Tear Film Characteristics Research Articles

Rationale for 24-hour management of dry eye disease: A review.

The symptom severity of patients with dry eye disease (DED) varies over a 24-hour period. It is typically worse upon waking than later in the morning and deteriorates towards the evening. Substantial differences in the characteristics and physical properties of the tear film, such as levels of inflammation, pH, osmolarity, volume and stability, also exist between night (sleeping) and day (waking), and over the course of the day itself. Data on diurnal variation in symptom severity and tear film characteristics have been reviewed to recommend a management strategy that supports the various needs of patients with DED over a full 24-hour period. Treatment strategies for DED must be matched to the variations in the severity of DED and to the environments that eyes are subjected to over a 24-hour period. While artificial tears are used to moisturise the ocular surface and reduce damage to the corneal epithelium during the day, gels are used at night-time; they are more viscous and have a longer ocular surface retention time than artificial tears. Several combinations of these products are currently available in tandem to support the 24-hour variation in tear film characteristics. The present review of published literature provides evidence that the approach of the daytime use of artificial tears to protect the eye from aggravating environmental factors in combination with the night-time use of gels to relieve more severe symptomatology. This, in turn, should provide optimal 'around-the-clock' DED management.

Predictive Potential of Eyelids and Tear Film in Determining Symptoms in Contact Lens Wearers.

Early diagnosis of clinical markers of contact lens discomfort can help clinicians set realistic expectations and monitor and provide prophylactic management for contact lens wearers. The purpose of this study was to evaluate the potential of eyelid- and tear film-related clinical markers to be used as predictive factors for diagnosing discomfort in contact lens wearers. A cross-sectional study was performed on 30 contact lens wearers (6 male, 24 female) with median age of 23 years (range, 18 to 41 years). Eyelid signs and tear film characteristics were evaluated during a single visit, and subjects completed the Contact Lens Dry Eye Questionnaire to evaluate ocular discomfort. Area under the curve (AUC) statistics and sensitivity and specificity values from receiver operating characteristic curves were analyzed to evaluate the predictive potential of clinical signs in discriminating symptoms of contact lens discomfort. The presence of foam at meibomian gland orifices (AUC, 0.944; P < .05; sensitivity >0.7), meibomian gland secretion volume (AUC, 0.935; P < .05; sensitivity >0.7), quality (AUC, 0.969; P < .05; sensitivity >0.7), and expressibility (AUC, 0.933; P < .05; sensitivity >0.7) were significant and strong predictors of discomfort in lens wear. Tear evaporation rates with (AUC, 0.779; P < .05; sensitivity >0.7) or without contact lenses (AUC, 0.788; P < .05; sensitivity >0.7), palpebral conjunctival roughness (AUC, 0.859; P < .05; sensitivity >0.7), palpebral conjunctival staining (AUC, 0.817; P < .05; sensitivity >0.7), palpebral conjunctival hyperemia (AUC, 0.746; P < .05; sensitivity >0.7), meibomian gland orifice capping (AUC, 0.873; P < .05; sensitivity >0.7), pouting (AUC, 0.891; P < .05; sensitivity >0.7), and lid-parallel conjunctival folds (AUC, 0.770; P < .05; sensitivity >0.7) were other acceptable discriminators of symptoms of discomfort during contact lens wear. An equation was developed to identify symptomatic from asymptomatic lens wearers based on the significant predictors: Symptom discriminant function score = 3.378 (meibomian gland secretion grade) + 0.224 (meibomian gland morphology grade) + 0.61 (tear evaporation rate without contact lenses) + 0.439 (lid-parallel conjunctival folds grade) - 0.346 (palpebral conjunctival health grade) - 4.625. This study demonstrated that clinical signs related to meibomian gland secretions and morphology, tear evaporation, lid-parallel conjunctival folds, and palpebral conjunctival health may successfully predict symptoms of discomfort in contact lens wearers.

