Detecting Dry Eye in Contact Lens Wearers

Learn how to recognize this evasive condition before discomfort drives these patients out of their lenses.

BY KELLY A. KINNEY, OD
JUNE 1998

It's not uncommon to hear contact lens patients express symptoms of dry eye. It has been well documented that contact lens wear and dry eye often go hand in hand. Since contact lenses alter the precorneal tear film, contact lens wear is often considered a causative factor of dry eye. Contact lens wear can also exacerbate an underlying dry eye condition, resulting in contact lens discomfort or intolerance. Many factors influence contact lens comfort, including deposits on the contact lens surface, the fit of the lens, blink patterns and the contact lens-lid interaction. How can you ensure that patients wearing contact lenses are appropriately monitored for dry eye? An in-depth case history and a concise battery of dry eye tests can provide the answer.

Patient History

Patients may report that their lens comfort is adequate, yet they're unable to wear their contact lenses for as long as they desire -- a symptom that can go undetected if not specifically questioned. In addition to asking the routine contact lens related questions, remember to address symptoms of dryness and irritation including contact lens wearing time. Dry eye questionnaires, such as the standardized McMonnies' Dry Eye Questionnaire, can help you assess the severity of symptoms and elicit systemic risk factors, including the use of medication. Questionnaires are easily administered to patients at the time of check-in and can be scanned during the examination.

Understanding the Condition

In 1995, the National Eye Institute sponsored a dry eye workshop to establish a global diagnosis for dry eye and to set forth recommendations to the ophthalmic community regarding the diagnosis and management of dry eye patients. The new definition of dry eye states that it is a disorder of the tear film resulting from tear deficiency or increased evaporation leading to interpalpebral ocular surface damage accompanied by dry eye symptoms. Although this definition appears to be absolute, dry eye can be diagnosed in the absence of symptoms or ocular surface damage, so it's important to rule out "masqueraders" to ensure proper management of underlying disease (Table 1). Many of the difficulties we have in diagnosing dry eye stem from the general lack of knowledge of the underlying mechanisms. It's generally thought that increased tear film osmolarity is the common link between evaporative and aqueous deficient dry eye, which results in damage to the corneal epithelial cells and the conjunctival goblet cells. Efforts to understand these mechanisms continue to aid in our diagnosis.

Diagnostic Procedures

Perform a standard battery of dry eye tests on all patients suspected of having dry eye. When you assess the patient's symptoms, ask about related systemic disease and medications used. Collagen vascular disorders, such as rheumatoid arthritis and autoimmune diseases including Sj�gren's syndrome can produce severe dry eye symptoms. Antihistamines, birth control pills and diuretics can also alter the tear film and lead to dry eye. Asking patients if they feel they have dry eye can be a strong indicator of their subjective dry eye status.

Slit Lamp Exam -- Following the patient history, perform a complete slit lamp evaluation. First, assess the quantity and quality of the inferior tear prism (Fig. 1). When measuring tear meniscus height, using a reticule installed into the slit lamp oculars will aid in measurement consistency. You can observe tear debris using a parallelepiped biomicroscope slit beam illumination and specular reflection to focus on tear film movement following the blink. Increased debris and scant, mucus-filled tears are signs of dry eye (Fig. 2). Evaluating lid regularity and blink frequency can pinpoint problems in the redistribution of tears over the ocular surface. An incomplete blink can continuously leave an area of the cornea exposed without the protective tear film. Irregularities in the lid margin can also prevent normal surfacing of the tear film over the cornea and lead to disruption of the corneal and conjunctival epithelium.

FIG. 1: Evaluation of tear prism

FIG. 2: Scant tear prism.

Finally, evaluate the meibomian glands and lashes for signs of blepharitis and meibomian gland disease, both of which contribute to evaporative dry eye. Assess meibomian glands for blockage or "capping" of the glands, as well as for chalazion or hordeola. A history of chalazion or an oily or gummy tear film and lid margin can indicate meibomian gland dysfunction. Coupled with symptoms, irregularities in the above findings can lead to a dry eye diagnosis.

TBUT -- In addition to the slit lamp examination, tear break-up time (TBUT) testing provides an assessment of the stability of the pre-corneal tear film (Fig. 3). The use of a Wratten #12 yellow filter can enhance the fluorescein dye viewed with cobalt blue light. Record the location and time of the tear break-up. Studies have shown that it's easier to determine tear break-up using a wide beam versus using a narrow scanning beam. The wider the beam, however, the more decreased contrast between the fluorescein dye and the area of break-up. Try using a three- to four-millimeter beam, taking care to observe the location of the break-up. A tear break-up time of 10 seconds or less is considered abnormal and tends to be inferior on the corneal surface.

 

FIG. 3: Tear break up time (TBUT).

