Video 2.1 : The normal eye: The retina and the macula
A thin membrane which lines the inner part of the eye
Consisting of :
- Visual cells sensitive to light or photoreceptors
- Rods: responsible for night-time vision.
- Cones: responsible for day-time vision and differentiate between colours.
- Nerve cells enable transmission of visual information to the brain via the optic nerve
Organised in two areas :
- The peripheral retina is involved in peripheral vision, i.e. spatial vision involved in perception of the environment.
- The macula or macula lutea (the yellow spot) (central retina)
- Located at the centre of the retina, in the optic axis of the eye
- Transmits 90% of visual information processed
- Responsible for visual acuity and for central vision: precise vision involved in reading, writing, recognition of details and of colours.
Age-related macular degeneration
- A degenerative disorder of the macular retina
- Onset most commonly after 50 years of age.
- Results in irreversible alteration of central vision
- Central vision: precise vision involved in reading, writing, recognition of details and of colours.
- Does not lead to complete blindness, peripheral vision is conserved
- Peripheral vision: spatial vision involved in perception of the environment. (2) (3)
- The 3rd leading cause of visual deficiency world-wide
- Accounts for 8.7% of causes of visual deficiency
- The leading cause of decreased visual acuity in the industrialised countries (3)
- Prevalence in the population of France: 8% (4)
- The incidence increases in the population with ageing (5)
- 1% of persons 50 to 55 years,
- about 10% of subjects 65-75 years
- of 25 to 30% of subjects over 75 years of age
- A disease which risks becoming wide-spread world-wide as the result of increasing life span (3)
Aetiology and risk factors
- Age: +50 years
- Genetic susceptibility (6):
- Multifactorial, polygenetic
- Family heredity
- Identification of genetic areas associated with the disease (Complement Factor H)
- A healthy and balanced diet, high in green vegetables and in fresh fruits and fish may delay onset of the disease
- Repeated exposure to UV radiation is a suggested risk factor.
- Arterial hypertension, cardiovascular disease, hypercholesterolaemia. (2) (4)