Corneal interactive programmed topographic ablation customized photorefractive keratectomy for correction of postkeratoplasty astigmatism

Safety and efficacy of a laser refractive procedure in eyes with previous keratoplasty: systematic review and meta-analysis

Post-keratoplasty (KP) patients' visual acuity can be severely limited by ametropia. Irregular astigmatisms are frequently encountered in these patients and is commonly associated with high degrees of hyperopia or myopia. This systematic review investigates the safety and efficacy of laser refractive surgery for post KP vision correction. 31 studies with 683 participants (732 eyes) enrolled in this review. Mean astigmatism improved significantly (mean difference [MD] = -2.70, 95% CI, -3.13 to -2.28, P < .0001). As well as Mean spherical equivalent (MD = -3.35, 95% CI, -3.92 to -2.78, P < .0001). From 586 participants 5.8% lost 2 or more lines of corrected distance visual acuity after treatment. The proportion of eyes with 20/40 uncorrected distance visual acuity or better was reported and the percentage was 46.79% overall. Laser refractive procedures (laser in situ keratomileusis [LASIK] or photorefractive keratectomy [PRK] or transepithelial PRK) on eyes with corneal transplantation were found to be relatively safe and effective. Our systematic review shows there is improvement in all outcomes. Main adverse effects were haze for PRK and epithelial ingrowth for LASIK.

Femto-LASIK after Deep Anterior Lamellar Keratoplasty to Correct Residual Astigmatism: A Long-Term Case Series Study

Purpose: To evaluate the long-term outcomes of femtosecond laser-assisted in situ keratomileusis (Femto-LASIK) to correct residual astigmatism after deep anterior lamellar keratoplasty (DALK). Methods: This retrospective case series study included 10 eyes that underwent Femto-LASIK after a DALK. The refractive error, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, thinnest corneal thickness (TCT), and central corneal thickness (CCT) were registered. The postoperative follow-up ranged between 36 and 60 months. Results: All surgeries were uneventful, with no intra- or postoperative complications. The mean UDVA (Snellen scale) rose from 0.13 ± 0.05 to 0.47 ± 0.15 six months after Femto-LASIK (p < 0.001). All cases experienced a significant improvement in UDVA. None of the eyes lost lines of CDVA, and seven eyes (70%) improved the CDVA compared to preoperative values. The refractive cylinder changed from a preoperative value of −3.88 ± 1.00 D to −0.93 ± 0.39 six months after Femto-LASIK (p < 0.0001). In eight eyes (80%), the UDVA and refractive outcomes remained stable at postoperative follow-up visits. In contrast, one eye experienced a refractive regression over the follow-up. TCT and CCT were stable at the different postoperative follow-up visits. Conclusions: Our findings suggest that Femto-LASIK might safely and effectively corrects residual astigmatism after DALK. Despite these encouraging results, further long-term studies, including a larger number of cases, are required to confirm the safety of the procedure. The refractive stability in eyes with prior RK might be lower than for other DALK indications.

Topography-guided custom ablation treatment for treatment of keratoconus

Keratoconus is a progressive ectatic disorder of the cornea which often presents with fluctuating refraction and high irregular astigmatism. Correcting the vision of these patients is often a challenge because glasses are unable to correct the irregular astigmatism and regular contact lenses may not fit them very well. Topography-guided custom ablation treatment (T-CAT) is a procedure of limited ablation of the cornea using excimer laser with the aim of regularizing the cornea, improving the quality of vision and possibly contact lens fit. The aim of the procedure is not to give a complete refractive correction. It has been tried with a lot of success by various groups of refractive surgeons around the world but a meticulous and methodical planning of the procedure is essential to ensure optimum results. In this paper, we attempt to elucidate the planning for a T-CAT procedure for various types of cones and asphericities.

Clinical results of topography-based customized ablations for myopia and myopic astigmatism

PURPOSE

To evaluate clinical outcomes after primary treatments for myopia and myopic astigmatism with topography-based ablation profiles on the Allegretto Wave Eye-Q platform (Alcon Laboratories Inc).

METHODS

Records of patients who underwent topography-guided, Q-adjusted LASIK were retrieved and analyzed. Patients with mean refractive spherical equivalent up to -16.00 diopters (D) and cylindrical errors up to 6.00 D were included (2051 eyes). Refractive outcomes and visual acuities were analyzed preoperatively and 3 months postoperatively.

RESULTS

Manifest spherical refractive error decreased from -5.05 +/- 2.33 to +0.04 +/- 0.35 D. Manifest cylindrical refractive error decreased from 0.83 +/- 0.75 to 0.23 +/- 0.22 D. At 3 months postoperatively, 86.1% (1766 eyes) had a spherical equivalent refraction within +/- 0.50 D of targeted refraction. The number of eyes with uncorrected distance visual acuity of 20/16 and 20/20 was 851 (41.5%) and 1495 (72.9%), respectively. At 3 months, 0.10% (2 eyes) lost more than 2 lines of corrected distance visual acuity and a loss of 2 lines occurred in 0.24% (5 eyes). All patients who lost lines of visual acuity were found to have corneal erosions related to dryness and recovered vision on further follow-up.

CONCLUSIONS

The results of this retrospective study demonstrate refractive predictability, efficacy, and safety comparable to other treatment modalities such as wavefront-optimized and wavefront-guided treatments. Results are also similar to those reported with other topography-guided systems.

