Comparison of Wavefront-guided Customized Ablation vs. Conventional Ablation in Laser in situ Keratomileusis

Recent advances in measurement of monochromatic aberrations of human eyes

The field of aberrations of the human eye is moving rapidly, being driven by the desire to monitor and optimise vision following refractive surgery. It is important for ophthalmologists and optometrists to have an understanding of the magnitude of various aberrations and how these are likely to be affected by refractive surgery and other corrections. In this paper, I consider methods used to measure aberrations, the magnitude of aberrations in general populations and how these are affected by various factors (for example, age, refractive error, accommodation and refractive surgery) and how aberrations and their correction affect spatial visual performance.

Two-years results of small-incision lenticule extraction and wavefront-guided laser in situ keratomileusis for Myopia

PURPOSE

To compare the 2-years visual and refractive outcomes between small-incision lenticule extraction (SMILE) and wavefront-guided laser in situ keratomileusis (LASIK) in eyes with myopia and myopic astigmatism.

METHODS

Our retrospective case-control study examined 30 eyes of 30 patients with the manifest refraction spherical equivalent (MRSE) of -3.71 ± 1.83 dioptres (D) who underwent SMILE and 30 eyes of 30 patients with MRSE of -3.81 ± 1.40 D who underwent wavefront-guided LASIK. We assessed the 2-years clinical outcomes.

RESULTS

Logarithm of the minimal angle of resolution (LogMAR)-corrected distance visual acuity (CDVA) was -0.23 ± 0.07 in the SMILE group and -0.24 ± 0.07 in the wavefront-guided LASIK group 2 years postoperatively (p = 0.82). Logarithm of the minimal angle of resolution-uncorrected distance visual acuity (UDVA) was -0.18 ± 0.09 and -0.15 ± 0.11 (p = 0.30, respectively). In the SMILE and wavefront-guided LASIK groups 2 years postoperatively, 100% and 73% of eyes, respectively, were within 0.5 D of the prompted MRSE correction (p = 0.005). Changes in the MRSE of -0.10 ± 0.30 D and -0.23 ± 0.51 D occurred from 3 months to 2 years (p = 0.40, respectively). We found a significant correlation between myopic regression and the changes in the keratometric readings from 3 months to 2 years after wavefront-guided LASIK (r = -0.48, p = 0.002), but not after SMILE (r = -0.004, p = 0.90).

CONCLUSION

Small-incision lenticule extraction offers better refractive outcomes than wavefront-guided LASIK during a 2-years follow-up for the correction of myopia and myopic astigmatism.

Comparison of astigmatic correction after femtosecond lenticule extraction and wavefront-guided LASIK for myopic astigmatism

PURPOSE

To compare postoperative astigmatic correction between femtosecond lenticule extraction (FLEx) and wavefront-guided LASIK in eyes with myopic astigmatism.

METHODS

Fifty-eight eyes of 41 patients undergoing FLEx and 49 eyes of 29 patients undergoing wavefront-guided LASIK to correct myopic astigmatism were examined. Visual acuity, cylindrical refraction, predictability of the astigmatic correction, and astigmatic vector components were compared between groups 6 months after surgery.

RESULTS

There was no statistically significant difference in manifest cylindrical refraction (P = .08) or percentage of eyes within ± 0.50 diopter (D) of its refraction (P = .11) between the surgical procedures. The index of success in FLEx was statistically significantly better than that of wavefront-guided LASIK (P = .02), although there was no significant difference between the groups in other indices (eg, surgically induced astigmatism, target-induced astigmatism, astigmatic correction index, angle of error, difference vector, and flattening index). Subgroup analysis showed that FLEx had a better index of success (P = .02) and difference vector (P = .04) than wavefront-guided LASIK in the low cylinder subgroup; the angle of error in FLEx was significantly smaller than that of wavefront-guided LASIK in the moderate cylinder subgroup (P = .03).

CONCLUSIONS

Both FLEx and wavefront-guided LASIK worked well for the correction of myopic astigmatism by the 6-month follow-up visit. Although FLEx had a better index of success than wavefront-guided LASIK when using vector analysis, it appears equivalent to wavefront-guided LASIK in terms of visual acuity and the correction of astigmatism.

Wavefront-guided versus non-wavefront-guided photorefractive keratectomy for myopia: meta-analysis of randomized controlled trials

Purpose

To compare the efficacy, predictability, safety, and induced higher-order aberrations (HOAs) between wavefront-guided and non-wavefront-guided photorefractive keratectomy (PRK).

Methods

The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for randomized controlled trials. Trials meeting the selection criteria were quality appraised, and data was extracted by 2 independent authors. Measures of association were pooled quantitatively using meta-analytical methods. Comparisons between wavefront-guided and non-wavefront-guided ablations were made as pooled odds ratios (ORs) or weighted mean differences. The pooled ORs and 95% confidence intervals (CIs) were computed for efficacy, safety, and predictability. The weighted mean differences and 95% CIs were used to compare induced HOAs.

Results

The study covered five trials involving 298 eyes. After wavefront-guided PRK, the pooled OR of achieving an uncorrected distance visual acuity of 20/20 (efficacy) was 1.18 (95% CI, 0.53–2.60; p = 0.69), the pooled OR of achieving a result within ±0.50 diopter of the intended target (predictability) was 0.86 (95% CI, 0.40–1.84; p = 0.70). No study reported a loss of 2 or more lines of Snellen acuity (safety) with either modality. In eyes with wavefront-guided PRK, the postoperative trefoil aberrations (mean difference −0.02; 95% CI, −0.03 to −0.00; p = 0.03) were significantly lower. There were no significant differences between the two groups in the postoperative total HOAs (mean difference −0.04; 95% CI, −0.23 to 0.14; p = 0.63), spherical (mean difference 0.00; 95% CI, −0.08 to 0.09; p = 0.93), and coma (mean difference −0.06; 95% CI, −0.14 to 0.03; p = 0.20) aberrations.

Conclusions

According to the meta-analysis, wavefront-guided PRK offered no advantage in efficacy, predictability, or safety measures over non-wavefront-guided PRK, although it may have induced fewer trefoil aberrations.

Visual performance after posterior chamber phakic intraocular lens implantation and wavefront-guided laser in situ keratomileusis for low to moderate myopia

PURPOSE

To compare postoperative visual function after implantable collamer lens (ICL) implantation and after wavefront-guided laser in situ keratomileusis (LASIK) in eyes with low to moderate myopia.

DESIGN

Retrospective observational case study.

PATIENTS AND METHODS

We investigated 30 eyes of 20 patients undergoing ICL implantation and 64 eyes of 38 patients undergoing wavefront-guided LASIK for the correction of low to moderate myopia (manifest spherical equivalent: -3.00 to -5.88 diopters [D]). Ocular higher-order aberrations (HOAs) and contrast sensitivity (CS) function were measured by Hartmann-Shack aberrometry and a contrast sensitivity unit before and 3 months after surgery, respectively. From the contrast sensitivity, the area under the log contrast sensitivity function was calculated.

