 1-way deterministic sensitivity analyses were performed to assess for uncertainty.

MAIN OUTCOME MEASURES

Incremental cost-effectiveness ratio and incremental cost-utility ratio (ICUR) measured in quality-adjusted life years (QALYs).

RESULTS

Approximately 20.5% of patients undergoing cataract surgery may have macular pathologies, of which 11% may not be detected on the initial clinical examination. In the base case, an adjunctive preoperative OCT was cost effective from a third-party payer and societal perspective in the United States. In the probability sensitivity analyses, the ICURs were within the societal willingness-to-pay threshold of $50 000/QALY in approximately 64.4% of the clinical scenarios.

CONCLUSIONS

A preoperative screening OCT during the evaluation of a patient considering a multifocal IOL added to the costs of the cataract surgery, but the OCT increased the detection of macular pathologies and improved the QALYs over time. An adjunctive screening OCT can be cost effective from a third-party payer and societal perspective.

Accuracy and feasibility of axial length measurements by a new optical low-coherence reflectometry-based device in eyes with posterior subcapsular cataract

PURPOSE

To evaluate the feasibility and accuracy of measuring axial length (AL) by a new optical low-coherence reflectometry (OLCR)-based device in eyes with central posterior subcapsular cataract (PSC).

SETTING

Department of Ophthalmology, Assaf-Harofeh Medical Center, Zerifin, Israel.

DESIGN

Retrospective case series.

METHODS

Consecutive cases of patients who had uneventful cataract surgery and whose preoperative AL measurements were not feasible with the partial coherence interferometry (PCI) device because of a central PSC were assessed. Preoperative AL was measured by the OLCR device and immersion ultrasound (US). Preoperative results were compared with the postoperative AL measurements obtained by the PCI.

RESULTS

Twenty-seven patients (27 eyes) were enrolled in the study. The median difference between the OLCR and the PCI AL measurements (0.07 mm) was lower than the median difference between the US and the PCI AL measurements (0.13 mm) (P = .016). The ranges of the limits of agreement were 0.15 mm between OLCR and PCI, and 0.88 mm between US and PCI. The proportion of eyes with an AL difference of less than 0.1 mm was significantly higher between the OLCR and the PCI devices (24 eyes [88.9%]) than between the US and the PCI devices (9 eyes [33.3%]) (P = .001).

CONCLUSIONS

The OLCR-based device successfully measured the preoperative AL in all eyes with central PSC for which preoperative PCI scans were not feasible. These measurements had a high level of agreement with the postoperative AL measurements obtained by the PCI device.

Secondary intraocular lens implantation: Complication rates, visual acuity, and refractive outcomes

PURPOSE

To compare complication rates, visual acuity, and refractive outcomes of secondary intraocular lens (IOLs) implantation.

SETTING

Department of Ophthalmology, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

DESIGN

Retrospective case series.

METHODS

All secondary IOLs placed by the anterior segment service were reviewed. Preoperative data, operative reports, and data from each subsequent postoperative visit were evaluated. Patients were divided into 5 groups based on the final IOL position: (1) sulcus with optic capture, (2) sulcus without optic capture, (3) anterior chamber (AC), (4) iris-fixated, and (5) transscleral-sutured. Complication rates, visual acuity, and refractive outcomes were compared for each group.

RESULTS

The sulcus with and without optic capture groups had the lowest complication rates and best visual acuity outcomes. There was no difference in final corrected distance visual acuity (CDVA) between the transscleral-sutured IOL, iris-fixated IOL, and AC IOL groups, although the AC IOL group had the lowest rates of early postoperative complications and a significant improvement in vision. The transscleral-sutured IOL group had the highest complication rates, and 25% of patients in the iris-fixated IOL group lost 2 or more lines of CDVA.

CONCLUSIONS

When a secondary IOL cannot be placed within the capsular bag, sulcus with optic capture is the best alternative, followed by sulcus without optic capture. There was no difference in visual acuity outcomes between transscleral-sutured IOLs, iris-fixated IOLs, and AC IOLs. Anterior chamber IOLs resulted in fewer early complications.

Intraocular lens power calculations in eyes with previous hyperopic laser in situ keratomileusis or photorefractive keratectomy

PURPOSE

To evaluate the accuracy of 7 intraocular lens (IOL) calculation formulas in patients with previous hyperopic laser in situ keratomileusis (LASIK) or excimer laser photorefractive keratectomy (PRK).

