Laser refractive surgery in the United States Navy

[Ophthalmic disqualification from the military services: Multicentric cross-sectional study]

PURPOSE

This article aims to describe the causes of ophthalmological disqualification from the military services detected during specialist consultations conducted at Army Training Hospitals.

METHODS

This observational, cross-sectional, multicenter study retrospectively included individuals deemed as "unfit for military service" due to eye diseases identified during the specialist consultation conducted at 3 ATHs between January 2020 and December 2021. The data collected included age, medical and surgical history, reasons for ophthalmological disqualification, uncorrected distance visual acuity, best corrected distance visual acuity and cycloplegic refraction.

RESULTS

Over this period, 133 subjects (98 men and 35 women) were included. Thirty-eight candidates (28.6%) were declared unfit due to a refractive error beyond the required limits, including 30 myopic subjects in excess of -10 diopters (D) and 8 hypermetropic subjects over +8 D. Twenty-five candidates (18.8%) were unfit under the age of 21 years due to corneal refractive surgery performed before the required age. Four subjects (3.0%) were unfit due to phakic intraocular lenses. Degenerative conditions were observed in 23 subjects (17.3%), including 21 patients with severe keratoconus. Other causes of incapacity were linked to oculo-orbital trauma in 11 subjects (8.3%), moderate or severe amblyopia in 7 patients (5.3%), congenital causes in 7 subjects (5.3%), inflammatory or infectious diseases in 7 candidates (5.3%), hereditary causes in 6 subjects (4.5%) and undetermined visual dysfunctions in 4 subjects (3.0%).

CONCLUSION

The three main causes of ophthalmological disqualification were high ametropia, refractive surgery performed before the required age and keratoconus.

Photorefractive Keratectomy in Student Naval Aviators: Outcomes of the U.S. Navy Accessioning Study

PURPOSE

To present the outcomes of the U.S. Navy photorefractive keratectomy (PRK) accessioning study conducted between 2000 and 2005 that helped lead to the acceptance of laser vision correction within the U.S. aviation industry.

METHODS

In this prospective masked study, a total of 301 students who had PRK and underwent naval flight training were compared to 4,368 untreated peers. Three training pipelines were compared: propeller/jet transport, jet fighters, and helicopters. The evaluated metrics were flight and academic performance (assessed for the primary and advanced stage of the training as normalized Navy Standard Score [NSS]), as well as the student attrition rate from training.

RESULTS

The attrition rate was lower in the PRK group compared to controls (15.9% vs 23.2%; P = .004). In the primary stage of training, students who had PRK outperformed controls in flight training performance in the propeller/jet transport pipeline (average NSS after PRK: 52.4 ± 7.5 vs controls: 50.7 ± 6.4, P = .02), but the flight performance in the jet fighter and helicopter pipelines was comparable between the two groups. Academic performance in the primary stage of training was approximately 7% to 13% higher in students who had PRK for all training pipelines. During the advanced training stage, there was no difference in the flight performance between the groups in any of the presented pipelines. Academic performance was significantly better for students who had PRK in the helicopter pipeline (51.2 ± 11.0 vs 46.7 ± 11.7 P < .001) but comparable between the two groups in the remaining pipelines.

CONCLUSIONS

Refractive surgery did not have adverse effects on flight performance metrics. Pilots who had PRK had comparable or better outcomes than their untreated peers. [J Refract Surg. 2024:40(3):e173-e181.].

Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance

PURPOSE

To assess early visual outcomes and military task performance after small-incision lenticule extraction (SMILE) among U.S. military service members.

SETTING

Warfighter Refractive Eye Surgery Program and Research Center and Night Vision and Electronic Sensors Directorate, Fort Belvoir, Virginia.

DESIGN

Single-center, prospective, observational study.

METHODS

The study was composed of active duty service members (n = 37) electing to undergo SMILE for myopia or myopic astigmatism. Testing performed preoperatively and at 1 month and 3 months postoperatively included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, wavefront aberrometry, low-contrast visual acuity (LCVA), contrast sensitivity, and vision-related questionnaire. 14 participants underwent rifle marksmanship with spectacle correction before and without correction at 6 to 8 weeks postoperatively.

