Glaucoma is an eye condition that damages optic nerve due to increased intraocular pressure. This damage to optic nerve leads to progressive loss of vision and if it is left untreated then it will lead to permanent blindness. Glaucoma is the second leading cause of blindness around the world after cataract.
Advanced glaucoma is defined as so much loss of vision as to show significant symptoms with enough impairment/deterioration of eye function. The optic nerve is responsible for carrying all the visual functions from the retina to the brain and plays an important role in visual perception. In advanced glaucoma, the patient loses about 80 to 90% of one’s optic nerve fibers and the cup-to-disc ratio is around 0.8 or 0.9, thus visual perception in advanced glaucoma patient is severely impaired. Generally, the optic nerve is susceptible to high intraocular pressure, but in advanced glaucoma patients, the optic nerve also becomes more prone to damage/injury at normal/lower eye pressures too.
Patients progress to advanced glaucoma stage because they do not visit an ophthalmologist for regular eye checkup or they neglect significant eye symptoms for a long time. Some patients do progress to advanced glaucoma stage despite being under the care of a doctor, but this is usually rare in patients diagnosed early in the disease state.
What are the Symptoms of Advanced Glaucoma?
The symptoms of advanced glaucoma often vary from person to person. The patient might perceive difficulty with different visual functions such as reading, outdoor activities, driving, seeing at nighttime and usually his/her eyes tire easily with different visual functions. Patients have difficulty seeing in low light environments as well as have difficulty seeing in bright light environment too and experience glare and photosensitivity/photophobia/light sensitivity. Amber/yellow glasses seem to help with glare and contrast in the vision; also dark tinted glasses help with light sensitivity.
In advanced glaucoma patients, all visual functions such as color, acuity, and contrast sensitivity are affected due to 80-90 % damage to the optic nerve, which plays a significant role in vision. The usual pattern of vision loss is from superiorly as well as inferiorly and from periphery to center and as it progresses visual acuity (sharpness of vision) is lost and vision becomes narrow or patient experiences tunnel vision. Patients also experience severe defect in visual field that encroaches center of fixation leading to split fixation visual field loss. These patients have very poor prognosis, though visual field tests vary from person to person. Studies also show that glaucoma generally affects yellow-blue perception than red-green perception of light, but the overall vision is affected due to optic nerve damage. Generally, patients with glaucoma have symmetric visual field defects in both the eyes, but one eye defect can be worse than the other eye.
The patient might present with hazy or blurred vision, halos around bright lights, severe eye and head pain, nausea, vomiting, sudden vision loss, easy tiring of eyes. The symptoms differ from patient to patient and in the same patient from day to day, as patient’s report that they have some bad days accompanied with good days with their vision.
Treatment of Advanced Glaucoma
The patients who are at a risk of vision loss and those that are not managed with medications such as eye drops or even laser may benefit from surgery. The decision on surgical intervention depends on the extent of optic nerve damage, target intraocular pressure, elevated intraocular pressure despite conservative management. Laser can be used in which a focused light beam is used to release intraocular pressure by treating trabecular meshwork. Various laser surgeries used to treat glaucoma are selective laser trabeculoplasty (SLT), argon laser trabeculoplasty (ALT), laser peripheral iridotomy (LPI) and laser cyclophotocoagulation. If laser is not effective then incisional surgery (filtering surgery) can be opted in which an artificial drainage hole is created in sclera with procedures such as trabeculectomy or sclerostomy to release intraocular pressure. In addition, ExPRESS shunt and glaucoma drainage implants such as Ahmed and Baerveldt implants can be used to drain the fluid and release IOP.
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