Visual outcomes of topography-guided excimer laser surgery for treatment of patients with irregular astigmatism

The aim of this study was to evaluate the efficacy, safety, and predictability of topography-guided treatments to enhance refractive status following other corneal surgical procedures. In a prospective case series study, 28 consecutive eyes of 26 patients with irregular astigmatism after radial keratotomy, corneal transplant, small hyperopic and myopic excimer laser optical zones, and corneal scars were operated. Laser-assisted in situ keratomileusis (LASIK) (n = 8) and photorefractive keratectomy (PRK) (n = 20) were performed using the ALLEGRETTO WAVE excimer laser and topography-guided customized ablation treatment software. Preoperative and postoperative uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), manifest and cycloplegic refraction, and corneal topography with asphericity were analyzed in 12 months follow-up. Uncorrected visual acuity (UCVA) changed from 0.2 ± 0.2 or (20/100 ± 20/100) to 0.51 ± 0.31 or (20/40 ± 20/60) in the LASIK group (P = 0.01) and from 0.34 ± 0.16 or (20/60 ± 20/120) to 0.5 ± 0.23 or (20/40 ± 20/80) in the PRK group (P = 0.01). Refractive cylinder decreased from -3.2 ± 0.84 diopters (D) to -2.06 ± 0.42 D in the LASIK group (P = 0.07) and from -2.25 ± 0.39 D to -1.5 ± 0.23 D in the PRK group (P = 0.008). Best corrected visual acuity did not change significantly in either group. Topography-guided treatment is effective in correcting the irregular astigmatism after refractive surgery. Topography-guided PRK can significantly reduce irregular astigmatism and increase the UCVA and BCVA.

Photorefractive keratectomy followed by cross-linking versus cross-linking alone for management of progressive keratoconus: two-year follow-up

PURPOSE

To compare visual, refractive, topographic, and corneal higher-order aberration outcome at the 2-year follow-up after customized photorefractive keratectomy (PRK) followed by cross-linking (CXL) as a single procedure versus CXL alone in eyes with progressive keratoconus.

DESIGN

Prospective, interventional, nonrandomized clinical trial.

METHODS

Seventeen patients (34 eyes) with progressive keratoconus were assigned to 2 groups: the worse eye (17 eyes) was assigned to the PRK plus CXL group and the better eye (17 fellow eyes) was assigned to the CXL group.

RESULTS

In the PRK plus CXL group, uncorrected distance acuity improved significantly, from a mean ± standard deviation of 0.63 ± 0.36 logarithm of the minimal angle of resolution (logMAR) units to 0.19 ± 0.17 logMAR units (P < .05) and best distance acuity from 0.06 ± 0.08 logMAR to 0.03 ± 0.06 logMAR (P < .05). Manifest refraction spherical equivalent and spherical and cylindrical power improved significantly (P < .05). Simulated keratometry, flattest, steepest, average, cylindrical, apex keratometry, and inferior-superior value decreased significantly (P < .05). Total and coma-like aberrations significantly decreased for all pupil diameters (P < .05). In the CXL group, uncorrected distance acuity improved, but not significantly, from 0.59 ± 0.29 logMAR units to 0.52 ± 0.29 logMAR units, and best distance acuity improved from 0.06 ± 0.11 logMAR units to 0.04 ± 0.07 logMAR units (P > .05). Manifest refraction spherical equivalent and cylindrical power improvement was not significant (P > .05), unlike spherical power (P < .05). Steepest simulated keratometry, average simulated keratometry, and inferior-superior value significantly decreased (P < .05), unlike flattest simulated keratometry, cylindrical simulated keratometry, and apex keratometry (P > .05). Total and coma-like aberrations were not decreased significantly for all pupil diameters (P > .05). No significant endothelial changes were observed in either group.

CONCLUSIONS

The PRK plus CXL procedure may be a good option to reduce corneal aberrations and stabilize corneas with progressive keratoconus.

Simultaneous topography-guided PRK followed by corneal collagen cross-linking after lamellar keratoplasty for keratoconus

BACKGROUND

The purpose of this paper is to report the results of using combined treatment of customized excimer laser-assisted photorefractive keratectomy (PRK) and prophylactic corneal collagen crosslinking (CXL) for residual refractive error in a group of patients who had previously undergone lamellar keratoplasty for keratoconus.

METHODS

The study included 14 eyes from 14 patients who had originally been treated for keratoconus in one eye by excimer laser-assisted lamellar keratoplasty (ELLK), and subsequently presented with residual ametropia (-6.11 D ± 2.48, range -2.50 to -9.50). After a mean 40.1 ± 12.4 months since ELLK they underwent combined simultaneous corneal regularization treatment with topographically guided transepithelial excimer laser PRK (central corneal regularization) and corneal CXL induced by riboflavin-ultraviolet A.

RESULTS

After a mean 15 ± 6.5 (range 6-24) months, all eyes gained at least one Snellen line of uncorrected distance visual acuity (range 1-10). No patient lost lines of corrected distance visual acuity, and four patients gained three lines of corrected distance visual acuity. Mean manifest refractive spherical equivalent was -0.79 ± 2.09 (range +1 to -3.0) D, and topographic keratometric astigmatism was 5.02 ± 2.93 (range 0.8-8.9) D. All the corneas remained clear (haze < 1).

CONCLUSION

The combination of customized PRK and corneal CXL provided safe and effective results in the management of corneal regularization for refractive purposes after ELLK for keratoconus.