Influence of Nasal Tear Osmolarity on Ocular Symptoms Related to Dry Eye Disease

To investigate relationships between local tear osmolarity and tear film characteristics and dry eye disease (DED) symptoms. Prospective, cross-sectional, observational study. Nasal and temporal tear osmolarity were measured in subjects with DED. The difference between nasal and temporal tears (OSM difference) was then calculated. Ocular symptoms were evaluated and tear break-up time (TBUT), corneal fluorescein staining score (CFSS), eyelid hyperemia, and tear production were measured. Correlations between DED symptoms and nasal tear osmolarity, temporal tear osmolarity, OSM difference, and tear film characteristics were evaluated using Pearson correlation analyses. Subjects were divided into 3 groups based on OSM difference: the temporal group had a temporal osmolarity > nasal osmolarity, the nasal group had a temporal osmolarity < nasal osmolarity, and the equal group had an OSM difference < 10 mOsm/L. Forty-eight eyes of 48 subjects were included. Eleven eyes were in the temporal group, 17 eyes were in the equal group, and 20 eyes were in the nasal group. Temporal osmolarity, nasal osmolarity, and OSM difference were not correlated with TBUT, CFSS, lid hyperemia, or tear production. Nasal tear osmolarity was correlated with cold sensitivity frequency (r= 0.298, P= .040), foreign body sensation severity (r= 0.293, P= .043), and light sensitivity severity (r= 0.293, P= .043). Additionally, OSM difference was correlated with daily symptom frequency (r= 0.339, P= .019). Nasal tear osmolarity and OSM difference play an important role in DED symptoms. Lid hyperemia, TBUT, CFSS, and tear secretion volume are not significantly affected by tear osmolarity. It is important to measure both nasal and temporal tear osmolarity when evaluating patients with DED.

Comparison of tear film characteristics between Kajal (Kohl) users and Non-Users

Aim: To determine the effect of applying Kajal (an eye cosmetic) over the eye lids on tear film stability and quantity. Methods: Non-invasive tear break-up time and Schirmer test were performed on 46 female subjects (23 Kajal users and 23 non-Kajal users). All measurements were performed in the morning. Results: Quantity of the tear film was not altered with Kajal use but the stability of tear film was significantly lower in the Kajal wearing group (p<0.001). Conclusion: Present study demonstrates that application of Kajal as cosmetic over the eye lid margins can reduce the tear film stability.

Ocular surface and tear film status among contact lens wearers and non-wearers who use VDT at work: comparing three different lens types.

To analyze differences in the ocular surface appearance and tear film status of contact lens wearers and non-wearers in a group of visual display terminals (VDT) workers and additionally to assess differences between lens materials. Cross-sectional study of 236 office workers, of whom 92 were contact lens wearers. Workers provided information on their contact lenses (conventional hydrogel, silicone hydrogel or rigid gas permeable lenses) and exposure to VDT at work. Ocular surface and tear film status were determined by the presence of bulbar, limbal and lid redness, lid roughness and corneal staining type, and by Schirmer's and tear break-up time tests (TBUT). A generalized linear model was used to calculate the crude (cRR) and age- and sex-adjusted (aRR) relative risk to measure the association between ocular surface and tear film abnormalities and contact lens use and type. The aRR of ocular surface abnormalities was higher in contact lens wearers compared to non-wearers: bulbar redness (aRR 1.69; 95% CI 1.25-2.30), limbal redness (aRR 2.87; 1.88-4.37), lid redness (aRR 2.53; 1.35-4.73) and lid roughness (aRR 7.03; 1.31-37.82). VDT exposure > 4h/day increased wearers' risk of limbal and lid redness. Conventional hydrogel wearers had the highest risk of ocular surface abnormalities, followed by silicone hydrogel wearers. Both contact and non-contact lens wearers had a high prevalence of altered TBUT (77.3 and 75.7% respectively) and Schirmer (51.8 and 41.3%). Regular contact lens use during VDT exposure at work increases risk of bulbar, limbal and lid redness, and lid roughness, especially in soft contact lens wearers. The high prevalence of altered TBUT and Schirmer's results in all participants suggests that VDT use greatly affects tear film characteristics.

