Effects of Osmoprotection on Symptoms, Ocular Surface Damage, and Tear Film Modifications Caused by Glaucoma Therapy

Glaucoma and Dry Eye Disease: Opportunity to Assess and Treat

Dry eye disease (DED) has been found to occur at a higher prevalence in individuals with glaucoma than in individuals without glaucoma. The relationship between glaucoma and DED may be, in part, a result of glaucoma therapy. Greater number of antiglaucoma medications used and greater number of antiglaucoma eyedrops instilled per day have been associated with ocular surface disease in patients with glaucoma. Use of antiglaucoma medication has also been associated with higher levels of ocular surface inflammatory markers and ocular surface alterations. There is evidence to suggest that antiglaucoma medications with preservatives and, to some extent, antiglaucoma medication formulations without preservatives may contribute to ocular surface signs and symptoms. Trabeculectomy for glaucoma has also been associated with ocular surface signs related to DED; however, there may be benefits of trabeculectomy and other procedures for glaucoma due to reduced use of antiglaucoma medications. Patients with glaucoma with ocular surface disease have been found to have greater ocular surface symptoms, poorer vision-related quality of life, and poorer antiglaucoma medication adherence compared with patients with glaucoma without ocular surface disease. Because of the potential negative impact of DED on patients with glaucoma, patients with glaucoma may benefit from evaluation for DED. Management of DED in patients with glaucoma may include modifications to antiglaucoma medications and use of treatments for DED.

New trends towards glaucoma treatment: Topical osmoprotective microemulsions loaded with latanoprost

The chronic use of hypotensive agents eventually leads to ocular surface damage and poor patient compliance during glaucoma management. Thus, new sustained drug delivery systems are needed. This work aimed to develop osmoprotective latanoprost-loaded microemulsion formulations as new potential glaucoma treatments with ocular surface protective properties. The microemulsions were characterized and latanoprost encapsulation efficacy determined. In-vitro tolerance, osmoprotective efficacy, cell internalization as well as cell-microemulsion interactions and distribution were performed. In vivo hypotensive activity was conducted in rabbits to assess intraocular pressure reduction and relative ocular bioavailability. Physicochemical characterization showed nanodroplet sizes within 20-30 nm, being in vitro tolerance within 80 and 100% viability in corneal and conjunctival cells. Besides, microemulsions exhibited higher protection under hypertonic conditions than untreated cells. Cell fluorescence lasted for 11 days after short exposure to coumarin-loaded microemulsions (5 min) showing extensive internalization in different cell compartments by electronic microscopy. In vivo studies exhibited that a single instillation of latanoprost-loaded microemulsions reduced the intraocular pressure for several days (4-6 days without polymer and 9-13 days with polymers). Relative ocular bioavailability was 4.5 and 19 times higher than the marketed formulation. These findings suggest the use of these microemulsions as potential combined strategies for extended surface protection and glaucoma treatment.

The Effect of Prostaglandin Analogs on Central Corneal Thickness of Patients with Glaucoma or Ocular Hypertension: A Systematic Review

BACKGROUND

Prostaglandin analogs (PGAs) are first-line antiglaucoma agents that appear to either decrease or increase central cornea thickness (CCT), creating controversy regarding the benefits of PGAs in treating CCT.

PURPOSE

We performed the first meta-analysis of observational studies to evaluate the effects of PGAs on CCT in patients with glaucoma or ocular hypertension (OHT).

METHODS

This systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. A literature search was performed of the PubMed, Embase, Cochrane Library, System for Information on Grey Literature in Europe (Open Grey), and ClinicalTrials.gov databases and the references of retrieved studies. Only observational studies were included in the meta-analysis. The final CCT of patients and 95% confidence interval (CI) of each study were extracted. Study quality was assessed using the Newcastle-Ottawa Scale (NOS) and the Agency for Healthcare Research and Quality (AHRQ). A fixed-effects model was used to calculate the weighted mean difference (WMD) and 95% CI. Subgroup analyses based on several stratified factors such as public bias (Begg's test) and sensitivity analyses were performed.

