Michael C. Knorz

Femtosecond Laser Capsulotomy and Manual Continuous Curvilinear Capsulorrhexis Parameters and Their Effects on Intraocular Lens Centration

PURPOSE To measure and compare sizing and positioning parameters of femtosecond laser capsulotomy with manual continuous curvilinear capsulorrhexis (CCC). METHODS Femtosecond capsulotomies (Alcon-LenSx Lasers Inc) and CCC were carried out in 20 eyes of 20 patients, respectively. Intraocular lens (IOL) decentration, circularity, vertical and horizontal diameters of capsulotomies, and capsule overlap were measured with Adobe Photoshop (Adobe Systems Inc) 1 week, 1 month, and 1 year after surgery. Between-group differences of parameters and predictors of IOL decentration were determined with repeated measures analysis of variance, chi-square test, and logistic regression analyses. RESULTS Vertical diameter of CCC was statistically significantly higher in the first week and month. Significantly higher values of capsule overlap over 1 year and circularity in the first week showed more regular femtosecond capsulotomies. Horizontal IOL decentration was statistically significantly higher in the CCC group over 1 year. A significant difference was noted between the two groups in dichotomized horizontal decentration values at 0.4 mm with chi-square test after 1 week and 1 year (P=.035 and P=.016, respectively). In univariable general estimating equation models, type of capsulorrhexis (P<.01) and capsule overlap (P=.002) were significant predictors of horizontal decentration. Vertical diameter showed significant correlation to the overlap in the CCC group (1 week: r=-0.91; 1 month: r=-0.76, P<.01; 1 year: r=-0.62, P<.01), whereas no significant correlation was noted in the femtosecond group (P>.05). CONCLUSIONS More precise capsulotomy sizing and centering can be achieved with femtosecond laser. Properly sized, shaped, and centered femtosecond laser capsulotomies resulted in better overlap parameters that help maintain proper positioning of the IOL.

Comparison of Intraocular Lens Decentration Parameters After Femtosecond and Manual Capsulotomies

PURPOSE To evaluate a laser technique and manual technique to perform capsulorrhexis in cataract eyes. METHODS Anterior capsulotomy was performed with an intraocular femtosecond laser (LenSx Lasers Inc) in 54 eyes (FS group) and manual continuous curvilinear capsulorrhexis was performed in 57 eyes (CCC group). Circularity and area of capsulotomy and IOL decentration were measured using Photoshop CS4 Extended (Adobe Systems Inc) 1 week after surgery. Average keratometry, axial length, and preoperative anterior chamber depth were examined with the Lenstar LS 900 (Haag-Streit AG). RESULTS No statistically significant differences were noted between groups in axial length, preoperative refractive state, and in the area of capsulotomy. Circularity values were significantly better in the FS group (P=.032). We found incomplete overlap of capsulotomies in 28% of eyes in the CCC group and 11% in the FS group (P=.033). Significant correlations were noted between axial length and area of capsulotomy, and between average keratometry and area of the capsulotomy in the CCC group (R=0.278, P=.036; and R=-0.29, P=.033, respectively), but both did not correlate in the FS group (P>.05). In the CCC group, the pupillary area correlated significantly with the area of the capsulotomy (R=0.27, P=.039). Significant correlation was noted between IOL decentration and axial length in the CCC group (R=0.30, P=.026), but there was no correlation in the FS group (P>.05). CONCLUSIONS Femtosecond laser capsulorrhexis was more regularly shaped, showed better centration, and showed a better intraocular lens/capsule overlap than manual capsulorrhexis.

Laser in situ keratomileusis to correct myopia of -6.00 to -29.00 diopters.

