Tear Film Osmolarity in Subjects with Acute Allergic Rhinoconjunctivitis

Patients and Methods

Patient recruitment. Forty-five subjects with acute allergic rhinoconjuctivitis were recruited in this study. An experienced allergist referred to us patients with ocular symptoms, who had never been treated by an ophthalmologist. Although acute allergic rhinoconjuctivitis has already been defined (8), we mention that we diagnosed the disease in people suffering from the following symptoms: nasal obstruction, watery nasal discharge, sneezing and itching, and conjunctival symptoms, including itching, injection and tearing. The inclusion criteria also involved the follow indexes: tear film breakup time (BUT) less than 5 seconds, Schirmer I test less than 5 mm, and positive corneal and conjunctival staining. Past medical history, including medications, medical conditions, ocular history, within the last 3 months was obtained.

The exclusion criteria comprised any evidence of acute or chronic infection, any inflammatory or allergic condition of the cornea and conjunctiva other than acute allergic rhinoconjuctivitis, incomplete lid closure, entropion, ectropion, nasolacrimal drainage obstruction, placement of punctal plugs or punctal cauterisation, history of ocular surgery within the past year, use of contact lenses during the previous month and use of other topical ocular medications or artificial tears within 2 hours of checking tear osmolarity. Moreover, the history of known collagen vascular disease, such as secondary Sjögren syndrome or positive serology of autoantibodies, was regarded as exclusion criteria. Subjects suffering from systemic diseases, such as diabetes mellitus and thyroid diseases, or receiving treatment, including antidepressants, diuretics, corticosteroids or immunomodulators, which could impact tear secretion or the ocular surface, were ruled out by the medical history.

Study design. This study was designed as a prospective study. All subjects included were treated for a run-in period of 7 days with one eye drop of saline six times a day. At the end of this period (time 0 of the study) the subjects were randomly divided into three groups and assigned to a treatment by personnel not involved with the subjects' examination. The number of the groups was determined according to the type of artificial tears that each patient received: Group A (Thera tears), Group B (Wet therapy) and Group C (Tears Naturale free). The eye drops were administered six times a day for 60 days and the subjects enrolled in the study underwent grading of subjective symptoms and clinical examination at baseline (time 0) and at the end of the treatment (after 60 days).

The parameters evaluated at baseline and at each follow up visit included the ocular surface disease index (OSDI; Allergan, Inc, Irvine, CA, USA), BUT, tear osmolarity test, Schirmer test I, fluorescein corneal and conjunctival staining. Tear osmolarity was measured first and Schirmer test was performed last, in order to minimize the effect of other examinations. The subjects were allowed to know the brand name of the eye drops they were using. They were asked to bring, at all visits, the used boxes of eye drops in order to control the compliance with the study protocol.

The study was conducted in the General Hospital of Athens G. Gennimatas in accordance to the tenets of the Declaration of Helsinki. The protocol used was approved by the ethics committee of the University Hospital. All patients agreed to participate in the study and gave written informed consent.

Study material. We used the following types of artificial tears: Thera tears (Akorn, Inc., Lake Forest, Illinois, USA), Wet therapy (Vita Research, Rome, Italy) and Tears Naturale free (Alcon, Inc., Fort Worth, Texas, USA). The characteristics of all drops are depicted in Table I. All artificial tears were preservative-free.

Symptoms. Symptoms of dry eye syndrome, such as burning, foreign body sensation, dryness, mucous discharge, itching and photophobia, were assessed with the ocular surface disease index (OSDI; Allergan, Inc, Irvine, CA, USA). The OSDI consists of 12 questions on symptoms within the past week and yields scores ranging from 0 (least severe) to 100 (most severe). A score of 12 is typically used as a cutoff for normal, 13-22 for mild dry eye, 23-32 for moderate dry eye, and ≥33 for severe dry eye (1, 2, 9).

Tear osmolarity. Tear osmolarity was measured in each eye with the TearLab® Osmolarity System (TearLab Corporation, San Diego, CA, USA). This new osmometer is a disposable ‘lab-on-a-chip’ system that requires <50 nl of tear fluid for analysis (3). A desktop instrument converts the electrical signals generated from the laboratory card into a quantitative measurement and displays the value on a screen. The system was stored in a temperature and humidity controlled environment, and these values were logged prior to each measurement of tear osmolarity. The system was calibrated at the beginning of each study day according to the manufacturer's instructions; the test cards used for each tear osmolarity measurement were from the same lot numbers as the test cards used to calibrate the machine each day.

Subjects were instructed not to rub their eyes for at least 10 minutes. Tear samples (50 nl each sample) were collected atraumatically from the lateral tear meniscus (near the lateral canthus) of the right eye and then the left eye. The tip of the TearLab device (Pen 1) was placed gently with care being taken not to induce reflex tearing. Normal tear osmolarity is equivalent to normal blood osmolarity, which ranges from 280-295 mOsm/L. A tear osmolarity value of 305 mOsm/l was used as the cutoff for mild dry eye and 316 mOsm/l was used as the cut-off for more severe dry eye disease (3, 4). All measurements were performed by the same investigator. Since inter-eye variability has been found to be associated with an increased severity of DED, the measurement from the eye with the higher osmolarity was used for data analysis.

BUT and Schirmer test. Fluorescein strip was wet with a drop-volume of non-preserved saline solution and the strip was touched to the inferior palpebral conjunctiva. Subjects were asked to blink several times. The investigator monitored the integrity of the tear film with a slit lamp and measured up to the time until one or more dry spots appeared in the precorneal tear film from the last blink.

A 5-minute Schirmer I test without topical anesthesia was performed to evaluate both basal tear secretion and reflex tearing. A Schirmer test I value of less than 10 mm in 5 minutes was considered abnormal (5).

Corneal staining. The degree of staining was measured for each of the five regions of the cornea: central, superior, temporal, nasal, and inferior. The degree of staining was evaluated using the National Eye Institute (NEI) method, for each of the five regions of the cornea (central, inferior, nasal, superior, and temporal) as follow: 1) grade 0 (normal); no staining, 2) grade 1 (mild); superficial stippling and micropunctate staining, 3) grade 2 (moderate); macropunctate staining with some coalescent areas; and 4) grade 3 (severe); numerous coalescent macropunctate areas and/or patches. Each of the five regions was graded on a scale from 0 to 3. The scores of the five areas were added to obtain a total score for each eye.

Conjunctival staining. The degree of staining was separately assessed for the three portions of the temporal conjunctiva and the three portions of the nasal conjunctiva on a scale from 0 to 3. The scores for each of the six areas were added to obtain a total score for each eye.

Statistical analysis. The statistical program IBM SPSS Statistics 22.0 was used for the data analysis. Descriptive analysis was carried out for age, OSDI scores, tear osmolarity, BUT and Schirmer I test values, as well as corneal and conjunctival staining scores. Non-parametric analysis Kolmogorov-Smirnov was used to check the normal distribution of the variables. The paired two-tailed t-test was utilized to calculate the differences in means of the measured variables between baseline and after the administration of artificial tears within each group. If the data failed the normality test, the non-parametric Wilcoxon matched-pairs signed-rank test was used. Independent samples Kruskal-Wallis tests were applied to identify the possible differences in means of the measured variables between the three groups (Mann-Whitney test was used when there was no indication of normal distribution either after Kolmogorov-Smirnov analysis or after Levene's test for e3quality of variances). Correlation technique, based on Spearman's coefficient, was performed to determine the relation among ocular indexes. A p-value less than 0.05 was considered to indicate statistical significance.