Optimizing the methodology for the assessment of bulbar conjunctival lissamine green staining

SIGNIFICANCE When using lissamine green for bulbar conjunctival evaluation, the most staining was observed with two applications of the same strip in the same eye, wetted with a drop of saline. The first application was 5 seconds after wetting the strip, and the second was 1 minute later, followed by immediate viewing. This suggests that bulbar staining should be viewed before the lid wiper region.PURPOSE This study aimed to optimize the assessment of lissamine green staining of the bulbar conjunctiva by investigating the application technique and subsequent observation period.METHODS Twenty-two participants with dry eye (as defined by the Tear Film and Ocular Surface Society Dry Eye Workshop II) were recruited to trial five application methods in randomized order: (1) application immediately after wetting a single strip, (2) application 5 seconds after wetting a single strip, (3) application 10 seconds after wetting a single strip, (4) consecutive single application of sodium fluorescein followed by lissamine green 5 seconds after wetting, and (5) two applications using the same lissamine green strip 5 seconds after wetting, 1 minute apart. Slit-lamp photography of the conjunctiva was performed immediately following application and at 30, 60, 90, and 300 seconds after application. Three experienced (masked) practitioners independently quantified the visible punctate spots and graded the staining intensity within the images in a random order.RESULTS Values for punctate spot count (F = 6.29, p<0.0001) and lissamine green staining intensity (F = 6.29, p<0.0001) varied significantly between the different application methods. Using two applications of the same lissamine green strip, 1 minute apart, in the same eye resulted in the greatest values for both punctate spot count and lissamine green staining intensity. Lissamine green staining decreased with time for both spot count (F = 18.87, p<0.0001) and lissamine green staining intensity (F = 11.33, p<0.0001), with the most staining found immediately after application followed by a gradual decline. There was no evidence of any interaction effect between time and application method for either measure (p>0.05 for both).CONCLUSIONS The optimal approach for assessing bulbar conjunctival lissamine green staining involves two applications of a whole infused drop resting on the same strip for 5 seconds, applied 1 minute apart. The ocular surface should be viewed immediately after application to maximize the conjunctival staining observed

The impact of material surface characteristics on the clinical wetting properties of silicone hydrogel contact lenses

This PhD project investigated the ramifications of air-cured and nitrogen-cured manufacturing processes during silicone hydrogel contact lens manufacture in terms of lens surface characterisation and clinical performance. A one-hour contralateral clinical study was conducted for ten subjects to compare the clinical performance of the two study lenses. The main clinical findings were reduced levels of subjective performance, reduced surface wettability and increased deposition. Contact angle analysis showed the air-cured lenses had consistently higher advancing and receding contact angle measurements, in comparison with the nitrogen-cured lens. Chemical analysis of the study lens surfaces in the dehydrated state, by x-ray photoelectron spectroscopy (XPS) and time-of-flight mass spectrometry (ToF-SIMS), showed no difference due to surface segregation of the silicone components. Analysis of frozen lenses limited surface segregation and showed a higher concentration of silicone polymer components and lower concentration of hydrophilic polymer components at the surface of the air-cured lens, in comparison with the nitrogen-cured lens. Scanning electron microscope (SEM) imaging showed the nitrogen-cured lens to have a surface typical of a hydrogel material, whereas the air-cured lens had regions of apparent phase separation. In addition, atomic force microscopy (AFM) showed the air-cured lens to have a rougher surface associated with greater adherence of contaminants (often observed in materials with reduced polymer cross-linking). In conclusion, clinical assessment of the study lenses confirmed the inferior performance of the air-cured lens. Surface analysis suggested that the non-wetting regions on the air-cured lenses were associated with elevated level of silicone components, reduced polymer cross-linking and polymer phase separation.EThOS - Electronic Theses Online ServiceCooperVision Inc.Medical Research CouncilGBUnited Kingdo

The impact of material surface characteristics on the clinical wetting properties of silicone hydrogel contact lenses

This PhD project investigated the ramifications of air-cured and nitrogen-cured manufacturing processes during silicone hydrogel contact lens manufacture in terms of lens surface characterisation and clinical performance. A one-hour contralateral clinical study was conducted for ten subjects to compare the clinical performance of the two study lenses. The main clinical findings were reduced levels of subjective performance, reduced surface wettability and increased deposition. Contact angle analysis showed the air-cured lenses had consistently higher advancing and receding contact angle measurements, in comparison with the nitrogen-cured lens. Chemical analysis of the study lens surfaces in the dehydrated state, by x-ray photoelectron spectroscopy (XPS) and time-of-flight mass spectrometry (ToF-SIMS), showed no difference due to surface segregation of the silicone components. Analysis of frozen lenses limited surface segregation and showed a higher concentration of silicone polymer components and lower concentration of hydrophilic polymer components at the surface of the air-cured lens, in comparison with the nitrogen-cured lens. Scanning electron microscope (SEM) imaging showed the nitrogen-cured lens to have a surface typical of a hydrogel material, whereas the air-cured lens had regions of apparent phase separation. In addition, atomic force microscopy (AFM) showed the air-cured lens to have a rougher surface associated with greater adherence of contaminants (often observed in materials with reduced polymer cross-linking). In conclusion, clinical assessment of the study lenses confirmed the inferior performance of the air-cured lens. Surface analysis suggested that the non-wetting regions on the air-cured lenses were associated with elevated level of silicone components, reduced polymer cross-linking and polymer phase separation.EThOS - Electronic Theses Online ServiceCooperVision Inc.Medical Research CouncilGBUnited Kingdo

