Journal of Refractive Surgery

Original Article Supplemental Data

Outcomes for Mixed Cylinder LASIK With the MEL 90® Excimer Laser

Dan Z. Reinstein, MD, MA(Cantab), FRCSC; Glenn I. Carp, MBBCh, FCOphth (SA); Timothy J. Archer, MA(Oxon), DipCompSci(Cantab), PhD; Alexander C. Day, PhD, FRCOphth, CertLRS; Ryan S. Vida, OD, FAAO

Abstract

PURPOSE:

To report the outcomes of LASIK for mixed cylinder using the Triple-A ablation profile with the MEL 90 excimer laser (Carl Zeiss Meditec, Jena, Germany).

METHODS:

This was a retrospective analysis of all eyes treated by LASIK for mixed cylinder using the Triple-A ablation profile with the MEL 90 laser between July 2013 and October 2016. Patients were observed for 1 year after surgery. Standard outcomes analysis and vector analysis by the Alpins method were performed.

RESULTS:

The database review identified 105 eyes (82 patients) treated by LASIK for mixed cylinder using the MEL 90 laser. Mean age was 40 ± 11 years (range: 18 to 65 years). Mean attempted spherical equivalent was +0.30 ± 0.90 diopters (D) (range: −2.30 to +1.75 D). Mean cylinder was −2.93 ± 1.47 D (range: −0.75 to −7.00 D). Preoperative corrected distance visual acuity (CDVA) was 20/20 or better in 81% of eyes. Postoperative uncorrected distance visual acuity was 20/20 or better in 69% and 20/25 or better in 86% of eyes. Mean postoperative spherical equivalent relative to the intended target was −0.21 ± 0.38 D (range: −1.25 to +1.13 D), with 83% within ±0.50 D. Mean postoperative cylinder was −0.57 ± 0.41 D (range: 0.00 to −1.75 D). Geometric mean was 1.12 for the correction index and 0.25 for the index of success. For angle of error, the arithmetic mean was −0.6° ± 4.2° (range: −13.5° to 9.5°) and the absolute mean was 2.9° ± 3.0° (range: 0.0° to 13.5°). There was loss of one line of CDVA in 3% of eyes and no eyes lost two or more lines CDVA. There was a small increase in contrast sensitivity after surgery at 3, 6, 12, and 18 cycles per degree (P < .05).

CONCLUSIONS:

One-year outcomes of LASIK using the MEL 90 laser for mixed cylinder up to −7.00 D demonstrated excellent efficacy, safety, and predictability. Vector analysis found a 12% overcorrection in magnitude of refractive cylinder. Given the high accuracy for angle of error, a nomogram could be applied to reduce the over-correction and further improve the uncorrected distance visual acuity outcomes.

[J Refract Surg. 2018;34(10):672–680.]

Abstract

PURPOSE:

To report the outcomes of LASIK for mixed cylinder using the Triple-A ablation profile with the MEL 90 excimer laser (Carl Zeiss Meditec, Jena, Germany).

METHODS:

This was a retrospective analysis of all eyes treated by LASIK for mixed cylinder using the Triple-A ablation profile with the MEL 90 laser between July 2013 and October 2016. Patients were observed for 1 year after surgery. Standard outcomes analysis and vector analysis by the Alpins method were performed.

RESULTS:

The database review identified 105 eyes (82 patients) treated by LASIK for mixed cylinder using the MEL 90 laser. Mean age was 40 ± 11 years (range: 18 to 65 years). Mean attempted spherical equivalent was +0.30 ± 0.90 diopters (D) (range: −2.30 to +1.75 D). Mean cylinder was −2.93 ± 1.47 D (range: −0.75 to −7.00 D). Preoperative corrected distance visual acuity (CDVA) was 20/20 or better in 81% of eyes. Postoperative uncorrected distance visual acuity was 20/20 or better in 69% and 20/25 or better in 86% of eyes. Mean postoperative spherical equivalent relative to the intended target was −0.21 ± 0.38 D (range: −1.25 to +1.13 D), with 83% within ±0.50 D. Mean postoperative cylinder was −0.57 ± 0.41 D (range: 0.00 to −1.75 D). Geometric mean was 1.12 for the correction index and 0.25 for the index of success. For angle of error, the arithmetic mean was −0.6° ± 4.2° (range: −13.5° to 9.5°) and the absolute mean was 2.9° ± 3.0° (range: 0.0° to 13.5°). There was loss of one line of CDVA in 3% of eyes and no eyes lost two or more lines CDVA. There was a small increase in contrast sensitivity after surgery at 3, 6, 12, and 18 cycles per degree (P < .05).

CONCLUSIONS:

One-year outcomes of LASIK using the MEL 90 laser for mixed cylinder up to −7.00 D demonstrated excellent efficacy, safety, and predictability. Vector analysis found a 12% overcorrection in magnitude of refractive cylinder. Given the high accuracy for angle of error, a nomogram could be applied to reduce the over-correction and further improve the uncorrected distance visual acuity outcomes.

[J Refract Surg. 2018;34(10):672–680.]

