Eyes in the Sky: Laser Eye Surgery to Address the Demands of Presbyopic Commercial Pilots

By Dan Z. Reinstein, MD, MA(Cantab), FRCSC, FRCOphth, DABO, FEBO

Whether they are pinpointing one of hundreds of dials and buttons in the cockpit, viewing radio and autopilot systems at multiple intermediate distances, or reading material in dim lighting conditions, pilots’ vision is crucial not just to their safety but also their passengers’. As pilots age and presbyopia sets in, their near vision deteriorates.

Cockpits are multidimensional environments. Their visual distance requirements imply they were designed by nonpresbyopic engineers who failed to consult experts on vision correction (see A Cockpit’s Visual Requirements for the Flight Instrument Panel). When emergencies occur in the air, pilots must react quickly, but their ability to do so can be hampered by the need to change glasses for different tasks. How can presbyopic pilots safely keep their wings?

Most people who present with presbyopia are prescribed progressive, bifocal, or trifocal glasses. These can offer visual clarity at two or three distances, but they can restrict a pilot’s peripheral vision and require stiff, unnatural head movements.¹ Multifocal contact lenses and IOLs also have drawbacks, including a reduction of contrast sensitivity, halos, and glare.^2,3 For this reason, Class 1 certification does not permit pilots to wear multifocal contact lenses. It tolerates multifocal IOLs only if pilots can pass specific tests of visual function. If they fail, they must undergo an IOL exchange or lose their certification and thus their job.

The need to provide commercial and military pilots with an alternative solution to their presbyopia was the motivation for a recent study of Presbyond Laser Blended Vision LASIK, a procedure that I developed in the mid-2000s and that was commercialized by Carl Zeiss Meditec in 2009.^4-12

RESULTS OF SURGERY

Visual outcomes. The aforementioned study found that 100% and 52% of pilots achieved a binocular uncorrected distance visual acuity of 20/20 or better and 20/16 or better, respectively.⁴ Binocular uncorrected intermediate visual acuity of J3 or better and J5 or better was achieved in 73% and 95% of pilots, respectively. Binocular uncorrected near visual acuity of J1 or better and J2 or better was achieved in 78% and 100% of pilots, respectively. No eye lost 2 lines or more of corrected distance visual acuity—a decrease that might have prevented the pilot from being recertified.⁴

Postoperatively, patients’ contrast sensitivity improved at 3, 6, 12, and 18 cycles per degree.⁴ No statistically significant change was detected in the HD Analyzer (Keeler) objective scatter index or the C-Quant straylight log value (Oculus), indicating that patients maintained an excellent quality of vision after surgery.¹³

All published studies of Presbyond outcomes to date have found the procedure’s safety to be equivalent to that of standard LASIK.^4-12

Functional assessment changes. My colleagues and I developed a 16-point questionnaire to assess the functional performance of pilots and the impact of visual aids before and after surgery. The survey incorporated input from commercial airline pilots and the results of a thorough review of their presenting complaints and motivation to undergo surgery.

We found that pilots’ functional activities improved significantly after surgery; 83.3% of Class 1 pilots reported they no longer required any form of vision correction while flying.¹⁴ Their ocular comfort also improved significantly compared with preoperative levels, with 88% and 12% of pilots reporting greater comfort and no change, respectively. No pilot reported increased discomfort, decreased visual quality, or decreased visual performance (Figure).

MEETING THE VISUAL DEMANDS OF PRESBYOPIC PILOTS

Benefits. Pilots had a higher degree of functionality after Presbyond than with glasses or contact lenses because surgery minimized restrictions in the cockpit environment.¹⁵ They also maintained binocular summation, reported greater eye comfort in their working conditions after surgery, and had better uncorrected distance visual acuity in their near eye than we expected given the myopic refraction of the near-preferred nondominant eye. This is why neural binocular summation was maintained after microanisometropia was achieved.

The findings are particularly important for commercial pilots, who rely on their depth perception to land aircraft safely.^16,17 We also observed a blend zone for clear vision across all distances between both eyes. In contrast, standard monovision correction can compromise intermediate distance acuity. Additionally, patients experienced a statistically significant improvement in contrast sensitivity—a unique advantage over multifocal corneal ablation options and IOLs.^3,18,19

Limitations. Our study found that, although the procedure significantly improved patients’ visual function, some pilots used glasses to see at near or intermediate distance in some circumstances. Given that the cockpit is a visually demanding presbyopic environment, however, we considered reducing the need for glasses to one pair only for certain tasks in 17% of pilots to be an excellent outcome.²⁰ All the pilots in our study had achieved the visual requirements for revalidation of their Class 1 medical certificate, as defined by the United Kingdom Civil Aviation Authority, by 1 month and were able to resume flying shortly thereafter.

A BROAD PERSPECTIVE

In refractive surgery, the keys to patient satisfaction are education and setting realistic expectations, candidate selection, and tailoring the procedure to patient characteristics, needs, and goals.

