The human eye is one of Nature’s God-given marvels- and unfortunately, one that many people take for granted. It is only when our eyes give us trouble that our attention is drawn to them. Thus most people are unaware of the plethora of diseases that eyes can be subject to. Symptomatically, pain, redness and loss of vision are important problems that require medical attention. However, eye problems can warn us of other health problems as well. That is why early diagnosis, prevention and cure of common eye diseases are all the more important.
Prevent Blindness America, an independent organization dedicated to eye care and the prevention of blindness in both old and young, characterizes some known symptoms of possible eye disease and impending vision loss. Among the more well known symptoms are dry eyes, itching or burning sensations, temporary loss of vision in one or both eyes (including side vision), halos, flashes or blurring of vision, and darkness or flashes before the eyes. It becomes all the more complicated if the person concerned has diabetes or high blood pressure, as these conditions can at any time exacerbate any existing eye diseases. Therefore proper care and regular checkups are recommended especially for these patients- as it is a means of keeping the eyes healthy, alert and free from disease (Prevent Blindness America homepage, 2004).

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The cornea is the part of the eye that helps us see. It works on the principle of taking and relaying images- much in the same way as a camera takes a film. However, when something goes wrong with the cornea, the images that it takes and presents to us becomes distorted. This happens when the shape of the cornea or the eye becomes maladjusted, with the consequence that the image relayed to the person is blurred or out of focus. Depending on what actually occurs in terms of focus error, we may become nearsighted (have problems seeing people or objects at a distance); farsighted (have difficulty seeing objects or people at close range) or the Retina may just produce distorted images of people or objects due to irregularities in the lens or cornea of the eye. Medical science has given the following names to these conditions: Myopia (nearsightedness), Hyperopia (farsightedness), and Astigmatism (distortion due to corneal or retinal malfunctions). All these three conditions are quite common, and fortunately all three are curable. Nowadays, both spectacles and contact lenses are easily available to correct nearsightedness or farsightedness- all you need is a proper eye check to indicate the power and type of lenses needed for a particular condition.
Combinations of myopia and astigmatism and hyperopia and myopia are also common and can be treated. For astigmatism, one has the option of going for either normal laser eye surgery or the more specialized procedures of RK, PRK, and more recently LASIK surgery.

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Since in scientific terminology the bending and focusing of light is called Refraction, the imperfections in the focusing power of the eye are called Refractive Errors. Consequently all corrective surgery done to correct these conditions has been given the name Refractive Surgery. Therefore RK, PRK, LASIK all come under this group of surgical procedures.
The development of the LASIK procedure has been somewhat of a breakthrough in approach; though a logical path of development exists from the oldest surgical procedure to the newest one. Moreover due to the quickness and ease of the newer procedures, the use of traditional laser eye surgery has now been relegated to treat the conditions of glaucoma, macular degeneration, diabetic retinopathy and presbyopia.
Basically, LASIK stands for “Laser Assisted In Situ Keratomileusis”. It is an outpatient procedure, performed by an ophthalmologist and is used to treat conditions of myopia, hyperopia and astigmatism. The Lasik procedure produces clear vision by reshaping the cornea. Whereas PRK, or Photo Refractive Keratectomy is a procedure used to correct only low degrees of myopia and astigmatism.
The basic difference between the two operating procedures is this: in PRK, a corneal flap is not created before the surgeon uses a laser to ablate the eye. In LASIK however, a knife called a excimer or micro-keratome, is used to cut a flap in the cornea. A hinge is left at one end of the flap. Then the flap is folded back to reveal the middle of the cornea (called the stroma). After this, computer controlled laser pulses are used to vaporize the defective part of the stroma, and finally the flap is replaced (Nationally Recognized LASIK Surgeons, 2004).