In mixed cylinder, the axis of maximum refractive power is myopic and anterior to the retina, and the axis of minimum refractive power is hyperopic and posterior to the retina; therefore, refractive correction by excimer laser requires flattening in one axis and steepening in the other. The ablation profile is therefore different than that required for the correction of simple or compound astigmatism. The main strategies have been bitoric,1–9 where the ablation is split into a myopic and a hyperopic component, or monotoric, including cross-cylinder followed by spherical equivalent10 and positive cylinder followed by negative sphere.11 The bitoric approach has proved to be the most popular, largely because it leads to the minimum ablation depth.12

The bitoric ablation strategy was first described in 1998 by Chayet et al.,1 and also set out the potential for coupling effects between the steepening and flattening components that would need to be accounted for to achieve the desired spherical equivalent. Although the Chayet nomogram was based on a coupling effect from the myopic cylinder, Alpins et al.13 showed that hyperopic cylinder correction can also be associated with a spherical shift (coupling) and have described a method for calculating these coupling factors.9 Outcomes of LASIK for mixed cylinder have been reported previously for several platforms.2–11,14–22

The aim of this study was to report the visual and refractive results of LASIK for the correction of mixed astigmatism performed with the MEL 90 and VisuMax femtosecond lasers (Carl Zeiss Meditec, Jena, Germany).

Patients and Methods

Patients

This was a retrospective non-comparative case series of all mixed cylinder LASIK procedures treated consecutively between July 2013 and October 2016 by two experienced LASIK surgeons (DZR, GIC) using the MEL 90 and VisuMax femtosecond lasers at the London Vision Clinic, London, United Kingdom. The analysis included all eyes in which a mixed cylinder correction was performed using the Triple-A ablation profile. Informed consent and permission to use their data for general analysis and publication was obtained from each patient prior to surgery as part of our routine protocol. Because this was a retrospective study, an exemption from full institutional review board approval was obtained from the United Kingdom Health Research Authority.

A full ophthalmologic examination was performed by one of the in-house optometrists prior to surgery, as has been described previously.23,24 Manifest refraction was performed based on a standardized protocol designed to push maximum plus and maximum cylinder, and all optometrists had undergone refraction training with this protocol.25 The manifest refraction was repeated again by the treating surgeon at a separate visit before the day of surgery and this refraction was used to plan the treatment.

Excimer Laser and Ablation Profile

The MEL 90 excimer laser was introduced in 2013 as an upgrade to its predecessor, the MEL 80 laser. The main changes included a faster pulse rate, compatibility with the new advanced ablation algorithm (Triple-A) profile, and further improved dynamic flow cone for controlled atmosphere. Data on outcomes for the correction of myopia using the Triple-A ablation profile of the MEL 90 laser have been reported previously.24,26–28

The Triple-A profile was used at 500-Hz pulse frequency for all cases. For mixed cylinder, the Triple-A profile is generated as a bitoric profile to flatten the steep meridian and steepen the flat meridian, to which a defocus component is added to correct the spherical equivalent. Any pedestal resulting from the addition is removed to minimize the ablation depth. As for myopic ablations, the Triple-A profile includes an energy correction function to compensate for radial fluence projection and reflection losses and peripheral biomechanical changes.24,26–28

The optical zone used was between 6 and 7 mm, with a larger optical zone for eyes with a greater hyperopic cylinder component depending on pachymetric safety limits. The transition zone is fixed by the software to be 2 mm in all cases. No adjustments were made to the built-in nomogram.

Surgical Protocol

All treatments were performed as bilateral simultaneous LASIK using the VisuMax femtosecond laser.29–32 The programmed flap thickness was 115 μm in most cases, but a thinner flap (down to 85 μm) was used to maximize the stromal tissue available for ablation and adhere to the minimum residual stromal bed thickness of 250 μm. Flap diameter was programmed to be either 8 mm using small contact glasses or 8.8 mm using medium contact glasses. During the study period, a new method for reducing the incidence of opaque bubble layer jets33,34 was introduced and was used for all eyes treated from June 2016. In this method, the flap diameter was increased by 0.1 mm by programming with a larger contact glass than the size to actually be used. Therefore, the lamellar interface would start closer to the edge of the contact glass, thus allowing the gas to escape peripherally rather than being forced centrally. Side cut for all VisuMax flaps was set as an in-cut of 55° from the normal. The choice between small and medium contact glasses was based on the white-to-white measurement from the ATLAS topographer (Carl Zeiss Meditec). Medium contact glasses were used for white-to-white values of 11.5 mm or greater and small contact glasses were used for white-to-white values less than 11.5 mm. A 5-mm superior hinge was used in all cases. The VisuMax energy profile was set to an energy index of 50 (250 nJ), with spot and track spacing of 5 μm for flap bed and 2 μm for side cut. Treatments were centered on the coaxially sighted corneal light reflex.35 The standardized surgical technique followed has been described previously.36

The target postoperative sphere was hyperopic for all patients younger than 42 years; a linear function was used whereby the target sphere was +0.66 diopters (D) for a 21 year old down to plano for a 42 year old. Our micro-monovision protocol23,37 was used for all patients older than 42 years, where the target sphere is plano for the dominant eye and −1.50 D for the non-dominant eye for most patients.

Postoperative Evaluation

Patients were instructed to wear plastic shields while sleeping for 7 nights. Tobramycin–dexamethasone (Tobradex; Alcon, Laboratories, Inc., Fort Worth, TX) and ofloxacin (Exocin; Allergan Ltd, Marlow, United Kingdom) were applied four times daily for the first week, which is our standard protocol for broad-spectrum prophylaxis. Patients were reviewed at 1 day, 1 month, 3 months, and 12 months. The 1-day postoperative visit was conducted by the surgeon and included a slit-lamp examination, binocular and monocular uncorrected distance visual acuity (UDVA), and a spherical manifest refraction. The flap was adjusted at the slit lamp using a surgical spear if any microfolds were identified. All subsequent follow-up visits were conducted by one of the in-house optometrists and included measurements of monocular and binocular UDVA, manifest refraction, and corrected distance visual acuity (CDVA). Best-corrected mesopic contrast sensitivity was performed at the 3- and 12-month visits.

