One-year follow-up results of photorefractive keratectomy for low, moderate, and high primary astigmatism

Macular choroidal thickness in keratoconus

CLINICAL RELEVANCE

Expanding practitioner knowledge regarding potential changes in ocular structure of keratoconic eyes will improve the eye care practice and patient management.

BACKGROUND

This study aimed to compare the difference in choroidal thickness between keratoconus patients and two control groups of myopic-astigmatism and emmetropic subjects.

METHODS

A case-control study was undertaken which included 50 patients with keratoconus, 50 with myopic-astigmatism, 30 with emmetropia aged between 18 and 39 years. Choroidal thickness was measured at three different locations, including the subfoveal, nasal, and temporal (750 micrometres) to the fovea, using a spectral-domain optical coherence tomography with an enhanced depth imaging technique.

RESULTS

The mean spherical equivalents were 0.03 ± 0.05, -3.00 ± 0.2, and -3.00 ± 0.3 dioptre in emmetropic, myopic-astigmatism and keratoconus subjects, respectively. The choroid was significantly thicker in keratoconus patients than in myopic-astigmatism and emmetropic subjects in the subfoveal (396 ± 14, 314 ± 12, and 320 ± 18 μm, respectively, p < 0.001), temporal (405 ± 14, 317 ± 12, and 328 ± 19 μm, respectively, p < 0.001) and nasal (376 ± 14, 285 ± 12, and 311 ± 18 μm, respectively; p < 0.001).

CONCLUSION

Choroidal thickness is increased in keratoconus. The exact mechanism for choroidal thickening in individuals with keratoconus is unknown, but inflammatory responses could be the reason.

Three-year outcomes of mixed astigmatism correction with single-step transepithelial photorefractive keratectomy with a large ablation zone

PURPOSE

To evaluate refractive and visual outcomes of single-step transepithelial photorefractive keratectomy (transPRK) in the treatment of mixed astigmatism with the use of an aberration-neutral profile and large ablation zone.

SETTING

Nicolaus Copernicus University and Oftalmika Eye Hospital, Bydgoszcz, Poland.

DESIGN

Retrospective, observational case series.

METHODS

This study included patients who underwent transPRK to correct mixed astigmatism and completed the 3-year follow-up. Procedures were performed with an Amaris 750S excimer laser using an aberration-neutral profile and optical zone of 7.2 mm or more.

RESULTS

A total 48 eyes of 39 patients were included. Preoperatively, mean spherical manifest refraction was +1.37 ± 0.98 diopter (D) (0.25 to 4.00 D), and astigmatism was -4.00 ± 0.76 D (-2.25 to -6.00 D). Three years postsurgery, it was -0.17 ± 0.26 D and -0.41 ± 0.44 D, respectively. Attempted spherical equivalent correction within ±0.50 D was achieved in 45 eyes (94%) and cylindrical correction in 34 (71%). Preoperative corrected distance visual acuity (CDVA) was 20/20 or better in 38 eyes (79%), and postoperative uncorrected was 20/20 or better in 29 eyes (60.0%). No eye had lost 2 or more Snellen lines of CDVA, whereas 3 eyes (6%) gained 2 or more lines. In 4 eyes (8%), haze of low intensity was observed at the periphery, with scores between 0.5 and 1.0, and only 1 eye getting a score of 2 in 0- to 4-degree scale.

CONCLUSIONS

Mixed astigmatism correction with large-ablation-zone transPRK provided good results for efficacy, safety, predictability, and visual outcomes in a 3-year follow-up.

Four-year outcomes of small incision lenticule extraction (SMILE) to correct high myopic astigmatism

AIMS

To evaluate the long-term outcomes of small incision lenticule extraction (SMILE) in subjects with myopic astigmatism of ≥2.00 dioptres (D).

METHODS

Patients who underwent SMILE 4 years prior with astigmatism ≥2.00 D and ≤1.00 D were assigned to the high astigmatic group (HA group) or the low astigmatic group (LA group), respectively. The visual and refractive results as well as corneal wavefront aberrations were measured.

RESULTS

The preoperative cylinder was -2.47±0.54 D in 43 eyes in the HA group and -0.55±0.28 D in 31 eyes in the LA group. At 4 years, the residual cylinder was -0.31±0.29 D in the HA group and -0.20±0.28 D in the LA group (p=0.088). An uncorrected distance visual acuity of 20/20 was achieved in 88.4% of eyes in the HA group and 93.5% of eyes in the LA group. The efficacy index was 0.99±0.14 and 1.10±0.21 (p=0.025), and the safety index was 1.11±0.20 and 1.22±0.21 in the HA and LA groups, respectively (p=0.012). Eighty-six per cent and 90.3% of eyes were within ±0.50 D of the attempted cylindrical correction in the HA and LA groups, respectively. Vector analysis showed that the magnitude of error was -0.14±0.28 D and -0.05±0.16 D (p=0.085), the angle of error was -0.13±4.48 degrees and -2.57±29.42 degrees (p=0.592), the correction index was 0.94±0.13 and 0.94±0.35 (p=0.959), the index of success was 0.15±0.14 and 0.46±0.62 (p=0.517), and the flattening index was 0.93±0.13 and 0.71±0.59 (p=0.450) in the HA and LA groups, respectively.

CONCLUSIONS

This study demonstrates that SMILE is effective and safe for correcting high astigmatism. Vector analysis shows a tendency for the undercorrection of astigmatism in subjects with high astigmatism.

Transepithelial Photorefractive Keratectomy in Moderate to High Astigmatism With a Non-wavefront-Guided Aberration-Neutral Ablation Profile

PURPOSE

To evaluate the outcomes of transepithelial photorefractive keratectomy (PRK) in moderate to high astigmatism with a non-wavefront-guided aberration-neutral ablation profile using SmartPulse allocation.

METHODS

In this retrospective study, myopic patients with a preoperative cylinder of 2.00 diopters (D) or greater were analyzed at 3 months of follow-up. Transepithelial PRK treatments were performed in each patient with the Amaris 1050RS laser (SCHWIND eye-tech-solutions, Kleinostheim, Germany) creating aspheric ablation profiles by applying a SmartPulse allocation. Standard examinations and wavefront analyses were included for low and high ocular residual astigmatism subgroups.

RESULTS

Fifty-eight eyes (44 patients) were included in the cohort. The eyes were divided into separate ocular residual astigmatism subgroups: 17 eyes presented with less than 0.50 D (low ocular residual astigmatism) and 24 eyes with greater than 0.75 D (high ocular residual astigmatism). The mean refractive cylinder in the entire cohort was 2.84 ± 0.86 D preoperatively and 0.40 ± 0.39 D postoperatively, with 81% of the eyes within 0.75 D of the target astigmatism. At 3 months of follow-up, significant improvement (P < .05) was seen in terms of sphere, cylinder, spherical equivalent, and uncorrected (UDVA) and corrected (CDVA) distance visual acuity. CDVA improved in 40% of eyes and 3% of eyes lost one line of CDVA. No clinically relevant changes were seen in higher order aberrations. The refractive changes showed an excellent match with the keratometric changes. The difference between the low and high ocular residual astigmatism subgroups was not significant except for the change of Snellen lines of CDVA (P < .05).

CONCLUSIONS

Transepithelial PRK using a non-wavefront-guided aberration-neutral ablation profile performed by applying SmartPulse allocation yielded excellent visual outcomes. The preoperative astigmatism was reduced to subclinical values. Both subgroups were effective in terms of UDVA, CDVA, spherical and astigmatic correction, and preserving higher order aberrations. However, the low ocular residual astigmatism subgroup was slightly more prone to gain lines of CDVA. [J Refract Surg. 2018;34(7):466-474.].