Phacoemulsification and customized toric intraocular lens implantation in eyes with cataract and high astigmatism after penetrating keratoplasty

Phacoemulsification and implantation of a hydrophilic acrylic toric intraocular lens (IOL) (T-flex 623T) with customized cylindrical power was performed in 1 eye in 3 consecutive patients with cataract and high postkeratoplasty astigmatism (range 6.75 to 8.75 diopters [D]). Twelve months postoperatively, the uncorrected distance visual acuity improved from 20/200 to 20/30 in Case 1, from 20/400 to 20/40 in Case 2, and from 20/200 to 20/25 in Case 3 and the corrected distance visual acuity was 20/25 or better in all 3 eyes. The spheroequivalent was within ± 0.50 D of the intended value and the refractive astigmatism was less than 1.00 D. The corneal grafts were transparent, and the endothelial cell loss range was 6% to 12%. Rotation of the toric IOL was less than 5 degrees. The toric IOL with customized cylindrical power provided good postoperative rotational stability and very satisfactory postoperative visual recovery. This type of toric IOL is appropriate to correct high postkeratoplasty astigmatism in eyes operated on for cataract.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Combined corneal topography and corneal wavefront data in the treatment of corneal irregularity and refractive error in LASIK or PRK using the Carl Zeiss Meditec MEL 80 and CRS-Master

PURPOSE

To assess the efficacy, safety, and accuracy of TOSCA II (Topography Supported Custom Ablation) treatments for the correction of high corneal aberrations and refractive error following previous ocular surgery.

METHODS

Forty-eight eyes of 32 patients were included for study. Indications for TOSCA II treatment included small optical zone, decentered ablation, subjective visually significant higher order aberrations, and irregularly irregular astigmatism induced by LASIK, photorefractive keratectomy, radial keratotomy, conductive keratoplasty, cataract surgery, and deep lamellar keratoplasty. An ablation profile based on corneal topography data and corneal wavefront and manifest refraction was created using the CRS-Master software (Carl Zeiss Meditec) to treat corneal irregularity and refractive error simultaneously. Postoperative assessments were performed at 1 week and 1, 2, 3, 6, and 12 months.

RESULTS

Mean attempted spherical equivalent refraction (SE) was -1.12 +/- 1.97 diopters (D) (range: +1.13 to -10.50 D). Mean attempted cylinder correction was 1.34 +/- 1.65 D (range: 0.00 to 7.75 D). Median age was 38 years (range: 19 to 68 years). Median follow-up was 9.4 months. Accuracy: mean deviation from the intended SE correction was -0.19 +/- 0.94 D, 60% of eyes were within +/- 0.50 D and 77% of eyes were within +/- 1.00 D of the intended SE. Cylinder: the correction ratio was 1.49 +/- 0.85 and the error ratio was 0.87 +/- 0.69.

EFFICACY

56% of eyes achieved uncorrected visual acuity of 20/20 or better and 88% achieved 20/40 or better.

SAFETY

34% of eyes gained one or more lines of best spectacle-corrected visual acuity, 15% lost one line, and no eye lost two or more lines. Contrast sensitivity: for the subset of eyes with below normal contrast sensitivity preoperatively, there was a statistically significant improvement in contrast sensitivity at 3 cycles per degree (cpd), 6 cpd, and 12 cpd (P < .05). Stability: the average change in refraction between 3 months and 1year was +0.38 +/- 0.30 D. Higher order aberrations: the average higher order root-mean-square decreased by 21% and the average spherical aberration decreased by 41%.

CONCLUSIONS

The MEL 80 CRS-Master TOSCA II software appears to be an effective treatment for decentrations, optical zone enlargement, and reduction of higher order aberrations. The refractive outcome was satisfactory after one treatment.

Topographically guided two-step LASIK and standard LASIK in the correction of refractive errors after penetrating keratoplasty

PURPOSE

To evaluate in a long-term period the effectiveness and safety of topographically guided two-step laser in situ keratomileusis (LASIK) and standard LASIK technique in the correction of refractive errors after successful penetrating keratoplasty (PKP) for keratoconus.

METHODS

At least 2 years after PKP and 6 months after removal of all sutures, 15 eyes of 15 patients (Group 1; mean manifest refraction spherical equivalent (MRSE) -7.23 D -/+ 3.42 SD) were submitted to standard LASIK and 15 eyes of 15 patients (Group 2; mean MRSE -4.37 D -/+ 1.97 SD) to a topographically guided two-step LASIK procedure (first the flap and at least 2 weeks later the laser ablation). In all cases, a superior hinged corneal flap(160 microm/9.5 mm) was created.

RESULTS

After a follow-up of 36 months, in Group 1 the mean uncorrected visual acuity (UCVA) was 0.51 logarithm of the minimum angle of resolution (logMAR) -/+ 0.41 SD and the mean best-corrected visual acuity (BCVA) was 0.03 logMAR -/+ 0.05 SD, with a mean MRSE of -1.57 D -/+ 2.65 SD. In Group 2, the mean UCVA was 0.28 logMAR -/+ 0.24 SD and the mean BCVA was 0.01 logMAR -/+ 0.03 SD, with a mean MRSE of -0.07 D -/+ 1.00 SD. In both groups, no complications were observed.

CONCLUSIONS

After a long follow-up period, both topographically guided two-step LASIK and standard LASIK could be considered effective and safe tools in the correction of refractive errors after successful PKP for keratoconus.

Topography-guided treatment of decentered laser ablation using LaserSight's excimer laser

PURPOSE

To assess the efficacy of topography-guided laser ablation for correction of previously decentered laser ablation using LaserSight's excimer laser.

METHODS

Re-treatment was performed to correct decentered ablation using LaserSight's excimer laser for 18 patients who previously underwent LASIK surgery for myopia correction in both eyes. For each patient, only the decentered eye was re-treated while the other asymptomatic eye forms a control group for this study. Measurements were conducted on ablation center, best spectacle-corrected visual acuity (BSCVA), contrast sensitivity and corneal aberrations pre- and post-operatively.

