GLAUCOMA

INTRODUCTION

• Glaucoma is a group of ocular conditions characterised by optic nerve damage. This occurs when intraocular pressure rises due to impaired drainage of aqueous fluid through the scleral venous sinus in the angle between then iris and cornea in the anterior chamber. The most common type is open-angle glaucoma with less common types including closed-angle and normal tension glaucoma.
• About 11 to 67 million people have glaucoma globally. The disease occurs more among older people. Closed angle glaucoma is more common in women .
• Globally glaucoma is the second leading cause of blindness after cataract.
• The word ‘glaucoma’ is from a Greek word glaukos which means blue, green or grey.

RISK FACTORS

• Family history diabetes mellitus
• Thin cornea high blood pressure
• Eye trauma African-American race
• Short sightedness cardiovascular disease
• Migraines Obesity
• Prolonged use of corticosteroids

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PATHOPHYSIOLOGY

• The underlying cause of glaucoma is still unclear however , the major risk factor for most glaucoma’s and the focus of treatment is increased intraocular pressure.
• Intraocular pressure is a function of production of liquid aqueous humour by the ciliary process of the eye and its drainage through the trabecular meshwork. Aqueous humour flows from the ciliary processes into the posterior chamber and anteriorly by the iris. It then flows through the pupil of the iris into the anterior chamber , bounded posteriorly by the iris and anteriorly by the cornea. From here, the trabecular meshwork drains aqueous humour through the scleral venous sinus into the scleral plexus and then general blood circulation.

PATHOPHYSIOLOGY CONT’D

• In open or wide-angle glaucoma, flow is reduced through the trabecular meshwork due to degeneration and obstruction of the trabecular meshwork whose original function is to absorb the aqueous humour. Loss of aqueous humour absorption leads to increased resistance and thus a chronic, painless builds up of pressure in the eye .
• In closed-angle glaucoma, the irodocorneal angle is completely closed because of forward displacement of the final roll and root of the iris against the cornea, resulting in the inability of the aqueous fluid to flow from the posterior to the anterior chamber and then out of the trabecular network. This accumulation of aqueous humour causes an acute increase in pressure and pain.

STAGES OF GLAUCOMA

• Initiating event: this include factors that narrow the angle of the eye like emotional stress, long term use of corticosteroids.
• Structural alteration: the initiating events leads to structural alteration which impedes the flow of aqueous membranes.
• Functional alteration: tissue an cellular changes occur leading to increased intra-ocular pressure which creates a functional change.
• Optic nerve damage:
• Visual damage

DIAGNOSTIC INVESTIGATION

• Tonometry(measurement of intraocular pressure): the eye is dumbed by applying a few eye drops. The examiner then uses a tonometre to measure the inner pressure of the eye through pressure applied by warm air.
• Ophthalmoscopy(dilated eye examination): the test examine the shape and colour of the eye. The pupil is dilated through the application of eye drops. With the aid of a magnification device with a light on the end, the examiner can examine the magnified optic nerve.
• Perimetry(visual field test): it examines complete field of vision. The patient looks straight ahead and is asked to indicate when light passes the patients peripheral field of vision.

DIAGNOSTIC INVESTIGATIONS CONT’D

• Gonioscopy: measures angle in the eye where the iris meets the cornea. Eye drops are used to numb the eye. A contact lens with mirror is placed gently on the eye to allow the examiner to see the angle between the cornea and iris.
• Pachymetry : measures thickness of the cornea. The examiner places a pachymeter gently on the front of the eye to measure its thickness.
• Nerve fibre analysis: measures thickness of the nerve fibre layer. The nerve fibres are examined using one of several techniques.

TYPES OF GLAUCOMA

• Primary division in categorizing glaucoma is ;
• Open-angle (chronic glaucoma): refers to slow clogging of the drainage canals resulting in increased eye pressure which causes progressive optic nerve damage.
• Closed-angle(narrow-angle): the iris bows forward narrowing the angle that drains the eye, increasing pressure within the eye.
• Secondary glaucoma: the most common cause is inflammation of the iris, ciliary body and choroid(anterior uveitis)

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TYPES OF GLAUCOMA

SIGNS AND SYMPTOMS

• Blurred vision
• Difficulty focusing
• Headache
• Discomfort in and around the eye
• Difficulty adjusting to low light
• Halo around the light
• Loss of peripheral vision
• High intraocular pressure

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MEDICAL MANAGEMENT

• The goal of glaucoma treatment is to lower pressure in the eye and prevent optic nerve damage.
• Systemic and topical preparations are given normally starting on a low dosage until normal intraocular pressure is reached.
• Beta blockers, example Betimol is given
• Alpha-adrenergic agonists. E.g. lopidine
• Some times the eye drops alone cant bring down the pressure therefore an oral carbonic anhydrase inhibiter is given.

SURGICAL MANAGEMENT & THERAPIES

• Laser trabeculoplasty(laser beams are applied to the inner surface of the trabecular meshwork to open the intrabecular nerve space and widen the canal)
• Laser iridotomy: laser energy is used to make a small, full thickness opening in the iris to equalise the pressure between the front and back of the iris, thus correcting any abnormal bulging of the iris.

NURSING MANAGEMENT

• Reassure patient
• Monitor patients intra-ocular pressures.
• Position the patient on his back or unaffected side, and following general safety measures.
• Teach patient signs and symptoms that require immediate medical attention, such a vision change or eye pain.
• Monitor patients ability to see clearly. Question the patient regularly about the occurrence of visual changes.
• Encourage patient to express his/her concerns related to having a chronic condition

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NURSING MANAGEMENT CONT’D

• Encourage ambulation immediately after surgery.
• Stress the importance of meticulous compliance with prescribed drug therapy. After surgery, protect the affected eye by applying an eye patch and eye shield.
• Apply topical corticosteroids as ordered to rest the pupil
• After trabeculectomy, give medications as ordered to dilate pupila
• Administer pain medications as ordered.
• Instruct the patients family how to modify the patients environment for safety.

COMPLICATIONS

• Hypotony: IOP of 5mmHg or less
• Visual loss
• Postoperative complications of filtration procedures include cataract formation

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REFERENCE

• ROSS AND WILSON

ANATOMY AND PHYSIOLOGY IN HEALTH AND ILLNESS 11^TH EDITION

BRUNNER AND SUDDARTH'S TEXTBOOK FOR MEDICAL AND SURGICAL NURSING

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www.healthline.com

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www.wikipedia.com

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