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11.4.58 Complications following refractive surgery are infrequent but a formidable list of problems has
been reported including post-operative infections, loss of best-corrected visual acuity, and blindness.
11.4.59 The most important risks, from an aviation standpoint, are loss of best-corrected visual acuity,
undercorrection or overcorrection, fluctuation in vision at different times of the day, glare, “halo” or “starburst”
effects due to corneal haze, loss of contrast sensitivity, loss of low-contrast visual acuity, and regression
towards pre-operative refraction levels.
11.4.60 Significant changes in refraction during the course of the day have been reported in RK patients for
as long as four years after the surgery but such problems are uncommon, and the great majority of patients see
well within days or weeks after their surgery.
11.4.61 Visual recovery after PRK and LASIK is generally more rapid than after the other procedures, and
these excimer laser procedures have to a large extent replaced RK although there are still specific indications
for RK.
11.4.62 PRK and LASIK procedures usually leave no visible corneal scarring, so it is easy for an applicant
to conceal the fact that he has had refractive surgery. Examiners should be aware of this because the usual
visual acuity testing methods will not reveal the impaired low-contrast sensitivity, which may occur after
refractive surgery and which might impair visual performance in the aviation environment.
11.4.63 The recovery rate, predictability and regression rate following refractive surgery depend to some
extent on the pre-operative refractive error and on the type of surgery. The following is suggested as a guide to
the minimum interval between withdrawal of eye drops after refractive surgery and the resumption of duties:
Pre-operative refractive error of up to 6.00 D spherical equivalent:
RK 3 months
PRK 3 months
LASIK 3 months
Pre-operative refractive error 6.00 to 10.00 D spherical equivalent:
III-11-34 Manual of Civil Aviation Medicine
RK 6 months
PRK 6 months
LASIK 3 months
Greater than 10.00 D spherical equivalent:
RK 6 months
PRK 6 months
LASIK 6 months
11.4.64 It must be emphasized that applicants who have had refractive surgery and are being considered
for medical certification or re-certification should meet the following criteria:
a) The surgery is uncomplicated
b) Vision is stable
c) There is no corneal haze and no complaints of glare, halos or “ghosting”
d) The result meets the visual requirements of Annex 1, and the assessment must be based on
measurements made by a qualified vision care specialist acceptable to the Licensing Authority
e) There should be follow-up examinations by a qualified vision care specialist six months after
return to duty and yearly thereafter.
11.4.65 Individuals contemplating refractive surgery must be made aware of the risks involved and should
be told that having the surgery might result in a delay in return to duties as aircrew or air traffic controller or, if
complications occur, in the permanent loss of medical certification.
11.5 VISUAL FIELDS
11.5.1 While good visual acuity is clearly a requirement for safe operations in the aviation environment,
an adequate field of vision is also essential. The proper location of oneself in space and the location and
assessment of movement of other objects in the surrounding space are necessary for safe operation of aircraft.
11.5.2 That portion of physical space visible to an eye in a given position looking straight ahead is the
monocular visual field. The visibility of an object in the visual field depends on the size of the object, its
brightness, the contrast of the object to its surround, and its location in the field of vision. Visual acuity
diminishes rapidly as one moves away from the retinal fovea. Ten degrees eccentric from the fovea visual
acuity is only 6/30 (20/100, 0.2).
11.5.3 The extent of the visual field can be measured using targets of different size and different
brightness. In this way the (differential) sensitivity of the various parts of the retina can be determined and the
results drawn on a chart. When targets of different size are used to determine the threshold of visibility and the
points where each target just becomes visible are plotted on a chart, joining these points results in a series of
concentric, approximately oval curves called isopters. Thus isopters are lines joining points of equal sensitivity.
Part III. Medical Assessment
Chapter 11. Ophthalmology III-11-35
The larger an object the further out to the periphery of the field will it be perceived. In a normal eye the isopter
for a 3-mm white test object will extend approximately 95 degrees temporally, 60 degrees nasally, 60 degrees
　
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