Biomedical Engineering Reference
In-Depth Information
Ciliary body
Suspensory ligament
Optic nerve
Iris
Optic disc
Lens
Cornea
Anterior ch
amber
Posterior chamber
Scleral venous sinus
Macula lutea
Choroid
Sclera
Retina
Vitreous body
FIgUre 10.1
(See color insert.)
The structure of the eye.
F
F
A
F
'
F
B
FIgUre 10.2
Accommodation.
The ciliary muscle is a smooth muscle, innervated by the parasympathetic system, and
it acts when an image is unfocused. This process is closely related to convergence, which
keeps centering and focus synchronized (Figure 10.3).
This implies that the skills of a patient may sensibly vary as the distance at which the
assessment is carried out changes.
Another less known element that should always be considered is the functional char-
acteristics of the retina (Liuzzi and Bartoli 2002). The retina is made up of two types of
receptors: the cones, which are divided into three different groups that each detect one
primary color, and the rods, which likewise all react to the different wavelengths of the
light (Figure 10.4).
The receptors are connected to bipolar first-order cells and ganglion second-order cells.
Their axons unite in the blind spot to form the optical nerve (Figure 10.5).
