Total Flight Hours, Irritated and Burning Eye and Risk of Mild Myopia in Civilian Pilots in Indonesia

Latar belakang: Miopia merupakan kelainan refraksi yang sering terjadi di antara penerbang. Penelitianini bertujuan mengidentifikasi beberapa faktor risiko dominan terhadap miopia ringan pada penerbang sipildi Indonesia.Metode: Subyek adalah penerbang sipil pria berusia 21-45 tahun yang dipilih secara purposif di antara yangsedang melaksanakan pemeriksaan kesehatan berkala di Balai Kesehatan Penerbangan Jakarta. Data tajampenglihatan dan gula darah didapatkan dari rekam medik. Miopia ringan adalah subyek dengan penurunantajam penglihatan dengan koreksi lensa -0,25 sampai dengan -0,30. Analisis data dengan regresi Coxmenggunakan Stata 10.Hasil: Persentase miopia ringan dalam penelitian ini sebesar 36%. Faktor risiko dominan terhadap myopiaringan adalah jam terbang total, riwayat orang tua myopia, dan gejala iritasi dan gatal mata. Subyekdengan dibandingkan dengan yang kurang dari 1000 jam terbang 28% lebih tinggi berisiko myopia ringan[risiko relatif suaian (RRa) = 1,28; 95% interval kepercayaan (CI) =1,00-1,64; P = 0,047]. Subyek dengandibandingkan ttanpa riwayat orang tua myopia 32% lebih tinggi berisiko myopia ringan (RRa = 5,32; 95%CI = 3,75-7,55; P = 0,000. Sedangkan subyek dengan dibandingkan tanpa gejala iritasi mata 48% lebihbesar berisiko miopia ringan RRa) = 1,48; 95% CI = 1,19-1,85; P = 0,001). Subyek dengan dibandingkantanpa gejala iritasi mata 46% lebih berisiko miopia ringan (RRa = 0,46; 95% CI = 0,26-0,83; P = 0,009).Kesimpulan: Jam terbang total lebih dari 1000 jam, riwayat orang tua miopia, iritasi mata merupakanfaktor risiko dominan terhadap miopia ringan pada penerbang sipil di Indonesia. (Health Science Journalof Indonesia 2016;7:49-53)Kata kunci: miopia ringan, penerbang sipil, jam terbang, Indonesia Background: Spatial orientation is the main problem to pilots that determined by visual, vestibuler andpropioseptif. This study aims to identify several dominant risk factors related to mild myopia in civilianpilots in Indonesia.Methods: This cross-sectional study using using purposive sampling. Subjects answered the questionaire.Data was extracted from the medical record. Cox regression analyses using Stata 10.Results: The subject consisted of 21-45 years old male civilian pilots who performing scheduled medicalcheck up at the Civil Aviatian Medical Centre. We found that 36% of the pilots had mild myopia, and thedominant risk factors were total flight time for 1000 hours or more, parental myopia, as well as irritatedand burning eyes. Those who had compared to did have total flight hours for 1000 hours or more had 28%more risk to have mild myopia [adjusted relative risk (RRa) = 1.28; 95% confidence interval (CI) = 1.00 to1.64; P = 0.047]. In term of parential myopia, those who had compared who did not have parential myopiahad 32% more risk to have mild myopia (RRa = 1.32; 95% CI = 3.75-7.55; P = 0.000). Moreover, thosewho had compared to who did have irritated and burning eyes had 48% more risk to have mild myopia(RRa = 0.46; 95% CI = 0.26-0.83; P = 0.009).Conclusions: Total flight 1000 hours or more, parental myopia, as well as irritated and burning eyes were dominantrisk factors for mild myopia in civilian pilots in Indonesia. (Health Science Journal of Indonesia 2016;7:49-53)

Myopia is the most widely refractive error experienced by civilian pilotin the United States in 2004. 1 The prevalence of myopia in the USAF airmen at 21.9%. 2 Aeromedical concern for myopia is correction with glasses or contact lenses that do not fit or are not balanced will degrade stereopsis and contrast sensitivity and can also induce the onset of ocular pain and fatigue (asthenopia). Myopia also increased the risk of retinal detachment, open-angle glaucoma and retinal degenerations such as lattice. 3 Prevalence of myopia are more frequent in individual with a history of parental myopia compared with individual who do not have myopic parents. Environmental factors that can affect the risk of mild myopia in pilots, among others, altitude, humidity, acceleration, vibration, inadequate lighting and cockpit ergonomics. Low humidity in the cabin can cause dryness and irritation of mucous membranes-espe cially the eyes and nasopharynx. In most commer cial aircraft, the cabin pressure can be monitored but remained mild hypoxia can interfere with dark adaptation, visual field and a sharp decrease of vision and increased intraocular pressure. System in the plane due to the characteristics and limitations of existing designs, including other properties such as aircraft manuals, procedures, level of automation, control panels, alarms and warning systems, emer gency systems and all existing designs. [4][5][6] This study aims to identify the effect of total flight hours, age, parental history of myopia and visual fatigue symptoms on the risk of mild myopia in a civilian pilots in Indonesia