BACKGROUND Photorefractive keratectomy can cause corneal scarring and visual loss in highly myopic eyes. We evaluated laser in situ keratomileusis (LASIK) because it has the theoretical advantage of preserving both the corneal epithelium and Bowmans layer. METHODS In a prospective study, LASIK was performed in 62 myopic eyes (42 patients) using the Automatic Corneal Shaper (Chiron Vision) and the Keracor 116 excimer laser (Chiron Technolas). We measured refraction and visual acuity, and evaluated corneal topography (TMS 1) and corneal clarity after 4 to 8 weeks and 4 to 6 months. RESULTS Four- to 6-month follow up was completed in 51 eyes. The mean preoperative spherical equivalent refraction was -14.80 diopters (D) (range, -6.00 to -29.00 D). Postoperatively, the mean deviation from the target refraction was -1.70 D (range, -9.00 to +2.50 D) at 4 to 8 weeks and -1.90 D (range, -9.50 to +2.25 D) at 4 to 6 months. At 4 to 6 months, 19 eyes (37%) were within +/- 0.50 D of the target refraction, 24 (47%) within +/- 1.00 D, 33 (65%) within +/- 2.00 D, and 40 (78%) within +/- 3.00 D. From 4 to 8 weeks to 4 to 6 months, the mean regression of myopia was -0.20 D (0.50 D or less in 24 eyes [47%], 1.00 D or less in 32 [63%], and 2.00 D or less in 42 [82%]). In six eyes (12%), the stromal interface was not visible, in 38 (74%) it was barely visible, and in seven (14%) it was clearly visible. Corneal topography revealed only small variations in clear-zone size and dioptric value, demonstrating a very stable correction 4 to 6 months postoperatively. CONCLUSIONS LASIK may be a safe and effective procedure to correct high myopia. Further research is required to develop satisfactory microkeratome technology, effective laser algorithms, and to determine long-term stability of refraction.

Central corneal volume and endothelial cell count following femtosecond laser-assisted refractive cataract surgery compared to conventional phacoemulsification

PURPOSE To compare the effect of conventional phacoemulsification and femtosecond laser-assisted cataract surgery on the cornea using Scheimpflug imaging and noncontact specular microscopy. METHODS In each group, 38 eyes (38 patients) underwent cataract surgery using either femtosecond laser-assisted (Alcon LenSx laser) (femtolaser group) or conventional phacoemulsification (phaco group). Central corneal thickness, 3-mm corneal volume, and Pentacam Nucleus Staging (PNS) were determined by a rotating Scheimpflug camera (Pentacam HR, Oculus Optikgeräte GmbH), and the volume stress index was calculated at 1 day and 1 month postoperatively. Endothelial cell count was measured by noncontact specular microscopy preoperatively, 1 day, 1 week, and 1 month postoperatively. RESULTS Central corneal thickness was significantly higher in the phaco group (607±91 μm) than in the femtolaser group (580±42 μm) on day 1, but did not differ significantly preoperatively and at 1 week and 1 month. Volume stress index at day 1 was significantly lower in the femtolaser group than in the phaco group (P<.05) but did not differ significantly at 1 month. Multivariate regression analysis showed that the type of surgery had a significant effect on central corneal thickness. CONCLUSIONS Femtosecond laser-assisted cataract surgery causes less corneal swelling in the early postoperative period and may cause less trauma to corneal endothelial cells than manual phacoemulsification.

Intraocular lens tilt and decentration measured by scheimpflug camera following manual or femtosecond laser-created continuous circular capsulotomy

