Glaucoma and blindness
Home  |  Contact us  
eye care advice logo eye care advice logo
 
  Eye Biology  
 
 
 
 
  Eye Problems  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  Eye Care Procedures  
 
 
 
 
 
 
 
 
 
 
 
 

A leading cause of irreversible blindness throughout the world is believed to be Glaucoma. The studies suggest that health services in the developing countries have identified half of the people suffering from this dreadful disease, however in the developing countries the level of awareness is far below.

Definition

Glaucoma is essentially a type of optic neuropathy associated with damage of optic disc arising from increased intraocular pressure resulting in loss of vision. The diagnosis of which depends largely on clinical examination.

Earlier, glaucoma was thought to be a single disease entity resulting in optic nerve damage and visual loss secondary to high intraocular pressure. However, it is now known that there are various ocular disorders and processes, which leads to specific forms of optic disc damage and visual field loss.

Diagnosis

The differentiation of particular case of glaucoma is normally done through clinical examination. Such a clinical testing is conducted as ocular examination of any new patient. It is important to have a slit-lamp evaluation of the anterior segment structures as well as detailed study of the history, and special attention should be given to the key aspects as below:

  • Tonometry in order to record the accurate intraocular pressures
  • Gonioscopy to verify angle pathology if any
  • Nerve fiber layer analysis
  • Visual field examination
  • Optic disc examination

Tonometry

Assessment of intraocular pressure (IOP) is a vital part of glaucoma- instrumental (Schiøtz) tonometry helps in measuring it. Tonometry uses an instrument known as tonometer, which is based on certain physical principles for measuring pressure within a globe. The force required to strain a globe is directly proportional to the pressure within that globe.

There are three kinds of tonometer – indentation, or high-displacement, applanation, or low-displacement and noncontact.

The indentation tonometers use a plunger to indent the cornea by a varying amount. At the time of corneal deformation, a significant volume of intraocular fluid is displaced due to indentation, which results in almost doubling of the IOP. Further, the conversion tables help to estimate the original IOP from the indentation tonometric value obtained.

The applanation tonometers raise IOP only slightly, as the eye is subjected to sufficient force that flattens the cornea. The magnitude of force required to achieve flattening of cornea to a constant degree is converted into IOP values.

The Noncontact tonometers use a puff of air to flatten the cornea. The IOP is calculated based on the time required to flatten the cornea.

Gonioscopy

Gonioscopy is performed on the suspects of glaucoma after the anterior segment examination and IOP measurement gets over. Normally this technique is employed by practitioners in order to view the anterior chamber angle. The diagnosis provides vital information, which helps in determining the type of glaucoma, the suspect may be suffering from. Moreover, accurate diagnosis is very important as this determines the appropriate therapy, which should be instituted. Inaccurate diagnoses of glaucoma by clinicians who fail to examine the angle correctly, leads to improper therapy.

Diagnosis of optic nerve and visual field

Some important indications of prospective risk for glaucomatous damage are the extent of damage that already exists and the ongoing rate of progression of the disease. The magnitude of damage is estimated by evaluating the status of the optic nerve and visual field. The signs of glaucomatous damage such as notching of the rim, asymmetry between the appearance of the optic nerves, thinning of the neuroretinal rim (especially at the inferior and superior poles), peripapillary atrophy, or splinter hemorrhages, are detected through stereoscopic evaluation.

Observance of the progressive change of the optic disc or visual field is vital for diagnosis of glaucoma. However, this is impossible with few initial detections of the patient eye. It is only through serial examinations over time that the rate of progression can be measured.

Nerve fiber layer analysis

The evaluation of the nerve fiber layer is conducted through red-free illumination or special photographic techniques, which assists in detection of widespread loss or focal, wedge-shaped defects. The eyes affected by glaucoma feature distinctive nerve fiber pattern defects with or without generalized depression.

Major risk factors for Glaucoma

Demographic

Age - The studies on prevalence and incidence indicates that risk of Glaucoma increase with age.
Gender - Thought there are no such evidence that either men or women have higher chances of Glaucoma, some researches anticipate men suffer greater age-adjusted risk as compared with women.
Race - The large-scale population studies have confirmed that people of African, African-American, and African-Caribbean origin are highly vulnerable to primary open-angle glaucoma (POAG)

Ocular

Intraocular pressure (IOP) – There exist solid evidence that IOP is closely associated with glaucoma An individual affected by glaucoma, having higher IOP in the eye tend to lose field more quickly. More than an essential part of diagnosis, IOP is considered as a major risk factor for glaucoma
Optic nerve head – They are an important marker for the existence and progress of glaucoma, the structure of the optic nerve head might aid the pathogenesis of glaucoma.
Myopia – It is said to be associated with an increased risk of POAG.
Hypermetropia - High degrees of hypermetropia is one of the major causes of angle-closure glaucoma

Systemic risk factors

Diabetes – The risk POAG associated with it is typically based on hospital studies and often overestimated.
Systemic hypertension - Most of the studies reveal that there is a direct relationship between rise in blood pressure and rise in IOP; however, its association with POAG is not profound.

Genetic factors

The studies indicate a positive family history of glaucoma is known to increases the risk of glaucoma

Other factors

Factors like cigarette smoking, alcohol intake, and unsuitable socioeconomic factors can aggravate chances of Glaucoma.

Conclusion

Glaucomas have become threat to the public health systems in most countries. Considering at individual level, they represent a particularly severe form of blindness, which is irreversible. This makes appropriate diagnosis of the disease very essential to ensure the vision does not fade out in the early years of a glaucoma patient.

 
Disclaimer  |  Copyright  |  Privacy
Copyright © Reserved by Eye Care Advice . com