CONTACT LENS INTOLERANCE
Managing Contact Lens Intolerance
Patients may become intolerant to contact lens wear for a variety of reasons.
By Bezalel Schendowich, OD, FIACLE, & Scott McGregor, OD
Dr. Schendowich is a member of the Medical Advisory Board of the National Keratoconus Foundation, a Fellow of the International Association of Contact Lens Educators, and an adjunct assistant clinical professor of optometry at SUNY-Optometry in the ophthalmology clinic at the Sha'are Zedek Medical Center in Jerusalem, Israel.
Dr. McGregor has been in private practice since 1986. He specializes in specialty contact lenses and difficult fits. He is a member of the Medical Advisory Board of The National Keratoconus Foundation and is the educational director for the Ophthalmic Technician Programs at Collin College and Brookhaven.
Contact Lens Intolerance (CLI) is a catch-all description of a condition — a diagnosis of inclusion consisting of a vast array of causes from the physical, both anatomical and physiological, to the psychological. CLI may be total, occasional, periodic, or seasonal. It might result from a pre-existing condition or be acquired through contact lens abuse. Anything that can negatively affect a patient's relationship to his contact lenses can result in lens intolerance.
CLI sufferers typically cannot apply a lens to their eye without pain, injection, and lachrymosis. They may once have worn their contact lenses for all of their waking hours but now hesitate to use them even for the occasional social event. Additionally, any anatomical or physiological abnormality that can make contact lens use difficult can eventually cause CLI.
Anatomical and Pathological Considerations
Any change from a normal, healthy "good contact lens" eye anatomy is likely to enhance the CLI phenomenon. To wear contact lenses comfortably for long working days, all structures and functions of the external eye must be intact.
Eyelids Considering each surface of the eyelids, we can see that the success of contact lens usage in many respects depends upon the health and integrity of the entire system. The lid margins need to be full and smooth with no signs of inflammation or infection — no dandruff or meibomian gland dropout; no signs of meibomian gland dysfunction or lid wiper epitheliopathy. The palpebral conjunctiva should be smooth and pink: follicles, giant papillary conjunctivitis (GPC), and concretions can all reduce comfort, increase sensation and cause a patient to cross the line into lens intolerance. The musculature of the lids must allow for complete and gentle (not tense) closure upon blinking. During sleep the lids must close naturally to prevent nocturnal ocular surface desiccation.
Lid retraction, dermatochalasis, and lagophthalmos will also negatively affect comfortable lens use. These conditions will cause incomplete blinking and a greater tendency for firm lenses to be dislocated or even tipped off the eye.
Cornea Corneal problems contribute in no small way to CLI. Surface disease conditions such as dry eye syndrome (primary and secondary) and mild to complicated imperfections in epithelial integrity and corneal smoothness may cause reduced lens comfort.
Epithelial basement membrane dystrophy with concomitant recurrent corneal erosions will increase corneal sensitivity to painful levels if not treated. Proud nebulae at the tips of keratoconus apices will repeatedly erode, causing pain that persists after contact lens removal. Exposure- and dryness-related pterygia and pingueculae may not cause pain with contact lens use, but they are likely to become inflamed and unattractive.
Corneal nerves lose their myelination after 1mm inside the limbus. Thus, the central cornea has "unprotected nerve endings," which contribute to increased corneal sensitivity in all contact lens fits. It is for this reason that lenses with larger diameters (semi-sclerals and full sclerals) have such reported success as they do — they rest on the para-limbal region where nerves are many times less sensitive.
Though many CLI patients anticipate achieving the peace and serenity of perfect vision through refractive surgery, many end up with residual or recurrent refractive error that causes them to once again need glasses or contact lenses; but, because of the surface imperfections or chronic dryness resulting from the treatment, contact lenses are rarely tolerable.
Intacs (Addition Technology) trigger their own problems for patients who exhibit residual refractive error with the rings in place. They may be superficially placed, the ends might not be sufficiently buried in the cornea to prevent recurrent erosions, or wound gap at the insertion point exacerbated by the rubbing of the lenses (soft or GP) can result in irritation or even infection. Even a perfect Intacs fitting will result in sensitive corneal tissue being pressed between the Intacs ring and the plastic of the contact lens, which can lead to CLI.