RESULTS

For 4-mm and 6-mm pupils, the changes in ocular third-order aberrations, fourth-order aberrations, and total HOAs after ICL implantation were significantly less than those after wavefront-guided LASIK (P < .05, Mann-Whitney U test). The postoperative area under the log contrast sensitivity function was significantly increased after ICL implantation (P < .001), whereas, after wavefront-guided LASIK, it was not significantly changed (P = .11).

CONCLUSIONS

ICL implantation induces significantly fewer ocular HOAs than wavefront-guided LASIK. Moreover, CS was significantly improved after ICL implantation but unchanged after wavefront-guided LASIK in eyes with low to moderate myopia. Thus, even in the correction of low to moderate myopia, ICL implantation appears to be superior in visual performance to wavefront-guided LASIK, suggesting that it may be a viable surgical option for the treatment of such eyes.

Prospective contralateral eye study to compare conventional and wavefront-guided laser in situ keratomileusis

PURPOSE

To compare outcomes of customized/wavefront guided with conventional ablation in myopic patients with or without astigmatism undergoing laser in situ keratomileusis.

METHODS

A prospective, comparative, contralateral eye study was performed. Sixty-eight eyes of 34 myopic patients with similar refractive error in both eyes were included. One eye was randomly selected to undergo conventional and the fellow eye customized ablation. Surgery was performed using the Technolas 217z laser (Bausch & Lomb, Surrey, UK). Uncorrected visual acuity, manifest refractive spherical equivalent (MRSE), astigmatism, aberrometry and contrast sensitivity were recorded pre and 3 months postoperatively.

RESULTS

Mean MRSE treated in the conventional and customized groups were 3.77 ± 1.61 dioptres and -3.83 ± 1.59 dioptres respectively. Three months postoperatively there was no significant difference between the groups in mean MRSE (p = 0.99) or cylinder (p = 0.56). The factor increase in postoperative total higher order aberrations (HOAs) was less in the customized (1.32) compared with the conventional (1.54) treatment group but did not reach statistical significance (p = 0.08). Scotopic contrast sensitivity decreased significantly postoperatively in the conventional but not in the customized treatment group.

CONCLUSION

Visual acuity and refractive error outcomes were similar in both treatment group and no patient preference was observed. Customized ablation was associated with a smaller but not statistically significant postoperative increase in HOAs, better preservation of scotopic contrast sensitivity, quicker treatment time and removal of less corneal tissue.

Efficacy, predictability, and safety of wavefront-guided refractive laser treatment: metaanalysis

PURPOSE

To compare the efficacy, predictability, safety, and induced higher-order aberrations (HOAs) between wavefront-guided and non-wavefront-guided ablations.

SETTING

Division of Ophthalmology and Visual Sciences, University of Nottingham, Nottingham, United Kingdom.

DESIGN

Metaanalysis.

METHODS

The Cochrane Central Register of Controlled Trials, PubMED, and EMBASE were searched for randomized controlled trails. Trials meeting the selection criteria were quality appraised and data extracted by 2 independent authors. Measures of association were pooled quantitatively using metaanalytical methods. Comparison between wavefront-guided and non-wavefront-guided ablations was measured as pooled odds ratios (ORs) or weighted mean differences. The pooled ORs and 95% confidence intervals (CIs) were computed for efficacy, safety, and predictability. The weighted mean difference and 95% CIs were used to compare induced HOAs.

RESULTS

Eight trials involving 955 eyes were included. After wavefront-guided LASIK, the pooled OR of achieving uncorrected distance visual acuity (UDVA) of 20/20 (efficacy) was 1.10 (95% CI, 0.66-1.83; P=.72), the pooled OR of achieving a result within ± 0.50 diopter of intended target (predictability) was 1.03 (95% CI, 0.60-1.75; P=.92), and the weighted mean difference in induced HOAs was -0.09 (95% CI, -0.17 to -0.01; P=.04). No study reported loss of 2 or more lines of Snellen acuity (safety) with either modality.

CONCLUSIONS

Metaanalysis showed no clear evidence of a benefit of wavefront-guided over non-wavefront-guided ablations. However, there was a lack of standardized reporting of UDVA better than 20/20, which might mask an advantage in wavefront-guided treatment. With high preexisting HOAs, wavefront-guided has advantages over non-wavefront-guided treatment.

Factors influencing the changes in coma-like aberrations after myopic laser in situ keratomileusis

PURPOSE

To assess factors affecting changes in coma-like aberrations after myopic laser in situ keratomileusis (LASIK).

METHODS

We retrospectively examined 91 eyes of 48 patients undergoing LASIK (mean patient age ± standard deviation, 29.6 ± 8.1 years; gender, 29 male and 19 female; manifest refraction, -4.76 ± 1.42 diopters). We quantitatively assessed the values of coma-like aberrations for 4-mm and 6-mm pupils using a Hartmann-Shack aberrometer before and 3 months after surgery. Multiple regression analysis was used to assess the relevant factors of the changes in coma-like aberrations.

RESULTS

The mean changes in coma-like aberrations for 4-mm and 6-mm pupils were 0.08 ± 0.09 μm and 0.31 ± 0.30 μm, respectively. Explanatory variables relevant to the changes in coma-like aberrations were, in order of influence, amount of spherical equivalent correction (partial regression coefficient B = 0.022, p <0.001 for a 4-mm pupil, B = 0.090, p <0.001 for a 6-mm pupil), and surgical technique (B = -0.062, p = 0.01 for a 4-mm pupil, B = -0.169, p = 0.03 for a 6-mm pupil). No significant correlation was seen with other clinical factors such as age, gender, astigmatism correction, mean keratometric readings, central corneal thickness, or eye tracking (with or without).

CONCLUSIONS

High myopic eyes requiring larger amounts of laser correction and eyes undergoing conventional LASIK tend to induce more coma-like aberration after surgery. Wavefront-guided LASIK may be a better surgical approach for preventing the induction of coma-like aberrations, especially in eyes with high myopia.

Wavefront-optimized ablation versus topography-guided customized ablation in myopic LASIK: comparative study of higher order aberrations

BACKGROUND AND OBJECTIVE

To compare the outcomes of wavefront-optimized ablation and topography-guided ablation in fellow eyes of patients undergoing laser in situ keratomileusis (LASIK) for myopia.

PATIENTS AND METHODS

This prospective study included 84 patients who underwent LASIK in both eyes: wavefront-optimized ablation in one eye (group I) and topography-guided ablation in the fellow eye (group II). The Moria2 microkeratome with a 110 single-use head (Moria, Antony, France) was used to create a superior hinged flap and the Allegretto Wave Excimer Laser (Alcon/Wavelight Light Laser Technologie GmbH, Erlangen, Germany) for photoablation. The Allegretto wave analyzer was used to measure the ocular aberrations before and 6 months after LASIK. Refractive visual outcomes and ocular aberration changes were compared between the two treatment modalities.