Postoperative complications including microfolds, epithelial ingrowth, interface haze, interface debris, infection, superficial punctate keratitis, and diffuse lamellar keratitis were assessed at each visit using a 6-grade classification system: trace, grades I and II (not visually significant), and grades III to V (visually significant). In this scale, trace refers to any small amount inconsistent with an untreated cornea, even if not visually significant.

Statistical Analysis

Outcome analysis was performed according to the Standard Graphs for Reporting Refractive Surgery.38 Eyes where the intended postoperative refraction was not emmetropia were excluded in the efficacy analysis. Vector analysis was performed for refractive cylinder as described by Alpins,39 with the cylinder axes reflected in the vertical meridian for left eyes. Data from the 12-month visit were used for analysis if available, otherwise 3-month data were used. The outcomes were analyzed for the primary treatment data, excluding retreatments. Student's t tests were used to calculate the statistical significance of any changes in log contrast sensitivity.

Subgroup analysis was performed to report the results for each diopter bin of cylinder treated. The key outcome statistics for efficacy, safety, and predictability were recorded for each subgroup. Subgroup analysis was also performed to compare the results by with-the-rule and against-the-rule cylinder. A further subgroup analysis was performed to compare the results according to the weighting between the myopic and hyperopic cylinder components; the myopic-dominant group was defined as sphere equal to up to 25% of the cylinder magnitude, the hyperopic-dominant group was defined as sphere equal to at least 75% of the cylinder magnitude, and the mixed group included all remaining eyes.

Patient satisfaction with the procedure was verbally assessed and recorded by the clinician at the time of each postoperative examination. This assessment was subsequently quantified and entered into a database using a 5-point scale: 5 = very happy; 4 = happy; 3 = indifferent; 2 = somewhat unhappy; and 1 = unhappy.

Microsoft Excel 2010 software (Microsoft Corporation, Seattle, WA) was used for data entry and statistical analysis. A P value of less than .05 was defined as statistically significant.

Results

During the study period, a total of 105 eyes received a mixed cylinder treatment. Three-month data were available for all eyes and 12-month data were available for 95 eyes (90%). Table 1 shows the demographic data for the study population. The optical zone was 6 mm for 12 eyes (11%), 6.5 mm for 64 eyes (61%), and 7 mm for 29 eyes (28%). Intended flap thickness was 85 μm in 1 eye (1%), 90 μm in 23 eyes (22%), 95 μm in 5 eyes (5%), 100 μm in 3 eyes (3%), 105 μm in 14 eyes (13%), 110 μm in 3 eyes (3%), and 115 μm in 56 eyes (53%).

Study Demographics

Table 1:

Study Demographics

Figure 1 shows the Standard Graphs for Reporting Refractive Surgery. UDVA was 20/20 or better in 73% of eyes, relative to 84% with preoperative CDVA of 20/20 or better. Spherical equivalent refraction was within ±0.50 D in 85% and within ±1.00 D in 99% of eyes. There was a gain of one or more lines of CDVA in 33% and no change in 57% of eyes. No eyes lost two or more lines of CDVA. The spherical equivalent refraction was stable with a mean of −0.22 ± 0.39 D at 3 months and −0.19 ± 0.37 D at 12 months.

Nine standard graphs for reporting refractive surgery showing the visual and refractive outcomes for 105 mixed cylinder treatments using the VisuMax femtosecond laser and MEL 90 excimer laser (Carl Zeiss Meditec, Jena, Germany), using the Triple-A ablation profile at 500-Hz frequency. UDVA = uncorrected distance visual acuity; CDVA= corrected distance visual acuity; D = diopters; postop = postoperative; preop = preoperative; SEQ = spherical equivalent refraction; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Figure 1.

Nine standard graphs for reporting refractive surgery showing the visual and refractive outcomes for 105 mixed cylinder treatments using the VisuMax femtosecond laser and MEL 90 excimer laser (Carl Zeiss Meditec, Jena, Germany), using the Triple-A ablation profile at 500-Hz frequency. UDVA = uncorrected distance visual acuity; CDVA= corrected distance visual acuity; D = diopters; postop = postoperative; preop = preoperative; SEQ = spherical equivalent refraction; TIA = target induced astigmatism; SIA = surgically induced astigmatism

Figure 2 shows the vector analysis for refractive cylinder and the main outcome measures are shown in Table 2. The scatter plot for surgically induced astigmatism vector (SIA) versus target induced astigmatism vector (TIA) shows that there was an overcorrection of refractive cylinder with a slope of 1.12. The angle of error histogram shows that the refractive correction was placed accurately on the intended meridian; the angle of error was not more than 15° for any of the eyes. The correction index plot shows that there was no difference between with-the-rule and against-the-rule cases.

Vector analysis of refractive cylinder displayed as polar plots for target induced astigmatism vector, surgically induced astigmatism vector, difference vector, and correction index. D = diopters

Figure 2.