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A small group of surgeons prefer PRK to LASIK, because it avoids flap complications (despite post-operative pain and discomfort). Though both are surgical procedures, due to ease of operation and cost (the typical lasik procedure takes between 15-30 minutes and can cost between US$1000 for one eye to US$2500 for both eyes), LASIK has been advertised and touted as a miracle cure. The medical community has so far determined that LASIK operations fail in a minute 5% of total cases, however this figure may be far from accurate simply owing to a majority to people who are not satisfied with the results of the operation but do not know how to get proper redress in their individual situations.
As a means towards providing a higher proportion of success, doctors are inclined to ask patients to take a full eye examination as part of a pre-operative procedure to determine whether the patient is a good candidate for the operation. The pre-surgery tests typically include the following:

1. Checking for ocular irregularities in dilates
2. Measurement of refractive error
3. Measurements of pupil and corneal thickness
4. Map of corneal topography
5. Analysis of tear function
6. Discussion of medical history, lifestyles and expectations from the operation

If the results of the tests are OK (within the defined parameters determining a successful outcome), the patient is encouraged to go ahead and take the operation. Among the advantages of undertaking the LASIK procedure are the following:
1. Glasses/ Contact lenses will be unnecessary.
2. Discomfort associated with contact lenses will be eliminated.
3. Quality of vision will be better than that achieved with glasses or contact lenses.
4. Ability to pass the test for a Drivers License (most patients achieve the 20/40 vision needed for passing the test).

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However, the risks associated with LASIK cannot be denied. Among the risks affecting 5% of the patient population are the following:
1. Light sensitivity
2. Halos, glares and starbursts (this can however be touched up with corrective surgery)
3. Under-correction or over-correction
4. Irregular astigmatism (vision through cornea has wavy patterns)
5. Regression
6. Contrast sensitivity (difficulties with night vision).
It is also important to remember that patients in their 40’s or above suffer from presbyopia and will still need reading glasses.

Prior to the Lasik procedure, the surgeon will typically educate you as to the possible impact the surgery may have on your career. In addition to the cost involved, Lasik may affect any other medical conditions you may have. You may still need reading glasses, develop dry eyes, and the results may not be lasting. Lasik may affect your visual sensitivity, especially night vision. Therefore it is important to check that the doctor who is performing the procedure is experienced, informative, has the right equipment, and proper arrangements for long term care exist, if needed. You should be comfortable on all these counts before taking the operation.

The following are testimonials given by 3 patients who have had successful LASIK procedures:
“Being able to wake up every morning and actually see the alarm clock is something that I thought would never again happen to me. Since my experience with LASIK, I feel that I have been blessed with a miracle.” Melissa, Age 22 ((Laser Eye Surgery for Eye Diseases, 2004)

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“A few hours after the surgery I removed the protective glasses, looked at a tree in the distance (200-300 yards away), and tried to focus on the fine structure of its leaves. To my surprise, I was able to see almost every leaf, the different shades of green, and the tiny vibrations in the wind. My limitations were gone, making me feel younger, and giving me a future filled with clear horizons.” Michael, Age 34 (Laser Eye Surgery for Eye Diseases, 2004)
“I wanted to get LASIK performed because contact irritated my eyes and I didn’t like wearing my glasses while playing sports or going out. After the LASIK procedure, I can see the ball clearly, and I don’t have to worry about breaking my glasses. When I go out at night, I can look my best without having to squint to see things. I also like being able to wear regular sunglasses when it’s nice out, instead of paying to get special prescription ones made” Dave, Age 31 (Laser Eye Surgery for Eye Diseases, 2004).
However, debates on the effectiveness of Lasik surgery are still raging across America and other countries of the developed world. Lasik surgery is considered elective surgery, much on the same lines as plastic surgery. The Food and Drug Administration (FDA) approved LASIK after 5 years of testing. This may have been too short a test period. “The long term consequences of surgically manipulating the eyes are unknown. It simply hasn’t been around long enough to know how a person’s eyes will be 20 or 30 years down the road” (Keith et al, 2002).
“LASIK is the most popular eye surgery in America”, says Dr. Stephen G. Slade, an expert in refractive surgery and author of a popular new book ‘The Complete Book of Laser Eye Surgery’. “The procedure is very effective but it’s not as good as a surgery.”

