Dry eye disease is a multifactorial dysfunction of the ocular surface characterized by altered structural integrity of the tear film.1 Patients with dry eye disease present symptoms of ocular discomfort and report impairment in social functioning and reduced quality of life.1–3 Generally, dry eye disease can be divided into “aqueous-deficient” and “evaporative” forms.4 Although the former hyposecretory type is associated with Sjögren and non-Sjögren lacrimal diseases, the latter, more frequent, type is mainly caused by meibomian gland dysfunction.1,4,5 The lipid coat of the tear film, primarily produced by the meibomian glands, covers the aqueous–mucous layers and plays a crucial role in ensuring tear stability and hindering evaporation by serving as a protective hydrophobic barrier.6–8 An absent or insufficient lipid layer, as is the case in meibomian gland dysfunction, can precipitate up to a four-fold increase in tear evaporation.8 Therefore, restoration of the lipid film and prevention of tear evaporation is the aim of effective therapy in evaporative dry eye disease.
Typically, dry eye disease is treated by topical substitution of the tear film.9 However, most such “lubricants” are water based and contain viscous polymers such as hyaluronic acid, hydroxypropylmethyl-cellulose, or polyvidone to increase precorneal residence time.9–11 Furthermore, they merely substitute the aqueous–mucous layers and often contain preservatives and additives that are associated with ocular toxicity.11,12
A novel lipophilic tear supplement, EvoTears (URSAPHARM GmbH), was introduced containing 100% perfluorohexyloctane, which is an aliphatic, semi-fluorinated hydrocarbon that is chemically, physically, and physiologically inert.11 Due to its complete aqueous-free nature, it does not promote microbial growth or necessitate preservatives, demonstrates good spreading properties, and restores the lipid layer of the tear film, preventing excessive evaporation of the aqueous–mucous layers.6,13,14 Clinical studies have shown significant beneficial effects of EvoTears in patients with evaporative dry eye disease14 and meibomian gland dysfunction13 when topically administered for 6 to 8 weeks.
In previous reports, the ocular surface of patients with dry eye disease has been shown to aggravate signs and symptoms after undergoing ocular interventions such as keratorefractive procedures or cataract surgeries.15–19 Such postoperative aggravation of the ocular surface integrity is a problem that is often underestimated because it is not only associated with worsening of the dry eye symptoms that may further reduce the quality of life, but also with worse visual outcomes, instability of postoperative refraction, and side effects such as perception of halo and glare.
The aim of this prospective, single-center, open-labeled clinical trial was to evaluate the efficacy and tolerability of EvoTears as a postoperative ocular surface treatment after cataract surgery in patients with evaporative dry eye disease.
Patients and Methods
In this prospective, single-center, open-label clinical trial, 40 patients were enrolled and examined preoperatively and 1 day, 1 week, and 5 weeks postoperatively. Per patient, only one eye was included in the evaluation. The fellow eye was not scheduled for surgery during the time of the study, operated on during the time of the study but not assessed for changes in dry eye disease parameters in the course of the study, or already operated on before inclusion in the study. All patients were adequately informed and signed the informed consent form prior to study inclusion. The study complied with the German Act on Medical Devices, MPG§23b, and EN ISO 14155:2012-01 (Clinical Trial on Medical Devices for Use in Humans), was performed according to the guidelines of Good Clinical Practice, and adhered to the tenets of the Declaration of Helsinki and the laws of the Federal Republic of Germany. The trial protocol and patient information were approved by the local ethics committee. The registered clinical trial number (EUDAMED) is CIV-16-12-017924.
Inclusion criteria were adults with the presence of age-appropriate cataract for which standard cataract surgery was planned, preoperative subjective complaints indicating an evaporative dry eye disease for at least 3 months with a frequency and severity of complaints score of 2 of 10 or greater (Symptom Assessment in Dry Eye Visual Analog Scale [VAS] questionnaire) and Ocular Surface Disease Index (OSDI) score of 15 or greater, and fluorescein tear break-up time (TBUT) of 10 seconds or less. Exclusion criteria were dry eye due to systemic disease or concomitant medication or malign conditions, preoperative use of lipid-containing tear substitute for at least 3 months, simultaneous use of other therapeutic ophthalmics, ocular or systemic pathologies that may have an influence on the postoperative irritation (eg, acute viral or bacterial inflammation of the conjunctiva/cornea or chronic inflammatory/infectious uveitis), history of ocular surgery or punctum plugs during the past 3 months, malposition of the eyelids and/or lagophthalmos, contact lens wear up to 3 months before surgery, hypersensitivity against the ingredient (perfluorohexyloctane) of EvoTears, and concurrent pregnancy or lactation.