Vector analysis of refractive cylinder displayed as polar plots for target induced astigmatism vector, surgically induced astigmatism vector, difference vector, and correction index. D = diopters

Vector Analysis of Refractive Cylinder

Table 2:

Vector Analysis of Refractive Cylinder

Patient Satisfaction

Figure 3 shows a histogram for the subjective patient satisfaction evaluated using a 5-point scale based on the patient comments in the medical record. There were 5% of patients who were somewhat unhappy (score = 2) after the primary procedure, but this improved to happy or very happy following a re-treatment procedure in all cases.

Histogram of subjective patient satisfaction as recorded following verbal assessment by the clinician at the last postoperative visit.

Figure 3.

Histogram of subjective patient satisfaction as recorded following verbal assessment by the clinician at the last postoperative visit.

Subgroup Analysis

Table A (available in the online version of this article) presents the key outcome parameters with the population grouped by the magnitude of refractive cylinder treated. Table B (available in the online version of this article) presents the key outcome parameters with the population grouped by with-the-rule and against-the-rule/oblique astigmatism, and also grouped by the weighting between the myopic and hyperopic cylinder components. Figure 4 shows the TIA versus SIA scatter plot for the myopic-dominant, mixed, and hyperopic-dominant groups.

Key Outcome Parameters for Each Diopter Bin for Cylinder Treateda

Table A:

Key Outcome Parameters for Each Diopter Bin for Cylinder Treated

Key Outcome Parameters for WTR (0° to 30° and 150° to 180°) and ATR/Oblique (31° to 149°) Cylinder and Subgroupsa

Table B:

Key Outcome Parameters for WTR (0° to 30° and 150° to 180°) and ATR/Oblique (31° to 149°) Cylinder and Subgroups

Target induced astigmatism vs surgically induced astigmatism scatter plots for the subgroups of myopic-dominant (n = 41), mixed (n = 41), and hyperopic-dominant (n = 23) mixed astigmatism. The slope of the regression line was higher for the mixed and hyperopic-dominant groups compared to the myopic-dominant group. D = diopters

Figure 4.

Target induced astigmatism vs surgically induced astigmatism scatter plots for the subgroups of myopic-dominant (n = 41), mixed (n = 41), and hyperopic-dominant (n = 23) mixed astigmatism. The slope of the regression line was higher for the mixed and hyperopic-dominant groups compared to the myopic-dominant group. D = diopters

Safety and Complications

Table 3 includes the normalized mesopic contrast sensitivity data before and after surgery showing that there was a small but statistically significant increase at 3, 6, 12, and 18 cycles per degree (cpd). The ATLAS average keratometry changed from 43.41 ± 1.40 D (range: 39.47 to 46.98 D) preoperatively to 43.15 ± 1.75 D (range: 38.22 to 47.19 D) at 3 months and 43.01 ± 1.66 D (range: 37.95 to 47.01 D) at 12 months postoperatively. Corneal astigmatism changed from 2.26 ± 1.35 D (range: 0.13 to 6.13 D) preoperatively to 0.84 ± 0.48 D (range: 0.02 to 2.17 D) at 3 months and 0.80 ± 0.45 D (range: 0.90 to 1.83 D) at 12 months postoperatively.

Change in Contrast Sensitivity (CSV-1000) in log unitsa

Table 3:

Change in Contrast Sensitivity (CSV-1000) in log units

There were 5 cases (4.7%) of a mild peripheral epithelial defect, which were managed with a bandage contact lens. The bandage contact lens was removed at the 1-day postoperative appointment in all cases with no consequence or sequelae. Two eyes lost one line of CDVA at 1 year, but this was unrelated to the epithelial defect. There was one case (0.9%) of a small buttonhole in the superior periphery, which had no adverse effect on the outcome and no change in CDVA. There were no intraoperative complications.

Table 4 summarizes the incidence of postoperative complications as measured at the 3-month postoperative appointment. There were two cases of grade I diffuse lamellar keratitis on day 1 after surgery. These were managed successfully using the standard protocol of prednisolone acetate drops every 2 hours, with no sequelae and no change in CDVA. There were no visually significant complications (grades III to V). At day 1, a minor flap adjustment was made at the slit lamp in 8 eyes (7.5%) to optimize the flap positioning after the flap had returned to its natural hydration state overnight.

Postoperative Complications at 3 Months

Table 4:

Postoperative Complications at 3 Months

Discussion

One-year outcomes of LASIK using the MEL 90 laser for mixed cylinder up to 7.00 D demonstrated excellent efficacy, predictability, and safety. Almost three-quarters of eyes achieved a UDVA of 20/20 or better and 94% eyes were 20/40 or better 1 year after surgery, relative to 81% with CDVA of 20/20 or better before surgery. Overall residual refractive cylinder was 0.50 D or less in 64% of eyes and 1.00 D or less in 90% of eyes. High treatment safety was confirmed because no eye lost two or more lines CDVA, and there was even a slight increase in mesopic contrast sensitivity.

An overcorrection, in terms of cylinder magnitude, was identified by the TIA versus SIA scatter plot and the subgroup analysis. The angle of error histogram showed that the cylinder treatment was applied accurately on the intended axis. The subgroup analysis for with-the-rule and against-the-rule treatments showed little difference in outcomes; there was a significant difference in the postoperative cylinder of 0.50 D or less, but this was due to the higher corrections included in the with-the-rule group (mean cylinder treated was −3.50 D compared to −2.38 D). Therefore, the inaccuracy of the cylinder treatment could be isolated to the magnitude effect. This analysis indicates that a nomogram to apply a 12% reduction in cylinder is required for mixed cylinder treatments with the Triple-A profile on the MEL 90 laser.

