Clinical monitoring of ocular physiology using digital image analysis

Optimising subjective grading of corneal staining in Sjögren's syndrome dry eye disease

AIM

To assess whether smaller increment and regionalised subjective grading improves the repeatability of corneal fluorescein staining assessment, and to determine the neurological approach adopted for subjective grading by practitioners.

METHODS

Experienced eye-care practitioners (n = 28, aged 45 ± 12 years), graded 20 full corneal staining images of patients with mild to severe Sjögren's syndrome with the Oxford grading scheme (both in 0.5 and 1.0 increments, globally and in 5 regions), expanded National Eye Institute (NEI) and SICCA Ocular Staining Score (OSS) grading scales in randomised order. This was repeated after 7-10 days. The digital images were also analysed objectively to determine staining dots, area, intensity and location (using ImageJ) for comparison.

RESULTS

The Oxford grading scheme was similar with whole and half unit grading (2.77vs2.81,p = 0.145), but the variability was reduced (0.14vs0.12,p < 0.001). Regional grade was lower (p < 0.001) and more variable (p < 0.001) than global image grading (1.86 ± 0.44 for whole increment grading and 1.90 ± 0.39 for half unit increments). The correlation with global grading was high for both whole (r = 0.928,p < 0.001) and half increment (r = 0.934,p < 0.001) grading. Average grading across participants was associated with particle number and vertical position, with 74.4-80.4% of the linear variance accounted for by the digital image analysis.

CONCLUSIONS

Using half unit increments with the Oxford grading scheme improve its sensitivity and repeatability in recording corneal staining. Regional grading doesn't give a comparable score and increased variability. The key neurally extracted features in assigning a subjective staining grade by clinicians were identified as the number of discrete staining locations (particles) and how close to the vertical centre was their spread, across all three scales.

2022 Glenn A. Fry Award lecture: Enhancing clinical assessment for improved ophthalmic management

ABSTRACT

Detailed clinical assessment is critical to allow sensitive evaluation of the eye and its management. As technology advances, these assessment techniques can be adapted and refined to improve the detection of pathological changes of ocular tissue and their impact on visual function. Enhancements in optical medical devices including spectacle, contact, and intraocular lenses have allowed for a better understanding of the mechanism and amelioration of presbyopia and myopia control. Advancements in imaging technology have enabled improved quantification of the tear film and ocular surface, informing diagnosis and treatment strategies. Miniaturized electronics, large processing power, and in-built sensors in smartphones and tablets capacitate more portable assessment tools for clinicians, facilitate self-monitoring and treatment compliance, and aid communication with patients. This article gives an overview of how technology has been used in many areas of eye care to improve assessments and treatment and provides a snapshot of some of my studies validating and using technology to inform better evidence-based patient management.

Multi-scale information fusion network with label smoothing strategy for corneal ulcer classification in slit lamp images

Corneal ulcer is the most common symptom of corneal disease, which is one of the main causes of corneal blindness. The accurate classification of corneal ulcer has important clinical importance for the diagnosis and treatment of the disease. To achieve this, we propose a deep learning method based on multi-scale information fusion and label smoothing strategy. Firstly, the proposed method utilizes the densely connected network (DenseNet121) as backbone for feature extraction. Secondly, to fully integrate the shallow local information and the deep global information and improve the classification accuracy, we develop a multi-scale information fusion network (MIF-Net), which uses multi-scale information for joint learning. Finally, to reduce the influence of the inter-class similarity and intra-class diversity on the feature representation, the learning strategy of label smoothing is introduced. Compared with other state-of-the-art classification networks, the proposed MIF-Net with label smoothing achieves high classification performance, which reaches 87.07 and 83.84% for weighted-average recall (W_R) on the general ulcer pattern and specific ulcer pattern, respectively. The proposed method holds promise for corneal ulcer classification in fluorescein staining slit lamp images, which can assist ophthalmologists in the objective and accurate diagnosis of corneal ulcer.

Studying the Effects of Cold Plasma Phosphorus Using Physiological and Digital Image Processing Techniques

The goal of this study is to see how cold plasma affects rabbit bone tissue infected with osteoporosis. The search is divided into three categories: control, infected, and treated. The rabbits were subjected to cold plasma for five minutes in a room with a microwave plasma voltage of “175 V” and a gas flow of “2.” A histopathological photograph of infected bone cells is obtained to demonstrate the influence of plasma on infected bone cells, as well as the extent of destruction and effect of plasma therapy before and after exposure. The findings of the search show that plasma has a clear impact on Ca and vitamin D levels. In the cold plasma, the levels of osteocalcin and alkali phosphates (ALP) respond as well. Image processing techniques (second-order gray level matrix) with textural elements are employed as an extra proof. The outcome gives good treatment indicators, and the image processing result corresponds to the biological result.

Semi-MsST-GAN: A Semi-Supervised Segmentation Method for Corneal Ulcer Segmentation in Slit-Lamp Images

Corneal ulcer is a common leading cause of corneal blindness. It is difficult to accurately segment corneal ulcers due to the following problems: large differences in the pathological shapes between point-flaky and flaky corneal ulcers, blurred boundary, noise interference, and the lack of sufficient slit-lamp images with ground truth. To address these problems, in this paper, we proposed a novel semi-supervised multi-scale self-transformer generative adversarial network (Semi-MsST-GAN) that can leverage unlabeled images to improve the performance of corneal ulcer segmentation in fluorescein staining of slit-lamp images. Firstly, to improve the performance of segmenting the corneal ulcer regions with complex pathological features, we proposed a novel multi-scale self-transformer network (MsSTNet) as the MsST-GAN generator, which can guide the model to aggregate the low-level weak semantic features with the high-level strong semantic information and adaptively learn the spatial correlation in feature maps. Then, to further improve the segmentation performance by leveraging unlabeled data, the semi-supervised approach based on the proposed MsST-GAN was explored to solve the problem of the lack of slit-lamp images with corresponding ground truth. The proposed Semi-MsST-GAN was comprehensively evaluated on the public SUSTech-SYSU dataset, which contains 354 labeled and 358 unlabeled fluorescein staining slit-lamp images. The results showed that, compared with other state-of-the-art methods, our proposed method achieves better performance with comparable efficiency.

