Evaluation of the Frequency of Ophthalmic Solution Application: Washout Effects of Topical Saline Application on Tear Components

Quantifying Sample Collection and Processing Impacts on Fiber-Based Tear Fluid Chemical Analysis

Purpose

Noninvasive analyses of tear fluid from humans and animal models in clinical and research settings most commonly use absorbent material for collection and processing. Still, the impact of these analytical techniques on tear chemical analyses remains largely unknown. The purpose of this study was to quantify the impacts of phenol red thread fiber-based tear sample collection and processing on the primary amine content.

Methods

Human tears were collected by placing the folded end of phenol red thread on the palpebral conjunctiva of the right eye for 20 seconds. The wetted thread was then processed using elution or extraction, and capillary electrophoresis with light-emitting diode-induced fluorescence detection was used for analysis and quantitation.

Results

Distinct processing methods impacted tear analysis differently. Primary amines adsorbed onto the thread partitioned in a chromatographic manner and thus any single portion of the wetted thread might not be representative of the whole sample. Quantitative assessment of five small molecule standards after on-thread processing showed significant overestimation of the actual concentration, with increased accuracy for larger volume samples. Yet collection of larger tear volumes introduced error in volume determination owing to evaporation and reduced small molecule separation resolution.

Conclusions

These results indicated that absorption-based tear fluid collection and processing significantly alter chemical content analysis, suggesting that the impacts of methods used should be regularly evaluated to standardize results drawn from different studies.

Translational Relevance

This study identifies potential inconsistencies and inaccuracies in tear analyses that are widespread across the published literature and clinical care.

Tear protein analysis in presumed congenital alacrima

Objectives

It is often hard to reach a definitive diagnosis of congenital alacrima because of the difficultly in proving the lack of lacrimal tissue. We report here the distinct tear protein profile in presumed congenital alacrima.

Patients and methods

A 13-year-old girl with presumed congenital alacrima and 15 healthy volunteers aged 23–35 years were included in this study. Tears were collected using Schirmer strips, and tear protein analyses were performed. Tear samples were collected from the patient with alacrima before and after surgical punctal occlusion of both the upper and lower puncta, and tear protein extract was fractionated using HPLC. Lactoferrin and albumin concentrations in the tears were separately determined using ELISA.

Results

The chromatogram in the patient greatly differed from that in normal subjects with low concentrations of secretory IgA, lipocalin-1, and lysozyme. ELISA results indicated that the tear fluid in the patient contained a high concentration of albumin but a minimal concentration of lactoferrin. Punctal occlusion improved the ocular surface findings, but major lacrimal protein concentrations remained low and tear albumin concentrations further increased.

Conclusion

The tear protein profile of a patient with presumed congenital alacrima greatly differed from that of normal subjects. Tear protein analysis may be useful in making a diagnosis of congenital alacrima and in assessing the efficacy and mechanism of punctal occlusion.

The effect of rebamipide ophthalmic suspension on ocular surface mucins in soft contact lens wearers

PURPOSE

To evaluate the changes in ocular surface mucins with 2%rebamipide ophthalmic suspension treatment in soft contact lens (SCL) wearers. Rebamipide suspension is a mucin secretagogue approved for the treatment of dry eye syndrome in Japan. In this study, the fluorescence intensity of wheat germ agglutinin conjugate of fluorescein (F-WGA) was used as a marker of membrane-associated mucins, and sialic acid concentration in tear fluids as a marker of secreted mucins.

METHODS

Thirty-two eyes of 16 SCL wearers with discomfort were treated with rebamipide suspension at a dose of one drop in each eye four times daily for two weeks. The parameters of clinical efficacy were tear break-up time, fluorescein staining scores for the cornea and conjunctiva, and Schirmer test values. Fluorescence intensities in the central cornea were measured by fluorophotometry after the application of 5% F-WGA solution. Tears collected by Schirmer test strips were analyzed by high-performance liquid chromatography, and the concentrations of sialic acid, total protein, and the four major tear proteins, namely secretory IgA, lactoferrin, lipocalin-1, and lysozyme were measured.

RESULTS

Significant increases in F-WGA fluorescence intensities (p < 0.005) were seen in the corneal surfaces. Sialic acid concentrations increased over time; however, the differences were not statistically significant. Except for a slight increase in kerato-conjunctival staining scores (p < 0.05) and secretory IgA (p < 0.05), no other significant differences were seen among clinical parameters or tear proteins.

CONCLUSIONS

Topical application of rebamipide suspension significantly increased F-WGA intensity, a marker of membrane-associated mucins in SCL wearers.

Diquafosol for Soft Contact Lens Dryness: Clinical Evaluation and Tear Analysis

PURPOSE

To evaluate the efficacy of topical application of 3% diquafosol tetrasodium solution for the treatment of soft contact lens (SCL) wearers with dryness. In addition to clinical tests and subjective symptoms, we assessed the fluorescence intensity of wheat germ agglutinin conjugate of fluorescein (F-WGA) used as a marker of membrane-associated mucins and sialic acid concentration in tear fluids as a marker of secreted mucins.

METHODS

Twelve SCL wearers with dryness symptoms were treated with diquafosol for 4 weeks. Clinical tests included the tear film break-up time (BUT), corneal and conjunctival fluorescein staining scores, and Schirmer values. Subjective symptoms were evaluated by the Dry Eye-Related Quality-of-Life Score (DEQS). Fluorescence intensities in the central cornea were measured by fluorophotometry at 5 minutes after a 5% F-WGA solution was applied to the eye. The tears collected by the Schirmer test strips were analyzed by high-performance liquid chromatography (HPLC), and the concentrations of sialic acid; total protein; and the four major tear proteins secretory IgA, lactoferrin, lipocalin-1, and lysozyme proteins were measured.