Subgroup analysis by weighting between the myopic and hyperopic cylinder components showed that there may be a small difference between myopic-dominant and mixed or hyperopic-dominant cases, with the regression line slope increasing from myopic-dominant (1.116) to mixed (1.145) to hyperopic-dominant (1.166). Forcing the regression lines through zero increases this difference to 1.088 for myopic-dominant and 1.159 for mixed and hyperopic-dominant. Similarly, the correction index geometric means were 1.06 for myopic-dominant, 1.16 for mixed, and 1.13 for hyperopic-dominant cases. This result may be related to the balance of coupling effects from the myopic and hyperopic components. Further analysis might be performed to quantify the coupling effects more precisely, as described by Alpins et al.9 However, this is complicated by the fact that the Triple-A profile is a single combined profile rather than explicit bitoric components. Alternatively, a more complex multivariate nomogram analysis might be performed, such as that described by Patel el al.40

The safety in terms of loss of one line of CDVA appeared to show a trend for being more prevalent for lower corrections. This may be related to the higher mean age for the lower corrections. This result is also skewed by the relatively low number of eyes in each group, and also because the analysis was performed to the nearest whole line rather than to the nearest letter. Of the 6 eyes that lost one line for cylinder treated between 0.75 and 2.00 D, the change in CDVA was less than five letters in 4 eyes. Of the 2 remaining eyes, both were 20/12.5 before surgery. There was one eye in the high correction group where the CDVA was worse than 20/20 after surgery (excluding amblyopic eyes), but this was a loss of only two letters from 20/20−1 to 20/25+2. It was also notable that there were no eyes that lost one line in the myopic-dominant group, but this may be related to the minification effect and younger age.

To compare the current study to published LASIK studies, a literature review was performed using the search terms “mixed cylinder LASIK” and “mixed astigmatism LASIK” in PubMed, and referring to the database of the U.S. Food and Drug Administration premarket approval studies. The main outcome parameters are shown in Table C (available in the online version of this article) for the 18 studies where outcomes for a mixed cylinder population were available (ie, studies that included mixed cylinder cases together with myopic or hyperopic cases were excluded).2–9,11,14–22 The residual refractive cylinder within ±0.50 D ranged between 57% and 100%, relative to 65% as found in the current study. Had a nomogram been applied to the laser cylinder, this would have theoretically been improved to 84%. UDVA of 20/20 or better ranged between 18% and 100%, relative to 73% as found in the current study. However, UDVA results were difficult to compare due to significant differences in the preoperative CDVA between studies. For safety, the loss of two lines of CDVA ranged between 0.00% and 14%, with no loss of two lines found in the current study. Comparison between studies was also challenging due to the small population of many studies.

Literature Review of Studies Reporting Outcomes of LASIK for Mixed Cylinder

Table C:

Literature Review of Studies Reporting Outcomes of LASIK for Mixed Cylinder

The current study found the 1-year outcomes of LASIK using the Triple-A ablation profile and the MEL 90 laser for mixed cylinder up to −7.00 D to have excellent efficacy, safety, and predictability. Vector analysis found a 12% overcorrection in magnitude and, given the high accuracy for angle of error, the results could be improved by application of a nomogram, which is intended.

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  28. Chen Y, Yang D, Han T, Xu H, Li M, Zhou X. A pilot study: LASEK with the Triple-A profile of a MEL 90 for mild and moderate myopia. BMC Ophthalmol. 2017;17:98. doi:10.1186/s12886-017-0493-4 [CrossRef]
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  30. Blum M, Kunert K, Gille A, Sekundo W. LASIK for myopia using the Zeiss VisuMax femtosecond laser and MEL 80 excimer laser. J Refract Surg. 2009;25:350–356. doi:10.3928/1081597X-20090401-01 [CrossRef]
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  33. Mastropasqua L, Calienno R, Lanzini M, et al. Opaque bubble layer incidence in femtosecond laser-assisted LASIK: comparison among different flap design parameters. Int Ophthalmol. 2017;37:635–641. doi:10.1007/s10792-016-0323-3 [CrossRef]
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  36. Reinstein DZ, Carp GI, de Benedictis D, et al. Standardization of LASIK surgical technique evaluated by comparison of procedure time between two experienced surgeons. J Cataract Refract Surg. 2015;41:1004–1008. doi:10.1016/j.jcrs.2014.08.039 [CrossRef]
  37. Reinstein DZ, Couch DG, Archer TJ. LASIK for hyperopic astigmatism and presbyopia using micro-monovision with the Carl Zeiss Meditec MEL80. J Refract Surg. 2009;25:37–58.
  38. Reinstein DZ, Archer TJ, Randleman JB. JRS standard for reporting astigmatism outcomes of refractive surgery. J Refract Surg. 2014;30:654–659. Erratum in: J Refract Surg. 2015;31:129. doi:10.3928/1081597X-20140903-01 [CrossRef]
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  40. Patel S, Bohac M, Biscevic A, Koncarevic M, Anticic M, Gabric N. A critical evaluation of refractive outcomes following LASIK for moderate to high astigmatism using two excimer laser platforms. J Refract Surg. 2017;33:104–109. doi:10.3928/1081597X-20161102-01 [CrossRef]