Non-invasive pre-lens tear film assessment with high-speed videokeratoscopy.

To evaluate the effect of two types of daily contact lenses (delefilcon A and omafilcon A) on the tear film and establish whether it is dependent on pre-corneal tear film characteristics using a new method to analyse high-speed videokeratoscopy recordings, as well as to determine the sensitivity of the method in differentiating between contact lens materials on eye. High-speed videokeratoscopy recordings were analysed using a custom made automated algorithm based on a fractal dimension approach that provides a set of parameters directly related to tear film stability. Fifty-four subjects participated in the study. Baseline measurements, in suppressed and natural blinking conditions, were taken before subjects were fitted with two different daily contact lenses and after four hours of contact lens wear. The method for analysing the stability of the tear film provides alternative parameters to the non-invasive break up time to assess the quality of the pre-corneal and pre-lens tear film. Both contact lenses significantly decreased the quality of the tear film in suppressed and natural blinking conditions (p<0.001). The utilised method was able to distinguish between contact lens materials on eye in suppressed blinking conditions. The pre-corneal tear film characteristics were not correlated with the decrease in pre-lens tear film quality. High-speed videokeratoscopy equipped with an automated method to analyse the dynamics of the tear film is able to distinguish between contact lens materials in vivo. Incorporating the assessment of pre-lens tear film to the clinical practice could aid improving contact lens fitting and understand contact lens comfort.

A Confocal Fluorescence Microscopy Method for Measuring Mucous Layer Growth on Living Corneal Epithelia

Mucous layers at corneal epithelial cell surfaces perform a variety of tribological roles and are integral to the function of associated biological structures. The primary component of these layers are mucin glycosylated proteins, a broad and diverse class of biological macromolecules that influence tribological and rheological characteristics of the eye's tear film. The tear film composition is incessantly modulated by environmental conditions, active production by living cells, and passive processes such as degradation or wear. Quantitative investigation of mucin production and accumulation at the corneal surface will improve current understanding of tear film stability and function. Here, we present fluorescence microscopy and image analysis techniques capable of capturing the dynamics of mucous layer growth. Using this technique, we observe a non-monotonically thickening mucin layer at the apical surface of a corneal epithelial cell monolayer, while the total amount of mucin increases at a rate indicative of diffusion limited growth.

Effect of orthokeratology on tear film and cornea biological characteristics

Effect of orthokeratology on tear film and cornea biological characteristics

Changes in Tear Film Characteristics in Patients With Idiopathic Dacryoadenitis.

To evaluate the tear-film meniscus with optical coherence tomography (OCT) in patients with idiopathic dacryoadenitis and to determine its relationships with the clinical tests. Sixteen patients with unilateral idiopathic dacryoadenitis were included in the study. Patients with idiopathic dacryoadenitis with affected sites (group 1), with contralateral sites (group 2) and healthy participants (group 3) completed the ocular surface disease index before optical coherence tomography determination of tear meniscus height and tear meniscus area. These were followed by measurements of tear breakup time, fluorescein staining, and Schirmer test. Finally, surgical debulking or incisional biopsies were conducted. Tear meniscus height and tear meniscus area were the lowest in patients with affected sites (group 1) among the 3 groups (p < 0.05). Breakup time was the shortest in group 1 (p < 0.05). In the group 1, breakup time, fluorescein staining score, and histopathological phases were significantly correlated with tear meniscus height and tear meniscus area (p < 0.05). Tear function was significantly disturbed in idiopathic dacryoadenitis. Tear menisci volumes measured by optical coherence tomography may assess the tearing function in patients with idiopathic dacryoadenitis.

