Laser in situ Keratomileusis for Correction of High Astigmatism After Penetrating Keratoplasty

Laser in situ keratomileusis versus Artisan lens implantation in correcting ametropia after penetrating keratoplasty for keratoconus

PURPOSE

To compare the long-term safety and efficacy of laser in situ keratomileusis (LASIK) with Artisan phakic intraocular lens implantation to correct refractive errors after penetrating keratoplasty (PK) for keratoconus.

METHODS

This retrospective comparative interventional case series included a total of 33 consecutive keratoconus eyes that had previous PK and received subsequent LASIK (n = 16) or Artisan lens implantation (n = 17) were included in this study. Outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive error, and complications.

RESULTS

Postoperatively, the UDVA of ≥20/40 was achieved in none of the LASIK group compared to 62.5% of eyes in the Artisan group (P < 0.001); the respective values for CDVA of ≥20/40 were 87.5 and 94.1% (P = 0.51). Spherical equivalent refraction decreased from - 6.97 ± 1.50 D preoperatively to - 4.20 ± 2.05 D postoperatively in the LASIK group (P < 0.001) and from - 10.79 ± 2.15 D preoperatively to - 2.13 ± 1.23 D postoperatively in the Artisan group (P < 0.001). There was no significant change in the refractive astigmatism in LASIK group (P = 0.30) or Artisan group (P = 0.11). The efficacy and safety indices were significantly better for Artisan (0.82 ± 0.34 and 1.13 ± 0.30, respectively) than for LASIK (0.22 ± 0.17 and 0.85 ± 0.24, respectively, P ≤ 0.006 for both comparisons). While refractive error changed significantly from postoperative year 3 to the final visit in the LASIK group, it remained stable in the Artisan group through follow-up period. No significant complications were observed in any group.

CONCLUSION

Artisan lens implantation provided superior and stable visual outcomes compared to LASIK for the management of post PK refractive errors in keratoconus eyes.

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.

Correction of postkeratoplastic astigmatism by intrastromal corneal segments implantation using a femtosecond laser

Background. After penetrating keratoplasty, mild to high induced corneal astigmatism was observed in each case. The existing choice of correction of postkeratoplastic astigmatism is aimed at fi nding an individual approach in order to compensate for it and not weaken the biomechanical properties of the corneal graft.The aim: to analyze the clinical, functional, and morphological results of postkeratoplastic astigmatism correction by implantation of intrastromal corneal segments using a femtosecond laser.Methods. 22 patients were examined before and 1 year after surgery. The operation was performed under local anesthesia: stage I – an intrastromal tunnel was formed using a femtosecond laser “Femto Visum” 1 MHz (Optosystems, Russia); stage II – the intrastromal corneal segments were implanted. The results were assessed using standard and special research methods using optical coherence tomography Visante OCT (Zeiss, Germany), keratotopography (Tomey-5, Japan), optical corneal analyzer ORA (Reichert, USA), laser tindalemetry FC-2000 (Kowa, Japan) and confocal microscope Confoscan-4 (Nidek, Japan).Results. Before the operation, uncorrected visual acuity averaged 0.09 ± 0.05, after a year – 0.50 ± 0.16; best corrected visual acuity – 0.30 ± 0.12 and 0.60 ± 0.05 respectively; cylindrical component of refraction – –10.29 ± 3.12 and –2.20 ± 0.64 D respectively; mean keratometry value – 43.59 ± 2.14 and 38.56 ± 1.75 D respectively; corneal hysteresis – 7.92 ± 1.22 and 8.95 ± 1.05 mm Hg respectively; corneal resistance factor – 7.01 ± 1.81 and 8.44 ± 1.44 mm Hg respectively; protein fl ux in the moisture of the anterior chamber – 2.97 ± 0.28 and 3.04 ± 0.24 f/ms respectively; endothelial cell density – 1521 ± 327 and 1475 ± 419 cells/mm2 respectively.Conclusion. Intrastromal corneal segments implantation into a corneal graft using a femtosecond laser has efficiency and safety method in correcting postkeratoplastic astigmatism.

Post-penetrating keratoplasty astigmatism

Postoperative astigmatism is one of the common complications affecting visual outcomes after a penetrating keratoplasty. It can result from various factors related to host, donor and surgical technique, resulting in suboptimal visual outcome. While some of the measures taken during preoperative planning and during actual surgery can reduce the magnitude of postoperative astigmatism, postoperative correction of astigmatism is often required in cases with high degrees of astigmatism. When spectacles and contact lenses fail to provide optimal visual outcomes, various surgical techniques that include astigmatic keratotomy, compression sutures, toric intraocular lens placement, and laser refractive procedures can be considered. When none of these techniques are able to achieve a desired result with in the acceptable optical range, a repeat keratoplasty is considered a last option. We discuss the various causes and management of complication of postoperative astigmatism occurring after a full thickness corneal transplantation surgery.

Femtosecond Laser-Assisted In Situ Keratomileusis Treatment of Residual Refractive Error following Femtosecond Laser-Enabled Keratoplasty

Purpose

To evaluate the safety and effectiveness of femtosecond laser-assisted in situ keratomileusis (LASIK) in the treatment of residual myopia and astigmatism following femtosecond laser-enabled keratoplasty (FLEK).

Design

Retrospective case review.

Methods

Chart review of all patients with prior FLEK who subsequently underwent femto-LASIK surgery after full suture removal was performed at the Gavin Herbert Eye Institute at the University of California, Irvine. A total of 14 eyes in 13 patients met this criterion, and their comprehensive examinations performed at standard intervals were reviewed. Main outcome measures include uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) expressed as the logarithm of the minimum angle of resolution (logMAR), manifest refractive astigmatism, and spherical equivalent.

