Rapid Ophthalmology

Zahir Mirza

• Verlag: Wiley-Blackwell
• Jahr: 2013
• ISBN:
  9781118678824
• Auflage: 1
• Thema: Medicine
• Thema: Opthalmology & Optometry

A brand new title in the Rapid series, providing a concise, structured approach for students preparing for ophthalmology examinations

Presents a thorough foundation of ophthalmology knowledge, emphasising clinically relevant information, in the familiar 'Rapid' series format where diseases are presented in alphabetical order so aiding quick look-up of conditions

Ideal for use in busy clinical settings, such as clinics and hospital wards, while on rotation

Includes a companion website at www.wileyrapids.com/ophthalmology containing a range of clinical images in PowerPoint format This title is also available as a mobile App from MedHand Mobile Libraries. Buy it now from iTunes, Google Play or the MedHand Store.

Diseases

Age-related macular degeneration (AMD), dry

DEFINITION

Blinding degeneration of the macula characterized by drusen and changes to the retinal pigment epithelium (RPE).

AETIOLOGY

Unknown, likely multifactorial. See Associations/risk factors.

ASSOCIATIONS/RISK FACTORS

Increased age, female gender (most likely due to increased ages of survival), smoking, hypermetropia, hypertension, race (greater in Caucasians than Blacks), excessive alcohol intake. Cumulative UV light exposure. Increased dietary fat intake. There is some evidence for an inherited predisposition. Variants in the complement factor H gene, located on chromosome 1, are associated with the development of AMD.

EPIDEMIOLOGY

AMD is the leading cause of blindness in the Western world amongst 50+ year-olds. Dry AMD accounts for 90% of cases of macular degeneration but can be less severe than wet AMD.

HISTORY

Reduced visual acuity – gradual deterioration in central vision leading to difficulty with reading, recognizing faces, seeing fine details. Vision is not significantly improved with glasses. Metamorphopisa. Reduced contrast and colour sensitivity.

EXAMINATION

Drusen, focal hyperpigmentation, RPE atrophy. Geograpic atrophy can be a sign of late stage AMD. Amsler-grid testing should be used to monitor for development of wet AMD.

PATHOLOGY/PATHOGENESIS

Drusen are abnormal yellow deposits located between the RPE and Bruch's membrane. These can become calcified. The overlying photoreceptors cease to function due to lack of the required support from the RPE. Geographic atrophy represents a large well demarcated area of RPE damage.

INVESTIGATIONS

Optical coherence tomography, Fundus fluorescein angiography (FFA)

MANAGEMENT

There is no treatment for established Dry AMD. Measures to consider to prevent progression are below.

LIFESTYLE

Smoking cessation. High dose prophylcatic vitamins; C, E, zinc and beta-carotene. (Beta carotene may increase the risk of lung cancer in smokers who require a formulation without its inclusion.)

SUPPORTIVE

Counselling, low vision aids, referral to support groups. Sight-impaired/severely sight-impaired registration as appropriate.

COMPLICATIONS

Choroidal neovascularization (wet AMD).

PROGNOSIS

The presence of large drusen and pigment abnormality in one eye is associated with a 50% risk of developing AMD in the fellow eye within 5 years.

Age related macular degeneration, wet

DEFINITION

Degeneration of the macula complicated by choroidal neovascularization.

AETIOLOGY

Unknown, likely multifactorial. Excessive secretion of vascular endothelial growth factor (VEGF) may be a cause.

ASSOCIATIONS/RISK FACTORS

Increased age, female gender, smoking, hypermetropia, hypertension, alcohol intake. UV light exposure. Increased dietary fat intake. Variants in the gene coding for complement factor H, a component of the alternative complement cascade pathway, predispose to AMD.

EPIDEMIOLOGY

Accounts for 10% of cases of macular degeneration, however, is responsible for most of the sight-impaired/severely sight-impaired registrations that are made in the UK.

HISTORY

Subacute onset of decrease/loss of central vison +/- associated metamorphopsia.

EXAMINATION

Distorted vision detectable on Amsler chart testing. Fundoscopy: subretinal fluid/haemorrhage. Macular oedema, eventual disciform scar (subretinal fibrosis).

PATHOLOGY/PATHOGENESIS

There is neovascularization that develops from the choroid and extends through the RPE and into the subretinal space. The vessels are fragile and susceptible to rupture with resulting haemorrhage and oedema. Fibrosis and collagen deposition occur eventually leading to further degeneration and predisposition to bleeding of the macula. Haemorrhage and macular scarring can cause profound central vision loss.

INVESTIGATIONS

Urgent fluorescein angiography – to identify choroidal neovascularization. Optical coherence topography – aids in the detection of macular oedema and has revolutionized diagnosis and monitoring of this condition.

MANAGEMENT

• Referral to ophthalmology: for consideration of intravitreal anti-VEGF injections.
• Amsler-grid self-monitoring (allowing patients to determine progression).

LIFESTYLE

Smoking cessation/vitamin supplementation (see age-related macular degeneration, dry).

SUPPORTIVE

Low-vision aids, registration as sight-impaired/severely sight-impaired, counselling, referral to support groups.

COMPLICATIONS

Without treatment permanent visual loss almost inevitable.

PROGNOSIS

Intravitreal anti-VEGF injections have revolutionized treatment of wet AMD; a course of injections can lead to partial restoration of normal anatomy and cessation of the neovascularization. The benefit can be persistent.

Note: intravitreal injections can be associated with serious complications including endophthalmitis and retinal detachment.

Amaurosis fugax

DEFINITION

Transient monocular loss of vision.

AETIOLOGY

• There is transient interruption of the retinal blood supply. Causes of transient visual loss have been classified by the Amaurosis Fugax Study Group 1990:
• Embolic: cardiac/carotid
• Haemodynamic: arteritis, hypoperfusion, atheromatous occlusion, carotid artery dissection
• Ocular: anterior ischaemic optic neuropathy, retinal vessel occlusion
• Neurological: optic neuropathy, papilloedema, multiple sclerosis, migraine
• Idiopathic.

ASSOCIATIONS/RISK FACTORS

Stroke, transient ischaemic attack, atherosclerosis, giant cell arteritis.

EPIDEMIOLOGY

Most cases are due to underlying intracranial carotid artery disease hence the need for investigation as below to prevent stroke.

HISTORY

Monocular blurring, dimming or loss of vision lasting only seconds to minutes. The classic description (which is not ubiquitous) is of a vertically descending, curtain-like loss of vision. History should include eliciting symptoms of associated pathology and risk factors in particular those of giant cell arteritis.

EXAMINATION

Ophthalmic examination, especially for optic disc pallor, disc swelling and retinal ischaemia, e.g. cotton wool spots. Cholesterol...