Temporal variations in meibomian gland structure—A pilot study

Purpose: To investigate whether there is a measurable change in meibomian gland morphological characteristics over the course of a day (12h) and over a month.Methods: The study enrolled 15 participants who attended a total of 11 study visits spanning a 5-week period. To assess diurnal changes in meibomian glands, seven visits were conducted on a single day, each 2h apart. For monthly assessment, participants attended an additional visit at the same time of the day every week for three consecutive weeks. Meibography using the LipiView® II system was performed at each visit, and meibomian gland morphological parameters were calculated using custom semi-automated software. Specifically, six central glands were analysed for gland length ratio, gland width, gland area, gland intensity and gland tortuosity.Results: The average meibomian gland morphological metrics did not exhibit significant changes during the course of a day or over a month. Nonetheless, certain individual gland metrics demonstrated notable variation over time, both diurnally and monthly. Specifically, meibomian gland length ratio, area, width and tortuosity exhibited significant changes both diurnally and monthly when assessed on a gland-by-gland basis.Conclusions: Meibomian glands demonstrated measurable structural change over short periods of time (hours and days). These results have implications for innovation in gland imaging and for developing precision monitoring of gland structure to assess meibomian gland  health more accurately

Clinical performance and Willingness To Pay for soft toric contact lenses in low and moderate astigmats

Purpose: To determine clinical performance and the ‘Willingness To Pay’ for toric vs. spherical soft contact lenses in an astigmatic population. Methods: In the clinical study, subjects with binocular low to moderate astigmatism (-0.75DC to − 1.50DC) wore pairs of soft toric (Biofinity toric) and spherical (Biofinity) contact lenses in random sequence. Visual acuity (high and low contrast, monocular and binocular), subjective comfort and subjective vision were recorded. In the economics study, first subjects who had participated in the clinical study were presented with a series of randomised economic scenarios in order to determine their Willingness To Pay a premium (i.e. an increase) for toric lenses. Then, a similar set of scenarios were presented to a much larger group of online respondents and again, Willingness To Pay was established. Results: For the four measures of visual acuity, the Biofinity toric lens out-performed the Biofinity spherical lens by 0.6 to 1.1 lines.. Subjective vision performance was statistically significantly better with the toric lens for the distance task only. Comfort scores were not significantly different. Similar findings for Willingness To Pay were established for the clinical subjects and for the online respondents. The Willingness To Pay premium (additional fee) for a monthly supply of toric lenses (over spherical lenses) was between £13 and £16, if a toric lens provides better vision and similar comfort, as shown in the clinical study. Conclusion: Consumers are willing to pay a monthly premium of around 50% to benefit from the typical experience of better vision and similar comfort for toric vs. spherical lenses. The level of additional cost for toric lenses compared to their spherical equivalents is less than this in the market, so eye care professionals should consider that toric lenses are delivering a greater clinical return than anticipated by wearers for the relatively small increase in price

The TFOS international workshop on contact lens discomfort: report of the contact lens materials, design, and care subcommittee

Jones, L., Brennan, N. A., González-Méijome, J., Lally, J., Maldonado-Codina, C., Schmidt, T. A., … Nichols, J. J. (2013). The TFOS International Workshop on Contact Lens Discomfort: Report of the Contact Lens Materials, Design, and Care Subcommittee. Investigative Opthalmology & Visual Science, 54(11), TFOS37. https://doi.org/10.1167/iovs.13-13215Examining the role of the contact lens material, design, and the care system is fundamental to understanding contact lens discomfort (CLD). However, a systematic review that tries to determine the governing factors is fraught with difficulties. A lack of a validated “instrument” (or single validated questionnaire) for measuring discomfort makes it impossible to compare between studies because reported levels of comfort (or discomfort) are inconsistent. Subject classifications can vary widely, from studies that include only neophytes or asymptomatic contact lens (CL) wearers to studies including only those contact lens–wearing subjects who experience marked dryness or symptoms of discomfort. Also, it is difficult to measure issues of importance in isolation because changing one factor in a contact lens or care solution can invariably affect another. An illustration of this relates to a change in hydrogel water content, which also affects oxygen permeability, oxygen transmissibility, modulus, and possibly lens thickness. Finally, various confounding factors between studies also make true comparisons problematic. Typical examples would include differences between brands of lenses made from the same material (which may have differing geometric designs, edge configuration, or production methods); wearing modality (lenses may be worn on a daily wear [DW] basis, overnight occasionally, or for up to 30 nights on a continuous wear [CW] basis); duration of use prior to replacement, wearing time during the day (from just a few hours to most of the day); and care product differences or exposures (which could range from no exposure in the case of daily disposable [DD] materials to a preserved system that has extensive uptake and release from the contact lens material being examined). The purpose of this report is to summarize evidence-linking associations, mechanistic and etiological factors between contact lens materials, designs, and care solutions with CLD. The potential factors associated with this are many and varied, and graphically display the complexity of this issue