How to diagnose and manage contact lens discomfort

It’s all about perception
The perception of symptoms of contact lens discomfort is complex. One of the most common symptoms is dryness, which appears to diminish when the lenses are removed and also seems to change during the wearing period – with increased symptoms in the afternoon and evening. Other than dryness, ‘scratchy’ and ‘watery’ sensations, blurry vision and irritation are reported. More seldom, people experience light sensitivity and eye soreness.

So, never underestimate the importance of asking follow-up questions when a patient explains their symptoms. Try to expand on the presented symptoms and take a broader medical history. Understanding your patient’s symptoms will help you in diagnosing the epidemiology of their symptoms.

Use symptoms rather than signs
Published literature on contact lens discomfort contains many references to traditional clinical tests that may be helpful in the diagnosis of the condition. Some suggestions are the assessment of pre-lens tear film, meibomian glands, bulbar and limbal hyperemia, and corneal and conjunctival staining. Many studies indicate there’s a wide range of clinical signs that come with contact lens discomfort. Some of the more common signs are poor lens wetting, rapid pre-lens non-invasive tear breakup times (NITBUT) and preocular fluorescein breakup times. It’s important to note that the evidence regarding signs and the correlation with the condition is weak.

Therefore, when diagnosing contact lens discomfort, it’s better to use symptoms as an outcome measure, rather than signs, because the symptoms directly relate to the patient’s experience with their contact lenses. You can use a questionnaire to assess the frequency and intensity of the symptoms – this will also indicate further management and treatment, whether there are clinical findings or not. One of the questionnaires that the TFOS report mentions is the Contact Lens Dry Eye Questionnaire.

How do contact lens discomfort and dry eye disease interact and differ?
As symptoms of contact lens discomfort and dry eye disease are very similar, both conditions can intertwine. Patients who have traditional signs and symptoms of dry eye disease are more likely to have contact lens discomfort when they start wearing contact lenses. To the contrary, as the presence of dry eye disease increases with age, patients who haven’t been diagnosed yet with it at the time of being fitted with contact lenses, the suspected contact lens discomfort may instead be a manifestation of dry eye disease.

Also, a patient doesn’t need to have signs or symptoms of dry eye disease to suffer irritation when wearing contact lenses – and note relief when they remove them. On the other hand, practitioners often have patients with significant signs of dry eye disease, who’re able to wear contact lenses comfortably.

In short, patients with dry eye disease are more likely to have contact lens-related symptoms. As a practitioner, you have a difficult job in determining which factors have caused contact lens discomfort and concluding if the symptoms are either patient- or contact lens-related.

As one of the risk factors of dry eye disease is age, it’s wise to always pay extra attention to the quality of the tear film (with and without contact lenses on the eye), when fitting contact lenses on a presbyopic patient. Depending on the patient’s characteristics, you can determine the choice of lens material, wear time, as well as cleaning system and any suitable tear substitutes.

Future vision
To evaluate your patient’s signs and symptoms, you should combine the results from a questionnaire on symptoms with a thorough eye examination and anamnesis. The aim is to understand the reason behind your patient’s discomfort, to be able to support in wearing contact lenses comfortably – so to avoid drop-outs.

Material and design matter
Scientists and practitioners have questioned the influence of polymer chemistry, and various other material attributes that can be measured and quantified. The considered attributes are:

• The bulk, such as water content, dehydration, Ionicity, oxygen transmissibility, modulus and mechanical factors.
• The surface properties, such as friction, wettability, surface modification of contact lens materials.
• Contact lens material chemistry.

Up to now, almost none of these attributes – with the possible exception of friction – appears to be associated directly with contact lens discomfort. Contact lenses of different brands and manufacturers will vary in terms of their design. As a practitioner, you probably recognise that the design of contact lenses affects their ability to fit the ocular surface properly and that this influences the overall performance. For example, for soft contact lenses, moderate on-eye movement (with tear exchange) and corneal coverage are essential, but its overall association with contact lens discomfort is not entirely clear. There is even less consensus about the influence of various design attributes on the condition. However, friction, size, shape, and contour of lens edges appear to be some of the most influential determinants of contact lens comfort for soft contact lenses.

