Cataract surgery and intraocular lens implantation in aviation pilots

No consensus exists on full-RoF IOLs or postcataract surgery unfit periods. 3 of 5 agencies permit them for pilots, with recovery periods of 6 to 12 weeks.

Abstract

The rising age of pilots and the extension of retirement age underscore the importance of investigating presbyopia correction intraocular lenses (IOLs) during cataract surgery for aviation pilots. This study aims to assess recommendations from aviation regulatory agencies, providing guidance on the use of full-range of field (full-RoF) IOLs full-RoF IOLs in both commercial and military pilots. A review analyzed the perspectives of aviation regulatory agencies regarding the implantation of full-RoF IOLs in pilots. Findings reveal a lack of consensus among agencies regarding the use of full-RoF IOLs. Some adopt a permissive stance, permitting their use, while others maintain restrictive approaches. Variations in the postcataract surgery unfit assessment period were observed, ranging from 6 to 12 weeks. The implantation of full-RoF IOLs in aviation pilots remains contentious. Further research is crucial to address unresolved aspects associated with using full-RoF IOLs in this context.

Pilots during the flight need to constantly use various reading distances in different positions and under various lighting conditions.

Far vision is essential for monitoring what is happening outside the cockpit, but intermediate and near vision are crucial for reading multiple displays and instruments at different distances on the front, lower, and upper panels, as well as printed and written materials that can be necessary to consult during the flight.

In the aviation environment, there are several factors that can significantly compromise visual performance. Pilots are exposed to low levels of luminosity but also to high light intensities that can cause glare and reduce visual acuity (VA). The altitude also affects the quantity and quality of light. When flying above the clouds, sunlight is reflected upward, resulting in a reversed distribution of light where the instrument panel is shaded, while the exterior is highly illuminated, contrary to what normally happens at the ground level. In addition, even in a pressurized cabin, there is a slight degree of hypoxia that can affect dark adaptation, reduce visual fields and VA, and cause a slight increase in intraocular pressure. Furthermore, the low humidity in the cabin air can lead to ocular surface dryness, which is associated with poor visual quality.

Vision is a pilot's most important sense to obtain reference information during flight.¹

The compromise of a pilot's visual performance can be problematic for both pilots and ophthalmologists.

Meeting a pilot's vision requirements to enable optimal task performance can be demanding. To achieve the desired visual outcomes, ophthalmologists must carefully select the appropriate type of intraocular lens (IOL) and accurately determine the refractive power during the preoperative phase of cataract surgery. In addition to this, they must consider that each country is subject to certification by a specific regulatory agency, which may have varying positions regarding the type of IOL.

These professionals also need to consider the visual criteria required for approval in aeromedical certification.

VISUAL SYSTEM EXAMINATION

The following are the steps of an eye examination that need to be assessed.

Initial Eye Examination (According to the EASA)

A comprehensive eye examination by an eye specialist is required at the initial examination.² All abnormal and doubtful cases should be referred to an ophthalmologist. The examination should include (1) history; (2) visual acuities near, intermediate, and distant vision (uncorrected and with best optical correction if needed); (3) examination of the external eye, anatomy, media (slitlamp), and fundoscopy; (4) ocular motility; (5) binocular vision; (6) visual fields; (7) tonometry on clinical indication; (8) objective refraction: hyperopic initial applicants with a hyperopia of more than +2 diopters and the age younger than 25 should undergo objective refraction in cycloplegia; (9) assessment of mesopic contrast sensitivity; and (10) color vision.

Routine Eye Examination (According to the EASA)

A routine eye examination may be performed by an aviation medical examiner and should include (1) history; (2) visual acuities—near, intermediate, and distant vision (uncorrected and with best optical correction if needed); (3) examination of the external eye, anatomy, media, and fundoscopy; and (4) further examination on clinical indication.²

According to the European Union Aviation Safety Agency (EASA), for a class 1 medical certificate, distant VA, with or without correction, shall be 6/9 (0.7) or better in each eye separately and VA with both eyes shall be 6/6 (1.0) or better.²

