Shady T. Awwad

Intraocular lens power calculation after myopic laser in situ keratomileusis: Estimating the corneal refractive power

PURPOSE: To derive regression‐based formulas and identify essential dependent variables to estimate refractive corneal power after myopic laser in situ keratomileusis (LASIK). SETTING: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. METHODS: A retrospective data review of 30 eyes (23 patients) having myopic LASIK followed by phacoemulsification and posterior chamber intraocular lens (IOL) implantation in the same eye gathered the following: pre‐LASIK and post‐LASIK refractions and topographies, axial length, IOL type and power, and spherical equivalent (SE) refraction 3 months after phacoemulsification. Using the double‐K Holladay 1 formula, the refractive corneal power in each eye was back‐calculated. Regression formulas were derived and compared with current corneal power estimation methods. RESULTS: The multiple regression formula based on the average corneal power in the central 3.0 mm area (ACCP3mm) and the change (Δ) in SE (SEpostLASIK − SEpreLASIK) was simplified to ACCPadj = ACCP3mm − 0.16ΔSE, with the highest Pearson correlation coefficient (r = 0.989) and lowest absolute corneal power estimation error (0.30 diopter [D] ± 0.30 (SD)). Regression based on ACCP3mm alone yielded 0.980 and 0.49 ± 0.40 D, respectively. Using SimK with ΔSE resulted in a lower r value (0.971) and larger absolute corneal power estimation error (0.65 ± 0.44 D) (P = .0014). The clinical history methods yielded 0.909 and 1.09 ± 0.868 D, respectively (P = .0005). CONCLUSION: The regression formula based on ACCP3mm and ΔSE was very accurate in predicting refractive corneal power after myopic LASIK followed by formulas based on ACCP3mm alone and SimK and ΔSE, all of which consolidate the validity of similar previously suggested methods, including EffRPadjusted.

Wavefront-guided LASIK for myopia using the LADAR CustomCornea and the VISX CustomVue.

PURPOSE To evaluate the objective and subjective visual outcomes and refractive results of wavefront-guided LASIK with LADAR CustomCornea and VISX CustomVue. METHODS This prospective randomized single-institution multisurgeon study comprised 100 eyes of 58 patients (50 eyes on each laser platform). Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction were measured postoperatively at 1 day, 1 week, 1 month, and 3 months. Contrast sensitivity, higher order aberrations measurement, and a subjective vision questionnaire were performed preoperatively and at 3 months. RESULTS Preoperatively, the CustomCornea group had a mean manifest sphere of -3.58 +/- 1.61 diopters (D) (range: -0.50 to -7.25 D), cylinder of +0.64 +/- 0.45 D (range: 0 to +1.75 D), and manifest refractive spherical equivalent (MRSE) of -3.26 +/- 1.56 D. The CustomVue group had a manifest sphere of -4.00 +/- 1.69 D (range: -1.50 to -7.50 D), cylinder of +0.60 +/- 0.52 D (range: 0 to +2.00 D), and MRSE of -3.70 +/- 1.64 D. At 3 months, 94% of CustomCornea eyes and 84% of CustomVue eyes had UCVA > or = 20/20 (P = .20). Twenty-four percent of CustomVue eyes and 22% of CustomCornea eyes gained 1 line of BSCVA. In both groups, 96% of eyes were within 0.50 D of emmetropia. Mean CustomCornea glare contrast sensitivity improved (P = .04) whereas more eyes improved than worsened in both groups. Spherical aberration and total higher order aberrations increased, and trefoil decreased in both groups. A decrease in coma was noted in 70% of CustomCornea eyes. CONCLUSIONS Wavefront-guided LASIK with both platforms is safe, effective, and delivers excellent visual results. CustomCornea improves contrast sensitivity under glare conditions.

