Research carried out by the Chang Gung Memorial Hospital in Keelung, Taiwan, found significant differences between men and women with regard to initial presentation symptoms of the dry eye syndrome (DED). Being female was one of the factors associated with a higher symptom severity score
DRY EYE DISEASE
Dry eye disease (DED) is a condition that affects 5 to 50% of adults worldwide. In Taiwan, where the study was conducted, 7.85% of the general population, and as many as 20.72% of patients over the age of 65 suffer from it.
Although, unlike other diseases, DED doesn’t cause vision loss, it nevertheless significantly affects the living conditions of patients. DED damages the ocular surface, causing irritation and visual disturbances that, in turn, affect daily activities such as driving or watching TV.
The absence of a universal and accurate test poses limitations to DED diagnostic capabilities. Ophthalmologists must rely on a variety of tools: objective signs, the symptoms described by the patient, questionnaires, and diagnostic tests.
THE TEAM OF RESEARCHERS AND THE CLINIC-BASED COHORT
The focus of the team of researchers from Taiwan – composed of Pei-Ting Lu, Chia-Yi Lee, and Chi-Chin Sun of the Department of Ophthalmology at the Chang Gung Memorial Hospital in Keelung – was the analysis of sex-based differences in DED initial presentation symptoms, and the presence of a potential connection between a patient’s surgical history and discordances between DED symptoms and signs.
The study included data from 1229 patients, mostly women (79.3%) with a mean age of approximately 56.7 years. The initial presenting symptoms were cross-sectionally and retrospectively collected, starting from the first check-up at the DED tertiary referral clinic at Chang Gung Memorial Hospital, during the period between 1 August 2011 and 31 July 2018.
METHODOLOGY
The actual presence of dry eye disease, in the context of this research, was defined on the basis of the following criteria: an OSDI (Ocular Surface Disease Index) value greater than
12, which had to be associated to a TBUT (Tear Breakup Time) of less than 5 seconds or a positive Corneal fluorescein staining (CFS).
The collected data included a general medical and ophthalmic history of the patient, as well as, the date when the DED diagnosis was made, and the manifestation of the first symptoms and signs.
The OSDI questionnaire, which was submitted at the time of the first examination, was used to quantify ocular surface symptoms, their frequency, and the influence they had on vision.
In addition to the TBUT and CFC criteria, Schirmer’s test and MGD (Meibomian Gland Dysfunction) analysis were included.
The results were converted into a severity score system and the overall mean value was calculated.
The data was cross-sectionally analysed, also using a multivariate linear regression model.
RESULTS
The most common symptoms reported in order of importance were dry eye (43.5%), blurred vision (24.2%), the sensation of a foreign body in the eye (18.1%), and lacerations.
No significant differences were found between men and women with regard to initial presenting symptoms.
Several factors, however, were found to be connected to a higher symptom severity score than sign severity score.
These factors include being female and previous cataract surgeries.
The differences between the two sexes are due to the following reasons:
1. women usually have a lower pain threshold,
2. hormonal changes are associated with changes in the ocular surface,
3. oestrogens, unlike androgens, counteract the adjoining tissues of the eye and stimulate inflammatory responses,
4. women suffer from other comorbidities more frequently than men,
5. women have less trouble reporting potential pain, for socio-cultural reasons.
There are multiple reasons why cataract surgery is associated with stronger symptoms:
1. surgical interventions of the ocular surface destroy the innervation organization of the corneal area,
2. the use of localised anaesthetics, exposure to the microscope light as well as irrigation of the cornea contribute to a lower density of goblet cells and decreased tearing,
3. inflammatory mediators released after corneal incision can damage corneal nerves.
Among the factors that are associated with a higher symptom severity score are also pterygium removal and correction of conjunctivochalasis.
Conversely, the study identified a number of factors that are associated with a lower symptom severity score than sign severity score, such as: older age (despite being among the main predictors of DED onset), the use of artificial tears and type 2 diabetes mellitus.
The age factor, however, is often nullified in the event of cataract surgery.
CONCLUSIONS
This study shows a number of limitations:
· first of all, it is a retrospective and cross-sectional study, therefore the outcome and results of the research are simultaneous,
· the OSDI questionnaire relies on the self-assessment of symptoms,
· the data has been collected starting from the time of the first check-up, but some patients had previously received treatments at other clinics,
· several key predictors, such as chronic pain syndrome, and environmental factors, such as patient profession, were not taken into account.
The study allowed the team to highlight a series of important predictors of the discordance between symptoms and signs of the dry eye syndrome, which should be taken into considerable account in ophthalmological practice. Further research is however essential to fully understand such discordance.