Biomedical Engineering Reference
In-Depth Information
10.00 cm from the eye, the stimulus to accommodation is
−
10.00 D, and
the required accommodation is 10.00 D.
(c) First, find the power of the spectacle correction:
1
f
F
=
′
(100)(1.00)
f
=
−
3.50 D
′
′
=
−
f
28.57 cm
=
−
−
28.57 cm
−
(
−
1.5 cm)
27.07 cm
1
f
′
F
=
(100)(1.00)
−
=
F
27.07 cm
=
−
F
3.69 D
Next, find the image produced by the spectacle lens:
′
=
L
L
+
F
(100)(1.00)
−
⎡
⎥
⎤
⎥
′
=
L
+
(
−
3.69 D)
8.50 cm
′
=
−
L
15.45 D
1
l
′
L
=
′
(100)(1.00)
l
=
−
15.45 D
′
′
=
−
l
6.47 cm
The distance from the image to the eye is
−
7.97 cm [i.e.,
−
6.47 cm
+
(
−
1.50 cm)
=
−
7.97 cm].
Now determine the amount of accommodation required to focus the
image on the retina:
+
F
FP
=
L
F
A
(100)(1.00)
⎥
⎦
+
F
A
−
3.50 D
=
−
7.97 cm
⎣
F
A
= +
9.05 D
Wearing a spectacle correction, the patient must accommodate 9.05 D.