Early outcomes after small incision lenticule extraction and photorefractive keratectomy for correction of high myopia

We prospectively compared visual and refractive outcomes in patients with high myopia and myopic astigmatism after small-incision lenticule extraction (SMILE) and photorefractive keratetctomy (PRK) with mitomycin C. Sixty-six eyes of 33 patients (mean age, 29.7 ± 5.6 years) were included (SMILE: 34 eyes, PRK 32 eyes). Preoperatively, no significant difference was noted in manifest spherical equivalent (p = 0.326), manifest sphere (p = 0.277), and manifest cylinder (p = 0.625) between both groups. At 1 month, there were significant differences in logMAR uncorrected distance visual acuity, efficacy index and manifest refraction spherical equivalent between SMILE and PRK (p ≤ 0.029). At 6 months, the logMAR corrected distance visual acuity (p = 0.594), logMAR uncorrected visual acuity (p = 0.452), efficacy index (p = 0.215) and safety index was (p = 0.537) was comparable between SMILE and PRK. Significant differences were observed in postoperative manifest spherical equivalent (p = 0.044) and manifest cylinder (p = 0.014) between both groups. At the end of 6 months, 100% of the eyes in SMILE group and 69% of the eyes in PRK group were within ±0.50 D of the attempted cylindrical correction. The postoperative difference vector, magnitude of error and absolute angle of error were significantly smaller after SMILE compared to PRK (p ≤ 0.040) implying a trend towards overcorrection of cylindrical correction following PRK.

Comparison of femtosecond laser small-incision lenticule extraction and laser-assisted subepithelial keratectomy to correct myopic astigmatism

PURPOSE

To compare the efficacy of correcting myopic astigmatism with femtosecond laser small-incision lenticule extraction (SMILE, Carl Zeiss Meditec AG) versus laser-assisted subepithelial keratectomy (LASEK).

SETTING

The study was conducted at the Ophthalmology Department, Eye and ENT Hospital, Shanghai, China.

DESIGN

A retrospective, cross-sectional study.

METHODS

This study included patients who underwent small-incision lenticule extraction or LASEK for the correction of myopia and myopic astigmatism. Preoperative and 6-month postoperative astigmatism values were analyzed. The efficacies of the 2 surgeries to correct astigmatism were compared.

RESULTS

A total of 180 right eyes of 180 patients (small-incision lenticule extraction: n = 113, LASEK: n = 67) were included. No significant difference was found between the 2 groups in the preoperative astigmatism (small-incision lenticule extraction: 1.16 ± 0.85D, LASEK: 1.16 ± 0.83D, P > .05) or the postoperative astigmatism (small-incision lenticule extraction: 0.35 ± 0.37D; LASEK: 0.31 ± 0.42D, P > .05), determined by manifest refraction. No significant difference was found between the 2 groups in surgically induced astigmatism vector (small-incision lenticule extraction: 1.13 ± 0.83D, LASEK: 1.01 ± 0.65D, P > .05). The correction index was higher for the small-incision lenticule extraction group (1.05 ± 0.53) than for the LASEK group (0.95 ± 0.21, P = .045). The postoperative astigmatism was significantly higher for the small-incision lenticule extraction group when the preoperative astigmatism was 1.0 D or less (small-incision lenticule extraction: 0.26 ± 0.30D, LASEK: 0.12 ± 0.20D, P = .007) and lower for the small-incision lenticule extraction group when the preoperative astigmatism was more than 2.0 D (small-incision lenticule extraction: 0.48 ± 0.37D, LASEK: 0.89 ± 0.46D, P = .002).

CONCLUSIONS

An adjustment of nomograms for correcting low astigmatism (≤1.0 D) by small-incision lenticule extraction is suggested due to the tendency toward overcorrection, whereas a nomogram adjustment for tissue-saving ablation profile is needed for the correction of high astigmatism (>2.0 D) by LASEK due to the tendency toward undercorrection.

FINANCIAL DISCLOSURE

The authors declare that they have no competing financial interests.

Visual performance in cataract patients with low levels of postoperative astigmatism: full correction versus spherical equivalent correction

Purpose

To evaluate whether visual performance could be improved in pseudophakic subjects by correcting low levels of postoperative astigmatism.

Methods

An exploratory, noninterventional study was conducted using subjects who had been implanted with an aspheric intraocular lens and had 0.5–0.75 diopter postoperative astigmatism. Monocular visual performance using full correction was compared with visual performance using spherical equivalent correction. Testing consisted of high- and low-contrast visual acuity, contrast sensitivity, and reading acuity and speed using the Radner Reading Charts.

Results

Thirty-eight of 40 subjects completed testing. Visual acuities at three contrast levels (100%, 25%, and 9%) were significantly better using full correction than when using spherical equivalent correction (all P < 0.001). For contrast sensitivity testing under photopic, mesopic, and mesopic with glare conditions, only one out of twelve outcomes demonstrated a significant improvement with full correction compared with spherical equivalent correction (at six cycles per degree under mesopic without glare conditions, P = 0.046). Mean reading speed was numerically faster with full correction across all print sizes, reaching statistical significance at logarithm of the reading acuity determination (logRAD) 0.2, 0.7, and 1.1 (P < 0.05). Statistically significant differences also favored full correction in logRAD score (P = 0.0376), corrected maximum reading speed (P < 0.001), and logarithm of the minimum angle of resolution/logRAD ratio (P < 0.001).

Conclusions

In this study of pseudophakic subjects with low levels of postoperative astigmatism, full correction yielded significantly better reading performance and high- and low-contrast visual acuity than spherical equivalent correction, suggesting that cataractous patients may benefit from surgical correction of low levels of preoperative corneal astigmatism.

Wavefront-guided versus cross-cylinder photorefractive keratectomy in moderate-to-high astigmatism: a cohort of two consecutive clinical trials

Background

Although there have been many studies of the efficacy and safety of wavefront- guided (WF) and cross-cylinder photorefractive keratectomy (PRK), there are few studies on moderate-to-high astigmatism cases. The aim of this study was to assess and compare the efficacy of WF and cross-cylinder PRK in moderate-to-high astigmatism.

Methods

In a comparative cohort, the results of two before-and-after clinical trials conducted on moderate-to-high astigmatism were studied. In the first trial, 50 eyes of 25 patients with stable refraction were enrolled in a before-and-after clinical trial to undergo WF PRK using the VISX™ (VISX Inc, Santa Clara, CA) system. The second clinical trial enrolled 48 eyes of 24 patients with stable refraction and moderate-to-high astigmatism to undergo PRK by the cross-cylinder method using a NIDEK EC-5000 excimer laser system (NIDEK Co Ltd, Gamagori, Japan).

Results

After 6 months, 80% of the eyes in the WF group had uncorrected visual acuity of 20/20 or better compared to 40% in the cross-cylinder group. Only one eye in the cross-cylinder group and no eyes in the WF group lost more than one line of best corrected visual acuity (BCVA) after 6 months of treatment. No treated eyes in either group lost more than two lines of BCVA. The percentage of eyes with no change in BCVA was 54% and 58.3% in the WF and cross-cylinder groups, respectively. Mean postoperative absolute changes in total root-mean-square higher order aberrations in the WF group and cross-cylinder group were 0.05 ± 0.22 μm and 0.17 ± 0.20 μm, respectively (P < 0.001).

Conclusion

Both methods of PRK, using the NIDEK EC-5000 and VISX excimer laser systems, are effective for correcting moderate-to-high astigmatism. The WF approach appeared more successful in improving the refractive results.

Excimer laser correction of moderate to high astigmatism with a non-wavefront-guided aberration-free ablation profile: Six-month results

PURPOSE

To evaluate the postoperative clinical outcomes and higher-order aberrations (HOAs) in eyes with astigmatism greater than 2.00 diopters (D) that had laser in situ keratomileusis (LASIK) using a non-wavefront-guided aberration-free ablation profile.

SETTINGS

Private practice.

