Dr. Cheung’s Blog 4/1/2017

Dr. Cheung’s Blog 4/1/2017

April 1, 2017

Aloha Magic

My family and I went on a winter vacation to Kauai last month.  I can’t remember when was the last time that we went on a week-long vacation together.  It was so relaxing; sleeping in, soaking up some sun, and most of all, spending unhurried time with the kids.  The twins are deathly afraid of water and they have never submerged themselves in any pool past their necks.  Even the ordinary hair washing at bath time is still a struggle.  Maybe it was the Aloha magic but it was good to see them work up the courage and plunge their little heads into the water.  My son Theo was the first to do that and I just loved seeing his face beam with a sense of achievement when he popped out of the water.

My wife went with some friends to hike the famous Kalalau Trail along the Na Pali coast in the northern part of Kauai.  For that 48 hours, I watched six kids ranging from fourteen to three and a half.  Luckily, the pool, the beach and the sun kept them pretty happy and tired.  The seven of us did go on a road trip to the Kilauea Point Wildlife Refuge and Lighthouse.  It was the best deal in Kauai – five bucks for all seven of us to get in as 15 and under go free!!  We also visited the breathtakingly beautiful Hanalei Bay.  We were body surfing in paradise.

The highlight on this trip for me was sea kayaking and whale watching on the Southern coast of Kauai.  I kayak at least a few times each year but always in calm water.  Sea kayaking in the open Pacific Ocean is a whole different experience.  Members of our tour group all rode in these sit-on-top tandem ocean kayaks with holes in the bottoms.  (Yes, holes in the hull for splashed over water to drain out).  I felt very exposed and elevated compared to the regular sit-in kayak that I am accustomed to.  The sea was rough and we were mercilessly pummeled up and down by the strong winds and large swells.  I felt like I was riding a roller coaster in Disneyland.  Pretty soon though, the feeling of being small and scared drifting in this vast ocean dissipated.  My partner and I learned to be nimble and paddled with the waves.  Our little kayaks speedily glided through the choppy sea to within hundred feet of a humpback whale when it sprayed from its blow hole.  It was a glorious sight and all worth it.

With the strong winds blowing at me, my eyes got a bit dry and my contact lenses were less than comfortable.  I started to wonder if marine animals can get dry eye too.  One would think they wouldn’t since their eyes are constantly bathe in water.  What I learn is that cetaceans like whales and dolphins actually produce a thick layer of tears, almost in the consistency of a gel, to protect their corneas from the salt in the water.  Abnormalities of their tear glands can affect this tear gel, exposing the corneas to surface breakdown and infections in a manner similar to human with dry eye.  Dolphins in captivity who are exposed to high concentration of chlorine in the water are also know to produce mucus discharge and put them at risk for dry eye and corneal infections.

Dry eye is one of the most common ocular conditions that I see in the office.  Studies showed that the prevalence of dry eye can be as high as 34% in some populations.  Dry eye affects women more commonly then men and the incidence also increases sharply with age.  The tear film actually has the greatest optical power than any ocular surface such that irregularities in this layer can potentially degrade the retinal image by up to 80%.  The visual consequences of dry eye are far-ranging and can affect numerous aspects of daily living.

The human tear film is far more complex than salt water.  It has three main components: water, lipids and mucin along with a host of other substances such as electrolytes, antibodies, growth factors and anti-inflammatory molecules.  The water component is produced largely by the lacrimal gland located in the lateral aspect of the eye socket.  The lipid component serves to restrict tear film evaporation and is produced by the meibomian glands located along the margin of the eyelids.  The mucins control the thickness and stability of the tear film and are manufactured by specialized cells called the goblet cells on the surface coating of the eye (conjunctiva).  Even a subtle imbalance of any of these three components can potentially cause dry eye.  And as such, the diagnosis of dry eyes can be challenging and there is no single test that can be used to establish the diagnosis.

Tear film osmolarity is one of the newer modalities that may help to identify early dry eye disease.  It is often increased in dry eye patients because of decreased aqueous tear  production or increased evaporation as a result of a poor lipid layer.  An osmolarity reading greater than 308mOsms/L is generally considered diagnostic for dry eyes.  Interestingly, the tear osmolarity of bottlenose dolphin, at 470mOsms/L, is a lot higher than ours or other terrestrial mammals, presumably an adaption to their salt water environment.

Ocular surface inflammation appears to play an important role in the worsening of chronic dry eyes.  While topical steroids can be used in some acute situations with dry eyes, they are not good options for long-term therapy because of the associated side effects of cataracts and glaucoma.  Restasis (cyclosporine) is another anti-inflammatory drop that has been very helpful in the management of dry eyes.   Cyclosporine works by blocking the release of proinflammatory molecules from activated T-cells in the conjunctiva.  Most recently, Xiidra (Lifitegrast) appears as a promising anti-inflammatory drug by inhibiting the binding of two molecules (intercellular adhesion molecule-1 and lymphocyte function-associated antigen-1) that are responsible for T-cell activation and recruitment.

We are committed to be a center of excellence for dry eye management and we are pleased to be able to offer our patients the latest diagnostic and treatment modalities for dry eye disease.  If you are experiencing symptoms of dry eye and they are interfering with your quality of life, please do not hesitate to give us a call.