PURPOSE To compare intraocular lens (IOL) decentration and tilt following a circular capsulotomy created with a femtosecond laser (laser CCC) to a manually performed continuous curvilinear capsulorrhexis (manual CCC). METHODS In a prospective, randomized study, a laser CCC (Alcon LenSx Inc) was performed in 20 eyes from 20 patients and a manual CCC was performed in 25 eyes from 25 patients. Intraocular lens decentration and tilt were measured using a Scheimpflug camera (Pentacam, Oculus Optikgeräte GmbH) 1 year after surgery. Uncorrected (UDVA) and corrected distance visual acuity (CDVA) and manifest refraction were also determined postoperatively. Between-group differences of IOL decentration and tilt as well as the correlation between IOL decentration and postoperative refractive changes and between IOL tilt and visual acuity were analyzed. RESULTS Horizontal and vertical tilt were significantly higher in the manual CCC group (P=.007 and P<.001, respectively). Lenses implanted after manual CCC showed greater horizontal and total decentration (P=.034 and P=.022, respectively). Significant differences were found in the homogeneity of dichotomized IOL vertical tilt and both horizontal and total decentration distribution (P=.008, P=.036, and P=.017, respectively). Total IOL decentration showed a significant correlation with changes in manifest refraction values between 1 month and 1 year after surgery (R=0.33, P=.032). A significant correlation was noted between IOL vertical tilt and CDVA (R(2)=0.17, β=-0.41, 95% confidence limit: -0.69 to -0.13, P=.005). CONCLUSIONS Continuous curvilinear capsulorrhexis created with a femtosecond laser resulted in a more stable refractive result and less IOL tilt and decentration than manual CCC.

Internal Aberrations and Optical Quality After Femtosecond Laser Anterior Capsulotomy in Cataract Surgery

PURPOSE To compare ocular and internal aberrations after femtosecond laser anterior capsulotomy and continuous curvilinear capsulorrhexis in cataract surgery. METHODS In this prospective study, anterior capsulotomy was performed during cataract surgery with an intraocular femtosecond (FS) laser (Alcon LenSx Inc) in 48 eyes. As a control group, continuous curvilinear capsulorrhexis (CCC) was performed in 51 eyes. Wavefront aberrometry, corneal topography, and objective visual quality were measured using the OPD-Scan (NIDEK Co Ltd). Vertical and horizontal tilt, coma, and visual quality metrics were evaluated separately to determine whether the source of aberrations was ocular or internal. Main outcome measures included postoperative residual refraction, uncorrected and corrected visual acuities, ocular and internal aberrations, Strehl ratio, and modulation transfer function (MTF). RESULTS No statistically significant differences were noted between the FS and CCC groups, respectively, in postoperative sphere (-0.60 ± 1.50 vs -0.50 ± 1.40 diopters [D]), postoperative cylinder (1.30 ± 1.01 vs 1.10 ± 1.10 D), uncorrected distance visual acuity (0.86 ± 0.15 vs 0.88 ± 0.08), or corrected distance visual acuity (0.97 ± 0.08 vs 0.97 ± 0.06). The FS group had significantly lower values of intraocular vertical tilt (-0.05 ± 0.36 vs 0.27 ± 0.57) and coma (-0.003 ± 0.11 vs 0.1 ± 0.15), and significantly higher Strehl ratios (0.02 ± 0.02 vs 0.01 ± 0.01) and MTF values at all measured cycles per degree, compared to the CCC group. CONCLUSIONS Capsulotomy performed with an intraocular FS laser induced significantly less internal aberrations measured by the NIDEK OPD-Scan aberrometer compared to eyes that underwent CCC, which may result in better optical quality after the procedure.

Cataract extraction with multifocal intraocular lens implantation: clinical, functional, and quality-of-life outcomes. Multicenter clinical trial in Germany and Austria.

