Chua 7

Question 1

What is monovision

Answer 1

One eye myopic, one eye emmetropic

One eye for distance, one for near

For presbyopic patients

Acuity and stereopsis reduced

Question 2

What is PRK

Answer 2

Photorefractive Keratectomy

Uses exciser UV laser

BReaks molecular bonds
Reduces myopia by decreasing corneal curvature

More effective for low myopia

Question 3

LASIK

Answer 3

Microkeratone used to create a flap with hinge

Excimer laser used to treat stroma under flap

Question 4

What are contraindications for refractive surgery?

Answer 4

Age less than 21
KEratoconus
Recently worn contact lenses

Question 5

LASIK vs PRK

Answer 5

LEss painful as no conrea exposed

Can treat higher myopia

Less scarring

Less myopic regression

HIgher complication risk

Question 6

What are side effects of LASIK

Answer 6

Reduced corneal sensation
Tear film instability
Glare from scarring
Biometry can be inaccurate
May give risk to low IOP with Goldmann due to thinner cornea

Question 7

What is radial keratotomy

Answer 7

Cutting cornea radially for flattening of cornea

Used to treate myopia and astigmatism

Refractive power of cornea is reduced

Increased risk of rupture in blunt trauma

Question 8

What increases effect of radial keratotomy

Answer 8

80-90% cut deeper
Longer
Central zone smaller

Less predictable than LASIK
Takes longer to stabilise

Question 9

What are advantages of temporal corneal incision

Answer 9

Easier access to eye
Central cornea is further from temporal limbus so induced astigmatism is less

Question 10

Where is incision placed in astigmatic keratotomy?

Answer 10

Perpendicular to steepest meridian

Causes coupling - 90 degree parallel meridian gets steepended

Nearer the incision to centre the greater the effect howeer risk of glare and irregular astigmatism if too close to optical zone

Question 11

What happens when tight suture is placed radially in cornea

Answer 11

Meridian suture is in is steepened
Meridian perpendicular is flattened

Deeper suture/near centre of cornea has greater effect

Question 12

What is intrastromal corneal rign used for?

Answer 12

Flatten cornea and reduce refractive power

Treat myopia

Made of PMMA

Can be reversed

Question 13

What is epikeratophakia?

Answer 13

PRe-shaped donor conrea stroma to surface of host cornea

Question 14

What is keratomileusis

Answer 14

Use of microkeratome to remove a lamella of anteiror corneal stroma which is reshaped and replaced

Question 15

What is keratophakia

Answer 15

Keratome tolife lameela of anteiror stroma replaced over shaped lenticule of donor conreaW

Question 16

What is lamellar and penetrating keratoplasty

Answer 16

Partial thickness and full thickness corneal grafts

Question 17

What is the effect of scleral buckle?q

Answer 17

Increases length of eye - myopic shift

Can induce astigmatism if placed asymmetrically

Question 18

What causes cataract in macular hole surgery

Answer 18

Gas fill

Question 19

What happens with gas fill in phakic eye

Answer 19

Increases the refractive power of back surface of phakic eye and causes myopic shift

Question 20

What happens with gass fill in aphakic eye

Answer 20

Air increases diverging power of back surface of cornea and causes a hypermetropic shift

Question 21

What does silicone oil do to refraction of phakic eye

Answer 21

Higher refractive index than lens causing posterior surface of lens to become diverging causing hypermetropic shift

Question 22

What does silicone oil do to refraction of aphakic eye

Answer 22

Silicone oil acts as converging interface and causes myopic shift

Question 23

What effet does silicone oil have on US

Answer 23

US slower through silicone oil - gives erroneously long axial length

Question 24

What are complications of silicone oil

Answer 24

Band keratopathy
Glaucoma