Randomized Controlled Study to Investigate the Effect of Topical Diquafosol Tetrasodium on Corneal Sensitivity in Short Tear Break-Up Time Dry Eye

Evaluating the efficacy and safety of therapeutic interventions for corneal neuropathy: A systematic review

Corneal neuropathy involves corneal nerve damage that disrupts ocular surface integrity, negatively impacting quality-of-life from pain and impaired vision. Any ocular or systemic condition that damages the trigeminal nerve can lead to corneal neuropathy. However, the condition currently does not have standardized diagnostic criteria or treatment protocols. The primary aim of this systematic review was to evaluate the efficacy and safety of interventions for treating corneal neuropathy. Randomized controlled trials (RCTs) that investigated corneal neuropathy treatments were eligible if the intervention(s) was compared to a placebo or active comparator. Comprehensive searches were conducted in Ovid MEDLINE, Ovid Embase and clinical trial registries from inception to July 2022. The Cochrane Risk-of-Bias 2 tool was used to assess study methodological quality. Certainty of the body of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Overall, 20 RCTs were included. Evaluated interventions comprised regenerative therapies (n = 6 studies), dietary supplements (n = 4), anti-glycemic agents (n = 3), combination therapy (n = 3), supportive therapies (n = 2) and systemic pain pharmacotherapies (n = 2). Nine RCTs were judged at high risk of bias for most outcomes. Definitions for corneal neuropathy in the populations varied substantially across studies, consistent with lack of consensus on diagnostic criteria. A diverse range of outcomes were quantified, likely reflecting absence of an agreed core outcome set. There was insufficient evidence to draw definitive conclusions on the efficacy or safety of any intervention. There was low or very low certainty evidence for several neuroregenerative agents and dietary supplements for improving corneal nerve fiber length in corneal neuropathy due to dry eye disease and diabetes. Low or very low certainty evidence was found for neuroregenerative therapies and dietary supplements not altering corneal immune cell density. This review identifies a need to standardize the clinical definition of corneal neuropathy and define a minimum set of core outcome measures. Together, this will provide a foundation for improved phenotyping of clinical populations in studies, and improve the capacity to synthesize data to inform evidence-based care. Protocol registration: PROSPERO ID: CRD42022348475.

Effects of Diquafosol Sodium Ophthalmic Solution on Tear Film Matrix Metallopeptidase-9 and Corneal Nerve Density in Patients with Type 2 Diabetic Dry Eye

Purpose: Diabetes mellitus has been associated with increased dry eye disease (DED) and exacerbates DED's pathology. This preliminary short-term study aimed to evaluate the effects of 3% Diquafosol Sodium ophthalmic solution (DQS) on ocular surface inflammation and corneal nerve density in diabetic dry eye (DDE) patients. Methods: In this perspective, participants used 1 drop of 3% DQS (Diquas; Santen Pharmaceutical Co., Ltd., Osaka, Japan) 6 times daily for 8 weeks. Non-invasive tear breakup time (NITBUT), tear film lipid layer (TFLL), conjunctival hyperemia [redness score (RS)], corneoconjunctival staining (CFS), corneal sensitivity (CS), Meibomian gland quality (MGQ) and Meibomian gland expressibility (MGEx), corneal nerve fiber density (CNFD), and Standard Patient Evaluation Eye Dryness (SPEED) questionnaire were assessed at baseline, at weeks 4, and up to 8 weeks. Matrix metalloproteinase-9 (MMP-9) of tear samples was measured at baseline and weeks 8. Results: The mean age was 61.27 ± 11.68 years. At baseline NITBUT = 5.89 ± 2.81 s, tear meniscus height = 0.17 ± 0.05 mm, TFLL = 2.74 ± 0.51, CFS = 4.35 ± 0.68, CS = 53.83 ± 9.63 mm, MMP-9 = 49.10 ± 10.42 ng/mL, RS = 1.65 ± 0.44, MGEx = 1.85 ± 0.72, MGQ = 2.65 ± 0.50, CNFD = 20.36 ± 8.20 no./mm2, and SPEED = 12.62 ± 3.91. At week 4, significant improvements were found in all parameters except RS (1.59 ± 0.46, P = 0.172) and CNFD (21.46 ± 8.41, P = 0.163). Finally, at week 8, all parameters had significant improvements. Conclusion: Preliminary short-term findings suggest that treatment of DDE patients with DQS was found to be safe and efficacious in improving dry eye parameters. In addition, inflammatory marker and corneal nerve density were significantly improved. This study was registered with ClinicalTrials.gov (NCT05193331).