Better care, better comfort
Contact lens care solutions, practices, and wear schedules are interesting when we look at understanding their role(s) in contact lens discomfort. Peer-reviewed literature doesn’t show specific formulations or components that may be associated with either increasing the discomfort or improving comfort. That said, we can probably all agree that regular contact lens care – including rub, rinse, and adequate soaking – is essential in wearing contact lenses comfortably. Also, replacing soft contact lenses regularly is best for ocular health, and could potentially improve comfort.

What about patient- and environment-related factors?
Apart from contact lens material, design, and care, the classification scheme in figure 1 also shows that there are several patient- and environment-related factors that can cause contact lens discomfort.

It shouldn’t be a surprise that the eye can detect and sometimes react to the presence of a contact lens – as the contact lens touches sensitive parts, like the cornea, lid margin and, to a lesser extent, the conjunctiva. Evidence from the literature shows some occasional patient-related factors associated with the condition, such as female sex, younger age, inadequate tear film quantity and quality, seasonal allergies, and the use of systemic medications. On the other hand, there is little evidence that ethnicity, blink rate and blinking patterns, systemic disease, diet, alcohol, smoking, cosmetic use, or psychological factors play a role in contact lens discomfort.

The TFOS report also indicates that literature supports that symptoms of contact lens discomfort can occur due to an increased tear evaporation rate from the lens surface, because of a reduction in the relative humidity. In addition to this, the movement of air (wind) and visual activities that make people blink less (such as the use of digital devices) may worsen signs and symptoms of the condition. For the role of other environmental factors on contact lens discomfort, such as temperature, altitude, smoky environments, air conditioning or indoor heating, there’s little concrete evidence.

Future vision
Surprisingly enough, there are not so many proven links between contact lens discomfort and factors like contact lens material, design and care system. The TFOS report concludes that much work should be done yet to unravel the complexities of the condition. That said, as eye care professionals, we can agree that if a patient can’t wear their contact lenses comfortably, it may help to make changes to the lens material, design, care system and replacement schedule.

Contact lenses and the cornea
The cornea serves as the major surface on which the lens sits and could play a significant role in contact lens discomfort, particularly as it relates to its neurobiology. Even though many publications examine corneal staining associated with contact lens wear, there’s only a weak link between contact lens discomfort and corneal staining – and it’s not a significant factor for more contact lens wearers.

Contact lenses and conjunctiva
The conjunctiva proved to be more closely linked to the development of contact lens discomfort. In some studies, bulbar conjunctival staining was found to be associated with it. The palpebral conjunctiva has a vital role in controlling the interaction with the ocular surface and lens. Two specific issues potentially linked to contact lens discomfort include alterations to the meibomian glands and to the leading edge of the palpebral conjunctiva, as it moves across the lens surface (the so-called “lid-wiper” zone). Contact lens wear does appear to impact the function of the meibomian glands, and reduced meibomian gland function has been associated with contact lens wear. Alterations to the lid-wiper area are more common in contact lens wearers with symptoms of contact lens discomfort, and some studies have related these tissue changes to the condition.

The TFOS report concludes that there is some evidence to suggest a link between conjunctival and lid changes with contact lens discomfort. The most substantial evidence is related to the meibomian gland and alterations to the lid-wiper area.

Contact lenses and tear film
The presence of a contact lens on the eye divides the tear film into a pre- and post-lens tear film, creating new interfaces with the ocular environment. Changes in the tear film occur after the lens is applied and during the contact lens wear. Additionally, biochemical differences are likely to exist between the pre- and post-lens tear film layers. Partitioning of the tear film after applying a contact lens and during wear causes some compositional changes that result in a less stable tear film on the front surface of the lens and less well-defined changes to the post-lens tear film layer. The resulting pre-lens tear film has reduced lipid layer thickness, reduced tear volume, and increased evaporation rate compared to the “normal” tear film.

Evidence specifically suggests that decreased tear film stability, increased tear evaporation, reduced tear film turnover, and tear ferning are associated with contact lens discomfort. And, tear film stability is recognised as a critical factor in the condition as well.

Future vision
When you investigate the source of contact lens discomfort, you should undertake a full examination of the anterior ocular structures that can be impacted by the contact lens. The TFOS report suggests particular attention to the importance of carefully assessing the meibomian glands and lid margins.