METHODS
This cross-sectional study was conducted among male civilian pilots aged 21-45 years old during periodic health examination at the Ministry of Transportation Flight Health Center in Central Jakarta. Data were collected by self-questionnaires, and the data visual acuity results of refraction was extracted from data base of the Center during the period of May 5 to 21, 2014.
Myopia is a mild decrease in visual acuity away where the light entering the meet in front of the retina. Correction of the concave lens, -0.25 s / d -3.00. (PERDAMI) best corrected visual acuity with 20/20. Normal is a subject that gets the same exposure without refractive disorders of decreased visual acuity. Examination of visual acuity using the Snellen chart for 6 meters.
Risk factors studied were total flight hours, age and visual fatigue symptoms experienced by civilian aviators. Total flight hours was divided into two subgroups: 999 hours or lessof flying hours and 1000 hours or more. Aged was divided into two groups (21-34 years and 35-45 years). Parental history of myopia divided into: yes and no.
Symptoms of visual fatigue was the inability of the visual system to maintain the effectiveness and efficiency of work or in the presence of the following signs or symptoms: dry eyes, itching, burning, pain, irritation, difficulty to focus and look for lines, blurred vision or foggy letters. For eyestrain symptoms are grouped into; not perceived, sometimes perceived, and often perceived. For visual fatigue were grouped into: not noticeable at all, somewhat noticeable, extremely noticeable.
Data analysis by Cox regression using Stata 10. Ethical approval was received from the Health Research Ethics Committee of the Faculty of medicine, University of Indonesia. This research was approved by the Head of Flight Health Ministry of Transportation.

RESULTS
The number of pilots who were willing and qualified to be the subject of as many as 336 people. Three people were excluded due to severe myopia (lens correction more than -3.00) remaining 333 study subjects consisted ot 213 subjects had normal visual acuity and 120 subjects (36%) with mild myopia. Table 1 shows the subjects who had mild myopia were equally distributed in terms of age. OThose who had total of 1000 hours of flying hours or more had a 55% higher risk of experiencing mild myopia. Table 2 shows that the normal subjects experienced mild myopia appears to be distributed equally in terms of visual fatigue symptoms of dry eyes, watery eyes, heaviness of eyes, shivering/jumping.
Compared with their respective respective basic comparison groups, the subjects who experienced symptoms difficulty of focusing, pain, problems with line tracking, foggy letters and eye irritation; gritty; burning more likely had more risk to experience mild myopia.  7 Research has not been obtained linking between flight hours and the onset of mild myopia or other refractive disorders make it difficult for authors to compare. Increased flying hours experienced civilian pilots in this study resulted in an increase in the environmental factors that influence the risk of flight of myopia, the inadequate illumination in the cockpit, the strong bright light reflection (glare), vibration and poor ergonomics.
These results indicate the risk of myopia is 5 times greater in subjects with parental myopia when compared with subjects whose parents do not myopia. In the 1996 study found a greater prevalence of myopia in individuals with parental myopia when compared with individuals whose parents do not myopia. Genetic marker that decreases myopia has not been identified. 4 It was found that before the onset of myopia, individuals with parental myopia have longer eyes. 8 A person with myopia parents have experienced a 32.9% probability of myopia than if only one parent (father or mother) that has the possibility of 18.2% and 6.3% probability when no parent myopia. 9 this study and a comparison study showed a hereditary predisposition to myopia Based on multivariate analysis in this study, the presence of two symptoms associated with mild myopia in a civilian pilot, difficulty to focus (P = 0.001) and irritation eye,gritty or burning (P = 0.009). Bangor, 2000 states above 9 symptoms related to visual fatigue. 10 Visual fatigue in pilotmay be associated with visual tasks while flying. Airmen perform near and far vision simultaneously. The instrument panel, weather, air pressure, humidity, and vibration will aff.ect the onset of symptoms of visual fatigue.
Vibration in aircraft instruments and printed material, especially in the range of 22-64 Hz, can significantly impair vision. Aviator in an aircraft must maintain visual acuity in two conditions -when observing conditions outside the plane and while reading the display in the instrument or in the cockpit equally being vibrated. Linear motion between the eye and the instrument panel will cause motion in the retinal image and reduce visual acuity. 11 The results of the study Watten and Lie, 1992 indicates the convergence miopisasi and fatigue (fatigue Vergence) under the influence of continuous visual work; showed significant changes in visual acuity, refraction and myopia that leads to a decrease in the capacity of accommodation and convergence. 12 The instrument panel in the cockpit is one of the environmental risk factors that may affect the onset of myopia in a civilian pilot. The development of technology can improve the ability of pilots to feel and see the surrounding environment; This enhancement includes panels on top of the head (head-up displays/ HDU), panel-track flight (flight-path displays), night goggles (night vision goggle), artificial vision system (syntetic-vision system) and panel-retinal laser (laser-retinal displays). Flights to use manual instruments (instrument flight /instrument flight rules /IFR) or using visual cues (visual flight/visual flight rules/VFR). Read instrument panel and flight status information is very different from the fly by using a visual perception of the environment. Displacement of the instrument flew into a visual landing can cause disorientation due to sudden changes in attention. 6 In this study assessment needs to consider the possibility of a bias there because the flight environment is not measured against the risk factors.
In addition, questions about symptoms of visual fatigue are subjective, so it can also lead to bias.