Purpose: To compare bilateral implantation of a multifocal intraocular lens (IOL) versus a monofocal lens with respect to visual function, patient satisfaction, and quality of life. Setting: Seven clinical sites in Germany and 1 site in Austria. Methods: A prospective randomized masked clinical trial included 124 randomly assigned bilateral pseudophakic individuals, 64 of whom had bilateral implantation of an Array® foldable multifocal IOL (model SA‐40N, Allergan) and 60 of whom had bilateral implantation of an AMO®PhacoFlex II® silicone monofocal IOL (model SI‐40NB). Clinical data included binocular uncorrected and corrected distance and near visual acuities, complications, adverse events, and reports of halos and glare. Quality‐of‐life data were collected on 3 occasions using the modified Cataract TyPE Specification instrument. The functional status of the 2 groups was compared from baseline to final postoperative interview. Results: Three months after surgery, a higher proportion in the Array group achieved a Jaeger value of J3 (20/40 Snellen) or better uncorrected binocular near visual acuity and 0.5 (20/40) or better distance‐corrected binocular near visual acuity than in the monofocal groups (97% versus 68% and 95% versus 59%, respectively; P < .001). A higher proportion in the multifocal group achieved both 0.5 (20/40) and J3 or better uncorrected binocular distance and near visual acuities (97% versus 66%; P < .001). Those in the Array group were more likely than those in the monofocal group to never wear glasses overall (41% versus 12%; P < .001). Multifocal patients rated their vision without glasses better overall, at near and at intermediate distances (P < .05), and demonstrated better visual function for near tasks and social activities. Conclusions: Those who had bilateral implantation of the Array multifocal IOL obtained better uncorrected and distance‐corrected near visual acuities and reported better overall vision, less limitation in visual function, and less spectacle dependency than patients with bilateral monofocal IOLs.

Comparison of IOL power calculation and refractive outcome after laser refractive cataract surgery with a femtosecond laser versus conventional phacoemulsification

PURPOSE To compare intraocular lens (IOL) power calculation and refractive outcome between patients who underwent laser refractive cataract surgery with a femtosecond laser and those with conventional cataract surgery. METHODS In this prospective study, 77 eyes from 77 patients underwent laser refractive cataract surgery (laser group; Alcon LenSx femtosecond laser), and conventional cataract surgery with phacoemulsification was performed in 57 eyes from 57 patients (conventional group). Biometry was done with optical low coherence reflectometry (Lenstar LS900, Haag-Streit AG), and IOL calculation was performed with third-generation IOL formulas (SRK/T, Hoffer Q, and Holladay). The refractive outcome was analyzed using the mean absolute error (MAE; difference between predicted and achieved postoperative spherical equivalent refraction), and multivariable regression analysis was performed to compare the two groups. RESULTS No significant differences were found between age, axial length, keratometry, and preoperative corrected visual acuity in the laser and conventional groups (P>.05; Mann-Whitney U test). At least 6 weeks after surgery, MAE was significantly lower in the laser group (0.38±0.28 diopters [D]) than in the conventional group (0.50±0.38 D) (P=.04). The difference was the greatest in short (axial length <22.0 mm, 0.43±0.41 vs 0.63±0.48) and long (axial length >26.0 mm, 0.33±0.24 vs 0.63±0.42) eyes. CONCLUSIONS Laser refractive cataract surgery with a femtosecond laser resulted in a significantly better predictability of IOL power calculation than conventional phacoemulsification surgery. This difference is possibly due to a more precise capsulorrhexis, resulting in a more stable IOL position.

Topographically-guided laser in situ keratomileusis to treat corneal irregularities