Qualification for the Presbyond procedure entails a 5-minute, in-office, +1.50 acceptance test. Because the refractive targets are similar for most patients who are at least 40 years old, it is not necessary to take their preferences and required working distances into account like it is for multifocal IOL selection. A truck driver, baker, lawyer, ophthalmologist, and airline pilot, for example, would generally have the same refractive targets with Presbyond.

Pilots have exceptional visual requirements and are not representative of standard patients. The success of Presbyond for pilots should therefore translate positively to the general presbyopic population.

1. Nakagawara VB, Wood KJ, Montgomery RW. Vision impairment and corrective considerations of civil airmen. J Am Optom Assoc. 1995;66(8):489-494.

2. de Silva SR, Evans JR, Kirthi V, Ziaei M, Leyland M. Multifocal versus monofocal intraocular lenses after cataract extraction. Cochrane Database Syst Rev. 2016;12(12):CD003169.

3. Nti AN, Gregory HR, Ritchey ER, Wolffsohn JS, Berntsen DA. Contrast sensitivity with center-distance multifocal soft contact lenses. Optom Vis Sci. 2022;99(4):342-349.

4. Reinstein DZ, Ivory E, Chorley A, et al. PRESBYOND laser blended vision LASIK in commercial and military pilots requiring Class 1 medical certification. J Refract Surg. 2023;39(1):6-14.

5. Reinstein DZ, Archer TJ, Gobbe M. LASIK for myopic astigmatism and presbyopia using non-linear aspheric micro-monovision with the Carl Zeiss Meditec MEL 80 platform. J Refract Surg. 2011;27(1):23-37.

6. Reinstein DZ, Carp GI, Archer TJ, Gobbe M. LASIK for presbyopia correction in emmetropic patients using aspheric ablation profiles and a micro-monovision protocol with the Carl Zeiss Meditec MEL 80 and VisuMax. J Refract Surg. 2012;28(8):531-541.

7. Reinstein DZ, Couch DG, Archer TJ. LASIK for hyperopic astigmatism and presbyopia using micro-monovision with the Carl Zeiss Meditec MEL80 platform. J Refract Surg. 2009;25(1):37-58.

8. Falcon C, Norero Martínez M, Sancho Miralles Y. Laser blended vision (vision combinée) pour la correction de la presbytie : résultats à 3ans. J Fr Ophtalmol. 2015;38(5):431-439.

9. Ganesh S, Brar S, Gautam M, Sriprakash K. Visual and refractive outcomes following laser blended vision using non-linear aspheric micro-monovision. J Refract Surg. 2020;36(5):300-307.

10. Prasad K, Smitha T, Shetty SS, Poojary P. Laser blended vision-LASIK for presbyopia and initial clinical experience in 100 Indian patients. Semantic Scholar. 2015. Accessed October 13, 2023. https://www.semanticscholar.org/paper/Laser-Blended-Vision-LASIK-for-Presbyopia-and-in-Prasad-Smitha/fba59a80feba6fc6da51bb44299686c1aa1d750e

11. Zhang T, Sun Y, Weng S, et al. Aspheric micro-monovision LASIK in correction of presbyopia and myopic astigmatism: early clinical outcomes in a Chinese population. J Refract Surg. 2016;32(10):680-685.

12. Lim DH, Chung ES, Kim MJ, Chung TY. Visual quality assessment after presbyopic laser in-situ keratomileusis. Int J Ophthalmol. 2018;11(3):462-469.

13. Reinstein DZ, Archer TJ, Couch D, Schroeder E, Wottke M. A new night vision disturbances parameter and contrast sensitivity as indicators of success in wavefront-guided enhancement. J Refract Surg. 2005;21(5):S535-540.14.

14. Brar S, Sute SS, Bagare SN, Ganesh S. Functional outcomes and reading speeds following PRESBYOND LBV using nonlinear aspheric ablation profiles combined with micro-monovision. J Ophthalmol. 2021;2021:2957443.

15. Russo A, Reinstein DZ, Filini O, et al. Visual and refractive outcomes following laser blended vision with non-linear aspheric micro-anisometropia (PRESBYOND) in myopic and hyperopic patients. J Refract Surg. 2022;38(5):288-297.

16. Baudu P, Penin F, Arba Mosquera S. Uncorrected binocular performance after biaspheric ablation profile for presbyopic corneal treatment using AMARIS with the PresbyMAX module. Am J Ophthalmol. 2013;155(4):636-647.

17. Nakagawara VB, Veronneau SJH. A unique contact lens–related airline aircraft accident: final report. United States Department of Transportation. May 2000. Accessed October 13, 2023. https://rosap.ntl.bts.gov/view/dot/21488

18. Vargas-Fragoso V, Alió JL. Corneal compensation of presbyopia: PresbyLASIK: an updated review. Eye Vis (Lond). 2017;4:11.