Results

From the preoperative visit to the 3 month visit, all 14 eyes significantly improved in UDVA (logMAR, 0.93 ± 0.23 to 0.44 ± 0.32, P = 0.002) with no loss of CDVA (logMAR, 0.26 ± 0.19 to 0.18 ± 0.23, P = 0.50). All 14 eyes showed significant improvement in manifest refractive astigmatism (4.71 ± 1.77 to 2.18 ± 1.45 diopters (D), P = 0.003) and spherical equivalent (−2.57 ± 2.45 to −0.48 ± 0.83 D, P = 0.0007). There were no flap or graft complications as a result of femto-LASIK.

Conclusions

Our findings suggest that femto-LASIK on eyes with prior FLEK is safe and effective in improving visual acuity and reducing residual astigmatism.

Graft-size selection and anisometropia reduction in penetrating keratoplasty (PKP)

PURPOSE

To compare the amount of myopia induced by same-size donor-to-host penetrating keratoplasty with that of the amount of myopia induced by over-sized donor-to-host penetrating keratoplasty.

SETTING

Tertiary referral academic center.

DESIGN

Retrospective cohort study.

METHODS

Charts from patients who underwent penetrating keratoplasty by the same technique at Bascom Palmer Eye Institute between Nov 1, 2002, and January 1, 2006, were reviewed. The patients underwent optical penetrating keratoplasty using 12 interrupted 10-0 nylon sutures and a 12-bite continuous 10-0 nylon suture by a single surgeon (R.K.F.). The surgical technique used would be considered standard of care at most institutions. The Institutional Review Board, University of Miami Human Subjects Research Office, approved the study protocol. The donor graft was over-sized by 0.25mm in eyes when the intended final refractive target was greater than -1.00 diopters spherical equivalent (SE). The same-size donor graft was used when the intended final refractive target was less than -1.00 diopters SE. The selection of donor graft size was entirely based upon clinical parameters, meaning that the intended final refractive target was determined per each patient's fellow eye refraction, with the intention of reducing anisometropia. All patients received postoperative refraction and corneal topography. These measurements were performed at 6-8 weeks when the initial removal of sutures commenced, then at 6 months, then after completion of selective suture removal, then again at 12 months.

RESULTS

At 12 months, the over-sized group resulted in -1.35 diopters (SD = 2.25) SE of refraction, and the same-size group resulted in -0.14 diopters (SD = 2.42) SE. This approached statistical significance (p = 0.052) in comparison to -1.00 diopters spherical equivalent.

CONCLUSIONS

Using a donor graft that is over-sized by 0.25mm results in refraction of -1.00 diopters SE or more of myopia. Using a same-size donor-graft results in refraction of less than -1.00 diopters SE. Therefore, careful graft-size selection can result in a more favorable clinical outcome-namely, reduction in anisometropia-in patients undergoing penetrating keratoplasty.

Visual outcomes of Femto-LASIK for correction of residual refractive error after corneal graft

PURPOSE

To evaluate the outcomes of the Femto-LASIK method in the treatment of refractive errors following penetrating keratoplasty (PK) at the Persian Eye Clinic, Isfahan, Iran

METHODS

In a prospective, non-comparative case series, 34 consecutive symptomatic eyes of 34 patients after corneal graft, were operated on. Tissue-saving (TS) Femto-LASIK (n = 16), and Zyoptix Personalized Treatment Advanced (PTA) Femto-LASIK (n = 18) were performed using the Bausch & Lomb Technolas 217z excimer laser and Zyoptic algorithm. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), manifest refraction, contrast sensitivity, and HOAs were evaluated preoperatively and 12 months after enhancement treatment.

RESULTS

At 12 months, the mean preoperative myopic spherical equivalent refraction (SE) decreased from -6.50 ± 2.8 D to -1.6 ± 1.8 D, and mean hyperopic SE from +3.2 ± 2.20 D to 0.37 ± 1.2 D. The safety index was 1.42 (1.2 in the TS group and 1.5 in the PTA group). In the TS group, 100% of eyes achieved 20/80 or better UCVA and 50%, 20/40 or better and in the PTA group, 100% of eyes achieved 20/80 or better UCVA and 77.7%, 20/40 or better. The efficacy index was 1.08 (0.9 in TS group and 1.21 in the PTA group). Patients obtained statistically significant lower values of root mean square (RMS) of HOAs with spherical aberrations (p < 0.05).

CONCLUSIONS

Femto-LASIK method with Zyoptic programs after PK was safe, effective, and predictable for correction of spherical and cylindrical components of the refractive error.

Photorefractive keratectomy with mitomycin C after penetrating and lamellar keratoplasty

PURPOSE

To assess the safety and efficacy of photorefractive keratectomy with mitomycin C (PRK-MMC) to correct refractive errors after corneal transplantation.

METHODS

This was a prospective and noncomparative study of 36 eyes that underwent PRK-MMC after penetrating (n = 34) or lamellar (n = 2) keratoplasty. After mechanical epithelial removal and photoablation, a sponge with mitomycin C 0.02% was applied to the stromal bed for 1 minute. The uncorrected and best-corrected visual acuities, refraction, and complications were assessed.

RESULTS

The average follow-up was 16.27 ± 8.38 months (range, 6-30.5 months). The spherical equivalent decreased from -3.95 ± 4.11 to -1.07 ± 1.45 diopters (D) postoperatively (P < 0.001). The mean preoperative astigmatism was 4.42 ± 1.69 D (range, 1.00-7.25 D); however, surgical correction was limited to 6.00 D. Vector analysis of astigmatic correction showed an index of success of 55%. At the last follow-up, 41.7% (n = 15) and 61.1% (n = 22) of the eyes were within ±0.50 and ±1.00 D of emmetropia, respectively. Nineteen eyes (52.8%) achieved an uncorrected visual acuity of 20/40 or better. The best-corrected visual acuity remained within 1 line of the preoperative values in 26 cases (72.2%), improved in 8 (22.2%), and decreased in 2 (5.6%). Endothelial cell decompensation was observed in 1 eye (2.8%) 11 months postoperatively, and haze developed in 3 cases (8.3%).

