Symptoms Among CL and n-CL Wearers and VDT
Daily use of VDT was reported by 98.5% of people answering the questionnaire. Of those included in the statistical analysis, 49.5% use CRT displays, 43.8% use TFT displays, and 6.7% use both of them, with different daily exposure profiles as observed in Fig. 3. When compared with CRT, the proportion of people using TFT displays increases as the number of hours of daily use increases. Although the number of CRT displays is higher for those using them for <3 h/day, TFT displays are more frequent for those using them more than 3 h/day, particularly for the more intensive users (>6 h/day).
Figures 4a and 4b depict the pattern of symptoms presentation in CL and n-CL wear groups as a function of the daily exposure to VDTs. Comparative prevalence of symptoms among different VDTs users showed that scratchiness was significantly more frequent in CL wearers using both types of terminals for more than 3 h.
In the n-CL group, the symptoms were more prevalent as the number of hours spent working with computers increased. Those trends were statistically significant for “itching”, “excessive tearing,” and “scratchiness.” On the other hand, in the CL group, the prevalence of symptoms increased in subjects using VDT 3 to 6 h a day, but not in the group using VDTs 6 to 9 h a day. For those CL wearers using VDTs for <3 h a day the “burning” sensation was significantly lower than for those using them for 3 to 6 h (p = 0.016, χ2) and for those CL wearers using VDTs 3 to 6 h a day “scratchiness” was significantly higher (p = 0.048, χ2).
In general, the number of hours using VDTs did not affect the pattern of appearance of the symptoms, except for the response “end of the day” that presented statistically significant differences with increasing hours for n-CL group (p = 0.017, χ2). For those using VDTs for 3 to 6 h a day, the percentage of patients reporting symptoms at the “end of day” was significantly higher in the CL group (p = 0.006, χ2). This behavior was also observed for those CL wearers using VDTs for 6 to 9 h a day (p = 0.002, χ2).
Overall, the prevalence of most symptoms is more frequent in CL than n-CL wearers as seen in Figures 4a and 4b. A statistical comparison between n-CL and CL wearers has showed that “red eye” (p = 0.040, χ2) and “burning sensation” (p = 0.005, χ2) are significantly more frequent in CL wearers than n-CL wearers using VDTs <3 h/day; for those using VDTs 3 to 6 h/day scratchiness was significantly more prevalent in CL than n-CL wearers (p = 0.008, χ2).
Symptoms Among CL and n-CL Wearers and Indoor Environment Conditions (AC and HU)
Among those working/studying in AC and HU environments, the prevalence of symptoms increased in CL wearers compared to n-CL wearers except for the burning sensation (Fig. 5). Scratchiness was the only symptom with a significantly higher prevalence among CL than n-CL wearers using AC (p < 0.006, χ2) and HU (p < 0.005, χ2).
Ocular dryness and related symptoms continue to be the main complaint among CL wearers and it is believed that this is why CL wearers discontinue their use18 and opt for other vision correction strategies such as refractive surgery.19 Discomfort was indicated as the main reason by 51% of patients that discontinued CL wear in the UK.7
In this study, we have identified a higher prevalence of certain symptoms potentially associated with changes to the ocular surface in the CL wear population. Those who “often” reported symptoms increased significantly in the CL wearing group (24%) compared to n-CL wearers (13%). This is consistent with the results presented by Fonn et al., who described an almost linear decrease in patient comfort with different types of hydrogel and silicone hydrogel CL during a 7-h period among a group of symptomatic CL wearers.20 The level of scratchiness was the most significant difference between CL and n-CL wearers. Also, symptoms are more likely reported at the end of the day; 53.5% of CL wearers reported symptoms later in the day, whereas only 32% of n-CL wearers reported this.
The main reasons for the presence of these symptoms may be found in the tear stability, or lack of it, over the CL material, which can be adversely affected by environmental conditions of air temperature (AT) and relative humidity (RH).21–23 It is generally accepted that prelens tear stability is significantly affected by low humidity environments. In a recent study, Maruyama et al.12 have concluded that no statistically significant differences in tear volume was detected under different AT (10 to 35°) and RH (10 to 50%) conditions. However, they found that although noninvasive tear break-up time was independent of the environmental conditions without a CL in place, it decreased significantly as the air became dryer and colder for high and low water content SCL. These findings were associated with an increase of dryness complaints, particularly in high water content SCL.12 Nichols et al. have recently described similarities between the thinning of the prelens and precorneal tear film involving evaporation, dewetting, and pressure-gradient flows.24 However, the thinning process was more rapid over the CL material and the authors related more rapid thinning to dewetting processes. This could explain the higher prevalence of symptoms among CL wearers, particularly at the end of the day when the CL surface wettability could be more seriously affected.
For the population in this study, the use of heating devices in the work place might enhance ocular symptoms, which was not the case for those using air conditioner units that seemed to present a weaker correlation with the raising of ocular symptoms.
We noticed that working with VDTs can also influence the frequency of symptoms, particularly for those using TFT displays. However, this was probably related to a more intensive use of these displays rather than to the nature of the VDT. Indeed, for this population, the daily use of VDT was significantly higher than that reported by Begley et al. for the general population.2 Working with computers is a relevant matter of concern when fitting SCL to patients with the VDT exposure pattern reported in the present study. The fact that the most intensive VDT users do not present any severe symptoms suggests that a limited number of hours (perhaps between 3 and 6 h of computer use) might become irritating for CL wearers, and that above that number there is no increased impact on the wearer. However, more specific studies should be carried out to confirm this hypothesis.