A protocol for a single center, randomized, controlled trial comparing the clinical efficacy of 3% diquafosol and 0.1% hyaluronic acid in diabetic patients with dry eye disease

BACKGROUND

The global prevalence of diabetes mellitus (DM) continues to rise and 70% of diabetic individuals have dry eye disease (DED) that leads to subsequent abnormalities of the corneal epithelium, corneal nerves, tear film, or corneal endothelium. In addition, persons with diabetes produce fewer tear secretions than healthy individuals. While several anti-inflammatory drug-based therapies for dry eye in diabetic individuals are currently being administered, their efficacy has not been studied in detail. Therefore, the aim of this study was to compare the effectiveness of 3% diquafosol (DQS) vs 0.1% hyaluronic acid (HA) eye drops in diabetic dry eye patients.

METHODS

This triple-blind randomized, control trial will include 202 diabetic-related DED and will be assigned to DQS (n = 101) and HA (n = 101) one drop, six times per day for 8 weeks. Tear film lipid layer, non-invasive breakup time, conjunctivocorneal staining score, corneal sensitivity, tear MMP-9 levels, meibomian gland expression and quality, tear meniscus height, corneal nerves, immune/inflammatory cell change, conjunctival hyperemia, and ocular surface disease index questionnaire score will be assessed and compared at baseline, week 4, and week 8.

DISCUSSION

This study will be a standardized, scientific, clinical trial designed to evaluate the therapeutic effects and safety of DQS and HA for diabetic dry eye treatment.

TRIAL REGISTRATION

ClinicalTrials.govNCT05682547. Registered on December 05, 2022.

Update on Dry Eye Disease Treatment: Evidence From Randomized Controlled Trials

ABSTRACT

Although the ultimate goal of dry eye disease (DED) management is to restore the ocular surface and tear film homeostasis and address any accompanying symptoms, addressing this is not an easy task. Despite the wide range of current treatment modalities targeting multiple aspects of DED, the available DED management literature is quite heterogeneous, rendering evaluation or comparison of treatment outcomes hard or almost impossible. There is still a shortage of well-designed, large-scale, nonsponsored, randomized, controlled trials (RCTs) evaluating long-term safety and efficacy of many targeted therapies individually or used in combination, in the treatment of identified subgroups of patients with DED. This review focuses on the treatment modalities in DED management and aims to reveal the current evidence available as deduced from the outcomes of RCTs.

Short-term application of diquafosol ophthalmic solution benefits children with dry eye wearing orthokeratology lens

Purpose

This aim of this study was to evaluate the effect of 3% Diquafosol Ophthalmic Solution (DQS) on children with dry eye from wearing overnight orthokeratology (OrthoK) lenses.

Methods

Myopic children aged 8-18 years with dry eye syndrome were enrolled in this prospective observational study, and they were grouped according to their OrthoK treatment history for at least 1 year. All participants received DQS 4 times per day for 1 month. The following indicators were measured at baseline 1 month after treatment: the Dry Eye Questionnaire-5 (DEQ-5), non-invasive tear meniscus height (TMH), non-invasive tear film break-up time (first and average, NIBUT-F and NIBUT-A), meibomian gland score (MG score), conjunctival hyperemia redness score (R-scan), and blink pattern analysis.