A comparison of higher order aberrations in eyes implanted with AcrySof IQ SN60WF and AcrySof SN60AT intraocular lenses

Purpose. To evaluate the efficacy of AcrySof SN60WF aspheric intraocular lens (IOL) in decreasing spherical aberration and total higher order aberrations (HOAs) after cataract surgery compared to the spherical SN60AT lens. Methods. Wavefront analysis was conducted on 28 eyes of 28 patients that underwent uncomplicated phacoemulsification with implantation of either SN60WF (15 eyes) or SN60AT lenses (13 eyes). Eyes with a history of uveitis, retinal diseases, and previous surgery were excluded. Results. SN60WF eyes had less mean absolute spherical aberration than SN60AT eyes both at 4 mm (0.04±0.03 vs 0.11±0.03 RMS, p<0.0001) and 6 mm pupils (0.09±0.04 vs 0.43±0.12 RMS, p<0.0001). Mean total HOAs was lower in the SN60WF group at 6 mm pupils (0.44±0.14 vs 0.56±0.13 RMS, p=0.0274), while no difference was seen at 4 mm pupils (0.20±0.10 vs 0.25±0.08 RMS, p=0.160). There were no clinically significant differences between the SN60WF and SN60AT IOLs both at 4 and 6 mm pupils in terms of coma (0.16±0.07 vs 0.18±0.09 RMS, p=0.514 and 0.25±0.12 vs 0.23±0.12 RMS, p=0.664) and trefoil (0.14±0.09 vs 0.10±0.05 RMS, p=0.167 and 0.28±0.12 vs 0.23±0.07 RMS, p=0.199). There were no differences between groups in mean age, axial length, postoperative spherical equivalent, IOL power, or corneal curvature. Conclusions. An aspheric posterior optic IOL design with thinner center effectively reduces the positive ocular spherical aberration observed in the pseudophakic and elderly eyes, especially at larger pupillary diameters (6 mm), with no notable increase in coma. However, reduction in total ocular HOAs was only significant at 6 mm pupils.

Wavefront-guided Laser in situ Keratomileusis With the Alcon CustomCornea and the VISX CustomVue: Three-month Results

PURPOSE To evaluate and compare the visual and clinical outcomes of wavefront-guided laser in situ keratomileusis (LASIK) with the Alcon CustomCornea (Alcon Laboratories Inc, Fort Worth, Tex) and VISX CustomVue (VISX, Santa Clara, Calif) systems. METHODS Ninety-three eyes of 56 patients (50 and 43 consecutive eyes on CustomCornea and CustomVue, respectively) were enrolled in a prospective multisurgeon clinical outcome study. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction were measured at 1 day, 1 week, 1 month, and 3 months postoperatively. Early treatment diabetic retinopathy study (ETDRS) visual acuity and contrast sensitivity were measured at 1 month and 3 months, and wavefront mapping at 3 months. RESULTS Preoperatively, the CustomCornea group had a mean sphere of -3.90 +/- 1.62 diopters (D) (range -0.50 to -7.25 D), mean cylinder of +0.62 +/- 0.39 D (range 0 to +1.50 D), and mean manifest spherical equivalent refraction of -3.59 +/- 1.54 D. The CustomVue group had a sphere of -3.87 +/- 1.45 D (range -1.75 to -6.75 D), cylinder of +0.49 +/- 0.36 D (range 0 to +1.50 D), and manifest spherical equivalent refraction of -3.62 +/- 1.46 D. At 3 months, 98% of the CustomCornea group and 95% of the CustomVue group were within +/-0.50 D. Ninety-nine percent of eyes did not change >0.50 D (manifest spherical equivalent refraction) between 1 month and 3 months. CustomCornea eyes improved on contrast sensitivity testing and had a better profile than CustomVue for 20/15 Snellen and 20/12.5 ETDRS acuity. Both laser groups had a decrease in higher order aberrations with statistical significance for coma and spherical aberration in the CustomCornea group. CONCLUSION Wavefront-guided LASIK with both systems is safe and effective.

