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Simon P Holland - One of the best experts on this subject based on the ideXlab platform.
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topography guided Laser Refractive Surgery
Current Opinion in Ophthalmology, 2013Co-Authors: Simon P Holland, David T C Lin, Johnson C H TanAbstract:PURPOSE OF REVIEW Topography-guided Laser Refractive Surgery regularizes the front corneal surface irregularities to achieve the desired Refractive outcome. This is particularly applicable in highly aberrated corneas, where wavefront aberrometry is often not possible. This article aims to review the recently published results of topography-guided ablations in normal regular corneas, highly aberrated corneas, and its application in conjunction with collagen cross-linking (CXL) in cases of keratectasia. RECENT FINDINGS Topography-guided Laser ablation is increasingly used with good efficacy and safety outcomes in highly aberrated corneas with irregular astigmatism. These include eyes with Refractive Surgery complications including postLaser in-situ keratomileusis ectasia, decentered ablation, small optical zones, asymmetrical astigmatism, and postradial keratectomy astigmatism. Further indications are for postkeratoplasty astigmatism and keratoconus. Simultaneous topography-guided ablations with CXL in keratectasia have been promising, both in addressing the surface irregularities and progressive nature of the conditions. SUMMARY Topography-guided Laser Refractive Surgery is proving to be effective and well tolerated in the visual rehabilitation of highly aberrated eyes, with increasing predictability based on the recent research.
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intraocular lens power calculations after myopic Laser Refractive Surgery a comparison of methods in 173 eyes
Ophthalmology, 2011Co-Authors: Martin Mccarthy, Gregory M Gavanski, Katherine E Paton, Simon P HollandAbstract:Purpose To evaluate and compare published methods of intraocular lens (IOL) power calculation after myopic Laser Refractive Surgery in a large, multi-surgeon study. Design Retrospective case series. Participants A total of 173 eyes of 117 patients who had uneventful LASIK (89) or photoRefractive keratectomy (84) for myopia and subsequent cataract Surgery. Methods Data were collected from primary sources in patient charts. The Clinical History Method (vertex corrected to the corneal plane), the Aramberri Double-K, the Latkany Flat-K, the Feiz and Mannis, the R-Factor, the Corneal Bypass, the Masket (2006), the Haigis-L, and the Shammas.cd postRefractive adjustment methods were evaluated in conjunction with third- and fourth-generation optical vergence formulas, as appropriate. Intraocular lens power required for emmetropia was back-calculated using stable post-cataract Surgery manifest refraction and implanted IOL power, and then formula accuracy was compared. Main Outcome Measures Prediction error arithmetic mean ± standard deviation (SD), range (minimum and maximum), and percent within 0 to −1.0 diopters (D), ±0.5 D, ±1.0 D, and ±2.0 D relative to target refraction. Results The top 5 corneal power adjustment techniques and formula combinations in terms of mean prediction errors, standard deviations, and minimizing hyperopic "Refractive surprises" were the Masket with the Hoffer Q formula, the Shammas.cd with the Shammas-PL formula, the Haigis-L, the Clinical History Method with the Hoffer Q, and the Latkany Flat-K with the SRK/T with mean arithmetic prediction errors and standard deviations of −0.18±0.87 D, −0.10±1.02 D, −0.26±1.13 D, −0.27±1.04 D, and −0.37±0.91 D, respectively. Conclusions By using these methods, 70% to 85% of eyes could achieve visual outcomes within 1.0 D of target refraction. The Shammas and the Haigis-L methods have the advantage of not requiring potentially inaccurate historical information. Financial Disclosure(s) The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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avoiding serious corneal complications of Laser assisted in situ keratomileusis and photoRefractive keratectomy
Ophthalmology, 2000Co-Authors: Simon P Holland, Dan Z. Reinstein, Sabong SrivannaboonAbstract:Abstract Objective To identify avoidable factors that can lead to serious complications of Laser Refractive Surgery (photoRefractive keratectomy [PRK] and Laser assisted in situ keratomileusis [LASIK]). Design Noncomparative case series. Participants Twenty-seven eyes of 19 patients who had undergone either LASIK or PRK with severe complications accrued retrospectively. Intervention Review of clinical records. Main outcome measures Symptoms, Refractive outcome, and assessment of avoidable factors contributing to the complication. Results Patients were analyzed in four groups: group 1, scarring with ectasia; group 2, unrecognized keratoconus; group 3, flap related LASIK complications; and group 4, multiple retreatments. The 8 eyes with scarring and ectasia presented with the worst vision, 20/400 uncorrected visual acuity and 20/200 best spectacle-corrected visual acuity, with avoidable factors considered as high or difficult prescriptions with multiple retreatments. Four eyes in two patients with possible forme fruste keratoconus showed worsening irregular astigmatism. Laser assisted in situ keratomileusis flap complications included six eyes with partial Laser treatment under an incomplete flap with subsequent severe irregular astigmatism. Six eyes in three patients who had undergone an average of three multiple retreatments showed decreased vision with irregular astigmatism. Conclusions Certain severe complications of Laser Refractive Surgery likely can be avoided by using caution when treating high prescriptions, particularly with retreatments, recognizing early keratoconus and avoiding Laser treatment under a partial flap in LASIK.