RESULTS

Five cohort, 5 case-control, and three cross-sectional studies including 2,722 subjects were included. The pooled effect of all thirteen studies showed that PGAs reduced the CCT of patients with glaucoma or OHT slightly but significantly (WMD = -9.37; 95% CI [-12.18, -6.57]; p = 0.00; I2 = 45.5%). Significant effects were also observed in all three study designs: cohort (WMD = -5.17; 95% CI [-9.52, -0.82]), case-control (WMD = -15.31; 95% CI [-22.66, -7.97]), and cross-sectional (WMD = -8.65; 95% CI [-17.30, -0.01]). In addition, subgroup analysis of exposure time showed the effect of PGAs to be more obvious in the first (WMD = -5.81; 95% CI [-9.49, -2.14]) and second (WMD = -13.73; 95% CI [-20.19, -7.28]) years.

CONCLUSIONS

The pooled effects of previously reported studies suggest that PGA use can reduce the CCT of patients with glaucoma or OHT slightly but significantly, with this effect more pronounced in the first 2 years. These findings suggest that clinicians must closely monitor changes in CCT in the first 2 years of PGA use to identify cases of intraocular pressure misestimation and the efficacy of PGAs.

Hyaluronic acid in the treatment of dry eye disease

Dry eye disease (DED) is a highly prevalent and debilitating condition affecting several hundred million people worldwide. Hyaluronic acid (HA) is a naturally occurring glycosaminoglycan commonly used in the treatment of DED. This review aims to critically evaluate the literature on the safety and efficacy of artificial tears containing HA used in DED treatment. Literature searches were conducted in PubMed, including MEDLINE, and in Embase via Ovid with the search term: "(hyaluronic acid OR hyaluronan OR hyaluronate) AND (dry eye OR sicca)". A total of 53 clinical trials are included in this review, including eight placebo-controlled trials. Hyaluronic acid concentrations ranged from 0.1% to 0.4%. Studies lasted up to 3 months. A broad spectrum of DED types and severities was represented in the reviewed literature. No major complications or adverse events were reported. Artificial tears containing 0.1% to 0.4% HA were effective at improving both signs and symptoms of DED. Two major gaps in the literature have been identified: 1. no study investigated the ideal drop frequency for HA-containing eyedrops, and 2. insufficient evidence was presented to recommend any specific HA formulation over another. Future investigations assessing the optimal drop frequency for different concentrations and molecular weights of HA, different drop formulations, including tonicity, and accounting for DED severity and aetiology are essential for an evidence-based, individualized approach to DED treatment.

Combined hyperosmolarity and inflammatory conditions in stressed human corneal epithelial cells and macrophages to evaluate osmoprotective agents as potential DED treatments

PURPOSE

To develop an easy-to-perform combined model in human corneal epithelial cells (HCECs) and Balb/c mice macrophages J774.A1 (MP) for preliminary screening of potential ophthalmic therapeutic substances.

METHODS

HCECs were exposed to different osmolarities (350-500 mOsm/L) and MTT assay was employed for cell survival and flow cytometry to assess apoptosis-necrosis and relative cell size (RCS) distribution. Effectiveness of Betaine, L-Carnitine, Taurine at different concentrations (ranging from 20 mM to 200 mM) was studied. Also, mucoadhesive polymers such as Hyaluronic acid (HA) and Hydroxypropylmethylcellulose (HPMC) (0.4 and 0.8%) were evaluated. Cells were pre-incubated with the compounds (8h) and then exposed to hyperosmotic stress (470 mOsm/L) for 16h. Moreover, anti-inflammatory activity was performed in LPS-stimulated MP.