METHODS

This retrospective study evaluated the 6-month results of LASIK for astigmatism greater than 2.00 D. Standard examinations and preoperative and postoperative wavefront analyses were performed. Aspheric treatments with a non-wavefront-guided ablation profile were planned using software integrated into the Amaris flying-spot excimer laser system, which was used to perform the ablations. The LASIK flaps were created using an LDV femtosecond laser. Clinical outcomes were predictability, refractive outcomes, safety, efficacy, and wavefront aberration.

RESULTS

At 6 months, 84% of the 50 eyes evaluated achieved 20/20 or better uncorrected distance visual acuity (UDVA) and 40% achieved 20/16 or better UDVA. Forty-four percent of eyes were within +/-0.25 D of the attempted astigmatic correction, and 78% were within +/-0.50 D. The mean SE was -0.12 D +/- 0.25 (SD) and the mean astigmatism, 0.50 +/- 0.26 D. Corrected distance visual acuity (CDVA) improved in 36% of eyes; 4% of eyes lost 1 line of CDVA. The predictability slope for astigmatism was 0.97 and the intercept, -0.15 D. There were no clinically relevant changes in any aberration metric from preoperatively to postoperatively.

CONCLUSIONS

Excimer laser LASIK using a non-wavefront-guided aberration-free ablation profile yielded excellent visual outcomes. The preoperative astigmatism was reduced to subclinical values with no clinically relevant induction of HOA.

Three different techniques for photorefractive keratectomy for mixed astigmatism

BACKGROUND AND OBJECTIVE

To compare three different PRK techniques for the correction of mixed astigmatism.

PATIENTS AND METHODS

Sixty eyes of 40 patients affected by mixed astigmatism underwent PRK using an excimer laser with three different techniques: (A) combined myopic spherical and hyperopic cylindrical treatment (mean attempted correction in defocus equivalent [DE], 2 +/- 0.4 D), (B) combined cross-cylinder and spherical equivalent treatment (mean attempted correction in DE, 2.72 +/- 0.6 D), and (C) customized ablation with topography-supported customized ablation (TOSCA) method (mean attempted correction in DE, 2.67 +/- 0.9 D).

RESULTS

Twelve months postoperatively, the mean DE in group A was 0.45 +/- 0.6 D and an UCVA of 20/40 or better was achieved in 80% of eyes; the mean DE in group B was 0.55 +/- 0.4 D and an UCVA of 20/40 or better was achieved in 70%; and the mean DE in group C was 0.38 +/- 0.1 D and an UCVA of 20/40 or better was achieved in 90%. No patient lost more than 2 lines of spectacle-corrected visual acuity and there were no complications observed during the follow-up. No statistically significant difference among the three groups was evidenced.

CONCLUSIONS

PRK for the correction of mixed astigmatism can be considered a useful technique in terms of efficacy, safety, and predictability with all three tested techniques.

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.

Analysis of the efficacy, predictability, and safety of LASEK for myopia and myopic astigmatism using the Technolas 217 excimer laser

PURPOSE

To evaluate the efficacy, predictability, and safety of laser-assisted subepithelial keratectomy (LASEK) for the treatment of myopia and myopic astigmatism.

SETTING

Stanford University Eye Laser Center, Stanford, California, USA.

METHODS

This retrospective analysis comprised 102 eyes that had LASEK for myopia using the Bausch & Lomb Technolas 217 excimer laser. Primary outcome variables including uncorrected visual acuity (UCVA), best spectacle- corrected visual acuity (BSCVA), manifest refraction, and complications were evaluated at 3, 6, and 12 months. Vector analysis was performed on eyes that received astigmatic correction.

RESULTS

The mean spherical equivalent was -7.03 diopters (D) +/- 2.61 (SD) preoperatively, +0.19 +/- 0.64 D at 3 months, +0.23 +/- 0.82 D at 6 months, and +0.03 +/- 0.63 D at 12 months (P<.001). At 3, 6, and 12 months, the UCVA was 20/20 or better in 66%, 67%, and 83% of eyes, respectively, and 20/40 or better in 98%, 99%, and 100%; 74%, 70%, and 83%, respectively, were within +/-0.5 D of emmetropia, and 89%, 86%, and 97%, respectively, were within +/-1.0 D. No eye lost more than 2 lines of BSCVA. At 3, 6, and 12 months, 10.0%, 8.7%, and 0% of eyes, respectively, had trace corneal haze. Vector analysis found a success rate of approximately 78% to 80% in achieving the astigmatic surgical correction at the 3 postoperative visits.

CONCLUSIONS

Laser-assisted subepithelial keratectomy was an effective, predictable, and safe procedure for the treatment of myopia and myopic astigmatism. Further studies are needed to determine the role of LASEK in the refractive surgery spectrum.

Hyperopic Photorefractive Keratectomy With Adjunctive Topical Mitomycin C for Refractive Error After Penetrating Keratoplasty for Keratoconus

OBJECTIVE

To present a case of photorefractive keratectomy (PRK) with adjunctive topical mitomycin C (MMC) in an anisometropic hyperopic patient after penetrating keratoplasty (PKP) for keratoconus.

METHODS

Interventional case report, chart review, and literature review.

RESULTS

A 43-year-old man with a refraction of +7.00 -4.75 x 125 in the right eye underwent PRK 10 months after PKP for keratoconus. The patient had sutures removed for 3 months and was intolerant of contact lenses. After photoablation, 0.02% MMC was applied to the corneal stromal bed. The patient was followed up daily until the epithelium closed and at 1 week, 1 month, 3 months, and 6 months postoperatively.

CONCLUSIONS

To our knowledge, this represents the first reported case of the use of MMC to prevent postoperative haze after PRK for PKP in an eye with keratoconus. MMC (0.02%) applied topically to the cornea immediately after PRK is safe and effective to treat a hyperopic refractive error after PKP and prevent postoperative corneal haze formation without the risks of performing a lamellar flap into an ectatic corneal bed.

New Formula to Calculate Corneal Power After Refractive Surgery

PURPOSE

To assess the validity of intraocular lens (IOL) power calculations utilizing a theoretical variable refractive index correlated to axial length after myopic photorefractive keratectomy (PRK) in a clinical simulation and in patients who underwent cataract surgery after PRK for myopia.

METHODS

Our study included 374 eyes of 300 patients who had PRK for myopia (-2.00 to -12.00 D, mean -4.83 +/- 2.57 D), divided into three groups: Group I had 44 eyes with small ablation zones of 5 to 5.5 mm; Group II had 49 eyes with large ablation zones of 6 to 7 mm; Group III was the control group of 281 eyes (201 patients; 87 males and 114 females) with small and large ablation zones. PRK was performed using the Aesculap-Meditec MEL 60/94 and MEL 70 lasers, and the corneal power was acquired by corneal topography (EyeSys 2000) and a Nidek KM-800 keratometer.

RESULTS

There was a higher correlation between corneal power and both the change in refraction and axial length when calculated using keratometric measurements. IOL power calculated using keratometric postoperative PRK power was underestimated. The difference between the mean calculated and actual IOL power for emmetropia was 4.30 +/- 2.34 D. A theoretical variable refractive index (obtained from eyes treated with large PRK ablation zones) that correlated with axial length provided the correct keratometric postoperative PRK power: difference between mean calculated and mean actual IOL power was 0.42 +/- 1.23 D.

CONCLUSIONS

We propose a theoretical variable refractive index that is correlated to axial length. Utilizing this keratometric correct power, we calculated IOL power similar to that for emmetropia.

Topography-guided Laser in situ Keratomileusis (TOPOLINK) to Correct Irregular Astigmatism After Previous Refractive Surgery

PURPOSE

To assess whether topography-driven laser in situ keratomileusis (LASIK) can correct induced corneal irregular astigmatism.

