Anisometropia is a difference in the refraction characteristics of the two eyes. It can exist with any type of refractive error detailed later in this manual. The different refractive corrections needed for the two eyes result in different image size. This is called aniseikonia. The brain may be unable able to 'fuse' the images if the anisometropia is large. Contact lenses avoid this problem.
Information to be provided
A special eye report should be provided in the following circumstances:
- As required in the Timing of Routine Examinations GD [PDF 500 KB];
- On the first occasion that an applicant presents with a known or suspected difference of refractive error between the two eyes, other than minor;
- On the first occasion that an applicant presents with contact lenses;
- On the first occasion that an applicant presents with uncorrected distance visual acuity of 6/60 or worse in either eye;
- Every five years if an applicant has uncorrected distance visual acuity of 6/60 or worse, in accordance with ICAO recommendation;
- Every 2 years or as determined by the ME, if an applicant is young and the ME suspects that the refractive error has not yet stabilised. Alternatively, in this latter situation, the ME may elect to review the applicant and only refer if the standards are not met.
An anisometropia of 2.5 Dioptres or more should be considered as being of aeromedical significance.
A recent anisometropia (less than 6 months duration) of 2.0 Dioptres of more should be considered as being of aeromedical significance.