Intraocular lenses in the 21st century

Editorial

Visual evoked electrical and magnetic response to half-field stimulation using pattern reversal stimulation

The visual evoked magnetic response to half-field stimulation using pattern reversal was studied using a dc-SQUID coupled to a second-order gradiometer. The main component of the magnetic response consisted of a positive wave at around 100ms (P100M). At the same time this component was present the reponse to half-field stimulation consisted of an outgoing field contralateral and extending to the midline. When the left half-field was stimulates the outgoing field was over the posterior right visual cortex and when the right half field was stimulated it was over the left anterior visual cortex. These findings would correltly identify a source located in the contralateral visual cortex. The orientation of the dipoles was not that previously assumed to explain the paradoxical lateralization of the visual evoked potential. The results are discussed in terms of both electrical and magnetic models of the calcarine fissure.

Looking at Alzheimer's disease: Part 1 symptoms, diagnosis and changes in the brain

In this, the first of a series of articles, the natural history of Alzheimer's disease will be discussed as well as the methods of diagnosis and the pathological changes which underlie the symptoms.

Alzheimer's disease Part 2: visual changes

This article describes the pathological changes that have been observed in different parts of the visual system in Alzheimer's disease as well as the visual symptoms which may result from these changes.

Alzheimer's Disease Part 3: the Alzheimer patient in the practice

As a result of the increasing proportion of elderly people in the UK population, it is likely that the optometrist will see patients with dementia in the practice. These patients pose particular problems for the optometrist who has to carry out refraction or an eye examination. Since each case of dementia is unique, it is impossible to give guidelines which will ensure the cooperation of all patients. However, a knowledge of the changes in personality shown by patients and the special problems that can arise is helpful in attempting to test the demented patient.

Multiple sclerosis: natural history, diagnosis and changes in the brain

This article describes the general symptoms, diagnosis and changes in the nervous system in multiple sclerosis. A second article will describe the specific visual symptoms which are believed to be characteristic of the disease.

Ophthalmological manifestations of multiple sclerosis

Optic neuritis, as a result of the formation of demyelination plaques in the optic nerve, is one of the commonest early symptoms of multiple sclerosis. Hence, it is important that optometrists are aware of the symptoms of optic neuritis and of the conditions with which it can be confused. However, only a proportion of patients with optic neuritis will develop the symptoms of multiple sclerosis. The first part of the article describes the symptoms and differential diagnosis of optic neuritis and its relationship with multiple sclerosis. In the second part of the article, the variety of visual changes and symptoms which can be observed in multiple sclerosis patients will be described.

AIDS: structure, replication and spread of the AIDS virus

AIDS (Acquired Immune Deficiency Syndrome)was first, described as a new disease of humans in 1981. The origins of the disease are controversial. AIDS is caused by a retrovirus, a type of virus which rarely attacks human cells. The first virus of this type recorded in humans is reponsible for a type of leukaemia and was identified in 1978. AIDS is thus the third type of human retrovirus to be discovered and hence, is referred to as T-lymphotrophic virus III (HTLV-III). For viruses to replicate, they have to invade a host cell which in this case is a T4-lymphocyte, a type of white blood cell that regulates the immune system. The problems of the disease result directly from the death of these cells. As a consequence, the immune system is compromised leading to a number of opportunistic secondary infections and other disorders.

AIDS: neurological and ophthalmological aspects

Although overt ocular symptoms are not often encountered in AIDS patients, many exhibit subtile neuro-ophthalmic signs and symptoms. This article describes the neuropsychiatric symptoms as well as the neuro-ophthalmic conditions which have been reported recently in AIDS patients. The degree to which optometrists may be vulnerable to the AIDS virus from contact with patients in practice will also be discussed.

Parkinson's disease Part 1: symptoms, diagnosis and changes in the brain

Parkinson's disease is a common neurodegenerative disorder of middle-aged and elderly people. There are two aspects of the disease of special interest to optometrists. First, visual problems may be present in a proportion of patients with the disease. In addition, the disease is treated by a variety of drugs, some of which may have ocular complications. This article describes the incidence, symptoms, diagnosis, causes and changes in the brain in Parkinson's disease.

Parkinson's disease Part 2: visual aspects

There are two aspects of Parkinson's disease specifically discussed in this article. First, visual symptoms are present in a proportion of patients with the disease and it is important that these are recognised. Second, Parkinson's disease can be successfully treated with drugs, but some of the drugs have ocular side effects and optometrists need to be aware of the signs of ocular complication in these patients.

Retinoblastoma and the new genetics

Wardop first described retinoblastoma in 1809. It is the most common intraocular tumour of childhood and the most common tumour of the retina. It was originally thought to be a glioma arising from glial cells of the retina. However, in 1926 it was recognised as a tumour of undifferentiated photoreceptor cells. This article describes the basic clinical and pathological aspects of retinoblastoma, the advances in molecular genetics which have led to the discovery of the gene responsible, and the defects which have been discovered in the retinoblastoma gene.

Retinitis pigmentosa and the new genetics

This article describes the recent advances that have been made in understanding the molecular genetics of retinitis pigmentosa (RP). The basic clinical and pathological aspects of RP will be described, together with the patterns of inheritance exhibited by the disorder. In addition, the most important genes that have been linked to RP will be discussed as well as the advances in molecular genetics which have led to the identification of mutations in these genes.

The human immune system: Part 1

The immune system protects the human body against infectious and maligant disease. The concept of an immune system arose because of the observation that an attack of measles or mumps, two common childhood diseases, conferred an immunity on the individual, the immunity being specific to the disease. It was only much later that it was discovered that a system in the body conferred this immunity.

The human immune system Part 2: auto-immune disorders

For the immune system to function effectively, the body must be able to distinguish foreign antigens from self-antigens. However, the mechanisms which maintain this distinction may break down and result in auto-immune disease in which self-reacting antibodies and T-cells are produced. This article discusses first, the evidence for the existence of human auto-immune disease and second, the auto-immune diseases which have characteristic ocular symptoms.