CONJUNCTIVA AND LENS WEAR

Conjunctival Responses to Contact Lens Wear

It is important to evaluate the conjunctiva and limbus of all lens wearers, even when they’re asymptomatic.

By Jill Woods, BSc (Hons), MCOptom, FAAO, FBCLA

The conjunctiva responds in a number of ways to contact lens wear. While some of these give rise to symptoms of discomfort, others do not. The conjunctiva has slowly become recognized as an important structure to observe in the presence of contact lenses.

This article describes the more common and impactful changes that can be observed in the bulbar and limbal regions of the conjunctiva as a result of lens wear. It also discusses the clinical significance of these changes and their association with comfort.

Hyperemia

Presentation Hyperemia is the level of “redness” (or decrease of “whiteness”) exhibited by the conjunctiva. It is often differentiated as either limbal or bulbar hyperemia. This conjunctival response can cause a dilation of the fine blood vessels, making them more obvious to an observer and therefore reducing the “whiteness” of the conjunctival appearance (Figure 1). Additionally, any chemosis overlying the blood vessels causes a blurring of vessel demarcation and creates the perception of pink tissue around the vessels.

Figure 1. Conjunctival and limbal hyperemia.
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Causes and Clinical Significance The location of the hyperemia can be a clue to its cause. For example, sectoral bulbar hyperemia is observed in cases of episcleritis, or it may indicate localized irritation. Limbal hyperemia, which can also be sectoral, is suggestive of corneal involvement such as abrasions or infiltrates, whereas overall bulbar hyperemia may indicate an allergic or infective response such as that seen in allergic, bacterial, or viral conjunctivitis.

Conjunctival hyperemia has been reported as being higher in contact lens wearers than in non-wearers (Maldonado-Codina et al, 2004). Factors believed to increase hyperemia in contact lens wearers are hypoxia (Papas, 1998), lens deposits (Michaud and Glasson, 2002), and loose-fitting lenses (Young and Coleman, 2001). An acute hyperemic response is generally due to something other than contact lens wear, such as a foreign body or microbial infection. One exception to this is contact lens-associated acute red eye (CLARE), which is inflammatory in nature (Holden et al, 1996).

Evidence of Association with Contact Lens Discomfort Perhaps due to the multiple possible causes, conjunctival hyperemia has not been shown to be directly correlated to contact lens discomfort (Foulks et al, 2013).

Conjunctival Staining

Presentation Conjunctival staining can be categorized into one of three distinct types, which depend on their location: limbal, lens edge-related, or more diffuse bulbar staining (Figure 2). The staining is most commonly assessed with sodium fluorescein, but lissamine green is also frequently used and has replaced rose bengal for this purpose because of greater comfort and availability. Due to their different modes of action, the staining pattern with sodium fluorescein may differ from that seen with lissamine green; sodium fluorescein is believed to visibly stain the ocular epithelial surface where cells are compromised (Morgan and Maldonado-Codina, 2009), whereas lissamine green is believed to cause visible staining by entering membrane-compromised epithelial cells (Papas, 2014).

Figure 2. Three conjunctival staining presentations: (A) Staining over the limbal region; (B) Lens edge-related (circumlimbal) staining; and (C) Lissamine green diffuse staining of the conjunctiva.
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Causes and Clinical Significance Conjunctival staining is an adverse sign, and the aim should always be to reduce or eliminate it. Limbal staining should be addressed as soon as possible to avoid complications related to the limbal stem cells (see “Limbal Stem Cell Deficiency” on page 38). Lens edge-related staining is higher with stiffer lenses and when the lens edge profile is sharply pointed as opposed to rounded (Maissa et al, 2012). Bulbar staining, or staining not associated specifically with the edge of the contact lens, may have multiple causes, including systemic disease, environmental issues, or it could represent an exposure type of staining similar to that found in non-lens wearers who have dry eye.