METHODS

A prospective non-comparative case series of 41 eyes (38 patients) with irregular astigmatism following corneal refractive surgery, included two groups: Group 1 (26 eyes) with a defined topographic pattern and Group 2 (15 eyes) with no pattern. Ablation was performed using the Technolas 217C excimer laser with a software ablation program (TOPOLINK) based on corneal topography. Uncorrected and best spectacle-corrected visual acuity, manifest and cycloplegic refraction, corneal topography, superficial corneal surface quality, and image distortion were measured.

RESULTS

At 6 months follow-up in Group 1 eyes (defined topographic pattern) mean preoperative BSCVA improved from 0.16 +/- 0.11 LogMAR (0.4 to 0) to 0.09 +/- 0.10 LogMAR (0.2 to 0) (P = .001) (safety index of 1.1). In Group 2 eyes (no pattern), mean preoperative BSCVA was 0.18 +/- 0.11 LogMAR (0.4 to 0), similar to the postoperative BSCVA of 0.17 +/- 0.10 LogMAR (0.3 to 0) (safety index of 0.98). Mean postoperative UCVA was > or = 0.3 LogMAR in 25 eyes (96.2%) in Group 1 (efficacy index of 0.8) and 7 eyes (46.6%) in Group 2 (efficacy index of 0.5). Both superficial corneal surface quality and image distortion significantly improved in Group 1; there were no significant changes in Group 2. We reoperated nine eyes (21.9%).

CONCLUSIONS

Topographic-assisted LASIK was helpful in selected cases where irregular astigmatism showed a pattern. It was ineffective in undefined irregular astigmatism. Partial correction of the irregularity and regression of the obtained effect was common.

Photorefractive keratectomy for compound myopic astigmatism with the MEL-70 G-Scan excimer laser

PURPOSE

To assess the safety, efficacy, predictability and stability of photorefractive keratectomy in compound myopic astigmatism with a moderate and high cylinder component.

METHODS

Photorefractive keratectomy was done in 42 eyes with compound myopic astigmatism with the spherocylindrical algorithm of the MEL-70 excimer laser, with wide ablation zones.

RESULTS

Spherical equivalent refraction changed from -4.19 +/- 1.65D to -0.05 +/- 0.31D, refractive cylinder from -2.01 +/- 0.71D to -0.09 +/- 0.20D and mean sphere from -3.22 +/- 1.76D to -0.02 +/- 0.26D. Mean uncorrected visual acuity rose from 0.12 +/- 0.17 to 0.91 +/- 0.10. No eye lost lines of spectacle-corrected visual acuity. The safety index was 1.03 and the efficacy index 0.98. Six months from the treatment all eyes were within +/- 1D, 8.9% of eyes were within 0.50D and 44% were plano of target refraction. Refractive and topographical stability were achieved between one and three months after treatment. Transient haze was observed between one and three months after PRK.

CONCLUSIONS

Photorefractive keratectomy with the MEL-70 excimer laser to correct myopic astigmatism was a safe and effective procedure with good stability at six months' follow-up. Refractive and visual outcome confirmed that excellent predictability can be expected.

Predictability and outcomes of photoastigmatic keratectomy using the Nidek EC-5000 excimer laser

PURPOSE

To evaluate the effect of astigmatic correction on the accuracy of the myopic and astigmatic correction in patients having photorefractive astigmatic keratectomy (PARK) and in those having photorefractive keratectomy (PRK).

SETTING

Specialist excimer laser refractive clinic.

METHODS

This prospective consecutive case series comprised 6097 eyes with a preoperative mean spherical equivalent (MSE) of -4.63 diopters (D) +/- 1.95 (SD) (range -0.75 to -13.00 D) and a mean cylinder of -1.13 +/- 0.73 D (range -0.50 to -6.00 D) having PARK with a Nidek EC-5000 excimer laser. Visual and refractive outcomes were assessed 12 months postoperatively and compared with those in 3004 eyes that had spherical PRK.

RESULTS

At 12 months, the MSE was -0.02 +/- 0.79 D and the mean cylinder was -0.49 +/- 0.47 D in the PARK group; the MSE was -0.07 +/- 0.66 D in the PRK group. An MSE within +/-0.05 D of emmetropia was achieved by 69.8% and within +/-1.00 D, by 87.9%. The uncorrected visual acuity (UCVA) was 20/20 or better in 42.6% and 20/40 or better in 91.2%. Statistical significance (P <.001, analysis of variance) was achieved for MSE, sphere, cylinder, haze, and visual acuity (best corrected [BCVA] and UCVA) based on the preoperative cylinder. The loss of BCVA varied from 1.1% to 5.8% depending on the degree of astigmatism treated. Accuracy varied with the attempted myopic correction and the attempted astigmatic correction.

CONCLUSIONS

Excimer laser PARK was an effective treatment for compound myopic astigmatism, but predictability decreased and complications increased as the attempted astigmatic correction increased.

Corneal astigmatic change after photorefractive keratectomy and photoastigmatic refractive keratectomy

PURPOSE

To evaluate and compare the efficacy, safety, predictability, and surgically induced astigmatism (SIA) of photorefractive keratectomy (PRK) and photoastigmatic refractive keratectomy (PARK).

SETTING

Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.

METHODS

In this retrospective study, 70 eyes were treated for myopia and 70 eyes were treated for myopic astigmatism. Refraction, corneal topography, slitlamp findings, and visual acuity in the 2 groups at 1, 3, and 6 months were evaluated and compared. Vector analysis was performed to determine the SIA in both groups.

RESULTS

The mean preoperative spherical equivalent at the glasses plane in the PRK and PARK groups was -6.06 diopters (D) and -7.18 D, respectively. At 6 months, the mean reduction in astigmatism in the PARK group was 61.0%. Predictability was within +/-1.0 D in 85.2% of eyes in the PRK group and 62.5% in the PARK group. An uncorrected visual acuity of 20/40 or better was achieved in 91.8% and 83.9% of eyes, respectively. The mean SIA was 0.64 D in the PRK group, with a general with-the-rule axis shift. The results of vector analysis were more favorable when calculated from refractive values than from Sim-K corneal topography values. The mean astigmatism correction index and index of success calculated from refractive data were 0.75 and 0.38 in the PARK group. The mean magnitude and angle of error were 0.22 +/- 0.52 D and -2.13 +/- 24.41 degrees, respectively.

CONCLUSIONS

Photorefractive keratectomy and PARK were effective and safe procedures for the correction of myopia and myopic astigmatism. However, SIA occurred with spherical myopic treatments. This small SIA may be a confounding factor in low astigmatic treatments.

Laser in situ keratomileusis for the correction of myopia and myopic astigmatism

PURPOSE

To evaluate the efficacy, safety, predictability, and surgically induced astigmatism (SIA) of laser in situ keratomileusis (LASIK) for the correction of myopia and myopic astigmatism.

SETTING

Department of Ophthalmology, National Taiwan University Hospital, Taipei, Taiwan.

METHODS

This retrospective study comprised 69 eyes that had LASIK to correct myopia and 74 eyes that had LASIK to correct myopic astigmatism. The excimer laser keratectomy was performed using a Summit Apex Plus machine. Refraction, visual acuity, and computerized corneal videokeratography data from the preoperative and postoperative examinations were collected. The astigmatic change was calculated by the Alpins vector analysis method.

RESULTS

The preoperative spherical equivalent at the glasses plane in the myopia and myopic astigmatism groups was -8.08 diopters (D) and -9.73 D, respectively. At 6 months, the spherical equivalent and residual corneal astigmatism were -0.25 D and 0.85 D, respectively, in the myopia group and -0.71 D and 0.82 D, respectively, in the myopic astigmatism group. In the myopia group, 88% of eyes were within +/-1.0 D of the intended myopia correction and in the myopic astigmatism group, 85% were within +/-1.0 D of the targeted spherical equivalent and 90% were within +/-1.0 D of the intended astigmatism correction. The uncorrected visual acuity was 20/40 or better in 94.1% of eyes in the myopia group and 92.5% of eyes in the myopic astigmatism group. The SIA magnitude was 0.66 D with the axis randomly distributed in the myopia group. The mean astigmatism correction index was 0.97, the mean magnitude of error was 0.13 D +/- 0.62 (SD), and the mean angle of error was -3.70 +/- 13.73 degrees in the myopic astigmatism group.

