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Abdul-Jabbar Ghauri, Imran J. Khan, James Hodson, Paul Cottrell, Matthew R. Edmunds, Simon Evans, Geraint P. Williams, Saaeha Rauz; Defining Normal Fornix Limits in the South Asian Population. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1866.
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Measurement of forniceal shortening can facilitate clinical assessment of conjunctival scarring disorders. To date, normal limits of the human fornix and how this alters with age is unknown. This study aims to define the normal range of upper and lower fornix depths (FD) and fornix intercanthal distance (FICD) within a South Asian population.
A FICD modification of a custom-designed fornix depth measurer (FDM) was validated for FICD measurements by two independent observers in 40 eyes and agreement was calculated using Bland-Altman comparison. FD and FICD were measured in triplicate in a healthy South Asian Population. Sample size calculations indicated that 480 eyes (80 eyes per decade) would be sufficient to calculate means with 95% confidence interval (CI) widths of <0.8mm. Data were analysed using a repeated measures ANOVA, with p-values <0.05 were treated as significant.
There was 100% intra-observer agreement within 1mm for each observer FICD measurements. All of the measurements taken by the observers agreed by ± 10% of upper and lower FICD. In our study population, the overall upper and lower FD and FICD were measured to be 15.3( 14.9 - 15.6) mm, 10.9(10.7 - 11.1) mm, 32.9 (32.5 - 33.4) mm and 31.7 (31.3 - 32.1) mm (mean (95% CI)), respectively. There was a progressive reduction for all measurements across the decades of age (p<0.001) (Table 1), with females having smaller forinices (upper FD (p<0.001), lower FD (p<0.001), upper FICD (p=0.081), lower FICD (p=0.015)). There was no significant interaction between age and gender for any of the measurements.
This is the first study to define limits of normal upper and lower FD and FICD in any population, and shows not only gender variations, but also conjunctival shrinkage with age in our healthy South Asian study group. Our analyses provide objective anthropological data of normal forniceal anatomy. Further studies in other populations (White-Caucasian, Asian-Chinese, African-Caribbean etc) are required to enable normal comparative datasets for the assessment of cicatrising conjunctivides.
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