RESULTS

At 3 months postoperatively, the efficacy index was 0.96 and the safety index was 1.03. UDVA was ≥20/20 in 69 (96%) of eyes. LCVA change from baseline was significant under night vision condition. Eye problems contributed to 10% work and 20% activity impairments, both of which decreased to 0% (P = .001). The overall satisfaction rating for SMILE was high at 90.9 (95% CI, 85.3 to 96.5), and 95% of participants would be willing to undergo the procedure again. The median scores between preoperative and 6 to 8 weeks postoperative firing performance were comparable (34 vs 35, with and without correction, respectively; P = .247).

CONCLUSIONS

After the early recovery period, SMILE seems to preserve quality of vision, which appears to facilitate the accomplishment of tasks related to their work as military service members as well as performing activities outside of work.

Intra-Operative Discomfort in Photorefractive Keratectomy

Purpose

Photorefractive keratectomy (PRK) remains a viable, safe, and efficacious option for patients wishing to correct refractive errors. One of its most significant drawbacks is pain. While post-operative pain has been well studied with different management options, intra-operative pain has been less well defined. The purpose of this study was to characterize intra-operative pain during PRK in regard to eye operated on, gender, excimer platform used, surgeon, and age.

Patients and Methods

A total of 134 patients (264 eyes) were prospectively randomized to undergo bilateral PRK of either the right eye first or the left eye first followed immediately by the fellow eye. In the immediate post-operative period they were surveyed using an 11-point Numeric Rating Scale regarding intra-operative pain or discomfort experienced in each eye. Resultant pain scores were then analyzed via two sample z-test and analysis of variance (ANOVA) to characterize pain overall as well as comparing first versus second eye operated on, right versus left eye, male versus female, excimer platform used, inter-surgeon variability, and age.

Results

Of 264 eyes surveyed the mean pain experienced on a 0–10 pain scale was 1.13 (minimal discomfort). There was no statistically significant difference in pain or discomfort when comparing first versus second eye operated on, right versus left eye, male versus female, excimer platform used, operating surgeon, or age.

Conclusion

Intra-operative pain or discomfort experienced by patients is minimal. The absence of statistically significant differences in pain scores studied implies that standard of care procedures achieve adequate analgesia in PRK.

Quality of Vision Following LASIK and PRK-MMC for Treatment of Myopia

INTRODUCTION

Femtosecond-assisted thin flap, laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy with mitomycin-C (PRK-MMC) are the two most common refractive surgical procedures used to enhance visual capability in the U.S military. The purposes of the study were to examine effects on quality of vision following LASIK and PRK-MMC using a novel computer-based quick contrast sensitivity function (qCSF) test.

MATERIALS AND METHODS

This prospective clinical study included 58 active duty U.S. military service members who elected LASIK (n = 29) or PRK-MMC (n = 29) refractive surgery for myopia (nearsightedness) treatment. Monocular photopic and mesopic quality of vision of the right eyes in spectacle correction preoperatively and unaided right eyes at four postoperative follow-up visits (1 week, 2 weeks, 1 month, and 3 months) were examined using the qCSF device. Two qCSF parameters, area under a log CSF (AULCSF) between 1.5 and 18 cycles per degree, and CSF cutoff acuity (CSF Acuity), were collected using a 50-trial setting at a 4-m testing distance. General linear model (GLM) Repeated-measures Analysis of Covariance was used to examine effects on quality of vision following LASIK and PRK-MMC. Post hoc testing with Bonferroni correction was used for pairwise comparisons, and preoperative cylinder refraction was used as a covariate. Two-tailed independent t-test was used to compare preoperative and postoperative parameters between LASIK and PRK-MMC. Pearson's correlation, Bland-Altman plots, and multiple linear regression were used to examine the relationship among the qCSF and other vision tests.