Effect of Omega-3 Fatty Acids Dietary Supplementation on Ocular Surface and Tear Film in Diabetic Patients with Dry Eye

Objective: The objective of this study was to investigate the effect of dietary supplementation with omega-3 fatty acids on ocular surface and tear film in patients with type 2 diabetes suffering from dry eye.Methods: Thirty-six patients suffering from type 2 diabetes and moderate to severe dry eye syndrome were included in the study. Patients were assigned to receive omega-3 long-chain polyunsaturated fatty acids for 3 months. Tear film break-up time test, Schirmer-I test, and conjunctival impression cytology analysis were performed on all patients at baseline and after 1 and 3 months. The subjective symptoms of dry eye were evaluated with the Ocular Surface Disease Index (OSDI) questionnaire at the same time points.Results: Patients’ average age was 65.57 ± 4.27 years and the mean duration of diabetes was 14.85 ± 5.4 years. There was a statistically significant increase in Schirmer-I test results and tear break-up time score after 3 months of supplementary intake of omega-3 fatty acids compared to baseline (p < 0.05 and p < 0.001, respectively). Impression cytology demonstrated a significantly lower grade of conjunctival squamous cell metaplasia after 1 and 3 months of omega-3 fatty acids intake compared to baseline (p < 0.05 and p < 0.01, respectively). The OSDI score was statistically significant lower both at 1 and 3 months after omega-3 fatty acids supplementation compared to baseline (p < 0.001).Conclusions: Omega-3 fatty acids may effectively improve tear film characteristics, reverse ocular surface features, and alleviate the subjective symptoms associated with dry eye syndrome in patients with type 2 diabetes.

Effect of Ambient Temperature on the Human Tear Film.

During everyday life, the tear film is exposed to a wide range of ambient temperatures. This study aims to investigate the effect of ambient temperature on tear film physiology. A controlled environment chamber was used to create different ambient temperatures (5, 10, 15, 20, and 25°C) at a constant relative humidity of 40%. Subjects attended for two separate visits and were exposed to 25, 20, and 15°C at one visit and to 10 and 5°C at the other visit. The subjects were exposed to each room temperature for 10 min before investigating tear film parameters. The order of the visits was random. Tear physiology parameters assessed were tear evaporation rate, noninvasive tear break-up time (NITBUT), lipid layer thickness (LLT), and ocular surface temperature (OST). Each parameter was assessed under each condition. A threefold increase in tear evaporation rate was observed as ambient temperature increased to 25°C (P=0.00). The mean evaporation rate increased from 0.056 μL/min at 5°C to 0.17 μL/min at 25°C. The mean NITBUT increased from 7.31 sec at 5°C to 12.35 sec at 25°C (P=0.01). A significant change in LLT was also observed (P=0.00), LLT median ranged between 20 and 40 nm at 5 and 10°C and increased to 40 and 90 nm at 15, 20, and 25°C. Mean reduction of 4°C OST was observed as ambient temperature decreased from 25 to 5°C. Ambient temperature has a considerable effect on human tear film characteristics. Tear evaporation rate, tear LLT, tear stability, and OST were considerably affected by ambient temperature. Chronic exposure to low ambient temperature would likely result in symptoms of dry eye and ultimately ocular surface disorders.

Chronic dry eye in photorefractive keratectomy and laser in situ keratomileusis: Manifestations, incidence, and predictive factors

To evaluate dry-eye manifestations after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) and determine the incidence and predictive factors of chronic dry eye using a set of dry-eye criteria. Walter Reed Army Medical Center, Washington, DC, USA. Prospective, non-randomized clinical study. Dry-eye evaluation was performed before and after surgery. Main outcome measures included dry-eye manifestations, incidence, and predictive factors of chronic dry eye. This study comprised 143 active-duty U.S. Army personnel, ages 29.9 ± 5.2 years, with myopia or myopic astigmatism (manifest spherical equivalent -3.83 ± 1.96 diopters) having PRK or LASIK. Schirmer scores, corneal sensitivity, ocular surface staining, surface regularity index, and responses to dry-eye questionnaire significantly changed over time after PRK. After LASIK, significant changes were observed in tear breakup time, corneal sensitivity, ocular surface staining, and responses to questionnaire. Twelve months postoperatively, 5.0% of PRK and 0.8% of LASIK participants developed chronic dry eye. Regression analysis showed that pre-operatively lower Schirmer score will significantly influence development of chronic dry eye after PRK, whereas preoperatively, lower Schirmer score or higher ocular surface staining score will significantly influence the occurrence of chronic dry eye after LASIK. Chronic dry eye was uncommon after PRK and LASIK. Ocular surface and tear-film characteristics during pre-operative examination might help to predict chronic dry-eye development in PRK and LASIK. The authors have no financial interest in any product, drug, instrument, or equipment discussed in this manuscript.

