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

Abstract

Background/aimsDocumentation 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.MethodsA 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.ResultsFifty-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.ConclusionsThis 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.

Upper and lower conjunctival fornix depth in healthy white caucasian eyes: a method of objective assessment

“…Notably, Reeves et al describe increased variability in their method when there are lesser degrees of conjunctival involvement, and it has been found by others that interobserver agreement for this method is less consistent. 7 Furthermore, it is not possible to evaluate scarring of the upper conjunctival fornix with this method.…”

“…Some have produced a plastic fornix depth measurer (FDM) engraved by jewelry software 7 or a metal rod. 8 Others have used a ruler in different aspects of gaze 4 or the slit lamp beam.…”

Ocular and oral grading of mucous membrane pemphigoid

“…This means that measuring forniceal depth along the post-tarsal aspect principally measures conjunctival shrinkage below the tarsus. More recently, Kawakita et al and then Williams et al introduced a metric rule behind the lid margin for measurement of forniceal depth [12,13]. While this would appear to offer some advantages, it is still based upon measurement of the fornix from the tarsal aspect.…”

“…In contrast to the availability of oral grading systems, a number of systems have been described to measure involvement of the ocular surface in MMP [2,[9][10][11][12]. The systems of Mondino, Foster, and the modifications described by Tauber grade the percentage loss of conjunctival forniceal depth by estimating the reduction in distance from the posterior lower lid margin to the fornix [2,9,10].…”

Mucous Membrane Pemphigoid

“…Although there are several ocular grading systems for the severity of MMP, including Foster, Mondino and Tauber, none of these systems is universally accepted. [41][42][43] Reeves et al recently reported a grading system for both oral and ocular involvement, and no correlation in severity was found between the oral and ocular disease. 44 …”