LASIK is designed to modify the central corneal curvature, specifically making it flatter for myopia correction or steeper for hyperopia correction.1 However, this surgery may increase higher order aberrations, which is highly correlated with the development of glare, starbursts, double vision, and other visual symptoms.2 The evolution of LASIK technology, such as wavefront-guided lasers and topography-guided lasers,3–6 can minimize the induction of higher order aberrations, potentially resulting in fewer adverse effects.
Over the years, evaluation of LASIK outcomes has predominately focused on objective measures, such as efficacy, safety, predictability, stability, contrast sensitivity, and higher order aberrations. The success of LASIK was evaluated by how much these measurements improved from before to after surgery. However, some studies show that despite excellent results in visual outcomes, new symptoms of dryness, glare, and halos may negatively impact the patient's quality of life.7 Patients evaluate the success of LASIK by the quality of their vision, not the objective criteria we as physicians have constructed. Therefore, patient-reported outcomes must be included to properly measure the success of LASIK.
To our knowledge, there is no study evaluating the submitted U.S. Food and Drug Administration (FDA) data on patient-reported outcomes for the three latest FDA-approved platforms for LASIK. Therefore, the aim of this study was to analyze the impact of modern lasers on patient-reported outcomes with regard to changes in visual symptoms, quality of life, and satisfaction rates. These outcomes were measured following refractive surgery for myopia and astigmatism correction using the iDesign Advanced WaveScan wavefront-guided technology (Abbott Medical Optics Manufacturing, Milpitas, CA), Allegro Topolyzer topography system (Alcon Laboratories, Inc., Fort Worth, TX), and Nidek topography system (Nidek Co. Ltd., Gamagori, Japan).
Patients and Methods
This was a retrospective meta-analysis of the submitted FDA summary of safety and effectiveness data from the three latest approved LASIK platforms: STAR S4 IR Excimer Laser with iDesign Advanced WaveScan Studio System (P930016/S044),8 Allegretto Wave Eye-Q Laser System with Allegro Topolyzer topography system and T-CAT treatment planning software (P020050/S12),9 and Nidek EC-5000 Excimer Laser System with topography-assisted LASIK treatment using the Final Fit custom ablation treatment planning software (P970053/S011).10 In this study, the excimer lasers will be referred to as iDesign, Contoura, and CATz, respectively. The combined demographics of the three platforms used in this study are as follows. A total of 718 eyes from 250 men and 280 women (age: 33.4 ± 8.7 years) were assessed. The preoperative mean spherical equivalent was −5.15 ± 2.67 diopters.
Primary visual outcomes of efficacy and safety were assessed first by pooling the data from the three lasers to assess postoperative changes at 3 and 12 months for both variables. Efficacy outcomes were evaluated by assessing cumulative postoperative uncorrected distance visual acuity (UDVA), and safety outcomes were evaluated by comparing the change in lines of corrected distance visual acuity (CDVA) from preoperative to postoperative measurements.
At 6 months, patients from all three platforms were pooled for each visual symptom to evaluate postoperative changes. None and mild symptoms were grouped into one category, whereas moderate to severe symptoms were grouped into a second category. The visual symptoms assessed included: light sensitivity, difficulty driving at night, reading difficulty, double vision, fluctuation in vision, glare, halos, dryness, pain, and foreign body sensation. Some symptoms were not reported by specific platforms in the FDA report and were therefore excluded from the particular analysis. The percent change was calculated for statistical significance.
We further evaluated the most common symptoms causing dissatisfaction after LASIK,9 which included difficulty driving at night, glare, halos, and dryness. The symptoms were measured for changes over time. The time periods included preoperative 3, 6, and 12 months and 3, 6, and 12 months postoperative.
Finally, we measured the changes in the total prevalence of the symptom and changes in moderate to severe symptoms from the preoperative to 12-month postoperative intervals. Total prevalence decreased when the number of “none” symptoms increased and vice versa. The percent change was calculated for statistical significance.
Statistical analysis and graph plotting were performed with the help of Microsoft Excel 2015 and STATA version 14 software (College Station, TX). McNemar's test was used to determine whether the change in proportion before and after surgery was significant. A P value less than .05 was considered statistically significant.