RESULTS

Comparing the results before and after diquafosol treatment, BUT (p < 0.01), kerato-conjunctival staining score (p < 0.05), corneal staining score (p < 0.05), and DEQS score (p < 0.01) showed statistically significant improvements. The F-WGA fluorescence intensities (p < 0.0001) significantly increased after treatment, whereas the concentrations of sialic acid and tear proteins remained unchanged.

CONCLUSIONS

Topical application of diquafosol solution to the SCL wearers with dryness improved biomarker of membrane-associated mucins, BUT, staining of cornea and conjunctiva, and subjective symptoms.

Influence of Ophthalmic Solutions on Tear Components

Tear fluids are a mixture of secretions derived from lacrimal glands, accessory lacrimal glands, conjunctiva, and meibomian glands. Compositional changes to tears occur in the normal state and during ocular surface disease, such as dry eye conditions. We have investigated compositional changes to tears after topical application of ophthalmic solutions, with regard to tear-specific proteins (secretory immunoglobulin A, lactoferrin, lipocalin-1, and lysozyme) and ocular surface mucin in normal and dry eye conditions using high-performance liquid chromatography. After application of saline solution (0.9% sodium chloride) in normal subjects, transient but significant decreases in all tear components were observed. The recovery of protein concentrations took up to 30 minutes and lasted longer when the saline solution was applied more frequently. When applying ophthalmic solutions, a balance between washout and dilutional effects should be considered in addition to the therapeutic effect. Investigation of the effect of diquafosol solution (3%) in normal subjects revealed a significant increase in sialic acid concentration, a marker of ocular mucin, at 5 minutes after application, whereas a significant decrease was observed with saline. This result indicates the accelerated secretion of mucin from ocular tissues induced by diquafosol. A clinical study to determine the efficacy of diquafosol in patients with dry eye revealed improvements in tear breakup time, keratoconjunctival staining scores, and Schirmer test score, accompanied by an increase in sialic acid concentration in tears. Investigating normal and dry eye conditions through tear analysis may clarify the pathophysiology of dry eye conditions and support the efficacy of treatments.

Diquafosol sodium ophthalmic solution for the treatment of dry eye: clinical evaluation and biochemical analysis of tear composition

PURPOSE

To evaluate the clinical efficacy of 3% diquafosol sodium ophthalmic solution for dry eye, and to analyze the concentration of tear proteins and mucin-like substances after the treatment.

METHODS

Fifty eyes of 25 patients with dry eye syndrome were prospectively enrolled. The patients were treated with diquafosol solution at a dose of 1 drop in each eye 6 times daily for 4 weeks. The parameters of clinical efficacy were tear osmolarity, tear breakup time (BUT), fluorescein staining scores for the cornea and conjunctiva, Schirmer test values, and subjective symptoms evaluated using the ocular surface disease index (OSDI). Tears collected with Schirmer test strips were analyzed by high-performance liquid chromatography, and the concentrations of the total protein and the 4 major tear proteins, namely, secretory IgA, lactoferrin, lipocalin-1, lysozyme, and N-acetyl-neuraminic acid (Neu5Ac), were measured. Neu5Ac is a major sialic acid, a marker of secretory mucins.

RESULTS

The BUT, keratoconjunctival staining scores, and Schirmer test values were improved with statistical significance after the treatment with diquafosol solution, while changes in the other parameters, including tear osmolarity, corneal staining scores, and OSDI scores were not significant. The Neu5Ac concentration was significantly increased, which was not accompanied by changes in tear proteins.

CONCLUSIONS

Topical application of diquafosol significantly improved the clinical parameters of the BUT, keratoconjunctival staining scores, and Schirmer test values and was accompanied by increased sialic acid content in the tears of patients with dry eye.

Diquafosol Tetrasodium Increases the Concentration of Mucin-like Substances in Tears of Healthy Human Subjects

PURPOSE

This study was undertaken to determine the effect of topical application of diquafosol tetrasodium on proteins and mucin-like substances from tears of clinically healthy subjects.

METHODS

Tears were collected from both the eyes of 10 healthy volunteers. Diquafosol tetrasodium solution (3%) was applied once to the right eye and 0.9% sodium chloride solution (saline) once to the left eye. Tear samples were collected by Schirmer test strips before application and 5, 15, 30 and 60 min after application. Sialic acid, a marker of mucin-like substances, and major tear proteins including secretory IgA, lactoferrin, lipocalin-1, and lysozyme were measured by high performance liquid chromatography.

RESULTS

Levels of total protein, sIgA and lysozyme were transiently decreased in both groups but returned to baseline levels within 15 min after application. The concentration of lactoferrin and lipocalin-1 did not change significantly in both groups. Sialic acid in tears was significantly decreased 5 min after saline application, but significantly increased 5 min after diquafosol application. No significant difference in sialic acid was seen after 15 min in both groups.

CONCLUSIONS

Topical application of saline and diquafosol resulted in transient decrease of tear proteins possibly due to wash out or dilution effects. In contrast, diquafosol application significantly increased sialic acid, although the effect was transient. This suggests diquafosol stimulates the secretion of mucins from ocular tissues of healthy human subjects.