Canonical Grading Scales of Corneal and Conjunctival Staining Based on Psychophysical and Physical Attributes

Purpose

In this study, we apply psychophysical scaling principles based on physical (photometric) attributes of images to better understand the factors involved in clinician judgement of ocular surface staining and, using that knowledge, to develop photographic scales for the assessment of staining for dry eye (DE) and related conditions.

Methods

Subjects with noninfectious ocular surface staining were enrolled at five clinical sites. Following instillation of fluorescein, photographs of corneal staining were taken every 30 seconds for at least 5 minutes. The same procedure was followed for conjunctival staining after instillation of 2 µl of 1% lissamine green. A subset of the best corneal and bulbar conjunctival staining images were anonymized and a spectroradiometer measured photometric attributes (luminance and chromaticity). The images were scaled psychophysically by study investigators, who participated in constructing grading scales based on physical and psychophysical analyses. The final grading scales were refined following consultation with outside DE experts.

Results

Photographs were collected from 142 subjects (81% women), with an average age of 58 ± 17 years; 89% were diagnosed with DE. There was a monotonic relationship between between physical measurements and psychophysically scaled staining of both corneal (fluorescein) and bulbar (lissamine green) staining. Michelson contrast and u’ (chromaticity) accounted for 66% and 64% of the variability in the psychophysically scaled images of fluorescein corneal and lissamine green conjunctival staining, respectively.

Translational Relevance

This paper provides examples of the first ever clinically usable ocular surface staining scales validated using psychophysical scaling and the physical attributes (luminance and chromaticity) of the staining itself. In addition, it provides a generalizable method for the development of other clinical scales of ocular appearance.

Ocular redness - I: Etiology, pathogenesis, and assessment of conjunctival hyperemia

The translucent appearance of the conjunctiva allows for immediate visualization of changes in the circulation of the conjunctival microvasculature consisting of extensive branching of superficial and deep arterial systems and corresponding drainage pathways, and the translucent appearance of the conjunctiva allows for immediate visualization of changes in the circulation. Conjunctival hyperemia is caused by a pathological vasodilatory response of the microvasculature in response to inflammation due to a myriad of infectious and non-infectious etiologies. It is one of the most common contributors of ocular complaints that prompts visits to medical centers. Our understanding of these neurogenic and immune-mediated pathways has progressed over time and has played a critical role in developing targeted novel therapies. Due to a multitude of underlying etiologies, patients must be accurately diagnosed for efficacious management of conjunctival hyperemia. The diagnostic techniques used for the grading of conjunctival hyperemia have also evolved from descriptive and subjective grading scales to more reliable computer-based objective grading scales.

Anterior ophthalmic imaging

Improvements in imaging chips and computer processing power have brought major advances in imaging of the anterior eye. Digitally captured images can be visualised immediately and can be stored and retrieved easily. Anterior ocular imaging techniques using slitlamp biomicroscopy, corneal topography, confocal microscopy, optical coherence tomography (OCT), ultrasonic biomicroscopy, computerised tomography (CT) and magnetic resonance imaging (MRI) are reviewed. Conventional photographic imaging can be used to quantify corneal topography, corneal thickness and transparency, anterior chamber depth and lateral angle and crystalline lens position, curvature, thickness and transparency. Additionally, the effects of tumours, foreign bodies and trauma can be localised, the corneal layers can be examined and the tear film thickness assessed.

The SUSTech-SYSU dataset for automatically segmenting and classifying corneal ulcers

Corneal ulcer is a common ophthalmic symptom. Segmentation algorithms are needed to identify and quantify corneal ulcers from ocular staining images. Developments of such algorithms have been obstructed by a lack of high quality datasets (the ocular staining images and the corresponding gold-standard ulcer segmentation labels), especially for supervised learning based segmentation algorithms. In such context, we prepare a dataset containing 712 ocular staining images and the associated segmentation labels of flaky corneal ulcers. In addition to segmentation labels for flaky corneal ulcers, we also provide each image with three-fold class labels: firstly, each image has a label in terms of its general ulcer pattern; secondly, each image has a label in terms of its specific ulcer pattern; thirdly, each image has a label indicating its ulcer severity degree. This dataset not only provides an excellent opportunity for investigating the accuracy and reliability of different segmentation and classification algorithms for corneal ulcers, but also advances the development of new supervised learning based algorithms especially those in the deep learning framework.

Validation of Computerized Quantification of Ocular Redness

Purpose

To show feasibility of computerized techniques for ocular redness quantification in clinical studies, and to propose an automatic, objective method.

Methods

Software for quantification of redness of the bulbar conjunctiva was developed. It provides an interface for manual and automatic sclera segmentation along with automated alignment of region of interest to enable estimation of changes in redness. The software also includes the redness scoring methods: (1) contrast-limited adaptive histogram equalization (CLAHE) in red-green-blue (RGB) color model, (2) product of saturation and hue in hue-saturation-value (HSV), and (3) average of angular sections in HSV. Our validation pipeline compares the scoring outcomes from the perspectives of segmentation reliability, segmentation precision, segmentation automation, and the choice of redness scoring methods.

Results

Ninety-two photographs of eyes before and after provoked redness were evaluated. Redness in manually segmented images was significantly different within human observers (interobserver, P = 0.04) and two scoring sessions (intraobserver, P < 0.001). Automated segmentation showed the smallest variability, and can therefore be seen as a robust segmentation method. The RGB-based scoring method was less sensitive in redness assessment.

Conclusions

Computation of ocular redness depends heavily on sclera segmentation. Manual segmentation appears to be subjective, resulting in systematic errors in intraobserver and interobserver settings. At the same time, automatic segmentation seems to be consistent. The scoring methods relying on HSV color space appeared to be more consistent.

Translational Relevance

Computerized quantification of ocular redness holds great promise to objectify ocular redness in the standard clinical care and, in particular, in clinical trials.

Assessment of Corneal Fluorescein Staining in Different Dry Eye Subtypes Using Digital Image Analysis

Purpose

To describe a new objective technique of digital image analysis for the quantification and the morphological characterization of corneal staining in the setting of dry eye disease (DED), and to apply it to distinguish Sjögren syndrome (SS) from ocular graft versus-host disease (oGVHD).