Contact Lens Issues
In a patient who demonstrates a predilection for CLI, just about any factor in the contact lens equation can serve as a sufficient irritant that results in intolerance. Aspects of the lens-to-cornea fitting relationship, including the overall diameter, the various back surface curves and widths, lens thickness, edge configuration, and the movement of the lens over the ocular surface, can elevate sensation to intolerable levels. Material considerations of smoothness, wettability, "finish," and Dk all affect the tolerance quotient.
In some cases, a well-made lens both in design and manufacture becomes uncomfortable because of solution incompatibility either with the lens itself or with the patient.
Wearing time is a two-way street. Until now the considerations we have mentioned have been with regard to daily wear of contact lenses during waking hours, where our goal is maximum comfortable wearing time. Conversely, in overnight orthokeratology treatment, in which the lenses are worn during sleep, we have found that eight hours of wearing correctly designed ortho-k lenses delivers the desired result of an entire day of lens-free clear vision. But, we have seen cases in which overwear while sleeping has caused a form of eminently treatable CLI. One patient, for example, after several years of successful ortho-k treatment, presented with red, tired eyes and corneas covered from limbus to limbus with scattered punctate keratopathy. Her history: she was sleeping long nights and over-treating her corneas. She was seriously concerned that she had developed intolerance to her ortho-k lenses. We treated her successfully by reducing her wearing time to a strict eight hours and moving her to a milder contact lens solution system.
Patients who return after a long hiatus since their previous check-up may complain vociferously about their contact lenses. While the problem may well reside with the health of their eyes, you must analyze the condition of the lenses as well. Aside from changes in lens specifications, surfaces and lens edges must be examined for scratches, chips, cracks, and debris buildup.
Another aspect of CLI is visual compromise: poor visual acuity or poor quality vision when the measured acuity reaches high Snellen levels. A patient who has early keratoconus may consider himself suddenly intolerant to his lenses when in reality his dystrophy has progressed, obsolescing his lenses.
In cases of irregular corneas (ectasia, post-surgical, Reis-Buckler's), contact lenses serve to replace a distorted refracting surface with a smoothly polished, regular one. Theoretically, by perfecting the refraction, vision would be improved. We find in some cases of advanced keratoconus, for instance, that there are several areas of corneal thinning, and each has its own refraction and point of best focus on the retina. While a contact lens will be fit in reference to a sort of average of many of these points of focus, other areas requiring different corrections will result in monocular multiplopia, shadows, haloes, and other visual phenomena.
To many patients, this sort of vision is far below the standard expected from contact lenses. The vision that was bleary is now multiple or clear but shadowy — in any event, a source of CLI complaints.
Another source of intolerable vision problems generated by contact lenses is the blur encountered by keratoconic patients who have been refit into steeper lenses as their cones progress (or who have been refit from flat-fitting tri-curve lenses into a more modern keratoconus design, allowing for minimal apical as well as edge clearance). Over time, such patients have become accustomed to the temporary orthokeratology-type effect they experienced after removing their old contact lenses. They found that they could function inside their homes and read comfortably for some evening hours. When refit to a more "forgiving" keratoconus design that does not flatten their corneal apices, they become aggrieved because they have apparently lost this unadvertised benefit of their old lenses. One such patient threatened to jump off a roof if we did not return him to his previous status quo.
Often CLI results when we expected the opposite. You may refit a patient in a hybrid contact lens to increase comfort (especially to resolve the discomfort of the lid moving over the lens edge), yet the low Dk of the soft skirt combined with debris depositing on the skirt may result in dry, irritated eyes and CLI.
Physical aspects of ocular health and anatomy as well as the design and condition of the contact lenses themselves are quantifiable and amenable to treatment and redesign. But, subjective components of contact lens wear can be just as deleterious to successful and comfortable lens use.
A patient who cannot easily apply and remove his contact lenses will often quickly complain that the lenses are irritating his eyes. Patients who are not compliant with their lens care regimen or scheduled wearing time will also likely suffer an eventual breakdown in lens tolerance. Some patients are uncomfortable manipulating their eyelids — they may complain of intolerance rather than learn more forgiving techniques.