RESULTS

Exposure to hyperosmotic solutions between 450 and 500 mOsm/L promoted the highest cell death after 16h exposures (p < 0.0001) with a drop in viability to 34.96% ± 11.77 for 470 mOsm/L. Pre-incubation with Betaine at 150 mM and 200 mM provided the highest cell survival against hyperosmolarity (66.01% ± 3.65 and 65.90% ± 0.78 respectively) while HA 0.4% was the most effective polymer in preventing cell death (42.2% ± 3.60). Flow cytometry showed that Betaine and Taurine at concentrations between 150-200 mM and 20-80 mM respectively presented the highest anti-apoptotic activity. Also, HA and HPMC polymers reduced apoptotic-induced cell death. All osmoprotectants modified RCS, and polymers increased their value over 100%. L-Carnitine 50 mM, Taurine 40 mM and HA 0.4% presented the highest TNF-α inhibition activity (60%) albeit all of them showed anti-inflammatory inhibition percentages higher than 20% CONCLUSIONS: HCECs hyperosmolar model combined with inflammatory conditions in macrophages allows the screening of osmoprotectants by simulating chronic hyperosmolarity (16h) and inflammation (24h).

Progress in the use of plasma rich in growth factors in ophthalmology: from ocular surface to ocular fundus

Introduction: The use of blood derivatives and especially Plasma rich in growth factors (PRGF), for regenerative purposes has been a common trend along the last decades in the field of oral surgery, dermatology, orthopedics, and more recently in ophthalmology.Areas covered: PRGF is a type of platelet-rich plasma that is being explored for the treatment of ocular injuries. The present review article highlights 50 ophthalmology-related publications about the application of PRGF in the treatment of acute and chronic pathologies in ophthalmology as well as most relevant challenges and future prospects.Expert opinion: PRGF technology provides a wide range of formulations that can be used therapeutically in many different acute and chronic ocular pathologies. In addition to eye drops enriched with autologous growth factors, PRGF enables the preparation of both immunologically safe and fibrin-based formulations. Recent advances in the field have promoted PRGF storage for 12 months under freezing conditions, its daily use for 7 days at room temperature and the freeze-dried formulation. The thermally treated immunosafe formulation has shown promising clinical results for the treatment of several diseases such as Sjögren syndrome, graft versus host disease or cicatrizing conjunctivitis. In addition, several fibrin formulations have been preclinically evaluated and clinically incorporated as an adjuvant to ocular surface or glaucoma surgeries, dermal fat graft procedures, limbal stem cell expansion and retinal surgeries. The present review explores the latest scientific and clinical data, current challenges, and main prospects of this technology for the treatment of several ocular injuries.

Tear Film Osmolarity, Ocular Surface Disease and Glaucoma: A Review

Glaucoma is the second leading cause of blindness in the world, affecting more than 60 million people globally. In order to reduce the progression of the disease, both medical and surgical treatments are used. Frequent side effects of both treatments include a range of modifications of the ocular surface grouped as the Ocular Surface Disease (OSD), which include Dry Eye Disease (DED). DED and other OSD negatively impact on the success of anti-glaucoma treatments and reduce the adherence to medical therapies. Tear film osmolarity (TFO) is a relatively novel test which has become a hallmark of DED. The aim of this paper was to review the association between OSD, DED and glaucoma in view of published TFO data, and to discuss future fields of research and treatments on the topic of glaucoma iatrogenic damage.

Evaluation of an enhanced viscosity artificial tear for moderate to severe dry eye disease: A multicenter, double-masked, randomized 30-day study

PURPOSE

In a randomized, controlled clinical trial, two lubricant artificial tear formulations with enhanced viscosity were compared: an investigational product at the time, containing carboxymethylcellulose 1.0% and glycerin 0.9% (CMC-GLY) with osmoprotectants, and a standard formula containing carboxymethylcellulose 1.0% alone (CMC).

METHODS

This double-masked study recruited patients with moderate to severe dry eye at 10 US centers. After a 7-day run-in with CMC 0.5% (Refresh Tears) patients were randomized to use either CMC-GLY or CMC as needed, but at least 2 times daily for 30 days. Patients were stratified by Ocular Surface Disease Index^© (OSDI) score into moderate (23-32) and severe (> 32-65) subgroups. Assessments included OSDI (primary efficacy variable), corneal and conjunctival staining, tear break-up time (TBUT), symptom surveys, and safety variables. Study visits were days 1 (baseline/randomization), 7, and 30.