According to the Federal Aviation Administration (FAA), for a class 1 medical certificate, distant vision shall be 20/20 or better in each eye separately, with or without correction. Near vision shall be 20/40 or better in each eye separately (Snellen equivalent), with or without correction, as measured at 16 inches. Intermediate vision shall be 20/40 or better in each eye separately (Snellen equivalent), with or without correction at age 50 and older, as measured at 32 inches.³

CATARACT

Cataracts have important aeromedical significance. In the past, the development of cataract has ended a pilot's flying career.^4,5

Owing to the increased exposure to ultraviolet radiation, pilots may be at increased risk of developing cataracts.⁶

Cataract is an opacity of the lens of the eye that may cause blurred or distorted vision, or glare. Decreased VA, contrast sensitivity, symptoms of glare, acquired color vision deficiencies, and visual field defects associated with cataracts have the potential to adversely affect flight safety. Untreated cataracts were a factor in a fatal accident in 2013.⁷

In a study conducted at the Japan Aeromedical Research Center, involving a sample of 3780 commercial airline pilots aged between 20 and 65, it was found that 2.8% of the participants exhibited cataracts.⁸

In a study using the electronic Medical Records System of the Australian Civil Aviation Safety Authority, of the 14 163 Australian male commercial pilots licensed in 2011, 1286 aged 60 or older had biennial eye examinations showing a cataract prevalence of 11.6%.⁹

The percentage of pilots aged older than 60 is increasing. According to the Government Accountability Office's analysis of data from the FAA, 13% of active airline pilots fall within the age range of 60 to 64.¹⁰

CATARACT SURGERY AND AVIATION PILOTS

At first glance, it might seem that there is no relationship between cataract surgery and aviation pilots, but this could not be more wrong.

Military pilots were the first to receive intraocular polymethyl methacrylate (PMMA).¹¹

IOLs were invented during the Second World War after Dr. Harold Ridley made a significant observation. The canopy of the British Spitfire fighter plane was composed of PMMA. Dr. Ridley noticed that when acrylic plastic splinters from the canopy of the British Spitfire fighter plane became lodged in the eyes of pilots, contrary to his expectations, the material was not rejected. No significant intraocular inflammation was noted around the splinters of PMMA, and this established the fact that PMMA could remain inside the human eye without obvious unfavorable effects.

This unexpected discovery paved the way for the development of IOLs.¹² The first IOL was implanted by Dr. Ridley in 1949.

Are IOL Implants Safe in Aviation Pilots?

An aspect of consideration regarding IOLs is the theoretical risk of dislocation under the extreme G-forces in the aviation environment.¹³ According to the United States Air Force records, there has been no known dislocation of an IOL during flight duties. Furthermore, study animals with implanted IOLs were subjected to G-forces up to +12 Gz without any signs of dislocation.¹⁴

A case report demonstrated that IOLs may be stable under high G-forces when a pilot with an IOL ejected from a T-6A Texan and the IOL remained stable.¹⁵

In a study by Loewenstein A. et al., a pseudophakic pilot of the Israeli Air Force flying an F-15 aircraft was followed up for 3 years. The IOL did not dislocate, and no complications were observed.¹⁶

IOLs are even stable, effective, and well tolerated during long duration spaceflight.¹⁷

Cataract Surgery

Cataract surgery is the most frequent surgical procedure in developed countries.

The success rate for cataract surgery with IOL implantation is excellent, and the newer techniques using foldable lenses allow use of small incisions and no sutures so that surgically induced astigmatism is reduced, and visual recovery is rapid.¹⁸

The earliest IOLs were used in 1949. Since then, there have been numerous modifications in lens design and manufacture and in the surgical techniques for inserting these lenses. Several types of IOLs are available. According to the International Organization for Standardization (ISO 11979-7, 2024), there are 4 main categories of IOLs that are determined by optical design and/or clinical characteristics or performance: monofocal, toric, simultaneous vision range lenses (SVLs), which include partial-range of field (partial-RoF) and full-range of field (full-RoF) and accommodating IOLs.¹⁹

The corrective capacity of the IOL implant must be taken into consideration to attain aeromedical certification. Another important aspect to consider is the pilot's visual needs to perform their task, which require various working distances, and often occur under adverse conditions, as opposed to many other professions.

