Efficacy of hydroxypropyl-guar drops in improving tear film index and ocular surface dynamics using two treatment methods under a controlled desiccating environment.

AIM: This study aimed to assess the efficacy of hp-guar eye drops on tear film index and ocular surface dynamics under desiccating conditions using protection and relief treatment modalities. METHODOLOGY: The 12 normal, non-dry eye participants were subjected to adverse environmental conditions using a Controlled Environment Chamber (CEC) where the relative humidity (RH) was 5% and the ambient temperature was 21 °C. The participants were screened for ocular symptoms, tear osmolarity, ocular surface temperature (OST), tear production using the Ocular Surface Disease Index questionnaire (OSDI), OcuSense TearLab Osmometer, FLIR System ThermaCAM P620, and Schirmer strips. Tear production was calculated by the Tear Function Index test (TFI). RESULTS: The mean tear film osmolarity decreased significantly from 296 mOsm/L at 40% RH to 285 mOsm/L at 5% RH (p = 0.01). Conflicting responses were seen for osmolarity in protection and relief. Mean tear osmolarity was significantly higher in the protection method in comparison to the relief method (p = 0.005). The mean TFI increased from 557 at 40% to 854 at 5% (p = 0.02). A significant increase in TFI was observed in the relief method in comparison with both 40% (p = 0.001) and 5% (p = 0.04). In the relief method, the mean TFI score went up to 1139 when hp-guar was installed. A significant improvement in ocular comfort was experienced in both the protection (p = 0.041) and relief (p = 0.010) methods at 5% RH. The instillation of hp-guar drops in the relief method resulted in a significant reduction in OST. The mean OST dropped to 33.01 ºC, significantly lower than the recorded OST for both normal (p = 0.040) and dry (p = 0.014) environmental conditions. CONCLUSION: Hp-guar drops significantly improve tear film parameters under a desiccating environment, however, tear film parameters respond differently to the management modalities. In the protection method, tear film osmolarity was protected against a dry environment, while in the relief mode, an improvement in tear production and a decrease in ocular surface temperature were seen. Hp-guar performance could be maximized for the management of exposure to adverse environments by using a treatment protocol that targets the most affected parameters in each group of patients. Using CEC has the potential to provide researchers with a readily available method to evaluate the efficiency of tear supplementation.

Evaluation of therapeutic efficacy of Emustil drops for ocular discomfort and tear film osmolarity using different treatment management modes under dry environmental conditions.

BACKGROUND: We aimed to check the efficacy of Emustil (oil in water emulsion) drops on tear film index and ocular surface dynamics in dry environments through protection and relief treatment modalities. METHODS: The subjects were exposed to a dry environment using a Controlled Environment Chamber (CEC) where the relative humidity (RH) was 5% and the temperature was 21 °C and screened for ocular symptoms, tear osmolarity, ocular surface temperature (OST) and tear production using ocular Surface Disease Index questionnaire (OSDI), OcuSense TearLab Osmometer, FLIR System ThermaCAM P620 and Schirmer strips/phenol red test respectively. Tear production was calculated by the Tear Function Index test (TFI). RESULTS: The mean tear film osmolarity decreased significantly from 296.8 mOsm/l at 40% RH to 291 mOsm/l at 5%. (p = 0.01). Instillation of Emustil resulted in a significant increase in tear osmolarity in the relief method compared with osmolarity seen at 5% RH when no drop was used. The mean PRT value decreased from 26 ± 9 in normal conditions (40% RH) to 22 ± 4 mm in dry conditions (5% RH). Emustil drops did not induce any significant change in tear production in the PRT test. No significant change was found in OST following exposure to 5% RH. OST did not show a statistically significant change with the emulsion when used for relief (p > 0.05). The mean score of ocular discomfort observed was 70 at 5% RH. Still, the instillation of the oil-in-water emulsion (Emustil) resulted in a noticeable decrease in visual discomfort to 37 (p = 0.00) in protection and 59 in relief (p = 0.05). Emustil drops substantially improved tear film parameters under a desiccating environment, however, tear film parameters respond differently to the management modalities. In the protection method, tear film osmolarity was protected against a dry environment, while in the relief mode, tear production was improved. CONCLUSION: CEC allows for a thorough evaluation of tear film parameters and dry eye treatment protocols in labs, providing greater confidence when applying them to patients. In addition, our study showed that Emustil not only provides protection and relief for dry eyes but also helps to maintain ocular homeostasis in desiccating environments. This indicates a promising potential for improving dry eye treatment protocols.

Protecting Tear-Film Stability under Adverse Environmental Conditions Using a Mucomimetic with a Non-Newtonian Viscosity Agent.