Methods

Slit-lamp photographs of corneal staining obtained from 40 patients with DED (20 with SS and 20 with oGVHD; mean age 60.7 ± 12.3 years) were evaluated. Images were subjectively graded using Oxford and National Eye Institute (NEI) scales, the staining pattern was classified as micropunctate, macropunctate, coalescent, or patch. The corneal staining index (CSI) was calculated automatically using the software ImageJ 1.51s. Particles analysis was used to calculate mean area, circularity, and roundness of staining spots.

Results

CSI was significantly correlated with Oxford and NEI scales (respectively Rs = 0.823 and Rs = 0.773; both P < 0.001), and showed a good interobserver reliability (intraclass correlation coefficient [ICC] = 0.988 [95% confidence interval [CI]: 0.978–0.994]). The mean area of staining spots calculated with particles analysis was significantly correlated with the subjective classification of the staining pattern (Rs = 0.550, P < 0.001). The circularity and roundness of staining spots were significantly higher in oGVHD patients compared with SS (respectively, 0.51 ± 0.11 vs. 0.44 ± 0.10, P = 0.040; 0.61 ± 0.03 vs. 0.59 ± 0.02, P = 0.004). Sensitivity and specificity to distinguish oGVHD from SS were respectively 65.0% and 60% for circularity and 80.0% and 70.0% for roundness.

Conclusions

The new algorithm showed good reliability and was well correlated with the traditional subjective grading scales. Particles analysis for the objective assessment of the staining pattern may help to differentiate patients with oGVHD from those with SS.

Translational Relevance

The digital image analysis technique may be a reliable alternative to evaluate corneal staining objectively in the clinic and in clinical trials.

Multimodal Assessment of Corneal Erosions Using Optical Coherence Tomography and Automated Grading of Fluorescein Staining in a Rabbit Dry Eye Model

Purpose

To evaluate the potential use of anterior segment spectral domain optical coherence tomography (AS-SD-OCT) combined with an automated grading of fluorescein staining for assessment of corneal erosions in a rabbit short-term dry eye model.

Methods

Twenty-one New Zealand white rabbits were anesthetized and eyes were kept open for 140 minutes to induce acute corneal desiccation. Rectangular scans of the cornea were performed using Spectralis AS-SD-OCT. Total corneal thickness, corneal epithelial thickness, and the percentage of epithelial erosion area (PEEA) were evaluated. Corneas were stained with fluorescein and graded automatically using EpiView and semi-automatically using ImageJ. Spearman's rank-order correlations were calculated to compare the AS-SD-OCT PEEA and the two corneal staining scores.

Results

Eye desiccation resulted in corneal epithelium erosions that covered 0.67% to 14.2% of the central cornea (mean ± SD: 3.95% ± 3.2%) by AS-SD-OCT. The percentage of corneal area positively stained with fluorescein ranged from 0.24% to 38.01% (mean ± SD: 12.24% ± 9.7%) by using ImageJ, correlating with the AS-SD-OCT PEEA (Spearman's ρ, 0.574; P = 0.007). The EpiView score ranged from 0.5 to 10.17 and was better correlated with the AS-SD-OCT PEEA score (Spearman's ρ, 0.795; P = 0.000017).

Conclusions

Our study suggests that multimodal analysis of AS-SD-OCT and grading of fluorescein staining using EpiView software may enable quantitative assessment of corneal epithelial erosions in a rabbit short-term dry eye model.

Translational Relevance

This multimodal imaging analysis may be applied for evaluation of superficial punctate keratitis associated with dry eye.

Comparison of different smartphone cameras to evaluate conjunctival hyperaemia in normal subjects

Despite the significant advantages that smartphones’ cameras can provide in teleophthalmology and artificial intelligence applications, their use as black-box systems for clinical data acquisition, without adequate information of the quality of photographs can compromise data accuracy. The aim of this study is to compare the objective and subjective quantification of conjunctival redness in images obtained with calibrated and non-calibrated cameras, in different lighting conditions and optical magnifications. One hundred ninety-two pictures of the eye were taken in 4 subjects using 3 smartphone cameras{Bq, Iphone, Nexus}, 2 lighting levels{high 815 lx, low 122 lx} and 2 magnification levels{high 10x, low 6x}. Images were duplicated: one set was white balanced and color corrected (calibrated) and the other was left as it was. Each image was subjective and objectively evaluated. There were no significant differences in subjective evaluation in any of the conditions whereas many statistically significant main effects and interaction effects were shown for all the objective metrics. The clinician’s evaluation was not affected by different cameras, lighting conditions or optical magnifications, demonstrating the effectiveness of the human eye’s color constancy properties. However, calibration of a smartphone’s camera is essential when extracting objective data from images.

Review and analysis of grading scales for ocular surface staining

Vital dye staining has been used for over a century to assess the severity of ocular surface disease. However, despite common usage, a universally accepted "gold standard" grading scale does not exist for corneal and conjunctival staining, which can impact the ability to diagnose and monitor ocular surface conditions such as dry eye. The Food and Drug Administration (FDA) and other international regulatory agencies rely on ocular surface staining as a primary endpoint for new drug approvals, so that absence of a "gold standard" scale may affect approval of new drug treatments. To begin to address this problem, we review existing, published grading scales in an integrated fashion, highlighting their differences and similarities to emphasize common themes and the methods and elements that are important in creating a standardized scale. Our goal is to aid the field in moving towards an accepted standardized grading scale for ocular surface staining that can be applied in clinic and research settings for a variety of ocular conditions.

Assessment of ocular redness measurements obtained with keratograph 5M and correlation with subjective grading scales

OBJECTIVE

To examine correlations between ocular redness scores provided by the Keratograph 5M and those determined using two image-based grading scales.

METHODS

Observational prospective cross-sectional study. Two hundred and twenty six eyes of two hundred and twenty six participants (175 patients using anti-glaucoma eye drops and 51 subjects untreated). All subjects were scored automatically using the keratograph 5M. These redness scores (RS) were then correlated with the gradings provided by the Efron and McMonnies/Chapman-Davies scale (MC-D) scales (two observers).

