What is the Macula?
The macula refers to the centre of the retina (a film of tissue lining the inside wall of the eye, and which is essential for vision).  The macula is the most sensitive part of the retina, and is responsible for colour vision and detailed central vision.  The macula allows us to perform tasks that require good central vision such as reading, watching television, recognizing faces and driving [see figure 1].

Figure 1

Visually consequential age-related macular degeneration:
Visually consequential age-related macular degeneration (AMD) is a disease of the macula that results in loss of central vision.  Specifically, visually consequential AMD is the result of choroidal neovascularisation (i.e. abnormal blood vessels growing behind the retina [see figure 2] and/or atrophy (i.e. disintegration of the retina and choroid [see figure 3]).  Visually consequential AMD is the leading cause of age-related blindness in the western world, and is becoming increasingly prevalent throughout the world. Recent figures demonstrate that, in the developed world, AMD accounts for over 50% of cases of registered blindness.  As its name suggests, the prevalence of visually consequential AMD rises with increasing age, and therefore the prevalence and incidence of this disease are on the increase because we are living longer [see figure 4].

Figure 2	Figure 3

Figure 4a

Figure 4b

Figure 4c

Precursors of visually consequential AMD

Soft drusen
Soft drusen are small, circular dots (white or yellow in colour) that can develop at the back of the eye [see figure 5].  The presence of soft drusen is a sign of early AMD, which may progress to visually consequential AMD.  An eye care specialist can see drusen during a typical eye examination.

Pigmentary changes
Areas of hyper- and hypo-pigmentation at the macula represent another sign of early AMD [see figure 6], and indicate that the eye is at risk of developing visually consequential AMD; hyper-pigmentary changes refer to areas of pigment clumping, whereas hypo-pigmentary changes refer to areas of depigmentation, within the macula.

Figure 5	Figure 6

What happens if you have visually consequential AMD?
Visually consequential AMD is particularly frustrating because (if untreated or untreatable) it results in a loss of central vision. In other words, someone with visually consequential AMD can see everything except what he/she is looking at, and is therefore unable to read, watch TV, recognize faces or drive. Visually consequential AMD dramatically reduces an individual’s quality of life.

Interesting statistic
When asked what health condition they fear most, one third of people will say blindness, another third will say cancer, and the final third will cite a wide range of ailments or fears. However, most people regard it unlikely that they will develop blindness or vision loss. It is worth emphasising that even small degrees of visual loss have major adverse impacts on the quality and length of life.  For example, vision of 6/12 (about 83%) or less is associated with the following: loss of driving licence; increased risk of falls, hip fractures and depression; loss of social independence; admission to nursing homes three years before their counterparts with normal vision; not to mention, perhaps most importantly, a reduced ability to enjoy healthy and independent ageing.

What causes visually consequential AMD?
Although the exact cause of visually consequential AMD remains uncertain, it is known that damage by free radicals within the eye plays a role.  Free radicals are unstable molecules, and are produced in response to a person metabolising oxygen, and in response to light entering the eye.  Because we use oxygen to live and because we are constantly exposed to light, damage caused by free radicals is unavoidable.

What are the symptoms of visually consequential AMD?
The main symptom of visually consequential AMD is dim or fuzzy central vision, which can affect the ability to carry out fine detail visual tasks such as reading.  With this disease, objects may appear distorted or smaller than they really are. Faces will become more difficult to recognize. As the disease progresses, central vision is totally lost.  However, good peripheral (navigational) vision is retained.

Top