Kenneth J. Hoffer - One of the best experts on this subject based on the ideXlab platform.
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comparison of intraocular lens power formulas according to axial length after myopic corneal Laser Refractive Surgery
Journal of Cataract and Refractive Surgery, 2021Co-Authors: Woongjoo Whang, Kenneth J. Hoffer, Seonju Kim, Sohyang Chung, Giacomo SaviniAbstract:PURPOSE To assess the predictive accuracy of 4 no-history intraocular lens (IOL) power formulas in eyes with prior myopic excimer Laser Surgery, classified in 4 groups according to their axial length (AL), and investigate the relationship between AL and predictive accuracy. SETTING Seoul St. Mary's Hospital, Republic of Korea. DESIGN Retrospective case series. METHODS IOL power was calculated with the Barrett True-K, Haigis-L, Shammas-PL, and Triple-S formulas in 4 groups classified according to AL. Primary outcomes were the median absolute error (MedAE) and percentage of eyes with a prediction error (PE) within ±0.50 diopter (D). RESULTS This study included 107 eyes of 107 patients. The Barrett True-K had the lowest MedAE when AL was <26.0 mm (0.30 D) and between 26.0 and 28.0 mm (0.54 D); in these subgroups, it had the highest percentages with a PE within ±0.50 D (71.4% and 46.2%). For AL between 28.0 and 30.0 mm, the Triple-S method showed the lowest MedAE (0.43 D) and highest percentage with a PE within ±0.50 D (58.3%). For AL ≥30.0 mm, the Shammas-PL formula produced the lowest MedAE (0.41 D) and highest percentage with a PE within ±0.50 D (58.3%). The Barrett True-K was the only formula with a correlation between AL and PE (r = -0.219/P = .023). CONCLUSIONS The predictive accuracy of no-history IOL formulas depends on the AL. The Barrett True-K had the highest accuracy when AL was < 28.0 mm and the Triple-S when it ranged from 28.0 mm to 30.0 mm, whereas the Shammas-PL was more accurate when AL was ≥30.0 mm.
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corneal ray tracing versus simulated keratometry for estimating corneal power changes after excimer Laser Surgery
Journal of Cataract and Refractive Surgery, 2014Co-Authors: Giacomo Savini, Antonio Calossi, Massimo Camellin, Francesco Carones, Marco Fantozzi, Kenneth J. HofferAbstract:Purpose To evaluate whether the Refractive changes induced by excimer Laser Surgery can be accurately measured by corneal ray tracing performed by a combined rotating Scheimpflug camera–Placido-disk corneal topographer (Sirius). Setting Private practices. Design Evaluation of diagnostic test. Methods This multicenter retrospective study comprised patients who had myopic or hyperopic excimer Laser Refractive Surgery. Preoperatively and postoperatively, 2 corneal power measurements—simulated keratometry (K) and mean pupil power—were obtained. The mean pupil power was the corneal power calculated over the entrance pupil by ray tracing through the anterior and posterior corneal surfaces using Snell's law. Agreement between the Refractive and corneal power change was analyzed according to Bland and Altman. Regression analysis and Bland-Altman plots were used to evaluate agreement between measurements. Results The study evaluated 72 eyes (54 patients). The difference between the postoperative and preoperative simulated K values underestimated the Refractive change after myopic correction and overestimated it after hyperopic correction. Agreement between simulated K changes and Refractive changes was poor, especially for higher amounts of correction. A proportional bias was detected ( r = −0.77; P r 2 = 0.98). The mean pupil power did not overestimate or underestimate the Refractive change. The 95% LoA ranged between −0.97 D and +0.56 D. Conclusion Corneal ray tracing accurately measured corneal power changes after excimer Laser Refractive Surgery. Financial Disclosures Dr. Calossi is consultant to Costruzione Strumenti Oftalmici. Dr. Carones is consultant to Wavelight Laser Technologie AG. No other author has a financial or proprietary interest in any material or method mentioned.