RESULTS

Six months postoperatively, the mean uncorrected visual acuity of group II was statistically better than that of group I (P = .02). Seventy percent of group I and 83% of group II achieved a postoperative spherical equivalent refraction of ±0.5 diopters. The postoperative total root-mean-square of higher order aberrations (HOAs) of group II was smaller than that of group I, but the difference was not statistically significant (P = .51). There was a decrease in most of the individual terms of HOAs in group II, but it was only statistically significant in Z(3) (-1) (P = .04). The reverse occurred in group I, where most of the individual terms of HOAs increased, but it was not statistically significant. Significant improvement was only noted in Z(5) (3) (P = .05) and Z(5) (5) (P = .04).

CONCLUSION

Both wavefront-optimized ablation and topography-guided ablation provided good refractive results, but the latter induced fewer HOAs.

Changes in wave-front aberrations after rigid gas permeable contact lens fitting in post-laser in situ keratomileusis patients with visual complaints

OBJECTIVE

To evaluate the effect of rigid gas permeable (RGP) contact lenses in reducing wave-front aberrations in post-laser in situ keratomileusis (LASIK) myopic patients.

DESIGN

Cross-sectional study.

PARTICIPANTS

Thirty patients with visual complaints after conventional LASIK procedure for correcting myopia.

METHODS

The 30 patients were fitted with RGP contact lenses. Wave-front measurements were taken before and after RGP contact lens wearing.

RESULTS

Compared with bare eye examinations, root mean-square values of higher-order aberrations (HOAs) significantly decreased with RGP contact lens use. Among these, spherical aberration decreased from 0.507 (SD 0.304) microm to 0.164 (SD 0.121) microm (t = 7.186, p < 0.001); coma decreased from 0.470 (SD 0.312) microm to 0.165 (SD 0.090) microm (t = 5.566, p < 0.001); secondary coma decreased from 0.079 (SD 0.050) microm to 0.044 (SD 0.027) m (t = 4.118, p < 0.001); and total HOAs decreased from 0.782 (SD 0.449) microm to 0.307 (SD 0.140) microm (t = 6.710, p < 0.001).

CONCLUSIONS

Fitting RGP contact lenses effectively decreased HOAs induced by conventional myopic LASIK surgery. Possible reasons may be the elimination of irregularity and dissymmetry on the corneal anterior surface, relief of the aspherical extent of the central corneal surface, and enlargement of the effective optical zone.

Conventional versus custom ablation in photorefractive keratectomy: randomized clinical trial

PURPOSE

To compare visual outcomes and changes in total higher-order aberrations (HOAs) between conventional photorefractive keratectomy (PRK) and custom PRK SETTING: Department of Ophthalmology, Labbafinejad Medical Center, Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences and Negah Eye Center, Tehran, Iran.

METHODS

This clinical trial comprised eyes having bilateral myopic PRK with the Technolas 217z excimer machine. One eye had conventional ablation (conventional group) and the other eye, wavefront-guided custom treatment (custom group). Changes in postoperative visual acuity, cycloplegic refraction, contrast sensitivity function, and root mean square higher-order aberrations (RMS HOAs) were compared between the 2 groups.

RESULTS

The mean age of the 28 patients (56 eyes) was 26.7 years. The mean preoperative cycloplegic spherical equivalent refractive error was -4.92 diopters (D) +/- 1.6 (SD) and the mean refractive astigmatism, 0.91 +/- 1.0 D. There was no statistically significant difference between the 2 groups in preoperative cycloplegic refractive error, HOAs, or contrast sensitivity function. The mean follow-up was 8.1 +/- 3.3 months. The increase in RMS HOAs from preoperatively to postoperatively was statistically significantly higher in the custom group in the 6.0 mm zone (P = .03) but not in the 4.0 mm zone (P = .26). The decrease in low mesopic contrast sensitivity function was statistically significant in both groups.

CONCLUSIONS

The RMS HOAs significantly increased after PRK with both methods. The results suggest that custom ablation is more sensitive to optical zone (OZ) size and may yield more aberrations with an OZ smaller than 6.0 mm.

Reverse geometry rigid gas permeable contact lens wear reduces high-order aberrations and the associated symptoms in post-LASIK patients

PURPOSE

This study evaluated the efficacy of custom-made reverse geometry rigid gas permeable (RGP) contact lenses in the control of symptoms related to increased wavefront aberrations after LASIK correction of myopia.

MATERIALS AND METHODS

Twenty-eight myopes treated with LASIK were assessed for post-LASIK symptoms (declined night vision, glare, halos and/or monocular diplopia) and corneal topography. A set of RGP contact lenses was selected as trial lenses based on the matching between the lens and the patient's corneal topography. If the fluorescein pattern between the trial lens and the corneal surface showed a central alignment, a mid-peripheral bearing and peripheral clearance and if the patient felt comfortable with the lens wear, a duplicated lens was ordered for the patient. Otherwise, a lens satisfied with corneal topography of the patient and clinical judgment was used. Visual acuity (VA) and wavefront aberrations were measured after the lens wear.

RESULTS

The custom-made lenses well matched the host cornea with no dislodgment in all subjects. The post-LASIK eyes showed an increase of 1 Snellen line in VA (from 0.90 +/- 0.33 to 1.11 +/- 0.24) and a significant improvement in all symptoms after the lens wear. The total higher-order aberration is significantly reduced after the lens wear with at least 70% reduction in either spherical aberration, coma, third or fourth aberration but only 33% reduction in the fifth aberration.

CONCLUSIONS

Reverse geometry RGP lenses with the design based on individual topographic data can improve visual performance of post-LASIK eyes by reducing higher order aberrations.

Effects of decentration of photorefractive keratectomy on the induction of higher order wavefront aberrations

PURPOSE

To evaluate the effects of ablation decentration on the induction of higher order wavefront aberrations (HOAs) in active eye-tracker-assisted myopic photorefractive keratectomy (PRK) using the VISX STAR S4 laser with ActiveTrak (Abbott Medical Optics [AMO]).

METHODS

Ninety-four myopic eyes (53 patients) were divided into three groups according to ablation decentration (group 1, ≤0.15 mm, 20 eyes; group 2, >0.15 to ≤0.30 mm, 54 eyes; and group 3, >0.30 mm, 20 eyes). The distances of ablation centers from the centers of the entrance pupils were analyzed using corneal topography. Wavefront errors were measured preoperatively and at 6 months after PRK using a VISX WaveScan aberrometer (AMO). Statistical analysis was performed to assess the influence of ablation decentration on PRK-induced HOAs.

