1. The pupil is a hole located in the centre of the iris, hence it can become larger or smaller depending on the intensity of light as well as the object being viewed. The pupil size changes in many situations, which is referred to as the pupillary reflex. Based on the experiment carried out in this lab, a subject was placed in a dim room and a bright light was shone in front of the eye. The changes noted during this experiment include the pupil’s diameter became smaller when exposed to bright light and became larger when the light was moved away. Another way the pupillary reflex was tested was by observing an object at arm’s length and again at 15cm from the eye. The diameter of the pupil became slightly smaller (3mm to 2mm) when the object was placed closer to the eye. The changes in the pupil occur due to the presence of two layers of smooth muscles that are located beneath the iris. These two layers namely the radial and circular layer both aid in the control of the pupil diameter. The former aids muscles to contract in response to stimulation by the sympathetic nervous system in which dilation of the pupil occurs and the latter aids muscles contract in response to stimulation by the parasympathetic nervous system in which the pupils constrict. Furthermore, an advantage of placing a pinhole card in front of the eye is that it helps the subject to focus in a specific direction and on a specific object while a disadvantage of placing a pinhole card in front of the eye is that it blocks the peripheral vision of the subject.
2. Number of Cones used: L= 28ft (8534.4mm), H =3mm, l=2cm (20mm), h=?
H= (3mm’ 20mm), 8534.4mm
0.007mm / 0.003= 2.3 cones
3. Table 1. Snellen Eye Chart
This table shows the data collected for each person from the Snellen eye chart.
Jackie Selina Victoria Haleigh w/ glasses Haleigh w/out glasses
Right Eye 20/30 20/15 20/20 20/20 20/100
Left Eye 20/30 20/15 20/15 20/20 20/200
Table 2. Pseudo-Isochromatic Plates
This table shows the data collected for each person from the Pseudo-Isochromatic plates.
Number Missed from Each Color
Color Red Green Blue
H 0 2
H 0 0 0
H 0 0 0
H 0 0 0
4. Rods and cones are the two types of photoreceptors found in the eye. There are more rods than cones, and the density of each are found in separate areas of the retina. Rods are responsible for scotopic vision. Cones are responsible for the sensitivity to color. Rods are much more numerous than cones.
Rods are very useful in light and dark adaptations. They are also responsible for our motion detection. Due to their location, in part, on either side of the fovea they play the major role in our peripheral vision. There are no rods located in the fovea. In this lab, the density and location of rods was determined by the field of vision and blind spot experiments. So, we can thank our rods for our great peripheral (mom) vision.
Cones provide the sensitivity to color. Cones are divided into 3 types: red, green, and blue. Red is the most abundant, followed by green, then blue. Red and green cones are concentrated in the fovea. Blue cones are the most sensitive and concentrated outside the fovea. One way the cone density was determined in this lab was the visual acuity experiments. Cones are responsible for all our high-resolution vision because they determine color giving distinctions in our vision. Without cones we would see in in a grey scale.