Lazy Eye: Strabimus & Phorias

March 4, 2024

A strabismus, also known as a 'lazy eye' or 'crossed eyes' is a relatively common condition affecting 2-4% of the population. A strabismus refers to abnormal alignment of the eyes. Tropias and phorias indicate a tendency for the eyes to drift slightly. Both of these conditions raise concerns related to depth perception, binocular vision, and overall visual acuity. These conditions can potentially affect a pilot's ability to safely operate an aircraft, especially during critical phases of flight. For this reason the FAA cares about these conditions and requires the Aviation Medical Examiner (AME) to perform a few tests during a pilot exam for medical certification.

Testing for Phorias and Tropias

FAA Guidance

The FAA recognizes that each case is unique and approaches the certification process with careful consideration. Pilots with these conditions are not automatically disqualified from obtaining a medical certificate. Instead, the FAA evaluates each individual case based on several factors:

  1. Severity of the Condition: The FAA requires the AME to assess the severity of strabismus or phoria, considering factors such as the degree of misalignment or deviation of the eyes and whether it can be corrected. A phoria is measured by the numbered of diopters required to correct it (see video above). The FAA standard is for a limit of 6 diopters for horizontal misalignment and 1 diopter for vertical misalignment.
  2. Visual Acuity: Pilots must meet specific visual acuity requirements, both with and without correction, to ensure they can adequately perceive and respond to visual cues in the cockpit and the surrounding airspace. This standard is 20/20 for distant vision and 20/40 for near vision for Class 1 or 2 certificates. Visual acuity can be affected by history of strabismus and phoria.
  3. History and Treatment: The FAA reviews the pilot's medical history and any treatments undergone for the condition, such as surgery, vision therapy, or the use of corrective lenses. It is important that the AME ask if the pilot has ever experienced double vision (aka diplopia)
  4. Functional Ability: Pilots must demonstrate their ability to perform essential flight tasks, including maintaining proper scan patterns, interpreting cockpit instruments, and accurately judging distances.
  5. Special Issuance: In some cases, pilots with strabismus or phoria require a special issuance medical certificate. This is usually only required if a pilot has a phoria outside the above stated medical standards AND has any history of double vision or other failed vision test.

FAA Policy on Phorias, Tropias and Double Vision


It's essential for pilots with these conditions to undergo thorough evaluations by qualified aviation medical examiners (AME's) to determine their eligibility for certification. In many cases, pilots may be required to see an eye specialist and have a special form completed - the 8500-7. As long as pilots and applicants meet the above standard and do not have a history of double vision, they can be medically certified without special issuance or SODA. Consulting with an AME familiar with FAA policies regarding ocular conditions can provide valuable guidance throughout the certification process.

If you have a history of strabismus, tropia, phoria, or other medical condition affecting your vision, you may wish to consult an AME today.

You can schedule a consult with an AME or one of our specialists here today!

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