Page 31 - Retail Pharmacy Assistants September 2020

EYE CARE 29
IT’S TIME FOR A TEARY GOOD BUY
By Peter Howard.
For hundreds of years, scientists have mused over the mysteries of the human body. Along the way we’ve discovered DNA, unravelled the secrets of the genome, and used stem cells to grow real human ears that were later successfully transplanted.
Despite these astonishing advances, many mysteries remain. We’re puzzled by the appendix, have no idea what determines left- or right-handedness and, despite years of research, we still don’t understand why humans cry. Charles Darwin once declared emotional tears to be ‘purposeless’. Today, 160 years later, emotional crying remains one of the unsolved mysteries.
While the science behind emotional crying continues to elude us, we understand the complexities of tears, and have identified three distinct tear types produced by the human eye.
Emotional tears are known by ophthalmologists as psychic tears, which when released appear rapidly in significant quantities from both eyes. Next are the reflex tears, produced in response to irritants such as sand, chilli and fumes from
an onion, intended to protect the cornea by flushing foreign contaminants before they cause damage to its delicate surface. Unlike psychic tears, reflex tears are produced by individual eyes as they are irritated.
At the low end of the volume scale, but perhaps the most important of all, are basal tears. These tears are released by both eyes in a tiny, continuous flow intended to keep the cornea lubricated while also fighting against bacterial infection as a part of the body’s immune system.
When basal tears are produced as intended, we’re blissfully unaware of our eyes and suffer no eye discomfort. Unfortunately, multiple factors can interfere with the eye’s tear function, leading to a range of conditions including keratoconjunctivitis sicca, more commonly known as dry eye disease (DED).
Patients suffering with DED complain of a wide range of symptoms from mild discomfort to significant pain and, if left untreated, severe DED can progress to inflammation of the eye, abrasion of the cornea, corneal ulceration, and long-term vision problems.
Oil on troubled water
To understand more about DED, Retail Pharmacy Assistants spoke to ophthalmic specialists and explored the treatment options community pharmacies can offer.
Optometrist and Alcon ANZ Professional Affairs Associate Megan Zabell specialises in the education and training
of optometrists, dispensers, pharmacists and pharmacy assistants, on a range of eye conditions and treatments. She says the main causes for DED are tear quantity, tear quality, or a combination of the two.
“Sometimes the eyes aren’t producing enough tears, and this can be related to age and some inflammatory conditions,” she said.
“Other times the eyes produce poor-quality tears, so they evaporate off the eye’s surface too quickly, a condition most commonly linked to poor function of the oil glands. Dry eye can also be caused by a combination of the two,” she said.
To discuss DED treatment options with patients, we must understand the workings of the tear film – something Ms Zabell says is far more complicated than people know.
“On the very top of the tear film, there’s a very thin layer of oils called the lipid layer that stops the tears from evaporating too quickly,” she said. “Most of the oils in this layer are secreted by tiny oil glands called Meibomian glands located in our top and bottom eyelids.
“The bulk of the tears is made up of the mucoaqueous layer, a gel-like layer providing nourishment for the front of the eye, while also contributing to clear, precise vision. Dissolved in that mucoaqueous layer are mucins that help stick the tears to the eye.
“However, the oily layer can be deficient, often because the meibomian glands are blocked or not producing good quality oils, resulting in evaporative dry eye.
“The watery layer can also be deficient, causing aqueous deficient dry eye. People suffering from dry eye that has characteristics of both evaporative and aqueous deficiency are said to have mixed dry eye.”
Ebb and flow
Vision Eye Institute Ophthalmologist and University of Canberra Associate Professor Colin Chan says it’s important to learn a patient’s history to determine if a patient is presenting with DED or some other more acute eye problem.
“Dry eye disease is typically a more chronic problem,” he said. “It will be exacerbated by certain activities, like working at a computer or anything which reduces blinking because that increases evaporation from the eyes.
“Things like air conditioning, central heating, or even the wind outside can trigger DED and patients will usually talk about something relatively chronic and affecting them most of the time.
“Knowing there are different kinds of symptoms is important because watery eyes and dry eyes can both be symptoms of DED. One of the most common symptoms of dry eye is the patient complaining of reflex watering when they are out in the wind or saying their eyes suddenly start watering when they are working at a computer.
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RETAIL PHARMACY ASSISTANTS • SEP 2020