Full-RoF IOLs vs Monofocal IOLs

A Cochrane systematic review with meta-analysis including 20 studies concluded that full-RoF IOLs may result in better near vision. Spectacle dependence is less likely with use of these IOLs when compared with the standard practice of monofocal IOL implantation.²⁰

Full-RoF IOLs provide more convenience and spectacle independence. However, side effects such as decreased contrast sensitivity and glare disability and halos have been reported that might affect the pilot performance under low light conditions.^21–23

Using full-RoF IOLs is a balance between more convenience and spectacle independence on one hand and decreased contrast sensitivity and glare disability and halos on the other hand.

Current developments in optical designs for IOLs, such as partial-RoF lenses, can be considered. They have less corrective capacity for near focus but fewer changes in visual quality and dysphotopsia phenomena. However, there are no reports on the implantation of these lenses in pilots.

COMMERCIAL AIRLINE PILOTS AND MILITARY PILOTS

This section is divided in 2 parts: one focusing on commercial airline pilots and the other focusing on military pilots.

Commercial Airline Pilots

Are full-RoF IOLs Approved in Commercial Airline Pilots?

Thanks to advancements in cataract surgery techniques and technologies, pilots who undergo cataract surgery can continue their professional careers, provided they meet the requirements established by the aviation regulatory authority.

Each country is subject to certification by a specific regulatory agency, which presents varying positions regarding the type of IOL that can be implanted in the pilot population group.

Full-RoF IOLs provide more convenience and spectacle independence. However, side effects such as decreased contrast sensitivity and glare disability and halos have been reported that might affect the pilot performance under low light conditions.

There is no consensus among the different regulatory agencies, some of which are very permissive, leaving the decision to the patient and the surgeon, and others being very restrictive, allowing only monofocal IOLs. The use of full-RoF IOLs is allowed by some of the aviation regulatory agencies.²⁴

In accordance with the June 2020 Easy Access Rules for Medical Requirements published by the EASA, after IOL surgery, including cataract surgery, a fit assessment may be considered once recovery is complete and the visual requirements are met with or without correction. IOLs should be monofocal and should not impair color vision and night vision.²

The United Kingdom Civil Aviation Authority (UK-CAA) does not recommend or approve a particular IOL for certification.

The decision to proceed with a full-RoF implant should be made by the applicant and their surgeon, considering the potential impact on the applicant's occupation. Applicants should be aware of the possible adverse effects from any type of lens because aeromedical certification may not be possible if they occur. Scientific data indicate that monofocal IOLs are likely to be less problematic than full-RoF IOLs for the issue of an aeromedical certificate because adverse subjective visual phenomena, particularly halos, are more common and troublesome in people receiving full-RoF IOLs.²⁵

The Civil Aviation Safety Authority (CASA) recommends that the choice of IOL, full-RoF or monofocal, is to be made between the aviation medical certificate holder and their ophthalmic surgeon, based on the likely adverse effects of the type of the lens and its potential impact on their occupation. Full-RoF or partial-RoF IOLs, instead of monofocal IOL, may be acceptable on a case-by-case basis.²⁶

Regarding the regulation of IOL implantation, the regulations set forth by the FAA of the United States are particularly noteworthy. Although monofocal IOLs are permitted, there exists a specific regulation for full-RoF and accommodating lenses, requiring their approval by the FDA. The FAA approves IOLs (full-RoF or accommodating IOL implants) that must be FDA approved.³

According to the International Civil Aviation Organization's Manual of Civil Aviation Medicine from 2012, full-RoF IOLs are available but visual results with these lenses are less satisfactory than with single-vision IOLs. Only single-focus IOLs are considered suitable for use in the aviation environment.²⁷

Table 1 summarizes the legislation of several countries regarding IOL implantation in commercial airline pilots. The use of full-RoF IOLs is allowed by some aviation regulatory agencies. Among the 5 regulatory agencies included in the review, 3 permit the use of full-RoF IOLs in commercial aviation pilots. The summary table illustrates that the current European regulation seems to be one of the most stringent.

Table 1.