RESULTS

For the retreated 18 eyes, the mean decentration was significantly reduced from 1.32+/-0.28mm to 0.61+/-0.23mm post-operatively (t=16.24, p<0.001), and with a significant improvement in mean BSCVA from 0.08+/-0.09 logMAR to 0.01+/-0.11 logMAR (t=4.58, p<0.001). The post-operative contrast sensitivity at the spatial frequencies (SF) of 1.00 and 0.70 was significantly improved (p<0.05 for both SFs). Corneal higher-order aberrations (HOAs), including the coma-like aberrations and spherical aberration, were decreased. In comparing the measurements for the retreated group to those for the control group, no significant differencewas found either in decentration or in BSCVA, but the contrast sensitivity at 0.70 was lower and the level of corneal aberrations was higher.

CONCLUSIONS

Topography-guided ablation with LaserSight excimer laser is effective to correct decentered ablation. However, the re-treated eye is still inferior to the eye with originally centered ablation in corneal optical quality or visual performance.

Advances in technologies for laser-assisted in situ keratomileusis (LASIK) surgery

Laser-assisted in situ keratomileusis (LASIK) has become the most widely used form of refractive surgery today. The objective of this surgical technique is to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. This way, we are able to change the refractive status of the patient, providing better unaided vision. Continuous improvements in the original technique have made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are the responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon, and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. This article aims to describe the more relevant advances in LASIK that have played an important role in the spread and popularity of this technique.

Topographic Customized Photorefractive Keratectomy for Regular and Irregular Astigmatism After Penetrating Keratoplasty Using the LIGI CIPTA/LaserSight Platform

PURPOSE

To evaluate the use of a software ablation program (Corneal Interactive Programmed Topographic Ablation [CIPTA]) that provides customized photorefractive keratectomy (PRK) to correct astigmatism after keratoplasty.

METHODS

In this prospective, noncomparative, consecutive case series, 44 eyes underwent CIPTA for correction of astigmatism after penetrating keratoplasty. Eighteen eyes were treated for regular astigmatism and 26 eyes were treated for irregular astigmatism after penetrating keratoplasty. Orbscan II topography (Bausch & Lomb) and a flying-spot laser (LaserScan 2000; LaserSight) were used. Epithelial debridement with alcohol was performed before PRK in 16 eyes and transepithelial PRK was performed in 28 eyes. Mean target-induced astigmatism was 8.19 +/- 2.68 diopters (D) and 7.68 +/- 4.50 D in the regular and irregular astigmatism groups, respectively.

RESULTS

Mean follow-up was 25.4 +/- 13 months. At last postoperative follow-up, 13 (72.2%) and 18 (69.2%) eyes in the regular and irregular astigmatism groups, respectively, had uncorrected visual acuity (UCVA) better than 20/40. Four (22.2%) and 8 (30.7%) eyes in the regular and irregular astigmatism groups, respectively, had UCVA of 20/20. Fourteen (77.7%) and 18 (69.2%) eyes in the regular and irregular astigmatism groups, respectively, were within 1.00 D of attempted correction in spherical equivalent manifest refraction. No eye lost Snellen lines of best spectacle-corrected visual acuity. Mean surgically induced astigmatism was 7.66 +/- 2.70 D and 6.99 +/- 3.80 D for the regular and irregular astigmatism groups, respectively. Index of success of astigmatic correction was 0.138 and 0.137 for the regular and irregular astigmatism groups, respectively. Haze developed in three eyes.

CONCLUSIONS

Topography-driven PRK using CIPTA software is a suitable solution for correcting regular and irregular astigmatism after penetrating keratoplasty.

Customized transepithelial photorefractive keratectomy for iatrogenic ametropia after penetrating or deep lamellar keratoplasty

PURPOSE

To evaluate the safety and efficacy of customized transepithelial photorefractive keratectomy (PRK) for the correction of iatrogenic ametropia after penetrating keratoplasty (PKP) or deep lamellar keratoplasty.

SETTING

Eye Clinic, Department of Neurological and Visual Sciences, University of Verona, Verona, Italy.

METHODS

This study comprised 9 patients who had irregular astigmatism from 2.0 to 8.0 diopters (D) after PKP or deep lamellar keratoplasty. The ametropia was corrected with customized transepithelial PRK and the Corneal Interactive Programmed Topographic Ablation (CIPTA) software program (LIGI). Complete ophthalmic examinations were performed before and after surgery.

RESULTS

The mean age of the patients was 39.2 years (range 31 to 59 years). All patients gained at least 2 Snellen lines of uncorrected visual acuity; 2 patients had an increase of at least 5 lines, and 3 patients had an increase of 8 lines. The mean refractive spherical equivalent changed from -2.98 D +/- 3.11 (SD) (range -7.25 to +3.00 D) before PRK to -0.58 +/- 0.84 D (range 0 to -2.50 D) at the last follow-up visit. One patient presented with grade 1 haze that did not improve with topical steroid therapy. No patient lost best spectacle-corrected visual acuity.

CONCLUSION

Customized transepithelial PRK with the CIPTA software was a safe and effective treatment for irregular astigmatism after PKP or deep lamellar keratoplasty.

Topography-guided customized laser-assisted subepithelial keratectomy for the treatment of postkeratoplasty astigmatism

PURPOSE

To assess topography-assisted corneal wavefront excimer laser surface ablation for the correction of ametropia and irregular astigmatism after keratoplasty.