Intraocular lens power calculation after radial keratotomy : Estimating the refractive corneal power

PURPOSE: To evaluate the most accurate method for corneal power determination in patients with previous radial keratotomy (RK). SETTING: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. METHODS: A retrospective review of data for 16 eyes of 14 patients with a history of RK and subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation was performed. Outcome measures included axial length, postoperative topography, type and power of IOL implanted, and postoperative spherical equivalent (SE) refraction at 3 to 6 months. Average central corneal power (ACCP) was defined as the average of the mean powers of the central Placido rings. For each eye, simulated K‐readings and different values of ACCP computed corresponding to different central corneal diameters were used in each case, along with the implanted IOL power, to back‐calculate the SE refraction (Ref) via the double‐K adjusted Holladay 1 IOL formula. The predicted refractive error was hence computed as (Ref – SE), both in algebraic and absolute values. RESULTS: The ACCP over the central 3.0 mm (ACCP3mm) yielded the lowest absolute predicted refractive error (0.25 ± 0.38 diopters [D]), which was statistically lower than the error for ACCP1mm (P<.001) and for the simulated K‐value (P = .033). It also resulted in 87.5% of eyes being within ±0.50 D and 100% within ±1.00 D of the actual postoperative refraction. CONCLUSIONS: Corneal refractive power after RK was best described by averaging the topographic data of the central 3.0 mm area. Applying this method, together with a double‐K IOL formula, achieved excellent IOL power predictability.

Cataract surgery risk score for residents and beginning surgeons

tween the groups (P .317, Fisher exact probability test). Retinopathy progressed from 43 to 65 in 3 patients in the control group (Figure 1). Marked progression occurred in 5 (62.5%) of 8 eyes in the rapid-correction group with moderate to severe NPDR (P .0009, 2 test). We found no benefit of rapid preoperative correction in patients with poor glycemic control in preventing the progression of retinopathy after PEA. Significant postoperative progression was noted in patients in the rapid-correction group with moderate to severe preoperative NPDR. It is possible that this was caused by intensive treatment or rapid correction of glycemic control. We conclude that rapid preoperative improvement of glycemic control did not prevent postoperative progression of retinopathy after uneventful PEA. Additionally, care is needed in rapid preoperative glycemic correction in patients with moderate to severe NPDR.

Hyperopic laser in situ keratomileusis in eyes with previous radial keratotomy

PURPOSE: To assess the safety and efficacy of hyperopic laser in situ keratomileusis (LASIK) in eyes with previous radial keratotomy (RK). SETTING: Zale Lipshy University Hospital Laser Center for Vision, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: Thirty‐eight eyes of 25 patients were treated with LASIK for secondary hyperopia after RK using a Visx Star S2, S3, S4, or LADARVision excimer laser. Retreatment was done in 7 eyes. The main outcome measures were manifest refraction spherical equivalent (MRSE), uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), predictability of treatment, and complications. RESULTS: Preoperative mean MRSE was +2.39 diopters (D) ± 1.28 (SD) (range +0.87 to +6.00 D). At the last visit (25 eyes with minimum follow‐up of 12 months, including retreatments), the mean follow‐up was 23.3 ± 7.3 months (range 12 to 34 months), the mean MRSE was +0.11 ± 0.71 D, and the UCVA was 20/40 or better in 24 eyes (96%). Although no significant change in the mean MRSE was observed, the postoperative mean refractive cylinder showed a gradual increase over the follow‐up period. No eye lost more than 2 lines of BSCVA. CONCLUSIONS: Laser in situ keratomileusis was a safe and effective treatment with good predictability for the correction of consecutive hyperopia after RK. Cylindrical errors were difficult to correct, and astigmatic correction tended to regress over time. Retreatments are safe when old flaps were relifted.

Corneal intrastromal gatifloxacin crystal deposits after penetrating keratoplasty.

