Article

THE OCULAR SURFACE AND LENS COMFORT

A pilot study on the correlation of ocular comfort score and anterior segment grading in soft contact lens wearers.

Contact lenses (CLs) are widely used for optical, occupational, and cosmetic purposes. Today, there are around 140 million contact lens users, with a dropout rate of 16%; the primary reason reported for dropout is dryness and discomfort (Rumpakis, 2010; Evans et al, 2008; Young et al, 2002; Richdale et al, 2007). Studies show a dropout rate of approximately 20% every year (Weed et al, 1993; Pritchard et al, 1999; Young et al, 2002; Richdale et al, 2007). Even though advanced lens materials such as silicone hydrogels were introduced as an answer to hypoxic complications, CL dropout rates remained as high as 30% (Rumpakis, 2010; Evans et al, 2008; Young et al, 2002). The Tear Film and Ocular Surface Society (TFOS) concluded that discomfort was the primary factor for contact lens dropout. In its Workshop on Contact Lens Discomfort report, TFOS stated that “such discomfort may be the leading cause for patient dissatisfaction, and discontinuation of CL wear throughout the world” (Nichols et al, 2013).

The TFOS report also stated that CL discomfort is defined as “a condition characterized by episodic or persistent adverse ocular sensations related to lens wear, either with or without visual disturbance, resulting from reduced compatibility between the contact lens and the ocular environment, which can lead to decreased wearing time and discontinuation of contact lens wear” (Nichols et al, 2013).

Other common reasons for CL dropout were the inconvenience of handling the lenses, ocular hyperemia, overnight wear, dryness and unsatisfactory vision especially in the presbyopic age group, and finally, cost factors (Fonn et al, 1999). The combination of different CLs with lens care solutions and factors such as tear breakup time and high tear osmolarity are also associated with discomfort (de la Jara et al, 2015; Nichols and Sinnott, 2006).

Symptomatic CL wearers are classified as those who have an increase in subjective dryness ratings and a decrease in comfort rating over time, whereas asymptomatic wearers are those whose ratings remain relatively constant (Fonn et al, 1999). Previous studies indicate that symptomatic CL wearers had more lipocalin, increased lipases, and degraded lipids in their tears as compared to asymptomatic CL wearers (Glasson et al, 2002). Also, tear volume and tear film stability were found to be reduced in intolerant CL wearers compared with tolerant CL wearers (Glasson et al, 2003). It was therefore concluded that symptoms and subjective clinical measurement are predictive to sort out symptomatic subjects from asymptomatic subjects. Thus, the aim of this study is to correlate the ocular comfort score and clinical measurements of anterior segment grading in symptomatic and asymptomatic CL wearers.

METHODS

Data were gathered prospectively from 30 habitual soft CL wearers who visited the contact lens clinic of a tertiary eye hospital. Subjects included in the study had at least one year of lens wear experience, were between 18 to 40 years old, reported vision of 6/9 or better, and had no ocular or systemic abnormalities. The study was approved by an Institutional Review Board, and informed consent was obtained from the study subjects.

Anterior segment evaluation was performed using the 0 to 4 point Efron Grading Scale. The “comfort” rating was scored by verbally asking questions about vision, comfort, dryness, and redness (Santodomingo-Rubido et al, 2010). Comfort scoring was based on visual analog scales from 0 (very poor) to 100 (excellent) for vision and comfort; dryness and redness were scored from 0 (none) to 100 (severe) (Dumbleton et al, 2008).

Subjects who reported vision and comfort ≥ 80 and dryness and redness ≤ 20 were grouped as asymptomatic wearers. Similarly, those reporting vision and comfort ≤ 80 and dryness and redness ≥ 20 were grouped as symptomatic wearers.

Data analysis was performed using Microsoft Excel 2007 and IBM SPSS 20.0 software. Pearson correlation was used to calculate the r value between parameters, and Wilcoxon signed-rank test was used to compare the significance of comfort ratings between the groups. P-values of < 0.05 were considered as statistically significant.

RESULTS

Of the 30 subjects, seven were male and 23 were female. The mean age of the subjects was 24 ± 4.3 years. The mean wearing time of the lens per day was 9.7 ± 2.9 hours, and the mean duration of lens wear was 4.7 ± 4.5 years. No correlation was found between papillae and comfort rating (r = 0.15, p = 0.42), papillae and redness rating (r = 0.18, p = 0.15), nor papillae and dryness rating (r = –0.18 p = 0.88). No correlation was found between dryness rating and blepharitis (r = 0.33, p = 0.86), dryness rating and meibomitis (r = 0.02, p = 0.99), nor years of lens wear and comfort rating (r = –0.18, p = 0.32).

