A pilot’s suitability to fly can often hinge on the assessment of an eyecare professional. While optometrists play a key role in pilot vision assessments today, it hasn’t always been this way. MYLES HUME looks back on optometry’s fight for recognition as aviation eye examiners.
As optometrist Mr Tony Gibson flew over Victoria and Queensland in the early 1970s, leaning out the window of a chartered light aircraft to photograph features on the ground, you’d be forgiven for wondering if he’d lost his bearings.
It sounds far removed from the vocation that’s led him to Eyecare Plus Mitcham, Victoria, where he practises today alongside colleagues and optometrist daughter, Riki.
But back then, Gibson had commenced a Master’s degree at the Optometry Department in Victoria commissioned by the Aviation Medicine section of the Department of Civil Aviation. His expertise was called upon after pilots who failed existing visual acuity standards challenged the outcomes, claiming they had been determined arbitrarily and that reading letter charts with or without correction was unrelated to visually navigating an aircraft.
At the time, the Optometry Department and Victorian College of Optometry – under the late Professor Barry Cole – was involved in visual ergonomic research projects investigating colour signals and target movement detection, so the project was a good fit.
After interviewing pilots of varying experience about which terrain features they used to navigate, Gibson captured the images from above and set up a basic simulation model to test the navigation task and visual acuity on a standard chart with up to 3 dioptres of blur, simulating uncorrected myopia.
In the end, he showed the pilots’ performance worsened around 6/9 and 6/12, but after that it plateaued. He concluded that an uncorrected limit was irrelevant for pilots, as long as they can be corrected to the required standard. Australia’s aviation authorities listened and changed the visual acuity standards, opening an aviation career pathway for many pilots who were otherwise shut out under the old rules.
“The department changed the regulations and said we don’t mind what your uncorrected vision is, as long as you can be corrected – and they also stipulated that you need to carry a second pair of glasses,” Gibson recalls.
“It was estimated that the probability of losing one pair of glasses is 1 in 10,000, and if you’ve got another pair in your bag it’s 1 in 100,000, so there is a better chance of the wings falling off or the engine stopping, so it was decided that it was an acceptable risk.”
Fighting for recognition
In addition to this work, Gibson was involved in training designated aviation medical examiners (DAMES) who needed to complete modules on vision defects and flying as part of their training course (ACCAM). Professor Algis Vingrys was a Qantas pilot in a previous career who had been a subject in Gibson’s initial study and subsequently became interested in optometry as a career. Together, they presented the vision training day to the DAME course participants.
What’s ironic is that – while they could help establish new aviation standards and even run ophthalmic courses to update doctors on vision and eye problems – optometrists weren’t allowed to examine the pilots themselves. This was a job left for designated aviation ophthalmologists (DAOs).
This all changed in 1996 when ophthalmologist Professor Nitin Verma – the current RANZCO president – asked if the ACCAM DAME aviation medical course could be run in Papua New Guinea to train local aviation medical doctors who could not afford to do the program in Victoria.
En route to Port Morseby, the chartered executive jet was being flown by the then aviation medicine director, so Gibson seized the opportunity to point out the fact optometrists were unable to test pilots, despite some being highly trained in relevant fields, such as visual ergonomics.
Eventually, Gibson, South Australian optometrist Mr Neil Murray and Vingrys, were allowed to perform vision exams on pilots in the mid-1990s – a first for the profession.
This small group of optometrists were given the title of ‘designated aviation ophthalmologists’, and then ‘designated eye examiners’. This was until 2011 when the Civil Aviation Safety Authority (CASA) realised the title wasn’t embedded in legislation.
This served as the catalyst for the authority to formalise an agreement with Optometry Australia (OA) to establish a network of credentialed optometrists (COs) trained to conduct vision and eye examinations for pilot licensing.
After playing a considerable part in advocating for optometry’s involvement in aviation eye exams, Gibson and Murray – now a senior lecturer and clinical supervisor at the Flinders University optometry school – began running the course and still curate its material.
Today, the introduction of COs has also meant a greater geographical spread of aviation eye examiners in Australia, something that is closely watched and regulated by OA and CASA.
To date, there are around 155 COs and 145 DAOs involved in aviation eye examinations for approximately 30,000 Australian pilots and 1,000 air traffic controllers each year.