RESULTS

A total of 188 patients (94 CMC-GLY, 94 CMC) were enrolled. The severe subgroup had 67 CMC-GLY and 65 CMC patients. OSDI scores progressively improved and were similar at day 30 between treatment groups. At day 7, only the CMC-GLY group demonstrated significant improvements from baseline in OSDI score (all patients p < 0.001, severe p < 0.001), corneal staining (p = 0.004), and TBUT (p < 0.001). Between-group dose frequency for CMC-GLY was lower at day 7 (p = 0.031). Other efficacy results were similar between groups. The most commonly reported adverse event in both groups was blurred vision.

CONCLUSIONS

Overall, the CMC-GLY artificial tear formulation was as effective as the CMC formulation. CMC-GLY demonstrated improvements at an earlier stage (day 7). Both artificial tear formulations were safe and well tolerated, with no treatment-related serious adverse events. These results support the use of the CMC-GLY artificial tear formulation as an effective treatment to reduce the symptoms and signs of dry eye disease.

Plasma rich in growth factors eye drops to treat secondary ocular surface disorders in patients with glaucoma

Purpose

To evaluate the efficacy and safety of plasma rich in growth factors (PRGF) eye drops in patients with glaucoma with secondary ocular surface disorders (OSDs) due to surgeries and topical hypotensive drugs use.

Materials and methods

A retrospective case-series study design was used including six patients (eight eyes) diagnosed with glaucoma who received surgical (nonpenetrating deep sclerectomy and/or trabeculectomy) and medical treatments (hypotensive eye drops) to control intraocular pressure (IOP) and who developed secondary OSDs, unresponsive to conventional treatments. Patients were treated with PRGF eye drops (four times a day). Outcome measures were ocular surface disease index (OSDI), best-corrected visual acuity (BCVA, in logarithm of the minimum angle of resolution), visual analog scale (VAS), frequency and severity of symptoms, and IOP. The safety of the treatment was also evaluated.

Results

Six patients (seven eyes with open-angle glaucoma and one eye with uveitic glaucoma) treated with PRGF eye drops were evaluated. Mean age was 71 years (SD=7.2, range 58–79 years). Five were female and one was male. The mean treatment time was 21.8 weeks (SD=9.0, range 12–36 weeks). The mean time to reach closure of the corneal ulcer was 14.5 (SD=5.5) weeks. A statistical significant reduction in OSDI scale (50.6%), VAS frequency (53.1%), VAS severity (42.0%), and a 41.8% improvement in BCVA were observed (p<0.05). IOP also decreased by 16.6% (p=0.010). Only one of the six patients reported itching in both eyes as an adverse event (AE); however, the patient continued with the PRGF eye drops until the end of therapy; the remaining patients did not report any AEs during the follow-up period.

Conclusions

In patients with glaucoma and secondary OSDs refractive to conventional treatments, the treatment with PRGF eye drops could be considered a possible therapeutic option, because it demonstrates an improvement in the signs and symptoms of the ocular surface, as well as a better control of the IOP. This is an initial research work that can open doors for future research to confirm these findings.

Barriers to Glaucoma Medication Compliance Among Veterans: Dry Eye Symptoms and Anxiety Disorders

OBJECTIVE

To identify barriers to compliance of medical treatment for glaucoma among veterans.

METHODS

Patients with glaucoma from the Miami Veterans Affairs Eye Clinic (n=74) filled out a 63-question survey regarding dry eye symptoms, concurrent systemic disease, and medications. The association between glaucoma medical compliance was defined as self-reported adherence to drop regimens greater than 75% of the time.

RESULTS

Eighty percent of veterans (n=59) reported compliance with glaucoma therapy. Dry eye symptoms (as defined by Dry Eye Questionnaire 5 score ≥6) were reported by 39% (n=29), and their presence was associated with decreased compliance (63% vs. 89%, P=0.007). Anxiety and posttraumatic stress syndrome (PTSD) were also associated with significant noncompliance (64% vs. 83%, P=0.05 and 58% vs. 84%, P=0.02, respectively). Other studied factors including demographics, depression (P=0.11), and glaucoma regimens did not play a significant role in glaucoma medication compliance.