Summary of the legislation of several countries regarding IOL implantation in commercial airline pilots

Country	Regulatory agency	IOL recommendations	Are full-RoF IOLs approved?
European Union	EASA2	IOLs should be monofocal and should not impair color vision and night vision	No
The United Kingdom	UK-CAA25	Does not recommend or approve a particular IOL for certification. Applicants should be aware of the possible adverse effects from any type of lens because aeromedical certification may not be possible if they occur	Yes
Australia	CASA26	Full-RoF or partial-RoF IOLs, instead of monofocal IOL, may be acceptable on a case-by-case basis. The choice of IOL—full-RoF or monofocal—is to be made between the aviation medical certificate holder and their ophthalmic surgeon	Yes
The United States	FAA3	IOLs (full-RoF or accommodating IOL implants) that must be FDA approved	Yes
International	ICAO27	Only single-vision IOLs are considered suitable for use in the aviation environment	No

CASA = Civil Aviation Safety Authority; EASA = European Union Aviation Safety Agency; FAA = Federal Aviation Administration; ICAO = International Civil Aviation Organization; UK-CAA = United Kingdom Civil Aviation Authority

When to Return to Aviation Activities After Cataract Surgery?

There are no unanimous recommendations regarding the period of unfit assessment after cataract surgery. In addition, this is also an important issue because it is considered that for full-RoF lenses, there is a process of neuroadaptation in the first 6 months postoperatively.²⁸

The EASA recommends that after IOL surgery, including cataract surgery, a fit assessment may be considered once recovery is complete and the visual requirements are met with or without correction.²

The UK-CAA states that cataract surgery will result in an unfit assessment for at least 6 weeks. Fitness can be reassessed after complete recovery from surgery. Assessment should include a comprehensive eye examination to include assessment of contrast and glare sensitivities and mesopic contrast sensitivity. A report from this assessment should be provided to the applicant's aeromedical examiner along with a detailed report from the specialist who performed the procedure. This report should include the date of surgery, the type of implant used, and confirmation that the pilot has fully recovered from surgery and that there are no postoperative complications.²⁵

The CASA recommends a review for return to aviation activities after surgery at least 2 weeks after monofocal IOL and 12 weeks after full-RoF or partial-RoF IOL in case of recovery after uneventful surgery. A period of grounding will be required until postsurgical recovery is complete, and a satisfactory review from the operating surgeon has been received, typically 4 to 6 weeks.²⁶

The FAA recommends a minimum 3-month adaptation period after surgical lens implantation before certification. The pilot must present 20/20 distance vision, and 20/40 near and intermediate vision. In addition, a comprehensive report is required, affirming stable VA and refractive error, absence of significant side effects or complications, need of medications, and freedom from any glare, flares or other visual phenomena that could affect visual performance and aviation safety.³

The period of unfit assessment after cataract surgery varies between 6 weeks and 12 weeks.

Table 2 summarizes the recommendations after cataract surgery in commercial airline pilots.

Table 2.

Recommendations after cataract surgery in commercial airline pilots

Country	Regulatory agency	Recommendations after cataract surgery	Unfit assessment period (wk)
European Union	EASA2	A fit assessment may be considered once recovery is complete, and the visual requirements are met with or without correction	Until recovery is complete
The United Kingdom	UK-CAA25	Unfit assessment for at least 6 wk	6
Australia	CASA26	A period of grounding will be required until postsurgical recovery is complete and a satisfactory review from the operating surgeon has been received, typically 4-6 wk	4-6
The United States	FAA3	3-mo adaptation period after surgical lens implantation before certification	12
International	ICAO27	—	—

CASA = Civil Aviation Safety Authority; EASA = European Union Aviation Safety Agency; FAA = Federal Aviation Administration; ICAO = International Civil Aviation Organization; UK-CAA = United Kingdom Civil Aviation Authority

Are full-RoF IOLs Possibly Safe in Aviation Activities?

The use of full-RoF IOLs allows pilots to achieve spectacle independence.

There is no consensus among the different regulatory agencies, some of which are very permissive, leaving the decision to the patient and the surgeon, and others being very restrictive, allowing only monofocal IOLs.

There are very few studies comparing the use of full-RoF IOLs vs monofocal IOLs in aviation pilots.

In Europe, the EASA allows only the use of monofocal IOLs.

The UK-CAA does not recommend or approve a particular IOL for certification.

