A Critical On Glaucoma and the Optic Nerve
The word “glaucoma” comes from the Greek Word meaning opacity of the crystalline lens. It is the major disease of nerve vision called the optic nerve. The optic never receives light generated nerve impulses from the retina and transmits these to the brain where those electrical signals will be recognized as vision. Glaucoma is characterized by a particular pattern of progressive damage to the optic nerve that generally begins with subtle loss of vision, if glaucoma is not diagnosed and treated on time, it can progress to loss of central vision and blindness.
It is normally associated with increased fluid pressure in the eye (Merck, 2011). The term “ocular hypertension” is used for people with consistency raised intraocular pressure without any associated optic nerve damage (Sommer et al, 1991).
Glaucoma occur world wide leading to the cause of irreversible blindness, and it is called the silent thief of sight because the loss of vision often occurs gradually over a long period of time and symptoms only occur when the disease is quite advanced.
Once the vision is lost, it cannot normally be recovered, so treatment is aimed at preventing further loss. Glaucoma is the second cause of blindness after cataracts (Global vision on visual impairment, 2002). About 6 million individuals are blind in both eyes from this disease. In the united state, over 3 million people have glaucoma, as many half of the individuals with glaucoma may not know that they have the disease. The reason they don’t know is that glaucoma does not cause signs and symptoms at the initial time. (leske et al, 2007).
The nerve damage involves loss of retinal ganglion cells in a characterized pattern. (Hernandez et al, 2008). Many different subtypes of glaucoma can be considered to be a type of optic neuropathy. Raised intraocular pressure is the most important and only modified risk factor for glaucoma (Li et al, 2011). Some may have high eye pressure for years and never develop damage while others can develop nerve damage at a low pressure.
Glaucoma has been classified into major two types which are chronic or primary open-angle glaucoma and acute angle-closure glaucoma. (Paton and Craig, 1976). These angle refers to the area between the iris and cornea through which fluid flow to escape through trabecular meshwork primary open-angle glaucoma is a chronic disease that progress at a slower rate and the patients may not know that they have lost vision until the disease has progressed significantly (Wang et al, 2002). Other variations include normal tension glaucoma, pigmentary glaucoma, secondary glaucoma and congenital glaucoma.
They are many causes of glaucoma, which includes dietary, ethnicity, gender, genetics. In dietary causes caffeine increases intraocular pressure in those with glaucoma, but does not appear to affect normal individuals (Li et al., 2011). In ethnicity, east asian are prone to develop angle closure glaucoma due to their shallow anterior chamber depths (Wang et al., 2002). Women are three times at risk than men to develop acute angle closure glaucoma due to their shallow anterior chambers. While those of african descent are three times more likely to develop primary open angle glaucoma. Sometimes, it occur as a result of genetics, various congenital/genetic eye malformations are associated with glaucoma, primary open angle glaucoma is associated with mutations in genes at several loci (Chang. et al., 2001).
Other factors that can cause glaucoma known as secondary glaucoma’s which occur as a result of prolonged use of steroids (Steroid induced glaucoma), they are some conditions that severely restrict blood to the eye such as diabetic retinopathy and central retinal vein occlusion (neovascular glaucoma), ocular trauma and uveitis (Langman. et al., 2005). These diseases leads to some signs and symptoms like eye pain, headaches, halos around lights, dialated pupils, red eyes, nausea, vomiting and vision loss (Kwom et al., 2009). If these signs and symptoms is not treated on time it will lead to complications like, uveitis, subluxation of lens, traumatic glaucoma, Hemolytic glaucoma, toxic, central retinal vein occlusion, ischemia of the retina and neovascular glaucoma. (Hasnain and Syed, 2006).
Glaucoma can be diagnosed by standard eye examination performed by optometrists, orthoptists and ophthalmologists. Testing for glaucoma include measurements of the intraocular pressure through tonometry, changes in size or shape of the eye, anterior chamber angle examination or goniosocopy and examination of optic nerve to look for any visible damage to it or change in the cup-to-disc ratio, rim appearance and vascular change (Thomas and Parikh, 2006). Examination of glaucoma could also be assessed with more attention given to sex, race, and history of drug use, refraction, inheritance and family history (Pardianto et al., 2006).
The management of glaucoma are to avoid glaucomatous damages and nerve damage, and preserve visual field and total quality of life for patients with minimal side effects (Noecker, 2006). This requires appropriate diagnostic techniques and follow-up examinations and judicious selection of treatments for the individual patients. Although intraocular pressure is the only major risk factors for glaucoma, lowering it through various pharmaceuticals or surgical techniques is currently the mainstay of glaucoma treatment.