CONCLUSION

Laser in situ keratomileusis had similar predictability, safety, and efficacy in the treatment of myopia and myopic astigmatism. The astigmatism correction was effective, but the results suggest that subjective astigmatism of less than 1.0 D need not be treated with the Summit Apex Plus laser.

Photorefractive keratectomy for post-penetrating keratoplasty myopia and astigmatism

PURPOSE

To determine the safety, effectiveness, and predictability of photorefractive keratectomy (PRK) for the correction of myopia and astigmatism after penetrating keratoplasty.

SETTING

Gazi University, Medical School, Department of Ophthalmology, Ankara, Turkey.

METHODS

Photorefractive keratectomy was performed in 16 eyes of 16 patients with postkeratoplasty myopia and astigmatism who were unable to wear glasses due to anisometropia and were contact lens intolerant. They were examined for uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and corneal transplant integrity before and after surgery.

RESULTS

The mean follow-up after PRK was 26.0 months +/- 15.7 (SD) (range 12 to 63 months). The mean preoperative spherical equivalent refraction of -4.47 +/- 1.39 diopters (D) was -3.39 +/- 1.84 D (P >.05) at the last postoperative visit and the mean preoperative cylinder of -5.62 +/- 2.88 D was -3.23 +/- 1.70 D (P <.05); refractive regression correlated with the amount of ablation performed. The BSCVA decreased in 3 eyes (18.8%), and the UCVA decreased in 2 (12.5%). Six eyes (37.5%) had grade 2 to 3 haze, which resolved spontaneously in 4 eyes within a relatively long time but caused a decrease in BSCVA in 2 (12.5%). Two of the eyes (12.5%) had a rejection episode after PRK and were successfully treated with topical steroids.

CONCLUSIONS

Photorefractive keratectomy to correct postkeratoplasty myopia and astigmatism appears to be less effective and less predictable than PRK for naturally occurring myopia and astigmatism. Corneal haze and refractive regression are more prevalent, and patient satisfaction is not good.

Theoretical analysis of ablation depths and profiles in laser in situ keratomileusis for compound hyperopic and mixed astigmatism

PURPOSE

To compare the theoretical ablation depths and profiles of 4 treatment strategies for compound hyperopic and mixed astigmatism.

SETTING

Theoretical analysis.

METHODS

Corneal contour drawings of theoretical corneal ablation profiles during laser in situ keratomileusis (LASIK) and photoastigmatic refractive keratectomy were made. The depths of tissue ablation in 4 treatment strategies for compound hyperopic astigmatism (Groups 1 to 4) and for mixed astigmatism (Groups 5 to 8) were compared: (1) combined hyperopic spherical and myopic cylindrical treatments (Groups 1 and 5); (2) combined spherical and hyperopic cylindrical treatments (Groups 2 and 6); (3) combined cylindrical treatments (Groups 3 and 7); (4) combined cross-cylinder and spherical equivalent treatments (Groups 4 and 8).

RESULTS

In compound hyperopic astigmatism, the 4 approaches resulted in identical final curvatures, but the ablation depths were greatest in Group 1 (combined hyperopic spherical and myopic cylindrical treatments). The smallest amount of ablation occurred in Group 2 (combined hyperopic spherical and hyperopic cylindrical treatments) and Group 3 (combined hyperopic cylindrical treatments), which had similar tissue ablation patterns. In mixed astigmatism, the greatest ablation depth was in Group 5, followed by Group 8, and Groups 6 and 7. The tissue ablation depths and profiles were similar in Groups 6 and 7.

CONCLUSION

The treatment approaches in Groups 2, 3, 6, and 7 (which avoided the use of minus cylinder) resulted in the smallest degree of stromal ablation. Patients with compound hyperopic or mixed astigmatism may benefit from reduced ablation depths by deferring treatment until hyperopic cylindrical and/or combined cylindrical treatments are available.

Photorefractive keratectomy for compound myopic astigmatism

PURPOSE

To evaluate the safety and efficacy of photorefractive keratectomy for the treatment of primary compound myopic astigmatism.

METHODS

In a prospective study, 93 eyes from 56 patients with a mean spherical equivalent of -4.98 +/- 1.80 diopters (range, -1.75 to -8.5) underwent photoastigmatic refractive keratectomy with the Summit Apex Plus excimer laser using erodible mask technology and were followed for 2 years. Primary outcome measures included an assessment of astigmatic correction through vector analysis, manifest refraction, uncorrected visual acuity, corneal clarity, and the presence of adverse symptoms.

RESULTS

Eighty-five eyes (91.4%) were available for analysis at 6 months. Mean spherical equivalent refraction was reduced 85% (mean, -0.75 +/- 0.85 diopter) and the target-induced astigmatism was reduced 70% (mean, 0.98 +/- 1.88 diopters). Forty-eight eyes (56%) had an uncorrected visual acuity of 20/20 or greater, whereas 70 eyes (82%) had an uncorrected visual acuity of 20/40 or greater. Twenty-four eyes (26% ) required re-treatment because of undercorrection of the spherical equivalent and astigmatic components after the 6-month follow-up. Fifty-nine of the remaining eyes were available at the 24-month visit. Mean spherical equivalent refraction was reduced to -0.39 +/- 0.72 diopter (91.8%). The target-induced astigmatism was reduced 64% from 1.74 diopters. Forty-one eyes (81.3%) were within +/-1.0 diopter of attempted spherical equivalent correction. Stability within a spherical equivalent of +/-0.5 diopter occurred after the first postoperative month. Fifty-six eyes (94.9%) had an uncorrected visual acuity of 20/40 or greater, whereas 34 eyes (57.6 %) demonstrated an uncorrected visual acuity of 20/20 or greater. One eye (1.7%) lost 2 or more lines of best spectacle-corrected visual acuity.

CONCLUSION

Photoastigmatic refractive keratectomy with the Summit Apex Plus excimer laser is a safe and effective method of reducing compound myopic astigmatism. However, higher re-treatment rates may result from significant undercorrections because of current laser algorithms and variability in the mean angle of error.

Photoastigmatic Refractive Keratectomy in Myopes

PURPOSE

Photoastigmatic refractive keratectomy (PARK) was studied in a multi-center clinical trial. The Nidek EC-5000 excimer laser was evaluated for its effect on refraction, visual acuity, and safety measures as part of a U.S. Food and Drug Administration (FDA) regulated study.

METHODS

Eight U.S. centers enrolled adults with eyes having refractive astigmatism up to 4.00 D and a myopic spherical equivalent refraction up to -8.00 D. Results are reported for 749 eyes of 486 patients with at least 6 months follow-up. The rectangular beam scanning Nidek EC-5000 used a 5.5-mm-diameter treatment zone, a 7.0-mm-diameter peripheral blend zone, and a 40 Hz pulse rate for surface treatment of myopic astigmatism. Nomogram corrections to machine settings were required to achieve the desired results.

RESULTS

Preoperative average spherical equivalent refraction of -4.90+/-1.74 D was reduced to -0.02+/-0.79 D at 6 months. Refractive stability was established at 3 months. Over 62% of eyes were within +/-0.50 D of desired correction at 6 months, with over 86% within +/-1.00 D. Uncorrected visual acuity improved by an average of 10 Snellen lines; over 64% of eyes saw 20/20 or better uncorrected and over 93% saw 20/40 or better uncorrected at 6 and 12 months. PARK treatment effectively reduced astigmatism with little average axis error or magnitude error. Corneal haze and safety concerns were minimal.

CONCLUSIONS

Photoastigmatic refractive keratectomy using the Nidek EC-5000 excimer laser provided significant reduction of myopia and astigmatism, with minimal complications.