Results

A total of 104 participants (189 eyes) including 40 OrthoK wearers (72 eyes) and 64 Orthok candidates (117 eyes) completed the study. Of all, after DQS treatment for 1 month, DEQ-5 scores reduced from 5.54 ± 3.25 to 3.85 ± 2.98 (t = -3.36, p = 0.00). TMH increased from 0.20 ± 0.05 mm to 0.21 ± 0.05 mm (t = 2.59, p = 0.01), NIBUT-F and NIBUT-A were prolonged from 6.67 ± 4.71 s to 10.32 ± 6.19 s and from 8.86 ± 5.25 s to 13.30 ± 6.03 s (all p = 0.00), respectively. R-scan decreased from 0.69 ± 0.28 to 0.50 ± 0.25 (t = -9.01, p = 0.00). Upper MG scores decreased from 1.04 ± 0.32 to 0.97 ± 0.36 (t = -2.14, p = 0.03). Lower MG scores, partial blink rate, partial blinks, and total blinks did not change significantly. Both break-up time (BUT) and R-scan improved significantly after DQS treatment for 1 month (all p = 0.00) in OrthoK candidates and OrthoK wearers. Among the OrthoK wearers, TMH and dry eye symptoms increased significantly (all p = 0.00) but did not increase in OrthoK candidates (p > 0.05). There were no adverse events related to DQS.

Conclusion

Diquafosol Ophthalmic Solution was effective for children wearing overnight orthokeratology in relieving dry eye symptoms and improving ocular surface parameters, which may help improve children's OrthoK wearing tolerance and compliance.

Tear Fluid Biomarkers and Quality of Life in People with Type 2 Diabetes and Dry Eye Disease

Dry eye disease (DED) can be extremely distressing and is common in type 2 diabetes (T2D). To investigate potential biomarkers of DED in T2D, panels of proteins in tears, alongside clinical signs and symptoms of DED, were assessed. Patients were classified into four groups: T2D + DED (n = 47), T2D-only (n = 41), DED-only (n = 17) and healthy controls (n = 17). All patients underwent the Ocular Surface Disease Index (OSDI) and Dry Eye-Related Quality of Life (DEQS) questionnaires, tear evaporation rate (TER), fluorescein tear break-up time (fTBUT), corneal fluorescein staining (CFS) and Schirmer 1 test assessments. Six metabolic proteins and 14 inflammatory cytokines were analyzed with multiplex bead analysis. Interleukin (IL)-6 and IL-8 concentrations in tears were significantly higher in the T2D + DED group, and these biomarkers were positively correlated with CFS. In addition, tear IL-6 was negatively correlated with fTBUT in the T2D + DED group. Clinical signs of DED in the T2D + DED group were similar to the DED-only group. The T2D + DED group had more patients with moderate and severe DED (versus the DED-only group), suggesting a different pathogenesis for DED in T2D versus DED-only. Therefore, IL-6 and IL-8 could potentially be diagnostic biomarkers of DED in T2D.

Tear secretion by Diquafosol suppresses the excitability of trigeminal brainstem nuclear complex neurons by reducing excessive P2Y2 expression in the trigeminal ganglion in dry eye rats

The P2Y₂ receptor agonist, diquafosol sodium, is commonly used to treat the signs and symptoms of dry eye disease (DE) patients. Although diquafosol improves tear film stability, the neural mechanisms underlying the reduction in ocular pain are not well defined. This study determined if repeated application of diquafosol reduces the sensitization of nociceptive neurons in the lower trigeminal brainstem nuclear complex (TBNC) via peripheral P2Y₂ mechanisms in a rat model for DE. Diquafosol was applied to the ocular surface daily for 28 days, starting at day 0 or day 14, after exorbital gland removal. The number of eyeblinks, P2Y₂-immunoreactive neurons in the trigeminal ganglion (TG), and correlates of TBNC neural excitability (i.e., cFos protein and phosphorylated extracellular signal-regulated kinase (pERK) expression) were assessed in male rats. Diquafosol increased spontaneous tear volume and reduced the number of ocular surface-evoked eyeblinks in DE rats. Fluorogold-labeled TG neurons that supply the cornea expressed P2Y₂. The number of P2Y₂-immunoreactive neurons was increased in DE rats and suppressed by diquafosol. Diquafosol also reduced the number of cFos- and pERK-immunoreactive neurons in the TBNC in DE rats. These findings suggest that diquafosol, regardless of late-phase treatment, relieves ocular nociception in DE by reducing peripheral P2Y₂ expression.