On inclusion in the study, all patients received EvoTears and were instructed to use them four times a day, one drop in the conjunctival sac of the study eye in addition to the standard postoperative topical treatment (Isopto Max eye drops; Novartis Pharma GmbH) for 2 weeks and Isopto Max eye ointment (Novartis Pharma GmbH) 1x1/nocte for 1 week). No application of any eye drops was allowed up to 2 hours before an examination.
Preoperative and Postoperative Examination
At the preoperative visit, all patients were asked to fill out the VAS and OSDI questionnaires. The VAS questionnaire asked patients to judge their dry eye disease in terms of frequency of symptoms and severity of symptoms. Symptom assessment was evaluated by the VAS for the following symptoms: lacrimation, feeling of eye pressure, burning, foreign body sensation, mucus formation, and itching.20 The preoperative scores are expressed on a VAS from 0 to 10. At 1 and 5 weeks postoperatively, subjective changes in these values were further evaluated via VAS and they were transformed into a decimal scale using the percentage change from baseline. The OSDI is another widely validated questionnaire for measuring the severity of dry eye disease and its categories are listed as: normal (0 to 12 points), mild (13 to 22 points), moderate (23 to 32 points), and severe (33 to 100 points).20,21 In this study, the OSDI was used to verify the inclusion criteria of the patients preoperatively. It was not used postoperatively.
At all study visits, patients underwent an ophthalmological assessment including subjective refraction, corrected distance visual acuity (CDVA), slit-lamp examination, Goldmann applanation tonometry, and TBUT. Corneal staining was graded according to the Oxford grading scale.22 At preoperative and 5-week postoperative visits, the Schirmer test was performed with paper strips inserted into the lower eyelid pouch for 5 minutes without anesthesia (Schirmer I).13
During the course of the trial, the physicians monitored any pathologic symptoms and adverse events. Patients who reported having problems were offered an immediate visit at the study site and examined by the physician.
This study included 40 eyes of 40 patients with a mean age of 70.3 ± 9.4 years. There were 26 women (65%) and 14 men (35%). For the final data analysis, one patient was excluded from the postoperative data at the 5-week postoperative visit because this patient discontinued the use of EvoTears before the 5-week postoperative examination date due to subjective intolerance. At the preoperative visit, 38 patients (95%) had a “severe” OSDI total score, whereas 2 patients (5%) had a “moderate” OSDI total score. There were no patients with “normal” or “mild” preoperative OSDI scores.
Sample Size Calculation
For sample size calculation, previous literature was reviewed to define the approximate mean and standard deviation values for the primary endpoint, the TBUT.14,23 The calculation was performed according to the methods of Dupont and Plummer.24 Considering a power of 95% and an alpha value of 0.05, and under the hypothesis of preoperative and 5-week postoperative TBUT values of 6.5 and 9.0 seconds,14,23 respectively, with a standard deviation of 4.0, a sample size of 35 patients was calculated. Considering a drop-out rate of 10% to 15%, 40 patients should have been enrolled in this study.
Data analysis was performed using STATA 13.1 software (Stata Corp) and SPSS Statistics Software Package version 19.0 for Windows (SPSS, Inc). Normal distribution between preoperative and postoperative visits of the continuous variables was determined with the Kolmogorov-Smirnov test. The t test was used for parametric analysis. If a parametric analysis was not possible, the comparison of preoperative day 0 and postoperative day 35 after cataract surgery was done with the Wilcoxon signed-rank test. Paired categorical data were evaluated with the exact McNemar test in table 2 × 2.
Continuous data were presented as mean and standard deviation or median and range, whereas categorical data were expressed as percentages and absolute values.
For all statistical tests, a P value of less than .05 was considered statistically significant.
Table 1 shows the mean values of the TBUT, CDVA, Schirmer test, corneal staining score, and intraocular pressure at given visit dates.