CONCLUSIONS

PRK-MMC may be an option to correct refractive errors after keratoplasty. A low preoperative endothelial cell count and haze may affect the safety outcomes.

Femtosecond LASIK combined with astigmatic keratotomy for the correction of refractive errors after penetrating keratoplasty

BACKGROUND AND OBJECTIVE

To evaluate the outcomes of femtosecond laser in situ keratomileusis (LASIK) compared to combined LASIK and astigmatic keratotomy in the treatment of refractive errors following penetrating keratoplasty.

PATIENTS AND METHODS

A retrospective review was performed on 18 eyes of 16 patients who underwent LASIK for visual rehabilitation after penetrating keratoplasty. Seven eyes (38.8%) had undergone paired relaxing incisions with topographic guidance prior to LASIK performance.

RESULTS

Preoperative uncorrected visual acuity was 20/100 or worse in 13 eyes (72.2%) and best-corrected visual acuity (BCVA) was 20/40 or better in 15 eyes (83.3%). After LASIK, uncorrected visual acuity was 20/40 or better in 10 eyes (55.5%) and BCVA was 20/40 or better in 17 eyes (94.4%). Three eyes (16.6%) had a loss of 1 to 2 lines of BCVA. No difference in visual outcomes was noted in eyes undergoing LASIK and astigmatic keratotomy versus LASIK alone. An increased complication rate was noted in patients who also underwent astigmatic keratotomy and was associated with flap creation.

CONCLUSION

Femtosecond LASIK is effective in reducing ametropia after penetrating keratoplasty. Astigmatic keratotomy might complicate flap creation in LASIK; therefore, photorefractive keratectomy should be considered for patients who had previous astigmatic keratotomy to reduce astigmatism.

Femtosecond thin-flap LASIK for the correction of ametropia after penetrating keratoplasty

PURPOSE

To evaluate the outcomes of LASIK with thin femtosecond laser flaps for the treatment of refractive errors after penetrating keratoplasty (PK).

METHODS

Eleven consecutive eyes underwent femtosecond thin-flap LASIK 51.6+/-42.1 months (range: 13 to 156 months) after the initial PK. A full ophthalmic assessment was performed before femtosecond LASIK and 6 months after surgery. Postoperative retreatments were also noted.

RESULTS

No intra- or postoperative complications were observed. The outcomes of nine eyes that completed at least 6 months' follow-up and had no retreatment during that period were evaluated. Mean preoperative myopia decreased from -3.60+/-1.60 diopters (D) to +1.00+/-2.70 D 6 months after surgery, and mean hyperopia decreased from +3.50+/-1.30 D preoperatively to +0.30+/-0.70 D 6 months after surgery. Mean preoperative astigmatism decreased from -6.60+/-3.60 D to -2.90+/-2.00 D 6 months after surgery. At 6 months, the mean preoperative myopic spherical equivalent refraction (SE) decreased from -6.40+/-2.00 D to -0.02+/-2.20 D, and mean hyperopic SE from +0.80+/-2.80 D to -0.60+/-0.60 D. At 6 months postoperatively, 67% (6/9) of eyes were within 1 line of preoperative best spectacle-corrected visual acuity and 33% (3/9) gained > or =2 lines.

CONCLUSIONS

Femtosecond thin-flap LASIK is a safe procedure in eyes with previous PK. This procedure is reasonably predictable, especially for the spherical component of the refraction. Creating the flap with the femtosecond laser and performing excimer laser ablation within the corneal graft limits without involving the graft-host junction provides the advantage of performing the entire procedure in one step.

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.

[LASIK treatment for graft astigmatism]

OBJECTIVE

To analyze the advantages of LASIK as a treatment for postkeratoplasty residual astigmatism.

PATIENTS

and

METHOD

Retrospective, noncomparative, monocentric study on 14 patients with penetrative keratoplasty. Visual acuity, objective refraction, intraocular pressure, slit lamp biomicroscopy, videotopography, pachymetry, and patient satisfaction were studied before and after surgery.

RESULTS

Refraction was stable 6 months after treatment in 93% (13/14) of the patients. The mean uncorrected visual acuity increased from 0.16 to 0.4. Two out of four patients (14.3%) were retreated because visual acuity did not improve after the first treatment; 35% did not need any optical correction after the intervention. The measured astigmatism showed a significant decrease, from 65% greater than 5 D before treatment to 82% under 2 D after treatment. Only two out of 14 patients (14.3%) were not satisfied. No intraocular or postoperative complications were reported in this study.

CONCLUSION

LASIK seems to be an interesting option in the treatment of postkeratoplasty residual astigmatism. This study has shown its efficacy and safety in this indication. Its originality lies in the one-step procedure, with the flap and photoablation done in a single step. However, it is still dependent on the operator and most particularly the equipment (laser, microkeratome, aberrometry).

Flap-induced Refraction Change in LASIK After Penetrating Keratoplasty

PURPOSE

To further analyze the refractive and topographic changes occurring with microkeratome lamellar keratotomy and to investigate possible factors associated in eyes with previous penetrating keratoplasty (PK).

METHODS

The Hansatome microkeratome was used to create a lamellar corneal flap in 21 eyes of 19 patients after PK. The laser ablation was not performed in the first stage. Pre- and postoperative refractions and corneal topographies were compared to evaluate possible changes induced by the keratotomy.

