The development of cataract is common with aging and affects more people who have been particularly exposed to UV light. For this reason it is common in farmers and pilots. Smoking may be a risk factor.
This condition is seen principally with advancing age.
Is less common and is found in a ratio of roughly 2:3 when compared to nuclear cataract. Exposure to UVB is a risk factor. Abdominal obesity also appears to add to the risk of developing cortical cataract. There is some evidence suggesting an association between cortical cataract and dementia.
Is mainly seen in younger adults and is a posterior opacity. If central, the reduction in visual acuity can be severe and rapid. Systemic corticosteroid use, inhaled corticosteroid use after the fourth decade of life and alcohol use may increase the risk of developing subcapsular cataract.
Cataract may result in problems with glare. In addition, if the visual axis is affected, visual performance may be severely impaired in bright light, when the pupil is narrow. In some cases deterioration well below Part 67 medical standards can occur in as little as six to twelve months.
For this reason the ME should look for any sign of cataract or decrease in vision in the aging pilot and refer for a special eye examination report if any is present or suspected. If present, frequent surveillance is warranted.
Treatment is surgical, via cataract extraction and most commonly Intra Ocular Lens Implant (IOL).
Monofocal lens implants are acceptable for certification providing that a special eye report at not earlier than 3 weeks post IOL implant demonstrates visual performance within the standards and absence of complications. Overall around 85% of patients achieved best corrected visual acuity of 6/12 or better at 3 months and 80% are within one dioptre of the expected refraction.
IOLs offer the opportunity to correct refractive errors at the time of surgery. Thus sufficient time must have elapsed since the surgery to allow for neuro-adaptation to the new refractive characteristics if these are markedly different. While a waiting time of four weeks is often sufficient prior to resuming duty, up to three months may be appropriate, depending on the change in refraction. New corrective lenses must generally be obtained.
Post-operative anisometropia must be considered. This is a condition by which there is a difference of refraction between both eyes. As surgery is often performed one eye at a time, there is potential for significant anisometropia, which may take time to adapt to. Anisometropia leads to aniseikonia (difference in images size) if wearing spectacles. Contact lenses avoid this problem.
An anisometropia of 2.5 Dioptres or more should be considered as being of aeromedical significance. A recent, less than 6 months duration, anisometropia of 2.0 Dioptres of more should be considered as being of aeromedical significance.
Multifocal lens implants are now in common use. Multifocal IOLs generally provide for adequate near and distant visual acuity if of the appropriate power, but may not provide adequate intermediate distance vision. The technology is still in development. Intermediate vision is sometimes dealt with by using trifocal IOLs or different types of multifocal lenses in each eye.
The ME should inquire specifically about the use of multifocal IOLs. This is because these lenses may result in halos and glare and provide for variable visual performance. In particular decreased contrast sensitivity is an inevitable consequence of this type of lenses. Some of the problems associated with IOLs implants are outlined in the following table, as found in one study:
CAA considers the possible adverse visual symptoms as being of aeromedical significance and generally not acceptable.
The ME should suspect the presence of multifocal IOLs if the applicant is able to meet the near and distance visual standards without refractive correction. Checking the intermediate distance visual acuity may be revealing, and should be performed in all cases of new IOLs implants, Class 2 applicants included. However some lenses may correct for intermediate distance as well. A clear statement by the ophthalmologist who has undertaken the procedure or a copy of the operating notes should be obtained to ascertain the type of IOLs that have been implanted. The exact type and model of IOL should be recorded for each eye.
An applicant who has recently undergone an IOL implant should provide:
An applicant who meets the following criteria may be assessed as having a condition that is not of aeromedical significance if:
An applicant with multifocal IOLs can expect to have to demonstrate adequate visual performance through specialised testing. If a certificate is issued under the flexibility process, the carriage of passengers commercially, night flying and IFR privileges may be curtailed.
Applicants, particularly commercial pilots, need to be aware of the likely restrictive implications or even ineligibility to a medical certificate following multifocal IOLs implantation.
If no implants have been used, the necessary refractive correction generally requires very high power convex corrective lenses. This is unlikely to be acceptable.