Background and Objectives: Tamarind-seed polysaccharide (TSP) and hyaluronic acid (HA) have mucoadhesive properties that improve drug absorption and delay in drug elimination from the ocular surface. We aimed to evaluate TSP/HA-containing formulation for its efficiency in dry-eye symptoms induced by adverse environments and the interaction between mucomimic polymer and tear-film parameters. Materials and Methods: The participants were exposed to 5% relative humidity (RH) in a Controlled Environment Chamber (CEC) under constant room temperature (21 °C). Tear-film parameters were assessed at 40% RH and 5% RH. Rohto Dry Eye Relief drops were used in the two treatment modalities, protection (drops instilled before exposure to the dry environment) and relief (drops instilled after exposure to the dry environment). The HIRCAL grid, Servomed EP3 Evaporimeter, and Keeler's TearScope-Plus were used to screen for non-invasive tear break-up time (NITBUT), tear evaporation rate, and lipid-layer thickness (LLT) using protection and relief treatment methodology. Results: LLT was found to be significantly thinner at 5% RH compared with at 40% RH (p = 0.007). The median LLT dropped from 50-70 nm (grade 3) at 40% RH to 10-50 nm (grade 2) at 5% RH. TSP/HA eye drops significantly augment LLT in both treatment modalities, protection (p = 0.01) and relief (p = 0.004) at 5% RH. The mean evaporation rate doubled from 40.93 at 40% RH to 82.42 g/m2/h after exposure to 5% RH. In protection mode, the TSP/HA allowed the average evaporation rate to be much lower than when no TSP/HA was used at 5% RH (p < 0.008). No alteration in evaporation rate was recorded when the TSP/HA drop was used after exposure (relief). The mean NITBUT was reduced from 13 s in normal conditions to 6 s in the dry environment. Instillation of TSP/HA eye drops resulted in significant improvement (p = 0.006) in tear stability, where the NITBUT increased to 8 s in both protection (before exposure) and relief (after exposure) (p = 0.001). Although improved, these values were still significantly lower than NITBUT observed at 40% RH. Conclusions: Significant protection of tear-film parameters was recorded post instillation of TSP/HA eye drop under a desiccating environment. Both treatment methods (protection and relief) were shown to be effective. The presence of TSP/HA enhances the effectiveness of teardrops in protecting the tear-film parameters when exposed to adverse environments.

Strip meniscometry tube: a rapid method for assessing aqueous deficient dry eye.

BACKGROUND: The aim of this study was to investigate the utility of strip meniscometry tube (SMTube) for the quantitative assessment of the tear film, by comparing it to measurements of tear turnover rate using the gold standard method, fluorophotometry. Also, to determine the viability of this test as a diagnostic tool for aqueous deficient dry eye (ADDE), to inform appropriate clinical management. METHODS: Thirty-two participants (15 ADDE; 17 non-ADDE) were recruited. Tear turnover rate of the right eye of each subject was conducted with an automated scanning fluorophotometer and SMTube test was conducted. Tear meniscus height was assessed using a slitlamp biomicroscope and eyepiece graticule. RESULTS: Significant differences between the ADDE and the non-ADDE groups were found for all measures: tear turnover rate 7.9 ± 1.8 versus 19.6 ± 5.9 per cent/minute (p < 0.001), SMTube 3.2 ± 1.1 versus 5.7 ± 2.3 mm (p = 0.001) and tear meniscus height 0.18 ± 0.05 versus 0.23 ± 0.04 mm (p = 0.004). Moreover, significant correlations were found between tear turnover rate and SMTube (rho = 0.78, p < 0.001), tear turnover rate and tear meniscus height (rho = 0.54, p < 0.001) and SMTube and tear meniscus height (rho = 0.47, p < 0.01). Using a receiver operating characteristic curve, SMTube showed a sensitivity of 67 per cent and a specificity of 88 per cent for the diagnosis of ADDE. CONCLUSION: Given its performance, availability, speed and the fact it is relatively cheap, the study shows that the SMTube can be used as an alternative to fluorophotometry to assess tear production. It appears from the results that SMTube is a viable minimally invasive test for the diagnosis of ADDE.

Effect of tear supplements on signs, symptoms and inflammatory markers in dry eye.

