Lesson 7 - Refractive Errors Flashcards

Question

Astigmatism is different from nearsightedness and farsightedness because it makes vision ___.

Answer 1

Astigmatism is different from nearsightedness and farsightedness because it makes vision blurry at all distances. They may even see “ghost images” around objects

Answer 2

Doctors can correct this condition with glasses, contact lenses, or refractive surgery

Answer 3

1. Simple myopic astigmatism - This is when there is no power in one axis or meridian, and 90 degrees away from that axis or meridian, the eye is nearsighted. Prescription example: plano –4.00 x 090. 2. Simple hyperopic astigmatism - In this type, the power is plano in one axis. In the other axis, 90 degrees away, it’s farsighted. Prescription example: +4.00 -4.00 x 090. 3. Compound myopic astigmatism - Here, the eye is nearsighted in both axes. However, it’s more nearsighted in one axis than the other. Prescription example: -2.00 -2.00 x 180. 4. Compound hyperopic astigmatism - In this type of astigmatism, the eye is farsighted in both meridians, but it’s more farsighted in one meridian than the other. Prescription example: +2.00 +2.00 x 090. 5. Mixed astigmatism - In this case, one meridian is nearsighted, and the other is farsighted. Prescription example: +2.00 -4.00 x 090.

Answer 4

Doctors can correct presbyopia with reading glasses or contact lenses.

Answer 5

While aging is the cause of most presbyopia, it can also develop at an earlier age in people with diabetes, multiple sclerosis, or some cardiovascular diseases. In addition, some drugs—particularly antidepressants, diuretics, and antihistamines—can contribute to this condition.

Answer 6

People can develop strabismus if they suffer head trauma, have a stroke, have epilepsy or multiple sclerosis, or develop brain tumors. Thyroid conditions and nerve or muscle disorders can also cause this problem. Sometimes, kids who are farsighted (hyperopes) develop what we call accommodative strabismus or accommodative esotropia because they’re overconverging while trying to focus up close.

Answer 7

Strabismus can affect either one eye or both eyes.

Answer 8

Strabismus

Answer 9

While it’s especially common in “preemies” and children with developmental problems like Down syndrome or cerebral palsy, most kids with strabismus have no other health problems.

Answer 10

Strabismus can be either intermittent or constant. People with intermittent strabismus are more likely to exhibit the problem when they’re tired, sick, or stressed.

Answer 11

Depth perception or stereopsis—the fusing of images from the two eyes into a clear picture. Stereopsis is what allows us to see in three dimensions.

Answer 12

The most common tools doctors use to treat strabismus are eye muscle surgery and vision therapy.

Answer 13

Orthoptics (which means straight eyes) is the science of using instruments to help realign the eyes.

Answer 14

When a person who’s had misaligned eyes for some time has surgery to align the eyes, the straightened eye has to start using a different part of the retina. Vision therapy exercises help train that new part of the retinal nerve fiber layers to receive signals and transport them to the brain. Vision therapy involves orthoptics, but it also includes eye exercises that can improve visual and perceptual efficiency even if the eyes are straight. The approaches doctors use in vision therapy include computer programs, lenses, prisms, eye patches, and eye-hand coordination exercises. Vision therapy typically is most successful for young children

Answer 15

vision in only one eye

Answer 16

When treating patients with monocular vision, all eye care professionals should recommend that they wear sunglasses consistently when they’re outdoors and advise them to use protective eyewear whenever they play sports or do hobbies such as woodworking or gardening. Always tell them to use safety glasses if there is any risk of danger at the workplace. In addition, always stress the importance of having impact-resistant lenses in their regular glasses and wearing impact-resistant lenses—even if they don’t need prescription lenses. Counsel contact lens wearers not to overuse their lenses (if they insist on wearing contact lenses) or take any unnecessary risks that would endanger their good eye. And here’s another good tip for patients with monocular vision: Recommend that they wear sunglasses with a slight wrap to them to help prevent the risk of things flying into the good eye from the periphery.

Answer 17

Likely to be used in vision therapy. These are lenses that have a thick base and a thin apex. Lenses bend light. The thicker base of a prism slows down the light passing through it, while the thinner apex lets the light through more quickly. As a result, the light passing through the prism bends toward the base and bends toward the apex as it leaves the prism. Prisms displace an image, making it appear in a different direction. This moves the patient’s eye in the desired direction. As a result, prism can be prescribed to cause an eye to appear cosmetically straighter or can be prescribed to aid the focus of a slightly turned eye. The prisms in lenses can have bases pointing up, down, left, or right. Doctors can use prisms to train the eye to move in a different direction if the eyes are turned too far in, out, up, or down while reading or looking in the distance.

Answer 18

Myopia is usually corrected by single-vision glasses worn for distance only. Remember that myopia is a problem with blurred vision usually in the distance, so the prescription is usually prescribed for distance only. Sometimes the person is so nearsighted that they still need a prescription for near, but it will be less strong. In this case, they can have two pairs: one for distance and one for near. This is commonly the case for computer monitor users who don’t need their strong distance prescription for close work but still need a weak prescription. Bifocals and progressive lenses are sometimes prescribed for myopia as well if the patient is presbyopic also. In addition, a young myopic person may be prescribed bifocals or progressives lenses to enable them to have a lesser or no prescription to look through when they look down to read.

Answer 19

Hyperopes, usually need their glasses to read, but sometimes also need glasses for both distance and near, so like myopes, they can be prescribed single-vision glasses for near only, one for distance only or progressives or bifocals.

Answer 20

Astigmatism affects vision for all distances, so people with astigmatism are usually prescribed glasses to be used all the time, but if they also have myopia or hyperopia, then the previously discussed options will need to be considered as well. There are contact lenses available for astigmatism as well. Most people need at least two or more pairs of prescription glasses, one clear and one sunglass.

Answer 21

Recall from the previous lesson all the lens choices for presbyopia (multifocal lenses). The doctor will usually have the specific lens design specified on the prescription since there are so many options. If not, you will need to ask your patient if they have had progressive lenses before or not. Usually, people who have had progressives before will continue with them; however, if you have a patient who did not like their progressive lenses for whatever reason, you can offer them a separate single-vision pair for distance and one for near, a bifocal, a trifocal, or contact lenses.

Answer 22

Remember, astigmatism is when your eye’s cornea or lens is irregularly shaped. Normally, the cornea and lens are curved equally in all directions. If we view the eye as a sphere, “against-the-rule” is astigmatism where the steepest curve lies near the 180-degree meridian (imaginary line connecting east and west points of the cornea), and “with-the-rule” astigmatism (line connecting north and south points) is near the 90-degree meridian. With-the-rule is by far the most common type of astigmatism.