RESULTS

The mean decentration was 0.23±0.10 mm (range: 0.04 to 0.52 7 mm). The magnitude of all HOAs was significantly increased at 6 months postoperatively (P<.05). Increases in PRK-induced HOAs including total HOA, coma, and spherical aberration were significantly different among the three groups (P<.05). Statistically significant differences were noted between pairs of data in group 1 versus group 3 for total HOA (P=.015), coma (P=.038), and spherical aberration (P=.038), and group 2 versus group 3 for coma (P=.049).

CONCLUSIONS

Ablation decentration >0.30 mm from the center of the entrance pupil was associated with greater induction of total HOA, coma, and spherical aberration after PRK, as compared with ablation decentration <0.15 mm. In addition, ablation decentration has a more significant influence on coma-inducing effects.

Visual performance after implantable collamer lens implantation and wavefront-guided laser in situ keratomileusis for high myopia

PURPOSE

To compare postoperative visual function after implantable collamer lens (ICL; STAAR Surgical, Nidau, Switzerland) implantation and after wavefront-guided laser in situ keratomileusis (WFG-LASIK) in eyes with high myopia.

DESIGN

Retrospective, observational case study.

METHODS

We investigated 46 eyes of 33 patients undergoing ICL implantation and 47 eyes of 29 patients undergoing WFG-LASIK (Technolas217z; Bausch & Lomb, Rochester, New York, USA) for the correction of high myopia (manifest spherical equivalent < or = -6 diopters). Ocular higher-order aberrations (HOA) and contrast sensitivity (CS) function were measured by Hartmann-Shack aberrometry (KR-9000; Topcon, Tokyo, Japan) and a CS unit (VCTS-6500; Vistech Consultants Inc, Dayton, Ohio, USA) before and 3 months after surgery, respectively. From the CS, the area under the log CS function (AULCSF) was calculated.

RESULTS

For a 4-mm pupil, the changes in ocular coma-like aberrations, spherical-like aberrations, and total HOAs after ICL implantation were significantly less than those after WFG-LASIK (P < .001, Mann-Whitney U test). The postoperative AULCSF was significantly increased after ICL implantation (P < .001), whereas after WFG-LASIK, it was significantly decreased (P < .001).

CONCLUSIONS

ICL implantation induces significantly fewer ocular HOAs than WFG-LASIK. Moreover, CS was improved significantly after ICL implantation, but deteriorated after WFG-LASIK in eyes with high myopia. Thus, in the correction of high myopia, ICL implantation seems to be superior in visual performance to WFG-LASIK, suggesting that it may be a better surgical option for the treatment of such eyes.

The changes of posterior corneal surface and high-order aberrations after refractive surgery in moderate myopia

Purpose

To compare forward shift of posterior corneal surface and higher-order aberration (HOA) changes after LASIK, LASEK, and wavefront-guided LASEK surgery in moderate myopia

Methods

One hundred eighty four eyes undergoing LASIK, LASEK and wavefront-guided LASEK with VISX STAR S4 were included in this study. The posterior corneal elevation was measured with Orbscan before, 2 and 4 months after surgery. Changes of the elevation were assessed using the difference map generated from preoperative and postoperative elevation maps. The values of higher-order aberrations were evaluated preoperatively and 2 months postoperatively with Wavefront aberrometer.

Results

The posterior corneal surface displayed forward shift of 27.2±11.45 µm, 24.3±9.76 µm in LASIK group, 23.4±10.5 µm, 23.6±10.55 µm in LASEK group, 24.0±14.95 µm, 28.4±14.72 µm in wavefront-guided LASEK group at 2 months and 4 months, respectively. There were no statistically significant differences among those three groups, and between 2 and 4 months. The root mean score (RMS) of HOA was increased after LASIK and LASEK (p=0.000, p=0.000, respectively). The mean change of HOA-RMS was significantly smaller in wavefront-guided LASEK than LASIK or LASEK (p=0.000, p=0.000, respectively, Bonferroni-corrected).

Conclusions

The changes of posterior corneal surface forward shift showed no difference among LASIK, LASEK and wavefront-guided LASEK in moderate myopia. HOAs were significantly increased after LASIK and LASEK. The changes of HOAs were significant smaller in wavefront-guided LASEK than LASIK or LASEK.

Changes in higher order aberrations after wavefront-guided PRK for correction of low to moderate myopia and myopic astigmatism: two-year follow-up

PURPOSE

To assess efficacy, safety, and changes in higher order aberrations after wavefront-guided photorefractive keratectomy (PRK) in comparison with conventional PRK for low to moderate myopia with myopic astigmatism using a WASCA Workstation with the MEL 70 G-Scan excimer laser.

METHODS

A total of 126 myopic or myopic-astigmatic eyes of 112 patients were included in this retrospective study. Patients were divided into two groups: Group 1, the study group; and Group 2, the control group. Group 1 consisted of 78 eyes treated with wavefront-guided PRK. Group 2 consisted of 48 eyes treated with spherocylindrical conventional PRK.

RESULTS

Two years postoperatively, in Group 1, 5% of eyes achieved an uncorrected visual acuity (UCVA) of 0.05; 69% achieved a UCVA of 0.00; 18% of eyes experienced enhanced visual acuity of -0.18 and 8% of -0.30. In Group 2, 8% of eyes achieved a UCVA of 0.1; 25% achieved a UCVA of 0.05; and 67% achieved a UCVA of 0.00 according to logMAR calculation method. Total higher-order root-mean square increased by a factor 1.18 for Group 1 and 1.6 for Group 2. There was a significant increase of coma by a factor 1.74 in Group 2 and spherical aberration by a factor 2.09 in Group 1 and 3.56 in Group 2.

CONCLUSIONS

The data support the safety and effectiveness of the wavefront-guided PRK using a WASCA Workstation for correction of low to moderate refractive errors. This method reduced the number of higher order aberrations induced by excimer laser surgery and improved uncorrected and spectacle-corrected visual acuity when compared to conventional PRK.

Optical Quality of the Eye Degraded by Time-Varying Wavefront Aberrations with Tear Film Dynamics

PURPOSE

Wavefront aberrations (WFAs) of the eye vary with time because of the tear film dynamics. We investigated, using a simulation method, the variation of optical quality with time-varying wavefront measurements of 13 eyes with different refractions.

METHODS

WFAs of 13 normal eyes of 13 subjects were measured every second for 10 s. First, we simulated WFAs with conventional corneal laser refractive surgery by subtracting the second-order aberrations of the least aberrated measurement from measured consecutive WFAs. Second, we simulated customized refractive surgery by subtracting the second- to sixth-order aberrations of the least aberrated measurement from measured consecutive WFAs. We calculated Strehl ratios and retinal images from these corrected consecutive WFAs.

RESULTS

In one eye, the root mean square (RMS) values of WFAs with a second-order correction were sometimes smaller than those of WFAs with a second- to sixth-order correction, when these were compared at the same time point after a blink. However, in the other 12 eyes, the RMS values with second- to sixth-order corrections were smaller than those with only a second-order correction. In eight eyes, the Strehl ratios with second- to sixth-order corrections were larger than those with second-order corrections. In the remaining five eyes, Strehl ratios with second- to sixth-order corrections were sometimes smaller than those with second-order corrections.