RESULTS

Twenty-one eyes were analyzed in this study. Mean time between PK and lamellar keratotomy was 36.63 +/- 28.23 months (range: 12 to 120 months). No microkeratome-related flap complications occurred. Previous to the keratotomy, the mean spherical equivalent refraction was -4.26 +/- 3.41 diopters (D), mean refractive astigmatism was -4.71 +/- 2.27 D, and mean topographic astigmatism was 5.28 +/- 2.94 D. After keratotomy, eyes showed statistically significant changes in spherical equivalent refraction from preoperative values (P = .025), with 3 eyes showing changes > 2.00 D. Average refractive and topographic astigmatism did not change significantly from before to after keratotomy. However, surgically induced astigmatism (SIA) calculated through vector analysis was > 1.01 in 11 (52.4%) eyes. A statistically significant correlation was found between the SIA values and preoperative refractive astigmatism (P = .025).

CONCLUSIONS

Lamellar keratotomy as part of two-stage LASIK in eyes with prior PK led to refractive changes that justify the use of this technique, especially in eyes with high degrees of preoperative astigmatism.

Astigmatism and the Impact of Relaxing Incisions After Penetrating Keratoplasty

PURPOSE

To determine the impact of relaxing incisions for correcting postoperative astigmatism following penetrating keratoplasty.

METHODS

Data were collected through the Swedish Corneal Transplant Register. Of the 1161 grafts with complete 2-year follow-up, 131 underwent relaxing incisions. Stepwise multiple regression was used to determine the factors that influenced the extent of astigmatism in diopters (D) (square root transformed). The change in astigmatism brought about by relaxing incisions was evaluated both by subtraction (ie, ignoring angle) and vector analysis.

RESULTS

The overall mean astigmatism was 4.56 D (95% confidence interval [CI]: 4.40-4.73, n = 1161). The final regression model explained only a small proportion of the overall variability of the data (< 5%). There was a slight increase in postoperative astigmatism with recipient age (P = .025), and two of the seven participating clinics achieved lower levels of astigmatism (P = .001 and P = .036, respectively). In patients who underwent relaxing incisions, astigmatism was reduced from 8.40 D (95% CI: 8.0-9.0, n = 131) to 3.80 D (95% CI: 3.5-4.3). The mean difference by subtraction was 4.50 D (95% CI: 4.0-5.0, P < .001, paired t test). Vector analysis showed the overall reduction of astigmatism due to surgery to be 7.90 D (95% CI: 7.2-8.7). Compared with grafts with no refractive surgery, a trend was noted that suggested corrected visual acuity was improved following relaxing incisions.

CONCLUSIONS

Relaxing incisions were found to be a safe and effective method for reducing postoperative astigmatism and may improve visual acuity.

Efficacy of nonsimultaneous bilateral LASIK after nonsimultaneous bilateral penetrating keratoplasty

PURPOSE

To show if nonsimultaneous bilateral laser in situ keratomileusis (LASIK) is a safe and effective procedure for patients with bilateral penetrating keratoplasty (PKP).

METHODS

Five patients (10 eyes), with keratoconus, underwent PKP separately in each eye. After an average PKP follow-up of 45.8 months per eye, (range, 19-92 months), each eye underwent 1-stage LASIK using the Visx Star S3 laser to correct its residual refractive error. We used the cycloplegic refraction as the target for the LASIK surgery. Each patient had his or her eyes done separately 3 weeks apart.

RESULTS

Pre-LASIK myopia averaged -3.93 +/- 2.9 D, ranging from -10.00 to +0.75 D. Pre-LASIK astigmatism averaged -3.25 +/- 0.80 D, ranging from -1.75 to -4.50 D. Mean pre-LASIK keratometry was 45.4 +/- 2.6, ranging from 42.2 to 50.5. Uncorrected visual acuity pre-LASIK averaged 20/220, ranging from 20/60 to 20/400. Best-corrected spectacle visual acuity (BCSVA) pre-LASIK averaged 20/22, ranging from 20/20 to 20/30. Nine eyes had no complications. One eye had a flap buttonhole during LASIK, and surgery was aborted. No vision was lost in this eye. Mean follow-up after LASIK in the 9 eyes was 17 +/- 15.2 months, (range, 4-56 months). Mean post-LASIK ametropia in these 9 eyes was +0.25 +/- 0.45 D, ranging from -0.50 to +0.75 D. Average post-LASIK astigmatism was -0.33 +/- 0.38 D, ranging from 0 to -0.75 D. In the 9 treated eyes, uncorrected vision post-LASIK averaged 20/25, ranging from 20/20 to 20/30. BCSVA post-LASIK averaged 20/21, ranging from 20/20 to 20/25. No lines of visual acuity were lost in any of the eyes.

CONCLUSION

Young patients who have had bilateral PKP, with good postoperative vision and low levels of myopia, astigmatism, and minimal wound override, are good candidates for bilateral nonsimultaneous LASIK. Further studies can now be done on the performance of bilateral simultaneous LASIK in patients who have had corneal transplant surgery in both of their eyes.

Three-Year Follow-up Analysis of Artisan Toric Lens Implantation for Correction of Postkeratoplasty Ametropia in Phakic and Pseudophakic Eyes

PURPOSE

To determine the 3-year follow-up of efficacy and safety of Artisan toric iris-fixated lens implantation after penetrating keratoplasty (PK) to correct high ametropia and astigmatism.

DESIGN

Prospective noncomparative case series with a minimum follow-up of 1 year.

PARTICIPANTS

Artisan toric lens implantation was performed in 36 eyes of 35 patients who were contact lens intolerant or unable to wear glasses due to anisometropia and/or high astigmatism.

INTERVENTION

Thirty-six eyes of 35 consecutive patients received Artisan toric lens implantation for postkeratoplasty astigmatism and/or anisometropia.

MAIN OUTCOME MEASURES

Manifest refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and corneal topography were determined or performed before surgery and at 3, 6, and 12 months and yearly intervals up to 4 years after surgery. Efficacy, safety, percent reduction of refractive astigmatism, anisometropia of defocus, and the astigmatism correction index were determined. A patient satisfaction questionnaire and specular microscopy were assessed.

