Complications When You Least Expect Them

Sometimes unusual lens complications can appear in your everyday contact lens practice.


Complications When You Least Expect Them

Sometimes unusual lens complications can appear in your everyday contact lens practice.

Dr. Hui is currently a PhD candidate at the Centre for Contact Lens Research, University of Waterloo. He is supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada, the Canadian Optometric Education Trust Fund (COETF), and a Vistakon Research Grant and Ezell Fellowship, both administered by the American Optometric Foundation (AOF). His thesis work on the development of novel drug delivery materials is also supported by the NSERC 20/20 Network for the Development of Advanced Ophthalmic Materials. He can be reached at

By Alex Hui, OD

“When you hear hoofbeats, think horses, not zebras.” This oftcited expression is commonly used in medical and optometric education to illustrate the difference between the common, everyday conditions encountered in practice and the weird, wacky, or rare conditions that may come along only once or twice in a career. The caveat to this phrase of course is that this concept may prove unreliable if you happen to be on the plains of the Sahara, where zebras are much more common than horses are.

The relevant point is that you must be cognizant of your specific patient population and direct your clinical investigation into the problems that are most likely to impact them. Contact lens wearers present one such specific population, with its own set of risk factors. Microbial keratitis, infiltrative inflammatory events, dry eye, discomfort, solution sensitivity, and fluctuating vision are all examples of contact lens-related problems in which veteran—or even novice—practitioners are well versed and prepared to consider, diagnose, and manage. I will therefore not focus my attention in this article on commonly observed conditions, but instead illustrate through a series of case examples some rarer contact lens complications that you may encounter when you least expect them.

Case 1: “Sometimes you just have to look harder!”

Case 1 pertains to a 60-year-old male patient who presented to the clinic as the result of a growing mass on the superior right eyelid. He had been a GP contact lens wearer for many years without any complications. The patient's visual acuity was good, and a general assessment of the rest of the visual system was unremarkable.

Further probing of the history suggested that the mass had been enlarging for several months, but it was neither painful nor overly inflamed. On examination, a palpable, movable mass was observed in the nasal portion of the superior right eyelid, and simple eversion of the eyelid showed no detectable mass.

Given this presenting information, the differential diagnosis would include common conditions such as a chalazion or hordeolum. Considering the patient's age and the rapid course of the growth, the possibility of a rare meibomian gland carcinoma would also need consideration, which would require a biopsy for confirmation (Shams et al, 2011). In this case, referral resulted in the patient being scheduled for surgery. When the surgery began, a needle inserted into the mass encountered a very hard surface. Double eversion of the lids and surgical dissection of the mass released a small amount of fluid and mucopurulent material, as well as an embedded, completely intact, GP contact lens that was reportedly lost some three years previously.

Retained GP contact lenses are an uncommon complication of contact lens wear (Jones et al, 1987), and the difficulty in diagnosis primarily results from the non-specific symptoms that they elicit. Surprisingly, not all cases result in the development of lid masses, and patients frequently complain only of non-specific eye irritation, which is often dismissed as dry eye symptoms associated with contact lens wear (Zola et al, 2008). Other patients have reported mucus discharge and lid swelling.

The history and time course are also very interesting. When questioned, patients may only vaguely remember losing a contact lens many years ago, with the presumption that it had fallen out rather than was retained under the lid. While embedded, the lens can cause little or no symptoms until some other event causes a mass to grow, or until the patient experiences discomfort and pain (Zola et al, 2008). Retained contact lenses also need not be unilateral, as there have been case reports of bilateral embedded lenses (Perera et al, 2008).

The period over which lenses remain embedded can also be incredibly long, with some cases describing asymptomatic embedded lenses for almost 40 years (Shams et al, 2011). Interestingly, when histology is performed on the eyelid tissues surrounding the retained lens, there are only slight signs of necrosis and granulomatous tissue, with a complete absence of giant cells or other signs of severe inflammation (Jones et al, 1987). This highlights the biological inertness of rigid materials, the best example being polymethyl methacrylate, as even retention for many years does not initiate a large-scale immune response to remove the foreign body.

