The excellent documented results concerning efficacy and safety of the different modalities of refractive surgery in the general population make this type of procedure the desired option for the correction of ametropias, particularly when the patient does not wish to use other kinds of optical correction such as glasses or contact lenses.

However, the elective nature that is usually associated with this type of procedure does not arise when we consider specific professional groups, becoming almost mandatory in ametropic patients wishing to ingress in particular functions within the three branches of the Armed Forces.

The high physical requirement associated with training and performance of military tasks that are common to the three branches and the specificities of each of them raise the need for an optimal visual performance, translating into a legal framework that describes minimum requirements of uncorrected and corrected visual acuity (Tables 1 and 2).¹

Correction of ametropia through glasses or contact lenses, while visually satisfactory, may compromise the correct performance of military functions: in case of loss/damage of glasses or incompatibility with modern visual systems, in case of contact lens displacement in visually demanding situations and in corneal injury associated with poor hygiene in a war theatre.

This concern also gave rise to the autonomous refractive surgery program of the United States Armed Forces.²

The current legislation in our country does not establish specific limitations to the performance of refractive procedures in candidates to the Armed Forces or elements in functions, referring only vaguely to "sequelae of myopia surgeries," which we can interpret vaguely as the possible presence of a corneal flap or an intraocular phakic lens. During the preparation of this document, new legislation is being drafted, which will address this aspect in a more specific and concrete way.

The specificities of the function to be performed should be considered when advising the candidate for refractive surgery, also analyzing the advantages and disadvantages of each type of procedure, whether based on ablative corneal surgery or intraocular phakic lens implantation.

Visual correction through corneal ablation techniques can be performed through surface surgery, conventional surgery with the creation of a corneal flap and, more recently, SMILE-type intra-stromal ablation.

Surface ablation requires the removal of the epithelium, implies a more extended healing period and recovery of the visual acuity when compared to the other techniques.^3,4.

This aspect may be relevant in a situation in which a candidate to the Armed Forces has a short deadline to perform physical tests with the minimum uncorrected visual acuity criteria.

On the other hand, surface techniques are those that offer a better safety profile if we consider the potential of ocular trauma associated with these people, as well as a more favorable biomechanical profile.

The fact that many candidates undergo surgery at a very young age (between the ages of 18 and 22), makes the surface technique more indicated by the aspect of a better corneal biomechanical safety profile (preventing secondary corneal ectasia); as well as by the fact that the ablation magnitude is much lower, allowing the possibility of re-treatment. Conventional LASIK surgery would be more appropriate if faster visual recovery or treatment of higher ametropias (between -4.00 and -7.00 D) is needed.

One of the disadvantages associated with Lasik is the need to create a flap during the procedure.

Considering that military activity is prone to trauma due to the inherent intense physical contact, the risk of flap complications is a concern, since there are cases described even several years after the procedure.⁵.

Another associated disadvantage would be the greater depth of the ablation performed and its relation to the candidate's young age. These two factors together are associated with a higher risk of developing secondary ectasia after surgery.

Finally, we comment on the usefulness and indications of phakic intraocular lens implantation: it is the technique of choice for treatments of myopia greater than -6.0 D or hypermetropia greater than + 4.0D, provided the biometric criteria of the anterior segment is fulfilled.

They also allow the treatment of lower ametropias that are not indicated for corneal surgery, are reversible and offer visual quality (especially in mesopic, scotopic or low contrast situations) superior to any corneal technique that induces a significant change in the corneal curvature.

The use of a phakic intraocular lens in the sulcus for the correction of moderate/high ametropias in the military was analyzed by Parkhurst, reporting excellent results regarding efficacy and safety.⁶.

In an interesting experiment, Tan and Nah submitted a pilot aviator candidate with a previous ICL (Staar) lens implant to different magnitudes of gravitational force (up to + 9G)7: rotational lens stability and absence of lens damage were observed, attesting to the safety of this type of lens for the performance of Air Force pilots.

Analyzing different techniques, Parkhurst compared visual performance after wavefront-optimized LASIK and ICL lens in military people.

The intraocular lens showed better performance under low light conditions and with night vision glasses, which may be relevant in certain scenarios.⁸.

In summary, the application of refractive surgery techniques to young people who are candidates for military positions must fulfill three major requirements: general indications for refractive surgery, legal requirements described in the Portuguese law (Diário da República) and the association between the first two and a third requirement, which is the need to choose the technique according to the young age of the patient, the higher risk of trauma as well as a possible and probable progression of the refractive error in the years following surgery.

Table 1: Table of general sensory conditions in Ophthalmology for the Navy Branch.

Table 2: Table of general sensory conditions in Ophthalmology for the Army and Air Force Branch.