Background. An 85-year-old man developed faint crystallike white precipitates in the mid peripheral stroma of his left cornea 3 weeks after undergoing penetrating keratoplasty. The patient had been initially treated with 1% prednisolone acetate ophthalmic suspension and 0.3% gatifloxacin eyedrops to his left eye from the first day postoperatively. Three weeks later, the precipitates were more numerous, larger, and diffuse in distribution. Gatifloxacin was discontinued and substituted with a neomycin–polymixin B–dexamethasone ophthalmic ointment. Methods. A detailed history, physical examination, laboratory workup, and tandem scanning confocal microscopy were performed. Results. Tandem scanning corneal confocal microscopy confirmed the presence of crystals in the cornea. Conclusions. Gatifloxacin, a fourth-generation fluoroquinolone, can cause intrastromal macroscopic crystalline deposits through a compromised corneal epithelium, similar to what has been described for ciprofloxacin, a second-generation fluoroquinolone.

Corneal Refractive Power Estimation and Intraocular Lens Calculation after Hyperopic LASIK

PURPOSE To identify key independent variables in estimating corneal refractive power (KBC) after hyperopic LASIK. DESIGN Retrospective study. PARTICIPANTS We included 24 eyes of 16 hyperopic patients who underwent LASIK with subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation in the same eye. METHODS Pre-LASIK and post-LASIK spherical equivalent (SE) refractions and topographies, axial length, implant type and power, and 3-month postphacoemulsification SE were recorded. Using the double-K Hoffer Q formula, corneal power was backcalculated for every eye (KBC), regression-based formulas derived, and corresponding IOL powers calculated and compared with published methods. MAIN OUTCOME MEASURES The Pearson correlation coefficient (PCC) and arithmetic and absolute corneal and IOL power errors. RESULTS Adjusting either the average central corneal power (ACCP(3mm)) or SimK based on the laser-induced spherical equivalent change (DeltaSE) resulted in an estimated corneal power (ACCP(adj) and SimK(adj)) with highest correlation with KBC (PCC=0.940 and 0.956, respectively) and lowest absolute corneal estimation error (0.37+/-0.45 and 0.38+/-0.39 diopter [D], respectively). The ACCP(adj) closely mirrored published DeltaSE-based adjustments of central corneal power on different topographers, whereas DeltaSE-based SimK adjustments varied across platforms. Using ACCP(adj) or SimK(adj) in the double-K Hoffer Q, using ACCP(3mm) or SimK in single-K Hoffer Q and adjusting the resultant IOL power based on DeltaSE, or applying Maskets formula all yielded accurate and similar IOL powers. The Latkany method consistently underestimated IOL power. The Feiz-Mannis and clinical history methods yielded poor IOL correlations and large IOL errors. CONCLUSION After hyperopic LASIK, adjusting either corneal power or IOL power based on DeltaSE accurately estimates the appropriate IOL power.

Comparative higher-order aberration measurement of the LADARWave and Visx WaveScan aberrometers at varying pupil sizes and after pharmacologic dilation and cycloplegia

PURPOSE: To compare higher‐order aberration (HOA) measurements of LADARWave and Visx WaveScan aberrometers, to test the validity of the peripheral wavefront data, and to evaluate the effect of pharmacologic dilation and mild cycloplegia. METHODS: Thirty‐three myopic eyes of 17 volunteers were enrolled and had the ocular HOAs measured and analyzed with varying pupil diameters (PD) controlled by a tunable light intensity source and after instillation of tropicamide 1% and phenylephrine 2.5%. RESULTS: Higher‐order aberrations increased with PD and optical zone (OZ), especially an OZ between 6.0 mm and 6.5 mm. Spherical aberration increased the most, followed by coma, then trefoil and secondary astigmatism. Measurement differences were observed between LADARWave and WaveScan at an OZ of 6.0 mm, although measurement correlations between the 2 machines were high. In the case of the WaveScan, when PD = OZ (6.0 mm), the spherical aberration and, to a less extent, the coma data differed from those obtained with larger PDs and the same OZ. In the case of the LADARWave, at an OZ of 6.0 mm, the HOAs measured in eyes with physiologic pupils were similar to those in pharmacologically dilated pupils when the physiologic pupil center was taken as the reference. CONCLUSIONS: There were detectable measurement differences between LADARWave and Visx WaveScan. Ensuring that the PD is at least 0.5 mm larger than the desired OZ is very important. Dilation and mild cycloplegia did not clinically affect the wave measurement magnitude or pattern.