Vision Correction

Question 1

What is refraction?

Answer 1

bending of light rays as they pass from one transparent medium through another of different density

Question 2

What is normal refraction?

Answer 2

light that is reflected from an object is refracted through the cornea and lens directly onto the retina

Question 3

When does myopia occur?

Answer 3

the refracting power of the eye is too strong

Question 4

THe contact lens for myopia is shaped how?

Answer 4

minus and divergent

Question 5

When does hyperopia occur?

Answer 5

the refracting power of the eye is weak

Question 6

If contact lens for hyperopia is shaped how?

Answer 6

plus and convergent

Question 7

What kind of lens is astigmatism corrected with?

Answer 7

spherical lens

toric- a lens with different optical power and focal length in two orientations perpendicular to each other

Question 8

So for myopia and astigmatism what will the lens look like?

Answer 8

spherical and divergent

Question 9

What is an incisional procedure that corrects vision?

Answer 9

Radial keratotomy

Question 10

What is the most common surgical procedure for vision correction?

Answer 10

LASIK

Question 11

What does LASIK stand for?

Answer 11

laser-assisted in situ keratomilusis

Question 12

Which procedures are surface ablation procedures?

3

Answer 12

1. photorefractive kertotoamy (PRK),
2. laser epithelial keratomileusis (LASEK) and
3. epitherilial laser keratomileusis (epi-LASIK)

Question 13

What procedures are intracorneal procedures?

Answer 13

corneal inlays

Question 14

Name a generic term, which includes all surgical procedures on the cornea to improve vision by changing the shape, and thus the refractive index of the corneal surface?

Answer 14

Refractive keratoplasty

Question 15

What are three types of refractive keratoplasties?

Answer 15

1. Keratotomies, ie corneal incisions
2. Keratectomies, ie removal of corneal epithelium
3. Keratomileusis, ie reshaping a stromal layer of the cornea

Question 16

What are some precautions for patient selection for vision correction surgery?

Answer 16

patients with presbyopia in patietns 60-69 (higher retreatment rates)

Question 17

Contraindications for vision correction surgery?

6

Answer 17

1. Autoimmune disease
2. collagen vascular disease and 3. immunodeficiency disease affect corneal healing
3. Women who are pregnant or nursing have fluctuating visual acuity
4. Patients with abnormal wound healing (keloids) may have abnormal corneal healing
5. DM—can perform if well-controlled, without cataract or diabetic retinopathy

Question 18

Specific ocular contraindications for vision correction surgery?
7

Answer 18

1. Keratoconjunctivitis sicca (dry eye syndrome)
2. Exposure keratitis
3. Neurotrophic keratitis (degenerative disease caused by impaired corneal innervation)
4. Lid disorder affecting the tear layer
5. Patient with a h/o herpetic keratitis
6. Any patient with an abnormal shaped cornea
7. Sever rosacea

Question 19

Why dont we use radial keratotomy anymore?

What kind of vision impairment was it used for?

Answer 19

Not accurate
didnt work in everyone
higher risk of infection
have to do second eye six weeks apart

incisions in periphery make central cornea flatter

myopia

Question 20

Describe HE Excimer laser surgery

Answer 20

Emits an ultraviolet beam with sufficient energy to break intermolecular bonds with the cornea (“photoablation”)

Using UV beam to break bonds in cornea removing discrete volumes of cornea stroma

Question 21

In LASIK surgery what is our goal in farsighted people?
Nearsighted people?
Astigmatism?

Answer 21

to flatten the too steep cornea
to steepen the too flat cornea
smoothing irregular cornea into a more normal shape

Question 22

What are the disadvantages of LASIK?

4

Answer 22

1. Changes made to the cornea cannot be reversed after LASIK
2. Technically complex—problems may occur when the doctor cuts the flap which can permanently affect vision
3. Can sometimes bt rarely cause a loss of “best” vision
   (Your best vision is the highest degree of vision that you achieved while wearing your contacts or eyeglasses)
4. Costs $500-$1000 per eye

Question 23

Advantages of LASIK

5

Answer 23

1. Around 90% of patients will have their desired vision
2. Associated with very little pain
3. Vision is corrected nearly immediately or by the day after
4. No bandages or stitches
5. Adjustments can be made years after to further correct vision

Question 24

Potenital side affects of LASIK?

6

Answer 24

1. Discomfort for 24-48 hrs after surgery
2. Glare
3. Seeing halos around images
4. Difficulty driving at night
5. Fluctuating vision
6. Dry eyes

Question 25

In Photorefractive Keratectomy (PRK) where is corneal tissue removed in myopia? In hyperopia?

Answer 25

myopia- is removed in its center | hyperopia- removed in its periphery

Question 26

What takes longer to heal LASIK, RK or PRK?

Answer 26

PRK is the longest and has a greater potential for scarring dont see results as quick

Question 27

Describe LASEK vision correction

Answer 27

A very thin corneal flap is made (70 microns) A few drops of a 20% alcohol solution are instilled and left on the cornea for 30 seconds that washed with water and dried The eximer laser treats the stroma just like in LASIK Uses alcohol, LASIK doesnt

Question 28

Advantages of LASEK? | 3

Answer 28

1. Thinner corneal flap may avoid corneal ectasia (cornea bows anteriorly) 2. LASIK requires more complicated equipment 3. Risks of infection are easier to manage with a thinner flap

Question 29

Disadvantages of LASEK? | 3

Answer 29

1. The thin corneal flap may dislodge postop causing greater pain 2. Slower optical recovery time 3. Can cause stromal haze in treated myopic patients

Question 30

What kind of vision can crystalens affect?

Answer 30

hyperopia or presbyopia

Question 31

What does the crystalens proceddure consist of?

Answer 31

The natural lens of the eye is removed and replaced with a plastic lens

Question 32

Replacing the natural lens of the eye with crystalens eliminates the chance of what?

Answer 32

cataracts

Question 33

Describe orthokeratology

Answer 33

Non surgical procedure by which a special contact lenses are worn at nighttime that slowly reshape the cornea over time to correct myopia

Question 34

What is vitamin A help with in the eye? | 2 other things too not associated with the eye

Answer 34

Necessary for night vision, | wound healing and proper functioning of the immune system.

Question 35

What vitamin helps reduce chronic inflammation and prevents homocysteine in the blood associated with vascular problems of the retina?

Answer 35

Vitamin B complex

Question 36

What vitamin could help reduce the risk of macular degeneration and help in the treatment of uveitis?

Answer 36

B vitamins

Question 37

How does vitamin C help the eye?

Answer 37

Potent antioxidant associated with reduced risk of cataracts

Question 38

How does vitamin D help the eye?

Answer 38

Associated with lower risk of macular degeneration

Question 39

How does vitamin E help the eye?

Answer 39

Associated with lower risk of cataracts

Question 40

How does Omega 3s help the eye?

Answer 40

reduces risk of dry eye

Question 41

What are some photochemical antioxidents?

Answer 41

ginkgo, biloba and bilberry which may provide protection form oxidative stress in the eyes

Question 42

What kind of vitamins should we not take too many of?

Answer 42

fat soluble