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Validation of a fornix depth measurer: a putative tool for the assessment of progressive cicatrising conjunctivitis

Williams, Geraint P. and Saw, Valerie P J and Saeed, Tariq and Evans, Simon T and Cottrell, Paul and Curnow, S. John and Nightingale, Peter and Rauz, Saaeha (2010) Validation of a fornix depth measurer: a putative tool for the assessment of progressive cicatrising conjunctivitis. British Journal of Ophthalmology. ISSN 0007-1161

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URL of Published Version: http://dx.doi.org/10.1136/bjo.2010.188011

Identification Number/DOI: 10.1136/bjo.2010.188011

Background/aims Documentation of conjunctival forniceal foreshortening in cases of progressive cicatrising conjunctivitis (PCC) is important in ascertaining disease stage and progression. Lower fornix shortening is often documented subjectively or semi-objectively, whereas upper forniceal obliteration is seldom quantified. Although tools such as fornix depth measurers (FDMs) have been described, their designs limit upper fornix measurement. The purpose of this study was to custom-design a FDM to evaluate the upper fornix and to assess variability in gauging fornix depth.

Methods A polymethylmethacrylate FDM was constructed using industry-standard jewellery computer software and machinery. Two observers undertook a prospective independent evaluation of central lower fornix depth in a heterogeneous cohort of patients with clinically normal and abnormal conjunctival fornices both subjectively and by using the FDM (in mm). Upper central fornix depth was also measured. Agreement was assessed using Bland–Altman plots.

Results Fifty-one eyes were evaluated. There was 100% intraobserver agreement to within 1 mm for each observer for lower fornix measurement. The mean difference in fornix depth loss using the FDM between observer 1 and 2 was 1.19%, with 95% confidence of agreement (±2SD) of −15% to +20%. In total, 86% (44/51) of measurements taken by the two observers agreed to within 10% of total lower fornix depth (ie, ±1 mm) versus only 63% (32/51) of the subjective measurements. Mean upper fornix difference was 0.57 mm, with 95% confidence of agreement of between −2 and + 3 mm.

Conclusions This custom-designed FDM is well tolerated by patients and shows low intraobserver and interobserver variability. This enables repeatable and reproducible measurement of upper and lower fornix depths, facilitating improved rates of detection and better monitoring of progression of conjunctival scarring.

Type of Work:Article
Date:17 October 2010 (Publication)
School/Faculty:Colleges (2008 onwards) > College of Life & Environmental Sciences
Department:Academic Unit of Ophthalmology, School of Immunity and Infection
Subjects:RE Ophthalmology
Institution:University of Birmingham
Copyright Holders:BMJ Publishing Group
ID Code:584
Refereed:YES
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