STUDENT NAME: ________________________________

Chapter 10 Homework

Please read the following Case Study and answer the given questions:

A Trip to the Eye Doctor by Hollie L. Leavitt, Department of Biology, College of Western Idaho, Nampa, ID

“Samantha,” called a voice from the front of the optometrist’s office. Samantha looked up. Jason, the optometrist assistant, was calling her name. Samantha smiled as she walked over to meet him.

“It’s good to see you again,” Jason said. “Let’s get you back and get started on some of the pre-exam tests. Dr. Thomp- son is with another patient but will be ready to see you soon.”

Jason led Samantha through a hall back to the pre-exam room. Machines designed to test different aspects of vision were lined up across the room.

“Let’s have you start here with the visual field test, Samantha” said Jason. “Do you remember this test from last year’s exam?”

“Yes,” Samantha replied. She sat down at the machine, placed her face in the forehead and chin rests and stared through the opening in the machine to a light on the inside.

“Okay Samantha,” Jason began. “I want you to keep your eyes focused on the light inside the machine. Every so often, you’ll notice lights flashing in areas of your peripheral vision. Each time you do, I want you to click this button letting me know that you saw the flashing lights.”

1.) For Samantha’s central vision, which region of the eye are light rays from the object in her vision landing? 

2.) What are the two types of photoreceptors, and which is more heavily concentrated in the aforementioned region of the eye?

3.) Age-related macular degeneration (AMD) is a disease that robs the elderly of their central vision due to the loss of key photoreceptor cells. Why would the loss of photoreceptors affect the conductance of visual stimuli through the optic nerve and into the brain? Explain.

As she finished up the visual field test, Samantha was curious about what she was being examined for. “Jason, I took an A&P class in college and we did a unit on eyes,” she began. “Now that I understand better the anatomy of the eye, I’m curious about what this test is looking for.”

” That’s great, I loved that class!” Jason replied. ” is particular test looks to see if there are any blind spots, or areas where you’ve lost the ability to see, in your peripheral vision. You would think it would be obvious if you had a blind spot, but often they develop slowly over time and people don’t notice them. Your brain is also very good at filling in missing visual information, so sometimes people lose an extensive amount of their peripheral vision and don’t even notice! That’s why we specifically test for it here, so that if there is a problem with vision loss we can treat it before it progresses.”

“We talked about the physiological blind spot that is in the peripheral field of vision in my A&P class,” said Samantha. “Isn’t it normal to have a blind spot?”

“Everyone has the physiological blind spot,” Jason explained. ” That is normal. But developing other blind spots in addition to that one is not normal.”

“What causes other blind spots to develop?” asked Samantha.

” There are a lot of things that can do it, but the most common is a disease called glaucoma. Here’s a model of the eye, which you probably are familiar with,” Jason began. “Glaucoma develops when there is increased pressure in the anterior chamber of the eye due to a buildup of aqueous humor.”

4.) Label the given anatomical features of the eye.

5.) What accounts for the “physiological blind spot?”