RESULTS

Excellent reproducibility was observed for both the Efron (weighted K=0.897, 95% CI 0.823-0.904) and MC-D (weighted K=0.783, 95% CI 0.752-0.795) scales. Keratograph RS and the scores obtained with both Efron (Spearman's Rho=0.43, P<0.001) and MC-D (Spearman's Rho=0.48, P<0.001) scales were significantly correlated. RS for the bulbar and limbal - nasal and temporal quadrants also correlated moderately with the two subjective scales. Through Bland Altman analysis, poor agreement was detected between the objective and subjective methods: agreement values for the Efron scale or MC-D scale (matching scorers between observers) versus overall RS showed high biases (-15.58 and -22.05 respectively) and wide limits of agreement (LOA) (-46.169 to 15.005 and -52.534 to 8.19 respectively). Lowest bias was observed between temporal limbal RS and Observer 2 Efron score (-0.04).

CONCLUSIONS

Although it emerged as a reliable objective method, the keratograph 5M overestimated the scores compared with the subjective grading scales when used to grade the degree of ocular redness. Therefore, they should not be interchangeable methods.

Comparison of subjective grading of lid wiper epitheliopathy with a semi-objective method

PURPOSE

To validate a semi-objective method of grading lid wiper epitheliopathy (LWE) compared to subjective assessment.

METHODS

Twenty upper and 20 lower eyelid margins of patients with LWE were photographed after instillation of fluorescein and lissamine green. The images were graded by two observers using a 0-3 grading scale for height (%) and width (mm) of the lid staining. The images were also processed using custom designed software in MATLAB. After manual delineation of the staining area, width and perpendicular height were automatically measured throughout the selected area. The height as a proportion of the lid margin width and width measures were then categorized into the same bins as in the grading scale.

RESULTS

Repeatability of the image analysis system showed a mean difference (95% limits of agreement) between repeats of -0.01mm (0.03 and -0.05mm) for LWE height, 0.04mm (1.16 and -1.08mm) for LWE width, and -0.11mm² (0.32 and -0.53mm²) for LWE area. The mean difference (95% limits of agreement) between image analysis and human grading for LWE height was -0.84 grades (0.54 and -2.21 grades), for LWE width was 0.31 grades (1.22 and -0.59 grades), and for the final grade (mean height and width) was -0.26 (0.44 and -0.96 grades) (all p<0.001).

CONCLUSION

Human observers tend to overestimate the height and underestimate the width of LWE staining. Lid wiper region is not well defined, thus, it might be a difficult process for human observers to judge the stained region as a proportion of the lid wiper total region.

iDEAS: A web-based system for dry eye assessment

BACKGROUND AND OBJECTIVES

Dry eye disease is a public health problem, whose multifactorial etiology challenges clinicians and researchers making necessary the collaboration between different experts and centers. The evaluation of the interference patterns observed in the tear film lipid layer is a common clinical test used for dry eye diagnosis. However, it is a time-consuming task with a high degree of intra- as well as inter-observer variability, which makes the use of a computer-based analysis system highly desirable. This work introduces iDEAS (Dry Eye Assessment System), a web-based application to support dry eye diagnosis.

METHODS

iDEAS provides a framework for eye care experts to collaboratively work using image-based services in a distributed environment. It is composed of three main components: the web client for user interaction, the web application server for request processing, and the service module for image analysis. Specifically, this manuscript presents two automatic services: tear film classification, which classifies an image into one interference pattern; and tear film map, which illustrates the distribution of the patterns over the entire tear film.

RESULTS

iDEAS has been evaluated by specialists from different institutions to test its performance. Both services have been evaluated in terms of a set of performance metrics using the annotations of different experts. Note that the processing time of both services has been also measured for efficiency purposes.

CONCLUSIONS

iDEAS is a web-based application which provides a fast, reliable environment for dry eye assessment. The system allows practitioners to share images, clinical information and automatic assessments between remote computers. Additionally, it save time for experts, diminish the inter-expert variability and can be used in both clinical and research settings.

Assessing ocular bulbar redness: a comparison of methods

PURPOSE

We consider whether quantification of ocular bulbar redness, using image processing of relative Red-channel activity (Red-value), can be applied to a clinical sample and how this approach compares to an automated bulbar redness grading technique (Oculus Keratograph 5M, R-scan).

METHODS

Red-values from dry eye patients (n = 25) were determined using image processing of digital photographs over the nasal bulbar conjunctiva. Red-values were compared with subjective grades from six clinicians who graded the images using the IER scale. We considered the level of agreement between the Red-value and automated bulbar redness scores from the commercial instrument (R-scan). Scoring variability for each technique was assessed using the geometric coefficient of variation (gCoV, %). Agreement between techniques was considered with Bland-Altman analyses.

RESULTS

Red-values showed a strong linear relationship (R(2) = 0.99) to the R-scan. The Red-value had least variability (gCoV = 0.97%, 95% CI: 0.76-1.35%). The IER grade showed a linear relationship with Red-value (R(2) = 0.99), bound by a floor effect; it did not discriminate changes in redness below a threshold of 1.75 units (Red-value = 33.0%), after which it paralleled the redness returned by the R-scan. Intra-method variability for the redness returned by the R-scan (gCoV = 9.84%, 95% CI: 7.60-13.94%) and IER grades (gCoV = 7.30%, 95% CI: 1.73-10.31%) was similar (p > 0.05). Bland-Altman analysis showed the R-scan was consistently biased towards lower absolute redness scores than the IER.

CONCLUSIONS

Digital imaging processing, using relative Red-channel activity, was the least variable of the three techniques. The R-scan and IER showed similar intra-observer variability. The linear relationship between R-scan and Red-value suggests that the R-scan could be derived using similar methods.

Comparison between live and photographed slit lamp grading of corneal staining

PURPOSE

To compare live and photographic (still) grades of corneal staining of the same eyes and the repeatability of grading between two investigators.

METHODS

Thirty patients were recruited to participate in a contact lens study, and their level of corneal staining was graded by two investigators in situ (live images), using slit lamp biomicroscopy. Digital still images of the corneal staining were also captured during the study visits. An independent observer selected 105 of the still images graded by investigator 1 and another 105 images graded by investigator 2 and presented them to the original investigator in a random order, on three separate occasions. Grading was performed at the time of the live grading and the three still image sessions, using the Centre for Contact Lens Research corneal staining scale that combines grades of both extent and type to provide an overall "global staining score" from 0 to 10,000 for corneal staining. A comparison was made between live and still grades as well as the intrainvestigator repeatability for the multiple grading of the still images.