Another realm of cognitive CLI is willfulness. Such patients have an agenda. Nothing works. Objectively, the cornea and lens-to-cornea relationship are excellent. Vision is good and predominantly without shadows. Wearing time can extend throughout the working day. But, such patients are still uncomfortable. Again, nothing works, including refitting to other designs or materials, piggyback lens systems, blink modification, warm lid massages, or rewetting with artificial tears.
Managing Physical Causes of CLI
Until now our discussion of CLI has revolved around possible underlying causes for our patients' difficulties in tolerating lens wear. We have seen that those problems can be grouped into several categories (Table 1):
- Pre-existing conditions
- Contact lens problems
- Cognitive issues
We have also mentioned that you can prevent CLI by diagnosing and treating the pre-existing conditions and weighing the value of dissuasion in place of engendering another case of CLI.
Pre-Fitting Examination As in every patient encounter, the first step toward either preventing or treating CLI is a careful case history and a full ocular health examination. During the history phase of the examination, it is important to elicit information about dryness; burning of the eyes, especially in the early mornings and late evenings; itchiness of the eyes; dryness of the skin around the eyes; the presence or absence of tears ("Can you cry tears?"); previous experience and level of success with contact lenses (comfort and wearing time); and what type of contact lenses (brand name is also helpful) and lens care system were used.
During the pre-fitting examination, pay careful attention to the eyelids, margins, eyelashes, and to the palpebral conjunctiva as well as to the degree of overall injection, sensitivity during eyelid eversion, the depth of the lacrimal lake, and the presence of fluorescein staining.
Corneal topography is an essential part of every contact lens work-up for both new fits and refits. A careful examination of the live action video image will demonstrate with vital clarity how well the patient's tears wet his corneas, how quickly the corneal surface dries as the tears migrate from the surface, and how rough that surface is, once dried. Simply put: the easier it is to get a clear topography image, the easier it will be to treat the patient and the less likely that he will develop CLI.
Topography also shows us fine details of corneal astigmatism. While low degrees of central astigmatism can be treated with spherical lenses, higher degrees or broader areas of astigmatism may require toric peripheral curves or even a full back-surface toric geometry for comfort and stability.
More obviously demonstrated by topography are the corneal ectasias, both primary and secondary. Fitting these corneas with lenses specific to their topographies can radically increase chances of comfort and success.
Pre-Existing Conditions Any patient presenting to a contact lens clinic intent upon contact lenses but demonstrating marginal blepharitis, meibomian gland dysfunction, or other external processes must be treated before you can initiate lens fitting. If signs and symptoms subside, then you may begin fitting while concurrently continuing treatment. Emphasize that this treatment must continue to enhance the contact lens experience.
A patient presenting for a refit or investigating orthokeratology as an option but who exhibits GPC must similarly be treated — preferably during a lens-free month — before fitting. You must also help such patients understand that once their condition quiets, they will need to use mast cell inhibitors to help them tolerate their contact lenses.
The constellation of borderline dry eye symptoms can, for many sufferers, severely limit their use of contact lenses. You need to help these patients or counsel them away from contact lens wear. For borderline dry eye patients who want to consider contact lenses as an option, carefully investigate the quality and quantity of the tear supply. While treatments are both time consuming and relatively expensive, patients must perform them consistently with full compliance to avoid intolerance. Take all of these steps before attempting to fit contact lenses that are advertised as "wetter" and "more comfortable for drier eyes." Basic eye lachrymosity is a much more important determinant than is the composition of the contact lens material for how well patients will succeed with their lenses.
Blinking Issues If any of your patients blink either incompletely or too infrequently, you similarly need to train them to develop correct blinking habits or counsel them away from lens wear.
For those of us who have lived and studied in Boston, the phrase "red line" conjures up memories of traveling the MBTA. For those of us who have become contact lens specialists, the complaint of a "‘red line’ on the white of my eye" creates a totally different "train" of thought. Cosmetically, the engorged horizontal conjunctival capillaries signal the likelihood of corneal desiccation and SPK at 3 o'clock and 9 o'clock and conjunctival drying at those locations. This entire scenario proceeds from incomplete blinking: generally down to the superior lens edge and pushing the lens inferiorly. The triangles just above the lens edge at 3 o'clock and 9 o'clock never benefit from tear circulation. The inferior lacrimal meniscus is never accessed to wet the lower third of the cornea. The outer surface of the lens dries, attracts debris, and becomes a barrier rather than an accessory to sharp vision.
