Physiology of the Lacrimal Gland System:

There are 2 sets of glands that produce tears to lubricate the eye:

1- Accessory Lacrimal Glands: are a set of small glands located in the upper eyelid and are responsible for continuously moisturizing the surface of the eye. A decrease of production of tears in these glands is the most common cause of Dryness in the eye.
2- Large Lacrimal Gland: This gland is mainly responsible for emergency flushing of the eye, for example, when we have a foreign body in the eye or when we cry. This gland is NOT responsible for continuous hydration of the surface of the eye

The tears usually moisturize the surface of the eye and then drain to the nose through the Nasal lacrimal duct and are swallowed afterward. That's why usually when we cry we sniffle and that's why many times we can taste the drops when we use them in the eye.
When tears do not adequately lubricate the eye, a person may experience:
-Pain in and around the eye
-Light sensitivity
-A gritty sensation

-A feeling of a foreign body or sand in the eye
-Itching
-Redness
-Blurring of vision
-Fluctuation of vision
-Eye fatigue following reading or use of computer.
-Runny eyes in windy conditions

Note that these symptoms may not always be there and may fluctuate with environmental changes. Symptoms are usually worse when exposed to dry and dusty air conditions similar to being on an airplane or when the weather is dry and cold and the indoors are heated. Even when you are driving and the heater or air condition is on, the dry air hitting your eyes can cause worsening of the dryness in the eye and cause your vision to become blurry, teary and/or irritated Sometimes, a person with a dry eye will have excess tears running down the cheeks, which may seem confusing. This happens when the eye isn't getting enough lubrication. The eye sends a distress signal through the nervous system for more lubrication. In response, the eye is flooded with tears from the back-up gland (called Lacrimal Gland) to try to compensate for the underlying dryness. However, these tears are mostly water and do not have the lubricating qualities or the rich composition of normal tears. They will wash debris away, but they will not coat the eye surface properly. In addition, because these emergency tears tend to arrive too late, the eye needs to regenerate and heal and treatment is necessary.

Dry  Eye Testing

Wavefront guided Laser Vision Correction technology was originally developed for use in high-powered telescopes to reduce distortions when viewing distant objects in space. Using this technology, Dr Jaoude can detect and measure the optical distortions unique to the entire optical system of your eye. Light travels in a procession of flat sheets known as wavefronts. Gentle wavefront lights enter the eye, pass through the entire optical system (cornea, lens and retina) and are then reflected back into the wavefront analyzer.

The wavefront analyzer compares the reflected wavefront with the original unaltered wavefronts. This produces a fingerprint of your vision. This information is then transferred to the excimer laser and is used as a guide to reshape the cornea during the laser vision treatment.

What is the Advantage of Wavefront LASIK or PRK?

In the past, laser vision correction patients have occasionally complained about their night vision. Of course, these symptoms can even be present in people without LASIK or PRK whose vision is corrected with glasses or contact lenses. However, in the wavefront guided LASIK clinical studies, more people were satisfied or very satisfied with their night vision after their wavefront guided LASIK or PRK as compared to their prior level of satisfaction using glasses or contact lenses