Quantitative Conjunctival Provocation Test for Controlled Clinical Trials

Abstract

SummaryBackground: The conjunctival provocation test (CPT) is a diagnostic procedure for the assessment of allergic diseases. Photographs are taken before and after provocation increasing the redness of the conjunctiva due to hyperemia. Objective: We propose and evaluate an automatic image processing pipeline for objective and quantitative CPT. Method: After scale normalization based on intrinsic image features, the conjunctiva region of interest (ROI) is segmented combining thresholding, edge detection and Hough transform. Redness of the ROI is measured from 0 to 1 by the average pixel redness, which is defined by truncated projection in HSV space. In total, 92 images from an observational diagnostic study are processed for evaluation. The database contains images from two visits for assessment of the test-retest reliability (46 images per visit). Result: All images were successfully processed by the algorithm. The relative redness increment correlates between the two visits with Pearson's r = 0.672 (p < .001). Linear correlation of the automatic measure is larger than the manual measure (r = 0.59). This indicates a higher reproducibility and stability of the automatic method. Conclusion:We presented a robust and effective way to objectify CPT. The algorithm operates on low resolution, is fast and requires no manual input. Quantitative CPT measures can now be established as surrogate endpoint in controlled clinical trials.

Liposomal Eye Spray Is as Effective as Antihistamine Eye Drops in Patients with Allergic Rhinoconjunctivitis Induced by Conjunctival Provocation Testing

“…Thus, digital analysis presents itself as a very sensitive method for evaluating the redness of the eye. The benefit and purpose of digital analysis have been demonstrated in multiple studies [29, 30]. This objective method for evaluating the relief of eye irritation further confirms the subjective patient evaluation and thus strengthens the hypothesis that LS is as effective as AD in reducing allergy symptoms.…”

Digitally Analyzed Conjunctival Redness: Does Repeated Conjunctival Provocation Intrinsically Cause Local Desensitization of the Eye?

“…(1) The conjunctival region of interest (ROI) to be analyzed was chosen manually using NIH ImageJ software (the iris and eyelids were excluded). As the bulbar position may have varied slightly in the images of one CPT series [20], it was important to display all pictures from 1 visit simultaneously, in order to determine the conjunctival intersection set visible in all of them. (2) After performing white balance, the ACE algorithm was applied to identify conjunctival vessels.…”

Reliability of a New Symptom Score in a Titrated Quantitative Conjunctival Provocation Test Supported by an Objective Photodocumentation

“…To enable an objective evaluation of the clinical reactions after the CPT, the eye reaction was documented in a high-resolution (4,032 × 3,042 pixels) macroimage that was analyzed using a MATLAB software program to calculate the degree of redness in percent developed by Astvatsatourov and Mösges [33] (alternative redness reconstruction was applied by Sárándi et al [34]). For this purpose, a photograph was taken before testing and 10 min after each provocation, respectively.…”