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applicant’s licence.
Note.— An applicant accepted as meeting these provisions is deemed to continue to do so unless there is reason to
Part III. Medical Assessment
Chapter 11. Ophthalmology III-11-11
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 3:
6.5.3.2 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.— 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.
Relationship between refractive error
and uncorrected visual acuity
11.3.35 There is considerable variation in the results of studies designed to determine the relationship
between refractive error and uncorrected visual acuity. Figure 11-3 gives approximate values for this
relationship. Examiners should note that myopes can often improve their uncorrected vision markedly by
squinting and that hyperopes can overcome their refractive error to a greater or lesser degree depending on
how much they are able to accommodate.
Figure 11-3. Approximate relationship between
visual acuity and refractive error
— — 20/600
— — 20/500
— — 20/400
— — 20/300
6/60, 0.1, 20/200
6/30, 0.2, 20/100
6/15, 0.4, 20/50
6/12, 0.5, 20/40
6/9, 0.7, 20/30
6/6, 1.0, 20/20
0 1 2 3 4 5
Refractive error in dioptres
III-11-12 Manual of Civil Aviation Medicine
Refraction
11.3.36 Clinical refraction means the diagnostic procedure used to determine the refractive error in the eye.
There are many ways to perform clinical refraction. Frequently, an objective component such as a retinoscope
or an automated refractor of some kind is involved and sometimes cycloplegic drugs are used in the process.
This is followed by subjective refinement of the results with the aim of providing a therapeutic prescription for
spectacles which will give the person good and comfortable vision. Not all persons with a refractive error
require correction with spectacles, contact lenses or by other means. In aviation, correction of a refractive error
is only needed when uncorrected visual acuity is substandard or when there is visual fatigue or an ocular
muscle imbalance related to that error. The determination of an appropriate optical correction for a person with
a refractive error should be made by a qualified vision care specialist.
Refractive errors
11.3.37 The refractive status of the eye depends on the curvature of the refracting surfaces (cornea and
lens), the axial length of the eye, and the refractive indices of the ocular media. The most important of these is
the axial length. Eyes which are longer than normal are usually myopic, and eyes which are shorter than normal
are usually hyperopic.
11.3.38 An eye which has no refractive error is said to be emmetropic. In such an eye, parallel rays of light
from a distant object are focused on the retina without the need for any accommodation so that objects in the
distance are seen clearly.
11.3.39 Light entering the eye from near objects will be diverging, and an emmetropic eye will need to
accommodate to see near objects clearly.
11.3.40 Most eyes have some error of refraction and are said to be ametropic. The errors of refraction are:
a) hyperopia (hypermetropia) — farsightedness
b) myopia — nearsightedness
　
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