DESIGN

Retrospective case series.

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, and private practice, Mesa, Arizona, USA.

METHODS

The 7 formulas evaluated were the adjusted Atlas 0-3, Masket, Modified Masket, Haigis-L, Shammas-PL, Barrett True-K, and Barrett True-K No-History. The Masket and Modified Masket were calculated using the single-K version of Holladay 1 and Hoffer Q formulas; the adjusted Atlas 0-3 was calculated using the double-K version of Holladay 1 and Hoffer Q. The IOL power predicted by each formula was calculated by targeting the postoperative manifest refraction. The IOL prediction error was obtained by subtracting the predicted IOL power from the implanted IOL power. The mean IOL prediction error, median absolute refractive prediction error, and percentages of eyes within ±0.50 diopter (D) and ±1.00 D of the predicted refraction were calculated.

RESULTS

Twenty-one eyes of 21 patients were evaluated. There were no significant differences in the median absolute refractive prediction error or percentages of eyes within ±0.50 D or ±1.00 D of the predicted refraction between formulas or methods. The IOL mean prediction errors were comparable between the Holladay 1 and Hoffer Q calculations for all formulas except for a greater error for the double-K version of the Hoffer Q of the adjusted Atlas 0-3.

CONCLUSION

In eyes that had hyperopic LASIK or PRK, there were no significant differences in the accuracy between the 7 IOL calculation formulas.

Corneal remodeling after implantation of a shape-changing inlay concurrent with myopic or hyperopic laser in situ keratomileusis

PURPOSE

To compare the induced addition (add)-power profile and epithelial remodeling between patients receiving hyperopic and myopic laser in situ keratomileusis (LASIK) concurrently with implantation of a corneal shape-changing inlay.

SETTING

Specialty clinics in Monterrey and Tijuana, Mexico.

DESIGN

Retrospective case series.

METHODS

Preoperative hyperopic patients (mean spherical equivalent [SE] treatment +1.71 diopters [D] ± 0.51 [SD]) and myopic patients (mean SE treatment -2.48 ± 1.33 D) had implantation of a Raindrop Near Vision Inlay in the nondominant eye immediately after the excimer laser ablation in both eyes under a corneal flap. Monocular and binocular visual acuities were recorded at 6 m. Wavefront measurement analysis yielded the mean inlay add-power profile, and optical coherence tomography images yielded the mean epithelial remodeling profile.

RESULTS

In the inlay eye in the hyperopic group (n = 34) and myopic group (n = 29), the mean uncorrected near visual acuity exceeded 20/25 (85% 20/25 or better), the mean uncorrected distance visual acuity (UDVA) was 20/32 (62% 20/32 or better), and the mean binocular UDVA was 20/18 (100% 20/25 or better). The add-power profiles for the hyperopic and myopic groups were similar. The epithelial thinning profiles were also the same, thinning centrally by approximately 19 μm, and were uncorrelated with the treated refractive error.

CONCLUSIONS

After concurrent LASIK and inlay implantation, the visual acuity, induced add-power profile, and epithelial remodeling were the same, regardless of hyperopic or myopic treatment.

Evaluation of crystalline lens and intraocular lens tilt using a swept-source optical coherence tomography biometer

PURPOSE

To evaluate crystalline lens and intraocular lens (IOL) tilt using a swept-source optical coherence tomography (SS-OCT) biometer (IOLMaster 700).

SETTING

Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

DESIGN

Retrospective case series.

METHODS

The study patients were evaluated for 1) repeatability of the crystalline lens tilt measurement, 2) preoperative crystalline lens and postoperative IOL tilt in right eyes, 3) mirror symmetry between right eyes and left eyes, 4) the correlation between preoperative crystalline lens and postoperative IOL tilt, and 5) the correlation between the magnitude of lens tilt and ocular parameters.

RESULTS

The study comprised 333 patients. The repeatability was 0.1 degrees for tilt magnitude and 3.0 degrees for tilt direction. Both the crystalline lens and IOL had anterior tilt of the nasal portion with mean tilt magnitudes of 3.7 degrees ± 1.1 (SD) (range 0.4 to 6.9 degrees) for the crystalline lens and 4.9 ± 1.8 degrees (range 1.6 to 10.7 degrees) for the IOL. There was mirror symmetry between right eyes and left eyes. The mean IOL tilt magnitude exceeded crystalline lens tilt by 1.2 ± 1.1 degrees (range -3.2 to 4.0 degrees), and the 2 values were significantly correlated (all P < .01). The magnitude of crystalline lens tilt significantly increased with decreasing axial length and with increasing angle α (all P < .05).