In Australia, the decision to implant a full-RoF IOL is to be made between the pilot and their ophthalmic surgeon.

In the United States, the FAA allows full-RoF IOLs in pilots. The IOL model must be approved for use in the United States, and the implantation must be performed at least 3 months before the FAA physical examination.

Lee Lenton concluded that the performance of visually related flight simulator tasks was not significantly impaired in older adults with full-RoF IOLs compared with age-matched adults with monofocal IOLs.

There were no significant differences in the self-reported quality of vision between the full-RoF and monofocal IOL groups, for either distance or reading vision during the day and at night. The full-RoF IOL group had a significantly higher incidence of halos compared with the monofocal IOL group. Although there was a trend toward greater severity of these haloes in the full-RoF IOL group, this did not reach statistical significance. There were no significant differences in photopic or mesopic VA or photopic or mesopic contrast sensitivity between the groups. These findings suggest that full-RoF IOLs do not impair visual performance in a flight simulator.²⁹

Currently, if a commercial airline pilot who has undergone cataract surgery with the implantation of a full-RoF IOL is working in a region where full-RoF IOLs are allowed (such as the United States) but decides to pursue their professional career in another region where such lenses are not permitted (for example, in Europe), the only solution may be to undergo lens explantation, despite having achieved optimal vision results with the full-RoF IOL.

In addition, ophthalmologists should be informed about the specific considerations involved in cataract surgery for this particular population. It is crucial for them to make appropriate choices regarding the IOLs for these patients because the implantation of a full-RoF IOL may not be compatible with the guidelines set by the aviation regulatory agency.

In the future, a potential solution could involve the inclusion of a multicrew pilot license restriction in the aeromedical certificate after cataract surgery with the implantation of a full-RoF IOL.

Military Pilots

Cataract surgery is a rare procedure before the age of 40 to 45, so the possibility of this procedure in candidates for the Air Force is not common. However, the possibility of implanting IOLs is an increasingly frequent scenario among active pilots.^30,31

According to the North Atlantic Treaty Organisation Research and Technology Organisation publication titled “Refractive Surgery: New Techniques and Usability for Military Personnel,” which was published in November 2012, full-RoF IOLs are not permitted for aviators.

Full-RoF IOLs are permitted for General Military Service in Germany, Spain, and the United States. In Denmark, full-RoF IOLs are not permitted for aviators. However, for the General Military Service, each case is evaluated individually to determine the feasibility of using such lenses.³²

CONCLUSIONS

The compromise of a pilot's visual performance can be problematic for both pilots and ophthalmologists. Meeting a pilot's vision requirements to enable optimal task performance can be demanding.

To achieve the desired visual outcomes, ophthalmologists must carefully select the appropriate type of IOL and accurately determine the best solution for correcting functional vision without compromising visual quality when performing their tasks in a specific working environment.

In addition to this, they must consider that each country is subject to certification by a specific regulatory agency, which may have varying positions regarding the type of IOL.

These professionals also need to consider the visual criteria required for approval in aeromedical certification. The use of full-RoF IOLs in aviation pilots remains a topic of discussion. Special attention should be given to the selection of an IOL implant because choosing a full-RoF IOL could potentially lead to failure to meet aeromedical requirements in certain countries.

Therefore, it is essential for ophthalmologists to be aware of the differing positions on the type of IOL implant allowed by various regulatory agencies. There is no consensus among these agencies; some are very permissive, leaving the decision to the patient and the surgeon, while others are very restrictive, allowing only monofocal IOLs. The use of full-RoF IOLs is permitted by some aviation regulatory agencies. Among the 5 agencies included in the review, 3 permit the use of full-RoF IOLs in commercial aviation pilots.

There are no unanimous recommendations regarding the period of unfit assessment after cataract surgery. The period of unfit assessment after cataract surgery varies between 6 weeks and 12 weeks. Spectacle independence is a favorable element for this professional activity. Full-RoF IOLs can be an effective way to overcome the limitations of wearing spectacles for pilots.

This research aimed to elucidate various perspectives on this topic and offer guidance to both pilots and ophthalmologists. Further studies regarding the use of full-RoF IOLs in aviation pilots are needed.