Updates in Diagnosis and Treatment of Low Tension Glaucoma

Abstract

Low tension glaucoma (LTG) is chronic optic neuropathy characterized by progressive damage or degeneration to the optic nerve and visual field loss with an intraocular pressure less than 22 mm Hg. It is reported that nearly one-third of glaucoma patients can be classified as having this type. LTG is caused by progressive death of RGCs; the pathophysiological process is unclear and is, at best, speculative. Many hypotheses developed to understand this process. One hypothesis is the compromised blood supply to the optic nerve due to mechanical compression exerted by IOP (even within normal range). Other hypothesis includes oxidative stress, both at the level of trabecular meshwork and retinal ganglion cells. The glial cells in the optic nerve head (lamina cribrosa cells), and in particular the astrocytes, have been proposed to play an important role in the glaucomatous change in extracellular matrix around the ganglion cells. Risk factors that facilitate LTG development are increased trans-cribrosal and CSF pressure, IOP fluctuation, genetic mutations as mutations in OPA1 and OPTN genes. LTG should be differentiated from physiologic large cup, other types of glaucoma and other optic nerve disorders. Diagnosis could be initiated by detailed history taking, full examination with tonometry, gonioscopy and optic disc view through fundus examination. Investigations run in two aspects, first is assessing optic nerve structure using optic nerve imaging (as confocal scanning laser ophthalmoscopy, OCT, OCT angiography, Scanning laser polarimery, Ocular Response Analyzer ), and second is assessing its function using perimetry (as Standard automated, Short-wavelength, Frequency-doubling). The modern goals of management are to avoid glaucomatous damage and nerve damage, and preserve visual field and total quality of life for patients, with minimal side effects. Although intraocular pressure is only one of the major risk factors for glaucoma, lowering it via various pharmaceuticals and/or surgical techniques (laser could be also used to help drainage) is currently the mainstay of glaucoma treatment. Additionally, it is important