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

Abstract

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 166 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.A ssessment of conjunctival hyperaemia is a vital part of any ophthalmic evaluation. The onset of hyperaemia can indicate not only ocular but also certain systemic conditions 1-3 and hence it is vital that the subtle variations in this surface are evaluated and monitored by clinicians as accurately as possible. The current best practice for such assessment is in the form of subjective grading scales that were introduced to reduce inconsistencies between examiners and to encourage uniform grading of the anterior eye.4-6 The level on the scale (commonly 4-5 predetermined images) that best matches the characteristic of the eye under observation is recorded, ideally to 1dp to improve discrimination. 7 However, these scales remain (by their nature) subjective and lead to inherently variable assessments, with a wide range of the scale utilised by different practitioners to describe the same image.5 8Practitioners also demonstrate a reluctance to interpolate between the grading images displayed, even if training has been undertaken. 9 This is compounded by the design of the scales themselves which are not linear in nature, instead having increased sensitivity at the lower end, although this is not always consistent. 8To improve this situation various studies have investigated computer-based objective grading of ocular surfaces. With respect to vascular changes, several parameters have been the focus of objective analysis software.10 11 Edge detection and colour extraction have been shown to be the most repeatable and discriminatory of those techniques, and have been found to be approximately 76 more reliable than that reported for subjective grading, 11 h...

Anterior eye health recording

“…1 Subjective grading has been extensively used to quantify and monitor ocular features such as bulbar hyperemia, palpebral roughness and corneal staining with sodium fluorescein (Efron, 1998 [6][7][8][9] although the range of possible features to grade is vast and there is no widely accepted guidance on which features should always be graded and which should be added when marked pathology is noted. Despite best efforts however, the sensitivity and reliability of the resulting assessments has been shown to be limited, 10,11 with natural bias such as to whole numbers. Longer time dedicated to grading generally reduced the variation between individuals, but a couple of seconds was sufficient for most pathological features.…”

“…10,16,17 However, image analysis techniques can predict the average experienced clinician grade, 2 but are many times more sensitive and reliable than subjective grading. 18 As the current practice for anterior eye health recording is not known, this study builds on previous studies to improve the evaluation and recording of soft and gas permeable contact lens fit 19,20 by surveying eye care practitioners from around the world in order to inform guidelines on best practice. The number of features of the anterior eye graded had a median of 11 and range of 1 to 23 features ( Table 1).…”

Objectifying the Conjunctival Provocation Test: Photography-Based Rating and Digital Analysis

“…One of the reasons for this is that only little attention has been given to allergic conjunctivitis compared to other atopic disorders such as allergic rhinitis or asthma [16], although ocular symptoms occur in up to 70% of allergic rhinitis patients [17]. Different methods for evaluating CPT results are available: grading scales that take the local investigators' assessment and the patient's subjective perception of symptoms into account [7], photographic documentation of patients' eyes and rating of such images by an observer [18,19], or rating by means of digital image analysis software [20]. However, none of these methods is a generally accepted tool for interpreting CPT results [10].…”

Intraocular Pressure and Conjunctival Hyperaemia with Bimatoprost Every 48 Hours Versus Every 24 Hours

“…16 As conjunctival hyperaemia with bimatoprost is highest during the first weeks and then diminishes by three months 17 , a reduced dose of bimatoprost may be better tolerated in the first weeks, whereas the standard regimen could be recommended later. We are aware that the method of subjectively grading ocular hyperaemia from direct observation 18 or colour photographs 8 is less sensitive and reliable than objective image analysis, 19 which requires appropriate software and instrumentation unavailable to us. Adherence and persistence is likely to be worse with prescriptions other than daily dosing.…”