Efficacy and Safety Visual Outcomes
Efficacy. At 12 months postoperatively, the new ablation platforms achieved a UDVA of 20/20 or better in 86% of eyes (Figure 1A). The three platforms achieved a UDVA of 20/12.5 or better in 24% of eyes at 12 months (Figure 1A). Nearly all eyes using the three lasers achieved a UDVA of 20/40 or better, far exceeding the FDA cut-off for efficacy (Figure 1A). Eighty percent of eyes had UDVA at 12 months that was equal to or better than the CDVA preoperatively (Figure 1B).
Visual outcomes. (A) The cumulative uncorrected distance visual acuity (UDVA) at 12 months postoperatively. (B) The difference in UDVA at 12 months postoperatively from corrected distance visual acuity (CDVA) preoperatively. (C) The change in CDVA at 12 months postoperatively. (D) The accuracy of spherical equivalent refraction (SEQ) to intended target. D = diopters
Safety. No eye lost two or more lines of CDVA at the 12-month postoperative follow-up compared to preoperative CDVA (Figure 1C), exceeding the FDA criteria for safety. At 12 months, 4% of eyes lost one line of CDVA compared to preoperative CDVA (Figure 1C). Approximately 48% of eyes gained at least one line of CDVA (Figure 1C). Ninety-six percent of eyes were within ±1.00 D of their intended target 12 months postoperatively (Figure 1D).
Patient-Reported Visual Symptoms
Light Sensitivity. Of the patients who had moderate to severe symptoms preoperatively, 4% reported a reduction of light sensitivity at the 6-month interval after surgery (P = .23) (Figure 2A). At 12 months postoperatively, 11% of patients reported complete resolution from preoperative symptoms (P = .11) (Figure AA, available in the online version of this article) and 9% of patients reported reduction from preoperative moderate to severe symptoms (P = .004) (Figure AB).
Changes in visual symptoms from preoperatively to 6 months postoperatively. (A) Light sensitivity. (B) Difficulty driving at night. (C) Reading difficulty. (D) Double vision. (E) Fluctuation in vision. (F) Glare. (G) Halos. (H) Dryness. (I) Pain. (J) Foreign body sensation.
Summary of changes that occurred from preoperative to 12 months. (A) Increase or decrease in prevalence of a symptom at 12 months. Decrease in prevalence is indicated by a negative bar. More patients reported no symptoms postoperatively. (B) Postoperative reduction in moderate to severe symptoms at 12 months. A reduction is indicated by a negative bar. Fewer patients complained of moderate to severe symptoms at 12 months than they did preoperatively.
Difficulty Driving at Night. The number of patients with mild or no symptoms increased (17%) 6 months after surgery (P < .001) (Figure 2B). There was also a significant decrease (10%) in the number of patients with moderate to severe symptoms from preoperatively to the 6-month interval (P < .001). There was a general trend of patients reporting more resolution and reduced moderate to severe symptoms as time progressed (Figure 3A).
Changes in visual symptoms over time for (A) difficulty driving at night, (B) glare, (C) halos, and (D) dryness.
At 12 months postoperatively, 29% of patients reported complete resolution (P < .001) of symptoms they had preoperatively and 22% reported a reduction in moderate to severe preoperative symptoms of difficulty driving at night (P < .001) (Figure 3A). LASIK had a greater effect on alleviating this symptom than any other symptom measured in this study.
Reading Difficulty. There were no statistically significant differences in moderate to severe symptoms of reading difficulty between the preoperative and 6-month postoperative intervals (P = .13) (Figure 2C). There was no statistically significant difference in the resolution of reading difficulty from the preoperative to 12-month postoperative follow-up (P = .27) (Figure AA). However, there was a significant alleviation (8%) of preoperative moderate to severe symptoms (P = .007) (Figure AB).
Double Vision. At the 6-month and 12-month postoperative intervals, there was no statistically significant reduction in baseline moderate to severe symptoms (P = .16) (Figure 2D, Figure AA).
Fluctuation in Vision. There were no statistically significant changes in the fluctuation in vision measurements from the preoperative to 6- and 12-month postoperative follow-up periods (Figure 2E, Figure AA).
Glare. There was no statistically significant difference in moderate to severe symptoms of glare from the preoperative interval to 6 months postoperatively (P = .06) (Figure 2F). As time progressed, the number of patients reporting complete resolution of glare increased and the number of patients with moderate to severe symptoms decreased (Figure 3B).
