Incidence of Intraoperative and Early Postoperative Adverse Events in a Large Cohort of Consecutive Laser Vision Correction Treatments


To evaluate the incidence of adverse events (AE) following laser vision correction.


Retrospective case series.


Optical Express, UK. Patients/study population : patients who underwent laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between July 1, 2014, and June 30, 2016. Intervention/observation procedures : all AEs recorded in the electronic medical record were extracted and retrospectively reviewed. The total incidence of AE and serious adverse events (SAE) was calculated. Loss of 2 or more lines of corrected distance visual acuity (CDVA) was calculated for the entire cohort of patients that attended a minimum of 3 months follow-up. Main Outcome Measures : AEs; Preoperative and last available postoperative clinical data.


A total of 31,921 (61,833 eyes) were included in the study for LASIK and 5,016 (9,467 eyes) for PRK. The total number of AE was 850 for LASIK (occurring in 783 eyes of 657 patients; incidence of 1.3% or 1:79 eyes) and 227 for PRK (occurring in 218 eyes of 170 patients; incidence of 2.3% or 1:43 eyes). In the LASIK group, there were 287 SAEs (271 eyes of 226 patients; incidence of 0.4% or 1:228 eyes), and the number of SAEs in PRK group was 65 (65 eyes of 39 patients; incidence 0.7% or 1:146 eyes). Combining LASIK and PRK data, the loss of 2 or more lines of CDVA was recorded in 0.37% of eyes.


Contemporary LASIK and PRK are safe procedures with a low incidence of serious adverse events.

Modern laser vision correction (LVC) outcomes demonstrate excellent precision and a high rate of patient satisfaction. Given the large amount of published data, the expected visual outcomes for a wide range of refractive errors are well known. , Despite these reassuring numbers, the potential for complications that may ultimately lead to reduced best corrected visual acuity exist. A thorough understanding of the potential risks associated with LASIK and PRK is essential for treating physicians as well as prospective patients.

Although there are some recent large laser vision correction studies that discuss adverse event (AE) rates, , there is a need for better understanding of postoperative AEs as well as their impact on postoperative visual acuity. The aim of this study was to explore AEs and outcomes in a large multicenter clinical practice.

Subjects and Methods

This study was deemed exempt from full review by the Committee on Human Research (the institution-specific name for the Institutional Review Board) at the University of California San Francisco because the study used only retrospective deidentified patient data. All patients provided informed consent to undergo LASIK or PRK and agreed to the use of their deidentified data for statistical analysis.

All AEs following primary laser in situ keratomilousis (LASIK) and photorefractive keratectomy (PRK) of patients treated between July 1, 2014, and June 30, 2016, were extracted from Optical Express electronic database. An AE was defined as an event that had the potential to adversely affect patients’ visual outcomes and could be related to the refractive surgery. A list of AEs was created, and each AE was clearly defined ( Table 1 ). Subsequently, each AE was reviewed to ensure that all AEs were categorized correctly and in line with their definition. The list of AEs was derived from the US Food and Drug Administration clinical trials, although the list of AEs was expanded, and stringent criteria were used for the definition of some of the AEs to ensure that any event that could have a potentially negative impact on the patient’s outcome was captured.

