Globally, there are more than 140 million contact lens wearers, 88% of which are soft lens users (Dumbleton et al, 2013; Nichols, 2016). Several studies have reported on contact lens dropout or discontinuation; rates have ranged between 12% to 51%, which is mostly due to contact lens discomfort (CLD) (Dumbleton et al, 2013; Pritchard et al, 1999; Weed et al, 1993; Richdale, et al, 2007). A study by Nichols and Sinnott (2006) has shown that approximately 50% of contact lens users report experiencing dry eye symptoms at least occasionally.
Dry eye and alterations of the tear film in contact lens wearers can lead to a reduction in functional visual acuity and in wear time as well as an increased risk of ocular surface desiccation, bacterial binding, and infection (Dumbleton et al, 2013). Many factors can cause dry eye. The most common cause of evaporative dry eye is meibomian gland dysfunction (MGD) (Schaumberg et al, 2011).
Meibomian glands are large sebaceous glands that produce the lipids that serve the tear film by retarding evaporation of the aqueous phase of tears (Knop et al, 2011). Dysfunction of the meibomian glands leads to altered lipid production, which subsequently results in increased tear evaporation, increased tear osmolarity, and dryness symptoms (King-Smith et al, 2008; Foulks, 2007).
In contact lens wearers, meibomian gland abnormality can lead to contact lens intolerance and discontinuation; however, the potential association between contact lens wear and meibomian gland changes is still not clear.
Some studies have found that contact lens wear may lead individuals to MGD and obstruction of the meibomian gland orifices (Henriquez and Korb, 1981; Arita et al, 2009; Machalińska et al, 2015). On the flip side, another study did not observe such an effect (Pucker et al, 2015). Thus, the purpose of this pilot study is to compare meibomian gland structural changes and dryness symptoms in soft contact lens wearers.
Convenience sampling garnered 30 daily wear soft contact lens users who visited a contact lens clinic of a tertiary eye hospital. All users who were enrolled in this Institutional Review Board-approved study had a history of at least one year of soft contact lens wear without any ocular or systemic illness, and they had been wearing lenses for at least five days per week. Only the right eyes of all subjects were included in the study, but measurements were recorded for both eyes.
A detailed contact lens history was recorded, followed by the administration of the Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire (Henriquez and Korb, 1981). SPEED questionnaire responses were graded based the following scale: a score of 0 indicated no symptoms, 1 to 9 indicated mild to moderate symptoms, and > 10 indicated severe dry eye symptoms.
After obtaining informed consent from the study subjects, meibomian gland images were captured using a Topcon SL-D701 digital slit lamp (with a DC-4 digital camera) non-contact meibography system after everting the upper eye lid. The ratio of the meibomian gland loss (MGL) area to the total area of the glands (a.k.a., MGL percentage) was calculated with ImageJ, an open source image processing program designed for scientific multidimensional images (Figure 1). Subsequently, the relative meiboscore was classified by applying a four-grade scale (Arita et al, 2008) (Table 1). Data analysis was done using Microsoft Excel and IBM SPSS 20.0 software. The Pearson correlation was used to calculate the r value between the parameters. A p value < 0.05 was considered statistically significant.
|GRADE||LOSS OF THE GLAND|
|Grade 0||No loss of the meibomian glands|
|Grade 1||Area loss was less than one-third of the total meibomian gland area (< 33%)|
|Grade 2||Area loss was between one-third and two-thirds (33% to 66%)|
|Grade 3||Area loss was more than two-thirds (> 66%)|
Of the 30 subjects recruited by convenient sampling, 12 wore silicone hydrogel lenses, and 18 wore hydrogel lenses. The mean age of the subjects was 23.83 ± 3.90 years, and there were 24 females. The mean duration of lens wear was 5.03 ± 3.89 years, and the mean lens-wearing hours per day was 9.7 ± 2.9 hours. The mean meiboscore in silicone hydrogel lens wearers was 30.62 ± 8.44%; in hydrogel lens wearers, it was 25.51 ± 5.75%.