At 12 months postoperatively, there was no statistically significant resolution of preoperative glare (P = .88) (Figure A). However, patients reported a statistically significant reduction (12%) in moderate to severe glare that was present at the preoperative stage (P < .001).
Halos. There were no statistically significant changes in moderate to severe symptoms from the preoperative to 6-month postoperative intervals (Figure 2G). Between 3 and 12 months, the prevalence of halos decreased (Figure 3C). There was a slight increase in the number of mild symptoms at 6 and 12 months postoperatively compared to preoperative levels (Figure 3C).
At 12 months postoperatively, there was a significant reduction (6%) in preoperative baseline moderate to severe symptoms (P = .018) (Figure 3A). However, there was no statistically significant change in the prevalence of halos at this interval (Figure AB).
Dryness. No significant changes were seen at the 6-month interval, although there was a brief increase in dryness that later resolved (Figure 2H). The number of patients with dryness decreased with time, illustrating that most symptoms of dryness were transient and improved at a subsequent period (Figure AD). At 12 months postoperatively, there was no statistically significant resolution of preoperative dryness (P = .27) and no significant reduction in moderate to severe pre-operative dryness (P = .08) (Figure A).
Pain. There were no significant changes in pain from before to after surgery at the 6-month (Figure 2I) or 12-month (Figure A) intervals.
Foreign Body Sensation. There were no significant postoperative changes in foreign body sensation (Figure 2J, Figure A).
Patient-reported outcomes are fundamental to refractive surgery analysis and have become an important quality measure for FDA trials. In our meta-analysis, we found that the new FDA-approved lasers significantly improved moderate to severe symptoms postoperatively. These symptoms included light sensitivity, difficulty driving at night, reading difficulty, glare, and halos at the 12-month postoperative interval. In particular, patients reported the greatest alleviation from difficulty driving at night, with 29% of patients reporting complete resolution and 22% of patients reporting reduction of moderate to severe symptoms 12 months after surgery. Furthermore, we found that the new platforms were excellent at completely resolving light sensitivity, difficulty driving at night, and reading difficulty in 11%, 29%, and 9% of patients, respectively. There was no statistically significant report of new visual symptoms from preoperative measurements to the 12-month postoperative interval. Interestingly, when we analyzed the four most common symptoms causing dissatisfaction with LASIK12 (dry eyes, halos, glare, and difficulty driving at night), we found that generally all symptoms showed remarkable improvement with time.
Dry eyes are the leading cause of patient complaints following LASIK.11 In our analysis, there was a slight increase in new cases of dryness after surgery. However, this increase was predominately mild. We also found that most symptoms of dryness had completely resolved at 12 months. This is consistent with evidence from other literature suggesting that patients should expect a transient increase in dryness at an early period with subsequent resolution at a later period.12 Bower et al.9 showed that the number of LASIK participants developing chronic dry eyes is low (0.8%). This further indicates that most symptoms of dryness tend to resolve at a later period. Bower et al.9 also noticed that the incidence of chronic dry eyes has decreased over time. The improved outcome may be due to newer lasers, more predictable thinner flaps, and patients being closely observed. Overall, the most effective means to reduce LASIK-associated dryness is by careful examination to detect preoperative tear dysfunction and ocular surface disease.11
In 2007, Bailey and Zadnik13 performed a meta-analysis comparing 12 lasers approved by the FDA for LASIK between 1998 and 2004. They found that an average of 26%, 23%, 25%, and 23% of all eyes with postoperative symptoms of glare, halos, night driving problems, and dryness, respectively, were worse or severely worse than the preoperative condition. Our analysis shows that a significant proportion of patients reported an improvement in preoperative symptoms of higher severity. This large difference illustrates the technological advances of modern lasers in recent years to improve patient-reported visual symptoms after LASIK.
Ultimately, the success of LASIK is contingent on how satisfied patients are with their vision. We believe that patient-reported outcomes are an important index of LASIK. A systematic world literature review of LASIK conducted by Solomon et al.10 demonstrated that the majority of patients (95.4%) were satisfied with their results. The patients who were dissatisfied often experienced worsening visual symptoms or residual refractive error.10 Therefore, reducing preoperative visual symptoms and minimizing the incidence of new visual symptoms can play a significant role in improving patient satisfaction after LASIK. In our analysis, we found 92% to 98% (96.3% average) of patients were satisfied with their correction. However, this measurement was taken after many patients were lost to follow-up. Thus, this percentage, although consistent with prior literature, may not be an accurate representation of patient satisfaction with modern lasers.
