Validation of a Fornix Depth Measurer - A Putative Tool for the Assessment of Progressive Cicatrising Conjunctivitis

Geraint P. Williams (1) , Valerie P.J. Saw (2) , Tariq Saeed (1) , Simon T. Evans (3) , Paul Cottrell (4) , S. John Curnow (1) , Peter Nightingale (5) , Saaeha Rauz (1)

1 Academic Unit of Ophthalmology, University of Birmingham
2 Moorfields Eye Hospital
3 Diamond Centre of Wales
4 Birmingham and Midland Eye Centre
5 Wellcome Trust Clinical Research Facility, Queeh Elizabeth Hospital, Birmingham

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 frequently 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: 51 eyes were evaluated. There was 100% intra-observer agreement to within 1mm 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%. 86%(44/51) of measurements taken by the two observers agreed to within 10% of total lower fornix depth (i.e. ±1mm) versus only 63%(32/51) of the subjective measurements. Mean upper fornix difference was 0.57mm with 95% agreement between -2 and + 3mm. Conclusions: Our custom-designed FDM is well tolerated by patients and demonstrates low intra- and inter-observer variability. This enables repeatable and reproducible measurements of upper and lower fornix depths, facilitating improved rates of detection and better monitoring of progression of conjunctival scarring.

Mots clés: Conjunctiva; Inflammation; Diagnostic tests/Investigation; Treatment Medical

Geraint P. Williams, Valerie P.J. Saw, Tariq Saeed, Simon T. Evans, Paul Cottrell, et al.. Validation of a Fornix Depth Measurer - A Putative Tool for the Assessment of Progressive Cicatrising Conjunctivitis. British Journal of Ophthalmology, 2010, 95 (6), pp.842. ⟨10.1136/bjo.2010.188011⟩. ⟨hal-00595939⟩