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For medical tests performed in the recruitment and selection of pilots, it is of course desirable to include those tests that measure capabilities and limitations in the performance of key tasks, for example, early target detection. The overall purpose of such tests for pilots is to contribute to the safety of the aircraft, its crew and passengers if any. Among the key tests included in the physical biometrics for a Pilots License by an Approved Aviation Authority are tests of Visual Acuity, Color Differentiation and Glaucoma tests. It is however important to remember that the pass/ fail criteria for many of these tests have been established through a trial and error process over a period of time. Moreover an added complication is that experts do not agree on a formally established procedure for the testing and interpretation of results.
For example, measurements of visual acuity assess the performance of a very small percentage (5%) of the functioning area of the retina. This area, called the Fovea, contributes mainly to our ability for sharp daylight and color vision. The remaining 95% of the retina is only cursorily tested, yet it is the key to our peripheral ability and night vision, and ability to distinguish between objects.

A visual acuity of 20/20 is defined as what a normal observer with clear vision would be able to see and read out or distinguish at a distance of 20 feet. A visual acuity of 20/40 would be the same observer distinguishing between objects at a distance of 40 feet. In the context of pilot selection tests, visual acuity can further be divided into detection, recognition and resolution tests. Typical performance tests give more importance to resolution, yet detection may be more important for a pilot in the line of duty, especially in difficult circumstances.

For the Class 1 Medical Certificate, pilots are required to be able to distinguish between colors, as well as between different hues of the same color. This is called Color Discrimination Testing. However in actual circumstances on the job, the pilot will at best be faced with distinction between 2 or more colors, e.g Red and Green, rather than between hues of the same color, such as Light and Dark Red. Further for a Class 1 and Class 2 Medical Certificate, pilots are required to have bifoveal vision under conditions that are normally attributed to the successful performance of duties.

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Simply stated, this tests the depth perception of the vision of the pilot, as the candidate is required to look centrally from both eyes at the same time. Monocular vision, in which the candidate uses shading, familiarity of objects or landscapes and apparent size difference to interpret depth perception, only serves for a Class 3 Medical Certificate.
With such high standards for pilot and aviation licenses, it is no wonder that more and more aspiring candidates are turning to LASIK as a fast cure for vision defects. Today there are vast combinations of tests that can measure different visual attributes.
However the fact remains that for normal vision in performing day to day activities, we use the remaining 95% of the available retina. This is used to interpret and distinguish between a variety of objects entering into our field of vision from a vast spectrum of different directions and angles. Another screen test, Dynamic Visual Acuity or DVA, is our ability to focus on and distinguish between rapidly moving objects.

With the emergence of computerized testing ability, it is hoped that we will one day move towards defining ‘acceptable zones’ of visual acuity, rather than establishing rigid and foreboding cut-off standards. The present system will only serve to decrease and discourage the aspiring candidates.

Currently,” Automated Perimetry” is being recommended and tested in research protocols, involving vision-screening of automobile drivers, industrial workers and the visually impaired. It will inevitably be recommended for aviation screening.
It is well to note that LASIK and other surgical procedures have potential adverse effects that could deter/ prevent flying duties. Typical among them are:

a. Corneal scarring or opacities;
b. Worsening or variability of vision;
c. Night-glare; and
d. Haziness of vision.

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The aviation medical examiners expect that a pilot will not resume piloting aircraft until his or her own treating health care professional determines:

i) The post operative condition has stabilized;

ii) There have been no significant adverse effects or complications; and

iii) The person meets the appropriate Aviation Authority’s vision standards.
If these determinations are favorable and if otherwise qualified, the pilot may immediately resume duties.

For now, the final conclusion is that LASIK is not right for everybody. People with diabetes and glaucoma may experience longer healing times, and people who are severely nearsighted or farsighted may find that the surgery will not result in the same miraculous results.

However, future advancements may make the already safe procedure much safer. Newer lasers are making it possible to correct severely nearsighted and farsighted people who weren't eligible before, and efforts are being taken to customize the procedure for individual patients. In addition, a new intraocular lens implanted in the eye eliminates the need to cut the cornea, and can be reversed by removing the lenses.
As the medical profession gains more and more experience with the LASIK procedure, both its costs and risks may be reduced. We’ll just have to wait and see.