Glaucoma

Glaucoma is a group of disorders characterized by increased intraocular pressure leading to atrophy and damage of optic nerve and retinal ganglion cells with a subsequent gradual loss of visual fields. Glaucoma is the most common cause of irreversible blindness and it is the second leading cause of blindness worldwide, affecting 2% of those over 40 years of age and 4% of those over 70 years. The main risk factor and characteristic is raised intraocular pressure. Once the vision loss from glaucoma has occurred, it is permanent.

Glaucomas is an umbrella term for a diverse group of over 60 eye conditions associated with damage of the optic nerve that leads to a loss of vision. They can be classified into different diagnostic groups:
Primary or secondary: the absence (primary) or presence of causative factors such as uveitis, trauma, drugs (eg corticosteroids), diabetes, venous occlusion (secondary)
Open-angle or angle-closure: depending on the anatomy of the drainage angle
Speed of onset: acute or chronic
Age of onset: juvenile, adult or congenital

Primary open-angle glaucoma (POAG)
This is the commonest glaucoma type that occurs in Caucasians and African Americans. It is ‘open-angle’ as the drainage angle for fluid within the eye remains open. The exact pathophysiological mechanism is not clear but elevated intraocular pressure, an alteration of the blood supply to the optic nerve and genetics are factors. Typically in this type of glaucoma, the progression from having normal vision to complete blindness can take about 25 years to 70 years if there is no treatment, sometimes leading it to be called the “silent thief of sight” as the vision loss occurs slowly over a longer period of time

Clinical Features:
The glaucoma is asymptomatic until it is somewhat advanced with visual field loss. The central vision is preserved until later stages and a considerable amount of peripheral vision may be lost before there is an awareness of a problem. Characteristic changes to the optic disc such as thinning of the optic disc neurosensory rim indicating loss of nerve fibres occur. There is no pain. The changes are typically asymmetrical. Diagnosis is usually made by looking for cupping of the optic nerve.

Glaucoma screening by opticians can helps detect primary open-angle glaucoma. Probably as many as 50% of those with glaucoma do not know they have it.

Treatment:
The aim is to reduce the intraocular pressure to below a level at which further damage to the nerve is less likely. If treated early, it is possible to slow or stop the progression of the disease. This can be done by:

  • medically with topical drops (beta-adrenergic blockers, prostaglandin analogs, hyperosmotic agents, carbonic anhydrase inhibitors)
  • laser treatments (Argon laser trabeculoplasty, Nd:YAG laser peripheral iridotomy, diode laser cycloablation)
  • surgically (canaloplasty or trabeculectomy)

Also important is counseling and information on the natural history of the condition and the impact it will have on activities like driving. Also, reviewing the important side effects of the drops and the importance of compliance. The probability is that the treatment is for their lifetime and they may not notice any day-to-day benefit from the drops.

Acute angle-closure glaucoma (AACG):
A closed-angle glaucoma can present gradually or acutely, generally in older people. The sudden presentation may involve severe eye pain, headache, blurred vision, decreased vision, redness of the eye, mid-dilated fixed pupil, seeing halos around lights, and nausea. The treatment of closed-angle glaucoma is a medical or ophthalmic emergency.

Podiatry Implications of Glaucoma:

  • Podiatrists treat patients with foot problems who have visual impairments from glaucoma, so need an understanding of what their patients are going through to be empathetic and understanding.
  • Visual impairment can affect the ability to self-care for foot problems that will generally need an alteration in treatment plans.
  • Ensure that any issues with their patient’s vision are followed up by the primary care provider.
  • Poor compliance with medication use has been reported in those with glaucoma, so all health professionals can play a role in reinforcing the need for it.

Gait and Glaucoma:
Lee et al (2021) using an F-scan in-shoe pressure measuring system reported that those who glaucoma when walking over a course with obstacles reported slower gait speed and cadence and longer gait cycle and stance time when compared to controls.

Related Topics:
Working with the visually impaired

Page last updated: Aug 17, 2021 @ 3:07 am

 
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