SETTING

Department of Ophthalmology, St. Thomas' Hospital, London, United Kingdom.

METHODS

In this pilot study, 15 patients (16 eyes) who were intolerant of spectacle and contact lens correction due to astigmatic anisometropia after keratoplasty (15 penetrating and 1 lamellar) had topography-assisted customized excimer laser treatments. Corneal topographic data using a Keratron Scout, Placido disk system allowed for preoperative analysis of wavefront anomalies of the anterior corneal surface from which a customized excimer laser correction of both lower-order aberrations (LOAs) and higher-order aberrations (HOAs) was prepared (ORK software) for treatment with a Schwind Esiris flying-spot laser. All eyes had laser-assisted subepithelial keratectomy (LASEK) using 15% alcohol with a 20-second to 30-second application. Four eyes received an application of mitomycin-C (MMC) 0.2 mg/mL for 1 minute after stromal ablation.

RESULTS

The mean preoperative spherical equivalent (SE) was -3.50 diopters (D) +/- 3.97 (SD) (range +1.625 to -9.25 D). The preoperative cylindrical error was -7.2 D (range -2.75 to -13.5 D). The programmed laser correction was -3.14 D (range +1.62 to -9 D) with a maximum attempted cylindrical correction of -7 D. Adherent LASEK epithelial flaps along suture lines and the graft-host junction were noted in 9 eyes (56%), although it was possible to obtain and replace a partial flap. A follow-up of 18 months was achieved in all eyes. At the final follow-up visit, the mean postoperative SE was -1.08 +/- 1.85 D (range +3 to -4.78 D) (P<.01, F<.01). Ten eyes (62.5%) were within +/-1 D of the intended correction. The mean postoperative cylindrical error was -2.72 D (range -0.5 to -6.5 D) (P<.001), with vector analysis demonstrating a mean 6.23 D correction. Analysis of HOAs using a 6.0 mm pupil size demonstrated a significant reduction of higher-order root mean square (RMS) (P<.002), trefoil (P<.005), and 4th-order spherical aberration (P<.02) at 18 months compared with preoperative values. Uncorrected visual acuity improved in all eyes (P<.0001). Best spectacle-corrected visual acuity was unchanged or improved in 13 eyes (81%) and worse in 2 eyes by 1 line; 1 eye lost 3 lines due to an increase in preexisting cataract. In eyes that did not receive MMC, corneal haze (grade II to IV) was encountered in 3 eyes (27%). One eye required phototherapeutic keratectomy with MMC application at 12 months. Of the 4 eyes treated with MMC, 1 had trace haze and 3 had no detectable haze. There were no reported cases of epithelial instability, ectasia, or graft rejection.

CONCLUSIONS

Topography-assisted customized LASEK was effective in the correction of postkeratoplasty astigmatism. A significant improvement of both LOAs and HOAs was obtained with good refractive stability for over 18 months. Iatrogenic haze typically occurred but appeared to be minimized with adjunctive use of intraoperative MMC.

Topography-guided Treatment of Irregular Astigmatism With the WaveLight Excimer Laser

PURPOSE

To evaluate the feasibility, safety, and predictability of correcting high irregular astigmatism in symptomatic eyes with the use of topography-guided photoablation.

METHODS

In a prospective, non-comparative case series, 16 consecutive symptomatic eyes of 11 patients with small hyperopic and myopic excimer laser optical zones, decentered and irregular ablation after corneal graft, and corneal scars were operated. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest and cycloplegic refraction, and corneal topography, with asphericity and regularity, were analyzed. LASIK (n = 10) and photorefractive keratectomy (n = 6) were performed using the ALLEGRETTO WAVE excimer laser and T-CAT software (Topography-guided Customized Ablation Treatment; WaveLight Laser Technologie AG, Erlangen, Germany).

RESULTS

In the LASIK group, UCVA improved from 0.81 +/- 0.68 IogMAR (20/130) (range: 0.2 to 2.0) to 0.29 +/- 0.21 logMAR (20/39) (range: 0.1 to 0.7) at 6 months. In the PRK group, mean UCVA improved from 0.89 +/- 0.87 IogMAR (20/157) (range: 0.1 to 2.0) to 0.42 +/- 0.35 logMAR (20/53) (range: 0.1 to 1.0) at 6 months. Best spectacle-corrected visual acuity did not change significantly in either group. One PRK patient lost one line of BSCVA. Refractive cylinder for the LASIK group improved from -2.53 +/- 1.71 diopters (D) (range: -0.75 to -5.75 D) to -1.28 +/- 0.99 D (range: 0 to -2.50 D) at 6 months. Refractive cylinder in the PRK group improved from -2.21 +/- 2.11 D (range: -0.25 to -5.50 D) to -1.10 +/- 0.42 D (range: -0.50 to -1.50 D). Index of surface irregularity showed a decrease from 60 +/- 12 (range: 46 to 89) to 50 +/- 9 (range: 32 to 63) at 6 months in the LASIK group whereas no significant change was noted in the PRK group. Subjective symptoms, such as glare, halos, ghost images, starbursts, and monocular diplopia, were not present postoperatively.

CONCLUSIONS

Topography-guided LASIK and PRK resulted in a significant reduction of refractive cylinder and increase of UCVA, without a significant loss of BSCVA.

Two-step LASIK With Topography-guided Ablation to Correct Astigmatism After Penetrating Keratoplasty

PURPOSE

To assess the efficacy, predictability, stability, and safety of a two-step LASIK procedure using topography-guided ablation to correct astigmatism after penetrating keratoplasty.