The median grade of MGL was grade 1 (i.e., < 33%) for an average of five years of lens wear. In addition, the MGL grade ranged between grade 1 and grade 2. There were six subjects with a grade 0 meiboscore, 20 subjects with a grade 1 meiboscore, and four subjects with a grade 2 meiboscore.
The median dry eye symptoms score (SPEED) was 5.00 (interquartile range=5). Only one subject reported with a severe symptoms score (14), 25 subjects had mild symptoms scores (1 to 9), and four subjects had a symptom score of 0.
Correlation between meiboscore and symptoms score (SPEED) showed a weak positive correlation (r=0.037, p=0.848). Correlation between the duration of time that contact lenses were worn in years and meiboscore also showed weak positive correlation (r=0.014, p=0.942).
This study used a non-contact meibography technique to image the meibomian gland loss associated with soft contact lens users in a pilot group of subjects who reported to a tertiary eyecare hospital. Apart from meibography imaging, subjective dryness and discomfort ratings associated with contact lens wear were also analyzed using the SPEED questionnaire.
Meiboscore in Soft Contact Lens Wearers Meiboscore grading ranged between grade 1 and grade 2 in the current study, and most of the subjects had grade 1 MGL (i.e., < 33 %). Similarly, Ong et al (1990) had examined the effect of lens wear on meibomian glands and found that there was no significant difference in the prevalence of MGD between contact lens wearers and non-wearers.
The mean meiboscore was higher in silicone hydrogel contact lens wearers than in hydrogel contact lens wearers in this study. The possible reasons could be: 1) because silicone hydrogel lenses have a greater modulus of elasticity; or 2) due to the mechanical interaction of the lens with the eyelid post blink. This echoes Arita et al (2009), who found no significant difference in meiboscore between GP contact lens wear and hydrogel contact lens wear. They also concluded that loss of meibomian glands depends on the duration of contact lens wear and not on the contact lens materials.
Symptom Score and Meiboscore Of the study subjects, 25 reported mild symptoms. One subject had a severe dry eye symptom score of 14, but surprisingly, the relative meiboscore of that same subject was < 33% (grade 1) (Figure 2). Arita et al (2009) had previously evaluated the clinical findings associated with changes in meibomian glands in contact lens wearers and non-wearers. They found that contact lens wearers had significantly greater MGL compared to non-contact lens wearers. But, in recent studies (Machalińska et al, 2015; Pucker et al, 2015), no significant associations have been found between changes in meibomian glands and contact lens wear.
This current study also showed no significant difference between the subjective ratings of dryness symptoms and MGL in contact lens wearers. But, these results are contradictory to a few studies (Henriquez and Korb, 1981; Ong et al, 1990) in which meibomian gland orifice obstruction was noted more in contact lens wearers. And, another study by Nichols and Sinnott (2006) reported no significant structural changes in the meibomian glands of contact lens wearers reporting dry eye compared to contact lens wearers without dry eye symptoms.
Contact lens wearers in this study (mean age: 23.8 years) had an average meiboscore of 0.93, which is similar to that observed in the 20 to 29 years age group from the normal population as reported in Arita et al (2008). This interestingly seems to be normal among our study subjects who had an average duration of five years of previous lens wear. Similarly, there was no statistically significant difference between the duration of contact lens wear and prevalence of MGL in our study. However, previous studies showed inconsistent results. For instance, Arita et al (2009) reported an increase in MGL with an increase in the number of years of contact lens wear, and Pucker et al (2015) reported no association between the duration of contact lens use and amount of MGL.
As this was a pilot study, the exact associations of subjective symptoms with clinical findings were not identified and may require a larger sample with a control group. Further study with correlation of symptoms, SPEED questionnaire, and MGL in a controlled population is currently being carried out. CLS
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