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intraocular lens power calculation after previous Laser Refractive Surgery
Journal of Cataract and Refractive Surgery, 2009Co-Authors: Kenneth J. HofferAbstract:Methods to attempt more accurate prediction of intraocular lens power in Refractive Surgery eyes are many, and none has proved to be the most accurate. Until one is identified, a spreadsheet tool is available and can be used. It automatically calculates all the methods for which data are available on a single sheet for the patient's chart. The various methods and how they work are described.
Scott Macrae - One of the best experts on this subject based on the ideXlab platform.
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the effect of optical zone decentration on lower and higher order aberrations after photoRefractive keratectomy in a cat model
Investigative Ophthalmology & Visual Science, 2007Co-Authors: Jens Buhren, Geunyoung Yoon, Scott Macrae, Shawn Kenner, Krystel R HuxlinAbstract:Correct alignment of the ablation to the visual axis of the eye is an essential requirement for optimal outcome in Laser Refractive Surgery (LRS). Decentration of the ablation zone leads to incomplete Refractive correction and induction of higher-order aberrations (HOAs), especially coma.1–4 The expected benefit of less HOA induction in eye tracker–controlled treatments has been demonstrated.5 However, decentration still occurs as a result of misalignment of the tracking system,6 static registration errors due to surgeon offsets,7 and pupil center shifts as a function of dilation.8 In most cases, the magnitude of such misalignments is 500 μm are one of the most visually disturbing complications after LRS. Besides causing severe deterioration of visual quality, such complications are difficult to treat, and success is often limited.12–18 Although several studies on decentration-induced aberrations after conventional1,2,7 and wavefront-guided LRS3,4,8,19 have been published, all assumed a perfect ablation and did not consider the inherent induction of HOA which occurs in real corneas as a result of wound healing and biomechanical effects.20,21 The present study was conducted to investigate the effects of decentration of the Laser ablation relative to the entrance pupil of the eye on LOA, HOA, and optical quality, in a cat photoRefractive keratectomy (PRK) model. Although the optical effects of PRK for myopia, such as reduction of defocus, induction of coma, and positive spherical aberration are similar in cats and humans,22,23 the greater corneal surface area and the naturally large scotopic pupil diameter (PD) of ~12 mm in cats allowed us to measure wavefront changes well beyond the ablation OZ. A simplified computational model was used to simulate decentration effects over a circular area of 3000 μm in diameter by calculating wavefront errors (WFEs) for systematically offset subapertures of 3.5 and 6.0 mm. Using this paradigm, we assessed (1) the nature and magnitude and spatial distribution of optical aberrations induced by different amounts of decentration, (2) the impact of such aberrations on theoretical optical quality, (3) whether residual Refractive errors could be partially attributed to microdecentrations (≤500 μm), and (4) the impact of optical aberrations induced by Laser Refractive Surgery on tolerance of decentration.
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aberrations induced in wavefront guided Laser Refractive Surgery due to shifts between natural and dilated pupil center locations
Journal of Cataract and Refractive Surgery, 2006Co-Authors: Jason Porter, Geunyoung Yoon, Scott Macrae, Ian G Cox, Diana C Lozano, Jessica I Wolfing, Remy Tumbar, David R WilliamsAbstract:Purpose To determine the aberrations induced in wavefront-guided Laser Refractive Surgery due to shifts in pupil center location from when aberrations are measured preoperatively (over a dilated pupil) to when they are corrected surgically (over a natural pupil). Setting Center for Visual Science and Department of Ophthalmology, University of Rochester, Rochester, New York, USA. Methods Shifts in pupil center were measured between dilated phenylephrine hydrochloride (Neo-Synephrine [2.5%]) and nonpharmacological mesopic conditions in 65 myopic eyes treated with wavefront-guided Laser in situ keratomileusis (Technolas 217z, Bausch & Lomb). Each patient's preoperative and 6-month postoperative wave aberrations were measured over the dilated pupil. Aberrations theoretically induced by decentration of a wavefront-guided ablation were calculated and compared with those measured 6 months postoperatively (6.0 mm pupil). Results The mean magnitude of pupil center shift was 0.29 mm ± 0.141 (SD) and usually occurred in the inferonasal direction as the pupil dilated. Depending on the magnitude of shift, the fraction of the higher-order postoperative root-mean-square wavefront error that could be due theoretically to pupil center decentrations was highly variable (mean 0.26 ± 0.20 mm). There was little correlation between the calculated and 6-month postoperative wavefronts, most likely because pupil center decentrations are only 1 of several potential sources of postoperative aberrations. Conclusions Measuring aberrations over a Neo-Synephrine-dilated pupil and treating them over an undilated pupil typically resulted in a shift of the wavefront-guided ablation in the superotemporal direction and an induction of higher-order aberrations. Methods referencing the aberration measurement and treatment with respect to a fixed feature on the eye will reduce the potential for inducing aberrations due to shifts in pupil center.