According to CASA, more than 80% of flight information is acquired by pilots visually from aircraft instruments or through visual information outside the cockpit. Good visual function is necessary for safe performance of most of the aviation activities including pre-flight checks, take- off, navigation, landing and proper use of displays, dials, gauges, and maps in modern cockpits.
Pilots with a Class 1 licence (commercial) and Class 3 (air traffic controller) are required to have an aviation eye examination performed by a DAO or CO when they first have their licence issued. Once they turn 60, eye exams are performed every two years. During the intervening years, DAME doctors perform frequent overarching aviation medical exams which involves a rudimentary eye test – if issues are spotted pilots are referred to a DAO or CO for further assessment.
Although visual environment and demands vary with different aviation operations and medical standards, for commercial pilots some of the main criteria include; distance visual acuity of 6/9 or better in each eye separately and 6/6 or better binocular (with or without correcting lenses); being able to read (with or without correcting lenses) an N5 chart binocularly in the range of 30 to 50cm, as well as an N14 chart binocularly (with or without correcting lenses) at 1m.
For contact lens wearers, pilots need to be able to wear them for twice the projected flight or duty time without deterioration in visual acuity or discomfort. Also, the pilot must have backup spectacles available and pass the appropriate standards with them immediately after removing their contact lenses.
Colour perception is also a major factor, and can often be a determining factor in whether a person is fit to become a pilot.
Gibson says if pilots fail the Ishihara screening test, they can be referred for a Farnsworth Lantern test. This test was initially developed 70 years ago for maritime signal recognition and involves showing a pair of vertically oriented lights consisting of combinations of either red, green or white. The test subject is asked to identify the two colours, in nine different parings. If passed, the pilot is regarded as “colour defective safe” but if failed then further tests or an occupational field test can be arranged.
“In some cases, pilots with colour vision issues can get through to gaining their commercial pilot licence but they may never get a job because the employers have the right to demand their own standards and may reject an applicant with a significant colour vision deficit,” Gibson says.
He says this has led to a lot of controversy, with some colour-defective pilots saying better instrument design is required, or correct colour detection isn’t important, and that there shouldn’t be any colour vision regulation.
“I don’t agree with this view,” Gibson says. “A protanopic subject might match a full 100% bright red light with a 30% dull yellow light and declare them to be identical which in my view is a safety issue. Colour displays are common in the aviation industry such as electronic displays, colour coded radar and warning signals.”
“We always advise young colour defective applicants, especially the red deficient protanopics, that their flying career options may be limited.”
Gibson says visual field loss and glaucoma is a common defect in older pilots, which can have serious ramifications for their careers.
“The question becomes how significant is it, is it going to impinge on their ability to do the job and how often should we be reviewing these pilots? Sometimes their careers are on the line and it can be an important and emotional situation. We always reinforce that CASA are interested in keeping them flying and not stopping them, but it just needs to be in a safe manner,” he says.
One issue Gibson sees with current testing methods is the use of the binocular Esterman screening test for visual fields. It uses bright targets and binocular viewing and is difficult to fail. He’s seen examples of stroke victims who can obtain a strong 85% seen score and being declared as safe to drive despite missing 50% of their visual field on monocular testing.
“That might be good if you’re testing a grandfather’s ability to drive the car down to the shops but it’s a different issue when you’re in charge of a plane full of passengers,” he explains.
“We always use threshold monocular field tests as a baseline and can now do binocular threshold testing on the Medmont perimeter. Monocular visual field greyscale maps can also be superimposed to gain an impression of where both eyes share significant losses. This provides a more valid evidence-based result and can inform the CASA aviation medical staff on the area of shared loss from they can determine the operational safety risk of the field defects.”
He continues: “The regulator must establish the likelihood and consequence of a critical visual cue being hidden by a binocular field loss and determine if a safety issue is present.”
In other cases, Gibson has seen keratoconus patients who can achieve good results with contact lenses but do not achieve the required corrected vision with backup spectacles.
“One pilot could pass with specs in one eye but failed in the other. We did the exam and spelled out the facts in a detailed report explaining that the pilot was binocular with good vision and comfort using his RGP lenses, but a backup spectacle option was not practical for his more affected eye,” he says.