RESULTS

Quality of vision, AULCSF, and CSF Acuity returned to the preoperative baseline at postoperative 2 weeks under mesopic condition and at postoperative 1 month under photopic condition after PRK-MMC. In comparison, photopic and mesopic quality of vision were not significantly different from the baseline at any of the four postoperative visits following LASIK. Changes of CSF Acuity from the baseline after LASIK were significantly better under photopic than mesopic condition by 0.067 ± 0.014 logarithm of the minimum angle of resolution (logMAR); P < .001). Quality of vision was not significantly different between the LASIK and PRK-MMC groups at postoperative 1 and 3 months. When predicting photopic AULCSF (overall model fit R2 = 0.47), 5% contrast acuity (beta = -0.43), visual acuity in 100% contrast (beta = -0.18), and residual refraction in spherical equivalent (beta = 0.20) were significant predictors (P ≤ .001), while high-order aberrations (beta = -0.07, P = .22) were not significant predictors. Visual acuity (beta = -0.12, P = .07) and high-order aberrations (beta = -0.04, P = .58) were not significant predictors of mesopic AULCSF. Bland-Altman plots show that photopic CSF Acuity and visual acuity had a mean difference of 0.19 ± 0.01 logMAR with limits of agreement (LOAs) at -0.01 and 0.39 logMAR. Photopic CSF Acuity and 5% contrast acuity had a mean difference of -0.06 ± 0.01 logMAR with LOAs at -0.33 and 0.21 logMAR.

CONCLUSION

Quality of vision recovers at postoperative 1 week after LASIK and at postoperative 1 month after PRK-MMC. The standard black-on-white high-contrast, chart-based visual acuity test is weak in predicting quality of vision. The qCSF detects mild-to-moderate visual changes and is suitable for quality of vision assessment following refractive eye surgery.

Assessment of Factors Associated With Postoperative Pain After Photorefractive Keratectomy

PURPOSE

To define the factors that affect patient's self-assessed postoperative pain after photorefractive keratectomy (PRK).

METHODS

Patients who underwent PRK in 2016 were evaluated. Anonymized data collected included patient gender, age, and season at the time of surgery, ablation depth, surgeon status (attending vs. resident), topical tetracaine use, and subjective pain scores at postoperative days (PODs) 1 and 7. Average pain scores and amount of pain medication taken were analyzed for each of the previously mentioned variables.

RESULTS

Overall, 231 patients who underwent PRK were analyzed. The mean pain score and SD were 0.78 ± 1.87 on POD 1 and 0.03 ± 0.37 by POD 7. Patients who used topical tetracaine reported significantly higher pain on POD 1 and 7 compared with patients who did not use tetracaine (P < 0.001 and P = 0.038, respectively). No significant differences in pain scores were seen based on surgeon status, ablation depth, gender, and season. Patients who used topical tetracaine took a higher amount of oral pain medication (9.44 ± 6.01) compared with those who did not (7.02 ± 4.71) (P = 0.022).

CONCLUSIONS

Postoperative pain was significantly elevated in patients who used tetracaine on POD 1 and POD 7. These patients were also more likely to take oral pain medication than those who did not use topical tetracaine. Surgeon status, season, gender, and ablation depth showed no significant differences in subjective pain scores. Oral pain medication should be evaluated to assess efficacy and safety in inhibiting ocular pain after PRK.

Excimer Lasers in Refractive Surgery

Introduction

In the field of ophthalmology, laser technology is used in many basic and clinical disciplines and specialities. It has played an important role in promoting the development of ophthalmology.

Aim

This article is designed to review the evolution of laser technology in refractive surgeries in ophthalmology, mainly focusing on the characteristics of the excimer laser applied in corneal refractive surgery.

Methods

This article was performed based on a literature review and Internet search through scientific databases such as PubMed, Scopus, Web of Science and Google Scholar.

Result

The literature on excimer laser technology addresses the technical and physical aspects of excimer lasers including types, characteristics and commercially available lasers on the market.

Conclusion

The conclusion on this forum aims to help understand the benefits of excimer laser use in ophthalmology, with focus on correction of refractive errors.

Corneal re-innervation following refractive surgery treatments

Laser refractive surgery is one of the most performed surgical procedures in the world. Although regarded safe and efficient, it has side effects. All of the laser based refractive surgical procedures invoke corneal nerve injury to some degree. The impact of this denervation can range from mild discomfort to neurotrophic corneas. Currently, three techniques are widely used for laser vision correction: small incision lenticule extraction, laser-assisted keratomileusis in situ and photorefractive keratotomy. Each of these techniques affects corneal innervation differently and has a different pattern of nerve regeneration. The purpose of this review is to summarize the different underlying mechanisms for corneal nerve injury and compare the different patterns of corneal reinnervation.

