Optimizing OCT acquisition parameters for assessments of vitreous haze for application in uveitis.

Detection and evaluation of inflammatory activity in uveitis is essential to the management of the condition, and yet continues to be largely dependent on subjective clinical measures. Optical coherence tomography (OCT) measurement of vitreous activity is an alternative to clinical vitreous haze scoring and has passed a number of early validation studies. In this study we aimed to evaluate the impact of 'operator factors' on the variability of the technique as part of the validation process, and to help evaluate its suitability for 'real world' use. Vitreous haze index was calculated as a ratio between the reflectivity of the vitreous and of the outer retina in each scan. Different scanning conditions were tested and their effect on the measurement is reported. Our results show that the 'quantitative imaging' technique of OCT-measured vitreous activity had good reliability in normal subjects under a range of 'real world' conditions, such as when the operator changes the averaging value. The technique was however vulnerable to highly inaccurate focussing or abnormal downward displacement of the image. OCT-based quantification of vitreous activity is a promising alternative to current subjective clinical estimates, with sufficient 'tolerance' to be used in routine clinical practice as well as clinical trials.

New superior-inferior visual field asymmetry indices for detecting POAG and their agreement with the glaucoma hemifield test.

PURPOSE: To describe and measure the discriminatory performance of three new superior-inferior asymmetry indices for detecting primary open angle glaucoma (POAG) and to compare these with the glaucoma hemifield test (GHT). METHODS: In all, 412 control and 247 POAG eyes were selected from a visual field database of patients attending the Manchester Royal Eye Hospital. Age-adjusted defect asymmetries were calculated for each of the 22 vertically mirrored test point pairs used in the GHT. The three new indices, hemifield mean difference (HMD) and hemifield standard deviation (HSD) of the asymmetry values along with the number of test pairs (NP) falling outside the 85% probability limits of the control population, were calculated. ROC curves of the indices and GHT were constructed. Agreement between the indices was explored with a proportional Venn diagram and 3 × 3 contingency tables. Cases of disagreement between the indices were reviewed. RESULTS: The area under the ROC curves were HMD=0.745 (95% confidence interval (CI) 0.705-0.786), HSD=0.864 (95% CI 0.833-0.894), NP=0.863 (95% CI 0.832-0.893) and GHT=0.792 (95% CI 0.754-0.829). The Venn diagram and contingency tables highlighted the good agreement between HSD, NP and GHT. Agreement was 78% (HSD vs. GHT) and 82% (NP vs. GHT) in the control sample and 70% (HSD vs. GHT) and 71% (NP vs. GHT) in the POAG sample. Five cases are presented where disagreement existed between the indices. CONCLUSIONS: The new HSD and NP asymmetry indices perform better than GHT in differentiating between normal and POAG eyes in this data set. GHT can fail to detect significant asymmetry, detected by HSD and NP, when an early defect crosses sector boundaries.

Comparison of three screening tools to detect psoriatic arthritis in patients with psoriasis (CONTEST study).

BACKGROUND: Multiple questionnaires to screen for psoriatic arthritis (PsA) have been developed but the optimal screening questionnaire is unknown. OBJECTIVES: To compare three PsA screening questionnaires in a head-to-head study using CASPAR (the Classification Criteria for Psoriatic Arthritis) as the gold standard. METHODS: This study recruited from 10 U.K. secondary care dermatology clinics. Patients with a diagnosis of psoriasis, not previously diagnosed with PsA, were given all three questionnaires. All patients who were positive on any questionnaire were invited for a rheumatological assessment. Receiver operating characteristic (ROC) curves were used to compare the sensitivity, specificity and area under the curve of the three questionnaires according to CASPAR criteria. RESULTS: In total, 938 patients with psoriasis were invited to participate and 657 (70%) patients returned the questionnaires. One or more questionnaires were positive in 314 patients (48%) and 195 (62%) of these patients attended for assessment. Of these, 47 patients (24%) were diagnosed with PsA according to the CASPAR criteria. The proportion of patients with PsA increased with the number of positive questionnaires (one questionnaire, 19·1%; two, 34·0%; three, 46·8%). Sensitivities and specificities for the three questionnaires, and areas under the ROC curve were, respectively: Psoriatic Arthritis Screening Evaluation (PASE), 74·5%, 38·5%, 0·594; Psoriasis Epidemiology Screening Tool (PEST), 76·6%, 37·2%, 0·610; Toronto Psoriatic Arthritis Screen (ToPAS), 76·6%, 29·7%, 0·554. The majority of patients with a false positive response had degenerative or osteoarthritis. CONCLUSION: Although the PEST and ToPAS questionnaires performed slightly better than the PASE questionnaire at identifying PsA, there is little difference between these instruments. These screening tools identify many cases of musculoskeletal disease other than PsA.