PURPOSE: Three tear supplements were compared for their effects on the signs, symptoms and inflammatory status of subjects with dry eye disease. Assessments were made before and after both 2 and 4 weeks of treatment. METHODS: In this masked, randomized, 3-way crossover trial, eighteen dry eye subjects were recruited. At each visit, symptoms, tear evaporation rate, stability and osmolarity were measured and tear samples were analyzed for 7 inflammatory markers, using multiplex immunoassays. The 3 treatments included carboxymethylcellulose-glycerine-castor oil (CGC), carboxymethylcellulose (CMC) and hydroxypropyl guar (HPG). The CGC and HPG drops are emulsified lipids; CGC also contains osmoprotectants. The CMC drop is a standard aqueous polymeric supplement. RESULTS: Significant improvements were seen in symptoms (OSDI) and tear stability (NITBUT) with all 3 treatments at 4 weeks. At 4 weeks post-CGC, 6 out of 7 biomarkers demonstrated a >25% reduction (in 40% of subjects). The same reduction (>25%) was seen in 10% of the subjects for CMC and in none of the subjects for HPG. No significantly different change to either evaporation rate or tear osmolarity was found following any of the three treatments. CONCLUSIONS: In this study, the CGC treatment resulted in the greatest reduction in ocular biomarkers of inflammation, while all 3 treatments reduced symptoms and improved tear stability. These results indicate that subject-perceived symptomatic improvements are not necessarily associated with a reduction in objective measures of inflammation.

Basal Tear Osmolarity as a metric to estimate body hydration and dry eye severity.

The osmolarities of various bodily fluids, including tears, saliva and urine, have been used as indices of plasma osmolality, a measure of body hydration, while tear osmolarity is used routinely in dry eye diagnosis, the degree of tear hyperosmolarity providing an index of disease severity. Systemic dehydration, due to inadequate water intake or excessive water loss is common in the elderly population, has a high morbidity and may cause loss of life. Its diagnosis is often overlooked and there is a need to develop a simple, bedside test to detect dehydration in this population. We hypothesize that, in the absence of tear evaporation and with continued secretion, mixing and drainage of tears, tear osmolarity falls to a basal level that is closer to that of the plasma than that of a tear sample taken in open eye conditions. We term this value the Basal Tear Osmolarity (BTO) and propose that it may be measured in tear samples immediately after a period of evaporative suppression. This value will be particular to an individual and since plasma osmolarity is controlled within narrow limits, it is predicted that it will be stable and have a small variance. It is proposed that the BTO, measured immediately after a defined period of eye closure, can provide a new metric in the diagnosis of systemic dehydration and a yardstick against which to gauge the severity of dry eye disease.

Care solution effects on contact lens in vivo wettability.

BACKGROUND: The aim of the study was to evaluate the effect of care solutions on contact lens in vivo wettability using Doane's interferometric technique. METHODS: Thirteen subjects (aged 26.6 ± 6.3 years) participated for contact lens wettability evaluation after soaking in five care solutions namely Opti-Free EverMoist (now called puremoist), Opti-Free Express (Alcon), COMPLETE (AMO), ReNu and Biotrue (Bausch & Lomb). A new pair of lenses was soaked in the solutions for eight hours (prior to wear) or taken directly from pack solutions (as control) and worn by the subjects. The total number of pairs of lenses tested was 13 by six (78 lenses; 13 pairs of lenses wetted in five care solutions plus the pack solution). Doane's interferometer was used to capture images of the pre-lens film on a single type of contact lens, Acuvue Oasys (Johnson & Johnson). The lens in vivo wettability was evaluated after 15 minutes and eight hours of wear by each subject. Four parameters: onset latency, drying duration, maximum speed and peak latency were used to assess the lens wettability. RESULTS: After eight hours, the solutions showing significant reduction in contact lens wettability were the following. For onset latency: Pack solution, Biotrue Opti-Free EverMoist and Express; for drying duration: pack solution, ReNu and Opti-Free EverMoist; for peak latency; pack solution, Biotrue and Opti-Free EverMoist. Regarding the maximum speed, lenses soaked in Pack solution, ReNu and Opti-Free EverMoist showed a significant increase (worsening). The comparative study showed that there were significant differences among the performance of the care solutions. CONCLUSION: This novel thin film interferometric technique was able to measure, objectively, contact lens in vivo wettability, following the use of care solutions. COMPLETE was the only solution that showed no significant change in the lens wettability (with the all parameters) between the initial and the end of day.

Effects of Humidity on Tests of Tear Production.

PURPOSE: To determine if the Schirmer test is affected by environmental humidity, to quantify any effects, and to consider the ways in which this may affect the diagnosis of dry eye disease. METHODS: All experiments took place within a controlled environment chamber at a range of 5% to 95% relative humidity (RH). In vitro testing immersed Schirmer strips at 5 mm depth in water for 5 minutes. In vivo tests were conducted using the standard clinical method. All experiments were conducted using both standard Schirmer strips and Schirmer strips sheathed in a plastic film in order to reduce the possible effects of evaporation. RESULTS: In vitro results showed a clear decrease in Schirmer wetting length as RH was reduced. Schirmer test strips that were encased within a plastic sheathing were less affected by changing RH. As well as wetting length, the rate of wetting of Schirmer strips was also affected by changes in RH. In vivo data showed that Schirmer results in participants with severe dry eye disease were less affected by changes in RH than "normal" participants. CONCLUSIONS: Patients with severe dry eye disease produce Schirmer test results which are unaffected by environmental humidity. However, patients with moderate Schirmer wetting lengths may be falsely diagnosed as having dry eye disease if their test is undertaken in a low-humidity environment. This phenomenon may be overcome with the use of plastic sheathing. Previous studies investigating the effects of environmental conditions on the tear film may have been affected by this phenomenon.

