Colour Atlas of Ophthalmology (eBook)

Ian J Constable, Arthur Lim Siew Ming (Autoren)

eBook Download: EPUB

2014 | 2. Auflage
156 Seiten
Elsevier Science (Verlag)
978-1-4832-8128-5 (ISBN)

Infos

Colour Atlas of Ophthalmology, Second Edition provides information pertinent to the fundamental aspects of ophthalmology. This book provides the correct diagnosis and treatment of many ocular disorders. Organized into 11 chapters, this edition begins with an overview of the process of assessment of a patient with eye disease, which includes taking a good history, examining the eyes with adequate illumination, and testing the visual function. This text then describes exophthalmos, which is the most common condition of the orbit and indicates the possibility of thyroid disease or a space-occupying lesion. Other chapters consider the common causes of ocular injuries, including injury from flying particles, sharp instruments, chemicals, and ocular injury associated with head injury. The final chapter deals with the common, therapeutic, and diagnostic ocular drugs. This book is a valuable resource for ophthalmologists, physicians, nurses, students, and all those paramedical personnel who have to deal with common eye disease.

Textauszug

1

EXAMINATION

Publisher Summary

The cause for a sudden loss of vision could be vascular in nature such as retinal vein occlusion, retinal artery occlusion, or vitreous hemorrhage. It could also be due to acute glaucoma, retinal detachment, or inflammatory conditions such as acute uveitis and optic neuritis. A gradual loss of vision is usually due to a refractive error, such as myopia or presbyopia, or degenerative conditions of which cataract is the most common. Flashes are momentary flashes of light due to the stimulation of the retina and are seen in retinal tears and detachments and also in vitreous detachment. Eye pain and headaches may be due to either ophthalmic or nonophthalmic causes. Binocular diplopia is usually due to extraocular muscle paralysis. Monocular diplopia is caused by disease in the eyeball, such as early cataract, lens dislocation, or corneal opacity. The assessment of distant and near visual acuity is important as it reflects the state of the macular function (central vision). The response of light directed at one pupil in a darkened room is known as the direct pupillary response. The extraocular muscles are examined by observing the position of the eyeballs with the patient looking straight ahead. The ophthalmoscope is used to observe abnormality in the ocular media, the optic disc, the retinal vessels, the fundal background, and the macula.

INTRODUCTION

In the assessment of a patient with eye disease, it is important to take a good history, examine the eyes with adequate illumination and test the visual function.

Recently, retinal and macular diseases have become more common as causes of severe visual loss. In these cases, a fundal examination with dilatation of the pupils in a darkened room is necessary.

HISTORY

A careful history of the patient’s ocular symptoms is essential. His past history and general illnesses, such as diabetes and hypertension, frequently provide useful clues.

Myopia, squint, open-angle glaucoma and dystrophic conditions have a hereditary tendency which is revealed by an inquiry into the patient’s family history. It is also useful to take note of allergies and of the medical therapy the patient is undergoing.

OCULAR SYMPTOMS

The more important symptoms include decreased visual acuity, floaters, ocular pain, headaches, itching, flashes, watering and double vision (diplopia).

Decreased visual acuity

Decreased visual acuity must always be investigated and the cause found. The cause for a sudden loss of vision could be vascular in nature such as retinal vein occlusion, retinal artery occlusion or vitreous haemorrhage. It could also be due to acute glaucoma, retinal detachment or inflammatory conditions such as acute uveitis and optic neuritis.

Gradual loss of vision is usually due to a refractive error such as myopia or presbyopia, or to degenerative conditions of which cataract is the most common. It could also be due to macular degeneration or chronic glaucoma.

Floaters

Another common ocular symptom which calls for further investigation is the appearance of floaters usually described by the patient as small, semi-translucent particles of varying shapes moving across the visual field with the movement of the eye. Single or double floaters of many months or years are common and usually harmless. But a sudden increase in floaters, especially when associated with lightning flashes and visual loss in patients with high myopia or in the elderly, suggests retinal disease, particularly retinal detachment.

Flashes

Flashes are momentary flashes of light due to stimulation of the retina and are seen in retinal tears and detachments and also in vitreous detachment. Other sensations of light may arise from migraine or lesions of the visual pathway.