Contextual detection of ischemic regions in ultra-wide-field-of-view retinal fluorescein angiograms.

We report a novel prototype algorithm using contextual knowledge to locate ischemic regions in ultra-wide-field-of-view retinal fluorescein angiograms. We use high-resolution images acquired by an Optos ultra-wide-field-of-view (more than 200 degrees) scanning laser ophthalmoscope. We leverage the simultaneous occurrence of ischemia with a number of other signs, detected automatically, typical for the state of progress of the condition in a diabetic patient. The specific nature of ischemic and non-ischemic regions is determined with an AdaBoost learning algorithm. Preliminary results demonstrate above 80% pixel classification accuracy against manual annotations.

Statistical strategies to assess reliability in ophthalmology.

Reliability of measurements and measurers is important so that we can trust the measurements we record. However, the statistical techniques used to assess reliability of measurements or measurers in the ophthalmic literature are often inappropriate, and not able to evaluate reliability between measurements/measurers. We review the techniques used in reliability studies for both continuous and categorical data, and describe appropriate statistical methods for particular study designs. We also highlight current techniques that are not appropriate in the analysis of reliability, but that are still commonly used in the ophthalmic literature. We hope that by highlighting these, we shall discourage their future use.

Development of a forced choice photographic questionnaire for photic phenomena and its testing - repeatability, reliability and validity.

AIM: To design, develop and test a system for analysis of photic phenomena. METHOD: Extensive background research, patient interviews and theoretical studies led to development of a set of photographic images resembling photic phenomena experienced by patients. These photographic images were processed and digitally altered to create scales of severity for each photic phenomenon in which patients indicated their severity of symptoms by choice of image. The system was tested for stability and validity. RESULTS: The system showed excellent repeatability and reliability. Face, content, criterion and construct validity were all found to be acceptable. CONCLUSION: The photographic images of photic phenomena analyser is an acceptable, validated measure for the assessment of photic phenomena, in both pseudophakic patients and those with cataract.

The development and assessment of a self-perceived quality of vision questionnaire to test pseudophakic patients.

PURPOSE: To develop and test a questionnaire to assess quality of vision in pseudophakic patients. METHODS: The problems with existing health measurement scales and the need for a new questionnaire are first discussed. Development of the new questionnaire from concept to completion is presented and all stages discussed. The questionnaire is then tested for internal consistency, reliability and validity. RESULTS: The Cronbach Alpha for internal consistency was 0.92. British Standards Institution repeatability coefficient was satisfactory at 6.6. Discriminant construct validity testing by extreme groups demonstrated excellent discrimination between patients with functionally significant posterior capsule opacification (PCO) and no significant PCO (Mann-Whitney U test, p = 0.001). CONCLUSION: The questionnaire is validated as a robust, stable measure of pseudophakic visual symptoms with a high degree of clinical utility. It should be invaluable for the many studies that compare outcomes from different forms of modern cataract surgery with implantation of different intraocular lenses.

Systems of analysis of posterior capsule opacification.

This paper demonstrates the wide variety of systems for the analysis of posterior capsular opacification (PCO). No single system has been proved to be a gold standard and it is difficult to comment on the advantages of one system over another with the limited current knowledge on the effects of PCO on vision. There are few studies that actually compare the different systems of analysis. Researchers must ensure that the systems they use for PCO analysis are objective and must give maximum consideration to ensuring potential systematic errors are reduced to a minimum. Further research is required into how the various types and locations of PCO affect vision and how well different systems of analysis perform.