Effect of Ambient Temperature on the Human Tear Film.

PURPOSE: 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. METHOD: 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. RESULT: 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. CONCLUSION: 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.

The effect of low humidity on the human tear film.

PURPOSE: To investigate the effect of exposure to a low relative humidity (RH) environment on tear film physiology. METHOD: A controlled environment chamber was used to create 2 different environmental conditions. Ambient temperature was constant in both conditions (21°C) while the RH was set at 40% at the normal condition and at 5% in the desiccating environment. Tear evaporation, noninvasive tear break-up time, lipid layer thickness (LLT), osmolarity, ocular comfort, tear production, and ocular surface temperature were assessed in normal humidity and over a period of 60 minutes in the dry environment. RESULTS: There was significant change in tear evaporation rate (P = 0.00), noninvasive tear break-up time (P = 0.00), LLT (P = 0.00), ocular comfort (P = 0.00), and tear production (P = 0.01) after exposure to the desiccating environment. No significant differences were observed between normal and dry environmental conditions in tear osmolarity (P = 0.09) and ocular surface temperature (P = 0.20). CONCLUSIONS: Evaporation rate, tear LLT, ocular comfort, tear stability, and production were adversely affected by low RH. The tear film parameters observed after exposure to a desiccating environment for 1 hour were similar to those of the dry eye patient. Therefore, to avoid tear film disruption and possible ocular surface damage, the environmental conditions of dry locations need to be improved or the tear film should be protected against adverse environmental conditions.

Low energy lamps and eye lens autofluorescence.

Tungsten filament lamps are rapidly being displaced from the market-place by compact fluorescent lamps. Although the colour temperature and total luminous output of a fluorescent lamp may be similar to that of an incandescent lamp, the output spectrum is very different. The peaks of the mercury vapour spectrum at 365.4nm (UV) and at 435.8nm (blue) are close to the peak fluorescence excitation wavelengths in the human lens, and it has been shown that such fluorescence can lower sensitivity to low contrast objects. This effect could also explain the reported preference for brown, red and yellow tinted lenses often reported by elderly patients, as these coincidentally block the ultraviolet and blue exciting wavelengths.

The influence of automobile windscreen rake on effective light transmittance.

The theoretical transmittances at the installation angle of the windscreens of the ten best-selling cars in the UK in 2008 are investigated. The data show that the ten most popular cars on the UK roads have a windscreen rake that reduces transmittance to a value close to or below that specified in International Standards for normal incidence. British and International Standards for windscreen transmittance should be revisited by the relevant authorities in the light of the high rake angles that have become widespread in recent years. The problem is worsened considerably by tinted windscreens having become the default option in many models. It is also suggested that there may be good reason for all spectacles supplied to drivers for low light level driving to be untinted and anti-reflection coated.

Does the niqab (veil) wearer satisfy the minimal visual field for driving?

Visual field testing of subjects wearing a niqab was carried out using the approved (Esterman) test on a Humphrey perimeter to determine if visually normal subjects met the European driving standard. Measurement of aperture dimensions of the niqab when worn was recorded. When wearing the niqab, all subjects achieved a visual field adequate to satisfy UK/European driving standards. A measurement of the limiting aperture size was obtained and a self-test method for niqab wearers was determined.

A simple variable prism with a linear scale.

PURPOSE: To build a simple, low cost, variable-power prism with a linear scale. METHODS: A sliding lens system, using the prismatic effect of ophthalmic lenses, was constructed. RESULTS: The system functions well at low powers using conventional curved form ophthalmic lenses. CONCLUSIONS: The sliding lens variable prism is a useful alternative to the conventional rotating variable-power prism.

Is the spectacle lens jack-in-the-box phenomenon really due to the lenses?

The calculation of the extent of the ring scotoma around positive lenses, as conventionally taught to students of clinical optics, indicates that the scotoma is of a significant size. Using knife-edge lenses this study shows that the calculations are invalid due to the finite size of the eye's entrance pupil and in many instances the scotoma is shown not to exist. The effect noticed in clinical practice is probably largely due to the frame and the edging techniques used which add to the refractive scotoma which is present with high powered lenses, large apertures and/or small pupil sizes.