RESULTS

The mean (±SD) of corneal staining grades recorded for the same eyes examined live and then later on three occasions was 1795 (±1083) and 714 (±974), respectively, for participants examined by investigator 1 (p < 0.001) and 1854 (±1075) and 461 (±411) for those examined by investigator 2 (p < 0.001). There was a significant difference over the three repeated still grading sessions for each investigator (p < 0.001), although there was a high degree of consistency among the three still grading sessions for each of the investigators: the intraclass correlation for investigator 1 was 0.91 (confidence interval, 0.87 to 0.93) and that for investigator 2 was 0.82 (confidence interval, 0.77 to 0.87).

DISCUSSION

Digital still image grading of corneal staining significantly underrepresented the amount of corneal staining observed through a slit lamp. Clinical investigators graded corneal staining with a high degree of consistency.

Anterior eye health recording

AIMS

To survey eye care practitioners from around the world regarding their current practice for anterior eye health recording to inform guidelines on best practice.

METHODS

The on-line survey examined the reported use of: word descriptions, sketching, grading scales or photographs; paper or computerised record cards and whether these were guided by proforma headings; grading scale choice, signs graded, level of precision, regional grading; and how much time eye care practitioners spent on average on anterior eye health recording.

RESULTS

Eight hundred and nine eye care practitioners from across the world completed the survey. Word description (p<0.001), sketches (p=0.002) and grading scales (p<0.001) were used more for recording the anterior eye health of contact lens patients than other patients, but photography was used similarly (p=0.132). Of the respondents, 84.5% used a grading scale, 13.5% using two, with the original Efron (51.6%) and CCLRU/Brien-Holden-Vision-Institute (48.5%) being the most popular. The median features graded was 11 (range 1-23), frequency from 91.6% (bulbar hyperaemia) to 19.6% (endothelial blebs), with most practitioners grading to the nearest unit (47.4%) and just 14.7% to one decimal place. The average time taken to report anterior eye health was reported to be 6.8±5.7 min, with the maximum time available 14.0±11 min.

CONCLUSIONS

Developed practice and research evidence allows best practice guidelines for anterior eye health recording to be recommended. It is recommended to: record which grading scale is used; always grade to one decimal place, record what you see live rather than based on how you intend to manage a condition; grade bulbar and limbal hyperaemia, limbal neovascularisation, conjunctival papillary redness and roughness (in white light to assess colouration with fluorescein instilled to aid visualisation of papillae/follicles), blepharitis, meibomian gland dysfunction and sketch staining (both corneal and conjunctival) at every visit. Record other anterior eye features only if they are remarkable, but indicate that the key tissue which have been examined.

Randomised masked clinical trial of the MGDRx EyeBag for the treatment of meibomian gland dysfunction-related evaporative dry eye

Background/aims

To investigate the efficacy and safety of the MGDRx EyeBag (The Eyebag Company, Halifax, UK) eyelid warming device.

Methods

Twenty-five patients with confirmed meibomian gland dysfunction (MGD)-related evaporative dry eye were enrolled into a randomised, single masked, contralateral clinical trial. Test eyes received a heated device; control eyes a non-heated device for 5 min twice a day for 2 weeks. Efficacy (ocular symptomology, non-invasive break-up time, lipid layer thickness, osmolarity, meibomian gland dropout and function) and safety (visual acuity, corneal topography, conjunctival hyperaemia and staining) measurements were taken at baseline and follow-up. Subsequent patient device usage and ocular comfort was ascertained at 6 months.

Results

Differences between test and control eyes at baseline were not statistically significant for all measurements (p>0.05). After 2 weeks, statistically significant improvements occurred in all efficacy measurements in test eyes (p<0.05). Visual acuity and corneal topography were unaffected (p>0.05). All patients maintained higher ocular comfort after 6 months (p<0.05), although the benefit was greater in those who continued usage 1–8 times a month (p<0.001).

Conclusions

The MGDRx EyeBag is a safe and effective device for the treatment of MGD-related evaporative dry eye. Subjective benefit lasts at least 6 months, aided by occasional retreatment.

Trial registration number

NCT01870180.

Development of automated conjunctival hyperemia analysis software

Conjunctival hyperemia is observed in a variety of ocular inflammatory conditions. The evaluation of hyperemia is indispensable for the treatment of patients with ocular inflammation. However, the major methods currently available for evaluation are based on nonquantitative and subjective methods. Therefore, we developed novel software to evaluate bulbar hyperemia quantitatively and objectively. First, we investigated whether the histamine-induced hyperemia of guinea pigs could be quantified by image analysis. Bulbar conjunctival images were taken by means of a digital camera, followed by the binarization of the images and the selection of regions of interest (ROIs) for evaluation. The ROIs were evaluated by counting the number of absolute pixel values. Pixel values peaked significantly 1 minute after histamine challenge was performed and were still increased after 5 minutes. Second, we applied the same method to antigen (ovalbumin)-induced hyperemia of sensitized guinea pigs, acquiring similar results except for the substantial upregulation in the first 5 minutes after challenge. Finally, we analyzed human bulbar hyperemia using the new software we developed especially for human usage. The new software allows the automatic calculation of pixel values once the ROIs have been selected. In our clinical trials, the percentage of blood vessel coverage of ROIs was significantly higher in the images of hyperemia caused by allergic conjunctival diseases and hyperemia induced by Bimatoprost, compared with those of healthy volunteers. We propose that this newly developed automated hyperemia analysis software will be an objective clinical tool for the evaluation of ocular hyperemia.

Objectifying the conjunctival provocation test: photography-based rating and digital analysis

BACKGROUND

Patients with allergic rhinoconjunctivitis are susceptible to both nasal and ocular symptoms. The conjunctival provocation test (CPT) is an established diagnostic procedure used in allergic rhinoconjunctivitis, particularly to document a patient's current reactivity to allergens. To date, there are no international guidelines defining the CPT. No approved evaluation method exists for interpreting CPT results. This paper aims to establish the digital analysis of macroimages as an objective, validated and standardized method for interpreting CPT results.