Diquafosol sodium reduces neuronal activity in trigeminal subnucleus caudalis in a rat model of chronic dry eye disease

Patients with persistent and severe dry eye disease (DED) have corneal hypersensitivity, resulting in ocular pain, and diquafosol sodium, a potent P2Y₂ receptor agonist, is commonly used to improve the resultant tear film stability. This study determined the effects of diquafosol instillation on the suppression of trigeminal subnucleus caudalis (Vc) neuronal activity and ocular pain by enhancing tear film stability in the model for chronic DED. The effects of diquafosol on the ocular surface were assessed by the topical application for 28 days, starting from the 14th day since unilateral exorbital gland removal (chronic DED). Loss of tear volume secretion in chronic DED rats was significantly reversed by diquafosol instillation after 28 days, compared with saline treatment. The number of eyeblinks and pERK-IR neurons in the superficial laminae of Vc following hypertonic saline administration to the ocular surface was lower in diquafosol-treated chronic DED rats than in saline-treated rats. The neuronal activity evoked by hypertonic saline and mechanical stimulation along with the spontaneous neuronal activity in the superficial laminae of the Vc were suppressed in diquafosol-treated chronic DED rats. These findings suggest that ocular surface instillation of diquafosol for 28 days attenuates the neuronal hyperactivity in the Vc and the ocular pain that often occurs in chronic DED.

Efficacy of Topical Administration of Corticosteroids for the Management of Dry Eye Disease: Systematic Review and Meta-Analysis

The efficacy of corticosteroids (CS) for dry eye disease (DED) has been investigated in the clinical setting. The present study investigated whether topical CS application improves the clinical outcome at last follow-up compared to the baseline. The present study was conducted according to the PRISMA 2020. All the randomized clinical trials (RCTs), which investigated the efficacy of corticosteroids in the management of DED, were accessed. In September 2022, the following databases were accessed: Pubmed, Web of Science, Google Scholar, and Embase. The following data were extracted at baseline and at last follow-up: Ocular Surface Disease Index (OSDI), tear breakup time test (TBUT), Schirmer I test (SIT), and corneal staining. Data from 425 patients were retrieved. A total of 69.4% (295 of 425 patients) were women. CS were effective to improve SIT (p = 0.02) and corneal staining (p = 0.003) at the last follow-up of 10.0 ± 15.3 weeks. TBUT was greater in the CS than in the control group at the last follow-up (p = 0.002). Concluding, topical CS administration led to an increase of SIT and a reduction of corneal staining at a mean of 10 weeks follow-up in patients with DED. Compared to a control group, topical CS administration evidenced greater values of TBUT. Altogether, a good safety profile was witnessed in DED patients receiving CS. However, different safety profiles of different CS formulations were not investigated due to a lack of quantitative data. The exact dosing frequency, duration of therapy, and favorable potency of the CS are still under investigation. Future randomized, controlled trials with larger sample sizes are warranted to provide higher-quality evidence to establish the role of CS in DED.

