What GPs need to know when they refer patients to ophthalmologists …
DRY eye disease is a very common condition with potential to greatly impact quality of life for our patients. Being proactive about managing dry eye prior to cataract surgery can make a difference in terms of reducing patient discomfort, visual outcomes and, in my opinion, overall happiness.
You would therefore expect this condition to be taken seriously, especially by ophthalmologists. But it has only been over the past decade that dry eye disease has been properly recognised and respected as a major clinical problem by the wider ophthalmic community. There are many reasons for this previous lack of respect and increased interest in the topic.
First, and perhaps most importantly, was the generational thinking that dry eye was a minor irritation without major sequelae. Dry eye was put in the same category of importance as hayfever and dandruff, where over the counter symptomatic relief was perfectly acceptable. Our changes in lifestyle, with much more screen time, greater visual expectations and everyone generally living longer, have pushed along innovation to better understand dry eye and develop targeted, effective treatments.
Surgeons are implanting a greater number of presbyopia correcting intraocular lenses (IOLs) and this trend appears to be increasing. These types of IOLs allow a patient to see at multiple distances without a need for glasses. Personally, over 80% of my cataract surgeries involve implantation of a presbyopia correcting IOL. It is obvious why this technology is popular, but it may be less obvious why dry eye would impact the quality of vision with these IOLs more than a standard monofocal IOL.
Most presbyopia correcting IOLs diffract light to give multiple focal points, meaning that a near target for reading may only receive 25% of available light. Vision quality will be optimal if the cornea is smooth and allows passage of focused rays of light. Any scattering or reflection of light from a dry, irregular surface can further reduce focused light reaching the retina and degrade image quality to a greater extent than would occur with a monofocal implant where light is not split between targets. Dry eye is considered an extremely important factor in attaining accurate measurements to plan surgery and set patients up for success.
Unfortunately, we have become aware that dry eye is a complex condition not usually solely due to lack of tear production, inflammation or rapid tear evaporation alone. Often clinical signs are inconsistent with severity of symptoms. This sort of multifactorial disease creates a spectrum of patients with dry eye, from those with more prominent evaporative changes due to Meibomian gland dysfunction to autoimmune or inflammatory decreased tear production. This may seem overwhelming. Specialty dry eye clinics with modern methods of assessing the type of dry eye as well as offering interventions to treat the underlying cause exist and are wonderful for the more challenging cases.
When patients are referred to see me (and other ophthalmologists) to consider cataract surgery, I examine their eyes with a slit lamp microscope and take measurements of their eyes in order to calculate what type of IOL would best suit their eyes. The most important of these measurements is keratometry or corneal curvature. We do the same operation basically for each cataract surgery but the power of the IOL we implant varies depending on the length and shape of the eye. The final visual result is extremely dependent on attaining accurate measurements.
We measure the shape of the cornea by looking at reflections of light from the liquid and variable tear film. Any dryness, variability in oiliness or debris will impact the quality of measurements, can lead to inaccurate IOL calculation and ultimately a suboptimal visual result. If a patient arrives to see me and I cannot attain consistent keratometry measurements, I will manage their tear film and have the patient return for repeat measurements, usually two weeks later. This is quite a delay for some patients and so the advice to come should hopefully help in reducing the number of people requiring repeat tests.
Although I have said that there is a spectrum of overlapping dry eye causes, the majority involve Meibomian gland dysfunction and are labelled as being “evaporative” or “mixed”. Basically, this means that the lipid layer secreting meibomian glands are not functioning well, become obstructed and instead of their contents being a nice olive oil consistency, they become more buttery. This leads to a poor quality lipid layer of the tear film and ultimately the aqueous layer evaporating more rapidly than it would in a healthy ecosystem.
When GPs refer a patient for cataract surgery with symptoms of dry eye disease, both the patient and ophthalmologist colleague will appreciate if an attempt to optimise the ocular surface has been made.
Symptoms include feelings of grittiness, fluctuating vision quality, and watery eyes especially when in cold or windy environments. Due to a high likelihood of underlying factors, including Meibomian gland dysfunction, I personally would manage these patients with a combination of hot lid massages and lubricating eye drops using Systane® COMPLETE* lubricating eye drops, which have a lipid component. As the applied heat should be approximately 40°C to address inspissated meibum for patients with Meibomian gland dysfunction, it has been found that hot lid massages are best done with a compress, before the lower lid is firmly massaged upwards and the upper lid firmly downwards. This should be done daily.
Systane® COMPLETE* lubricating eye drops are my choice here, as they help to stabilise and support the quality of the lipid layer of the tear film while the hot compresses are working on Meibomian secretion quality. I ask patients to apply one drop four times daily until they are seen in clinic.
When patients are referred for cataract surgery but do not have concerning dry eye symptoms, I would still prefer to see the ocular surface optimised. For these patients I prefer to use Systane® HYDRATION* lubricating eye drops four times daily, as there is evidence that using lubricating eye drops in the weeks before surgery and again post-operatively leads to happy patients in my experience, with better visual results and less discomfort. That is exactly what I want for all of my patients with cataracts.
Dr Ben LaHood MBChB(Dist) PGDipOph(Dist) FRANZCO is a laser vision correction and refractive cataract surgeon.
*Systane range of lubricating eye drops are indicated for relief of dry eye symptoms
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