“He was approved as a commercial pilot to use his monocular backup glasses when required. His limited depth perception with the backup spectacles precluded him from low level flying such as crop dusting or helicopters. He was not interested in these activities and delighted to continue his commercial role as a pilot of twin-engined light aircraft.”
Becoming a credentialed optometrist
When optometrists subscribe to the CASA credentialed optometry course, Murray – who helped advocate for optometry’s recognition in aviation alongside Gibson – says many often remark on the fact they’re resurrecting knowledge and skills they learned at university.
Physiological issues associated with flight, including hypoxia, fatigue and illusions are taught as part of the course, while optometrists should look for the likelihood of incidents that could occur mid-flight such as a retinal attachment or acute angle-closure glaucoma attack.
Alongside Gibson, Murray attends aviation and aerospace conferences to get the most updated information in the field, with the most relevant aspects incorporated into the CO course.
“When a pilot is at close to 10,000 feet and isn’t using additional oxygen, their peripheral vision is going to reduce, for example, so there is quite a widespread grounding in all these functional issues that are specific to aviation, which isn’t necessarily taught to ophthalmologists who don’t do any aviation specific training,” he explains.
Murray says optometrists need to keep detailed records of their pilot examinations which can be audited. They also need be able to perform tests like gonioscopy and indirect ophthalmoscopy and confirm they have access to equipment such as a contrast sensitivity charts and glare testing equipment.
The introduction of COs, he says, has helped overcome maldistribution of aviation eye examiners, which once meant pilots in isolated areas needed to travel hours to see a DAO.
Optometry Australia (OA) national professional services advisor Ms Sophie Koh says CASA is satisfied with the number of COs, but there are still some geographic gaps, particularly in the rural and regional locations near growing airfields.
“And it’s not just defence, but other types of airfields. In regional places like Karratha in WA and Port Lincoln in SA, we have been supportive of optometrists in those areas and the need for them to be credentialled to support the aviation community,” she says.
“In metro CBD areas we tend to have saturation and the question of: ‘why don’t we just accredit everyone that’s interested?’, is always there. The argument is we don’t want optometrists to end up seeing one aviation patient per year. There’s no incentive to do so. There are certain clinical competencies each optometrist needs to upkeep, including
familiarity with the aviation standards and CASA’s medical record system and statutory declarations, annual fees and paperwork too.
She continues: “Optometrists also have to pay a fee annually to maintain their accreditation with us and every four years they need to have an upskilling assessment to satisfy CASA’s contracting requirement to make sure these optometrists remain competent, so it needs to be worth their while.”
Koh says OA intends to run the course every three years.
“From a job satisfaction and scope-of-practice point of view, the optometrists that do see a lot of aviation patients enjoy it,” she says.
“As optometrists we get fixated on visual acuity and ocular disease often, and there are many other functional aspects such as contrast, colour vision, ocular movements, glare sensitivity and visual illusions that are taught at university but don’t get many opportunities to apply that knowledge in the context of occupational vision such as with our aviation patients.”
Space flight and beyond
An intriguing component of the CO course is the issue of spaceflight, and what role eyecare professionals may play.
Murray says aviation medical examiners are required to be part of the Australasian Society of Aerospace Medicine (ASAM), which is optional for eye examiners. Via ASAM, he’s become involved with the Royal Australian Air Force and completed the ASAM course on space medicine which involved presenters from NASA.
In recent years, NASA has been working to solve a major issue with astronauts who return from the International Space Station with lasting changes in their visual acuity, referred to as spaceflight associated neuro-ocular syndrome (SANS).
“The micro-gravity situation in Low Earth Orbit is such that there is no gravitational effect to keep the spinal fluid towards the lower lumbo-sacral areas of the spine and this fluid moves more towards being within the skull,” Murray explains.
“This in turn raises the intra-cranial pressure on the brain causing a number of structural and functional changes. There is swelling of one or both optic nerves between the brain and the back surface of the globe of the eye. Additionally, there is increased fluid pressure within the orbital fat that is behind the globe of each eye. This pressure flattens that back surface of each eye, reducing the overall length of the eye, and making the astronaut’s eye focus become more hypermetropic. There are also changes within the retina and choroid of the eye.”
Murray says with an impending boom in space tourism, the industry is beginning to think about the potential implications.
“We’re already discussing what happens in a few years’ time when people go into space, and how we should be advising them.”