METHODS

In a clinical immunotherapy trial with 155 patients, treatment progress was documented based on the CPT. Local investigators used a symptom score to grade tearing, reddening and the patients' subjective perception of symptoms (mucosal irritation). A central observer rated conjunctival hyperemia via digital photography. Digital image analysis software was utilized to determine conjunctival hyperemia.

RESULTS

Spearman's correlation between the local investigators' and the central observer's ratings was r = 0.729 (p < 0.001); the percentage of total agreement was 48% (based on 739 photos). Digital image analysis (based on 48 photos) had a high percentage of total agreement with the central observer's ratings (69%) but a low percentage of total agreement with the investigators' ratings (38%). The corresponding correlations were r = 0.264 and 0.064, respectively.

CONCLUSION

Photography-based rating by a central observer may represent a valuable supplement to the local investigator's assessment for making an objective evaluation of CPT results. Digital image analysis possesses the potential of being an objective evaluation method compared to the wide-spread subjective evaluation by the investigators.

Image analyses of the kinetic changes of conjunctival hyperemia in histamine-induced conjunctivitis in Guinea pigs

BACKGROUND

Conjunctival hyperemia is the most common finding in patients with allergic conjunctivitis. Histamine is a typical chemical mediator involved in allergic conjunctivitis and induces hyperemia. Here, we investigated the kinetic changes in bulbar hyperemia induced by histamine in eyedrops.

METHODS

Male guinea pigs were challenged with histamine in eyedrops. Bulbar conjunctival images were taken every 10 seconds by a digital camera up to 8 minutes after histamine challenge, and the software program ImageJ was used to analyze the images. Images were binarized, and a region of interest unobscured by corneal and scleral vessels was selected as the evaluation area. Evaluations were carried out before and after histamine challenge by counting the numbers of absolute pixel values, percent changes in pixels, or the fractal dimension in acquired images.

RESULTS

After histamine challenge, the conjunctival vessel area continued to increase up to 5 minutes before stabilizing. The various parameters used to evaluate the images (numbers of absolute pixel values, percent change in pixels, or the fractal dimensions) markedly increased 1 minute after histamine challenge, gradually increased up to 5 minutes, and then gradually decreased before reaching a level that remained significantly higher than that before histamine challenge.

CONCLUSIONS

This is the first report to quantitatively evaluate bulbar hyperemia induced by histamine using image analysis. The development of software that can automatically yield meaningful values for hyperemia from hyperemia images will be a useful objective tool in clinical trials for evaluation of drug effects in animal models and in humans.

Objective grading of the anterior eye

PURPOSE

To convert objective image analysis of anterior ocular surfaces into recognisable clinical grades, in order to provide a more sensitive and reliable equivalent to current subjective grading methods; a prospective, randomized study correlating clinical grading with digital image assessment.

METHODS

The possible range of clinical presentations of bulbar and palpebral hyperaemia, palpebral roughness and corneal staining were represented by 4 sets of 10 images. The images were displayed in random order and graded by 50 clinicians using both subjective CCLRU and Efron grading scales. Previously validated objective image analysis was performed 3 times on each of the 40 images. Digital measures included edge-detection and relative-coloration components. Step-wise regression analysis determined correlations between the average subjective grade and the objective image analysis measures.

RESULTS

Average subjective grades could be predicted by a combination of the objective image analysis components. These digital "grades" accounted for between 69% (for Efron scale-graded palpebral redness) and 98% (for Efron scale-graded bulbar hyperaemia) of the subjective variance.

CONCLUSIONS

The results indicate that clinicians may use a combination of vessel areas and overall hue in their judgment of clinical severity for certain conditions. Objective grading can take these aspects into account, and be used to predict an average "objective grade" to be used by a clinician in describing the anterior eye. These measures are more sensitive and reliable than subjective grading while still utilizing familiar terminology, and can be applied in research or practice to improve the detection, and monitoring of ocular surface changes.

Sensitivity and reliability of objective image analysis compared to subjective grading of bulbar hyperaemia

AIMS

To establish the sensitivity and reliability of objective image analysis in direct comparison with subjective grading of bulbar hyperaemia.

METHODS

Images of the same eyes were captured with a range of bulbar hyperaemia caused by vasodilation. The progression was recorded and 45 images extracted. The images were objectively analysed on 14 occasions using previously validated edge-detection and colour-extraction techniques. They were also graded by 14 eye-care practitioners (ECPs) and 14 non-clinicians (NCLs) using the Efron scale. Six ECPs repeated the grading on three separate occasions

RESULTS

Subjective grading was only able to differentiate images with differences in grade of 0.70-1.03 Efron units (sensitivity of 0.30-0.53), compared to 0.02-0.09 Efron units with objective techniques (sensitivity of 0.94-0.99). Significant differences were found between ECPs and individual repeats were also inconsistent (p<0.001). Objective analysis was 16x more reliable than subjective analysis. The NCLs used wider ranges of the scale but were more variable than ECPs, implying that training may have an effect on grading.

CONCLUSIONS

Objective analysis may offer a new gold standard in anterior ocular examination, and should be developed further as a clinical research tool to allow more highly powered analysis, and to enhance the clinical monitoring of anterior eye disease.

The Relation between Physical Properties of the Anterior Eye and Ocular Surface Temperature

PURPOSE

To examine the relation between ocular surface temperature (OST) assessed by dynamic thermal imaging and physical parameters of the anterior eye in normal subjects.

METHODS

Dynamic ocular thermography (ThermoTracer 7102MX) was used to record body temperature and continuous ocular surface temperature for 8 s after a blink in the right eyes of 25 subjects. Corneal thickness, corneal curvature, and anterior chamber depth (ACD) were assessed using Orbscan II; noninvasive tear break-up time (NIBUT) was assessed using the tearscope; slit lamp photography was used to record tear meniscus height (TMH) and objective bulbar redness.

RESULTS

Initial OST after a blink was significantly correlated only with body temperature (r=0.80, p<0.0005), NIBUT (r=-0.68, p<0.005) and corneal curvature (r=-0.40, p=0.05). A regression model containing all the variables accounted for 70% (p=0.002) of the variance in OST, of which NIBUT (29%, p=0.004), and body temperature (18%, p=0.005) contributed significantly.