Study Demographics

CharacteristicValuea
Eyes (patients)105 (84)
Age (y)40 ± 11 (18 to 65)
Gender (M/F) (%)66/34
Attempted sphere (D)+1.17 ± 0.99 (+0.05 to +4.25)
Attempted refractive cylinder (D)−2.93 ± 1.47 (−0.75 to −7.00)
Attempted spherical equivalent refraction (D)−0.30 ± 0.90 (−2.30 to +1.75)
CDVA62% t 20/16; 97% t 20/20
Follow-up90% 12 months; 10% 3 months
Preoperative minimum corneal thickness (μm)536 ± 33 (429 to 612)
Scotopic pupil diameter (mm)5.37 ± 0.99 (2.28 to 7.07)
Postoperative sphere relative to intended target (D)−0.07 ± 0.38 (−1.25 to +0.62)
Postoperative cylinder (D)−0.55 ± 0.41 (0.00 to −1.75)
Postoperative spherical equivalent relative to intended target (D)−0.20 ± 0.36 (−1.25 to +0.64)

Vector Analysis of Refractive Cylinder

ParameterValuea
Target induced astigmatism vector (D)
  Arithmetic mean2.93 ± 1.47 (0.75 to 7.00)
  Summated vector mean0.66 Ax 169
Surgically induced astigmatism vector (D)
  Arithmetic mean3.30 ± 1.69 (0.68 to 7.86)
  Summated vector mean0.72 Ax 165
Correction index – geometric mean1.12 (0.68 to 1.61)
Difference vector (D)
  Arithmetic mean0.57 ± 0.41 (0.00 to 1.98)
  Summated vector mean0.11 Ax 49
Index of success – geometric mean0.25 (0.00 to 0.71)
Angle of error (°)
  Arithmetic mean−0.4 ± 4.2 (−13.5 to 9.5)
  Absolute mean2.9 ± 3.0 (0.0 to 13.5)

Change in Contrast Sensitivity (CSV-1000) in log unitsa

Parameter3 cpd6 cpd12 cpd18 cpd
Preoperative1.55 ± 0.19 (0.70 to 1.93)1.77 ± 0.22 (0.91 to 2.29)1.40 ± 0.26 (0.61 to 1.84)0.95 ± 0.27 (0.17 to 1.40)
Change0.09 ± 0.17 (−0.29 to 0.93)0.05 ± 0.17 (−0.44 to 0.64)0.08 ± 0.20 (−0.47 to 0.49)0.06 ± 0.19 (−0.46 to 0.63)
P< .01< .01< .01< .01
Contrast increase > 0.2 log units14.9%11.9%22.8%19.8%
Contrast decrease > 0.2 log units1.0%4.0%5.9%4.0%

Postoperative Complications at 3 Months

ComplicationNilTraceGrade I
Microfolds97.2%2.8%
Epithelial ingrowth95.3%4.7%
SPK81.1%16.0%2.8%
Interface haze91.5%6.6%1.9%
Infection100.0%
Interface debris97.2%2.8%
DLK (day 1)98.1%1.9%

Key Outcome Parameters for Each Diopter Bin for Cylinder Treateda

ParameterRefractive Cylinder Magnitude Range (D)

0.75 to 1.001.25 to 2.002.25 to 3.003.25 to 4.004.25 to 5.005.25 to 7.00
Eyes112724191311
Age (years)51 ± 7 (34 to 61)43 ± 13 (21 to 66)39 ± 10 (21 to 63)36 ± 8 (24 to 52)32 ± 11 (21 to 53)40 ± 8 (28 to 53)
Attempted spherical equivalent refraction (D)+0.04 ± 0.19 (−0.25 to +0.25)−0.09 ± 0.51 (−0.80 to +0.75)−0.26 ± 0.78 (−1.45 to −1.19)−0.45 ± 0.88 (−1.75 to +1.08)−0.59 ± 1.44 (−2.00 to +1.75)−0.63 ± 1.37 (−2.30 to +1.38)
Attempted sphere (D)+0.51 ± 0.21 (+0.24 to +0.75)+0.76 ± 0.49 (+0.10 to +1.75)+1.05 ± 0.79 (+0.05 to +2.50)+1.29 ± 0.83 (+0.15 to +2.70)+1.69 ± 1.47 (+0.30 to +4.25)+2.25 ± 1.27 (+0.70 to +4.00)
Attempted refractive cylinder (D)−0.93 ± 0.12 (−0.75 to −1.00)−1.69 ± 0.26 (−1.25 to −2.00)−2.63 ± 0.30 (−2.25 to −3.00)−3.49 ± 0.31 (−3.25 to −4.00)−4.56 ± 0.33 (−4.25 to −5.00)−5.75 ± 0.52 (−5.25 to −7.00)
UDVA / CDVA 20/20 or better (eyes intended plano)88%/100% (8)85%/90% (20)89%/94% (18)75%/88% (16)55%/64% (11)13%/50% (8)
Postop spherical equivalent refraction within ±0.50 D of target91%89%75%95%77%82%
Postop cylinder 0.50 D or less100%85%63%58%46%18%
Loss one line CDVA18%15%4%5%0.0%18%
Loss two or more lines CDVA0.0%0.0%0.0%0.0%0.0%0.0%
Postoperative CDVA 20/20 or better (eyes preoperative CDVA 20/20 or better)100% (11)100% (25)100% (22)100% (15)100% (7)80% (5)
Difference vector magnitude (D)0.25 ± 0.19 (0.00 to 0.50)0.42 ± 0.27 (0.00 to 1.25)0.52 ± 0.34 (0.00 to 1.25)0.63 ± 0.30 (0.00 to 1.25)0.67 ± 0.52 (0.00 to 1.75)1.08 ± 0.51 (0.25 to 1.98)
Angle of error (°) – absolute4.0 ± 4.9 (0.0 to 13.5)3.3 ± 3.4 (0.0 to 10.9)3.0 ± 2.8 (0.0 to 9.0)2.8 ± 1.9 (0.0 to 6.2)1.7 ± 2.5 (0.0 to 8.4)2.3 ± 2.2 (0.0 to 6.9)
Correction index (geometric mean)1.061.131.131.111.091.15