Thankfully, excision and removal of these embedded lenses generally yield complete resolution of the patient's symptoms. The “upper fornix trap” has been a postulated causative mechanism for the retention of rigid lenses. In this theorized mechanism, the contact lens edge becomes embedded in the upper tarsal plate, especially if the lens becomes flipped such that the concave surface faces the anterior surface of the eyelid. The lens edge causes local necrosis, and the conjunctiva eventually grows over the lens (Zola et al, 2008). The authors of these cases recommend the use of double lid eversion in cases of suspected retained lenses, as this is the only method of potentially identifying the deeply embedded mass. The conjunctival “O” sign has also been described. An everted lens trapped within the conjunctiva will have sharp, raised edges with a depression in the center.

Case 2: “Will you be using both eyes, or only one?”

Case 2 concerns a 45-year-old woman wearing soft contact lenses. She had been a successful contact lens wearer for many years, but at her last progress check six months previously she reported difficulty with reading while wearing her lenses. Examination at that time was unremarkable except for newly diagnosed presbyopia, which was corrected with both a new pair of progressive addition spectacles and modified monovision in her contact lenses, biasing her non-dominant right eye for near work. She was quite happy with the spectacles and contact lenses at that time, but presented at her next visit with complaints of intermittent double vision. She first observed the double vision a month prior and reported that it had been steadily increasing in frequency over the past month, worsening when she was tired. She did not remember this ever occurring before, but recalled possibly having eye surgery as an infant.

Upon further questioning, she noticed that this problem occurred only while wearing her contact lenses. The differential diagnosis for sudden onset of double vision includes some conditions that are potentially life-threatening, notably stroke, aneurysms, and brain tumors, and thus calls for prompt evaluation and treatment. For this patient, these diagnoses were promptly ruled out, suggesting a possible binocular vision problem with her contact lenses.

Evaluation of her binocular vision status while wearing her lenses showed a constant left exotropia in office, which became an exophoria with spectacles. Further evaluation while wearing only distance contact lenses in both eyes with a pair of reading glasses for near work also showed an exophoria, in the absence of strabismus. The patient was thus easily fitted with a full distance correction in her contact lenses and prescribed a pair of readers for near vision. Further follow-up appointments were unremarkable, other than confirmation from the patient's parents that the surgery performed when she was a child was for “crossed eyes.”

In day-to-day practice, practitioners rarely consider a patient's binocular vision status when fitting different types of contact lenses (Pollard et al, 2011). Indeed, for most patients, going from spectacles to contact lenses is a relatively seamless transition, unless they have a significant degree of ametropia, in which case they may experience minification or magnification effects (Evans, 2006). Occasionally, induced prismatic effects when converging for near work (in which the patient experiences base-in prism if wearing minus lenses and base-out prism for plus lenses) can cause some visual discomfort during prolonged contact lens wear and reading, but this rarely becomes clinically significant. However, as Case 2 illustrates, there are occasions in which unique patient characteristics may cause the more complicated contact lens corrections to disrupt the visual system.

Intermittent strabismus or double vision caused by monovision correction has been reported (Godts et al, 2004; Evans, 2006; Pollard et al, 2011). In many of the cases, the patients demonstrate a previous history of binocular vision dysfunction, be it a history of vision training, strabismus surgery, or amblyopia. Decompensation after monovision prescribing can take patients from a tolerable binocular vision status to strabismus. This can occur anywhere from months to years after initial prescribing, with most patients decompensating after three years or more of monovision wear (Pollard et al, 2011). The causal theory is that the additional blur in the nondominant eye induced by monovision causes a patient who has poor binocular fusion lock to decompensate into a strabismic state. This clearly has implications beyond contact lens wear, and similar cases have been reported of strabismus arising after monovision laser and cataract surgery. In some cases, in which the refractive correction is more permanent, strabismus surgery was required to correct intractable diplopia (Godts et al, 2004). In most cases, full distance correction with contact lenses generally leads to a good fusional outcome, although in some cases, strabismus surgery is still required.