RESULTS

The mean +/- standard deviation of preoperative refractive cylinder was -7.06+/-2.01 diopters (D) (range, -3.0 to -11.0), which was reduced to -1.73+/-1.25 D, -1.69+/-1.15 D, -1.94+/-1.68 D, -2.02+/-1.93 D, and -2.00+/-1.53 D at 6 months (n = 36), 1 year (n = 36), 2 years (n = 29), 3 years (n = 15), and the last follow-up examination (28.5+/-12.5 months, n = 36), respectively (P<0.001 for all time points, paired t test). The spherical equivalent was reduced from -3.19+/-4.31 D (range, +5.5 to -14.25 D) preoperatively to -1.03+/-1.20 D (range, +1.0 to -5.25 D) at the last follow-up. The UCVA and BSCVA were > or =20/40 in 31.6% and 80.6%, respectively. There was a loss of BSCVA of >2 lines in 8.3% of eyes and a gain of at least 2 lines in 8.3% of eyes. Percent reductions in refractive astigmatism and anisometropia of defocus were 88.8%+/-29.5% and 77.8%+/-19.3%, respectively. The astigmatism correction index was 96.0%+/-24.2%. Satisfaction increased from 3.6 to 8.0 (scale, 0-10) after implantation. The endothelial cell loss as compared with preoperatively was 13.8%+/-18.7% (n = 34), 21.2%+/-21.8% (n = 33), 29.6%+/-27.3% (n = 26), 30.4%+/-32.0% (n = 18), and 34.8%+/-26.3% (n = 6) at 6 months (P = 0.001), 1 year (P<0.001), 2 years (P<0.001), 3 years (P = 0.001), and 4 years postoperatively (P = 0.1), respectively. In 2 patients, irreversible graft rejections occurred, and in 1 patient, gradual endothelial decompensation occurred.

CONCLUSION

Artisan toric lens implantation after PK was effective for reduction of refractive astigmatism and ametropia. All patients were suitable for spectacle correction after implantation. There was continuing endothelial cell loss from 6 months to 3 years postoperatively. In 3 cases, corneal graft failure developed.

Correction of post-keratoplasty astigmatism with keratotomies in the host cornea

We evaluated the effects of astigmatic keratotomy performed in the host cornea to treat astigmatism after penetrating keratoplasty. In 11 patients with high post-keratoplasty astigmatisms (mean 9.02 diopters [D]; range 5.5 to 17.4 D), an arcuate keratotomy was performed in the host cornea. The mean incision depth was 575 mum (range 500 to 600 mum). The refractive data were analyzed using the Alpins method for vector analysis. The mean keratometric cylinder decreased to 3.41 D (range 0.9 to 5.3 D). The mean surgically induced astigmatism achieved was 7.3 +/- 3.89, with a mean correction index of 0.82 +/- 0.34. No microperforations were observed, and neither graft decompensation nor rejection occurred. Astigmatic keratotomy performed in the host cornea was a safe procedure to reduce post-keratoplasty astigmatism. The procedure offers the potential for correction of the astigmatism and has satisfactory predictability.

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.

Laser in situ keratomileusis outcomes following radial keratotomy, astigmatic keratotomy, photorefractive keratectomy, and penetrating keratoplasty

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) to enhance refractive status following other corneal surgical procedures.

SETTING

Clinical office-based practice.

METHODS

Seventy-one eyes of 57 patients had LASIK for refractive errors following radial keratotomy (n = 22), astigmatic keratotomy (n = 13), photorefractive keratectomy (n = 18), and penetrating keratoplasty (n = 18). A Moria LSK-1 microkeratome was used with a Visx S2 or Wavelight Allegretto excimer laser. Data were acquired by retrospective chart review of all appropriately qualified patients.

RESULTS

The mean preoperative manifest refractive spherical equivalent (MRSE) was -3.93 diopters (D) +/- 2.83 (SD) in myopic eyes and +1.43 +/- 1.79 D in hyperopic eyes. The mean time from the initial corneal surgical procedure to LASIK was 65.0 months. The mean post-LASIK follow-up was 9.40 months (range 1 to 42 months). Postoperatively, the mean MRSE was -0.85 +/- 1.42 D in myopic eyes (P<.0001) and -0.16 +/- 1.09 D in hyperopic eyes (P<.0001). Enhancement by LASIK was required in 14% of eyes.

CONCLUSION

In eyes that have had a variety of previous corneal surgeries, LASIK offers a safe and predictable method for enhancing refractive results.

Post-LASIK corneal flap displacement following penetrating keratoplasty for bullous keratopathy

OBJECTIVE

To report 3 patients who experienced late flap dislocation after laser in situ keratomileusis (LASIK) in eyes that had undergone prior penetrating keratoplasty (PKP) for bullous keratopathy.

METHODS

Retrospective chart review of 2 referral corneal and refractive surgery practices, case reports, and literature review.

RESULTS

Three patients (mean age 58.3 years, 2 male, 1 female), all status post-corneal transplant for bullous keratopathy, had residual myopic astigmatism and underwent LASIK for correction of their significant anisometropia. Flap dislocation occurred at a mean of 7 days (range 3 to 14 days) following the LASIK procedure. All patients had peripheral corneal edema in their recipient bed. All 3 patients required an additional surgical procedure for visual rehabilitation.

CONCLUSION

Flap displacement may occur following LASIK in patients who have undergone PKP for bullous keratopathy. The endothelial pump function, which is vital to maintaining flap adherence, may be compromised in these patients. We suggest that patients with a history of PKP and endothelial compromise who undergo LASIK wear protective shields for a longer than normal period and be followed closely to reduce the risk of flap slippage.

Torische Kunstlinsen zur Korrektur eines persistierenden kornealen Astigmatismus nach perforierender Keratoplastik

PURPOSE

Cataract extraction with implantation of toric intraocular lenses (tIOL) is a new surgical option for correction of residual astigmatism following penetrating keratoplasty and cataract with only minimal direct manipulation of the graft.

