Case Study 5 PDF

Preview

Summary

case study...

Description

1

A Trip to the Eye Doctor

Koheun Lee BIO-209-101 Dr. Coleen Di Lauro 30 July 2020

Case Study: A Trip to the Eye Doctor

2 KOHEUN LEE

Part I 1. Central vision is used to read, drive, and see pictures or faces and allows a person to see shapes, colors, and details clearly and sharply. During the visual field test, Samantha’s central vision is focused on the light straight ahead. 2. The light rays from the object in Samantha’s central vision are focused on the macula in the center of the retina. 3. The peripheral vision is the side vision that allows the eye to view objects on either side of the body. The objects in Samantha’s peripheral vision hit the rods, which are on the outside of the macula of the retina. 4. The optic disc, which is called the blind spot, is responsible for the physiological blind spot because it contains no rods or cones. 5. Please see below:

6. Aqueous humor (transparent watery fluid) nourishes the lens and cornea.

3 KOHEUN LEE

7. Glaucoma, a disease caused by an increase in pressure within the eye, is as a result of blockage of the flow of aqueous humor (a watery fluid produced by the ciliary body). The normal flow of the aqueous humor is (1) from the ciliary body into the posterior chamber; (2) from the posterior chamber through the pupil into the anterior chamber; (3) from the anterior chamber through a sievelike layer of tissue in the lining of the eyeball, located at the outer peripheral of the iris and into a circular channel (the canal of Schlemm); from here the aqueous humor flows into blood vessels. Blockage of the aqueous humor flow causes increased pressure in the posterior chamber, this pressure is transmitted by way of the vitreous to the optic nerve head, then the retina. This abnormally high intraocular pressure that is unrelieved causes vision impairment. 8. As mentioned in the answer above, the increased pressure in the anterior chamber may cause pressure on the optic nerve which could cause damage and affect the peripheral vision. 9. Normal intraocular pressure helps support the shape of the eye, ultimately supporting the two million parts of the eye that help people see. 10.Above normal and below normal. 11. The tonometry test would be able to catch glaucoma in earlier stages because it measures if an increased pressure is present inside the eye, also known as intraocular pressure or IOP. Part II 1. A person with 20/500 vision can clearly see something 20 feet away that a person with normal vision can see clearly from a distance of 500 feet. 20/500 vision is considered as a profound visual impairment, or profound low vision. 2. 20/20 vision is a term used to express normal visual acuity measured at a distance of 20 feet -- meaning you can clearly see at 20 feet something that should normally be seen at that

4 KOHEUN LEE

distance, whereas, 20/15 vision is sharper than the average -- here you can see a line in the eye chart at 20 feet whereas the average person can only see the same line when they are 15 feet away. 3. Eye B is focused on a closer object because the lens becomes more curved, ultimately causing greater refraction of the light rays. 4. A convex lens has at least one convex surface (such that light passing through it may be brought to focus), whereas, a concave lens has at least one concave surface (light rays passing through it bend away from its optical axis). 5. A concave surface causes light rays to diverge, whereas a convex surface causes light rays to converge. 6. A convex lens causes light rays to converge at a focal point; please see the focal point as labeled below:

7. The lens would bend light rays that pass through which causes light rays to converge. Part III 1. Normal vision occurs when light is focused directly on the retina, rather than in front or behind it.

5 KOHEUN LEE

2. The focal point is in front of the retina in myopia, this occurs when the physical length of the eye is greater than the optical length. 3. Please see below:

4. Myopia occurs if the eyeball is too long or the cornea is too curved. As a result, the light entering the eye is not focused correctly and distant objects look blurred. 5. Samantha’s vision began to get progressively worse because of her eyes getting longer; this causes the focal point to move further from the retina and ultimately causing a decrease in her vision. 6. Glasses with concave lenses cause rays of light to diverge and focus the light back onto the focal point of the retina. 7. Hyperopia, or farsightedness, is when you see things that are far away better than things that are up close. 8. The focal point is behind the retina because the length of the eye is too short. 9. The cornea doesn’t refract light properly in hyperopia, so the point of focus falls behind the retina which makes close-up objects appear blurry.

6 KOHEUN LEE

10. Because glasses with convex lenses refract light before it enters the eye, these lenses subsequently decrease the appearance in distance of the image. 11. (most convex) B – A – C (least convex) 12. Cornea B would bend the light rays to a focal point of the shortest distance; this is because the focal point is further in front of the retina. 13. Cornea C would bend light rays to a focal point of the longest distance; this is because the cornea is flat which gives a longer distance to the light being absorbed. 14. Because of Samantha’s myopia, the shape of her cornea is too convex. Therefore, the LASIK

operation will be set to be less convex, making her cornea more flatten....