Staining -- Evaluate and record fluorescein staining patterns on the corneal and conjunctival epithelium. Interpalpebral conjunctival staining can be difficult to assess in comparison to the corneal epithelium. Due to the loose nature of the conjunctival adhesion to the underlying tissues, the fluorescein dye collects in minute ridges and can mimic epithelial cell loss and staining. True fluorescein staining of the conjunctiva can best be seen if the fluorescein has been allowed to dissipate and is enhanced by the Wratten #12 yellow filter.

It has been well established that contact lens wear can cause superficial punctate keratitis on the corneal surface. The most common form of staining is the 3 and 9 o'clock staining found in RGP lens wear. With hydrogel soft lenses, staining patterns can be diffuse or localized to regions of the cornea, generally the inferior cornea. Even without dry eye, the cornea of a contact lens wearer can show signs of epithelial damage. The key in dry eye diagnosis is to differentiate staining that's secondary to the contact lens from staining that's found in dry eye. If you suspect dry eye during a routine contact lens evaluation, evaluate the patient on another occasion following temporary discontinuation of contact lens wear. If symptoms and staining patterns persist, be suspicious of dry eye syndrome.

Diagnosis of dry eye in a contact lens patient by fluorescein staining patterns alone would be presumptuous. In addition to fluorescein staining, evaluate staining of the cornea and conjunctiva with either rose bengal or lissamine green dye (Dakryon Pharmaceuticals, Lubbock, Texas) (Fig. 4). Lissamine green has not been found to induce the same ocular irritation as rose bengal and is reported to have identical staining patterns. Fluorescein, lissamine green and rose bengal staining are best recorded using the diagram recommended in the Report of the NEI Dry Eye Workshop. The diagram divides the cornea into five regions and the conjunctival surface into six areas, allowing improved localization of staining patterns (Fig. 5).

FIG. 4: Rose bengal staining

Evaluating Aqueous Production -- Although contact lens related dry eye is generally classified as evaporative, it's important to evaluate aqueous production using the Schirmer test or the phenol red thread test. Controversy exists regarding the validity, repeatability and the use of anesthetic with the Schirmer test. Studies show that the use of anesthetic decreases tear production significantly, so it's recommended that the Schirmer test be performed without anesthetic. However, many clinicians still feel that the anesthetized results reflect true basal secretion. A result of 5mm of wetting or less in five minutes signifies a decreased aqueous production.

The Zone-Quick phenol red thread test (Showa Yakuhin Kako Co., Ltd. & Menicon USA, Inc.) is gaining popularity due to the ease of measurement in comparison to the Schirmer test. After inserting the thread over the right inferior lid margin at the same location as described for the Schirmer test, the patient looks straight ahead and blinks normally for 15 seconds. The thread is then removed and measured to the nearest millimeter, and repeated for the left eye. A result of 10mm or less is an indication of dry eye, although the test may need to be repeated several times to increase validity. Table 2 is a summary of dry eye tests and diagnostic values.

TABLE 2: Diagnostic tests for dry eye

TEST	ABNORMAL VALUES
Tear meniscus height Tear film quality Fluorescein tear break-up time Fluorescein staining Rose bengal or lissamine green staining Schirmer tear test (without anesthetic) Phenol red thread test Lactoferrin analysis � 0.3 mm >= Grade 2 debris � 10 sec. >= Grade 1 (or more) staining in 3 regions >= Grade 1 (or more) staining in 3 regions � 5 mm/5 min. � 10 mm/15 sec. � 0.9 mg/mL

Advances in Testing Technology

The measurement of tear osmolarity has been referred to as the gold standard diagnostic dry eye test due to greater sensitivity and specificity, but the testing procedures are technical and require significant training and expertise. Although newer edition osmometers such as the Advanced Instruments osmometer require a smaller tear sample than previous instruments and are more portable, the instrumentation is expensive and not clinically available.

The measurement of lactoferrin concentration as an indicator of dry eye has been in existence for many years. In the past, lactoferrin analysis has been cumbersome to perform and required a three-day incubation period before results could be analyzed. Recently, Touch Scientific, Inc., (Raleigh, N.C.) has developed the Tear Touch Lactoferrin Microassay System, which requires approximately one to two microliters collected with a capillary tube from the inferior tear meniscus. The test can be performed in the office while the patient is present. A result of less than 0.9mg/mL indicates dry eye.

Other non-invasive TBUT devices are available, including the Keeler TearScope (manufactured by Keeler Ltd. and distributed by EagleVision, Inc.), which also allows you to qualitatively evaluate the lipid layer.

