Question

Kindly answer the questions. Answer all of it if possible there's just some short answers. Thanks. PLEASE ANSWER ALL OF IT, IF NOT THEN LET OTHER REAL EXPERTS DO IT BECAUSE SOME EXPERTS EVEN DO THE WHOLE THING AND AN ESSAY ABOUT IT! IF NOT, THEN IGNORE THIS POST!

Pick 5/6 questions

Eye and Vision

1. How is visual acuity tested? Describe the condition of myopia and hyperopia. What kinds of lenses are needed to correct those conditions and how does each type of lens correct the condition

2. What does processing in the retina demonstrate about on center/off surround and off center/on surround ganglion cells?

3. What can you learn by moving an on center/off surround field over a light/dark boundary? How is this effect useful for the visual system when several adjacent on center/off surround ganglion cells encounter contrast?

4. How is the retina attached to the eye? What keeps it from folding over on itself? How do people usually get a detached retina and why does this need to be repaired quickly?

5. Explain why the dot disappears in blind spot eye test.

6. A. In your own words, what is happening in image 4.2. What is optic cupping?
   Image 4.2 This is the microscopic appearance of the lesion. Explain how this occurs. [Image contributed by Nick Mamalis, MD, University of Utah]
   

B. In image 4.4 we can see the opposite condition where pressure is high on the outside of the optic disc. Why is that such a serious condition?

Answer 1

1. How is visual acuity tested? Describe the condition of myopia and hyperopia. What kinds of lenses are needed to correct those conditions and how does each type of lens correct the condition

The visual acuity test is used to determine the smallest letters you can read on a standardized chart (Snellen chart) or a card held 20 feet (6 meters) away. Special charts are used when testing at distances shorter than 20 feet (6 meters). Some Snellen charts are actually video monitors showing letters or images.

Hyperopia is a condition in which an image of a distant object becomes focused behind the retina, making objects up close appear out of focus. Myopia is a condition in which, opposite of hyperopia, an image of a distant object becomes focused in front of the retina, making distant objects appear out of focus

Shortsightedness is corrected using a concave (curved inwards) lens which is placed in front of a myopic eye, moving the image back to the retina and making it clearer. Longsightedness is corrected using a convex (outward facing) lens.

1. What does processing in the retina demonstrate about on center/off surround and off center/on surround ganglion cells

The retinal ganglion cells(RGCs) are the output stage of retinalinformation processing. They are the only cells in the retina with axons that leave the eye. The ganglion cell axons form the optic nerve and transmit retinalinformation – in the form of spike trains – to the visual target areas in the brain

1. How is the retina attached to the eye? What keeps it from folding over on itself? How do people usually get a detached retina and why does this need to be repaired quickly
   

All of the retinal breaks are identified and traction from the vitreous is removed from the breaks in particular. The fluid under the retina is drained through one of the breaks and laser is applied to seal the breaks. A gas bubble is placed to seal the break and help the retina stay attached while the eyeheals.

The key factors in preventing retinal folds following primary vitrectomy are (1) complete drainage of the subretinal fluid and (2) avoidance of submacular displacement of fluid during fluid air exchange. In the majority of cases, an internal drainage is performed through one of the preexisting retinal breaks.

Retinal detachment is a serious eye condition that happens when your retina -- a layer of tissue at the back of your eye that processes light -- pulls away from the tissue around it. Doctors also call it detached retina.

1. Explain why the dot disappears in blind spot eye test.

A blind spot, scotoma, is an obscuration of the visual field. A particular blind spot known as the physiological blind spot, "blind point", or punctum caecum in medical literature, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the optic disc of the retina where the optic nerve passes through the optic disc.

This is because your brain is "filling in" the missing information