THE TEAR FILM WAS TRADITIONALLY viewed as 3 independently functioning layers. We have now come to understand that the interactions among the mucin, aqueous, and lipid layers of the tear film are far more integral than previously thought. The mucin layer helps the overlying aqueous layer to spread evenly over the surface of the eye, and the aqueous layer contains the bolus of nutrients and volume of the tear film, all held in place with the lipid layer. The lipid layer, or what I refer to as the anti-evaporative layer, is produced by the meibomian glands, which are located on the posterior lid margin. It is critically important that these 3 layers interact appropriately to provide both comfort and visual acuity.
Dynamics of the Tear Film
As with and in addition to presbyopia, changes to the tear film occur naturally with aging. The prevalence of meibomian gland dysfunction increases over time, and presbyopes are certainly not immune. When patients reach 40 to 50 years of age, reductions in the quality and amount of meibomian gland secretions can be observed. Due to an insufficient lipid layer, the aqueous layer tends to evaporate more prematurely than it typically would.
When examining and treating presbyopes, eyecare practitioners (ECPs) must be hypercognizant that their patients’ tear film is already at greater risk of being frail. Beyond age-related changes, environmental conditions are a key consideration. Lifestyle factors, such as relative humidity and exposure to digital devices, may greatly impact eyelid and ocular wellness.
Viewing digital screens for extended periods of time is a common, challenging stimulus that further contributes to the inadequacies and insufficiencies in a patient’s tear film. The increased exposure to artificially constructed environments has been shown to affect both blink rate and total blink reflex, posing a challenge even to patients with normal tear films. ECPs should also think about ocular cosmetic use when working with presbyopes. It is critically important that ECPs counsel presbyopes regarding proper cleaning and product removal before sleep, given some ingredients’ associations with meibomian gland toxicity.1
Concentrating on Multifocal Contact Lenses
Perhaps as a result of examining healthy tear films or ocular surfaces, particularly in younger patients, ECPs may take for granted the intricacies and potential challenges associated with contact lens wear in presbyopes. A concept that is insufficiently discussed among ECPs is the thickness of contact lenses relative to the tear film. Although a contact lens sits within the tear film, disruption still occurs. As clinicians, we must continue to be mindful of material properties, particularly those that will promote a homeostatic state on the ocular surface.
To that end, replacement frequency has become an increasingly critical component for multifocal contact lens wear in presbyopes. Daily disposable contact lenses typically excel because their regular replacement helps to provide a more easily maintained hygienic experience for patients. As clinicians, we can expect a lower risk of adverse events associated with discomfort without the cleaning that is otherwise required with the biweekly or monthly modality. Owing to the increasing availability of contact lenses and parameters, ECPs have the ability to fit more presbyopes in daily disposable lenses.
Highlighting the Ideal Characteristics
The overall strategy for optimizing the multifocal lens wearing experience is twofold: comfort and vision are both crucial and interrelated components. With regard to comfort, first and foremost, ideal contact lens material characteristics incorporate a low modulus while still retaining high levels of moisture. Additionally, it is optimal that contact lens materials contain micronutrients within the matrix of the lens to create homeostasis between the lens and the tear film. If the contact lens fails to maintain moisture and a homeostatic state on the surface of the eye throughout the day, there is a greater risk of poor optics. Understanding that dryness can be a disruptor of visual acuity, it is incumbent upon ECPs to really understand the material characteristics when placing contact lenses on a patient’s eyes.
Considering how multifocal lens design can provide the greatest chance of success with patients is also optimal. ECPs should use advanced designs that offer our patients that multidistance functionality to help them see both far away and up close. Crucially, the optics should address the intermediate range. Though clinicians may concentrate on a multifocal contact lens function at near and distance vision, many of our presbyopes’ daily activities take place in the intermediate range.
The Link to Comfort
It is remarkable how much modern presbyopes value functionality within their multifocal contact lenses. Fortunately, there are a number of recent additions to our armamentarium to treat and help these patients. An important advancement has been the wettability in the homeostatic state, which modern multifocal lenses can provide to the ocular surface. Osmoprotectants, electrolytes, and/or moisturizers that are infused within the matrix of some contact lenses also help to make the initial placement on the eye feel more natural.
Innovations like ProBalance Technology (Bausch + Lomb), which feature these molecules, also allow for a homeostatic state throughout the day. Multifocal contact lens technologies that can optimize both the patient’s initial impressions and the duration of comfort are successful because patients are most functional. End-of–day comfort, in turn, optimizes the visual performance featured in the optical designs of multifocal contact lenses. As companies offer advancements in the way that multifocal contact lenses interact with the ocular surface, our patients and practices benefit from the additional options available to them.
A Change in Approach
I encourage other ECPs to think differently about how they prepare for visits from presbyopes who wear spectacles. Rather than solely preparing to update a patient’s eyeglasses, we as clinicians should ensure that we are constantly providing all vision correction options to patients, no matter what stage of presbyopia. Even if contact lens wearers are seemingly content, they may not necessarily have the best multifocal contact lens technology for their eyes. I suspect that some patients refrain from honestly evaluating their contact lens wearing experience at the risk of their ECP advising them to discontinue contact lenses.
From a clinical perspective, ECPs need to always share the latest options with our patients so that we, with the patient, can determine the best strategy for that individual moving forward. Although some patients may not necessarily want the newest technology, without proactive communication they may not have the opportunity to even contemplate the change. When we educate our patients, we can formulate strategies that are best for them to incorporate contemporary technologies for their ocular surface health and overall visual satisfaction. ■
- Wang J, Liu Y, Kam WR, Li Y, Sullivan DA. Toxicity of the cosmetic preservatives parabens, phenoxyethanol and chlorphenesin on human meibomian gland epithelial cells. Exp Eye Res. 2020;196:108057.