CONCLUSIONS

The repeatability of crystalline lens tilt measurements using the SS-OCT biometer was excellent. There was mirror symmetry between the right eyes and left eyes. Preoperative crystalline lens tilt could be used to predict the postoperative IOL tilt. The lens tilt magnitude was greater in short eyes and in eyes with larger angle α.

Long-term safety of laser in situ keratomileusis in eyes with thin corneas: 5-year follow-up

AIM

To investigate the long term (≥5y) efficacy, predictability, and safety of laser in situ keratomileusis (LASIK) in eyes with thin corneas [central corneal thickness (CCT) <500 µm].

METHODS

A total of 339 patients met the criteria of this study. Finally, 175 eyes of 89 patients who had thin corneas and underwent LASIK≥5y ago returned to our clinic and included in this study. Preoperative parameters recorded included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), manifest refraction, CCT and corneal topography. At returning visits, in addition to visual acuity and manifest refraction, ultrasound CCT and corneal topography were performed. Optical coherence tomography was used to measure the CCT, LASIK flap thickness, and residual stromal bed thickness (RSBT). Safety index, efficacy index, percentage of eyes within ±0.5 D and ±1.0 D of refraction, percent tissue altered (PTA), and percentage stromal bed thickness (PSBT) were calculated.

RESULTS

The safety index was 1.09 and efficacy index was 0.99. The percentages of eyes within ±0.5 D and ±1.0 D were 71.2% and 87.7%, respectively. The mean PTA was 40%±6% (range 20% to 55%); 76 eyes (43.4%) had PTA <40% and 99 eyes (56.6%) had PTA≥40%. The mean RSBT was 303±27 µm (range 240 to 390 µm), and 2 eyes had RSBT<250 µm. The mean PSBT was 61%±9% (range 51% to 85%). No eyes developed ectasia.

CONCLUSION

In this cohort with the PSBT of 50% or more, LASIK is safe with follow-up for at least 5y.

Accuracy of 8 intraocular lens calculation formulas in relation to anterior chamber depth in patients with normal axial lengths

PURPOSE

To determine the effect of anterior chamber depth (ACD) on the accuracy of 8 intraocular lens calculation formulas in patients with normal axial lengths (ALs).

SETTING

Baylor College of Medicine, Alkek Eye center, Houston, Texas, USA.

DESIGN

Retrospective case series.

METHODS

Patients having cataract surgery with ALs between 22.0 mm and 25.0 mm were divided into 3 groups based on their preoperative ACD measurement. The mean prediction errors, mean absolute errors (MAEs), and median absolute errors for each group were calculated.

RESULTS

For the ACD of 3.0 mm or less group and the ACD of 3.5 mm or more group, the Barrett Universal II, Holladay 2, Haigis, and Olsen ray-tracing formulas had mean prediction error values that were not significantly different from zero. For the ACD of 3.01 to 3.49 mm group, all formulas had mean prediction error values that were not significantly different from zero. For the ACD of 3.0 mm or less group, the Barrett Universal II formula had a smaller median absolute error than the Haigis, Hoffer Q, and Olsen optical low-coherence reflectometry (OLCR) (Lenstar) formulas and a smaller MAE than the Hoffer Q, Hill-RBF, and Olsen OLCR (P < .05). In the ACD of 3.5 mm or more group, the Barrett MAE was smaller than the Hoffer Q (P < .05); however, there were no significant differences between median absolute errors.

CONCLUSION

In eyes with normal ALs, taking preoperative ACD values into consideration might improve refractive outcomes.

New algorithm for toric intraocular lens power calculation considering the posterior corneal astigmatism

PURPOSE

To assess the accuracy of toric intraocular lens (IOL) power calculations of a new algorithm that incorporates the effect of posterior corneal astigmatism (PCA).

SETTING

Abbott Medical Optics, Inc., Groningen, the Netherlands.

DESIGN

Retrospective case report.