CONCLUSIONS

Dry eye symptoms, PTSD, and anxiety were associated with decreased compliance to medical treatment of glaucoma. Identifying and treating underlying ocular surface disease and anxiety disorders may lead to increased adherence to glaucoma treatment.

A rating scale is a proper method to evaluate changes in quality of life due to dry eye symptoms

PURPOSE

To determine which utility value assessment method is more suitable to evaluate changes in the quality of life due to dry eye symptoms.

METHODS

Dry eye outpatients with a presenting visual acuity of 20/25 or better in the worse-seeing eye were recruited. Presenting distance visual acuity, tear film break-up time, Schirmer I test and fluorescein were assessed. The severity of dry eye symptoms was assessed using the Ocular Surface Disease Index (OSDI), and utility values were measured using the time trade-off (TTO), standard gamble (SG1 and SG2) and rating scale (RS) methods. Different utility values were compared with each other. The most appropriate utility value method to evaluate quality-of-life changes solely due to dry eye symptoms is determined by calculating the correlation between the OSDI score and different utility values.

RESULTS

A total of 104 patients were enrolled. The three sections of OSDI in the order of high to low scores were as follows: "environmental trigger," "eye discomfort" and "visual function." The utility scores measured with TTO, SG1, SG2 and RS were 0.95 ± 0.11, 0.96 ± 0.10, 0.99 ± 0.07 and 0.89 ± 0.10, respectively. The utility scores evaluated by the TTO, SG1, SG2 and RS methods were significantly different from each other (p < 0.05). Only the utility scores measured with RS were significantly correlated with the composite OSDI score, "environmental trigger" and "eye discomfort" section scores (p < 0.05).

CONCLUSIONS

RS is more sensitive than TTO and SG for the evaluation of altered quality of life due to dry eye symptoms.

Investigating the potential benefits of a new artificial tear formulation combining two polymers

PURPOSE

Artificial tear formulations typically contain a water-soluble polymer to enhance residence time, moisture retention, and binding to the mucin coat of the ocular surface, which facilitate corneal healing. This study investigated the potential advantages of combining carboxymethylcellulose (CMC) and hyaluronic acid (HA) polymers in a single formulation.

MATERIALS AND METHODS

Individual CMC and HA solutions were prepared and tested for bulk viscosity in comparison to a solution that combined CMC and HA. Rheometry determined the differences between solutions at increasing shear rates, simulating eye movement and blinking.

RESULTS

The bulk viscosity of the individual 0.5% CMC and 0.1% HA solutions was 2.5 and 5.7 cP, respectively. The viscosity of the combined solution (13.1 cP) was 60% higher than predicted by additive effects. Rheometry revealed shear rates between 10/second (open eye) and 10,000/second (blinking eye). At these rates, viscosity ranged from 2.7 to 3.5 cP for 0.5% CMC, 2.8 to 6.8 cP for 0.1% HA, and 5.2 to 15.3 cP for the 0.5% CMC-0.1% HA combination. Low-shear viscosity of the CMC-HA combination increased 48% over the sum of the individual solutions, but high-shear viscosity remained virtually unchanged. Data from CMC and HA solutions at higher concentrations were consistent with these results.

CONCLUSION

Combining CMC and HA polymers produced a synergistic increase in low-shear viscosity (which cannot be fully explained by simple molecular entanglement), while the high-shear viscoelasticity of the combined solution remained unaffected. These data suggest that CMC-HA combinations have properties that may be used to formulate artificial tears that optimize ocular retention (through higher low-shear viscosity), while minimizing blur and stickiness during blinking (through lower high-shear viscosity).

