Ever wondered why some patients present with dry eye complaints, yet no obvious dry eye clinical signs are observed? Dry eye is one of the most common complaints of patients presenting for an ocular examination. Although dry eye has received increased attention in clinical research and general public awareness since the 1995 National Eye Institute/Industry report on clinical trials in dry eyes,1 its origin is still not well understood.
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For years in private practice the clinical diagnosis of dry eye condition has been limited to the Schirmer test, tear film break-up time and fluorescein staining of the ocular surface. Clinical trials also included the use of dry eye questionnaires as a diagnostic requirement for the condition. These tests diagnose dry eye on the basis of either insufficient tears or tear film instability. But an anomaly occurs when a patient reports with dry eye symptoms in the absence of these clinical signs.
A new finding, lid wiper epitheliopathy (LWE), has been identified by Korb and co-workers.2 This recently reported syndrome occurs in the presence of dry eye symptoms despite the absence of other positive clinical findings.
Lid Wiper Epitheliopathy in Clinical Practice
While examining the palpebral conjunctiva after eversion of the upper eye lids, Korb et al2 noticed repeated observations of fluorescein and rose bengal staining of the epithelium of a particular portion of the upper eyelid marginal conjunctival.
Korb named this section of the upper eyelid ‘lid wiper’ to reflect its role in wiping the ocular surface during blinking. Compared to the anatomically normal Marx’s Line (Fig.1), the lid wiper is a more diffuse, wider and more proximally located staining band (Fig. 2).3
Figure 1: Marx’s line stained with lissamine green. Photo: IER
Figure 2: Lid wiper epitheliopathy stained with lissamine green. Photo: IER
This interesting discovery has sparked further investigations by Korb et al. To determine the prevalence of lid wiper epitheliopathy (LWE), 50 dry eye symptomatic and asymptomatic non-contact lens wearers were evaluated.4
The examination was conducted four hours after waking. Both fluorescein and rose bengal were used in the evaluation of the ocular surfaces due to their difference in epithelial staining properties (i.e. fluorescein penetrates areas of interrupted continuity of cornea and conjunctival epithelium, while rose bengal stains the nuclei of dead or degenerated cells and mucus.5)
The length and width of the stained lid wiper was measured and graded for each type of dye, with the average grades from both dyes used as a final score to classify the severity of LWE (0-3) (where 0 = none, 1 = mild, 2 = moderate and 3 = severe).
The study found the symptomatic group had a six times more frequent occurrence of LWE compared to the asymptomatic group (76 per cent vs. 12 per cent). Symptomatic participants also had a higher prevalence of grade 2 and grade 3 LWE.
These findings are also evident in contact lens wearers. An earlier study conducted by Korb et al found 80 per cent of symptomatic contact lens wearers displayed LWE as compared to 13 per cent of asymptomatic wearers.2 Likewise, grade 2 and grade 3 LWE were more common with symptomatic than asymptomatic contact lens wearers.
An interesting observation arising from these studies was that the use of both fluorescein and rose bengal are essential in detection of LWE, as this particular area may only stain with one type of the dye but not with the other. Limited understandings of the mechanism for ocular staining preclude us from providing an explanation of this particular observation.
A more recent study employed the use of fluorescein and lissamine green dyes in the detection of LWE.6 Lissamine green is thought to have similar properties to rose bengal and does not sting on instillation. LWE was found in 88 per cent of symptomatic participants and only 18 per cent of those who were asymptomatic with either or both dyes. The likelihood of having LWE ≥ grade 2 was 16.5 times greater in the symptomatic population compared to the asymptomatic.
These studies have suggested a strong correlation between LWE and dry eye symptoms in both contact lens wearers and non lens wearers, and may be useful in the diagnosis of dry eye.
To avoid missing this condition, the following is recommended:
- Routinely perform lid eversion as part of primary eye care examination
- While the lid is everted, observe the entire lid, not just the tasal conjunctival
- Make sure an adequate amount of fluorescein and lissamine green is applied to the eye
- Avoid confusing LWE with a normal variation in the anatomy of the lid wiper region.
Treating the Condition
All participants in the above studies had normal Schirmer test values, regardless of whether they were symptomatic or not. It is therefore possible that tear film dysfunction rather than tear volume compromises lubrication between the epithelium of the two surfaces.
Lubricating agents may be useful in treating the condition – the use of artificial tears during waking hours and lubricating ointments at bedtime could possibly offer some improvement.
McMonnies has suggested that incomplete blinking habits may play a role in LWE. His suggestion is based on a theory proposing that with a desiccated cornea, an increased frictional force between the lid wiper/ocular surface interface may be encountered. This is because after an incomplete blink, the tear film at the inferior cornea is thinnest.
A subsequent complete blink will cause the lid wiper to pass over the thinner tear film, increasing frictional forces and potentially damaging both surfaces. For patients with incomplete blinking habits, McMonnies suggest blinkefficiency training.7
The Take Home Message
When a patient presents with dry eye symptoms, routinely evert the eyelids and assess with both fluorescein and lissamine green. Patients with LWE should be provided with a treatment program that includes lubricating agents and blink efficiency exercises if incomplete blinking habits are noted.
NB: The Institute for Eye Research and University of Western Sydney will host an international exchange of leading researchers to progress the development of solutions to dry eye, from 3 to 8 August. For more information please contact Maureen Story on: (AUS) 02 3855 7462 or email: [email protected]
Rebecca Weng B.Optom (Hons), Grad Dip (I&T), NAATI (Translator English/Chinese), a Clinical Optometrist at the Institute for Eye Research. The author would like thank Daniel Tilia, Nicole Carnt and Percy Lazon de la Jara for their assistance.
References:
- [cited 2009 12 June]; Available from: http://www.touchscientific.com/NEI.pdf.
- Korb, D.R., et al., Lid-wiper epitheliopathy and dry-eye symptoms in contact lens wearers. CLAO Journal, 2002. 28(4): p. 211-6.
- Donald, C., et al., A quantitative assessment of the location and width of Marx’s line along the marginal zone of the human eyelid.[erratum appears in Optom Vis Sci. 2003 Oct;80(10):720 Note: Hughes Claire [corrected to Donald Claire]]. Optometry & Vision Science, 2003. 80(8): p. 564-72.
- Korb, D.R., et al., Lid wiper epitheliopathy and dry eye symptoms.[see comment]. Eye & Contact Lens: Science & Clinical Practice, 2005. 31(1): p. 2-8.
- Norn, M.S., Vital staining of cornea and conjunctiva. Acta Ophthalmologica, 1962. 40: p. 389-401.
- Korb, D.R.e.a., Prevalence of Lid Wiper Epitheliopathy in Subjects with Dry Eyes Signs and Symptoms, in ARVO. May 2009: Fort Lauderdale.
- McMonnies, C.W. and C.W. McMonnies, Incomplete blinking: exposure keratopathy, lid wiper epitheliopathy, dry eye, refractive surgery, and dry contact lenses. Contact Lens & Anterior Eye, 2007. 30(1): p. 37-51.
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