METHODS

In eyes implanted with toric IOLs, the exact vergence formula of the Tecnis toric calculator was used to predict refractive astigmatism from preoperative biometry, surgeon-estimated surgically induced astigmatism (SIA), and implanted IOL power, with and without including the new PCA algorithm. For each calculation method, the error in predicted refractive astigmatism was calculated as the vector difference between the prediction and the actual refraction. Calculations were also made using postoperative keratometry (K) values to eliminate the potential effect of incorrect SIA estimates.

RESULTS

The study comprised 274 eyes. The PCA algorithm significantly reduced the centroid error in predicted refractive astigmatism (P < .001). With the PCA algorithm, the centroid error reduced from 0.50 @ 1 to 0.19 @ 3 when using preoperative K values and from 0.30 @ 0 to 0.02 @ 84 when using postoperative K values. Patients who had anterior corneal against-the-rule, with-the-rule, and oblique astigmatism had improvement with the PCA algorithm. In addition, the PCA algorithm reduced the median absolute error in all groups (P < .001).

CONCLUSIONS

The use of the new PCA algorithm decreased the error in the prediction of residual refractive astigmatism in eyes implanted with toric IOLs. Therefore, the new PCA algorithm, in combination with an exact vergence IOL power calculation formula, led to an increased predictability of toric IOL power.

The Sensitivity of Clinical Outcomes to Centration on the Light-Constricted Pupil for a Shape-Changing Corneal Inlay

PURPOSE

To assess the clinically acceptable range of inlay decentration with respect to the light-constricted pupil center and the coaxially sighted corneal light reflex (CSCLR) for an inlay (Raindrop Near Vision Inlay; ReVision Optics, Inc., Lake Forest, CA) that reshapes the anterior corneal surface.

METHODS

In this retrospective, observational cohort study of 115 patients with emmetropic or low hyperopic presbyopia who were implanted with a shape-changing corneal inlay, visual acuity, task performance (in good and dim light), reports of halos and glare, and satisfaction data were collected from the preoperative and 3-month postoperative examinations. Inlay centration with respect to the pupil center and CSCLR was determined from the center of the inlay effect derived from iTrace (Tracey Technologies, Houston, TX) wavefront measurements. Multivariate regression models assessed the influence of inlay position on visual outcomes.

RESULTS

On average, monocular uncorrected near visual acuity (UNVA) improved 4.9 ± 1.7 lines in the treated eye, with no loss in binocular distance vision. Eighty-three percent of implants were centered radially within 0.5 mm of the pupil center. Multivariate analysis of decentration with respect to both the pupil center and CSCLR revealed no significant interaction with the above clinical outcomes, with the exception of UNVA in the treated eye (all P > .05, α = 0.05). For decentration of less than 0.75 mm, the change in UNVA was less than 1 line.

CONCLUSIONS

Distance and near visual acuity, task performance, severity of halos and glare, and satisfaction were independent of radial decentration of the Raindrop Near Vision Inlay of less than 0.75 mm from the light-constricted pupil. [J Refract Surg. 2018;34(3):164-170.].

Intraocular Lens Power Calculation in Eyes After Laser In Situ Keratomileusis or Photorefractive Keratectomy for Myopia

Intraocular power calculation is challenging for patients who have previously undergone corneal refractive surgery. The sources of prediction errors for these eyes are well known; however, the numerous formulas and methods available for calculating intraocular lens power in these cases are eloquent testimony to the absence of a definitive solution. This review discusses some of the available methods for improving the accuracy for predicting the refractive outcome for these patients. It focuses mainly on the methods available on the American Society of Cataract and Refractive Surgery (ASCRS) online calculator and provides some practical guidelines for cataract surgeons who encounter these challenging cases.

Comparison of Newer IOL Power Calculation Methods for Eyes With Previous Radial Keratotomy

Purpose

To evaluate the accuracy of the optical coherence tomography–based (OCT formula) and Barrett True K (True K) intraocular lens (IOL) calculation formulas in eyes with previous radial keratotomy (RK).

Methods

In 95 eyes of 65 patients, using the actual refraction following cataract surgery as target refraction, the predicted IOL power for each method was calculated. The IOL prediction error (PE) was obtained by subtracting the predicted IOL power from the implanted IOL power. The arithmetic IOL PE and median refractive PE were calculated and compared.