Surgically induced astigmatism after photorefractive keratectomy with the excimer laser

PURPOSE

To evaluate retrospectively the effect of spherical excimer laser photorefractive keratectomy (PRK) on astigmatism.

METHODS

Four hundred seventy consecutive eyes of patients who had PRK for the treatment of myopia without astigmatic keratotomy, PRK reoperation, or other surgical procedures were evaluated in a retrospective clinical study. PRK was performed using the Summit Apex excimer laser with attempted corrections from 1 to 7 diopters (D) of myopia. Preoperative and postoperative astigmatism was determined by manifest refraction refined with a 0.25-D Jackson cross cylinder and evaluated with vector analysis.

RESULTS

Eighty-five ( 18%) eyes continued to have a spherical refraction after PRK, 53 (11%) eyes had the same preoperative astigmatism, and 332 (71%) eyes had a change in magnitude of astigmatism > or =0.25 D after spherical PRK. The absolute change in astigmatism magnitude irrespective of axis was +0.4 +/- 0.4 (standard deviation) D at 6 months after PRK. Eyes with change in astigmatism power tended to have higher preoperative myopia and higher preoperative astigmatism. Vector analysis revealed surgically induced astigmatism was 0.68 +/- 0.50 D (range, 0-3.25 D) at 1 month and 0.56 +/- 0.47 D (range, 0-3.1 D) at 12 months after spherical PRK.

CONCLUSION

Spherical excimer laser PRK is associated with significant surgically induced astigmatism that is likely related to decentration of the ablation, excimer laser beam irregularities, and variations in wound healing across the ablated zone. Surgically induced astigmatism will complicate attempts to correct astigmatism simultaneously at the time of PRK and suggest that such attempts are likely to be problematic for lower levels of astigmatism.

Arcuate Transverse Keratotomy Remains a Useful Adjunct to Correct Astigmatism in Conjunction With Photorefractive Keratectomy

PURPOSE

To retrospectively evaluate the effectiveness of paired, arcuate transverse keratotomy (Arc-T) performed prior to or after photorefractive keratectomy (PRK) to correct low to moderate amounts of natural or laser-induced astigmatism.

METHODS

Spherical PRK was performed in 730 eyes for myopia of -1.00 to -7.00 D. PRK with arcuate transverse keratotomy was performed in 150 of these eyes; we studied 123 eyes that did not have PRK enhancement. Arc-T was performed prior to PRK in all 37 study eyes with astigmatism of 1.50 D or more at the preoperative examination. Arc-T keratotomy was performed after PRK in 86 study eyes for residual astigmatism of +0.75 D or more and uncorrected visual acuity of 20/30 or worse.

RESULTS

Arc-T before PRK group: PRK was performed at a mean 1.0 +/- 1.5 months after Arc-T. Mean astigmatism decreased from +2.40 +/- 0.6 D (range, 1.00 to 4.00 D) before Arc-T to 0.60 +/- 0.60 D (range, 0 to 2.25 D) after Arc-T (P < .0001). Net change in astigmatism was 1.80 +/- 0.60 D (range, 0.80 to 2.80 D) and mean reduction was 75%. Spherical equivalent refraction changed from -4.10 +/- 1.90 D (range, -0.25 to -8.10 D) to -4.40 +/- 1.80 D after Arc-T (P = .002). Mean change in spherical equivalent refraction after Arc-T was -0.30 +/- 0.50 D (range, -1.10 to +0.40 D). Arc-T after PRK group: Arc-T was performed at a mean 3.5 +/- 1.9 months after PRK. Six months after Arc-T, astigmatism was decreased from +1.50 +/- 0.60 D to 0.40 +/- 0.40 D (P = .04). Net change in astigmatism at 6 months was 1.10 +/- 0.60 D and mean reduction was 74%. Vector change in astigmatism magnitude was 1.30 +/- 0.60 D (range, 0 to 4.00 D) at 6 months and vector change in astigmatism axis was 65 degrees +/- 68 degrees. Spherical equivalent refraction did not change when Arc-T was performed after PRK for eyes with low astigmatism (P = .4). Arc-T retreatment was performed in 6 of 37 (16%) eyes that had Arc-T before PRK and 18 of 86 (21%) eyes that had Arc-T after PRK (P = .12).

CONCLUSION

Arcuate transverse keratotomy performed prior to PRK for high astigmatism or after PRK for lower levels of residual astigmatism effectively improved visual outcome. Coupling was less predictable for high levels of astigmatism correction with Arc-T.

Photorefractive Keratectomy for Visual Rehabilitation of Anisometropia Induced by Retinal Detachment Surgery

PURPOSE

To evaluate the efficacy of unilateral photorefractive keratectomy to correct anisometropia induced by retinal detachment surgery.

METHODS

Photorefractive keratectomy was performed in 10 eyes of 10 patients with anisometropia induced by previous retinal detachment surgery. The Aesculap Meditec MEL 60 excimer laser was used.

RESULTS

Preoperative mean spherical equivalent refraction was -5.20 D. Mean postoperative spherical equivalent refraction was -0.25 D after a mean follow-up of 12.9 months. Mean preoperative spherical equivalent refraction difference between two eyes of 4.87 D was decreased to a mean 0.60 D postoperatively (t-test, P < .0001). All patients were free of anisometropic symptoms after laser surgery.

CONCLUSION

Unilateral photorefractive keratectomy seems to be an effective method to correct anisometropia induced by conventional retinal detachment surgery, especially for patients with spectacle and contact lens intolerance.

Advances in refractive surgery. New options expand the scope of corrective procedures

The Food and Drug Administration's approval of the excimer laser in 1995 heralded the age of laser refractive surgery in the United States. Since then, other advances in refractive surgery have spurred great public interest in and enthusiasm for these procedures. In this article, the authors review the major types of refractive surgery and discuss their indications, results, and complications.

One year clinical results of photoastigmatic refractive keratectomy for compound myopic astigmatism

PURPOSE

To evaluate the efficacy, predictability, and safety of excimer laser photoastigmatic refractive keratectomy (PARK) to correct compound myopic astigmatism.

SETTING

Departments of Ophthalmology, Robert Debré Hospital and Rothschild Foundation, Paris, France.

METHODS

This retrospective study included 27 eyes with compound myopic astigmatism treated with a Nidek EC 5000 excimer laser. The refractive results were measured at 1 year, and the cylindrical component was analyzed by the Alpins method. Mean preoperative myopia was -4.50 diopters (D) (range -0.75 to -4.00 D) and mean preoperative cylinder, -1.64 D (range -0.75 to -4.00 D).

RESULTS

At 1 year, the spherical equivalent was -0.47 D (range +1.00 to -3.00 D) and residual subjective astigmatism, -0.40 (range -0.25 to -1.50 D). Uncorrected visual acuity of 20/40 or better was obtained in 22 of the 27 eyes; 21 eyes were within +/- 1.0 D of emmetropia. Vector analysis showed a mean coefficient adjustment of 1.50 D +/- 0.53 (SD), a mean axis shift of 2.64 +/- 12.10 degrees, and a mean magnitude of error of 0.45 +/- 0.56 D. Haze was absent in 22 eyes and grade 1+ in 5 eyes. Five eyes gained 1 line of best corrected visual acuity and 3 lost 1 line. No patient lost more than 1 line.

CONCLUSION

Excimer laser PARK successfully corrected low and moderate myopia combined with up to 4.0 D of astigmatism with a low mean angle of error. To increase the accuracy of toric ablation, specific algorithms for the cylinder component are needed.

Photorefractive keratectomy for astigmatism greater than -2.00 diopters in eyes with low, high, or extreme myopia

PURPOSE

To assess the efficacy of excimer laser photorefractive astigmatic keratectomy (PARK) in correcting astigmatism of more than -2.00 diopters (D) in eyes with low, high, and extreme myopia.