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surgeon offsets and dynamic eye movements in Laser Refractive Surgery
Journal of Cataract and Refractive Surgery, 2005Co-Authors: Jason Porter, Geunyoung Yoon, Scott Macrae, Ian G Cox, Gang Pan, Ted Twietmeyer, David R WilliamsAbstract:METHODS: The surgeon’s accuracy in aligning the pupil center with the Laser center axis was measured when engaging the eye-tracker in 17 eyes receiving conventional Laser in situ keratomileusis (LASIK) procedures (Technolas 217z; Bausch & Lomb). Eye movements were measured subsequently during the treatment in 10 eyes using a pupil camera operating at 50 Hz. Temporal power spectra were calculated from the eye movement measurements. RESULTS: The mean pupil misalignment by the surgeon at the beginning of the procedure was 206.1 mm G 80.99 (SD) (with respect to the Laser center). The Laser center was typically misaligned below (inferiorly) and to the left (nasally and temporally in left and right eyes, respectively) of the Laser center.Smallamountsofcyclotorsionwereobservedduringthe ablation(<2degrees). Themean magnitude of dynamic pupil decentration from the Laser center during treatment was 227.0 G 44.07 mm. The mean standard deviation of eye movements was 65.7 G 25.64 mm. Temporal power spectra calculated from the horizontal and vertical changes in eye position during the ablation were similar. Ninety-five percent of the total power of the eye movements was contained in temporal frequencies up to 1 Hz, on average, in both directions. CONCLUSIONS:Most eye movements duringLASIK are slow drifts in fixation. An eye-tracker with a 1.4 Hz closed-loop bandwidth could compensate for most eye movements in conventional or customized ablations.
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higher order aberrations in eyes with irregular corneas after Laser Refractive Surgery
Ophthalmology, 2005Co-Authors: Gregory J Mccormick, Ian G Cox, Jason Porter, Scott MacraeAbstract:Purpose To investigate the distribution of the eye's higher-order aberrations in postoperative Laser Refractive Surgery patients with visual complaints and highly irregular corneal shapes. Design Retrospective case–control study. Participants Thirty-three symptomatic postoperative LASIK and/or photoRefractive keratectomy eyes with subjective visual complaints not corrected by spectacles more than 6 months after Surgery are compared with 46 normal preoperative and 46 asymptomatic successful postoperative conventional LASIK eyes. Methods Postoperative wave aberrations were measured for each patient using a Shack-Hartmann wavefront sensor (Zywave, Bausch & Lomb, Rochester, NY) over a 6-mm pupil. These measurements were averaged across patients with similar corneal topographic diagnoses (central islands, decentered ablations, a new group termed baby bowties, and irregularly irregular corneas). Main Outcome Measures Higher-order aberrations and corneal topography. Results The average (±1 standard deviation) higher-order root-mean-square (rms) wavefront error values (third, fourth, and fifth orders) for the symptomatic patients was 1.31±0.58 μm. This was an average of 3.46 times greater than the average magnitude of normal preoperative eyes (mean rms, 0.38±0.14 μm), and an average of 2.3 times greater than the average magnitude of asymptomatic successful postoperative conventional LASIK eyes (mean rms, 0.58±0.21μm) over a 6-mm pupil. Higher-order rms wavefront error increased with pupil size, roughly doubling for every millimeter of increasing pupil diameter. On average, eyes with central islands (n = 6) had the most vertical coma (Z 3 −1 ; mean, −1.35±0.43 μm). Eyes with central islands and decentered ablations (n = 2) also had elevated amounts of spherical aberration (Z 4 0 ; means of 0.83±0.11μm and 0.69±0.29 μm, respectively) compared with successful postoperative LASIK eyes (mean of 0.42±0.20 μm). Eyes with a topographic central baby bowtie demonstrated the most secondary astigmatism (Z 4 2 and Z 4 −2 ; mean rms, 0.56±0.17 μm; n=3), despite the lowest average higher-order rms (mean, 0.84±0.05 μm) among symptomatic topographic subgroups. Eyes with irregularly irregular corneas had a mean higher-order rms of 1.10±0.39 μm. Conclusions Symptomatic postoperative Laser Refractive Surgery patients with irregular corneas have higher-order aberrations that are 2.3 to 3.5 times greater than asymptomatic postoperative LASIK and normal preoperative eyes, respectively. The higher-order aberrations seem to correlate with corneal topography.
