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Ocular Disease part 2 > Refractive Surgery > Flashcards

Flashcards in Refractive Surgery Deck (84)
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1

what are 3 types of incisional refractive surgeries?

radial keratotomy (RK), astigmatic keratotomy (AK), relaxing incisions (limbal or peripheral)

2

what are 2 types of thermal refractive surgeries?

laser thermal keratotomy (LTK) and conductive keratoplasty

3

what are 4 types of excimer laser refractive surgeries?

PRK, LASEK, epi-LASIK and LASIK

4

what are 2 types of intraocular surgeries?

phakic IOL's and refractive lens exchange

5

which procedure steepens the cornea and which one flattens the cornea?

incisional = flattens

thermal = steepens

6

what 3 types of cuts will result in more flattening of the cornea?

larger, central and deeper cuts

7

How is radial keratotomy performed and what is it used for?

diamond blade - radial/tangential incisions used for myopia and astigmatism correction

8

what are some con's for radial keratotomy?

fluctuating vision, hyperopic shift over time, and corneal integrity is permanently weakened

9

when is astigmatic keratotomy performed?

during cataract surgery - limbal relaxing incisions or post PKP

10

what results did the PERK study find with radial keratotomy?

43% of eyes experienced a hyperopic shift of 1.00D or more at 10-year follow-up

11

what are intrastromal corneal ring segments made of and why are they used?

made of PMMA implanted in deep stroma to modify corneal curvature (keratoconus)

12

what is the minimum corneal thickness needed for intrastromal corneal ring segments and what are 2 ways to create the pockets?

450 microns (inserted 70-80% corneal thickness) diamond blade pocket creator or femtosecond infrared laser Nd: glass laser

13

what are the two types of intrastromal corneal ring segments and how are they different?

Intacts = hexagonal shape

Ferrara rings = triangular shape

14

how is laser thermal keratoplasty performed?

a series of radial treatment spots are placed outside the visual axis with a Holmium: YAG laser

15

what is laser thermal keratoplasty used for?

causes shrinkage of stromal collagen - steepens cornea to treat hyperopia or presbyopia (effect regresses within several years)

16

what is conductive keratoplasty? what is the advantage over thermal keratoplasty?

a probe applanates the corneal surface - radio waves heat/shrink collagen less risk of irregular astigmatism and regression

17

what type of laser is used in excimer refractive surgery?

argon-fluoride gas laser (emits cool, UV pulses = 193nm and vaporizes tissue at 1/4000mm/pulse)

18

which procedures use excimer lasers? what does it correct?

PRK, LASEK, epi-LASIK and LASIK can correct refractive errors and higher order aberrations

19

what happens in photoreactive keratectomy (PRK)?

corneal epithelium is mechanically removed (blade or ethanol) - excimer laser photoablates Bowman's and anterior stroma - either flattens or steepens cornea

20

what are some indications for PRK?

thin cornea, cost, mild-moderate refractive errors, dry eyes, residual refractive errors (cataract sx, PKP, refractive surgery), and PTK (therapeutic keratomy)

21

what are some primary issues with PRK?

significant post-op discomfort, delayed VA recovery, and development of stromal corneal haze (2-3 weeks)

22

what can you put on the cornea during surgery to reduce the risk of corneal haze?

Mitomycin- C

23

how is LASEK performed?

alcohol is used to loosen the epithelium - cells are harvested - rolled back into place after treatment (similar to PRK but less discomfort and quicker VA recovery)

24

how is epi-LASIK performed?

an epi-microkeratome is used to remove the corneal flap (less discomfort than PRK and more cells survive than with LASEK)

25

how is LASIK performed?

incision is made with either microkeratome (blade) or fematosecond (laser) into corneal stroma creating a flap

NOT surface ablation - goes deep into stroma

26

what layers does the flap consist of in LASIK?

epithelium, bowman's, and anterior stroma (ablation occurs deeper into stroma so there is less wound healing from keratocytes)

27

which method, microkeratome or fematosecond laser creates very high IOP?

microkeratome creates more suction during procedure - very high IOP

28

what does conventional LASIK correct for vs. WaveFront or CustomCornea LASIK?

conventional = myopia, hyperopia, astigmatism custom = also spherical aberrations

29

what are some indications for LASIK?

thicker corneas, keloid formers, higher corrections (>-6D), rapid restoration of vision and almost painless

30

what are some LASIK complications?

flaps (button hole, lost, aborted, epithelial ingrowth, DLK, and striae), corneal ectasia or irregular astigmatism