Table 1

Definition of Adverse Events

AE Serious AE Definition
Abrasion Corneal abrasion that occurred in immediate postoperative period and was likely to be related to the surgical procedure.
Crystalline lens changes within 12M of LVC Yes Crystalline lens changes recorded in the first 12 postoperative months
CTK Yes Noninfectious dense opacification of the central corneal stroma associated with loss of stromal tissue, hyperopic shift, loss of CDVA and long recovery.
Corneal edema Yes Corneal edema persisting for longer than 1 month postoperative
Decentered ablation Yes Decentered ablation appearance on postoperative topography, causing visual symptoms and/or irregular astigmatism and/or loss of corrected visual acuity.
Delayed healing Epithelial defect persisting for longer than 2 weeks postoperatively
DLK grade 3 Diffuse lamellar keratitis graded based on clinical examination
DLK grade 4 Yes
Ectasia a Yes Progressive keratometric and topographic steepening, with or without central or paracentral corneal thinning, and associated corneal irregularity, myopic shift and/or induced astigmatism
Epithelial Ingrowth (required intervention) Yes Progressive epithelial ingrowth requiring surgical intervention
Epithelial ingrowth (stable) Epithelial ingrowth that required monitoring, but did not induce irregular astigmatism, topographic changes or cause visual symptoms.
Flap buttonhole Yes Intraoperative or postoperative complications evident during surgery or postoperative aftercare
Flap free
Flap incomplete Yes
Flap torn Yes
Flap traumatic displacement Yes
Flap melt Yes
Irregular flap Yes
Gas break-through during femtosecond flap creation Yes
Equipment failure during excimer laser ablation Yes
Suction loss Intraoperative suction loss that either resulted in change of the procedure to a surface ablation, or the procedure had to be aborted and rescheduled to a different day.
Flap lift (debris/fiber) Debris/fiber under flap discovered during early postoperative period and required a flap lift to remove.
Flap striae Yes Flap striae resulting in secondary procedure to correct the striae and/or a loss of vision or significant visual symptoms attributed to the striae.
Haze or scar Yes Haze/scar that persisted for longer than 1 month after LASIK or longer than 3 months after PRK and resulted either in a loss of CDVA and/or required a course of steroids and/or required a secondary surgical intervention to reduce haze, such as mitomycin C application.
Incorrect treatment Yes Incorrect treatment endpoint (aim), or incorrect procedure performed (e.g. conventional ablation instead of wavefront guided).
Elevated IOP Yes Elevated intraocular pressure greater than 21 mm Hg or >10 mm Hg over baseline persisting for longer than 1 week postoperatively
Microbial keratitis Yes Culture positive or probable culture negative microbial keratitis based on clinical findings.
Herpes simplex keratitis Yes Herpes simplex keratitis based on clinical findings
Recurrent erosions Repeated breakdown of epithelium, causing discomfort and/or photophobia, requiring management with either ocular surface lubrication or therapeutic contact lenses.
Retinal tear Yes Retinal tear diagnosed on dilated fundus examination, requiring treatment
Retinal detachment Yes Retinal detachment diagnosed on dilated fundus examination, requiring urgent treatment
Other posterior segment event Yes Posterior segment events including central serous retinopathy, pigment epithelium detachment of posterior vitreous detachment with formation of significant floaters
Sterile infiltrates Noninfectious corneal infiltrate(s)
Transient light sensitivity syndrome Transient light sensitivity diagnosed based on patients symptoms of light sensitivity with no obvious slit-lamp findings, treated with a course of steroid drops.

AE = adverse event; CDVA = corrected distance visual acuity; CTK = central toxic keratopathy; LASIK = laser in situ keratomileusis; PRK = photorefractive keratectomy.

a Ectasia after laser vision correction can take many years to manifest and it is only included here to maintain a comprehensive list of all AEs that occurred in our study population.

All treatments were performed using the VISX STAR S4 IR excimer laser system (Johnson & Johnson Vision Care, Inc, Santa Ana, California) with either a conventional or a wavefront-guided ablation profile (iDesign or Advanced CustomVue; Johnson & Johnson Vision Care). Corneal flaps were created by using a femtosecond laser (IntraLase iFS or FS-60; Johnson & Johnson Vision Care). All surgeries were performed by 1 of 29 surgeons in 25 surgical centers located in the United Kingdom.

