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Quianta Moore, Stephen C Pflugfelder, ; Blink-Related Changes in Light Scattering in Meibomian Gland Dysfunction. Invest. Ophthalmol. Vis. Sci. 2014;55(13):25.
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Tear dysfunction is a reported cause of blurred and fluctuating vision. This study evaluated the hypothesis that light scattering, measured with the Optical Quality Analysis System (OQAS), differs between aqueous tear deficiency (ATD) and meibomian gland dysfunction (MGD).
In this retrospective, comparative case study all patients presenting with eye irritation, a tear break-up time (TBUT) < 7 and who had a measured ocular scattering index (OSI) using the OQAS were included in the analysis. Patients were stratified into ATD (n=18) or MGD (n=18) based on tear meniscus height (TMH) and clinical signs. The mean OSI between ATD and MGD, and the difference in OSI before and after blinking was compared between groups.
The majority of patients with ATD (88%) had a mean OSI slightly above normal (normal < 1.0; 1.5 > ATD >1). The majority of patients with MGD (83%) had an abnormally elevated OSI > 1.5. A significantly greater number of patients with MGD had an OSI >1.5 compared to the ATD group (p< 0.0001). Additionally, the majority of the MGD group (66%) had a greater than 1 difference in pre- and post- blink OSI, whereas 100% of the ATD had a difference in OSI of < 1 (p< 0.0001 MGD vs ATD).
Patients with MGD had higher mean light scattering indices than those with ATD. Also, light scattering decreased momentarily after blinking in the MGD group, but remained either unchanged or minimally changed after blinking in the ATD group. Despite having similar tear break-up times, the ATD group had less light scattering overall. Thus, light scattering appears to be a feature of lipid tear dysfunction.
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