Diurnal Variation of Central Corneal Thickness and Intra-Ocular Pressure n Normal and Suspect Glaucomatous Eyes
Stuart Keel, BOrth&OphthSc(Hons) 1
Linda Malesic, PhD 1,2
1 Department of Clinical Vision Sciences, La Trobe University, Melbourne, Australia
2 Department & Clinical School of Orthoptics, Royal Victorian Eye and Ear Hospital, Melbourne, Australia
Normal physiological variations in central corneal thickness (CCT) are important as they provide a reference parameter for experimental and clinical research particularly in the field of glaucoma prediction and assessment. The literature has established that significant diurnal fluctuations in CCT occur in persons with no ocular pathology when CCT has been assessed over a 12-48 hour period. The consensus in the literature is that CCT is thickest in the morning upon awakening and gradually thins as the day progresses, with the greatest proportion of this variation occurring in the first three hours after awakening. Studies that have attempted to establish whether a diurnal variation in CCT exists in glaucomatous eyes have not been successful. To date, significant developments, although variable, have been made to better understand diurnal variation in CCT in individuals with no ocular pathology. This signifies the importance of monitoring CCT throughout the day in those individuals who may be at risk of developing glaucoma, as opposed to those individuals who already suffer from glaucoma, as it will ensure that the timing of glaucoma treatment will not be overlooked. This review discusses the current opinion on diurnal CCT in those individuals who have no ocular pathology and in those who are glaucoma suspects. It will also focus on the significance of diurnal variability with CCT and its relationship to intra-ocular pressure (IOP) diurnal variation.