Key Outcome Parameters for WTR (0° to 30° and 150° to 180°) and ATR/Oblique (31° to 149°) Cylinder and Subgroupsa

ParameterWTRATR/ObliqueMyopic-DominantMixedHyperopic-Dominant
Eyes5253414123
Age (y)38 ± 11 (21 to 63)42 ± 11 (21 to 66)37 ± 9 (21 to 63)41 ± 12 (21 to 64)43 ± 12 (21 to 66)
Attempted spherical equivalent refraction (D)−0.31 ± 0.96 (−2.30 to +1.75)−0.28 ± 0.84 (−2.00 to +1.19)−1.18 ± 0.55 (−2.30 to −0.25)−0.02 ± 0.41 (−0.75 to +1.25)+0.77 ± 1.07 (+0.25 to +1.75)
Attempted sphere (D)+1.43 ± 1.17 (+0.10 to +4.25)+0.91 ± 0.69 (+0.05 to +3.00)+0.47 ± 0.30 (+0.05 to +1.50)+1.38 ± 0.93 (+0.24 to +4.00)+2.03 ± 1.07 (+0.75 to +4.25)
Attempted refractive cylinder (D)−3.50 ± 1.59 (−0.75 to −7.00)−2.38 ± 1.11 (−0.75 to −5.50)−3.30 ± 1.45 (−1.00 to −7.00)−2.80 ± 1.51 (−0.75 to −6.00)−2.51 ± 1.33 (−1.00 to −5.25)
Refractive cylinder axis (WTR/ATR)100%/0%0%/100%51%/49%54%/46%51%/49%
UDVA/CDVA 20/20 or better (eyes intended plano)66%/78% (41)80%/90% (40)78%/84% (37)67%/87% (30)71%/79% (14)
Postop spherical equivalent refraction within ±0.50 D of target83%87%85%88%78%
Postop cylinder ≤0.50 D58%72%68%59%70%
Loss of one line of CDVA10%9%0.0%15%17%
Loss of two or more lines of CDVA0.0%0.0%0.0%0.0%0.0%
Difference vector magnitude (D)0.63 ± 0.48 (0.00 to 1.98)0.51 ± 0.32 (0.00 to 1.25)0.55 ± 0.43 (0.00 to 1.75)0.61 ± 0.41 (0.00 to 1.98)0.51 ± 0.38 (0.00 to 1.25)
Angle of error (°) – absolute2.8 ± 3.1 (0.0 to 13.5)3.0 ± 2.9 (0.0 to 10.9)2.8 ± 2.8 (0.0 to 8.9)3.3 ± 3.5 (0.0 to 13.5)2.4 ± 2.5 (0.0 to 9.0)
TIA vs SIA regression line (slope with intercept zero)1.135x – 0.063 (1.120)1.123x + 0.042 (1.137)1.116x – 0.113(1.088)1.145x + 0.051 (1.159)1.166x – 0.023 (1.159)
Correction index (geometric mean)1.101.141.061.161.13