The proportion of CL wearers reporting symptoms at the end of the day is almost twice as large compared to the n-CL group. In a recent study, Begley et al. have shown that for all symptoms under study, Sjögren’s syndrome (SS) and non-Sjögren’s syndrome keratoconjunctivitis sicca (non-SS KCS) groups presented an increase in the number of subjects who reported moderate to aggravated symptoms in the evening. For example, 67% of subjects with SS and 32% of subjects with non-SS KCS reported moderate to severe discomfort in the morning vs. 90% in the SS group and 60% in the non-SS KCS group in the evening.17 In the present study, almost no subject reported symptoms early in the day. This suggests that the pattern of appearance of symptoms (morning vs. evening) could be important to differentiate between pathological and marginal CL-related symptoms.
Furthermore, a recent study has shown that clinicians often underestimate the severity of dry eye conditions, particularly as far as older women are concerned.1,25 In the authors’ opinion although it is not possible to evaluate a general population directly, this suggests that CL wearers are at risk of developing symptoms who cannot be correctly managed might face a risk of CL intolerance in the future, if the clinicians rely only on clinical signs of dry eye to change the fitting/wearing strategy. However, to date, no standard tool has been provided for a proper subjective evaluation of CL related symptoms. Meanwhile, direct questions must be asked to patients wearing CL about their eye sensations and the way that these present themselves. Scratchiness at the end of the day appears to be key points to detect subtle problems in an early stage. This fits with the conclusions drawn in a recent study.14 Our study shows that this is even more important for females, for intensive VDT users, and for subjects who work in indoor heated environments. Strategies such as more frequent lens replacement, more intense cleaning, and a reduced wear schedule should be adopted earlier to maintain comfortable and safe CL wear.
In general terms, our results suggest that those CL wearers, (particularly young women) that use of VDT for long hours in air conditioned rooms, run a higher risk of presenting certain symptoms (mainly scratchiness) at the end of the day. If not solved, such a condition could lead to the discontinuation of CL wear in the medium term. The “at risk” group corresponds to the prototype of the most common contact lens wearers in Portugal to be fitted for the first time or refitted. Within this specific populations, 66.5% are female and aged 28 ± 10 (whole sample); 20% of the patients who are refitted describe frequent symptoms vs. 10% of first fits, and 30% describe symptoms in the evening against 16% in the first fitting group. These differences are statistically significant at p = 0.05 and p = 0.01 levels, respectively.26
Current demographic and socioeconomic trends along with the current CL wearer profile could lead to an increasing proportion of CL-related symptoms among the world population of CL wearers. Despite significant improvements in CL materials and palliative treatments that could reduce these problems in the future, clinicians should consider new standards of subjective evaluation. This includes the prefitting investigation of risk factors that can potentially affect CL tolerance in the medium and long terms, and a proper follow-up schedule with direct questions that allow early detection of symptoms that can suggest changes in the CL wearing strategy.
This study was partially supported by a grant from the Science and Technology Foundation (FCT) - Ministry of Science and Superior Education (MCES) under contract 8281/2002 from the European Social Funding granted to JMG-M.
None of the authors has a commercial or financial interest in the instruments or materials used in the study.
The authors wish to thank the assistance of AP Almeida, AP Costa, A Fernandes, A Teixeira, C Marques, C Pinho and J Matos for their assistance in data acquisition, and Dr. Ana Costa from the program of Support to the Edition of Scientific Papers at the University of Minho for help with English editing of the manuscript.
José Manuel González-Méijome
Department of Physics (Optometry)
Campus de Gualtar, University of Minho
4710-057 Braga, Portugal
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Please, answer the following questions placing ⊠ where appropriate.
- Male □ Female □ Age □ Occupation □
- Do you wear contact lenses?
No, I do not wear contact lenses □
Yes □ Soft /Hydrogel □ Rigid and Rigid Gas Permeable □ For how long? □ years/months
1. Have you ever used drops for your eyes?
No □ Yes □ Which kind: Drugs □ Artificial Tears/Saline □
2. Which kind of symptoms/signs did you feel after a normal day working/studying?
Red eye □ Itching □ Excessive tearing □ Scratchiness □ Burning □
3. How frequently you feel this/these sign(s)/symptom(s)?
Never □ Sometimes □ Frequently □ Constantly □
There is a specific part of the day when you feel them more?
Early in the day □ End of the day □
4. Do you use to work/study in closed rooms with some of the following environments?
Air conditioned □ Heating units □ Dust □ Chemicals □
5. Do you use frequently computers at your working/studying place?
Yes □ No □
6. Do you feel some irritation after having using a computer for a prolonged period?
Yes □ No □ I do not use computers □
7. Which kind of screen use your computer?
Conventional (CRT or TV-like) □ Flat screen (TFT, LCD or laptop-like) □
This questionnaire is anonymous. By answering this questionnaire you agree that this data would be used with scientific and teaching purposes by staff of the Department of Optometry at the University of Minho.
Keywords:© 2007 American Academy of Optometry
adverse environment; ocular symptoms; soft CL; complaints; marginal dry eye