METHODS

Fifteen eyes of 15 patients underwent a two-step LASIK procedure at the Maggiore Hospital of Bologna, Italy. In the first step, a flap was created using the Hansatome microkeratome. In the second step, topography-guided ablation using the LaserSight LSX was planned with interactive software (CIPTA) once topographical and refractive stabilization had been obtained. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), cylindrical correction, gain of lines of BSCVA, spherical equivalent refraction, and complications were analyzed.

RESULTS

Minimum follow-up was 12 months (range: 12 to 30 months). Uncorrected visual acuity improved in all 15 (100%) eyes. At the last postoperative examination, 11 (73%) eyes had UCVA > or = 20/40. Nine (60%) eyes were within 1.0 diopter (D) of the attempted correction. Mean postoperative astigmatism was -1.67 (range: -3.5 to 0; standard deviation: 1.26). Index of success of astigmatic correction was 0.26. No patient lost Snellen lines of BSCVA. Intraoperative complications included two buttonhole flaps, and postoperative complications included one flap retraction. No further laser treatment was needed.

CONCLUSIONS

The two-step LASIK procedure using topography-guided ablation reduces spherical and cylindrical refractive error due to penetrating keratoplasty. Topography-guided ablation also proved to be effective in correcting irregular astigmatism.

Refractive surgery after corneal transplantation

PURPOSE OF REVIEW

Many patients who have undergone corneal transplantation are unable to achieve satisfactory visual acuity with spectacle and contact lens correction alone. For these patients, refractive surgery becomes a viable option to reduce the post-keratoplasty ametropia. With the many recent advances in refractive surgery for naturally occurring refractive error, new possibilities arise for application to this complicated set of patients. This review discusses key recent developments in refractive surgery after corneal transplantation.

RECENT FINDINGS

The biomechanical effects of incisional keratotomy on post-keratoplasty corneas continue to be studied, and these techniques remain a common and simple method of reducing astigmatism. Photorefractive keratectomy, previously problematic for regression and haze formation, is gaining new prominence as early experience with the adjunctive use of mitomycin C has demonstrated good results. Long-term studies with laser in-situ keratomileusis (LASIK) have continued to show good safety and efficacy. Modern developments in cataract surgery appear to have lower incidences of graft rejection and failure. Developments in lens implantation technology continue to offer expanding options for intraocular refractive surgery.

SUMMARY

Although visual rehabilitation after corneal transplantation remains a formidable challenge, developments in refractive surgery for naturally occurring ametropias directly translate into an improved ability to help these most challenging refractive cases. Continued research will bring about improved efficacy while maintaining a high level of safety.

Reliability of Orbscan II topography measurements in relation to refractive status

PURPOSE

To investigate the reliability of corneal topography measurements using the Orbscan II topography system (Bausch & Lomb) not only referring to a normal cohort but also to different refractive conditions.

SETTING

Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

METHODS

Eighty patients (mean age 46.4 +/- 19.0 years) were assigned to 4 refractive groups (Group A: emmetropia (n=20); Group B: astigmatism (n=20) (-1.98 +/- 1.77 diopters [D]); Group C: hyperopia (n=20) (+4.84 +/- 1.6 D); Group D: myopia (n=20) (-9.64 +/- 3.79 D). Three measurements were performed in a series. Thirteen defined, standardized points of the entire cornea (apex, 3.0 mm, 5.0 mm, and 7.0 mm zone) were evaluated for 3 different maps (anterior elevation, pachymetry, keratometry).

RESULTS

In all 80 patients, the following mean values were found in relation to analyzed zones: with regard to the anterior elevation map, the values decreased from 5.53 microm (center) to -6.52 microm (7.0 mm zone), the corneal thickness increased from 549.41 microm to 638.63 microm peripheral and the keratometry from 43.86 D (apex) to 45.4 D (7.0 mm zone), respectively. Analysis of the 3 different maps in all 4 refraction groups showed a tendency toward an increase in SD from the center to the 7.0 mm zone for anterior elevation and pachymetry maps. For keratometry, however, the lowest SD was found in the 7.0 mm zone. In particular, patients with hyperopia showed significant differences (P<.01), compared with emmetropic patients; the SD was higher with regard to anterior elevation as well as keratometry in peripheral zones. Group B (astigmatism) showed significantly higher SD for anterior elevation in zones 3.0, 5.0, and 7.0 mm when compared with emmetropic patients.

CONCLUSIONS

The repeated Orbscan II measurements showed SD in the micrometer range for anterior elevation and pachymetry but values between 0.48 D and 0.97 D for keratometric data. Patients with astigmatism and especially hyperopia showed significantly higher SD values in peripheral zones for anterior elevation and keratometry, indicating a lower reliability, compared with the emmetropic cohort. However, the different ages of the patients could also be a possible explanation for these findings. Therefore, the Orbscan II seems to be a predictable and useful device for measuring corneal topography.

Strategic Planning in Topography-guided Ablation of Irregular Astigmatism After Laser Refractive Surgery

PURPOSE

To identify an optimal customized ablation strategy in the treatment of eyes with secondary irregular astigmatism.

METHODS

Corneal anterior surface elevation maps of 50 eyes with secondary irregular astigmatism after decentered laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) and 50 virgin eyes were used for customized ablation simulations. Two ablation simulations with targeted postoperative surfaces perpendicular to either the visual or corneal morphological axis were made for each eye. All ablations were programmed for correction of corneal irregularities, including corneal astigmatism. The manifest refractive error was not corrected. Optical diameter was 6.5 mm and total diameter was 7.5 mm. Maximum ablation depths and maximum transition zone gradients were registered and analyzed.