CONCLUSIONS

In a simulation, the correction of time-invariant higher order aberrations usually reduced RMS values, but it did not always result in higher Strehl ratios than those obtained with only second-order corrections.

Corneal Wavefront-guided Ablation With the Schwind ESIRIS Laser for Myopia

PURPOSE

To evaluate the outcome of corneal wavefront-guided LASIK for the treatment of myopia and myopic astigmatism.

METHODS

This study included 56 myopic virgin eyes of 28 patients with a mean spherical equivalent refraction of -4.40 +/- 1.83 diopters (D) (range: -1.25 to -9.75 D) and astigmatism < 2.50 D. The corneal wavefront aberrations were analyzed using a corneal topography system. The preoperative corneal wavefront aberration data obtained from the above analyses combined with manifest refraction were used to generate a customized ablation profile. The safety, efficacy, and predictability of the correction, contrast sensitivity, and corneal higher order wavefront aberrations were evaluated.

RESULTS

At 1-year follow-up, the mean residual spherical equivalent refractive error was -0.15 +/- 0.3 D (range: 0 to -1.25 D) and mean cylinder was -0.54 +/- 0.34 D (range: 0 to -1.50 D). Ninety-five percent of eyes were in the residual refractive error range of +/- 0.50 D and uncorrected visual acuity improved by 1.00 D or better in 94% of eyes. The safety index and efficacy index were 1.13 and 0.92, respectively. After treatment, corneal higher order wavefront aberrations with a 6-mm pupil diameter increased significantly (paired sample t test, P < .01), and contrast sensitivity with glare had small reductions at high spatial frequencies. Changes in spherical-like aberration (R = 0.708, P < .001) and higher order wavefront aberration (R = 0.449, P = .001), except for coma-like aberration (P = .238), were positively correlated with the amount of achieved correction.

CONCLUSIONS

Evaluation of clinical results showed that corneal wavefront-guided LASIK for the correction of myopia and myopic astigmatism was safe and effective. There was an increase in all higher order aberrations postoperatively.

Wavefront-guided LASIK for Myopia Using the LADAR CustomCornea and the VISX CustomVue

PURPOSE

To evaluate the objective and subjective visual outcomes and refractive results of wavefront-guided LASIK with LADAR CustomCornea and VISX CustomVue.

METHODS

This prospective randomized single-institution multisurgeon study comprised 100 eyes of 58 patients (50 eyes on each laser platform). Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction were measured postoperatively at 1 day, 1 week, 1 month, and 3 months. Contrast sensitivity, higher order aberrations measurement, and a subjective vision questionnaire were performed preoperatively and at 3 months.

RESULTS

Preoperatively, the CustomCornea group had a mean manifest sphere of -3.58 +/- 1.61 diopters (D) (range: -0.50 to -7.25 D), cylinder of +0.64 +/- 0.45 D (range: 0 to +1.75 D), and manifest refractive spherical equivalent (MRSE) of -3.26 +/- 1.56 D. The CustomVue group had a manifest sphere of -4.00 +/- 1.69 D (range: -1.50 to -7.50 D), cylinder of +0.60 +/- 0.52 D (range: 0 to +2.00 D), and MRSE of -3.70 +/- 1.64 D. At 3 months, 94% of CustomCornea eyes and 84% of CustomVue eyes had UCVA > or = 20/20 (P = .20). Twenty-four percent of CustomVue eyes and 22% of CustomCornea eyes gained 1 line of BSCVA. In both groups, 96% of eyes were within 0.50 D of emmetropia. Mean CustomCornea glare contrast sensitivity improved (P = .04) whereas more eyes improved than worsened in both groups. Spherical aberration and total higher order aberrations increased, and trefoil decreased in both groups. A decrease in coma was noted in 70% of CustomCornea eyes.

CONCLUSIONS

Wavefront-guided LASIK with both platforms is safe, effective, and delivers excellent visual results. CustomCornea improves contrast sensitivity under glare conditions.

Bilateral Comparison of Conventional Versus Topographic-guided Customized Ablation for Myopic LASIK With the NIDEK EC-5000

PURPOSE

To compare visual acuity and higher order aberrations before and after myopic LASIK using conventional versus customized ablation.

METHODS

This prospective, randomized study included 54 myopic eyes in 27 patients who underwent bilateral LASIK using the NIDEK EC-5000 excimer laser system (NIDEK Technologies, Gamagori, Japan). Customized aspheric treatment zone (CATz) treatment was used in one eye (CATz group) and conventional ablation (conventional group) was used in the fellow eye. Uncorrected visual acuity (UCVA) and higher order aberrations (root-mean-square [RMS] in 4-mm and 6-mm zones) of both groups were observed with the NIDEK OPD-Scan aberrometer before and 3 months after LASIK. Preoperative mean refractive error was similar for both eyes of each patient (P>.05).

RESULTS

No statistically significant differences were noted in preoperative higher order aberrations (RMS in 4-mm and 6-mm zones) between groups (P>.05). No statistically significant difference was noted between pre- and postoperative higher order aberrations in the CATz group (P>.05). However, a highly statistically significant increase in higher order aberrations was observed after conventional ablation (P<.001). There was a statistically significant higher increase of higher order aberrations after LASIK in the conventional group than the CATz group (P<.05). Postoperative UCVA with both conventional and customized ablation was not significantly different (P>.05).

CONCLUSIONS

LASIK with conventional ablation and CATz ablation resulted in the same UCVA. The increase in higher order aberrations after CATz ablation was less than after conventional ablation.

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

Conventional and wavefront-guided myopic LASIK retreatment

PURPOSE

To assess the clinical outcomes of conventional and wavefront-guided myopic laser in situ keratomileusis (LASIK) retreatment.

DESIGN

Retrospective, nonrandomized case series.

METHODS

The study comprised a cohort of 97 eyes having LASIK retreatment for residual myopia after primary LASIK. The eyes were divided into two groups: conventional retreatment (CR) group (n = 74) and wavefront-guided retreatment (WR) group (n = 23). The retreatment LASIK was performed using LADARVison 4000 with/without CustomCornea (Alcon Surgical, Orlando, Florida, USA). The mean follow-up was 8.9 +/- 5.8 months after retreatment (range three to thirty-six months).

RESULTS

The mean pre-retreatment spherical equivalent (SE) was -0.93 +/- 0.41 diopters in the CR group and -0.84 +/- 0.48 diopters in the WR group (P = .409). At the last visit, the mean SE was -0.19 +/- 0.28 diopters and +0.32 +/- 0.47 diopters, respectively (P < .001). An SE of +/- 0.50 diopters was achieved in 92% (68 of 74) of CR eyes and 65% (15 of 23) of WR eyes. In the CR group, 85% eyes had a uncorrected visual acuity (UCVA) > or = 20/20 and 99% > or = 20/40, and in the WR group, 35% and 100%, respectively. None of the CR eyes and 17% (4 of 23) of WR eyes lost two lines of best spectacle-corrected visual acuity (BSCVA). Nine percent (7 of 74) of CR eyes and 30% of WR eyes (7 of 23) had optical symptoms before retreatment, the number was reduced to 1% (1 of 74) and 4% (1 of 23), respectively.