When considering monovision, conduct a thorough history. Particular attention to a history of patching, strabismus surgery, or vision training can alert you to potential future binocular vision problems with such corrections. Indeed, the development of improved multifocal contact lenses may provide better alternatives for patients, regardless of their pre-existing binocular vision status (Martin and Roorda, 2003).

Case 3: “Never forget that the eye doesn't end at the cornea!”

Case 3 pertains to a longtime male presbyopic patient. He had recently begun a busy, high-paying job in the financial sector and thus requested to be fit with multifocal contact lenses. After the initial fitting, the patient was relatively happy and determined to continue using the multifocal contact lenses. He returned to the clinic after some time complaining of mild “blurriness” primarily for his near vision. This decrease in visual acuity was adversely affecting his work performance, although he suggested that it may simply be due to “stress.”

During his previous visits, there was a low myopic prescription with all other ocular findings being normal. At this visit, distance visual acuity through the contact lenses was 20/20 in the right eye, 20/40 in the left, with the right eye wearing a “low” add, and the left eye wearing the “mid” add for the multifocals. The fit and centration of the lenses appeared to be adequate, thus attention was focused on over-refraction of the left eye. A +0.75D over the left eye provided the best visual outcome, but after an initial trial with this lens for a week, the patient continued to complain that something was “just not right.”

A few more weeks passed during which the distance prescription and add powers of the left and right lenses were adjusted in a failed attempt to generate an acceptable visual outcome. After several trials, the patient also mentioned a vague description of the vision being “wavy” rather than merely just blurry, which prompted an Amsler central screening test, dilated fundus examination, and optical coherence tomography (OCT) examination. This resulted in a diagnosis of Central Serous Retinopathy (CSR).

The cautionary tale of Case 3 highlights the need for an overall or holistic view of a patient's visual system and visual perception when managing contact lens complications. It is tempting to assume with a patient who is fitted with a complicated lens type (such as a toric or a multifocal) that any and all visual complications are due to the contact lens itself. The key to avoid overlooking such complications—or misdiagnosing the problem as merely a contact lens-related complication—lies in your vigilance and curiosity. Misdiagnosis will occur with all practitioners at some point in their careers, whether they are an expert or novice within the field. However, it can be mitigated or minimized if you continue to maintain an open mind about possible diagnoses or causes for patients' clinical signs and symptoms and have a genuine concern for your patients' well-being. In this case, while the multifocal fit may be a potential cause of the patient's visual symptoms, CSR should have been considered sooner, given the characteristic history of stress, male gender, and rapid, mild, monocular hyperopic shift (Ferrara et al, 2008; Tarabishy et al, 2011). Fortunately, misdiagnosis for a short time in this case had no long-term implications, as the principal treatment for CSR is supportive counselling on stress relief and observation using dilated fundus examinations as the retina returns to normal, which generally takes a few months (Tarabishy et al, 2011). However, missing complications such as macular edema due to other issues including retinal detachment, hypertensive retinopathy, or diabetic changes could be far more severe.


The lofty—and possibly unattainable—goal of the contact lens industry is to integrate and make contact lens wear so seamless and well-designed that it is complication-free. The unfortunate reality is that as long as patients wear contact lenses, complications will occur. The common—and sight-threatening— complications that we see in day-to-day practice will continue to pose a challenge to contact lens practitioners worldwide, but will remain at the forefront of the minds of eyecare practitioners as they encounter problem-specific exams with contact lens patients.

I hope the illustrative cases presented will encourage you to also strive to keep an open mind regarding other causes when complications arise from seemingly common cases. Look out for those occasional zebras! CLS

For references, please visit and click on document #202.