Mean TBUT, CDVA, Schirmer Test, Corneal Staining, and IOP Values
At 5 weeks postoperatively, there was a statistically significant increase (P < .001) in the mean TBUT value (13.5 ± 6.7 seconds) compared to the preoperative visit (6.5 ± 1.6 seconds) (Figure A, available in the online version of this article).
Mean values of tear break-up time (TBUT), corneal staining, and Schirmer test measured preoperatively and at 5 weeks postoperatively.
At 5 weeks postoperatively, the mean CDVA value (0.14 ± 0.24 logMAR) improved statistically significantly (P < .001) compared to the preoperative visit (0.41 ± 0.26 logMAR).
Between the preoperative and 5-week postoperative visits, there was no statistically significant difference in the mean Schirmer test values (P = .150) (Figure A).
Corneal Staining Score
The mean total corneal staining score at the 5-week postoperative visit (2.36 ± 2.03) showed statistically significant improvement (P < .004) compared to the preoperative visit (3.53 ± 2.00) (Figure A).
The intraocular pressure did not show any statistically significant change during the trial (P = .3815).
Table 2 shows the scores given by the patients at preoperative and 1 and 5 weeks postoperative visits. With respect to the baseline values at the preoperative visit, all parameters improved statistically significantly at the 5-week postoperative visit (Figure B, available in the online version of this article).
Symptom Assessment in Dry Eye Questionnaire Scores Expressed on a Visual Analog Scale
Visual Analogue Scale questionnaire results as expressed on a visual analog scale at preoperative and 5 weeks postoperative visits.
Subjective Assessment of Tolerability and Effectiveness
Table 3 demonstrates the patient's and physician's assessment of efficacy and tolerability at the 5-week postoperative visit. The tolerability of EvoTears was rated as “impeccable” in 97.4% of patients and physicians, whereas its efficacy was evaluated as “impeccable” or “acceptable” by 89.7% of physicians.
Patient and Physician Assessment of Tolerability and Efficacy at 5-Week Postoperative Visit
A total of 12 adverse events was reported in 8 patients (Table A, available in the online version of this article). Seven adverse events were assessed as being related to the cataract surgery. Two adverse events (one case of skin irritation and one of conjunctival redness) were classified as “not assessable retrospectively” and three adverse events (subjective incompatibility with postoperative eye medication, skin rash, and blepharitis) were classified as “EvoTears suspected of causing adverse event.” None of those was classified as a serious adverse device effect (incident according to applicable legislation).
Surgical interventions such as cataract surgery have been shown to cause damage to the sensory nerves of the cornea, hindering proper neural feedback and leading to a reduced blinking rate and decreased tear secretion.17,25–29 Consequently, patients who already suffer from dry eye disease may show aggravated ocular surface postoperatively.17,28,30 Furthermore, Ishrat et al17 assessed the incidence of dry eye symptoms after cataract surgery in patients who did not show any clinical signs of dry eye disease preoperatively and reported that 42% of patients showed signs of mild to severe dry eye at 1 week postoperatively, suggesting that patients without dry eye disease may also be at risk of developing dry eye symptoms after cataract surgery.
Postoperative dry eye may be induced by a confluence of multiple factors. Phototoxic effects from the light exposure of the operating microscope,27,31,32 elevated levels of inflammatory cytokines in lacrimal tears,33 and the administration of topical anesthesia and a postoperative antibiotic regimen containing preservatives29 are among the factors that may have a negative impact on the stability of the tear film.
Previous studies reported that the meibomian glands may also be affected after cataract surgery.28,34 Park et al34 observed a statistically significant worsening of the meibomian gland parameters including eyelid margin abnormality, meibum expressibility, and meibum quality in patients with dry eye at up to 2 months after cataract surgery. The results were statistically significantly worse than those measured in the group without dry eye. The authors hypothesized that such functional and structural changes of the meibomian glands may have been caused by the postoperative ocular surface inflammation, eyelid dysfunction due to intraoperative placement of an eyelid speculum, and decrease in blink rate triggered by reduced corneal sensation.34 In another study, Kim et al26 assessed the thickness of the tear film lipid layer after cataract surgery to evaluate the impact of surgery on dry eye surface and reported statistically significant thinning of the lipid layer at 1 month postoperatively. Furthermore, the authors observed significantly shorter TBUT, higher OSDI scores, and worse meibum scores,28 reaffirming the importance of the lipid layer in preserving the integrity of the ocular surface.