CONCLUSIONS

In the study period with the current equipment, our results showed that conventional LASIK retreatment was superior to wavefront-guided LASIK retreatment in both efficacy and safety.

LASIK for Myopia With the Zeiss Meditec MEL 80

PURPOSE

To prospectively evaluate a new high-speed, small spot-scanner laser for the correction of myopia and myopic astigmatism.

METHODS

Seventy-six consecutive eyes with myopia and myopic astigmatism between -1.00 and -8.25 diopters (D) and up to -2.75 D astigmatism underwent LASIK treatment using the MEL 80 laser (Carl Zeiss Meditec, Jena, Germany). Parameters evaluated were uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), residual refractive error, regression of correction, and aberrometry.

RESULTS

Mean preoperative BSCVA was 20/20, which improved to 20/18 postoperatively. Postoperative UCVA was 20/20 at 1 month and 20/18 at 1 year. Uncorrected visual acuity > or = 20/20 was achieved in 58 (83%) of 70 eyes at 1 month and in 60 (88%) of 68 eyes at 1 year. The average refractive error before LASIK was -4.41 +/- 1.98 D. The mean residual refractive error was 0.14 +/- 0.31 D at 1 month and 0.13 +/- 0.30 D at 1 year. At 1-month and 1-year follow-up, respectively, 66 (94%) of 70 eyes and 65 (96%) of 68 eyes were within +/- 0.50 D of intended refractive correction. No eye lost two lines. At 1 month 17% of eyes and at 1 year 13% of eyes gained two lines or more. Between 1-month and 1-year follow-up, 100% of eyes were stable. Mean root-mean-square high order aberration changed from 0.20 microm preoperatively to 0.28 microm postoperatively.

CONCLUSIONS

The MEL 80 is effective and safe in the treatment of myopia and myopic astigmatism.

Clinical Outcomes of CATz Versus OPDCAT

PURPOSE

To compare refractive outcomes, wavefront outcomes, and corneal asphericity indices (Q values) for patients treated with wavefront-guided or topography-guided custom ablations using the NIDEK Advanced Vision Excimer Laser System (NAVEX).

METHODS

A total of 196 eyes of 98 patients underwent wavefront-guided or topography-guided LASIK. A contralateral study of 28 eyes of 14 patients who underwent customized aspheric treatment zone (CATz) ablation in one eye and optical path difference customized aspheric treatment (OPDCAT) in the fellow eye comprised one part of the study. The second part of the study was a retrospective review of myopic LASIK using CATz in 84 eyes and LASIK using OPDCAT in 84 eyes. In the CATz-treated eyes, the preoperative mean spherical equivalent refraction was -4.06+/-1.69 diopters (D). In OPDCAT-treated eyes, the preoperative mean spherical equivalent refraction was -3.67+/-2.17 D.

RESULTS

In the CATz-treated eyes, 95% of eyes achieved > or = 20/20 best spectacle-corrected visual acuity (BSCVA) with 15% gaining lines of BSCVA. In the OPDCAT-treated eyes, 94.5% of eyes achieved > or = 20/20 vision with 4.5% gaining lines of BSCVA. The difference in lines gained between CATz and OPDCAT in the retrospective component was statistically significant (P<.005). OPDCAT-treated eyes showed a statistically significant worsening in OPD root-mean-square (OPD-RMS), higher order wavefront error, and corneal asphericity (P<.005) compared to preoperative in the retrospective portion of the study. In the contralateral arm of the study, OPD-RMS value was significantly higher (P<.005) in the OPDCAT eyes than the fellow CATz-treated eyes. OPDCAT-treated eyes show a larger change in the Strehl ratio compared to the CATz-treated eyes (P<.005).

CONCLUSIONS

The refractive outcomes were excellent and showed no clinically significant difference between CATz and OPDCAT treatments. The higher induction of aberrations with the OPDCAT ablations may be due to the fact that these treatments are based on Zernike polynomials to drive the ablation.

Wavefront-guided correction of ocular aberrations: are phase plate and refractive surgery solutions equal?

Wavefront-guided laser eye surgery has been recently introduced and holds the promise of correcting not only defocus and astigmatism in patients but also higher-order aberrations. Research is just beginning on the implementation of wavefront-guided methods in optical solutions, such as phase-plate-based spectacles, as alternatives to surgery. We investigate the theoretical differences between the implementation of wavefront-guided surgical and phase plate corrections. The residual aberrations of 43 model eyes are calculated after simulated refractive surgery and also after a phase plate is placed in front of the untreated eye. In each case, the current wavefront-guided paradigm that applies a direct map of the ocular aberrations to the correction zone is used. The simulation results demonstrate that an ablation map that is a Zernike fit of a direct transform of the ocular wavefront phase error is not as efficient in correcting refractive errors of sphere, cylinder, spherical aberration, and coma as when the same Zernike coefficients are applied to a phase plate, with statistically significant improvements from 2% to 6%.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Higher Order Aberrations With Aspheric Ablations Using the Nidek EC-5000 CX II Laser

PURPOSE

To analyze the change in higher order aberrations in myopic and myopic astigmatic eyes following an aspheric ablation profile for laser in situ keratomileusis (LASIK) using a Nidek EC-5000 CX II excimer laser system.

METHODS

We performed a retrospective audit of 38 eyes (19 patients) with myopia and myopic astigmatism. A customized aspheric transition zone profile (CATz) was used in all eyes (profile 4) with an ablation zone of 5 mm and a transition zone of 9 mm using FinalFit software and a Nidek EC-5000 CX II excimer laser system.

RESULTS

Mean higher order aberrations (RMS) increased from 0.42 microm at baseline to 0.57 microm at 6-month follow-up. Mean spherical aberrations (Z12) increased from 0.02 microm at baseline to 0.33 microm after LASIK. Mean spherical aberration defocus equivalent (DEQ) increased from 0.56 microm at baseline to 1.54 at 6 months after surgery. Mean trefoil (Z6) was -0.11 microm at baseline and -0.14 microm at the 3-month examination. Mean coma (Z7) was -0.09 microm at baseline and -0.10 microm after surgery. Mean coma (Z8) was -0.03 at baseline and 0 at the 3-month examination. Mean trefoil (Z9) was -0.03 at baseline and -0.12 at the 3-month examination.

CONCLUSION

The amount of postoperative higher order aberrations in these myopic eyes was acceptable. However, the clinical significance of these numerical changes in aberrations is not known.