CONCLUSIONS

The results support previous theoretical models that OST radiation is principally related to the tear film; and demonstrate that it is less related to other characteristics such as corneal thickness, corneal curvature, and anterior chamber depth.

Comparison of an objective method of measuring bulbar redness to the use of traditional grading scales

PURPOSE

The primary objective was to compare measures of bulbar redness objectively using a photometric method with standard grading methods. Measures of redness were made on 24 participants wearing a silicone hydrogel contact lens in one eye for overnight wear. This report compares hyperaemia after 1 week of daily wear (baseline) with redness measured after 6 months of overnight wear.

METHOD

A new method of objectively measuring bulbar conjunctival redness was performed using the Spectrascan650 Photometer by Photo Research under fixed illumination. Photometric measures in CIEu(*) chromaticity values involve the measurement of chromaticity, a physical analogue of redness, greenness and blueness in the image. This method was validated in Part 1 of the study using repeated measurements on the photographic CCLRU scale. In Part 2 of the study, the photographic grading scale (CCLRU) from 0 (none) to 100 (extreme) was used to make the comparison.

RESULTS

Part 1 indicated that the photometer provides a repeatable and reliable measure of bulbar redness (CCC=0.989). A moderately strong and significant correlation was found between the CIEu(*) chromaticity values and the analogue data (R=0.795, p=0.000) at each measurement session (from baseline to 1 day, 1 week, and 1, 3 and 6 months of overnight wear).

CONCLUSIONS

This new standardized and objective method of measuring bulbar redness has great potential to replace subjective grading scales, especially with multi-centre studies, where variability between investigators occurs. This method may also detect smaller changes between visits or between eyes.

Clinical performance of daily disposable soft contact lenses using sustained release technology

PURPOSE

Polyvinyl alcohol (PVA) is a successful tear film stabiliser and is widely used in comfort drops and some soft contact lens materials. A PVA-containing lens, nelfilcon A has been modified to include additional (non-functional) PVA in order to provide improved comfort. This study aims to examine the clinical performance of this nelfilcon A lens with AquaRelease (AquaRelease).

METHODS

Two contralateral, investigator masked, open label, subjective and objective evaluations were conducted. The first examined the effect of adding increased molecular weight PVA to nelfilcon A (n=5), and the second compared this AquaRelease lens to ocufilcon B (n=34). The principal measures were non-invasive break-up time (NIBUT) and subjective comfort, which were assessed at the beginning and end of a week of daily wear, and three times throughout 1 day at 8, 12 and 16 h.

RESULTS

All subjects successfully completed the daily wearing schedule of 16h. On initial insertion, subjective comfort and NIBUT improved for AquaRelease than original nelfilcon A lenses (p<0.05). Initial comfort was better for AquaRelease compared to ocufilcon B lenses (p=0.01); however, NIBUT was not statistically different (11.7+/-15.6s versus 8.4+/-6.8s; p=0.26). Subjective comfort decreased with time (p<0.001), but there was no significant difference between AquaRelease and ocufilcon B lenses (p=0.16). NIBUT was not significantly affected by time (p=0.56) or between lenses (p=0.33). At the end of a weeks' wear, subjective initial, end-of-day, overall comfort and vision were rated significantly better with AquaRelease than ocufilcon B (p<0.01).

CONCLUSIONS

Release of additional non-functionalised PVA from the nelfilcon A lenses appears to enhance comfortable contact lens wear.

How red is a white eye? Clinical grading of normal conjunctival hyperaemia

PURPOSE

To quantify the level of normal bulbar conjunctival hyperaemia using the Cornea and Contact Lens Research Unit (CCLRU) grading scale, and to investigate inter-observer agreement.

METHODS

Bulbar conjunctival hyperaemia was assessed by two trained observers, using the CCLRU grading scale (zero to four units) interpolated into 0.1 increments, on the right eye of 121 healthy, non-contact lens-wearing subjects (male=58, female=63, median age=28 years, range 16-77). The eye was observed using a slit-lamp bio-microscope (x 10 magnification) under diffuse, white illumination. The subject's position of gaze was directed to allow grading of four quadrants: superior, nasal, inferior, and temporal conjunctiva. Bulbar redness was defined as the average of those four grades of conjunctival hyperaemia. A further twenty subjects were recruited to assess inter-observer agreement (male=8, female=12, median age=23 years).

RESULTS

The average bulbar redness was 1.93 (+/-0.32 SD) units. The nasal (2.3+/-0.4) and temporal (2.1+/-0.4) quadrants were significantly redder than the superior (1.6+/-0.4) and inferior (1.7+/-0.4) quadrants (P<0.0001). Males had redder eyes than females by 0.2 units. Inter-observer 95% limits of agreement for bulbar redness was 0.38 units.

CONCLUSIONS

The average bulbar redness of 1.9 units was higher than expected, reflecting the design of the grading scale. A bulbar redness of greater than 2.6 units may be considered abnormal, and a change in bulbar redness of > or =0.4 units may be significant.

Changes in Ocular Physiology, Tear Film Characteristics, and Symptomatology With 18 Months Silicone Hydrogel Contact Lens Wear

PURPOSE

The purpose of this study was to evaluate the longitudinal changes in ocular physiology, tear film characteristics, and symptomatology experienced by neophyte silicone hydrogel (SiH) contact lens wearers in a daily-wear compared with a continuous-wear modality and with the different commercially available lenses over an 18-month period.

METHODS

Forty-five neophyte subjects were enrolled in the study and randomly assigned to wear one of two SiH materials: lotrafilcon A or balafilcon A lenses on either a daily- (LDW; BDW) or continuous-wear (LCW; BCW) basis. Additionally, a group of noncontact lens-wearing subjects (control group) was also recruited and followed over the same study period. Objective and subjective grading of ocular physiology were carried out together with tear meniscus height (TMH) and noninvasive tear breakup time (NITBUT). Subjects also subjectively rated symptoms and judgments with lens wear. After initial screening, subsequent measurements were taken after 1, 3, 6, 12, and 18 months.