RESULTS

In eyes with secondary irregular astigmatism, mean maximum ablation depth was 48.21 +/- 25.96 microm and 26.31+/- 14.08 microm, whereas mean maximum transition zone gradient was 29.07 +/- 25.15 microm and 9.88 +/- 6.41 microm in ablation simulations based on the visual and corneal morphological axes, respectively. The difference between the ablation strategies was highly statistically significant for both parameters (P < .001). In virgin eyes, only a minor difference was noted between the visual and corneal morphological axis ablation simulations (P = .15 for maximum ablation depths and P=.19 for maximum transition zone gradient).

CONCLUSIONS

In secondary irregular astigmatism, ablation based on the corneal morphological axis appears to minimize corneal tissue consumption and allows a smoother transition zone.

Standardized arcuate keratotomy for postkeratoplasty astigmatism

PURPOSE

To assess the effect of standardized, paired arcuate keratotomy (AK) on the change in astigmatism in postkeratoplasty eyes.

SETTING

Moorfields Eye Hospital, London, United Kingdom.

METHODS

A retrospective review was conducted of 20 eyes of 19 patients having the same AK procedure regardless of the magnitude of the preoperative astigmatism. Each eye had a pair of 60-degree arc length incisions placed in the corneal stroma. The incisions were 600 mum deep and 6.0 mm apart. The preoperative and postoperative refractions and complications were analyzed. Astigmatic change was analyzed without regard to axis, as surgically induced refractive change, and using a modified polar plot of change in astigmatism.

RESULTS

The mean cylinder was reduced from -10.99 diopters (D) +/- 4.26 (SD) to -3.33 +/- 2.18 D. There was no significant change in the mean spherical equivalent. There was a strong correlation between the magnitude of the preoperative cylinder and the magnitude of the change in astigmatism (R2 = 0.76). In 3 eyes, the surgically induced axis of astigmatism was more than 15 degrees from that expected.

CONCLUSIONS

In postkeratoplasty eyes, the change in the magnitude of astigmatism induced by standardized AK was proportional to the preoperative magnitude of astigmatism. Arcuate nomograms for congenital astigmatism have no role in the management of astigmatism in postkeratoplasty eyes.

Orbscan computerized topography: Attributes, applications, and limitations

An extensive electronic search was undertaken in January 2004 to identify all relevant peer-reviewed publications on Orbscan slit-scanning/Placido computerized topography. Ninety-one publications were identified. These address elevation topography and best-fit sphere, accuracy and repeatability of anterior and posterior corneal elevation and keratometric maps, comparison of Orbscan-acquired data and Placido-based computerized videokeratography instruments, pachymetry measurement and correlation with ultrasound, screening eye-bank corneas, detection of keratoconus, identifying corneal ectasia after refractive surgery, and miscellaneous applications. Studies were analyzed and critically compared in relation to attributes, applications, and limitations of Orbscan corneal topography. The review highlights advantages of this technique in assessing the cornea in health and disease and after surgery and identifies specific aspects that require further investigation and clarification.

Treatment of irregular astigmatism with a 213 nm solid-state, diode-pumped neodymium:YAG ablative laser

PURPOSE

To present the outcome of photorefractive keratectomy (PRK) using a new neodymium:YAG (Nd:YAG) laser in patients with irregular astigmatism.

SETTING

Claremont Eye Clinic, Claremont, and the University of Western Australia, Perth, Australia.

METHODS

In 3 patients with irregular astigmatism, PRK was performed with a solid-state, 213 nm wavelength, 300 Hz scanning-spot, diode-pumped Nd:YAG ablative laser (CustomVis Pulzar laser system). The 3 patients had had previous PRK with penetrating keratoplasty, astigmatic keratotomy, or limbal relaxing incisions. At 3 and 6 months, best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), manifest refraction, contrast sensitivity, and corneal topography were measured.

RESULTS

The first patient had a 1-line improvement in BSCVA and a 4-line improvement in UCVA, a 3.00 diopter (D) decrease in keratometric cylinder, and improvement in contrast sensitivity. The second patient had a 7.00 D decrease in myopia in 1 meridian and a 4.25 D decrease in the refractive cylinder in the other meridian. The third patient had a 2-line improvement in BSCVA, a 5-line improvement in UCVA, a 2.00 D decrease in the refractive cylinder, and improvement in contrast sensitivity.

CONCLUSION

The laser's combination of a small spot, a fast pulse rate, and ultrafast tracking/scanning resulted in good results in 3 patients with difficult irregular astigmatism.

Topographically supported customized ablation for the management of decentered laser in situ keratomileusis

PURPOSE

To evaluate the efficacy, predictability, and safety of topographically supported customized ablations (TOSCAs) for decentered ablations following laser in situ keratomileusis (LASIK).

DESIGN

Prospective nonrandomized clinical trial.

METHODS

Nine patients (11 eyes) with LASIK-induced decentered ablations underwent TOSCA following flap lifting. Topographically supported customized ablation was performed using a corneal topographer to obtain a customized ablation profile, combined with a flying spot laser.