Literature Review of Studies Reporting Outcomes of LASIK for Mixed Cylinder

PublicationEyesLaserAge (y)Preop Sphere (D)Preop Cyl (D)F/U (Mo)SEQ ± 0.50 DPostop Cyl (D)Cyl ± 0.50 DCyl ± 1.00 DPreop CDVA 20/20Postop UDVA 20/20Postop UDVA 20/40≥2 Lines CDVA Loss
Chayet et al., 2001247EC-500032 NR+1.31 ± 0.95 (NR)−4.02 ± 1.22 (−1.50 to −6.25)1292%−0.35 ± 0.42 (0.00 to −1.25)NRNR57%68%98%0.00%
FDA, 200121110Star S2 and S341 ± 11 (21 to 68)NR (Up to +5.00)−3.10 (−0.80 to −6.30)677%NR63%89%NR62%99%0.00%
Salz et al., 20021757LADARVision53 ± 10 (21 to 74)+1.85 ± 1.35 (+0.25 to +5.00)−3.26 ± 1.49 (−1.25 to −6.00)665%0.55 ± 0.49 (DV)NRNR75%46%93%1.9%
Rueda et al., 2002323EC-500026 ± 7 (18 to 43)NR−3.38 ± 1.10 (−1.50 to −6.00)650%−0.59 ± 0.46 (0.00 to −1.50)NRNRNR18%NRNR
Hassaballa et al., 20031515217C Bitoric36 (22 to 49)NR−4.05 ± 0.68667%−0.76 ± 0.57 (NR)NRNRNRNRNR7.0%
15217C Monotoric36 (22 to 49)NR−2.80 ± 1.0060%−0.98 ± 0.60 (NR)NRNRNRNRNR14.0%
Albarran-Diego et al., 200442821734 ± 6 (21 to 47)NR (+2.00 to +4.00)−4.04 ± 1.13 (−2.00 to −6.00)664% (DEQ)−0.67 ± 0.79 (0.00 to −3.00)57%82%18%21%79%0.00%
Jin et al., 20051664LADARVision 400039 ± 12 (20 to 68)+1.14 ± 0.84 (NR)−2.75 ± 0.89 (−1.50 to −5.00)1286%−0.54 ± 0.44NR98%NR56%97%1.6%
Pinelli et al., 2006114021740 ± 15 (21 to 65)NR (+0.50 to +3.00)NR (−1.75 to −6.00)1288%0.00 to −1.0080%100%NRNRNR0.00%
FDA, 200620111Allegretto WAVE39 ± 9 (22 to 70)NR (Up to +5.00)−2.44 ± 1.10 (Up to −6.00)691%NR78%92%NR69%97%0.9%
de Ortueta et al., 2008619ESIRIS40 (21 to 66)+1.63 ± 1.23 (0.00 to +4.00)−3.55 ± 1.17 (−1.25 to −5.25)3100%−0.45 ± 0.31 (0.00 to −1.00)85%100%31%26%89%0.00%
Khalifa et al., 2009520Star S4 Conventional23+1.67 ± 1.32 (NR)−2.79 ± 2.24 (NR)365%NR60%70%NR65%NR10%
20Star S4 WFG24 (NR)+1.27 ± 0.60 (NR)−3.35 ± 1.48 (NR)70%NR65%70%NR70%NR0.00%
20Star S4 WFG+IR25 (NR)+1.00 ± 1.69 (NR)−2.50 ± 5.60 (NR)80%NR80%100%NR90%100%0.00%
Stonecipher et al., 20107111Allegretto WAVE 200-Hz37NR−1.06 ± 0.90 (Up to −3.33)3100%NR100%100%NR79%100%0.00%
26Allegretto WAVE 400-Hz(20 to 58)NR−2.55 ± 0.15 (Up to −2.66)100%NR100%100%NR81%100%0.00%
Tanzer et al., 20131849Customvue36NRNR3NRNR -NRNR100%100%100%0.00%
Alió et al., 20131452Amaris(21 to 53)+2.41 ± 1.26 (+0.25 to +5.00)−3.89 ± 0.70 (−3.00 to −5.25)327%1.11 ± 0.67 (0.00 to −3.50)NRNRNRNR85%5.8%
Bohac et al., 20141961Allegretto Eye-Q33 ± 7 (20 to 58)+2.72 ± 1.79 (+0.25 to +7.00)−3.84 ± 1.21 (−2.00 to −6.50)12NR−0.85 ± 0.41 (0.00 to −2.00)NRNRNRNRNR0.00%
111Amaris+3.11 ± 1.57 (+0.50 to +7.50)−3.66 ± 1.16 (−2.00 to −7.00)−0.58 ± 0.38 (0.00 to −1.50)
Kilavuzoglu et al., 2016819Allegretto Eye-Q36 ± 13 (22 to 66)+1.58 ± 1.02 (0.25 to +4.25)−3.19 ± 1.19 (−1.25 to −5.25)174%−0.59 ± 0.74 (NR)37%78%NR32%93%5.2%
23217z34 ± 9 (22 to 66)+1.67 ± 1.43 (+0.25 to +5.25)−3.62 ± 1.42 (−1.50 to −6.75)−0.81 ± 0.44 (NR)42%83%30%90%0.00%
U.S. FDA, 201622149Star S436 ± 10 (18 to 58)NR−2.99 ± 1.16 (−0.75 ± −6.00)391%−0.29 ± 0.29 (NR)NRNR100%92%100%0.00%
Alpins et al., 201713242Star S439 ± 10 (20 to 62)NR−2.72 ± 1.13 (−0.75 to −6.00)1 to 1271%NR68%89%63%38%99%6%
Current105MEL 9040 ± 11 (21 to 66)+1.17 ± 0.99 (+0.05 to +4.25)−2.93 ± 1.47 (−0.75 to −7.00)1285%−0.55 ± 0.41 (0.00 to −1.75)65%90%84%73%94%0.00%
Authors

From London Vision Clinic, London, United Kingdom (DZR, GIC, TJA, ACD, RSV); the Department of Ophthalmology, Columbia University Medical Center, New York, New York (DZR); Centre Hospitalier National d'Ophtalmologie, Paris, France (DZR); and Biomedical Science Research Institute, University of Ulster, Coleraine, Northern Ireland (DZR, TJA).

Dr. Reinstein is a consultant for Carl Zeiss Meditec (Jena, Germany) and has a proprietary interest in the Artemis technology (ArcScan, Inc., Golden, Colorado) through patents administered by the Center for Technology Licensing at Cornell University (CTL), Ithaca, New York. Drs. Carp and Archer receive travel expenses from Carl Zeiss Meditec. The remaining authors have no proprietary or financial interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (DZR, GIC, TJA); data collection (DZR, GIC, TJA); analysis and interpretation of data (DZR, GIC, TJA, ACD, RSV); writing the manuscript (DZR, TJA, ACD); critical revision of the manuscript (GIC, RSV); statistical expertise (DZR, TJA)

Correspondence: Dan Z. Reinstein, MD, MA(Cantab), FRCSC, London Vision Clinic, 138 Harley Street, London W1G 7LA, United Kingdom. E-mail: dzr@londonvisionclinic.com

Received: March 01, 2018
Accepted: July 25, 2018

10.3928/1081597X-20180814-01

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