For all patients, the preoperative ophthalmic examination included manifest and cycloplegic refraction, monocular and binocular uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA) using a calibrated projected eye chart, low-light pupil diameter, slit lamp biomicroscopy, dilated fundus examination, noncontact tonometry, corneal topography, ultrasonography pachymetry, and wavefront aberration measurement. All patients were advised to return for 1- and 4-day (PRK patients only), 1-week, and 1-, 3-, and 6-month postoperative examinations, where manifest refraction (except for days 1 and 4), visual acuity, noncontact tonometry and slit-lamp examination were performed. Yearly eye care was also recommended. If patients experienced AEs or side effects that were not resolved by 3 months, they were provided with continuing care until their issues resolved.

All AEs were recorded in the Optical Express electronic medical record (EMR) system. The EMR system is a custom-built system specifically for Optical Express and consists of both clinical and operating room interfaces. It is designed to enable easy capture of pertinent examination data and operating room specifics and has specialized measurements built in to comprehensively capture AEs in order to enable rapid analysis of any potential AE issues. All providers who interface with the EMR, including physicians, optometrists, and operating room nurses and technicians, undergo formal training in its use, which includes instructions for capturing AEs. In order to maximize the reporting of AEs, each electronic visit record (operative and postoperative) has a drop-down list of common LVC AEs. The electronic visit cannot be closed without the user first selecting if an AE had occurred or not. Furthermore, the user can select more than 1 AE for either eye of a given patient, and there is a field for free text entries if the encountered AE does not exist in the prespecified list. Continuous quality monitoring of the EMR data is also undertaken to ensure data integrity. Postoperative variables are analyzed on a per-examiner basis and compared with expected norms. Any substantial outliers trigger a review process with retraining if necessary. Patients who were treated at an outside clinic for an AE were instructed to submit bills to Optical Express for reimbursement. Any outside AE treatment was incorporated into the EMR.

Specific to the operating room, the clinical personnel are trained to record all intraoperative AEs that were evident during a procedure, such as flap complications, suction loss, equipment failure, and so forth. The operating room nurse or technician was trained to enter any AE encountered, and separately the treating physician also was required to enter a free text explanation of the situation leading to the AE. Postoperatively; Patients were seen by qualified and experienced refractive optometrists. The only exception to this was that patients who experienced an intraoperative AE were generally seen by their treating physicians. Any postoperative AE was recorded in the EMR in the process specified above. The refractive optometrists are provided with and instructed in a protocol regarding the engagement of the treating ophthalmic surgeon for management of AEs. Depending on the nature and severity of the AE, the patient was either managed by the optometrist in close communication with the treating surgeon or the patient was immediately referred to the surgeon. All severe AEs were managed by the treating surgeon. Every refractive optometrist undergoes a program of annual education and training to identify and manage AEs.

Statistical Analysis

The AEs were summarized, and the incidence rate was calculated based on the total number of eyes treated in the time period between July 1, 2014, and June 30, 2016. All percentages were calculated on a “per-eye” basis. Postoperative visual acuity outcomes and refractive outcomes for the last available appointment were separately presented for AEs marked as “serious” in Table 1 . Loss of 2 or more lines of best-corrected spectacle acuity was calculated for patients who attended the 3-month or later follow-up visit. This time point was chosen because most of the patients had achieved stabile acuity and refraction at 3 months after LVC. All visual acuity and refractive outcomes calculations were done based on the last available follow-up. Data tabulation was performed using Office Excel software (Microsoft, Redmond, Washington) and STATA software (Stata Corp, College Station, Texas).


The total number of patients treated between July 1, 2014, and June 30, 2016, was 31,921 (61,833 eyes) for LASIK and 5,016 (9,467 eyes) for PRK. Combining LASIK and PRK, the total numbers of patients who attended a minimum of 1-, 3-, 6-, and 12-month follow-up exams were: 89.4%, 60.3%, 40.9%, and 20.0%, respectively. The mean follow-up of the whole study group was 4.4 ± 4.9 months. Table 2 and 3 summarize the incidence of all postoperative AEs.