Laser in situ Keratomileusis for High Myopia Using a Small Ablation Zone and Large Aspheric Transition Zone

PURPOSE

To evaluate the efficacy and predictability of laser in situ keratomileusis (LASIK) using the Nidek NAVEX system with a small ablation (optical, OZ) zone and a large aspheric transition zone (OATz).

METHODS

We report a prospective nonrandomized study of LASIK for high myopia using a small ablation in 23 eyes of 18 patients. The optical zone was between 3 and 3.8 mm and transition zone (TZ) was between 7 and 7.8 mm. Preoperative examination included best-spectacle corrected visual acuity (BSCVA), refraction, and corneal topography. All eyes were measured by the Nidek OPD-Scan and data were imported to FinalFit software. Aspheric profile (OATz) numbers 5 to 7 were used. BSCVA, uncorrected spectacle visual acuity (UCVA), refraction, and subjective evaluation of glare and night vision by questionnaire were recorded after surgery.

RESULTS

At baseline, mean spherical equivalent refraction was -7.03 +/- 2.39 D (range -5.50 to -15.50 D). Postoperative UCVA was better than 20/25 in 95.65% of eyes 3 months after LASIK. Postoperative refraction was within +/- 0.50 D of emmetropia in 91.3% of eyes and within +/- 1.00 D in all eyes. No eye lost lines of BSCVA; 52.17% of eyes gained 1 line and 13.04% of eyes gained 2 lines. No patient reported significant glare or night vision problems on subjective questionnaire.

CONCLUSION

LASIK with a small ablation (optical) zone and high aspheric transition zone using the Nidek NAVEX system was effective, predictable, and relatively safe for correction of high myopia.

Wavefront Aberrations Following Laser in situ Keratomileusis and Refractive Lens Exchange for Hypermetropia

PURPOSE

To compare the magnitude of aberrations in eyes after elective hypermetropic laser in situ keratomileusis (LASIK) and refractive lens exchange (clear lens replacement).

METHODS

Forty-nine patients (92 eyes) had hypermetropic LASIK and 28 (48 eyes) had refractive lens exchange; 23 hypermetropic subjects (41 eyes) were the control group. LASIK was performed with the Nidek EC-5000 excimer laser; ablation zones 5.5 to 6.0-mm in diameter with transition zones 7.5 to 8-mm in diameter. For refractive lens exchange, all but four IOLs were made of foldable acrylic. Aberrations and corneal topography were measured with the Nidek OPD-Scan model ARK-10000 more than 12 months after surgery. The higher-order root-mean-square (HORMS) wave aberrations for combined third to sixth Zernike aberration orders and the Zernike spherical aberration coefficient C(0)(4) at both 4.2-mm and 6.0-mm pupil sizes were calculated.

RESULTS

For the LASIK group, surgical refractive change correlated significantly with total, corneal, and internal HORMS and spherical aberrations (except with internal spherical aberration for a 4.2-mm diameter pupil). For the refractive lens exchange group, there were no significant correlations of surgical refractive change with any of these factors. Similarly, there were no significant correlations of refraction with any of these factors for the control group. For a 3-diopter change in refraction with 6-mm pupils, LASIK doubled the total HORMS aberrations. LASIK changed the sign of spherical aberration from positive to negative by increasing the negative asphericity of the anterior cornea. Taking age differences between groups into account, refractive lens exchange increased the total HORMS aberrations by 40% compared with that of the control group, but this was not statistically significant. However, refractive lens exchange significantly increased total spherical aberration.

CONCLUSION

Refractive lens exchange was a better refractive procedure than LASIK for minimizing total higher order optical aberrations that accompany hypermetropic refractive surgery.

Wavefront-guided Laser in situ Keratomileusis With the Bausch & Lomb Zyoptix System

PURPOSE

To evaluate the clinical results of wavefront-guided laser in situ keratomileusis (LASIK) with the Zyoptix system.

METHODS

Twelve patients (24 eyes) underwent wavefront-guided LASIK with the Bausch & Lomb Zyoptix system. Uncorrected and best spectacle-corrected visual acuity and manifest refraction were measured at postoperative day 1, week 1, and months 1 and 3. A subjective vision quality questionnaire evaluated light sensitivity, dryness, tearing, glare, halos, ghost images, and difficulties in night driving, preoperatively and 3 months postoperatively.

RESULTS

Preoperatively, mean sphere was -3.70 +/- 2.33 D (range -0.50 to -8.00 D), mean cylinder was -0.90 +/- 0.98 D (range 0 to -3.00 D), and mean spherical equivalent refraction was -4.15 +/- 2.16 D (range -1.38 to -8.25 D). Three-month postoperative spherical equivalent refraction was within +/- 0.50 D of emmetropia in 17 eyes (70.8%) and within +/- 1.00 D in 22 eyes (91.7%). At 3 months postoperatively, no eyes lost any lines of BSCVA and eight eyes (33.3%) gained 2 lines. The ratio of postoperative BSCVA to preoperative BSCVA (safety) was 1.05 +/- 0.09 (range 1.00 to 1.20) at 1 month and 1.07 +/- 0.10 (range 1.00 to 1.29) at 3 months. The ratio of postoperative UCVA to preoperative BSCVA (efficacy) was 0.96 +/- 0.12 (range 0.80 to 1.20) at 1 month and 0.95 +/- 0.12 (range 0.8 to 1.2) at 3 months. The subjective vision quality questionnaire revealed less tearing, fewer halos, and less difficulty in night driving after wavefront-guided LASIK. Comparison of higher order optical aberrations before and after surgery was not done.

CONCLUSIONS

Wavefront-guided LASIK with the Bausch & Lomb Zyoptix system was safe and effective in correcting low to moderate myopic refractive error.

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

PURPOSE

To evaluate and compare the visual and clinical outcomes of wavefront-guided laser in situ keratomileusis (LASIK) with the Alcon CustomCornea (Alcon Laboratories Inc, Fort Worth, Tex) and VISX CustomVue (VISX, Santa Clara, Calif) systems.

METHODS

Ninety-three eyes of 56 patients (50 and 43 consecutive eyes on CustomCornea and CustomVue, respectively) were enrolled in a prospective multisurgeon clinical outcome study. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and manifest refraction were measured at 1 day, 1 week, 1 month, and 3 months postoperatively. Early treatment diabetic retinopathy study (ETDRS) visual acuity and contrast sensitivity were measured at 1 month and 3 months, and wavefront mapping at 3 months.