Results

All formulas except the True K produced hyperopic IOL PEs at 1 month, which decreased at ≥4 months (all P < 0.05). For the double-K Holladay 1, OCT formula, True K, and average of these three formulas (Average), the median absolute refractive PEs were, respectively, 0.78 diopters (D), 0.74 D, 0.60 D, and 0.59 D at 1 month; 0.69 D, 0.77 D, 0.77 D, and 0.61 D at 2 to 3 months; and 0.34 D, 0.65 D, 0.69 D, and 0.46 D at ≥4 months. The Average produced significantly smaller refractive PE than did the double-K Holladay 1 at 1 month (P < 0.05). There were no significant differences in refractive PEs among formulas at 4 months.

Conclusions

The OCT formula and True K were comparable to the double-K Holladay 1 method on the ASCRS (American Society of Cataract and Refractive Surgery) calculator. The Average IOL power on the ASCRS calculator may be considered when selecting the IOL power. Further improvements in the accuracy of IOL power calculation in RK eyes are desirable.

Evaluation of Femtosecond Laser Intrastromal Incision Location Using Optical Coherence Tomography

PURPOSE

To use optical coherence tomography (OCT) to evaluate the femtosecond laser intrastromal incisions made during cataract surgery to reduce corneal astigmatism.

DESIGN

Retrospective case series.

PARTICIPANTS

Seventy-seven eyes of 77 patients.

METHODS

Paired intrastromal incisions were created using the Catalys femtosecond laser (Abbott Medical Optics, Inc., Santa Ana, CA). The planned intrastromal incision parameters were 20% uncut anterior, 20% uncut posterior, midpoint depth of 50%, and 90° side cut angle. Optical coherence tomography scans were obtained 3 weeks or more after surgery to assess these 4 parameters, and actual values were compared with intended values.

MAIN OUTCOME MEASURES

Percentages of uncut anterior and posterior tissue, midpoint depth, and degrees of side cut angle.

RESULTS

The mean values were 17.2±5.8% (range, 7.2%-36.9%) for uncut anterior, 32.5±8.8% (range, 6.0%-57.9%) for uncut posterior, and 42.3±6.6% (range, 25.5%-65.4%) for midpoint depth, which all were significantly different from the planned parameters (all P < 0.05). The mean side cut angle was 88.5°±5.6° (range, 71°-114°) and was significantly different from the planned side cut angle of 90° (P < 0.05). In 50 eyes that had paired intrastromal incisions scanned by the OCT, there was no correlation between the paired incisions for midpoint depth and side cut angle (correlation coefficient, r = -0.063 and -0.067, respectively; P > 0.05).

CONCLUSIONS

The intrastromal incision midpoint depth was significantly more anterior than the planned depth of 50%. The locations of paired intrastromal incisions in each eye were not correlated. Further improvements are needed to ensure the precise location of the intrastromal incisions made with this device.

The Enigmatic Cornea and Intraocular Lens Calculations: The LXXIII Edward Jackson Memorial Lecture

PURPOSE

To review the progress and challenges in obtaining accurate corneal power measurements for intraocular lens (IOL) calculations.

DESIGN

Personal perspective, review of literature, case presentations, and personal data.

METHODS

Through literature review findings, case presentations, and data from the author's center, the types of corneal measurement errors that can occur in IOL calculation are categorized and described, along with discussion of future options to improve accuracy.

RESULTS

Advances in IOL calculation technology and formulas have greatly increased the accuracy of IOL calculations. Recent reports suggest that over 90% of normal eyes implanted with IOLs may achieve accuracy to within 0.5 diopter (D) of the refractive target. Though errors in estimation of corneal power can cause IOL calculation errors in eyes with normal corneas, greater difficulties in measuring corneal power are encountered in eyes with diseased, scarred, and postsurgical corneas. For these corneas, problematic issues are quantifying anterior corneal power and measuring posterior corneal power and astigmatism. Results in these eyes are improving, but 2 examples illustrate current limitations: (1) spherical accuracy within 0.5 D is achieved in only 70% of eyes with post-refractive surgery corneas, and (2) astigmatism accuracy within 0.5 D is achieved in only 80% of eyes implanted with toric IOLs.

CONCLUSION

Corneal power measurements are a major source of error in IOL calculations. New corneal imaging technology and IOL calculation formulas have improved outcomes and hold the promise of ongoing progress.