Excimer laser refractive surgery rate in Iran: 2010-2014

Purpose

To determine the rate of excimer laser refractive surgery in Iran and its trend during 2010–2014, and the number of surgeries per ophthalmologist.

Methods

Twelve provinces were considered for the study; 4 major referral provinces of Tehran, Fars, Isfahan, and Khorasan, and 8 others which were selected randomly. Then a number of excimer laser centers were chosen from each province. In the timeframe between 2010 and 2014, one week per season was randomly selected for each center, and the number of surgeries conducted in these 20 weeks was determined by trained personnel.

Results

In the 12 surveyed provinces, 28 of the 57 active surgical centers were selected. The rate of excimer laser refractive surgery in 2010 in Iran was 2764 per million population which reached 3744 per million by 2012 and took a slightly decreasing trend to 3582 until 2014. Based on the number of ophthalmologists and the number of surgeries in 2014, the average number of surgeries per ophthalmologist was 103 surgeries.

Conclusion

This is the first study to report the rate of excimer laser refractive surgery in Iran.

Three-Year Longitudinal Survey Comparing Visual Satisfaction with LASIK and Contact Lenses

PURPOSE

To assess patient satisfaction and perceived outcomes with different methods of refractive error correction through annual surveys administered over a 3-year period.

DESIGN

Prospective, longitudinal, parallel-group, multicenter survey.

PARTICIPANTS

A total of 1800 subjects, aged 18 to 60 years, who had LASIK or continued using contact lenses.

METHODS

Twenty sites across the United States enrolled subjects who completed a study-specific baseline survey during a contact lens examination or while being evaluated as a candidate for LASIK. Links to follow-up surveys were emailed annually for 3 years. Between-group differences were assessed by analysis of variance, and associations were assessed by logistic multivariate regression.

MAIN OUTCOME MEASURES

Visual satisfaction.

RESULTS

Of 1800 subjects, 694 (39%) comprised the control group who continued contact lens wear, 819 (45%) wore contacts at baseline and had LASIK, and 287 (16%) wore glasses at baseline and had LASIK. Most contact lens users had worn them successfully ≥5 years. The proportion expressing strong satisfaction with their current vision correction method decreased from 63% at baseline to 54% at year 3 in the contact lens control group, whereas 88% of former contact lens wearers and 77% of former glasses wearers were strongly satisfied with LASIK at year 3. Patients 40 years of age or younger when they had LASIK were somewhat more likely to be strongly satisfied than older patients. LASIK significantly reduced difficulties with night driving and nighttime visual disturbances among former contact lens users and former glasses users. The proportion with dry eye symptoms at 1, 2, or 3 years after LASIK was not significantly increased relative to baseline contact lens wear but was significantly increased relative to baseline glasses use, consistent with many glasses users having tried and abandoned contact lenses because of latent dry eye problems. Compared with continued contact lens wear, LASIK significantly reduced the self-reported rates of eye infections, ulcers, and abrasions each year.

CONCLUSIONS

Compared with contact lens wear, current LASIK technology improved ease of night driving, did not significantly increase dry eye symptoms, and resulted in higher levels of satisfaction at 1, 2, and 3 years follow-up.

Application of cold patch in relieving pain after transepithelial photorefractive keratectomy

Although photorefractive keratectomy often results in better corneal stability and fewer corneal flap complications than LASIK, pain remains a major drawback of the procedure. The authors compared the safety and efficacy of a postoperative cold patch versus intraoperative application of a chilled balanced salt solution on transepithelial photorefractive keratectomy-related postoperative pain.

BACKGROUND:

A return toward toward photorefractive keratectomy has occurred due to better corneal stability and fewer corneal flap complications; however, pain remains a major drawback of the procedure. Currently, clinical pain control measures focus on the administration of pain medications, which may delay corneal epithelial healing and has, occasionally, led to serious corneal toxicity.

OBJECTIVES:

To investigate the safety and efficacy of a cold patch on postoperative pain and other relevant consequences of transepithelial photorefractive keratectomy.