Management

Diagnosing dry eye in the contact lens patient is similar to detective work. Once all the puzzle pieces have been collected and the usual suspects ruled out, management is straightforward. Dry eye patients tend to deposit proteins and mucus on their lenses faster than non-dry eye contact lens wearers. Therefore, switching conventional lens wearers to a disposable or frequent replacement soft contact lens may be beneficial. Cleaning and disinfection systems using a separate daily cleaner, preferably alcohol-based, are most effective in removing lens deposits, and the addition of a weekly enzyme or more frequent replacement may also reduce discomfort. Some studies suggest that low water content lenses are more comfortable for the dry eye patient, while others suggest that the thickness of high water content lenses has a therapeutic effect on the corneal epithelium. In general, low to moderate water content, non-ionic contact lenses are often the preferred soft lens choice for dry eye patients. Some clinicians advocate a switch to RGP lenses, considering that there's usually less protein deposition on an RGP lens. Adaptation to RGPs should be monitored closely, especially for part-time contact lens wearers. Current RGP lens wearers may need more frequent lens polishing or possibly the addition of a weekly enzymatic cleaner.

Using non-preserved lubricant eye drops to prevent drying of the contact lenses is the first step in treating dry eye. Patient education regarding environmental conditions, such as computer screen location and heating vent placement in the workplace, aid in relieving eye irritation. Frequent computer breaks are also beneficial. If the above regimens are unsuccessful or too cumbersome for the patient, a trial of collagen plugs in the inferior puncta is warranted. Improvement over the course of the one- to two-week trial indicates that semipermanent silicone punctal occlusion will be beneficial.

Be sure to address and treat any pre-existing lid hygiene disorders. Chronic meibomian gland disorders are common in combination with dry eye and may need topical and oral medication (doxycycline or tetracycline) for resolution, depending on the severity of the condition.

Once dry eye is diagnosed, it's important to follow up on the patient's progress with the prescribed therapy. Often, the diagnosis of dry eye is carried from examination to examination without modification of unsuccessful therapy. Comparison between visits of subjective symptoms, the TBUT test, and fluorescein and either rose bengal or lissamine green staining patterns are the most predictive of therapy success. With the addition of a few tests to the contact lens examination, contact lens patients with dry eye can be successfully managed, increasing the comfort of both you and your patients.

Dr. Kinney is a graduate student at The Ohio State University College of Optometry in the area of dry eye research.

 

The Case of Decreased Contact Lens Wear Time PART 1: HISTORY Patient M.J. presented to the OSU contact lens clinic for a routine contact lens examination. The vision and comfort of her soft contact lenses were unchanged. Average wearing time was five to six hours, approximately two to three times per week. When questioned, M.J. revealed that she would like to wear her lenses for a longer period of time on a more regular basis but the lenses were comfortable for only five to six hours with occasional use of rewetting drops. Once irritation and discomfort began, she removed them. M.J. had a negative ocular and medical history. She was not currently taking any medications, and reported mild seasonal allergies. She reported dryness, a gritty sensation and soreness of the eyes on an occasional basis, both with and without contact lens wear. She used artificial tears two to three times per week; more frequently with contact lens wear and increased computer work. There had been no change in the multipurpose cleaning/disinfection solution used for lens care. McMonnies' dry eye questionnaire revealed ocular sensitivity to environmental conditions and lagophthalmos.

 

The Case of Decreased Contact Lens Wear Time PART 2: DRY EYE TESTING Contact lenses had not been worn for the previous 3 days. Slit Lamp Evaluation revealed complete blinking, normal lid margins and no blepharitis. Grade 1 tear debris was present, as well as Grade 1 meibomian gland dysfunction in both eyes. Tear meniscus height: OD: 0.1mm OS: 0.2mm TBUT: OD: 9 sec./inferior OS: 10 sec./inferior Fluorescein staining: OD: Grade 2 nasal conjunctival staining Grade 1 temporal conjunctival staining OS: Grade 2 nasal conjunctival staining Grade 1 nasal corneal staining Grade 1 inferior corneal staining Grade 1 temporal conjunctival staining Rose bengal staining: OD: Grade 1 nasal conjunctival staining OS: Grade 1 inferior conjunctival staining Phenol red thread test OD: 12 mm/15 sec. OS: 8 mm/15 sec.

 

The Case of Decreased Contact Lens Wear Time PART 3: DIAGNOSIS AND MANAGEMENT M.J. was diagnosed as having mild dry eye based on symptoms and largely borderline test results in both eyes. The most outstanding findings were mild to moderate fluorescein and rose bengal staining of the cornea and conjunctiva. Tear production as measured by the phenol red thread test was borderline. She did exhibit a scant tear meniscus and mild Meibomian gland disease. The fit with her current soft, low-water, disposable contact lenses was acceptable. M.J. had previously used lubricant eye drops on a regular basis both with and without contact lenses; therefore, collagen punctal occlusion of the inferior puncta was performed with her consent. Following a successful trial, silicone plugs were inserted in the inferior puncta of both eyes, which relieved the majority of the dry eye symptoms. It will be necessary to follow M.J. on a regular basis to ensure the silicone plugs remain in the puncta of both eyes.