Dry Eye and Tear Dysfunction

4/24/14

With an aging population and increasing awareness of the condition, dry eye has become one of the hottest topics in eye care today. There have been numerous advances in our understanding of the condition as well as several breakthroughs in treatment.
eye drops in eye
Lets start with the most fundamental question. Why do we have tears? Tears serve many functions, but perhaps the most important is that they create a perfectly smooth optical surface at the front of the eye to allow sharp focusing. The sharper your vision the more quickly you can spot and run from a predator or find a supply of food. Hence, a stable tear film is critical for survival. As a result, the body has evolved many ways to help keep the tears healthy and intact.

When I describe the tears to a patient I describe it as a structure. Tears have a foundation that anchors them to the eye’s surface, an elastic protective support section not that different than the walls in a building and even a roof, just like a house has. Like a house, problems with any structural part can adversely impact the entire building.

Over the past few years the most important breakthroughs in understanding dry eye have focused on the outer portion of the tear structure – what you might think of as the roof. When a roof develops holes and it rains, water gets in which can destroy the entire structure of the house. With the tears, holes in the “roof” can let moisture evaporate causing the structure to collapse and become unstable.

The outer layer of the tears consist of lipid or oil produced by the meibomian glands – glands that run radially through the lids and express small amounts of complex oil with each blink. When these glands work properly, the oils they produce coat the tears, preventing evaporation and stabilizing and lubricating. When the glands become blocked – which can occur for a number of reasons including decreased blinking due to excessive computer use, the lack of oil can lead to a down spiral of damage to the eye’s surface with symptoms that can range from annoying to life altering.

Lets talk for a moment about symptoms. We know that dry eye is progressive and, if left untreated will worsen over time, so the sooner we know about it, the sooner treatment can begin. I am often surprised that even with increased awareness, most patients don’t recognize that they suffer from dry eye until the condition is fairly advanced. One reason is that many people think that the symptoms of dry eye are a normal and expected part of aging. For the most part they are not. If you experience, burning, irritation, unstable vision, grittiness or any change in your vision or eye comfort, you should bring this to the attention of your eye care practitioner.

One of the most common signs of dry eye is excessive tearing. Patients often complain that their eyes are too wet and I have to explain that the excessive tearing is the eye’s way of trying to correct for dryness and prevent further damage. Unfortunately excessive tearing further destabilizes the tears and makes matters worse.

Lipiview System
Lipiview System

Perhaps the greatest advance today is the recognition that meibomian gland dysfunction causes or contributes to nearly 90% of all dry eye. Many eye care providers are adding high tech tools like meibography which can show the actual state of the meibomian glands like an X-Ray and LipiView which measure the actual thickness of the lipid layer of the tears. As a result diagnostic ability has improved.

Lipiflow Device
Lipiflow Device

Recently introduced eyedrops like Alcon’s Systane Balance and Allergan’s Refresh Optive Advanced Formula drops can help restore absent or deficient oils in the tears. And new treatments including moist heat goggles like Tranquileyes by EyeEco can help improve comfort. LipiFlow, a technology pioneered by TearScience, offers a breakthrough treatment that can clear blocked and reset meibomian glands. It can produce amazing improvement.

There have also been significant advances for contact lens wearers suffering from dry eye. Scleral lenses are especially helpful for patients with advanced dry eye who also must wear contact lenses to see, such as those who have keratoconus. The large scleral lens serves as a barrier that protects the eye and provides sharp stable vision. In fact, scleral lens designs are used as a treatment for severe dry eye and ocular surface disease.

Finally, if you have been diagnosed with dry eye previously and are still suffering despite treatment, this may be a good time to return to your eye care provider to discuss your condition and explore the possibility of new treatment options.

AArthur B. Epstein, OD, FAAO
co-founder of Phoenix Eye Care
and the Dry Eye Center of Arizona
Fellow of the American Academy of Optometry
American Board of Certification in Medical Optometry
Chief Medical Editor of Optometric Physician™

End of the Day Syndrome

4/2/14

“Dr. S., my eyes are red and burning at the end of my work day.”

“Patient, what sort of work do you do?  Tell me something about your work conditions.”

“I am a computer graphics artist.  I sit and stare at my twenty-seven inch HD screen for hours on end gently adjusting the composition of each pixel.  My studio is air-conditioned but not humidified, so after some hours of work, I feel dry as a bone.”

“One more question…can you cry tears?  Say, when you peel and slice an onion?”

Rule of 20 - blinking

The need to blink

Blinking is a complex function of the eyelids that when completed results in a clean, refreshed, re-wetted corneal surface.  The tears that are washed across the outside of the eye with each blink bring oxygen and other nutrients to the outer cell layer aiding in the rebuilding and revitalizing of the surface tissue.

Blinking is characterized by a full sweep of the upper lid over the eye to meet the lower lid.  The completion of this motion is performed gently without squeezing.  And, to be effective full eye closure needs to be repeated fairly often.  Blink rates vary according to investigators but most sources report an average of between six and ten full blinks per minute under normal viewing circumstances.

The anti-blink problem of our generation

In olden times – say the years between 1750-1950 – the most aggravating problem to the ocular surface was a good book or intense study.  The reader would concern himself with the text at hand and slowly his eyes would dry until a “rest break” was necessary.

Environmental or vocational changes to our lifestyle over the generations have promoted reduced blink rates.  Most recently in this negatively developmental progression is the effect of the television screen, the CRT, the LED screen, the handheld and pocket computer on the blink rate.  It appears that as attention level increases, blinking suffers.  First the eyes close less, then incompletely, and finally rarely only when surface dryness drives the individual to desperate measures.  He must blink or (so he feels) his eyes will pop out of their sockets.

Adding insult to injury increasingly over the decades is air conditioning – both heating and cooling – when not humidified.  Staring at console screens in dry environs speeds the desiccation of the cornea and results in discomfort.

The surface of the eye is a biological system.  Living systems require some degree of moisture.  If the cells of the eye – or any biological surface — are permitted to dry out, they will die.  Dead corneal cells fall off the cornea and float in the tears on the surface of the eye until washed away with a blink.  Until the surface is cleaned the dead cells are considered by the eye to be foreign bodies with the consequent irritation and induced reflex to blink.

When cells die and fall off, the underlying nerve endings send pain signals to the nervous system.  The sensation can be felt as pain, burning, or mere irritation or itching depending upon the severity of cell loss.

How to handle environmentally induced dry eye

After the ocular surface is dry most treatments will seem to make matters worse:  to cause burning and stinging, perhaps, even more than the dry eye itself.  Any tear substitute, any amount of blinking will be irritating at first. But, that is really all that can be done at this stage:  wetting and blinking.

Prevention

As in many conditions, the best treatment, in fact a cure, for recurrent environmentally induced dry eye is prevention.  For the eye that has a naturally flowing tear supply, the act of blinking is the surest prevention to stinging and burning after a day’s work at the computer.  Additionally, many sources recommend using the ‘rule of 20’:  after each twenty minutes of work, look up from the text or away from the screen; blink and refocus on the page twenty times.  This repetitive exercise simultaneously re-wets the eye and relaxes the focusing mechanism of the eye.

The result is relaxed and comfortable eyes that can continue to provide important and high quality information for longer hours of work.

Bezalel-SchendowichBezalel Schendowich, OD
Chairperson and Education Coordinator, JOS
Fellow, IACLE
Member, Medical Advisory Board NKCF
Sha’are Zedek Medical Center, Jerusalem, ISRAEL