PATIENTS AND METHODS

We implanted an individually manufactured backtoric tIOL in 11 eyes of 9 patients. TIOL power calculation was done using vergence transformation in a paraxial space.

RESULTS

Implantation and intraoperative alignment of tIOL were uneventful in all patients. Uncorrected visual acuity increased from 0.1+/-0.06 preoperatively to 0.47+/-0.18 (p=0.006) postoperatively. Best-corrected visual acuity changed from 0.23+/-0.18 preoperatively to 0.6+/-0.14 postoperatively (p=0.002). The refractive cylinder could be reduced from 7.0+/-2.6 D to 1.63+/-1.5 D (p=0.001) after surgery. We observed a small mean deviation from the target axis of 4.1+/-2.9 degrees (0-8 degrees ) after a mean follow-up time of 3.5 (2-7) months.

CONCLUSION

TIOL implantation is a promising option for correction of high astigmatism following penetrating keratoplasty with only minimal direct surgical manipulation of the graft. Regular and symmetric corneal topography is essential for successful implantation of tIOL.

Long Term Analysis of LASIK for the Correction of Refractive Errors After Penetrating Keratoplasty

PURPOSE

To determine the long-term safety and effectiveness of laser in-situ keratomileusis (LASIK) in the treatment of refractive errors following penetrating keratoplasty (PK).

METHODS

A retrospective review was performed of 57 eyes of 48 patients with anisometropia or high astigmatism who were unable to wear glasses or a contact lens after PK and who underwent LASIK for visual rehabilitation. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BCVA), and corneal transplant integrity were recorded before surgery as well as up to 60 months after LASIK.

RESULTS

The mean follow-up after the LASIK was 21.4 +/- 14.2 months (range 3 to 60 months). Mean preoperative spherical equivalent (SE) was -4.19 +/- 3.38 D. The mean preoperative astigmatism was 4.67 +/- 2.18 D. Preoperative BCVA was 20/40 or better in 42 eyes (74%). At 2 years the mean SE was -0.61 +/- 1.81 D, and mean astigmatism was 1.94 +/- 1.35 D for the 28 eyes with follow-up. UCVA was 20/40 or better in 12 eyes (43%), and BCVA was 20/40 or better in 24 eyes (86%) at 2 years. A gain in BCVA of 1 line or more was seen in 8 eyes (29%). Two eyes (7%) had loss of 2 or more lines of BCVA at 2 years. There were 9 eyes (16%) that developed epithelial ingrowth. Five eyes (9%) in this series had repeat corneal transplants.

CONCLUSIONS

LASIK is effective for reducing ametropia after PK. Proper patient counseling is necessary because the results of LASIK after PK are not as good as, and complications are more frequent than in eyes with naturally occurring myopia and astigmatism. Complications are especially common in patients with mismatch of the donor and host cornea or in those with poor endothelial cell function.

Effect of hinged lamellar keratotomy on post-keratoplasty astigmatism and vision

PURPOSE

To show that hinged lamellar keratotomy alone affects refraction and vision in post-keratoplasty eyes.

METHODS

A retrospective, non-comparative, interventional case series was conducted on 28 eyes of 26 patients who had two-stage laser in situ keratomileusis (LASIK) after penetrating keratoplasty. Records were reviewed with respect to the hinged lamellar keratotomy component of the procedure. The interval between keratoplasty and keratotomy was at least 1 year, and the follow-up period averaged 29 +/- 10 days. The Automated Corneal Shaper with nasal hinge was used. In addition to basic empirical astigmatism calculations, the Alpins method of astigmatism analysis was also employed to ensure that the influence of changes in cylinder axis were correctly taken into account when calculating the refractive change.

RESULTS

Surgically induced astigmatism from hinged lamellar keratotomy was not statistically significant in this series; however, the range in values (-9.06 to +7.57 D) has potential clinical ramifications. Nearly 70% of cases studied experienced surgically induced astigmatism of at least 2 D. Mean preoperative uncorrected vision was logMAR 1.06 +/- 0.41, which improved marginally postoperatively to logMAR 1.03 +/- 0.44 (P = 0.36). Best spectacle-corrected visual acuity averaged logMAR 0.21 +/- 0.16 preoperatively, improving to logMAR 0.09 +/- 0.15 (range -0.18 to 0.42) postoperatively, which was a statistically significant improvement (P < 0.01). No difference in refractive or visual outcomes was identified when those with keratoconus were compared to those with other underlying corneal disease processes.

CONCLUSION

Although mean surgically induced astigmatism was not statistically significant, hinged lamellar keratotomy caused considerable changes in astigmatism in nearly 70% of post-keratoplasty eyes studied. This suggests that clinically significant inaccuracies may result if a one-stage LASIK procedure is performed on such patients. The authors suggest that reassessment of refraction after keratotomy may improve refractive outcomes.

Five-Year Results of Laser In-Situ Keratomileusis (LASIK) After Penetrating Keratoplasty

OBJECTIVE

To study the long-term refractive results of LASIK after penetrating keratoplasty.

PLACE

Clinica Barraquer de América.

METHODS

Retrospective review of 46 eyes of 38 patients that underwent LASIK for the correction of refractive errors after penetrating keratoplasty.

RESULTS

The mean interval between keratoplasty and LASIK was 7 years. The preoperative defocus equivalent refraction (DEQ) was 2.0 to 7.0 D in 56% (26/46) of eyes and 8.0 to 24.0 D in the remaining 20 eyes. Five years after LASIK, DEQ was 1.0 to 7.0 D in all eyes. Seventy-five percent of eyes had a refractive error within 2.00 D of emmetropia. Thirty-two percent had uncorrected visual acuity of 20/40 or better, and 59% of eyes gained more than 1 line of best spectacle-corrected visual acuity at 5 years. Vector analysis showed a success index of 60% at 5 years. The refraction in eyes with keratoconus remained stable.

