Eyes health

The eyes are the organs of vision. Eyes and vision can be altered by disorders, diseases and other factors.
In order to measure vision, diopter, or one-tenth, is used.
Several individuals play their part in taking care of your eyes and vision health: ophthalmologists, opticians and orthoptists.
Various examinations may be used in order to detect eyes disorders and diseases.
Finally, different types of solutions may be used, depending on the disorders or the diseases.

 

Why the eyes, and what do they do?
They are the organs of vision. They can reflect light rays so as to form an image on the retina and convert this image into nervous stimuli which will then be interpreted by the brain.
The term “eye” also depicts its extensions: the eyelids, the lacrimal system or the oculomotor muscles.
What are the possible disorders of eyes and vision?
Different disorders can alter vision.
Some are caused by errors of refraction at convergence capacity level, and this is called ametropia. In that case, the image is not rightly formed on the retina. This applies to:
• Myopia, when remote objects cannot be clearly seen.
• Hyperopia, when near vision is difficult.
• Astigmatism, when images are distorted.
Other disorders may also alter vision:
• Presbyopia, which is a gradual reduction of the accommodation capacity of the eyes caused by a loss of flexibility of lens leading to a decrease of near vision.
• Strabismus, which is a parallelism defect in the two vision axis. When the two images received by the brain are too differentiated, the brain cancels the weaker one. The diverted eye will gradually lose its visual capacity and stop transmitting images to the brain. This is called amblyopia.
• Lastly, other inconvenience may develop.
What is the vision measurement unit used?
Vision defects are measured through diopters. This measurement unit is also used for spectacles and contact lenses which correct vision defects.
Diopter is a unit of measurement of optical systems capacities used to determine the level of refraction, that is to say the capacity of an object or of an environment in deviating light rays. Lenses and eyes (particularly lens and cornea) form an optical system. It is considered that a 1 diopter lens has a focal length of 1 m. A 2 diopters lens will have a focal length of ½ a meter.
The focal length corresponds to the distance between the lens or the environment generating the refraction and the rays’ convergence point, that is to say the point where the rays meet.
Specificity: myopia is measured with negative diopters. For instance, an individual with a 2 meters clear vision has myopia of ½ i.e. 0.5 diopters. It will thus be defined as 0.5 diopters myopia.
Other vision defects are measured in positive diopters.
What is the difference between diopters and tenths?
Diopters represent the capacity measurement unit of a corrective lens placed in front of the eyes so that they can see as best as possible.
Tenths express the size of the letters read at a distance by the eyes. The smaller the letters, the more the tenths.
What are the possible eyes diseases?
They are numerous. Among them :
Age-related macular degeneration, or AMD, which is a gradual decline in vision resulting in a total loss of central vision.
Cataract, which is a partial or total opacification of the eye’s lens causing a gradual decline in vision.
Glaucoma, which corresponds to a high eyes pressure level with an optical nerve problem leading to a reduction of the field of vision.
Diabetic retinopathy is caused by diabetes (increased blood sugar - hyperglycemia) and may cause blindness through an injury of the retina.

Other eyes – and their extensions- diseases exist. Among them :
Retinitis pigmentosa, which is composed of hereditary diseases attacking vision cells receiving light.
Retinoblastoma, which is a malignant tumor of the retina, of genetic origin.
Leber’s neuropathy, which is a disease causing a steep decline in vision.
Stargardt’s disease, which affects the layers of central retina resulting in an alteration in vision and retinal lesion.
Best’s disease, which is a genetic macular dystrophy causing a late decline in vision.
Central cerebri chorioretinopathy (French CRSC), which is a disease of the retina resulting in a decline in the vision of one eye.
Cystoid macula edema, which is a disease of the retina leading to a decline in visual acuity.
Some of such diseases are rare and orphan diseases. Many other diseases exist.

What are the factors which may weaken the eyes?
Several factors tend to weaken the eyes, thus making them vulnerable.
• Sun exposure may harm the eyes and cause various pathologies.
• Some elements of an individual’s environment, such as artificial lighting or workstations may cause visual fatigue and vision disorders too.
• Smoking and being exposed to cigarette smoke weaken the eyes and constitute risk factors for age-related Macular Degeneration,
• Some traumas may also harm the eyes.
• Drugs.

Who are the eyes health specialists?
Several health professionals are involved in the field of eyes health.
• Ophthalmologists, who treat eyes health.
• Opticians, who make, adapt and supply spectacles and contact lenses while abiding to the prescription of the ophthalmologist
• Orthoptists who take care of eyes rehabilitation in case of binocular vision disorders. Other professionals are also involved in rehabilitating visual impairments, such as daily life autonomy carers or mobility therapists.
What are the means available to screen vision disorders or diseases?
Various examinations can be used in order to screen possible eyes or vision disorders and diseases.
Such examinations must be carried out at certain points in life, depending on the evolution of the eyes and of the vision.
What are the different solutions available to treat vision disorders or diseases?
Different types of solutions can be used depending on the specific disorder or disease.

• Drugs of the same therapeutic class as timolol will prove useful when treating some diseases.
• Sometimes, surgery will be possible or even necessary.
• Technical aids may maximize visually impaired vision.
• Finally, devices such as spectacles or lenses may help correct refraction defects.

Date: 06/04/2013
Author: Sylvie ERVE
Organization: centich
Reference:
Only for Members: No
Content type: Good practises
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Categories: Medical & Functions, Eye - Vision impairment