EvoTears eye drops consist of 100% perfluorohexyloctane. This aliphatic, partly fluorinated hydrocarbon is a chemically and physically inert substance that stabilizes the lipid phase of the tear film.35,36 Numerous studies have evaluated and reported the beneficial effects of EvoTears in patients with dry eye disease.6,11,13,14 In a prospective observational study, Steven et al14 administered EvoTears four times a day for 6 weeks in patients with evaporative dry eye disease and observed significant improvements of the tear film stability, TBUT, and Schirmer I, and a significant reduction of overall corneal staining. In another study, Steven et al13 assessed the effect of perfluorohexyloctane in patients with meibomian gland dysfunction and reported that 6 to 8 weeks of topical application not only led to increased meibum quality, quantity, and expressibility, but also improved TBUT and corneal staining.
Meibomian gland dysfunction is considered the main cause of evaporative dry eye disease1,4,5 and thus restoration of the tear film lipid layer is essential for its treatment. This study evaluated the efficacy of lipophilic, aqueous-free EvoTears as postoperative ocular surface treatment in patients with evaporative dry eye disease undergoing cataract surgery. The results observed in this study were similar to those in the aforementioned studies. The application of EvoTears four times a day for 5 weeks along with the standard postoperative anti-inflammatory regimen led to marked improvement of dry eye disease parameters, particularly TBUT, the mean value of which almost doubled at 5 weeks postoperatively compared to the preoperative value. Moreover, there was a statistically significant reduction of total corneal staining score and statistically significant decrease in all scores of the VAS questionnaire at 5 weeks postoperatively. The Schirmer test showed a slight decrease compared to its preoperative value, yet the difference was not statistically significant.
The positive results observed in this study were also in accordance with the subjective assessment of the patients and physicians. All except one patient rated the tolerability of EvoTears as “impeccable,” whereas all physicians rated its tolerability as either “impeccable” or “acceptable.” Furthermore, 89.7% of physicians rated the efficacy of EvoTears as “impeccable” or “acceptable.”
Overall, this study demonstrated a good safety profile. Of those three adverse events that were suspected to be related to EvoTears, two were considered as minor (skin rash on the eyelid and blepharitis), whereas the third, although also considered minor (incompatibility with postoperative eye medication), led to discontinuation of the treatment due to subjective incompatibility.
The beneficial effect of EvoTears observed in this study may be ascribable to an array of properties compared to the other commercially available artificial tear supplements, of which most are water based. First, perfluorohexyloctane has been shown to possess good spreading abilities37 due to low interfacial tension and thereby reduce friction of the eyelids on the ocular surface with each eye blink.38,39 Because inflammation plays a central role in dry eye disease, less mechanical force on corneal and conjunctival epithelium may help soothe the ocular surface. Furthermore, thanks to its compelling spreading property, a significantly smaller droplet is sufficient to cover the ocular surface,14 which in turn minimizes the blurring effect on vision after each instillation.9 Because the drop size of 10 µL corresponds to the volume of the conjunctival sac, there is no rinsing of the eye after application of EvoTears. Second, perfluorohexyloctane is amphiphilic and able to dissolve lipids, which may contribute to dissolution of thickened meibum that could be blocking the meibomian glands,38,39 resulting in lipid layer stabilization of the tear film. Finally, thanks to its water-free nature, it discourages microbial growth and does not require any preservatives,6,13 allowing patients to administer drops more frequently without having to worry about the potential toxic effects of preservatives.11,12
This study is limited to the extent that it is a prospective open-label study without a control group, which makes it difficult to assess the potential placebo effects. Another limitation is that the steroids applied after cataract surgery may also lead to an improvement in dry eye symptoms and clinical parameters.40 However, this positive effect on dry eye disease parameters may also be “offset” by the ocular surface toxicity caused by the benzalkonium chloride, which is also contained in our standard postoperative topical anti-inflammatory regimen and has been shown to induce tear film instability and dry eye sensation.41,42 Furthermore, fluctuations in subjective assessments due to environmental and seasonal factors cannot be excluded. Longer follow-up periods may also be necessary to determine the long-term benefits of EvoTears in patients with evaporative dry eye disease after ocular surgery. Yet, because an eye is considered to be “recovered from cataract surgery” approximately 5 weeks postoperatively, it is regarded as a “normal” dry eye thereafter. Thus, the long-term observation also corresponds to its clinical efficacy in “normal” patients with dry eye disease.