Table 2


Total Consecutive Treatments 61,833 Eyes of 31,921 Patients
Total Adverse Events 850 (783 Eyes Of 657 Patients): 1.3% Or 1:79 Eyes
Total Serious Adverse Events 287 (271 Eyes of 226 Patients): 0.4% or 1:228 Eyes
AE SAE No of Eyes Incidence 1:__ Eyes Last CDVA ≥20/20 a Last CDVA ≥20/40 b Lost ≥ 2 lines CDVA c
Epithelial ingrowth (stable) 120 0.194% 1:515 94.8% 100.0% 1.0%
Flap striae e Yes 107 0.173% 1:578 89.2% 99.1% 6.1%
Abrasion 100 0.162% 1:618 88.2% 100.0% 2.8%
Recurrent erosions 76 0.123% 1:814 93.0% 98.7% 4.5%
Sterile infiltrates 76 0.123% 1:814 98.6% 100.0% 0.0%
Haze or scar Yes 74 0.120% 1:836 86.6% 100.0% 7.0%
Transient light sensitivity syndrome 70 0.113% 1:883 95.7% 100.0% 1.6%
DLK grade 3 69 0.112% 1:896 94.1% 100.0% 4.3%
Suction loss 31 0.050% 1:1,995 100.0% 100.0% 0.0%
Epithelial ingrowth (required intervention) Yes 18 0.029% 1:3,435 77.8% 100.0% 7.1%
Flap lift (debris/fiber) 14 0.023% 1:4,417 100.0% 100.0% 0.0%
Crystalline lens changes within 12 months of LVC Yes 10 0.016% 1:6,183 60.0% 90.0% 40.0%
Central toxic keratopathy Yes 9 0.015% 1:6,870 75.0% 100.0% 14.3%
Corneal edema Yes 8 0.013% 1:7,729 75.0% 100.0% 0.0%
Ectasia d Yes 8 0.013% 1:7,729 42.9% 87.5% 50.0%
Flap traumatic displacement Yes 7 0.011% 1:8,833 85.7% 100.0% 20.0%
Flap incomplete Yes 6 0.010% 1:10,306 100.0% 100.0% 0.0%
Flap melt Yes 5 0.008% 1:12,367 100.0% 100.0% 0.0%
Flap torn Yes 5 0.008% 1:12,367 100.0% 100.0% 0.0%
Other posterior segment events Yes 5 0.008% 1:12,367 0.0% 100.0% 100.0%
Delayed healing 4 0.006% 1:15,458 100.0% 100.0% 0.0%
Flap buttonhole Yes 3 0.005% 1:20,611 100.0% 100.0% 0.0%
Flap free 3 0.005% 1:20,611 100.0% 100.0% 0.0%
Herpes simplex keratitis Yes 3 0.005% 1:20,611 100.0% 100.0% 0.0%
Incorrect treatment Yes 3 0.005% 1:20,611 100.0% 100.0% 0.0%
Decentred ablation Yes 2 0.003% 1:30,917 0.0% 100.0% 50.0%
DLK grade 4 Yes 2 0.003% 1:30,917 50.0% 100.0%
Equipment failure during surgery Yes 2 0.003% 1:30,917 100.0% 100.0% 0.0%
Gas break through during flap creation Yes 2 0.003% 1:30,917 100.0% 100.0% 0.0%
IOP elevated Yes 2 0.003% 1:30,917 100.0% 100.0% 0.0%
Microbial keratitis Yes 2 0.003% 1:30,917 50.0% 100.0% 50.0%
Retinal detachment Yes 2 0.003% 1:30,917 0.0% 0.0% 100.0%
Irregular flap Yes 1 0.002% 1:61,833 100.0% 100.0% 0.0%
Retinal fear Yes 1 0.002% 1:61,833 100.0% 100.0% 0.0%

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Mar 14, 2020 | Posted by in OPHTHALMOLOGY | Comments Off on Incidence of Intraoperative and Early Postoperative Adverse Events in a Large Cohort of Consecutive Laser Vision Correction Treatments
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