There was statistically significant but low correlation found between years of lens wear and dryness rating (r = 0.37, p = 0.043). No correlation was found between average hours of lens wear per day and dryness (r = –0.06, p = 0.96) or comfort (r = 0.055, p = 0.67) ratings. The mean wearing time per day in symptomatic subjects was 9.7 ± 2.8 hours and in asymptomatic subjects was 9.6 ± 3.0 hours. The maximum and minimum scores were: comfort (100, 70), dryness (50, 0), and redness (50, 0) (Figure 1). A statistically significant difference was noted for the comfort (p = 0.001), dryness (p = 0.002), and redness (p = 0.009) scores between symptomatic and asymptomatic subjects.

Figure 1. A Box and Whisker plot comparing the subjective ratings between symptomatic and asymptomatic subjects.

DISCUSSION

Evaluation of the anterior segment and of ocular comfort by simply recording the presence of ocular symptoms revealed minimal differences between the symptomatic and asymptomatic CL wearers. During the study, six patients reported that they had previously discontinued their contact lens wear for two to three years due to ocular dryness, irritation, and fatigue.

As stated earlier, many studies have shown that discomfort and dryness are the primary reasons for discontinuation of CL wear. Dryness and discomfort could result from change in the ocular surface due to meibomitis, lid roughness, and blepharitis. In this current study, we could find no significant correlation between the subjective rating of comfort, vision, dryness, and redness in relationship to the anterior segment grading of blepharitis, meibomitis, and lid roughness. In addition, no significant correlation was found between a subject’s age when compared with dryness and comfort score. This shows that an age of younger than 40 years old is not an influencing factor for a patient’s subjective dryness and comfort rating.

This pilot study showed a positive correlation between the number of years of lens wear and dryness; on a related note, Arita et al (2009) found that a decrease in functional meibomian glands was proportional to the duration of lens wear in years, which contributed to dry eyes in CL wearers. Another study showed that intolerant CL wearers had reduced tear production that precluded the use of contact lenses (Glasson et al, 2003). Other factors that are responsible for dryness and discomfort during lens wear include loss of corneal sensitivity, increased tear osmolarity, pre-lens tear film thinning due to meibomian gland dysfunction, high-water-content contact lenses, and shortened blink rate (Nichols et al, 2013).

No correlation was noted between average wearing hours of the lens per day and dryness/comfort ratings, which was evident in the fact that the average lens wearing hours were almost equal in both symptomatic and asymptomatic subjects from this pilot study. CL materials with poor wettability (Thai et al, 2002; Guillon and Guillon, 1989) and higher water content (Nichols et al, 2006; Efron and Brennan, 1988) are linked with symptoms of dry eye. The majority of symptomatic subjects in this study were using hydrogel soft CLs (Figure 2).

Figure 2. The type of lens wearer among symptomatic and asymptomatic subjects.

Hydrogel CL wearers experience a low level of comfort due to the amount of dehydration (Fonn et al, 1999) that results from high-water-content lens material characteristics, lens design, and/or lens overwear. Surprisingly, both in the symptomatic and asymptomatic groups, a higher number of hydrogel lens wearers was noted, which is inconclusive of comfortable CL wear among the pilot group of subjects.

Although there were an equal proportion of subjects in both the symptomatic and asymptomatic groups, the median comfort and dryness score was better in asymptomatic (92, 10) than in symptomatic (77, 45) subjects. The maximum grade noted in symptomatic groups was grade 3 to 2 for papillae and grade 2 for conjunctival redness and meibomitis; in the asymptomatic group, the maximum was grade 2 for papillae while other anterior segment parameters were noted to be grade 1. Therefore, we concluded that subjects who report to the clinic with grade 2 complaints have the potential to become symptomatic CL wearers and need regular follow-up visits to prevent them from experiencing unsuccessful CL wear or dropout.

CONCLUSION

A minimal but significant difference in subjective scoring of comfort and clinical findings of the anterior segment in soft CL wearers was noted from the current pilot study. As this study was conducted in a small group of subjects, a larger sample size is required to clearly understand the relationship between comfort score and anterior segment grading with different lens materials and modalities. CLS

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