Our results showed that EvoTears is effective in treating patients with evaporative dry eye disease undergoing cataract surgery, as shown by significant improvements in TBUT, corneal staining, and subjective assessment of dry eye symptoms. Furthermore, both the patients' and physicians' assessment indicated high tolerability and a reliable safety profile, suggesting its suitability in postoperative management of the ocular surface in patients with dry eye disease.
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Mean TBUT, CDVA, Schirmer Test, Corneal Staining, and IOP Valuesa
|Parameter||Preoperative (n = 40)||1 Day Postoperative (n = 40)||1 Week Postoperative (n = 40)||5 Weeks Postoperative (n = 39)||Pb|
|TBUT (seconds)||6.5 ± 1.6||7.9 ± 2.4||9.8 ± 3.4||13.5 ± 6.7||< .001c|
|CDVA (logMAR)||0.41 ± 0.26||0.36 ± 0.29||0.17 ± 0.28||0.14 ± 0.24||< .001c|
|Schirmer test (mm/5 min)||18.18 ± 8.32||–||–||15.77 ± 9.47||.15|
|Corneal staining||3.53 ± 2.00||4.80 ± 2.23||4.38 ± 2.64||2.36 ± 2.03||< .004c|
|IOP (mm Hg)||14.4 ± 2.7||14.4 ± 3.5||14.2 ± 2.6||14.3 ± 4.2||.3815|
Symptom Assessment in Dry Eye Questionnaire Scores Expressed on a Visual Analog Scalea
|Parameter||Preoperative (n = 40)||1 Week Postoperative (n = 40)||5 Weeks Postoperative (n = 39)||Pb|
|Frequency of symptoms||5.5 ± 2.3||4.1 ± 3.2||2.5 ± 2.6||< .001c|
|Severity of symptoms||5.4 ± 2.1||4.5 ± 3.7||2.2 ± 2.3||< .001c|
|Lacrimation||4.2 ± 2.6||3.3 ± 3.3||2.8 ± 4.0||< .001c|
|Feeling of eye pressure||2.4 ± 2.3||1.8 ± 2.4||1.1 ± 1.5||< .001c|
|Burning sensation||3.6 ± 2.4||2.8 ± 2.5||1.5 ± 1.8||< .001c|
|Foreign body sensation||4.4 ± 2.9||4.0 ± 3.8||2.6 ± 3.5||< .002c|
|Mucus formation||1.7 ± 2.3||1.3 ± .0||1.0 ± 2.0||< .0016c|
|Itching||3.4 ± 2.5||2.0 ± 1.9||1.2 ± 1.6||< .001c|
Patient and Physician Assessment of Tolerability and Efficacy at 5-Week Postoperative Visit
|Parameter||Patient Tolerability||Physician Tolerability||Physician Efficacy|
|Impeccable||38 (97.4%)||38 (97.4%)||25 (64.1%)|
|Acceptable||0 (0.0%)||1 (2.6%)||10 (25.6%)|
|Not acceptable||1 (2.6%)||0 (0.0%)||4 (10.3%)|
|Patient No.||Event||Severity||Drops Suspected of Causing Adverse Event||Treatment Continued?|
|1||Skin irritation||Minor||Not assessable retrospectively||Yes|
|2||Conjunctival redness||Minor||Not assessable retrospectively||Yes|
|2||Damaged teeth during anesthesia induction||Severe||No||Yes|
|4||Open posterior capsule||Minor||No||Yes|
|4||Postoperative corneal edema||Minor||No||Yes|
|5||Intraocular pressure increase||Minor||No||Yes|
|5||Corneal erosion minor||No||Yes|
|5||Intraocular pressure increase medication||Minor||No||Yes|
|6||Incompatibility with postoperative eye||Minor||Yes||No|
|7||Skin rash (on the eyelid)||Minor||Yes||Yes|