METHODS:

A prospective, randomized controlled study was conducted. Forty patients (80 eyes) scheduled to undergo transepithelial photorefractive keratectomy for myopia or myopic astigmatism were randomly and equally assigned to be treated with ice-cold balanced salt solution during surgery (wash group) or to wear a postoperative cold patch on the eye for 24 h. The main outcomes were pain score on a visual analogue scale, postoperative eyelid edema, conjunctival hyperemia, epithelial healing time, haze and postoperative best-corrected visual acuity.

RESULTS:

All patients completed the final tests. Demographic characteristics and pain scores during surgery were similar between the two groups. The mean postoperative pain scores of patients in the cold patch group at 8 h, 16 h and 24 h were significantly lower than those of patients in the wash group. Scores for postoperative eyelid edema and conjunctival hyperemia in the cold patch group were also lower than in the wash group. Patients in the cold patch group used fewer painkillers. Epithelial healing time, haze and early recovery of visual acuity were similar between the two groups. No eyelid frostbite was observed.

CONCLUSION:

Wearing a cold patch on the eye after transepithelial photorefractive keratectomy effectively relieved pain and inflammation, and reduced the use of painkillers without any side effects.

Efficacy and safety of pain relief medications after photorefractive keratectomy: review of prospective randomized trials

The objective of this review was to provide a comprehensive overview and comparison of results from all prospective randomized trials published to date of medications used to treat pain after photorefrative keratectomy (PRK). A PubMed database search revealed 23 prospective and randomized studies. They included the following classes of medications: nonsteroidal antiimflammatory drugs (NSAIDs), anesthetics, opiates, acetaminophen, gabapentin, and pregabalin. The studies found that although the efficacy of drugs tended to be similar, tetracaine 1% and nepafenac 0.1% tended to have the most analgesic effect. Delayed corneal reepithelialization was a common side effect of both topical anesthetics and topical NSAIDs. Tetracaine 1% resulted in the most significant delay in reepithelialization when tested against placebo control compared with other topical medications tested against placebo. Concomitant use of topical NSAIDs and topical anesthetics, especially tetracaine, may have to be avoided to minimize the risk for delayed corneal healing.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

Excimer laser surface ablation: a review of recent literature

The aim was to review the recently published literature on excimer laser surface ablation procedures, including photorefractive keratectomy (PRK), laser sub-epithelial keratomileusis (LASEK), microkeratome-assisted PRK (epi-LASIK) and trans-epithelial (laser-assisted) PRK, to help elucidate where and how surface ablation may best fit into current refractive surgical practice. The emphasis was on publications within the last three years and included systemic reviews, meta-analyses and randomised controlled trials. Where such evidence did not exist, selective large series cohort studies, case-controlled studies and case series with follow-up preferably greater than six months were examined and included. Refractive and visual outcomes are excellent and comparable to those after LASIK even in complex cases after previous corneal surgery. Indeed, surface ablation combined with corneal collagen cross-linking may be used in selected eyes with biomechanical instability, where LASIK is contraindicated. In addition, there is evidence to suggest that there may be less induction of higher order aberrations with surface techniques. Long-term stability and safety appear to be extremely satisfactory. The literature supports the use of modern excimer laser surface treatments, with outcomes comparable to those after LASIK and evidence of less induction of higher-order aberrations. Follow-up studies at 10 to 20 years indicate excellent stability and safety.

Refractive surgery safety at altitude

Over the years, many climbers and other visitors to high altitude have been attracted to refractive surgery in hopes of lessening their dependence on glasses. Although there has been a gradual refinement of these procedures over time, they continue to have the potential for visual changes with altitude exposure. The goal of this review is to provide guidance to clinicians as to how to better advise their patients on the pros and cons of these procedures.

Long-term corneal wavefront aberration variations after photorefractive keratectomy for myopia and myopic astigmatism

PURPOSE

To analyze the higher-order corneal wavefront aberration during an 8-year follow-up after photorefractive keratectomy (PRK).

SETTING

IRCCS Fondazione G.B. Bietti, Rome, Italy.

DESIGN

Case series.