SETTING

Pusan National University Hospital, Pusan, Korea.

METHODS

Eighty-five patients (110 eyes) whose spherical error ranged from -3.00 to -13.00 D and cylinder ranged from -2.00 to -5.50 D had PARK with a VISX Twenty-Twenty excimer laser; follow-up was 6 months. All cases of myopic astigmatism were treated using the elliptical method and multizone ablation technique. Eyes were divided into 3 groups: low myopia, less than 6.00 D (n = 47); high myopia, from 6.25 to 10.00 D (n = 43); extreme myopia, over 10.25 D (n = 20). Alpins vector analysis was used to calculate the astigmatic change.

RESULTS

By vector analysis, the success rate of astigmatic correction was more predictable in the low and high myopia groups than in the extreme myopia group (P < .05). There was little improvement in astigmatism in the extreme myopia group.

CONCLUSION

Using PARK to correct astigmatism greater than -2.00 D in eyes with myopia less than -10.00 D tended to result in undercorrection; astigmatic correction in eyes with myopia over 10.25 D was minimal.

Prospective comparison of single-zone and multizone laser in situ keratomileusis for the correction of low myopia

OBJECTIVE

This study aimed to determine whether there is a true difference in predictability between single-zone and multizone laser in situ keratomileusis (LASIK) for the correction of low myopia or whether any difference in predictability is because of a need for separate clinical nomograms for the two treatments.

DESIGN

A prospective, randomized, clinical trial.

PARTICIPANTS

Fourteen surgeons and 190 eyes of 95 patients with myopia who desired surgical correction of myopia ranging from -2.00 to -7.00 diopters (D) participated.

INTERVENTION

Fellow eyes of patients with myopia undergoing bilateral simultaneous LASIK were randomized to single-zone and multizone ablation. Astigmatism was not corrected at the time of LASIK.

MAIN OUTCOME MEASURES

Predictability, postoperative videokeratography, and contrast sensitivity were assessed at 3 months after surgery.

RESULTS

At 3 months, r2 values relating laser setting to change in spherical equivalent refraction were 0.78 for single-zone and 0.76 for multizone ablation; mean outcome with respect to intended was -0.84 D (0.65 standard deviation [SD]) for single-zone and -0.62 D (0.78 SD) for multizone eyes (P = 0.035). There was no relationship between single-zone and multizone ablation and the likelihood of asymmetric postoperative videokeratography (P = 0.83). The only difference in contrast sensitivity was a significantly greater decrease in log contrast for multizone eyes at 12 cyc/deg under undilated conditions.

CONCLUSIONS

There is no true difference in predictability between single-zone and multizone LASIK for the correction of low myopia. Separate clinical nomograms for single-zone and multizone LASIK should eliminate the difference in predictability that was observed in this clinical trial.

Excimer laser treatment of myopic astigmatism. A comparison of three ablation programs

OBJECTIVE

The purpose of the study was to evaluate the precision, accuracy, and safety of three different modes of excimer laser surgery for myopic astigmatism.

DESIGN

A prospective interventional case series.

PARTICIPANTS

A total of 150 eyes with compound myopic astigmatism were treated.

INTERVENTION

Ablation programs included the VISX Twenty/Twenty excimer laser using either the sequential mode (58 eyes) or the elliptical mode (54 eyes) and the Technolas-Chiron Keracor 116 hybrid scanning laser (38 eyes).

MAIN OUTCOME MEASURES

Reduction in cylinder and sphere, vector analysis (polar values), uncorrected visual acuity, and best spectacle-corrected visual acuity were evaluated at 1, 6, and 12 months.

RESULTS

By 12 months, sphere was reduced by 95.1%, 87.7%, and 75% in low-astigmatism eyes treated with the VISX sequential, VISX elliptical, and Technolas modes, respectively, and by 92.2%, 98%, and 77.6% in high-astigmatism eyes. By 12 months, cylinder was reduced by 51.5%, 72.2%, and 36.3% in low-astigmatism eyes and by 70%, 78%, and 45.6%, respectively, in high-astigmatism eyes. Vector analysis showed that the elliptical treatment produced more significant reductions in mean polar values than the other two treatments at various timepoints.

CONCLUSION

These results suggest that the ablation approach may influence the clinical result.

Paradoxical response to photorefractive treatment for postkeratoplasty astigmatism

A 42-year-old woman with functionally disabling postkeratoplasty astigmatism in her right eye 3 years after corneal transplantation for keratoconus received photorefractive keratectomy for high astigmatism in that eye. This did not reduce her astigmatism. The procedure was repeated and corneal astigmatism paradoxically increased. The forces within the pseudo-optical ring that cause and maintain astigmatism in corneal transplants may be a significant factor in the unpredictable response of some corneal transplants to excimer photorefractive astigmatism correction.

Excimer laser correction of astigmatism with multipass/multizone treatment. The Melbourne Excimer Laser Group

PURPOSE

To evaluate the accuracy of excimer laser correction of myopic astigmatism by multipass/multizone photoastigmatic refractive keratectomy (PARK).

SETTING

Tertiary referral ophthalmic hospital with an associated private laser facility.

METHODS

This study comprised a consecutive series of 332 eyes of 289 patients who were followed for 6 months. All patients were 18 years or older, had stable myopic astigmatism (up to a -19.0 diopters [D] spherical equivalent [SE] at the spectacle plane), and had a best corrected visual acuity of at least 20/60 in both eyes. All eyes were treated with a VISX Twenty-Twenty excimer laser. The correction was divided between ablation zones using a multipass/multizone treatment paradigm based on the amount of myopia and astigmatism. Patients were examined 1 week, and 1, 3, and 6 months after surgery.

RESULTS

Analysis of the mean percentage of spherical correction across the range of myopic preoperative SEs treated demonstrated 90% correction for most amounts of myopic astigmatism. Eyes with low myopia (mean preoperative SE < or = -5.0 D) treated with < or = -1.0 diopter cylinder (DC) of astigmatism achieved a mean percentage of spherical correction of 91% versus 93% in eyes with high myopia (> -5.0 D mean preoperative SE). Eyes with low myopia treated with > -1.0 DC of astigmatism achieved a mean percentage spherical correction of 90% versus 89% in eyes with high myopia. The differences between the two groups were not statistically significant. Patients with high relative cylinder (> 80% of total sphere treated) achieved comparable results. Analysis of the astigmatic component of the treatment, independent of the spherical result, showed a trend toward overcorrection in the high myopia group with less than -1.0 DC and a mean astigmatic correction of 89 and 98%, respectively, in the low and high myopic astigmatism groups. The mean angle of error was +2.0 degrees.

CONCLUSION

Multipass/multizone PARK for myopic astigmatism demonstrated a high degree of predictability and stability with desirable results for low and high levels of astigmatism across the range of myopic astigmatism treated by surface ablation.

Excimer laser photoastigmatic refractive keratectomy: eighteen-month follow-up

OBJECTIVE

To study the efficacy of photoastigmatic refractive keratectomy (PARK) by the MEL 60 (Aesculap-Meditec, Jana, Germany) scanning excimer laser for the treatment of myopic astigmatism, with follow-up of 18 months.

PATIENTS AND METHODS

One hundred and twenty-eight eyes of 102 patients with different degrees of myopic astigmatism were treated by PARK and followed prospectively in an open study. Ablations were performed with an MEL 60 excimer laser using an astigmatic module.