RESULTS

Mean follow-up was 9.22 +/- 2.82 months (range 6-12 months). No intra- or postoperative complications were observed. Manifest refraction (spherical equivalent) did not change significantly (pre-TOSCA: -0.14 +/- 1.58 diopters [range, -1.75 to +3.00 diopters] to +0.46 +/- 1.02 diopters [range, -1.00 to +1.75 diopters]; P =.76), whereas there was a statistically significant reduction in the refractive astigmatism (pre-TOSCA: -1.55 +/- 0.60 diopters [range, -3.00 to -0.75 diopters] to -0.70 +/- 0.56 diopters [range, -2.00 to -0.25 diopters]; P =.003). Mean uncorrected visual acuity improved significantly (P <.001) from 0.45 +/- 0.16 (range, 0.2-0.7) to 0.76 +/- 0.29 (range, 0.2-1.2) at last follow-up. Mean best-corrected visual acuity improved from 0.74 +/- 0.22 (range, 0.4-1.0) to 0.95 +/- 0.20 (range, 0.6-1.2; P =.002). Eccentricity showed a statistically significant reduction after TOSCA treatment (pre-TOSCA: 1.59 +/- 0.46 mm [range, 0.88-2.23 mm]; post-TOSCA: 0.29 +/- 0.09 mm [range, 0.18-0.44 mm]; P <.001).

CONCLUSION

In our small sample, enhancement LASIK procedures with TOSCA appear to improve uncorrected and best-corrected visual acuity as well as eccentricity in patients with LASIK-induced decentered ablation.

Conductive Keratoplasty to Correct Hyperopic Astigmatism

PURPOSE

To evaluate the efficacy of conductive keratoplasty in the treatment of pre-existing and surgically induced hyperopic astigmatism.

METHODS

In this prospective, noncomparative case series, four eyes of four subjects, two female and two male (age 25 to 47 yr) were treated for hyperopia (up to +5.50 D) and hyperopic astigmatism (up to +5.75 D) with the Refractec ViewPoint conductive keratoplasty system. The follow-up period was 6 months. Uncorrected and spectacle-corrected visual acuity, manifest and cycloplegic refraction, and videokeratographs were obtained before and after surgery. We treated two patients who had already had LASIK, one of them with a decentered ablation and the other with flap striae, one patient after PRK, and one patient with keratoconus.

RESULTS

No complications were observed. No eye lost lines of spectacle-corrected visual acuity. All eyes showed improvement of uncorrected visual acuity of 3 or more lines. Videokeratographs demonstrated improved centration and reduction in keratometric power readings. Each eye was analyzed separately, including a comparative analysis of the proposed nomograms and quality of vision after surgery.

CONCLUSIONS

Conductive keratoplasty may be a minimally invasive solution for patients with irregular hyperopic astigmatism, offering improved quality of vision in instances of flap striae by tightening the central cornea.

Phototherapeutic keratectomy: 12 years of experience

BACKGROUND

Phototherapeutic keratectomy (PTK) has been employed as a surgical tool to treat corneal disease for more than 10 years. The laser has made it possible to remove superficial corneal opacities and thereby restore vision. The 193 nm ultraviolet light separates molecules and splits molecules in biological tissue, thereby ablating it. About 0.25 microm of tissue is ablated by each pulse. The development of the excimer laser technique has been fast. It has principally focused on refractive surgery but has also benefited PTK.

CORNEAL DYSTROPHIES

The ability to delay or postpone corneal grafting in superficial corneal dystrophies represents a very important achievement. Map-dot-fingerprint dystrophy or basal membrane dystrophy is a common indication for PTK. Other dystrophies such as Meesman's, Reis-Bückler's, Thiel-Benke's, granular, macular, lattice and Schnyder's can be treated, although with differing degrees of success and varying rates of recurrence. Subepithelial scarring in Fuchs' dystrophy has been ablated. Other trials have involved the removal of substantial parts of the stroma in order to reduce the load on the endothelium. Recurrent dystrophic changes can likewise be removed from corneal grafts and thus prevent the need for regrafting.

RECURRENT EROSIONS

Laser treatment has made it possible to manage wound-healing problems better after recurrent erosions. Recurrent erosions are the most common indications for PTK: several studies show good and persistent effects with this type of treatment. Persistent epithelial defects of various origins, among them corneal ulcers resulting from allergic disease, can likewise be treated.

SCAR TISSUE

Scars after surgery such as pterygeum excision can be removed. Smooth muscle actin containing fibroblasts in old scars should be given special consideration in PTK. Excimer laser surgery can be successfully combined with conventional surgery to remove excessive scar tissue, Salzmann's nodules and very flaky and coarse band keratopathy. Irregular corneal surfaces following ulcers and injuries pose problems that have so far proved difficult to overcome. Thinning is often seen after bacterial corneal ulcers or after herpes simplex keratitis. A rough or uneven surface can be made smoother by using modulators during treatment by casting a new surface under a hard contact lens (PALM technique), a surface that is then projected into the stroma by laser ablation. Modern techniques linking the excimer laser with computerized corneal topography and wavefront analysis promise to further improve the smoothing capacities of lasers and to increase the quality of optical results.

COMPLICATIONS

The most feared complication of PTK is the postoperative infection. These are rare. Haze is usually not prominent but scar tissue formation of a more persistent type has been noted after laser surgery in eyes with pre-existing surgical scars. Keratectasia has been described after PTK. Failure due to deep opacities or a surface that is too uneven is a more common frustration. This paper reviews advances in excimer laser treatment of corneal disease.

Customized corneal ablation

Refractive surgery is still one of the most innovative and evolving fields in ophthalmology. With the advent of customized ablation, a change in paradigm has been established: the primary goal of refractive surgery is not only to eliminate spectacles but to improve or at least prevent deterioration of the optical performance of the eye. Wavefront-guided refractive surgery has, as a new goal, to correct or at least minimize all optical aberrations of the eye, and consequently to improve or preserve visual performance, especially under scotopic conditions.