Limitations to our study are consistent with limitations in all studies that involve a meta-analysis. The primary limitation was difficulty combining the results of the three FDA trials due to the heterogeneity of data collecting and reporting. In some instances, we were only able to combine results from two of the three platforms, such as the data used to construct Figure A. Furthermore, outcomes for visual symptoms were measured via two different methods for the three platforms. The FDA trial for the Contoura and CATz lasers used a subjective questionnaire form to fill out information for symptoms. In contrast, the trial for the iDesign laser used the physician–patient interview to gather the symptoms that were reported. Quality of life was also measured using two different questionnaires, impeding our ability to pool the results into a single measurement. The results of this analysis may also be influenced by the quality of the primary studies. For example, patients may underreport their postoperative visual symptoms, quality of life, or satisfaction with the procedure in an effort to please their physician (Hawthorne effect). Differences in baseline preoperative measurements may also affect the final result of the study. Although significantly improved from the past, we encourage submitted FDA studies to report results in a similar format and timeline to allow for more accurate analysis of the safety and effectiveness data of different platforms.
Overall, we found a significant reduction in preoperative symptoms of light sensitivity, difficulty driving at night, reading difficulty, glare, and halos. The decrease in the magnitude of preoperative symptoms was found to be higher than the increase in new visual symptoms after surgery. The three excimer lasers show superb efficacy and safety with visual outcomes and exceed the FDA criteria for these measurements. The combination of improved visual outcomes, excellent patient-reported outcomes, and high satisfaction may be attributed to modern lasers with improved ablation profiles, in conjunction with experienced surgeons and careful preoperative examinations, making LASIK a safe and effective procedure.
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- Sharma M, Wachler BS, Chan CC. Higher order aberrations and relative risk of symptoms after LASIK. J Refract Surg. 2007;23:252–256.
- Moshirfar M, Betts BS, Churgin DS, et al. A prospective, randomized, fellow eye comparison of WaveLight® Allegretto Wave ® Eye-Q versus VISX CustomVue STAR S4 IR™ in laser in situ keratomileusis (LASIK): analysis of visual outcomes and higher order aberrations. Clin Ophthalmol. 2011;5:1339–1347. doi:10.2147/OPTH.S24316 [CrossRef]
- Stonecipher KG, Kezirian GM. Wavefront-optimized versus wavefront-guided LASIK for myopic astigmatism with the ALLEGRETTO WAVE: three-month results of a prospective FDA trial. J Refract Surg. 2008;24:S424–S430.
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- Yu J, Chen H, Wang F. Patient satisfaction and visual symptoms after wavefront-guided and wavefront-optimized LASIK with the WaveLight platform. J Refract Surg. 2008;24:477–486.
- United States Food and Drug Administration. Summary of Safety and Effectiveness Data (P930016/S044). Available at: http://www.accessdata.fda.gov/cdrh_docs/pdf/P930016S044B.pdf. Accessed June 1st, 2016.
- Bower KS, Sia RK, Ryan DS, Mines MJ, Dartt DA. Chronic dry eye in photorefractive keratectomy and laser in situ keratomileusis: manifestations, incidence, and predictive factors. J Cataract Refract Surg. 2015;41:2624–2634. doi:10.1016/j.jcrs.2015.06.037 [CrossRef]
- Solomon KD, Fernández de Castro LE, Sandoval HP, et al. LASIK world literature review: quality of life and patient satisfaction. Ophthalmology. 2009;116:691–701. doi:10.1016/j.ophtha.2008.12.037 [CrossRef]
- Xie W. Recent advances in laser in situ keratomileusis-associated dry eye. Clin Exp Optom. 2016;99:107–112. doi:10.1111/cxo.12361 [CrossRef]
- Charles QY, Manche EE. Subjective quality of vision after myopic LASIK: prospective 1-year comparison of two wavefront-guided excimer lasers. J Refract Surg. 2016;32:224–229. doi:10.3928/1081597X-20151222-03 [CrossRef]
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