RESULTS

Preoperatively, the CustomCornea group had a mean sphere of -3.90 +/- 1.62 diopters (D) (range -0.50 to -7.25 D), mean cylinder of +0.62 +/- 0.39 D (range 0 to +1.50 D), and mean manifest spherical equivalent refraction of -3.59 +/- 1.54 D. The CustomVue group had a sphere of -3.87 +/- 1.45 D (range -1.75 to -6.75 D), cylinder of +0.49 +/- 0.36 D (range 0 to +1.50 D), and manifest spherical equivalent refraction of -3.62 +/- 1.46 D. At 3 months, 98% of the CustomCornea group and 95% of the CustomVue group were within +/-0.50 D. Ninety-nine percent of eyes did not change >0.50 D (manifest spherical equivalent refraction) between 1 month and 3 months. CustomCornea eyes improved on contrast sensitivity testing and had a better profile than CustomVue for 20/15 Snellen and 20/12.5 ETDRS acuity. Both laser groups had a decrease in higher order aberrations with statistical significance for coma and spherical aberration in the CustomCornea group.

CONCLUSION

Wavefront-guided LASIK with both systems is safe and effective.

Wavefront-guided Ablation With Bausch and Lomb Zyoptix for Retreatments After Laser in situ Keratomileusis for Myopia

PURPOSE

To evaluate the efficacy of wavefront-guided ablation for treatment of residual refractive error and higher order aberrations after laser in situ keratomileusis (LASIK) for myopia.

METHODS

Twenty-one eyes of 13 patients with residual refractive error after myopic LASIK were treated with a wavefront-guided ablation with the Zyoptix technique. In 13 eyes of 8 patients (Group A) we lifted the flap with an epitheliorhexis technique; in 8 eyes of 5 patients (Group B) we cut a new flap with a Hansatome microkeratome.

RESULTS

Preoperative root mean square (RMS) values were 1.370 for second order aberrations, 0.382 for total higher order aberrations, 0.273 for third order, 0.243 for fourth order, and 0.052 for fifth order aberrations. Three months postoperatively, RMS values decreased significantly to 0.278 (second order), 0.189 (total higher order), 0.138 (third order), 0.107 (fourth order), and 0.038 (fifth order). Ablation depth was two times greater than needed with a standard Planoscan treatment. Patients in the microkeratome recut group showed a trend toward overcorrection, and residual astigmatism was higher (-0.75 +/- 0.58 D) than in the flap lift group (-0.25 +/- 0.29 D).

CONCLUSIONS

Wavefront-guided ablation was an effective method to correct residual refractive error and higher order aberrations after myopic LASIK. Functional and refractive outcomes were better when we lifted the flap than when we recut the flap.

Update on customized excimer ablations: recent developments reported in 2002

Customized corneal ablation is an exciting frontier in refractive surgery that incorporates wavefront technology to detect and correct higher order aberrations in addition to spherocylindrical refractive errors. The goal is to achieve super normal vision in terms of acuity and contrast. As the concept of wavefront customized ablations is still new, there are a number of aspects of its clinical application that need analysis and understanding. Numerous reports have appeared in the literature during the past year that address the developments, concerns, and limitations of wavefront technology and custom ablation. We have attempted to summarize and discuss the significant reports in this current review. Our focus is on the optical and physiologic limits of wavefront customized correction, including the effect of accommodation, aging, and flap creation on the aberration profile. In addition, we also present the laser technology requirements, and clinical outcomes of customized excimer ablations that are reported to date.

Comparison of designs of laser systems utilized for refractive surgery

Several different laser types are available on the market for the practitioner to use in refractive surgery. Each laser type has certain parameters that the surgeon must understand to obtain the best refractive outcomes. Studies published in peer-reviewed literature between February 2002 and March 2003 show that refractive results across all types of lasers have improved compared with those of several years ago. A difference in refractive outcomes between lasers is impossible to directly compare, as there are no randomized studies that hold surgeon or patient characteristics constant.

Measuring of ocular wavefront aberration in large pupils using OPD-scan

Wavefront analysis using a scanning slit refractometer (the OPD-Scan) was evaluated in both artificial and human eyes, in comparison with the Hartmann-Shack wavefront sensor (H-S) currently often used. Comparison of different methods and configurations carried out in the artificial eyes yielded basically the same results in moderate refractive error cases. There was a closer match between the RMS (root mean square) wavefront error obtained by OPD-Scan and H-S in the 6 mm pupils than in the 4 mm pupils of the same normal human eyes. Although OPD-Scan employs a different approach in determining aberration, the aberration value is similar to that of H-S, especially in large pupils.

Changes of Higher Order Aberration With Various Pupil Sizes in the Myopic Eye

PURPOSE

To investigate the effect of pupil diameter on higher order aberration in myopic eyes.

METHODS

One hundred and two eyes of 51 normal subjects were evaluated with the Nidek OPD-Scan.

RESULTS

All types of aberration increased significantly with increasing pupil size (P<.001). However, optical aberrations had a less pronounced increase in C3(-1) and C3(+1) , more pronounced increase in C4(0) with pupil area increased (P<.05), 2nd coma (C5(-1) and C6(+1)) and high order astigmatism (C4(-2), C4(+2) C6(-2), C6(+2) with larger pupil diameter. Compared with the aberrations of each high order aberration at 4 mm, the average increase root mean square values were 1.54, 1.59, 1.71, and 1.87 on S3, S4, S5, and S6 respectively, with a 5-mm pupil, whereas increased root mean square values were 1.46, 1.88, 1.51, and 1.60 for a 6-mm-diameter pupil.

CONCLUSION

For an equal increase of pupil size, not all Zernike polynomial coefficients induced equivalent increase of values. Coma-like aberrations increased less with pupil dilation. Spherical-like aberration showed only a small increase from 4 mm to 5 mm pupil size, but a larger increase from 5 mm to 6 mm pupil size. Other higher order aberrations (S5 and S6) increased slightly with pupil dilation. Coma-like aberration was larger than spherical aberration, and larger than other higher order aberrations for all pupil sizes.

Comparison of Conventional Versus Wavefront-guided Laser in situ Keratomileusis in the Same Patient

PURPOSE

To verify whether there is any difference in visual outcome, including higher order aberrations, after performing laser in situ keratomileusis (LASIK) with conventional ablation and wavefront-guided ablation in myopic eyes of the same patient.

METHODS

This was a prospective randomized study of 20 myopic eyes (10 patients) who had LASIK using the Nidek NAVEX excimer laser system. Wavefront-guided customized ablation was used in the first eye of the patient (study group) and the other eye of the same patient was operated with conventional ablation (control group). Mean refractive error was similar between left and right eyes of the same patient. Preoperative examination included higher order aberration by Nidek OPD-Scan. Uncorrected and best spectacle-corrected visual acuity and higher order aberrations were recorded postoperatively.

RESULTS

Preoperative and postoperative best spectacle-corrected visual acuity was better than 20/40 (100%) after LASIK in both the conventional ablation and wavefront-guided customized ablation groups. Postoperative refraction was within +/- 0.50 D of emmetropia: 90% in the conventional group and 100% in the wavefront-guided group. No statistically significant difference in postoperative higher order aberrations was found between groups.

CONCLUSION

Postoperative visual outcome with both conventional LASIK and wavefront-guided customized ablation was not significantly different. Higher order aberrations did not significantly increase postoperatively in either group.