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causes of spherical aberration induced by Laser Refractive Surgery
Journal of Cataract and Refractive Surgery, 2005Co-Authors: Geunyoung Yoon, Scott Macrae, David R Williams, Ian G CoxAbstract:Purpose To develop a corneal model to better explain how Refractive Surgery procedures induce spherical aberration. Setting Department of Ophthalmology and Center for Visual Science, University of Rochester, Rochester, New York, USA. Methods The preoperative cornea was modeled as a rotationally symmetric surface with various radii of curvature and asphericities. The postoperative cornea was defined as the difference between the preoperative cornea and an ablation thickness profile computed based on the Munnerlyn equation. A ray-tracing program and Zernike polynomial fitting were used to calculate the induced amount of spherical aberration assuming a fixed ablation depth per pulse or a variable ablation depth depending on the incidence angle of each pulse on the cornea. A biological eye model of the corneal surface change after Laser Refractive Surgery was also developed to explain the induced spherical aberrations after myopic and hyperopic treatments. Results The clinical data showed that positive spherical aberration was induced after myopic correction and negative spherical aberration increased after hyperopic correction. In contrast, assuming a fixed ablation depth per pulse, the theoretical prediction was that negative spherical aberration with myopic treatment and positive spherical aberration with hyperopic treatment would increase. However, when assuming a variable ablation depth per pulse caused by non-normal incidence of Laser spot on the cornea, the theoretically predicted induction of spherical aberration tends to fit better with the myopic and hyperopic clinical data. The effect of a variable ablation depth accounted for approximately half the clinically observed amount of spherical aberration. The biological model of the corneal surface change used to explain this remaining discrepancy showed the magnitude of the biological response in myopic correction is 3 times smaller than in hyperopic correction and that the direction of the biological response in hyperopic treatment is opposite that in myopic treatment. Conclusions This nontoric eye model, which separates the effects of differences in ablation efficiency and biological corneal surface change quantitatively, explains how spherical aberration is induced after myopic and hyperopic Laser Refractive Surgery. With the corneal topographic data, this model can be incorporated into the ablation algorithm to decrease induced spherical aberrations, improving the outcomes of conventional and customized treatments.
Shiva Mehravaran - One of the best experts on this subject based on the ideXlab platform.
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central corneal thickness measurement with pentacam orbscan ii and ultrasound devices before and after Laser Refractive Surgery for myopia
Journal of Cataract and Refractive Surgery, 2007Co-Authors: Hassan Hashemi, Shiva MehravaranAbstract:Purpose To determine the agreement in central corneal thickness (CCT) measurements between the gold standard method of ultrasound (US) pachymetry (UP-1000, Nidek) and 2 noncontact systems based on Scheimpflug imaging (Pentacam, Oculus) and scanning-slit topography (Orbscan II, Bausch & Lomb) in myopic eyes before and after Laser Refractive Surgery. Setting Noor Vision Correction Center, Tehran, Iran. Methods In this prospective study, 30 consecutive patients having Refractive Surgery for myopia were enrolled. All 60 eyes were examined with the 3 devices preoperatively and 6 weeks after Surgery; the US measurements were performed last. The Pentacam and Orbscan II CCT readings were compared with the US readings. Both the original and corrected Orbscan II readings were used in the analyses. Results The mean CCT readings with US, Pentacam, and Orbscan II were, respectively, 555 μm, 548 μm, and 580 μm before Surgery and 478 μm, 468 μm, and 474 μm after Surgery. Preoperatively, the 95% limits of agreement (LoA) with US were −31 μm and +19 μm for the Pentacam device and −5 μm and +57 μm for the Orbscan II device. Postoperatively, the LoA were −40 μm and +19 μm and −51 μm and +50 μm, respectively. Corrected Orbscan II measurements gave 95% LoA of −48 μm and +6 μm before Surgery and −85 μm and +5 μm after Surgery. Conclusions Refractive Surgery had a modest effect on the agreement between Pentacam readings and US measurements. With Orbscan II, the 95% LoA width nearly doubled after Surgery. Although the Pentacam seems to show better agreement than Orbscan II, especially after Refractive Surgery, it is not advisable to use the 3 devices interchangeably in every clinical situation.
