Treatment is initiated in eyes that have developed glaucomatous optic nerve damage and/or visual field loss, or in eyes at significant risk for developing glaucoma. ![]() Īs the risk factors for glaucoma continued to be explored further, IOP remains at present the only significantly modifiable risk factor in the treatment of glaucoma. Decreasing the IOP reduced the risk of progression to glaucoma - however, the majority of ocular hypertensive patients did not develop damage within 5 years. After 5 years of follow up, 9.5% of the observation group developed glaucoma while 4.4% of the medication group developed glaucoma, defined as optic disc or visual field deterioration. All subjects were followed closely with visual field exams and optic nerve photos. Half of the participants were randomized to treatment to lower their IOP by 20%, and half were randomized to observation. The Ocular Hypertension Treatment Study also investigated ocular hypertensive patients and addressed whether treatment of elevated IOP prevented or delayed the onset of glaucomatous damage. He found that the majority of patients in his study did not develop visual field loss over a 7-year period. These patients were followed carefully, without treatment. In the 1960’s, Armaly organized a collaborative investigation of “ocular hypertensives” with intraocular pressure greater than 21 mmHg, but without optic nerve damage or visual loss. This observation led to the belief that IOP measurement above 21 mm Hg is abnormal, and that the goal of glaucoma treatment was to lower the IOP to below 21 mmHg. Īs instruments were being developed for more objective measurement of IOP, population surveys at that time found that only approximately 2 percent of the population had IOP levels above 21 mm Hg. Therefore, IOP remained the primary focus in the diagnosis and treatment of glaucoma for many years. ![]() Bowman and others noticed that there was a definite relationship between the level of IOP and the likelihood that the eye would lose sight the higher the IOP, the greater the chance that the eye would become blind. In the 19th century, William Bowman ( English ophthalmologist) developed a method of estimating the tension, or hardness, of the eye by palpating it with his fingers through the closed eyelid. In the 17th century, Richard Bannister (English physician) noticed the hardness of eyes in cases where cataract operations did not improve vision. Īn association between increased IOP and the loss of sight in glaucoma has been noted for many centuries. Po is the IOP in millimeters of mercury (mmHg), F is the rate of aqueous formation, C is the facility of outflow, and Pv is the episcleral venous pressure. The intraocular pressure (IOP) of the eye is determined by the balance between the amount of aqueous humor that the eye makes and the ease with which it leaves the eye. 2.1.1 Goldmann and Perkins applanation tonometry.
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