As the process progresses, the surface of the eye and of the contact lens dries further; the eyes become redder and increasingly more irritated. The exposure can aid in the growth of pingueculae. The lack of complete blinking may be instrumental in the formation of plugs in meibomian gland orifices.
Depending upon the degree of progression, initial treatment should include learning the basics of correct blinking, warm lid massages, saline rinses, and assiduous contact lens care. Additional strategies from Dr. Schendowich for managing lens discomfort, dryness, and blinking issues are available in the May 2003 Readers' Forum article titled, "Four-Point Plan to Achieve Comfortable Contact Lens Wear."
Consider Lens Refitting Patients who require contact lenses either because of a visual handicap or because of other needs but who have become intolerant might benefit from contact lens refitting. The direction this exercise will take depends upon the eyes and the cause of the intolerance. The degree of change may be as small as a power change; it may be change in material to one of a higher Dk or a reduced modulus. You might refit a patient from GP lenses to silicone hydrogels or from soft lenses to GPs. Or for any of many reasons, you might refit a semi-scleral or full scleral lens in place of a smaller GP lens design.
Lens, Compliance, and Handling Issues
CLI can result from damage to the contact lens surfaces, edges, or curvatures; from solution sensitivity; from lens care noncompliance; or from other handling issues.
In the case of an old or damaged contact lens, the patient is always better off with a new lens. We can occasionally attempt to put off the inevitable by polishing the surfaces and re-edging GP contact lenses.
Solution sensitivity is far less likely to occur with multipurpose solutions currently in use compared to the thimerosal-chlorhexidine blends that were in use in the early decades of soft contact lenses. Nevertheless, various solution/soft lens combinations do not mix. The recent and ongoing work of Andrasko available at www.staininggrid.com advises us about how to avoid these problems.
Over the years we've found that one of the greatest sources of aggravation with contact lenses and an extremely curable source of CLI is the ‘touched contact lens.’ Many patients — not necessarily those new to contact lens wear — examine their soft contact lenses for correct sidedness and cleanliness before applying. This is good in and of itself. But, you must remind lens wearers who do this to rinse the lens with sterile soft contact lens solution before applying it. The bits of grit and finger oil transferred from the fingertip to the lens act as extremely annoying irritants to the epithelium. Countless and most likely unnecessary changes in lens care systems occurred until we solved this dilemma.
In the last few years, the contact lens world was stricken by two distinct events of microbial keratitis involving contact lenses and care solutions. The lessons learned from those experiences also apply to preventing CLI:
- Keep lens cases clean.
- Clean and dry hands thoroughly before handling lenses.
- Clean lenses as directed after each use.
- Store in fresh solution only — no topping off.
- Store in recommended solution only.
- Never bring soft contact lenses into contact with tap water.
Learn and Teach Patience
Very little comes automatically and immediately. To succeed with patients who claim or demonstrate CLI in any degree, we must be patient with them and nurture their patience as well. The effects that result from pre-treating abused lids or encouraging more effective tear composition will pay off only if worked at patiently day after day.
Slowly building up tolerance to contact lenses by gradually adding wearing time on a daily basis requires strength of will to keep to a schedule and to neither rush the process nor skip prescribed days.
CLI as an entity can most likely not be eliminated. Our goal is to improve comfort, ocular health, and the overall lens-patient relationship to help affected patients overcome their CLI.
We can help prevent CLI by carefully selecting potential contact lens patients. We can further help prevent it by pre-treating many external conditions before the first fitting session. If potential contact lens patients are amenable and compliant with the pre-treatment in preparation for the lenses, then the potential for success is enhanced.
CLI is a greater problem for patients whose corneas require optical correction that only contact lenses can provide. You can help many of these patients through pre-treatment, continued medical treatment, lid and blink therapy, or through redesigning their lenses.
Helping this group of "critical care" contact lens patients to enable them to tolerate their lenses can change their lives. This is indeed the challenge of our practice. CLS