CONCLUSION

LASIK is safe and effective for the correction of refractive errors in eyes that have previously undergone corneal transplantation.

Laser in-situ keratomileusis after penetrating keratoplasty

Laser in situ keratomileusis (LASIK) after penetrating keratoplasty has been used more commonly for the correction of myopia or myopic astigmatism and less so for hypermetropia or hyperopic astigmatism. The primary goal after LASIK in such cases is resolution of sufficient myopia and astigmatism to allow spectacle correction of the residual refractive error and decrease anisometropia. All sutures should be removed prior to LASIK and the interval between penetrating keratoplasty and LASIK should be a minimum of 1 year. Preoperative evaluation includes refraction, slit-lamp biomicroscopy, corneal topography, and specular microscopy. The technique of LASIK surgery after penetrating keratoplasty is similar to the standard procedure. However, many variations have been described. These include maneuvers during surgery such as augmentation with arcuate cuts on the stromal bed and topographically guided LASIK. Other variations are relaxing incisions followed by LASIK surgery and sequential treatment by LASIK, that is, raising of the flap as a first stage procedure followed by ablation if required, 4 to 6 weeks later after relifting the flap in the second stage. Improvement in both uncorrected visual acuity and spectacle-corrected visual acuity, as well as a decrease in spherical equivalent, cylinder, and anisometropia, has been reported in various studies. All grafts were clear and no occurrence of wound dehiscence has been reported. Intraoperative complications include hemorrhage, microkeratome failure, flap buttonhole, dislocation, and perforation. Postoperative complications include undercorrection, decentered ablation, and regression. Re-enhancements after LASIK following keratoplasty are possible with acceptable visual outcome.

Surgical technique for control of postkeratoplasty myopia, astigmatism, and anisometropia

PURPOSE

We previously demonstrated that selective suture removal reduces keratoplasty astigmatism; however, a myopic shift was induced with the increasing number of interrupted sutures removed. This study is an attempt to determine the effects of a modified surgical technique on postkeratoplasty myopia, astigmatism, and anisometropia.

DESIGN

A cohort study compared with historical controls.

METHOD

Optical penetrating keratoplasties were performed on 92 eyes of 84 patients. The study group consisted of 92 consecutive penetrating keratoplasties performed using 12 interrupted 10-0 nylon sutures and a tight 12-bite continuous suture and an average K reading of 46.00 diopters for eyes undergoing combined and intraocular lens exchange procedures. All patients had refraction, keratometry, and videokeratoscopy postoperatively starting at 6 weeks and at the completion of selective suture removal.

RESULTS

Before suture removal, the average spherical equivalent was -0.160 +/- 3.59 diopters; it was -1.58 +/- 3.66 diopters at the completion of suture removal at 1 year and -1.44 +/- 3.72 at the last follow-up visit, averaging 20.7 months. Final refractive, keratometric, and videokeratoscopy astigmatism was 2.81 +/- 1.82, 4.19 +/- 2.94, and 3.58 +/- 2.03 diopters, respectively. Anisometropia, using the spherical equivalent of the operated and fellow eyes, was 2.49 +/- 2.25 diopters at completion of the study. A best-corrected visual acuity of 20/50 or better was achieved in 59% of patients.

CONCLUSIONS

Low myopic spherical equivalent and anisometropia were achieved using a K reading of 46 diopters for calculation of intraocular lens power. The use of tighter continuous sutures and selective removal of fewer interrupted sutures only served to increase final astigmatism, with no significant effect on the final spherical equivalent.

Two-stage Laser in situ Keratomileusis to Correct Refractive Errors After Penetrating Keratoplasty

PURPOSE

To evaluate the effect of a two-stage laser in situ keratomileusis (LASIK) procedure on eyes with high astigmatism and/or anisometropia after penetrating keratoplasty.

METHODS

Eleven postoperative penetrating keratoplasty eyes were included in a prospective, non-controlled study. All patients had at least 4.00 D of astigmatism and/or at least 3.00 D of anisometropia and were spectacle and contact lens intolerant. Two-stage LASIK was performed; in the first stage a hinged corneal flap 160 microm in thickness and 9 mm in diameter was created. After stabilization of corneal shape (1 to 3 months after keratotomy), the corneal flap was lifted and laser refractive treatment (second stage) was performed.

RESULTS

After the first stage, a statistically significant reduction in refractive astigmatism (P<.01) was recorded. In all eyes but one, best spectacle-corrected visual acuity was maintained or improved after the procedure. Three months after the second stage, refractive astigmatism in 8 of 11 eyes (73%) was within +/- 1.00 D, and spherical equivalent refraction in 9 of 11 eyes (82%) was within +/- 1.00 D of intended correction. Preoperative irregular astigmatism persisted in three patients (3 eyes) who could not be corrected within +/- 1.00 D of refractive astigmatism and/or +/- 1.00 D of intended spherical equivalent refraction. In one eye, an interface infiltrate developed shortly after creation of the flap, and resulted in limited melting.

CONCLUSIONS

A two-stage LASIK procedure improved visual acuity and refraction in postoperative penetrating keratoplasty eyes with high astigmatism and/or anisometropia. Complications were uncommon but can lead to loss of vision.

Laser in situ keratomileusis combined with topography-supported customized ablation after repeated penetrating keratoplasty

I report the case of a 32-year-old woman who had penetrating keratoplasty (PKP) in both eyes because of keratoconus. After PKP, a high degree of spherical myopia and irregular astigmatism prevented optical correction. The patient then had laser in situ keratomileusis (LASIK) combined with topography-supported customized ablation (TOSCA) in both eyes. The procedure resulted in a significant reduction in spherical myopia and astigmatism. A tissue-sparing algorithm was used to plan the refractive treatment. There were no intraoperative or postoperative complications, and the treated corneas maintained transparency. TOSCA-supported LASIK is a useful method for dealing with specific refractive problems after PKP.

