Glaucoma, changes in the intraocular pressure, is an irreversible, chronic and progressive disease that causes visual field loss and destruction of retinal ganglion cells. It is the leading cause of irreversible blindness worldwide (1) and among eye diseases, glaucoma is the second leading cause for blindness after cataracts (2). It is characterized by both functional and structural changes. Where visual field tests are used for the diagnosis, follow-up, and treatment of the functional deterioration; optical coherence tomography can indicate changes in retinal ganglion cells and optic nerve heads qualitatively and/or quantitatively.
One of the major risk factors for glaucoma is high intraocular pressure. Although, as a biological phenomenon, intraocular pressure is not fixed and varies considerably during the day. The effect of this 24-hour alteration cycle on the natural course of glaucoma is not yet fully understood (3). In literature, it is indicated that intraocular pressure is measured the highest in the early morning and out-of-office hours (4). Therefore, one measurement during office hours might be insufficient to determine the real value of intraocular pressure. Increases in nocturnal eye pressure have not yet been adequately studied. Due to these reasons, ideal measurement techniques appear to be 24-h IOP cycle measurements or diurnal follow-ups. In this way, positive results can be achieved in cases with acceptable IOP during clinic hours but show functional or anatomical deterioration.
Studies to perform measurements that are non-invasive, continuous and compatible with Goldman tonography are still in progress (5). In this direction, special contact lenses have been produced to measure intraocular pressure for 24 hours (6). The data provided from contact lenses enables specialists to make more accurate decisions. Normotensive glaucoma is one of the most beneficial diseases through the differentiation of patients from normal individuals.
1. The Effect of Statins on Intraocular Pressure and on the Incidence and Progression of Glaucoma: A Systematic Review and Meta-Analysis. McCann P, Hogg RE, Fallis R, Azuara-Blanco A. Invest Ophthalmol Vis Sci. 2016 May 1; 57(6):2729-48.
2. Glaucoma is second leading cause of blindness globally. Kingman S. Bull World Health Organ. 2004 Nov; 82(11):887-8.
3. Diurnal and 24-h Intraocular Pressures in Glaucoma: Monitoring Strategies and Impact on Prognosis and Treatment. Konstas AG et al. Adv Ther. 2018 Nov;35(11):1775-1804
4. Untreated 24-h intraocular pressures measured with Goldmann applanation tonometry vs nighttime supine pressures with Perkins applanation tonometry. Quaranta L et al. Eye (Lond). 2010 Jul; 24(7):1252-8.
5. Diurnal Intraocular Pressure Fluctuation in Eyes with Angle-closure. Bhartiya S et al. J Curr Glaucoma Pract. 2015 Jan-Apr;9(1):20-3.
6. Twenty-four hour intraocular pressure monitoring with the SENSIMED Triggerfish contact lens: effect of body posture during sleep. Beltran-Agulló L et al. Br J Ophthalmol. 2017 Oct;101(10):1323-1328.