Impact of Diquafosol Ophthalmic Solution on Tear Film and Dry Eye Symptom in Type 2 Diabetic Dry Eye: A Pilot Study

Background: Diquafosol ophthalmic solution (DQS) stimulates P2Y2 receptors on the ocular surface, which enhances mucin secretion from goblet cells. Therefore, tear film stability and hydration of the ocular surface can be achieved independent from lacrimal gland function. Methods: This prospective, open-label pilot study included 60 eyes of 30 diabetic patients diagnosed with dry eye disease (DED) and were randomly assigned to either DQS (n = 30 eyes) or hyaluronate (HA) group (n = 30 eyes). Participants in the DQS group received 3% diquafosol ophthalmic solution, whereas HA group received 0.1% sodium HA preservative-free artificial tears. The dosage for both drugs was 1 drop, 6 times per day for 4 weeks. Tear film lipid layer (TFLL), noninvasive breakup time (NITBUT), corneoconjunctival staining (CS) score, meibomian gland (MG), conjunctival hyperemia [redness score (RS)], ocular surface disease index (OSDI) was assessed and compared at baseline, day 14, and day 28. Results: Comparing baseline and day 28 measurements revealed that both groups found significant improvements in NITBUT, CS, MG quality, MG expressibility, and OSDI scores significantly (P < 0.05), in addition TFLL improvements were only found in the DQS group. At day 28, the magnitude of change in mean NITBUT was 1.74 (DQS) versus 0.31 (HA), 1.16 (DQS) versus 0.37 (HA) point grade reduction in corneoconjunctival staining score and 9.80 (DQS) versus 4.80 (HA) point grade in mean OSDI score. Conclusion: Three percent diquafosol ophthalmic solution treatment demonstrated the ability to improve the tear film dry eye parameters and clinically reduced sign and symptoms of DED in diabetic dry eye patients. Clinical Trials.gov ID: NCT04980144.

Defining Dry Eye from a Clinical Perspective

Over the past decades, the number of patients with dry eye disease (DED) has increased dramatically. The incidence of DED is higher in Asia than in Europe and North America, suggesting the involvement of cultural or racial factors in DED etiology. Although many definitions of DED have been used, discrepancies exist between the various definitions of dry eye disease (DED) used across the globe. This article presents a clinical consensus on the definition of DED, as formulated in four meetings with global DED experts. The proposed new definition is as follows: “Dry eye is a multifactorial disease characterized by a persistently unstable and/or deficient tear film (TF) causing discomfort and/or visual impairment, accompanied by variable degrees of ocular surface epitheliopathy, inflammation and neurosensory abnormalities.” The key criteria for the diagnosis of DED are unstable TF, inflammation, ocular discomfort and visual impairment. This definition also recommends the assessment of ocular surface epitheliopathy and neurosensory abnormalities in each patient with suspected DED. It is easily applicable in clinical practice and should help practitioners diagnose DED consistently. This consensus definition of DED should also help to guide research and clinical trials that, to date, have been hampered by the lack of an established surrogate endpoint.

Capsaicin-induced pain sensitivity in short tear break-up time dry eye

PURPOSE

To evaluate transient receptor potential vanilloid 1 (TRPV1)-mediated pain sensitivity in patients with short tear break-up time (TBUT) dry eye (DE) by using the capsaicin stimulus test.

METHODS

This prospective cross-sectional comparative study included 22 eyes of 22 patients with short TBUT DE and 11 eyes of 11 non-DE control subjects. Patients were divided into two groups based on response to standard DE treatments: 10 non-responders (intractable DE) and 12 responders (responsive DE). Mechanical touch (M-touch) and mechanical pain (M-pain) were measured using a Cochet-Bonnet esthesiometer. Capsaicin-induced pain (C-pain) and C-pain duration (C-pain DT) were measured using a capsaicin stimulus test. Psychological distress was also assessed.

RESULTS

M-touch sensitivity was similar among all three groups. M-pain sensitivity was higher in the responsive DE group than in the intractable DE and control groups (P < .001). C-pain sensitivity was lower (P < .001) in the intractable DE group than in the responsive DE and control groups, and C-pain DT was shorter (P = .006) in the intractable DE group than in the responsive DE group. Psychological distress was higher in the intractable DE group than in the control group (P < .001).