OBJECTIVE To evaluate the predictability and safety of topographically guided laser in situ keratomileusis (LASIK) to treat corneal irregularities. DESIGN Prospective, noncomparative interventional case series. PARTICIPANTS Twenty-seven patients (29 eyes) with postsurgical corneal irregularities, divided into four subgroups (postkeratoplasty, 6 eyes; posttrauma, 6 eyes; postphotorefractive keratectomy (PRK)/LASIK with decentered or small ablations, 11 eyes; post-PRK/LASIK with central islands, 6 eyes). INTERVENTION LASIK was performed using the Automatic Corneal Shaper and the Keracor 117 C spot-scanning excimer laser (Bausch & Lomb Surgical Technolas, Munich, Germany). Individual ablation patterns were calculated on the basis of axial radii of curvature data obtained with the Corneal Analysis System (EyeSys Premier, Irvine, CA). MAIN OUTCOME MEASURES Change of corneal topography pattern, patient satisfaction, manifest spectacle refraction, and visual acuity at 12 months after surgery. RESULTS Corneal topography showed improved corneal regularity in 66% of eyes in the postkeratoplasty group, whereas 34% remained irregular. In the posttrauma group, 83% improved and 17% remained irregular. In the decentered/small optical zone group, 91 % improved and 9% remained irregular. In the central islands group, 50% improved and 50% remained irregular. Refractive cylinder decreased from 5.83 +/- 1.25 diopters (D) to 2.96 +/- 1.23 D in the postkeratoplasty group (P = 0.01), from 2.21 +/- 1.35 D to 0.50 +/- 0.84 D in the posttrauma group (P = 0.001), from 0.73 +/- 0.71 D to 0.36 +/- 1.05 D in the decentered/small optical zone group (NS), and from 1.42 +/- 1.13 D to 0.50 +/- 0.84 D in the central island group (P = 0.01). Uncorrected visual acuity improved from 20/200 +/- 0.07 to 20/50 +/- 0.17 in the postkeratoplasty group (P = 0.01), from 20/83 +/- 0.12 to 20/50 +/- 0.28 in the posttrauma group (P = 0.01), from 20/60 +/- 0.16 to 20/50 +/- 0.29 in the decentered/small optical zone group (NS), and from 20/71 +/- 0.12 to 20/60 +/- 0.24 in the central island group (NS). CONCLUSIONS The topographically-guided LASIK method used in this study resulted in a significant reduction of refractive cylinder, a significant increase of uncorrected visual acuity, and improved corneal regularity in a large percentage of patients with severe corneal irregularities such as decentered/small optical zones after LASIK or irregular astigmatism after keratoplasty or trauma. With small irregularities such as central islands, results were sufficiently poor to advise against the use of our technique in these patients.

Laser in situ Keratomileusis for Hyperopia and Hyperopic Astigmatism

PURPOSE To evaluate the efficacy, stability, and safety of laser in situ keratomileusis (LASIK) for hyperopia and hyperopic astigmatism using a prospective clinical trial. METHODS LASIK was performed using the Automatic Corneal Shaper and the Keracor 117C excimer laser on 192 hyperopic eyes with astigmatism of less than 1.00 D (spherical group) and 164 hyperopic eyes with corneal astigmatism of 1.00 to 7.50 D (toric group). RESULTS At 12 months after LASIK, 110 eyes were available for follow-up examination. In low spherical hyperopia (+1.00 to +3.00 D), 13 eyes (55%) were within +/-0.50 D of emmetropia and none lost 2 or more lines of spectacle-corrected visual acuity. In low toric hyperopia (+1.00 to +3.00 D), 14 eyes (61%) were within +/-0.50 D and none lost 2 or more lines of spectacle-corrected visual acuity. In moderate spherical hyperopia (+3.10 to +5.00 D) 9 eyes (44%) were within +/-0.50 D and none lost 2 or more lines of spectacle-corrected visual acuity and in moderate toric hyperopia (+3.10 to +5.00 D) 5 eyes (36%) were within +/-0.50 D and 2 eyes (14%) lost 2 or more lines of spectacle-corrected visual acuity. In high spherical hyperopia (+5.10 to +9.00 D), 6 eyes (38%) were within +/-0.50 D and 2 eyes (13%) lost 2 or more lines of spectacle-corrected visual acuity, and in high toric hyperopia (+5.10 to +9.50 D) 4 eyes (31%) were within +/-0.50 D and 2 eyes (15%) lost 2 or more lines of spectacle-corrected visual acuity. CONCLUSIONS LASIK seems to be reasonably effective and safe in spherical hyperopia of +1.00 to +5.00 D but less effective for hyperopic astigmatism. For hyperopia greater than +5.00 D, loss of spectacle-corrected visual acuity occurred in a significant number of eyes and accuracy was sufficiently poor to advise against LASIK in these eyes.