Understanding vision and the brain

Diseases which affect the visual pathway or the nerves to the eye muscles are often serious. This article summarises the anatomy and function of the 2nd, 3rd, 4th and 6th cranial nerves and the signs and symptoms which are important in making a correct diagnosis. N euro-ophthalmology includes the specialties of neurology and ophthalmology. Skills of both specialties are needed to assess patients. A detailed history and clinical examination are needed in order to make a differential diagnosis and create a management plan. There are two broad groups of neurological conditions that can affect someone's vision: 1 Those which affect the visual pathways in the brain and 2 Those which affect eye movements. If the condition affects the visual pathways, there can be loss of visual acuity, loss of visual field, or difficulties in understanding the visual world, depending on where the lesion is in the visual pathway. If the condition affects the 3rd, 4th or 6th cranial nerves, the main symptom is double vision (diplopia) due to restricted eye movements. The visual pathways comprise the optic nerve, optic chiasm, optic tract, optic radiation and the visual cortex in the occipital lobes. Nerve impulses arising in the retina travel via the optic nerve to the optic chiasm. In the optic chiasm there is " crossing over " of some visual information, so that images which fall on the right visual field of each eye Diseases which affect the visual pathway or the nerves to the eye muscles are often serious. This article summarises the anatomy and function of the 2nd, 3rd, 4th and 6th cranial nerves and the signs and symptoms which are important in making a correct diagnosis. N euro-ophthalmology includes the specialties of neurology and ophthalmology. Skills of both specialties are needed to assess patients. A detailed history and clinical examination are needed in order to make a differential diagnosis and create a management plan. There are two broad groups of neurological conditions that can affect someone's vision: 1 Those which affect the visual pathways in the brain and 2 Those which affect eye movements. If the condition affects the visual pathways, there can be loss of visual acuity, loss of visual field, or difficulties in understanding the visual world, depending on where the lesion is in the visual pathway. If the condition affects the 3rd, 4th or 6th cranial nerves, the main symptom is double vision (diplopia) …