Change in tear film characteristics in visual display terminal users.

To evaluate changes in symptoms and tear film characteristics in young computer users. Fifty-one computer users and 26 controls were evaluated at the beginning and the end of the working day. Subjects with ocular or systemic disease, history of ocular surgery, use of contact lenses or glasses with antireflective surfaces, and use of topical or systemic medications were excluded from the study. Computer use duration, Ocular Surface Disease Index (OSDI) questionnaire, tear osmolarity, Schirmer test, tear break-up time (TBUT), and ocular surface vital dye staining were performed prevocationally and postvocationally. The mean age was 31.2 ± 6.3 years in computer users and 33.7 ± 5.8 in controls. The mean reported computer use was 6.9 ± 2.7 hours/day in computer users and 0.4 ± 0.5 hours/day in controls. The mean prevocational and postvocational values in computer users for OSDI, osmolarity, TBUT, and Schirmer test were 23.2 ± 16.6 and 27.0 ± 17.6, 306.6 ± 14.9 and 311.0 ± 12.5 mOsm/L, 13.9 ± 4.0 and 13.2 ± 3.8 seconds, 22.7 ± 11.8 and 20.6 ± 12.5 mm, respectively. The vocational change was significant for all parameters in the computer user group but not in the control group. The osmolarity-based dry eye diagnosis was 27.4% in the computer users while it was 15.4% in the control group. Oxford score was only grade 1 in 5.9% of visual display terminal users and did not change at the end of the day. Both symptoms and signs of dry eye increased significantly with computer use. Approximately 1 of every 3-4 computer users was found to have dry eye with higher tear osmolarity values.

Dry Eye Syndrome in Non-Exophthalmic Graves’ Disease

ABSTRACTBackground: The present study aims to assess qualitative and quantitative characteristics of tear film and corneal related impairment and to evaluate the quality of life in a cohort of non-exophthalmic Graves’ disease (GD) patients. Methods: The series comprised 50 eyes from 25 newly diagnosed GD patients with no proptosis. As control group, 56 eyes of 28 thyroid disease-free subjects were enrolled. Results: The results of Schirmer I and II, break-up time, and Oxford scheme showed a significant difference between GD and controls. By ocular surface disease index (OSDI) questionnaire, eleven (44%) GD patients had normal ocular surface, while two (8%) had mild, four (16%) had moderate, and eight (32%) had severe dry eye. The mean score of the OSDI in the GD group was significantly (p < 0.001) higher with respect to the control group. Conclusions: This study shows that the tear film and cornea are damaged in newly non-exophthalmic GD subjects.

Characteristics of, prevalence of, and risk factors for corneal pigmentation (pigmentary keratopathy) in Pugs

To determine the characteristics of, prevalence of, and risk factors for corneal pigmentation (CP) in Pugs. Prospective cross-sectional study. 295 Pugs > 16 weeks old. Ophthalmic examination of the anterior segment of each eye was performed, including determination of tear film characteristics (Schirmer tear test and tear film breakup time) and corneal sensitivity. Digital photographs of the head and each eye were obtained. Corneal pigmentation of eyes was graded as absent, very mild, mild, moderate, or severe. Signalment and medical history information and American Kennel Club registration status were recorded. Results-CP was detected in at least 1 eye of 243 of the 295 (82.4%) Pugs; CP was typically very mild or mild. Detection of CP was not significantly associated with coat color, age, eyelid conformation, or tear film characteristics but was significantly associated with sex of dogs. The severity of CP was not significantly associated with American Kennel Club registration status or age, but was significantly associated with sex, tear film characteristics, and coat color. Iris hypoplasia was detected in 72.1% of the Pugs. Iris-to-iris persistent pupillary membranes were detected in 85.3% of the Pugs. Prevalence of CP in Pugs in this study was high. Unexpectedly high prevalences of iris hypoplasia and persistent pupillary membranes were also identified. The condition identified in these Pugs was a pigmentary keratopathy, rather than pigmentary keratitis or corneal melanosis. This condition may have a genetic basis, and further studies are warranted to determine etiology.