RESULTS

Mean preoperative refractive cylinder improved from a preoperative value of -1.8 +/- 0.8 diopters (D; range, -1.0 to -6.0 D) to -0.3 +/- 0.5 D (range, +1.0 to -2.5 D) at 18 months. The mean reduction in cylindrical correction alone was 84 +/- 37% in the low astigmatism group (-1.0 to -1.5 D); 91 +/- 21% in the moderate astigmatism group (-1.75 to -2.5 D); and 75 +/- 25% in the high astigmatism group (-2.75 to -6.0 D). One hundred and three eyes (80%) at 12 months and 100 eyes (85%) at 18 months were within +/-0.5 D of the intended astigmatic correction, with more eyes in the low astigmatic group. One hundred and nineteen eyes (93%) and 114 eyes (97%) at 12 and 18 months, respectively, were within +/-1.0 D of the intended correction. Ninety-two percent to 95.7% of the eyes in the different groups had a postoperative axis less than 10 degrees of the preoperative and intended axis at 12 and 18 months after PARK. Uncorrected visual acuity (UCVA) of 20/40 or better was achieved in nearly 84% of the eyes 12 and 18 months after PARK. A UCVA of 20/20 was achieved in 49% of eyes 18 months after PARK. Ten eyes (8%) underwent reoperation at the end of 12 months.

CONCLUSIONS

The data indicate that PARK is an effective surgical tool for correcting astigmatism, especially astigmatism of 1.0 to -2.5 D, with a success rate of approximately 70%.

Laser in situ keratomileusis assisted by corneal topography

PURPOSE

To assess whether laser in situ keratomileusis (LASIK) assisted by corneal topography can successfully treat corneal irregularities or irregular astigmatism in patients with previous ocular surgery or ocular trauma.

SETTING

University Eye Hospital, Klinikum Mannheim, Mannheim, Germany.

METHODS

In a prospective clinical study, LASIK was performed in 23 eyes of 22 patients. Reasons for surgery were irregular astigmatism after penetrating keratoplasty or penetrating injury or corneal irregularity after previous excimer laser surgery. Excimer ablation was based on preoperative corneal topography data (Corneal Analysis System, EyeSys Technologies) using a proprietary algorithm (Topographic Assist LASIK, Chiron Vision). Follow-up was 6 months.

RESULTS

Mean preoperative uncorrected visual acuity (UCVA) was 20/80 and mean best spectacle-corrected visual acuity (BSCVA), 20/35. Uncorrected visual acuity improved in all but two cases. Postoperatively, mean UCVA increased to 20/50; mean BSCVA was unchanged. No eye lost two or more lines of BSCVA. Postoperative topography showed less corneal irregularity in 81.3% of eyes; full correction was achieved in 19.4%. Four eyes (19.4%) needed re-treatment for undercorrection and three eyes (14.3%) for regression.

CONCLUSION

Preliminary results indicate that the concept of topographic-assisted LASIK is feasible. However, most eyes were undercorrected and had regression. One reason might be that corneal topography underestimated corneal irregularity, causing significant undercorrection.

Treatment of myopic astigmatism with the Summit Apex Plus excimer laser

PURPOSE

To assess the results of surface sequential toric photorefractive keratectomy (PRK) with the Summit Apex Plus excimer laser using an erodible mask.

METHODS

A prospective study was performed on consecutive eyes having surface sequential toric PRK over a 4 month treatment period. Attempted astigmatism correction varied from 70 to 100%, depending on the power and axis of the cylinder. The myopic correction was adjusted so the combined treatment aim was emmetropia. Refraction, manual keratometry, corneal haze, and visual acuity data from preoperative and follow-up visits over 12 months were divided into various groups based on the preoperative refraction and analyzed.

RESULTS

Fifty-nine eyes from 48 patients had sequential toric PRK. Preoperatively, the mean spherical equivalent at glasses plane (SEGP) was -4.88 diopters (D) +/- 3.20 (SD) and the mean refractive cylinder, 2.02 +/- 1.04 D. The mean attempted cylinder correction was 1.87 D. At 12 months the mean SEGP was -0.02 +/- 0.67 D, which was not statistically significant from plano. The mean refractive cylinder was 0.84 +/- 0.84 D, which was statistically significantly different from zero cylinder power. There was a statistically significant correlation between the preoperative and the 12 month postoperative refractive cylinder powers. At 12 months, 34 of 43 eyes (79.1%) had an uncorrected visual acuity of 6/12 or better. While 2 eyes in one patient (4.7%) lost two lines of best corrected visual acuity, with a final acuity of 6/12 in each, no patient lost more than two lines.

CONCLUSION

The manifest refraction cylinder power is not fully corrected with the current treatment algorithms; however, surface sequential toric PRK using an erodible mask is capable of treating compound myopic astigmatism with moderate success.

Excimer laser photorefractive keratectomy for low hyperopia: safety and efficacy

PURPOSE

To assess the safety and efficacy of photorefractive keratectomy (PRK) to correct low hyperopia.

SETTING

University of Ottawa Eye Institute, Ottawa General Hospital, Ontario, Canada.

METHODS

Twenty-five eyes with refractions of +1.00 to +4.00 diopters (D) and cylinder of 1.00 D or less were treated for hyperopia with the VISX Star excimer laser system using a refined ablation architecture. Thorough visual assessments were performed preoperatively (baseline) and 1, 3, and 6 months postoperatively. Complications were recorded and the level of patient satisfaction was noted.

RESULTS

Mean spherical equivalent at 6 months was +0.27 D +/- 0.55 (SD), which was an 89% reduction over baseline. Eighty-four percent of patients gained two to seven lines of near uncorrected visual acuity (UCVA) and 1 patient (4%) lost more than one line. Eight percent achieved 20/25 or better UCVA. Approximately half realized their preoperative distance best corrected visual acuity (BCVA) by 1 month. By the end of the study, all patients had improved, achieved, or were within one line of their baseline distance BCVA. There were some slight reductions in lower contrast acuity at 6 months, although dim lighting conditions did not further reduce these acuities. Most patients had no clinically meaningful change in cylinder. The most common complications included early, transient corneal surface irregularities and visual symptoms and trace haze (grade < or = 0.5) in 14 of 23 patients at 6 months. All but 1 patient expressed a high degree of satisfaction.

CONCLUSIONS

These results support the hypothesis that PRK shows great promise as a safe and effective treatment for low hyperopia. There were no significant complications and no decentered ablations. The slight regression occurred with or without the presence of trace haze. Overall, refractive stability was encouraging, although longer follow-up is needed.

Photoastigmatic Refractive Keratectomy for Compound Myopic Astigmatism with a Nidek Laser

BACKGROUND

With advances in the delivery of excimer laser energy to the cornea, spherocylindrical ablations are now possible. The refractive and visual outcome of eyes undergoing photoastigmatic refractive keratectomy with a minimum of 12 months follow-up are presented.

METHODS

A retrospective analysis of 160 consecutive eyes that underwent photoastigmatic refractive keratectomy using the Nidek EC5000 excimer laser was undertaken. One year follow-up data were available on 89 eyes. Vector analysis of the change in cylindrical error, by the Alpins method, was performed. Before surgery, the mean spherical equivalent refraction was -5.68 diopters (D) (SD 2.67 D) with a mean cylinder power of -1.40 D (SD 0.75).

RESULTS

At 1 year after surgery, the mean spherical equivalent was -0.44 D (SD 0.87). Seventy-one eyes (79.8%) had a spherical equivalent within 1.00 D of the target refraction and 79 eyes (89%) achieved 6/12 or better, unaided. Four of 89 eyes (4.5%) lost more than two lines of spectacle-corrected visual acuity with 9 eyes (10%) gaining Snellen acuity, comparing preoperative spectacle-corrected acuity with postoperative uncorrected visual acuity. The mean coefficient of adjustment (targeted induced astigmatism vector magnitude divided by surgically induced astigmatism vector magnitude) was 1.11 (SD 1.33), indicating undercorrection of the cylinder. The mean angle of error was 0.73 degree (+/- 10.91).

CONCLUSIONS

Refractive visual acuity outcome after photoastigmatic refractive keratectomy was good. Current algorithms undercorrect the cylinder power, but are adequately aligned. Algorithms for toric ablations in the Nidek EC5000 need to be improved.