Evidence of Association with Contact Lens Discomfort While conjunctival staining is associated with contact lens wear (Maldonado-Codina et al, 2004; Lakkis and Brennan, 1996), it has been shown that there is a negative correlation between lens edge staining and lens discomfort, in which higher staining is associated with higher comfort scores (Maissa et al, 2012). Bulbar conjunctival staining has been associated with reduced comfort in contact lens wearers (Lakkis and Brennan, 1996; Guillon and Maissa, 2005). Interestingly, lissamine green conjunctival staining can be significantly higher in symptomatic compared to asymptomatic lens wearers (Guillon and Maissa, 2005), whereas fluorescein conjunctival staining appears to not be discriminatory (Guillon and Maissa, 2005; Pult et al, 2009).

Conjunctival Indentation

Presentation Conjunctival indentation is a depression created in the conjunctival tissue from the pressure of the edge of the lens. It should not be confused with lens edge-related conjunctival staining because, although they frequently coexist, each can also exist in isolation. Although cases of extreme indentation can be viewed with white light, the optimal observation of more subtle indentation follows instillation of sodium fluorescein, because it “pools” in the depression (Figure 3).

Figure 3. Conjunctival indentation.
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Causes and Clinical Significance The clinical implications of conjunctival indentation are unknown, and very little is reported in the literature on this topic. Anecdotal observations are that indentation is greater in the superior and inferior regions, probably caused by a thick lens edge and/or steeper fit that is then exacerbated by lid pressure. It should be regarded as an undesirable sign, as it may be an indicator of poor post-lens tear circulation and/or poor limbal vessel blood flow (Keir et al, 2010).

Evidence of Association with Contact Lens Discomfort There are no reports of associations between conjunctival indentation and contact lens discomfort.

Conjunctival Flaps

Presentation First reported in the literature by Løfstrøm and Kruse (2005), conjunctival flaps are loose, “finger-like” projections of conjunctiva that develop at the region of the bulbar conjunctiva coincident with the edge of a soft lens, particularly in the superior/temporal region (Markoulli et al, 2007). They are believed to represent a delamination and “bunching-up” of the conjunctival layers, with little or no evidence of morphological abnormalities in the affected region (Markoulli et al, 2011). Observation is best achieved under high magnification with sodium fluorescein and a barrier filter (Keir et al, 2010; Løfstrøm and Kruse, 2005) (Figure 4).

Figure 4. Conjunctival epithelial flaps.
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Causes and Clinical Significance It has been proposed that conjunctival flaps develop in response to the physical movement of the lens edge across the bulbar conjunctiva with blinking and eye movements. Greater lens/tissue interaction occurs with higher-modulus lenses, which explains why there is a higher incidence with silicone hydrogel lenses than with hydrogel lenses (Løfstrøm and Kruse, 2005; Santodomingo-Rubido et al, 2008). A sharp lens edge is hypothesized to create more delamination of the conjunctival tissue compared to a round-edged lens of lower modulus (Graham et al, 2009).

Although they have been observed in daily soft lens wear (Santodomingo-Rubido et al, 2008; Lin et al, 2005) and with GP lenses (Graham et al, 2009), flaps are more prevalent in patients who wear silicone hydrogel lenses on an overnight modality (Santodomingo-Rubido et al, 2009), with the authors of one study reporting the incidence to be more than one-third of their cohort of silicone hydrogel continuous wear subjects (Graham et al, 2009).

To date, there have been no reports of adverse consequences associated with the presence of conjunctival flaps; however, their development is considered undesirable, as the potential risks remain unexplored (Markoulli et al, 2011). Merely ceasing lens wear prompts complete resolution of the flaps (Markoulli et al, 2007; Graham et al, 2009). Clinically, refitting patients with a lower-modulus lens often prevents their recurrence.

Evidence of Association with Contact Lens Discomfort Studies have failed to show that the presence of conjunctival flaps is associated with any ocular symptoms or with contact lens discomfort, either in a causative or a reactive manner (Løfstrøm and Kruse, 2005; Markoulli et al, 2007; Graham et al, 2009).

Lid Parallel Conjunctival Folds (LIPCOFs)

Presentation LIPCOF is the accepted acronym, introduced by Hoh, for the subtle horizontal folds in the temporal and/or nasal bulbar conjunctiva close to, and parallel with, the lower lid margin (Hoh, 1995). Although best observed with a slit lamp under high magnification (20X or greater) using diffuse white light (Figure 5), they can also be viewed using optical coherence tomography imaging (Veres et al, 2011).