CONCLUSIONS

Patients with intractable short TBUT DE were less sensitive to the effects of capsaicin than patients with responsive short TBUT DE and controls. Altered neural activation may contribute to the development of DE symptoms in the short TBUT DE subjects. The capsaicin stimulus test may be used to better understand pain sensitivity in short TBUT DE patients.

Advances in the diagnosis and treatment of dry eye

The core mechanism of dry eye is the tear film instability. Tear film-oriented diagnosis (TFOD) is a concept to clarify the cause of tear film instability by tear film, and tear film-oriented treatment (TFOT) is a concept to treat dry eye disease by replacing the lacking components of the tear film layer based on the TFOD. In TFOD, the fluorescein breakup pattern of the tear film is important, and the subtype of dry eye can be judged to some extent from the breakup patterns. Current noninvasive devices related to the dynamic analysis of the tear film and visual acuity enabled the diagnosis of dry eye, subtype analysis, and the extent of severity. In Asian countries, secretagogues represent the main treatment in TFOT. Since meibomian gland dysfunction is a factor that greatly affects the tear breakup time, its treatment is also essential in the dry eye treatment strategy. A newly discovered dry eye subtype is the short breakup time-type (BUT) of dry eye. The only abnormal finding in this disease is the short BUT, suggesting a relationship with ocular neuropathic pain and eye strain. Recently, data from many studies have accumulated which show that dry eye is a life-style disease. In addition to the treatment of dry eyes, it is becoming possible to prevent the onset by intervening with the daily habits, diet, exercise and sleep, etc. It has been pointed out that oxidative stress is also involved in the pathology of dry eye, and intervention is being carried out by improving diet and taking supplements. Future research will be needed to link clinical findings to the molecular biological findings in the tear film.

Analysis of the association between the severity of ocular and systemic pain

PURPOSE

To evaluate the relationship between the severity of ocular and systemic pain.

METHODS

A cross-sectional study was conducted in patients with ocular pain symptoms who were observed in Keio University Hospital between April 2017 and September 2018. Evaluations consisted of the Dry Eye-Related Quality of Life Score (DEQS), Short-Form McGill Pain Questionnaire (SF-MPQ), visual analog scale (VAS), and ophthalmologic examination, including tear breakup time measurement and Schirmer I test. The revised Asia Dry Eye Society Dry Eye Disease (DED) diagnostic criteria were used.

RESULTS

The present study involved 41 participants (31 women; mean age, 57.6 ± 17.5 years). Thirteen participants had aqueous-deficient DED, 18 participants had short tear break-up time DED, and 10 participants had no DED. Multivariate regression analysis revealed that the DEQS was significantly associated with both the SF-MPQ total (Coefficient score β = 0.92, p < 0.01) and the VAS (β = 0.25, p = 0.01). In addition, correlation analysis revealed that the DEQS had a significant positive linear correlation with both the SF-MPQ total (Spearman correlation score rs = 0.70, p < 0.01) and the VAS (rs = 0.66, p < 0.01).

CONCLUSIONS

The findings of the present study suggested that the ocular pain score was significantly associated with systemic pain score. Participants with higher systemic pain scores have an increased risk of having ocular pain.

Short Tear Film Breakup Time-Type Dry Eye

Measurement of tear film breakup time (TBUT) has become a standard diagnostic procedure in the dry eye clinic. Short TBUT-type dry eye is characterized by TBUT of less than 5 seconds and dry eye symptoms such as ocular fatigue or dryness; the importance of this type has recently been gaining prominence. Patients with this condition show no reduction in tear production and no staining of the ocular surface. The severity of symptoms is almost the same as in dry eye in which the ocular surface is stained with rose bengal or fluorescein. In addition to discomfort, patients suffer from decreased vision due to the unstable tear film, which can be attributed to the relative abnormality of the lipid layer, aqueous layer, and/or mucin layer. The diagnosis should be performed carefully on the basis of the patient's symptoms and the TBUT test, because the ocular surface appears normal and remains unstained.