Osmoprotectants, carboxymethylcellulose and hyaluronic acid multi-ingredient eye drop: a randomised controlled trial in moderate to severe dry eye

Purpose

To assess the safety and efficacy of an eye drop combining osmoprotectants, carboxymethylcellulose and hyaluronic acid (O/CMC/HA) in reducing symptomatic, moderate to severe dry eye, compared with HA.

Methods

In this investigator-masked, randomised study, patients instilled 1–2 drops/eye of O/CMC/HA or HA (2–6 times/day) for 3 months. Primary endpoint: mean change in Global Ocular Staining Score (GOSS) from baseline at day 35. Noninferiority of O/CMC/HA was tested in the per-protocol population; if achieved, superiority was tested in the intent-to-treat population. Secondary efficacy endpoints: mean change from baseline in GOSS, Ocular Surface Disease Index (OSDI), Schirmer score, tear break-up time (TBUT), corneal/conjunctival staining, conjunctival hyperaemia, symptoms, and patient/investigator assessments.

Results

Baseline characteristics were comparable between groups (n=40 each). O/CMC/HA was noninferior (and not superior) to HA based on similar GOSS reductions from baseline at day 35 and month 3 in both groups (P=0.778, day 35, per-protocol population). Overall, O/CMC/HA and HA provided similar reductions in OSDI, Schirmer score, TBUT, corneal staining and hyperaemia from baseline at 35 days (P≥0.155). More patients reported less severe stinging/burning, sandiness/grittiness, and painful/sore eyes at month 3 with O/CMC/HA (P≤0.039), and more rated the dropper bottle easy to use (87.5%), compared with HA (46.2% P=0.002). Other patient and investigator assessments were similar between groups. O/CMC/HA and HA were well tolerated.

Conclusions

O/CMC/HA is noninferior to HA in improving objective signs of dry eye, with potential advantages for subjective symptoms and patient acceptance.

Effect of 0.3% Hydroxypropyl Methylcellulose/Dextran Versus 0.18% Sodium Hyaluronate in the Treatment of Ocular Surface Disease in Glaucoma Patients: A Randomized, Double-Blind, and Controlled Study

PURPOSE

To compare the efficacy and safety of 0.3% hydroxypropyl methylcellulose/dextran (HPMC/dextran) and 0.18% sodium hyaluronate (SH) in the treatment of ocular surface disease in patients using antiglaucoma drugs containing preservatives.

METHODS

This was a double-blind, randomized, parallel-group study in 70 glaucoma patients with Ocular Surface Disease Index (OSDI) score greater than 20 points and/or presence of ocular signs. Patients were randomized to receive either preservative-free 0.3% HPMC/dextran (n=35) or preservative-free 0.18% SH (n=35). Treatment was 1 drop in each eye, 4 times a day. Data were collected at baseline, at day 7 and day 28.

RESULTS

The groups were homogeneous at baseline. At day 28, both treatments showed significant improvements (P<0.05) in the mean OSDI score, lid skin and lid margin inflammation, conjunctival injection, and expressibility of meibomian glands, corneal staining score, fluorescein tear breakup time (FBUT), and Schirmer I test. However, the mean OSDI score, lid margin inflammation and conjunctival injection showed significant improvements (P<0.05) in the SH group at days 7 and 28, compared to the HPMC/dextran group. FBUT and the Schirmer I test also showed significant improvements (P<0.05) in the SH group compared to the HPMC/dextran group, at day 28. No adverse reactions were observed in either group.

CONCLUSIONS

Preservative-free artificial tear, 0.3% HPMC/dextran, and 0.18% SH, caused a significant relief of the ocular surface disease in glaucoma patients. However, 0.18% SH led to a greater improvement in ocular signs and symptoms than 0.3% HPMC/dextran.

Efficacy and safety of two new formulations of artificial tears in subjects with dry eye disease: a 3-month, multicenter, active-controlled, randomized trial

Purpose

To evaluate and compare the efficacy and safety of two investigational artificial tear formulations (CHO-1 and CHO-2) containing carmellose sodium, hyaluronic acid at different concentrations, and osmoprotectants, with a standard carmellose sodium-containing formulation (Refresh Tears [RT]) in the treatment of dry eye disease.