Figure 5. Lid parallel conjunctival folds (LIPCOFs).
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Causes and Clinical Significance It is not fully understood whether there are any clinical consequences to the development and presence of LIPCOFs. There is also no evidence of them resolving in response to any management strategies (Chalmers, 2014). LIPCOF grading has been shown to significantly correlate with dryness symptoms, fluorescein staining, tear breakup time, Schirmer 1 test, and lid wiper epitheliopathy (Berry et al, 2008; Németh et al, 2012). In a recent study, the grade of LIPCOF was significantly correlated with the percentage of almost-complete/complete blinks (Pult et al, 2013). Reports on a correlation with age remain inconclusive (Németh et al, 2012).

It is unclear whether LIPCOFs are associated with dry eye signs and symptoms because they create a drier ocular surface, or whether they are created as a result of the friction with the lid during each blink as a result of a dry ocular surface. The causative nature of this relationship has yet to be determined, though one study has shown LIPCOFs to be related to mucin quantity (Berry et al, 2008), which would suggest that dry eye may lead to LIPCOFs rather than the reverse.

Evidence of Association with Contact Lens Discomfort LIPCOFs have been reported to be significantly increased in symptomatic contact lens wearers (Pult et al, 2009). They have also been reported as a predictor of dry eye in contact lens wearers, in which the predictive power of the LIPCOF grade is increased if the nasal and temporal grades are added (Pult et al, 2009; Berry et al, 2008).

Limbal Stem Cell Deficiency

The corneal epithelium is a tightly arranged, multi-layered cellular structure that exists in a state of dynamic equilibrium; the cells are constantly regenerating and migrating anteriorly, where they become desquamated and shed into the tear film. Like other tissues within the body that undergo continual renewal, the lost cells are replaced through the regenerative properties of a group of cells known as “stem cells” (Hall and Watt, 1989). Stem cells have the capacity for self-maintenance and longevity, and they demonstrate unlimited self-renewal (Hall and Watt, 1989). The stem cells of the corneal epithelium are located exclusively at the limbus, within the basal layer of the epithelium, with the larger populations found in the superior and inferior regions (Wiley et al, 1991). This annular population of stem cells has a dual function. Not only does it provide the epithelium with a constant supply of new cells, it also acts as a barrier to prevent conjunctival cells from encroaching into the transparent corneal tissue (Jeng et al, 2011).

Presentation, Causes, and Clinical Significance Limbal stem cell deficiency has been reported to be associated with contact lens wear, and it may be associated with hypoxia, chemical sensitivity, or mechanical friction, typically presenting as focal regions of deficiency (Jeng et al, 2011). If the stem cells are destroyed, then the corneal structure and integrity are progressively compromised due to the lack of epithelial cell replacement and encroachment of conjunctival cells (Jeng et al, 2011).

Early detection can allow resolution to be achieved through simply ceasing contact lens wear and using lubricants (Jeng et al, 2011). However, in more severe cases, a limbal stem cell transplant may be warranted (Chan and Holland, 2013).

Evidence of Association with Contact Lens Discomfort As the deficiency manifests with increased corneal epithelial inflammation and lesions, discomfort increases. However, it is important to recognize that early stages of contact lens-associated stem cell deficiency can be asymptomatic and may present only very subtle clinical signs (Jeng et al, 2011).

Don’t Forget to Check the Conjunctiva

This article discusses a number of conjunctival responses to contact lens wear, and although they do not all cause contact lens-related discomfort, they do highlight the need to carefully observe the conjunctiva during contact lens wear.

Routine assessment of the conjunctiva and limbal region with lissamine green and/or sodium fluorescein with a yellow barrier filter is an important step in identifying many of these tissue changes, particularly as symptoms cannot be relied on as an alert mechanism. CLS

This article was prepared with financial support from Alcon.

For references, please visit www.clspectrum.com/references and click on document #237.

Jill Woods is a clinical research manager and senior clinical scientist at the Centre for Contact Lens Research (CCLR), University of Waterloo, Waterloo, Canada. She is also a consultant to Alcon. The CCLR has received research funding from Abbott Medical Optics, Advanced Vision Research, Alcon, Allergan, CooperVision, Essilor, Johnson & Johnson, OcuSense, and TearScience, among others.