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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/21818

Title: The Sclerotic Scatter Limbal Arc Is More Easily Elicited under Mesopic Rather Than Photopic Conditions
Authors: Denion, Eric
Lux, Anne-Laure
Mouriaux, Frederic
Béraud, Guillaume
Issue Date: 2016
Citation: PLOS ONE, 11 (3)
Abstract: Introduction We aimed to determine the limbal lighting illuminance thresholds (LLITs) required to trigger perception of sclerotic scatter at the opposite non-illuminated limbus (i.e. perception of a light limbal scleral arc) under different levels of ambient lighting illuminance (ALI). Material and Methods Twenty healthy volunteers were enrolled. The iris shade (light or dark) was graded by retrieving the median value of the pixels of a pre-determined zone of a gray-level iris photograph. Mean keratometry and central corneal pachymetry were recorded. Each subject was asked to lie down, and the ALI at eye level was set to mesopic values (10, 20, 40 lux), then photopic values (60, 80, 100, 150, 200 lux). For each ALI level, a light beam of gradually increasing illuminance was applied to the right temporal limbus until the LLIT was reached, i.e. the level required to produce the faint light arc that is characteristic of sclerotic scatter at the nasal limbus. Results After log-log transformation, a linear relationship between the logarithm of ALI and the logarithm of the LLIT was found (p<0.001), a 10% increase in ALI being associated with an average increase in the LLIT of 28.9%. Higher keratometry values were associated with higher LLIT values (p = 0.008) under low ALI levels, but the coefficient of the interaction was very small, representing a very limited effect. Iris shade and central corneal thickness values were not significantly associated with the LLIT. We also developed a censored linear model for ALI values <= 40 lux, showing a linear relationship between ALI and the LLIT, in which the LLIT value was 34.4 times greater than the ALI value. Conclusion Sclerotic scatter is more easily elicited under mesopic conditions than under photopic conditions and requires the LLIT value to be much higher than the ALI value, i.e. it requires extreme contrast.
Notes: [Denion, Eric; Lux, Anne-Laure] CHU Caen, Dept Ophthalmol, F-14000 Caen 9, France. [Denion, Eric] INSERM, COMETE U1075, Caen 9, France. [Denion, Eric; Lux, Anne-Laure] Unicaen, Sch Med, Pole Format & Rech Sante, Caen, France. [Mouriaux, Frederic] CHU Rennes, Serv Ophtalmol, Rennes, France. [Mouriaux, Frederic] Univ Rennes 1, Fac Med, Rennes, France. [Beraud, Guillaume] CHU Poitiers, Med Interne & Malad Infect, Poitiers, France. [Beraud, Guillaume] Univ Droit & Sante Lille 2, EA2694, Lille, France. [Beraud, Guillaume] Hasselt Univ, Interuniv Inst Biostat & Stat Bioinformat, Hasselt, Belgium.
URI: http://hdl.handle.net/1942/21818
DOI: 10.1371/journal.pone.0150314
ISI #: 000371993000030
ISSN: 1932-6203
Category: A1
Type: Journal Contribution
Validation: ecoom, 2017
Appears in Collections: Research publications

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