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11.3.27 Vision chart projectors have several advantages including availability of a selection of different
slides, the ability to display only one row of symbols at a time and much better durability than the less expensive
printed charts.
11.3.28 Printed vision charts should be matt white and the symbols should be matt black. The gap in the
Landolt rings must subtend an angle of 1 minute of arc at the prescribed distances. The Snellen letters are
formed within a square subtending 5 minutes of arc at the prescribed distances or (on some charts) within a
rectangle 4 minutes in width and 5 minutes in height and are made so that the constituent parts of the letter
subtend 1 minute of arc.
11.3.29 Testing programmes to measure visual acuity, colour perception and other aspects of visual
function are available for personal computers. Some of these programmes are used for testing aviation
personnel but standardization remains a challenge.
11.3.30 Examiners should not allow the applicant to squint during testing as using the eyelids as a
stenopaeic slit may mask refractive errors. No error should be allowed per line of ten symbols. In cases where
test letters other than Landolt rings are used, the Licensing Authority should ascertain that the methods used
for measuring visual acuity will provide comparable results.
III-11-10 Manual of Civil Aviation Medicine
11.3.31 Any degree of myopia results in reduced visual acuity. A significant degree of myopia, i.e. –0.75 D
or more, will be detected during the screening examination, provided the applicant is not allowed to squint. In
contrast, low or moderate degrees of hyperopia (hypermetropia), especially in young individuals, are
compensated for by accommodation, and such applicants will have normal distance visual acuity and may not
be detected during an ordinary screening examination. The full amount of hyperopia can only be measured by
refraction under cycloplegia, but this possibility is not generally available to the designated medical examiner.
The +2.5 D lens test
11.3.32 A useful screening test for hyperopia is to have applicants who read 6/6 or better without correction
read the distance acuity chart while looking through a +2.5 D spherical lens. This can be done by holding a
single lens in front of each eye or, more conveniently, by using a pair of full-size reading spectacles with +2.5 D
lenses. Each eye is tested separately. If the eye is emmetropic, vision through the +2.5 D lens will be blurred,
and the visual acuity will be reduced by about two lines on the Snellen chart. If the distance acuity is not
reduced by the +2.5 D lens and the applicant sees just as well through these lenses as without them, some
hyperopia is present.
11.3.33 Applicants who fail the +2.5 D lens test should normally be referred to a qualified vision care
specialist for evaluation.
Annex 1 requirements for distant visual acuity
11.3.34 Annex 1 requirements for distant visual acuity are as follows:
Class 1:
6.3.3.2 Distant visual acuity with or without correction shall be 6/9 or better in each eye separately, and binocular visual acuity
shall be 6/6 or better. No limits apply to uncorrected visual acuity. Where this standard of visual acuity can be obtained only with
correcting lenses, the applicant may be assessed as fit provided that:
a) such correcting lenses are worn during the exercise of the privileges of the licence or rating applied for or held; and
b) in addition, a pair of suitable correcting spectacles is kept readily available during the exercise of the privileges of the
applicant’s licence.
Note 1.— 6.3.3.2 b) is the subject of Standards in Annex 6, Part I.
Note 2.— An applicant accepted as meeting these provisions is deemed to continue to do so unless there is reason to
suspect otherwise, in which case an ophthalmic report is required at the discretion of the Licensing Authority. Both uncorrected
and corrected visual acuity are normally measured and recorded at each re-examination. Conditions which indicate a need to
obtain an ophthalmic report include: a substantial decrease in the uncorrected visual acuity, any decrease in best corrected
visual acuity, and the occurrence of eye disease, eye injury or eye surgery.
Class 2:
6.4.3.2 Distant visual acuity with or without correction shall be 6/12 or better in each eye separately, and binocular visual
acuity shall be 6/9 or better. No limits apply to uncorrected visual acuity. Where this standard of visual acuity can be obtained
only with correcting lenses, the applicant may be assessed as fit provided that:
a) such correcting lenses are worn during the exercise of the privileges of the licence or rating applied for or held; and
b) in addition, a pair of suitable correcting spectacles is kept readily available during the exercise of the privileges of the
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Manual of Civil Aviation Medicine 2(39)
