Time of Day Impacts Anterior Sclera, Conjuctiva Thickness Variations

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Amplitude of diurnal thickness change larger in the conjunctiva than in the sclera
Amplitude of diurnal thickness change larger in the conjunctiva than in the sclera

HealthDay News — Diurnal variations occur in the thickness of the anterior sclera and conjunctiva among healthy young adults, according to a study published online March 1 in Ophthalmic & Physiological Optics.

Scott A. Read, PhD, from the Queensland University of Technology in Brisbane, Australia, and colleagues collected measures of anterior scleral and conjunctival thickness for 19 healthy young adults with minimal refractive error using anterior segment optical coherence tomography at seven measurement sessions over a 24-hour period. For each subject at each measurement session the thickness of the temporal anterior sclera and conjunctiva were determined at six locations at varying distances from the scleral spur.

The researchers observed significant diurnal variations in thickness in both the anterior sclera and conjunctiva over a 24-hour period (both P < 0.01). A similar pattern of diurnal change was exhibited by the sclera and conjunctiva; close to midday there was small magnitude thinning, while in the early morning immediately after waking there was a larger magnitude thickening. The amplitude of diurnal thickness change was larger in the conjunctiva than the sclera (mean amplitude 69 ± 29 versus 21 ± 8 µm). At the scleral spur, the conjunctiva exhibited its smallest magnitude of change, while the sclera exhibited its largest magnitude of change.

"Studies requiring precise measures of these anatomical layers should therefore take time of day into consideration," the authors write.

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