METHODS

Patients having PRK using the Technolas 217C excimer laser platform were divided into 3 groups according to the preoperative refraction as follows: low myopia, high myopia, and astigmatism. The preoperative and 1-, 4-, 6-, and 8-year postoperative root mean square (RMS) values of coma, spherical aberration, and total higher-order aberrations (HOAs) were calculated with 3.5 mm and 6.0 mm simulated pupils. The mean preoperative and postoperative higher-order corneal wavefront aberration maps, point-spread functions, and radial modulation transfer functions (MTFs) were represented to describe the impact of PRK on the optical quality of the anterior cornea.

RESULTS

The study enrolled 33 patients (66 eyes). Corneal spherical aberration was statistically significantly higher after PRK for simple myopia with 3.5 mm and 6.0 mm pupils (P<.05). The postoperative increase in coma was statistically significant in the high-myopia group with both pupil sizes (P<.05). Total RMS HOAs increased postoperatively with a 6.0 mm pupil in all groups (P<.05). The mean radial MTF was almost stable in all groups between preoperatively and postoperatively.

CONCLUSIONS

Higher-order corneal wavefront aberrations stabilized 1 year after PRK to treat myopia or myopic astigmatism. The effect of induced corneal HOAs tended to increase after correction of high myopia with large pupils, although without degrading the image optical quality of the cornea over the long term.

Phakic intraocular lens implantation in United States military warfighters: a retrospective analysis of early clinical outcomes of the Visian ICL

PURPOSE

To assess short-term clinical outcomes after implantation of phakic intraocular lenses (Visian ICL, STAAR Surgical Co) in US military warfighters who are not good candidates for laser vision correction.

METHODS

A retrospective interventional consecutive case series analysis of all eyes that underwent ICL surgery during a 14-month time period was performed. Main outcome measures included indications for surgery, efficacy, predictability, and early adverse events.

RESULTS

Three-month postoperative visual data were available for 135 eyes of 69 patients who underwent ICL implantation during the study period. Indications included abnormal corneal topography (37%), thin predicted residual bed following LASIK (32%), history of dry eye (13%), thin corneal thickness (11%), or other (7%). Mean patient age was 30.9 ± 6.6 years. Mean preoperative spherical equivalent refraction was -6.00 ± 1.92 diopters (D) (range: -2.63 to -11.50 D). Three months postoperative, uncorrected distance visual acuity of 20/20 or better was found in 129/135 (96%) eyes and 91/135 (67%) were 20/15 or better. Manifest refraction and corrected distance visual acuity (CDVA) data were available for 128 eyes. Forty-two (33%) eyes had improvement of one or more lines of CDVA. One hundred fifteen eyes (90%) were within ± 0.50 D of emmetropia, and predictability within ± 0.75 D was found in 127/128 (99%) eyes. No significant intra- or postoperative complications were observed.

CONCLUSIONS

This retrospective analysis of 3-month outcomes suggests that Visian ICL implantation in myopic warfighters provides excellent refractive and visual results. Further study is needed to evaluate long-term results.

Effect of topical 0.5% morphine on postoperative pain after photorefractive keratectomy

PURPOSE

To investigate safety and efficacy of 0.5% morphine drops for pain control after photorefractive keratectomy (PRK).

METHODS

In a double-blind prospective study, 40 patients were randomized to either 0.5% morphine drops (n=20) or vehicle control (n=20). Treatment occurred every 2 hours following PRK on the day of the procedure, then four times daily on postoperative days 1 through 3. Patients completed pain assessment questionnaires (visual descriptor, numerical rating, visual analog scales, and oral analgesic consumption) every 2 hours while awake during the treatment period. Daily average and maximum scores were compared between the two groups. Patients were examined daily for 4 days after PRK, weekly for 4 weeks, then monthly for 3 months. Epithelial healing, corneal haze, and refractive outcomes were compared.

RESULTS

Both average and maximum pain scores were lower in the morphine group than in the vehicle control group on all scales and during all 4 days after PRK. Statistical significance (P<.05) was reached on numeric rating scale on procedure day and on postoperative day 1. The difference between the groups on the visual analog scale was statistically significant on procedure day, and on postoperative days 1 and 2. Oral analgesic consumption was higher in the vehicle control group on postoperative day 2. No difference between groups was noted in epithelial healing or refractive outcomes. Stromal haze scores were lower in the morphine group, but the difference was not statistically significant.

CONCLUSIONS

Topical 0.5% morphine may be an effective and safe method of pain control after PRK.