Subjects and methods

In this 3-month, double-masked, multicenter study, subjects (n=305) were randomized 1:1:1 to receive CHO-1, CHO-2, or RT, used as needed but at least twice daily. The primary endpoint was change in ocular surface disease index (OSDI) score from baseline to day 90. Other key outcomes included symptoms evaluated on a visual analog scale, corneal and conjunctival staining, and adverse events.

Results

OSDI scores and dry eye symptoms showed a rapid and sustained reduction from baseline in each group. Both CHO-1 and CHO-2 met the primary efficacy endpoint of noninferiority to RT in day 90 OSDI score change from baseline. OSDI ocular symptoms subscale improved more with CHO-1 than CHO-2 (P=0.048). In subjects with clinically relevant baseline ocular surface staining (>14 total score of a maximum of 55), day 90 improvements were greater with CHO-1 and CHO-2 than RT (P≤0.044). Day 90 improvements in OSDI ocular symptoms subscale scores were also greater with CHO-1 than RT (P<0.007) in subjects with clinically relevant ocular staining. All treatments were well tolerated.

Conclusion

Both combination artificial tear formulations were efficacious and well tolerated in subjects with dry eye. CHO-1 demonstrated the best performance in improving ocular symptoms and reducing ocular staining in this heterogeneous study population.

Role of hyperosmolarity in the pathogenesis and management of dry eye disease: proceedings of the OCEAN group meeting

Dry eye disease (DED), a multifactorial disease of the tears and ocular surface, is common and has a significant impact on quality of life. Reduced aqueous tear flow and/or increased evaporation of the aqueous tear phase leads to tear hyperosmolarity, a key step in the vicious circle of DED pathology. Tear hyperosmolarity gives rise to morphological changes such as apoptosis of cells of the conjunctiva and cornea, and triggers inflammatory cascades that contribute to further cell death, including loss of mucin-producing goblet cells. This exacerbates tear film instability and drives the cycle of events that perpetuate the condition. Traditional approaches to counteracting tear hyperosmolarity in DED include use of hypotonic tear substitutes, which have relatively short persistence in the eye. More recent attempts to counteract tear hyperosmolarity in DED have included osmoprotectants, small organic molecules that are used in many cell types throughout the natural world to restore cell volume and stabilize protein function, allowing adaptation to hyperosmolarity. There is now an expanding pool of clinical data on the efficacy of DED therapies that include osmoprotectants such as erythritol, taurine, trehalose and L-carnitine. Osmoprotectants in DED may directly protect cells against hyperosmolarity and thereby promote exit from the vicious circle of DED physiopathology.

Rasch analysis of the Ocular Surface Disease Index (OSDI)

PURPOSE

The Ocular Surface Disease Index (OSDI) is a 12-item scale for the assessment of symptoms related to dry eye disease and their effect on vision. Its reliability and validity have been investigated within the classical test theory framework and, more recently, using Rasch analysis. The purpose of the present analysis was to more completely investigate the functioning of its response category structure, the validity of its three subscales, and the unidimensionality of the latent construct it is intended to assess.

METHODS

Responses to the OSDI from 172 females participating in the Dry Eye in Postmenopause (DEiM) study who had previously been diagnosed with dry eye or reported significant ocular irritation and dryness were analyzed. Response category structure and item fit statistics were evaluated for assessment of model fit. Person separation statistics were used to examine the validity of the subscales. Unidimensionality was assessed by principal component analysis (PCA) of model residuals.

RESULTS

The recommended five-category response structure resulted in disordered response thresholds. A four-category structure resulted in ordered thresholds. Item infit statistics were acceptable for all 12 items. Person separation with this category structure was adequate, with a person separation index of 2.16. None of the three subscales demonstrated adequate person separation. PCA showed one other significant factor onto which the three environmental items loaded significantly.

CONCLUSIONS

All items demonstrated acceptable fit to the model after collapsing categories to order the response thresholds. The original subscales did not prove valid, and there is some evidence of multidimensionality and poor targeting.