RESULTS

Subjective and objective grading of ocular physiology revealed a small increase in bulbar, limbal, and palpebral hyperemia as well as corneal staining over time with both lens materials and regimes of wear (p < 0.05). No significant changes in NITBUT or TMH were found (p > 0.05). Subjective symptoms and judgment were not material- or modality-specific.

CONCLUSIONS

Daily and continuous wear of SiH contact lenses induced small but statistically significant changes in ocular physiology and symptomatology. Clinical measures of tear film characteristics were unaffected by lens wear. Both materials and regimes of wear showed similar clinical performance. Long-term SiH contact lens wear is shown to be a successful option for patients.

The effect of digital image resolution and compression on anterior eye imaging

AIM

To determine the theoretical and clinical minimum image pixel resolution and maximum compression appropriate for anterior eye image storage.

METHODS

Clinical images of the bulbar conjunctiva, palpebral conjunctiva, and corneal staining were taken at the maximum resolution of Nikon:CoolPix990 (2048x1360 pixels), DVC:1312C (1280x811), and JAI:CV-S3200 (767x569) single chip cameras and the JVC:KYF58 (767x569) three chip camera. The images were stored in TIFF format and further copies created with reduced resolution or compressed. The images were then ranked for clarity on a 15 inch monitor (resolution 1280 x 1024) by 20 optometrists and analysed by objective image analysis grading. Theoretical calculation of the resolution necessary to detect the smallest objects of clinical interest was also conducted.

RESULTS

Theoretical calculation suggested that the minimum resolution should be > or = 579 horizontal pixels at 25x magnification. Image quality was perceived subjectively as being reduced when the pixel resolution was lower than 767 x 569 (p<0.005) or the image was compressed as a BMP or <50% quality JPEG (p<0.005). Objective image analysis techniques were less susceptible to changes in image quality, particularly when using colour extraction techniques.

CONCLUSION

It is appropriate to store anterior eye images at between 1280 x 811 and 767 x 569 pixel resolution and at up to 1:70 JPEG compression.

The effect of contact lens wear on dynamic ocular surface temperature

AIM

To determine the dynamic emitted temperature changes of the anterior eye during and immediately after wearing different materials and modalities of soft contact lenses.

METHOD

A dynamic, non-contact infrared camera (Thermo-Tracer TH7102MX, NEC San-ei) was used to record the ocular surface temperature (OST) in 48 subjects (mean age 21.7 +/- 1.9 years) wearing: lotrafilcon-A contact lenses on a daily wear (LDW; n=8) or continuous wear (LCW; n=8) basis; balafilcon-A contact lenses on a daily wear (BDW; n=8) or continuous wear (BCW; n=8) basis; etafilcon-A contact lenses on a daily disposable regimen (EDW; n=8); and no lenses (controls; n=8). OST was measured continuously five times, for 8s after a blink, following a minimum of 2h wear and immediately following lens removal. Absolute temperature, changes in temperature post-blink and the dynamics of temperature changes were calculated.

RESULTS

OST immediately following contact lens wear was significantly greater compared to non-lens wearers (37.1 +/- 1.7 degrees C versus 35.0 +/- 1.1 degrees C; p < 0.005), predominantly in the LCW group (38.6 +/- 1.0 degrees C; p < 0.0001). Lens surface temperature was highly correlated (r=0.97) to, but lower than OST (by -0.62 +/- 0.3 degrees C). There was no difference with modality of wear (DW 37.5 +/- 1.6 degrees C versus CW 37.8+/-1.9 degrees C; p=0.63), but significant differences were found between etafilcon A and silicone hydrogel lens materials (35.3 +/- 1.1 degrees C versus 37.5 +/- 1.5 degrees C; p < 0.0005). Ocular surface cooling following a blink was not significantly affected by contact lens wear with (p=0.07) or without (p=0.47) lenses in situ.

CONCLUSIONS

Ocular surface temperature is greater with hydrogel and greater still with silicone hydrogel contact lenses in situ, regardless of modality of wear. The effect is likely to be due to the thermal transmission properties of a contact lens.

Incremental nature of anterior eye grading scales determined by objective image analysis

AIM

To use previously validated image analysis techniques to determine the incremental nature of printed subjective anterior eye grading scales.

METHODS

A purpose designed computer program was written to detect edges using a 3 x 3 kernal and to extract colour planes in the selected area of an image. Annunziato and Efron pictorial, and CCLRU and Vistakon-Synoptik photographic grades of bulbar hyperaemia, palpebral hyperaemia roughness, and corneal staining were analysed.

RESULTS

The increments of the grading scales were best described by a quadratic rather than a linear function. Edge detection and colour extraction image analysis for bulbar hyperaemia (r2 = 0.35-0.99), palpebral hyperaemia (r2 = 0.71-0.99), palpebral roughness (r2 = 0.30-0.94), and corneal staining (r2 = 0.57-0.99) correlated well with scale grades, although the increments varied in magnitude and direction between different scales. Repeated image analysis measures had a 95% confidence interval of between 0.02 (colour extraction) and 0.10 (edge detection) scale units (on a 0-4 scale).

CONCLUSION

The printed grading scales were more sensitive for grading features of low severity, but grades were not comparable between grading scales. Palpebral hyperaemia and staining grading is complicated by the variable presentations possible. Image analysis techniques are 6-35 times more repeatable than subjective grading, with a sensitivity of 1.2-2.8% of the scale.

Drug-induced bilateral transient myopia with the sulphonamide sulphasalazine

Whereas there are numerous reported ocular side effects from systemic sulpha medication, most are rare and reversible, with myopia being the most common reaction observed. A case report is presented of sudden bilateral onset of -1.0 DS of myopia (from -3.0 to -4.0 DS) in a young adult female following the addition of a sulphonamide (sulphasalazine) to oral non-steroidal anti-inflammatory treatment (meloxicam) for rheumatoid arthritis. The myopia regressed to -3.50 DS after 2 weeks when all medication was withdrawn and stabilised at this level when subsequent treatment was resumed after 8 weeks with the non-steroidal anti-inflammatory drug celecoxib. The case indicates that account needs to be taken of the possibility that relatively modest myopic shifts encountered in young adult contact lens wearers may be associated with concomitant systemic medication.