Correction of astigmatism with short arc-length intrastromal corneal ring segments: preliminary results

OBJECTIVE

To evaluate the refractive effect of 130 degrees short arc length intrastromal corneal ring segments (ICRS) designed to correct myopia concurrent with astigmatism.

DESIGN

Prospective, nonrandomized, comparative (self-controlled) trial.

PARTICIPANTS

Ten eyes of 6 patients from one surgical center with manifest refraction spherical equivalent between -1.00 and -6.00 diopters (D), manifest cylinder correction between 1.00 and 6.00 D, and best spectacle-corrected visual acuity of 20/20 or better.

INTERVENTION

The patients were assigned to receive 1 of 6 ICRS thicknesses, ranging from 0.25 to 0.50 mm by 0.05 mm increments, with an arc length of 130 degrees.

MAIN OUTCOME MEASURES

Vector analysis of astigmatic correction. Efficacy was assessed by uncorrected visual acuity and by deviation of postoperative spherical and cylindrical refractive error from predicted correction. Safety was assessed by maintenance or loss of preoperative best spectacle-corrected visual acuity. Measurements were made before surgery and after surgery at days 1 and 7 and months 1, 2, 3, and 6.

RESULTS

At 6 months, uncorrected visual acuity was 20/20 or better in 80% of eyes (8/10) and 20/40 or better in all eyes. Eight of 10 eyes (80%) were within +/-0.25 D of plano spherical equivalent manifest refraction. There was no loss of best spectacle-corrected visual acuity, and 6 of 10 eyes (60%) gained a line. Reduction of keratometric cylinder by ICRS thickness was statistically significant (P = 0.039).

CONCLUSIONS

Preliminary results of visual and refractive performance after correction of compound myopic astigmatism using short arc length ICRS are promising.

Correction of myopia and astigmatism after penetrating keratoplasty with laser in situ keratomileusis

PURPOSE

We evaluated whether laser in situ keratomileusis (LASIK) was a safe and effective treatment for myopia and astigmatism after penetrating keratoplasty (PK).

METHODS

We performed a retrospective review of medical records of all the patients who underwent LASIK following PK at the University of Minnesota between January 1999 and March 2000.

RESULTS

Seventeen patients (20 eyes) underwent LASIK following PK between January 1999 and March 2000. Mean age of the patients at the time of LASIK was 37 years (range, 20-62). Keratoconus was the indication for PK in the majority of the eyes (73.7%). Anisometropia and/or contact lens intolerance was the indication for LASIK following PK. No intraoperative complications occurred. Following LASIK, the best spectacle-corrected visual acuity remained within 1 line of preoperative visual acuity in 94.7% of the eyes. The mean sphere was reduced by 3.93 diopters (80.0%) and the mean cylinder was reduced by 2.83 diopters (69.9%) from the preoperative values at the last follow-up visit. Uncorrected visual acuity became 20/40 or better in 73.7% of the eyes after LASIK.

CONCLUSIONS

LASIK is a safe procedure in eyes in which PK has previously been performed. LASIK is effective in the treatment of myopia and astigmatism following PK.

Astigmatism and LASIK

Although laser in situ keratomileusis (LASIK) enjoys a high success rate, postoperative residual or induced astigmatism may limit uncorrected visual acuity and cause starbursts and glare at night. Irregular astigmatism can also cause loss of best-corrected visual acuity, monocular diplopia, and ghosting of images. Astigmatism may be measured by keratometry and refraction, while corneal topographic techniques help to define irregular astigmatism, in particular. Further information may be obtained regarding induced higher-order aberrations with aberrometry. Because astigmatism has both direction and magnitude, its analysis is more complex than that of the spherical component of the treatment. There are multiple approaches to the analysis of surgically induced astigmatism, including vector analysis, conversion to a Cartesian coordinate system, matrix formalism, and linear optics. Both excimer laser and incisional techniques may be used to correct astigmatism after LASIK, but the treatment of irregular astigmatism requires selective zonal ablation techniques or customized corneal ablations, using topographic or wavefront derived data.

Treatment of post-keratoplasty astigmatism by topography supported customized laser ablation

PURPOSE

To evaluate the clinical and optical efficiency of topography modulated customized corneal ablations for irregular corneal astigmatism.

MATERIAL & METHODS

Sixteen eyes of 16 patients with iatrogenic corneal astigmatism (post keratoplasty) were consecutively included. Based on preoperative corneal topographic measurements height deviations from a spherical corneal shape were calculated and transferred to a flying-spot excimer laser. Photo-refractive keratectomy of the topographic irregularities was then performed. Clinical and optical efficiency was evaluated by best corrected visual acuity and by computation of corneal wavefront aberrations before and up to one year after treatment. Wavefront aberrations were decomposed by Zernike polynomial analysis.

RESULTS

Before treatment the average best-corrected visual acuity was 0.23. Three and 12 months after PRK the average best-corrected visual acuity had increased to 0.37 (p<0.05) and 0.45 (p<0.05), respectively. Corneal wavefront aberrations (root-mean-square) were 3.35 before surgery and 1.88 (p<0.05) and 1.51 (p<0.05) at three and 12 months after treatment. Zernike polynomial decomposition of the wavefront aberrations revealed that regular corneal astigmatism was the most important aberration component before and after surgery. Regular astigmatism was significantly decreased by the procedure, whereas coma, spherical aberrations, and higher-order aberrations were not reduced significantly.

CONCLUSION

Topography modulated photorefractive keratectomy of highly astigmatic corneal grafts can improve best corrected visual acuity and reduce corneal wavefront aberrations. Even in apparently irregular topographic astigmatism, regular astigmatic wavefront aberration may be the most important contributor to wavefront errors.