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corneal changes after Laser Refractive Surgery for myopia comparison of orbscan ii and pentacam findings
Journal of Cataract and Refractive Surgery, 2007Co-Authors: Hassan Hashemi, Shiva MehravaranAbstract:Purpose To determine the agreement between scanning slit topography (Orbscan II, Bausch & Lomb) and Scheimpflug imaging (Pentacam, Oculus) in corneal elevation, corneal curvature, and anterior chamber depth (ACD) measurements before and after Laser Refractive Surgery for myopia and to compare the postoperative changes seen with these devices. Setting Noor Vision Correction Center, Tehran, Iran. Methods In a prospective observational case-series study, 23 consecutive myopic patients having Laser Refractive Surgery were examined with the Orbscan II and Pentacam preoperatively and 6 weeks postoperatively. Readings of ACD, anterior (A-) and posterior (P-) best-fit sphere (BFS) size, central elevation (CE), maximum elevation (ME), axial power in the 3.0 mm zone (AX3) and 5.0 mm zone (AX5), and tangential power in these zones (TG3 and TG5, respectively) were collected and used in the analyses. Results Statistically significant interdevice differences were found preoperatively for all parameters except P-TG3 ( P = .014) and in operated eyes for ACD, anterior parameters of A-AX3 and A-AX5, and all posterior corneal parameters. In posterior corneal measurements, Orbscan II demonstrated significant postoperative changes in all parameters except P-AX5 ( P = .004) and P-TG5 ( P = .034), although none of the differences was statistically significant with the Pentacam. The devices measured similar postoperative changes in anterior curvature parameters and in P-AX5 and P-TG5; all other changes were significantly different. Conclusions Compared to the Pentacam, the Orbscan II yielded larger posterior elevation values before and after Surgery and significant postoperative changes in P-CE and P-ME. Further studies can determine which device gives more accurate images of the cornea and redefine screening criteria.
Graham D Barrett - One of the best experts on this subject based on the ideXlab platform.
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total keratometry in intraocular lens power calculations in eyes with previous Laser Refractive Surgery
Clinical and Experimental Ophthalmology, 2020Co-Authors: Michael Lawless, Chris Hodge, Gerard Sutton, James Y Jiang, Timothy V Roberts, Graham D BarrettAbstract:Importance Intraocular lens (IOL) calculations in post-Refractive cases remain a concern. Our study identifies improved options for surgeons. Background To evaluate and compare the prediction accuracy of IOL power calculation methods after previous Laser Refractive Surgery using standard keratometry (SK), measured posterior corneal astigmatism (PCA) and total keratometry (TK). Design Retrospective consecutive cohort. Participants A total of 50 consecutive patients (72 eyes) at a private institution who underwent cataract Surgery with prior Laser Refractive procedures. Methods Methods using SK included ASCRS mean, Barrett True-K no history, Haigis-L and Shammas IOL formulae. Barrett True-K using posterior values (True K TK), Haigis and Holladay 1 Double-K methods using TK were also assessed. Post-Surgery refraction was undertaken at minimum 3 weeks following Surgery. Main outcome measures Arithmetic and absolute IOL Refractive prediction errors, variances in mean arithmetic IOL prediction error, and percentage of eyes within ±0.25D, ±0.50D, ±0.75D and ±1.00D of Refractive prediction errors were compared. Results The Barrett True-K (TK) provided the lowest mean Refractive prediction error (RPE) and variance for both prior myopes and hyperopes undergoing cataract Surgery. The Barrett True-K (TK) exhibited the highest percentages of eyes within ±0.50D, ±0.75D and ±1.00D of the RPE compared to other formulae for prior myopic patients. Conclusions and relevance Accuracy of IOL power calculations in post-Laser eyes can be improved by the addition of posterior corneal values as measured by the IOLMaster 700. The use of total keratometry may supplement outcomes when no prior refraction history is known.