Eye pain and headaches

Eye pain and headaches may be due to either ophthalmic or non-ophthalmic causes. Of the ophthalmic causes, acute glaucoma is the most important. Less frequent but just as important is iritis. Uncorrected refractive error, migraine and anxiety are common causes of headaches.

Itchy eyes

Itching around the eyes is frequently due to allergy. It may also be due to blepharitis.

Watering

In infants, watering is usually due to a blocked nasolacrimal duct. A rare but important cause of watering and irritable eyes is congenital glaucoma. Another cause is entropion of the lower lid.

In adults, watering has many causes, a common one being a blocked nasolacrimal duct. It can also occur in association with surface irritation, as in conjunctivitis, keratitis or when a foreign particle is in the eye.

Double vision (diplopia)

It is important to note whether double vision (binocular diplopia) occurs only when both eyes are opened or when one eye is occluded (monocular diplopia).

Binocular diplopia is usually due to extraocular muscle paralysis. Monocular diplopia is caused by disease in the eyeball, such as early cataract, lens dislocation or corneal opacity.

EXAMINATION

VISUAL ACUITY

The assessment of distant and near visual acuity is important as it reflects the state of the macular function (central vision). The visual acuity can be tested by asking the patient to cover one of the eyes with a cardboard or with the palm of his hand. By testing the ability of the patient to see objects such as the clock or the newspaper in his own environment, it is possible to get a gross assessment of the visual acuity as blind, grossly defective, subnormal or normal.

Distant visual acuity

It is usually necessary to record a patient’s distant visual acuity more accurately with Snellen’s chart. It is read at six metres, with the letters diminishing in size from above.

The patient has normal vision if he is able to read the line of letters designated as 6/6 at or near the bottom of the chart. The scale for decreasing distant visual acuity is 6/9, 6/12 (industrial vision), 6/18, 6/24, 6/36 and 6/60 (legal blindness in some countries).

If the patient is unable to read the letters, he is asked to count the examiner’s fingers which are held a metre away. If his answers are correct, he has distant visual acuity of “count fingers” at a metre. If he is unable to count the fingers, the examiner should move his hand in front of the patient’s eyes. The visual acuity is then said to be “hand movement”. If he can see only light, visual acuity is recorded as “perception of light”. If he cannot see any light, visual acuity is recorded as “no perception of light” which is total blindness.

In some countries, patients with less than 6/60 vision are classified as legally blind. Patients who can see 6/12 have sufficient vision to work in most industries and are said to have “industrial vision” which is also the visual requirement for driving.

VISUAL ACUITY TRANSCRIPTION TABLES

Pinhole

In testing distant visual acuity, looking through a pinhole is useful for patients with blurred vision. Vision can be improved if the defective vision is due to refractive error. It cannot be improved if it is due to organic eye disease.

Near visual acuity

The common visual acuity tests are the Jaegar test and the ‘N’ chart, usually read at a distance of 30 cm. The Jaegar test is recorded as J1, J2, J4, J6, etc, and the ‘N’ chart as N5, N6, N8, N10, etc. Standard small newsprint is approximately J4 or N6. Each eye is tested in turn with the other covered. Middle-aged patients (presbyopic age) must be tested with their reading glasses.

Difficulties in examination

It is often difficult to test visual acuity in young children as well as patients who are illiterate, uncooperative or malingering. Frequently only an estimate can be made. The E-chart, picture cards or small coloured objects may be used. It can be extremely difficult to determine whether a patient is malingering without the use of special tests.

VISUAL FIELDS

Confrontation

The visual fields can be recorded approximately by using the confrontation test. The patient covers the eye which is not being tested with his palm and fixes the other at the examiner’s nose, ear or eye. A target is then brought into his field of vision from the side and the point at which the patient sees the object is noted. The eye is tested in the different meridians, usually 8.

Alternatively, the examiner’s fingers are held at a distance of one metre and the patient is asked to count them in the different quadrants, that is, the superior temporal, the inferior temporal, the superior nasal and the inferior nasal quadrants.

EXTERNAL EYE EXAMINATION

This is done with good illumination from either a window or a bright torch. A magnifying glass facilitates examination and should be used whenever...

Produkt-Details

• Erscheint lt. Verlag: 20.3.2014
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Augenheilkunde
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Chirurgie
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Neurologie
• ISBN-10: 1-4832-8128-0 / 1483281280
• ISBN-13: 978-1-4832-8128-5 / 9781483281285