Relation Between Upper and Lower Lids' Meibomian Gland Morphology, Tear Film, and Dry Eye

To analyze relations between upper lid (UL) and lower lid (LL) meibomian gland (MG) morphology and tear film and the MG criteria ability to predict dry eye. MG, lipid layer, and non-invasive break-up time (NIBUT) were evaluated of the OD of 20 randomly selected subjects (female = 10; median age = 44.5 years, interquartiles = 39.5 to 55 years). Subjects were grouped into nine Ocular Surface Disease Index (OSDI)- and 11 OSDI+ by the OSDI. Non-contact infrared meibography and image analysis were performed to evaluate MG loss, MG thickness, and MG bent angle. MG loss (Pearson correlation; r = 0.647, p = 0.003) and MG bent angle (r = 0.489, p = 0.027) were significantly correlated between lids, but MG thickness was not (r = -0.059, p = 0.413). MG loss was significantly (t-test; p = 0.048) less in the UL (median = 26.9%; LL = 32.3%), thicker in the LL (p < 0.001) and were more bent in the LL (p = 0.001). MG loss was significantly correlated to lipid-layer thickness (r < -0.597, p < 0.003) and NIBUT (r < -0.453, p < 0.030), whereas MG thickness and bent angle of the UL only were related to NIBUT (r < -0.563, p < 0.018). Combining MG loss of both lids (linear regression analysis) resulted in the best predictive ability of OSDI± (area under the receiver operative characteristic curve = 0.929, p = 0.001). MG scores between lids were significantly different but correlated. MG loss was significantly correlated to tear film characteristics including lipid layer thickness and stability. MG thickness and bent angle of the UL were related to NIBUT. The combination of both lids' MG loss showed best predictive ability of dry eye.

A Novel On-Eye Wettability Analyzer for Soft Contact Lenses

To develop novel methodology to assess two in vivo wettability parameters, contact angle and index of liquid spreading (ILS), for hydrogel contact lenses and to provide a comprehensive investigation of the measurement errors (repeatability) associated with these two parameters. A Novel On-eye Wettability Analyzer (NOWA) was constructed which delivered a drop of 0.4% sodium hyaluronate mixed with sodium fluorescein directly on to a lens surface in vivo while a two-camera digital system recorded both the resultant contact angle and liquid spreading. Ten subjects each wore a different etafilcon A lens (-0.50 DS) in the right eye for 30 min before measurement on three separate occasions. For contact angles, the coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intrasubject COR, and intersubject COR) was determined. For ILS, the COR associated with two measurement conditions (intrasubject COR and intersubject COR) was also determined. The in vivo contact angle for the etafilcon A lens was 19.8° ± 2.9° (mean ± standard deviation). COR values for contact angle were 3.2°, 5.2°, and 8.0° for image analysis, intrasubject measures, and intersubject measures, respectively. The mean ± standard deviation ILS was 2.0 ± 0.3 mm, and COR values were 0.4 and 0.8 mm for intrasubject and intersubject measures, respectively. This research demonstrates that it is possible to obtain hydrogel lens contact angles in vivo and to provide a new wettability parameter (ILS) with the NOWA instrumentation. The COR values obtained were considered to be acceptable. Intersubject COR values were greater than intrasubject COR values for both contact angle and ILS; this is likely to be due to greater variability of tear film characteristics between subjects than within an individual. The use of this novel methodology and its associated clinical parameters across a wider range of lens types in various clinical situations warrants further investigation.