19. Alió JL, Chaubard JJ, Caliz A, Sala E, Patel S. Correction of presbyopia by technovision central multifocal LASIK (PresbyLASIK). J Refract Surg. 2006;22(5):453-460.

20. Ang RE, Cruz EM, Pisig AU, Solis ML, Reyes RM, Youssefi G. Safety and effectiveness of the SUPRACOR presbyopic LASIK algorithm on hyperopic patients. Eye Vis (Lond). 2016;3:33.

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SMILE Has Advantages for Individuals With High-Precision Jobs

By Bruce A. Rivers, MD

To gain recognition and widespread acceptance, technological advances in refractive surgery must offer additional benefits to prospective patients. SMILE meets these requirements for individuals who qualify for the procedure, and it has distinct benefits for individuals with high-precision jobs.

SMILE EXPERIENCE

Adoption. My experience with SMILE began shortly after its FDA approval. I was the director of the Warfighter Refractive Eye Surgery Program and Research Center (WRESP-RC) at Fort Belvoir in Virginia at the time. The US military investigates clinical outcomes as part of the WRESP.

Studies have described the learning curve for SMILE.^1-3 In my experience, the critical step was creating the 50 LASIK flaps to learn the nuances of gentle suction with a femtosecond laser before beginning to perform SMILE.

Patient selection. Offering an array of options allows the choice of surgery to be tailored to the patient (ie, candidacy) and their preferences. I have found that patients sometimes base their decisions on factors such as their friends’ surgical experiences, their jobs, and their hobbies.

Comparisons to LASIK and PRK. Part of integrating SMILE into the WRESP’s offerings was the initiation of a few studies to assess outcomes. A retrospective report on our first year of experience, for instance, compared the visual outcomes of SMILE, PRK, and LASIK.⁴ SMILE was found to be a promising option for myopic patients. Their postoperative visual recovery was similar to that seen after LASIK, and refractive stability was similar to that observed with PRK. These nuances are particularly important to military operations.

The disadvantages of PRK (eg, delayed visual recovery, the possibility of haze formation, and a prolonged steroid taper) may deter patients from undergoing surgery. LASIK flaps created with a femtosecond laser typically are stable even after a supersonic aircraft ejection.⁵ In my experience, however, the flap dislocations service members experienced were not due to military operations but rather off-duty activities, including basketball injuries and mishaps involving toddlers and pets.

Equivalency is often overlooked in discussions of SMILE. A prospective study assessing patients’ functional performance by evaluating their rifle marksmanship¹ showed no significant difference in median scores of their firing range performance with habitual correction preoperatively compared to without correction 6 to 8 weeks postoperatively. Previous firing studies of participants undergoing PRK and LASIK reported similar results.⁶ The marksmanship of more than half of the SMILE patients improved, but various factors can affect performance (Figure). Patient-reported outcomes showed no negative impact on work productivity. Most patients were satisfied with their postoperative vision compared to their preoperative vision.¹

Personal experience. Zachary Skurski, DO, the current director of the WRESP-RC, underwent SMILE just before his cornea fellowship at the Wilmer Eye Institute at Johns Hopkins (read about his experience in the sidebar).

CONCLUSION

I underwent PRK. My wife underwent LASIK in 2010. Last month, my son, Rohan, underwent SMILE. He participates in mixed martial arts and resumed practice 5 days after surgery.

For patients who qualify, SMILE offers the best of two alternative procedures: the rapid visual recovery of LASIK and the refractive stability of PRK. SMILE represents the next step in the evolution of laser refractive technology.

Disclaimer: The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of A.T. Augusta Military Medical Center, the Defense Health Agency, Department of Defense, or US Government. Discussion of any commercial products in this article does not create or imply any federal/Department of Defense endorsement.

1. Sia RK, Ryan DS, Beydoun H, et al. Small-incision lenticule extraction in the U.S. military: prospective study of visual and military task performance. J Cataract Refract Surg. 2021;47(12):1503-1510.

2. Ivarsen A, Asp S, Hjortdal J. Safety and complications of more than 1500 small-incision lenticule extraction procedures. Ophthalmology. 2014;121(4):822-828.

3. Titiyal JS, Kaur M, Rathi A, Falera R, Chaniyara M, Sharma N. Learning curve of small incision lenticule extraction: challenges and complications. Cornea. 2017;36(11):1377-1382.

4. Sia RK, Ryan DS, Beydoun H, et al. Visual outcomes after SMILE from first-year experience at a U.S. military refractive surgery center and comparison with PRK and LASIK outcomes. J Cataract Refract Surg. 2020;46(7):995-1002.

5. Richmond CJ, Barker PD, Levine EM, Hofmeister EM. Laser in situ keratomileusis flap stability in an aviator following aircraft ejection. J Cataract Refract Surg. 2016;42(11):1681-1683.

6. Bower KS, Burka JM, Subramanian PS, Stutzman RD, Mines MJ, Rabin JC. Night firing range performance following photorefractive keratectomy and laser in situ keratomileusis. Mil Med. 2006;171(6):468-471.