Effect of a liposomal spray on the pre-ocular tear film

With the potential to address evaporative dry eye, a novel spray has been developed in which phospholipid liposomes are delivered to the tear film via the surface of the closed eyelid. This study evaluated the short-term effects of liposomal spray application on the lipid and stability characteristics of the pre-ocular tear film in normal eyes. Twenty-two subjects (12M, 10F) aged 35.1+/-7.1 years participated in this prospective, randomised, double-masked investigation in which the liposomal spray was applied to one eye, and an equal volume of saline spray (control) applied to the contralateral eye. Lipid layer grade (LLG), non-invasive tear film stability (NIBUT) and tear meniscus height (TMH) were evaluated at baseline, and at 30, 60, 90 and 135min post-application. Subjective reports of comfort were also compared. Treated and control eyes were not significantly different at baseline (p>0.05). Post-application, LLG increased significantly, at 30 and 60min, only in the treated eyes (p=0.005). NIBUT also increased significantly in the treated eyes only (p<0.001), at 30, 60 and 90min. TMH did not alter significantly (p>0.05). Comfort improved relative to baseline in 46% of treated and 18% of control eyes, at 30min post-application. Of those expressing a preference in comfort between the eyes, 68% preferred the liposomal spray. Consistent with subjective reports of improved comfort, statistically and clinically significant improvements in lipid layer thickness and tear film stability are observed in normal eyes for > or =1h after a single application of a phospholipid liposomal spray.

Effect of castor oil emulsion eyedrops on tear film composition and stability

An emulsion eyedrop containing castor oil has been shown to modify the tear film lipid layer and increase tear film stability. The primary objectives of this investigation were to measure the prevalence of castor oil in the tear fluid over time and quantify the effects on the lipid layer. A secondary objective was to quantify the initial effects on ocular symptomatology. The investigation was an open label pilot study on 5 normal and 10 dry eye subjects. A single eyedrop (Castor oil emulsion, Allergan) was instilled in each eye; the tear film appearance and composition were monitored for 4h via in vivo visualisation using the Tearscope and post in vivo tear samples analysis by HPLC. Combined results for both normal and dry eye subjects showed that castor oil was detected up to 4h after a single eyedrop instillation and associated with an increase in the level of tear film lipid. The relative amount of various lipid families was also changed. An increase in tear lipid layer thickness was significant up to one hour post-instillation for the symptomatic sub-population. The changes in tear film characteristics were associated with significantly lower symptoms up to four hours post-instillation for the symptomatic sub-population. This pilot investigation showed that castor oil eyedrops achieved a residence time of at least four hours post-instillation, producing a more stable tear film and an associated significant decrease in ocular symptoms over the entire follow-up period for the symptomatic subjects.

The effect of soft contact lens wear and time from blink on wavefront aberration measurement variation

Introduction: Advances in contact lens design technology allow incorporation of correction of higher‐order aberrations to improve or manipulate the eye's optical quality. Repeatability of aberration measurements in vivo with contact lens wear has not been established.Method: Higher‐order aberrations were measured using the COAS aberrometer (Wavefront Sciences, USA) in 23 participants who were free from external eye pathology. Cycloplegia with 1% Cyclopentolate HCl ensured control of accommodation and that pupil diameters exceeded analysis diameter. Tear film characteristics were assessed with the phenol red thread test and Keeler Tearscope. Variability in wavefront aberrations was assessed with and without a low powered soft contact lens. The effect of time after the blink and tear film characteristics were also investigated.Results: Standard deviations differed significantly for some fifth‐order terms (p ≤ 0.003) with contact lens wear. Coefficient of variation did not increase significantly with contact lens wear. Time from blink increased standard deviations in the third‐order (p ≤ 0.003). The effect of contact lens wear and time from blink differed between groups with different tear film characteristics.Conclusions: Variability in measurements of aberrations increased significantly for odd‐order aberrations when a contact lens was worn or between blinks. Fourth‐order aberrations showed less effect of contact lens wear. Therefore, verification of the performance of lenses with aspheric optics on eye is feasible. Accurate assessment of higher‐order aberrations is more difficult when a contact lens is worn. Both contact lens wear and time from blink increase variability in aberrations, which suggests a role for the tear film in increased aberrations with soft contact lens wear.