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Ocular Disease part 2 > Refractive Surgery > Flashcards

Refractive Surgery Flashcards

1
Q

what are 3 types of incisional refractive surgeries?

A

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

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2
Q

what are 2 types of thermal refractive surgeries?

A

laser thermal keratotomy (LTK) and conductive keratoplasty

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3
Q

what are 4 types of excimer laser refractive surgeries?

A

PRK, LASEK, epi-LASIK and LASIK

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4
Q

what are 2 types of intraocular surgeries?

A

phakic IOL’s and refractive lens exchange

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5
Q

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

A

incisional = flattens

thermal = steepens

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6
Q

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

A

larger, central and deeper cuts

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7
Q

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

A

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

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8
Q

what are some con’s for radial keratotomy?

A

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

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9
Q

when is astigmatic keratotomy performed?

A

during cataract surgery - limbal relaxing incisions or post PKP

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10
Q

what results did the PERK study find with radial keratotomy?

A

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

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11
Q

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

A

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

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12
Q

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

A

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

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13
Q

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

A

Intacts = hexagonal shape

Ferrara rings = triangular shape

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14
Q

how is laser thermal keratoplasty performed?

A

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

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15
Q

what is laser thermal keratoplasty used for?

A

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

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16
Q

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

A

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

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17
Q

what type of laser is used in excimer refractive surgery?

A

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

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18
Q

which procedures use excimer lasers? what does it correct?

A

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

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19
Q

what happens in photoreactive keratectomy (PRK)?

A

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

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20
Q

what are some indications for PRK?

A

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

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21
Q

what are some primary issues with PRK?

A

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

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22
Q

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

A

Mitomycin- C

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23
Q

how is LASEK performed?

A

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)

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24
Q

how is epi-LASIK performed?

A

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

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25
Q

how is LASIK performed?

A

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

NOT surface ablation - goes deep into stroma

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26
Q

what layers does the flap consist of in LASIK?

A

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

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27
Q

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

A

microkeratome creates more suction during procedure - very high IOP

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28
Q

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

A

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

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29
Q

what are some indications for LASIK?

A

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

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30
Q

what are some LASIK complications?

A

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

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31
Q

how can you help prevent corneal ectasia during LASIK?

A

keep a residual corneal thickness of 275 microns (250-300)

only perfom up to -10.00D myopia

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32
Q

what are some indications for phakic IOL’s?

A

high refractive errors (20D myopia/hyperopia or 7.5D astigmatism) and thin corneas

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33
Q

what are some general risks to phakic IOL’s?

A

endophthalmitis, residual refractive error, glare and glaucoma/cataract

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34
Q

which phakic IOL can cause glaucoma and which can cause a cataract?

A

anterior chamber lens = glaucoma

posterior chamber lens = cataract

35
Q

what is the minimum anterior chamber depth for an anterior chamber phakic IOL?

A

minimum 3.2mm (problem for hyperopes - smaller AC depth)

36
Q

what type of patients get refractive lens exchange?

A

for patients who are not good candidates for other refractive surgeries (similar to cataract removal)

37
Q

what are 3 considerations for refractive lens exchange?

A

PVD/retinal detachment, presbyopia, and stability of refractive error

38
Q

what percentage of patients had visual symptoms that were extrememly bothersome in the LQOLCP study?

A

4% of subjects without correction at 3 months

39
Q

what percentage of patients had new dry eye symptoms in the LQOLCP study?

A

30%

40
Q

what are some medical history/conditions that would not be good for refractive surgery?

A

autoimmune/collagen vascular disease (lupus, rosacea, sjogren’s, ehler’sdanlos, RA), diabetes, pregnancy, immunodeficiency, personality disorder and medications (Amiodarone HCL, Isotretinoin - Accutane)

41
Q

what are some ocular history’s that would not be good for refractive surgery?

A

corneal ulcers, viral infections - post tx, steroid responder, lagophthalmos, floppy lid syndrome and eye dominance

42
Q

why do you need to know the patient’s CL history before refractive surgery?

A

need to know if they like the CL or if they are non-compliant = good candidate

if they do not like monovision or multifocals = bad candidate dry eyes = bad candidate

43
Q

why do you perform a cycloplegic refraction prior to refractive surgery?

A

you do not want to overestimate their Rx

44
Q

what are some risk factors for dry eye history?

A

females, over 50 y/o, Asians, higher myopes and hyperopes, medications and cigarette smoking

45
Q

what are the risk factors for ectasia according to the Randleman study (in order)?

A

abnormal topography, residual stromal bed thickness, age, pre-op corneal thickness and refractive error

46
Q

what are the absolute surgical contraindications?

A

under 18 y/o, pregnant or nursing, dx with collagen vascular disease, autoimmune or immunodeficiency, taking accutane and/or amiodarone and keratoconus

47
Q

what are the relative surgical contraindications?

A

diabetes, connective tissue/atopic disease, immunocompromise status, herpes simplex/zoster, keratitis sicca and glaucoma

48
Q

what are the pre-op medications/treatments?

A

omega 3, doxycycline, restais, antibiotics, artificial tears, lid massage, plugs

49
Q

what are some potential complications with the laser or microkeratome?

A

*worst complications may be postponed irregular flap healing

can cause corneal distortion perforation of cornea could occur with devastating consequences

50
Q

what are some potential complications of refractive surgery?

A

mild or severe infection is possible, could develop keratoconus, increased light sensitivity/glare, dry eyes, over/under correction, fragile cornea, pain/FB sensation and vision could regress over time

51
Q

what are the day 1 pot-op clinical tests?

A

history, UCVA, slit lamp, review drops and RTC in 1 week

52
Q

what are some clinical findings at the 1 day post-op appointment that would indicate they return to the surgical center?

A

dislodged flap, flap striae, infections

53
Q

what clinical tests are different at the 1 week appointment?

A

do a dry Rx BCVA, use NaFl with slit lamp and RTC in 3 weeks

54
Q

what clinical findings at the 1 week appointment would indicate the patient to return to the surgical center?

A

infection and loss of BCVA

55
Q

what clinical tests are performed at the 1 month post-op exam?

A

history, UCVA, dry refraction, slit lamp with NaFl, and RTC in 8 weeks

56
Q

what are the symptoms of post-LASIK dry eye?

A

visual fluctuation, dryness, irritation, and pain (refract with little hyperopia and WTR cylinder)

57
Q

can dry eyes cause a regression towards the pre-LASIK refractive state?

A

several studies show that regression following hyperopic and myopic LASIK is correlated with dry eyes

58
Q

how is post LASIK ectasia diagnosed?

A

delayed acquired astigmatism, loss of BCVA, elevation topography and aberromtey (elevated vertical cornea)

59
Q

what are the treatments for ectasia?

A

specs, soft CL, RGP CL, hybrid CL, Intacts, collagen cross linking, keratoplasty (PKP)

60
Q

which LASIK treatment has been shown to cause more dry eyes?

A

microkeratome (had 46% corneal staining vs. femto 8%)

61
Q

what happens to contrast sensitivity with LASIK?

A

decreases initially - by 3 months patients regain normal cycles/degree

62
Q

what did the cyclosporin and corneal sensitivity study find?

A

Restasis helps dryness and makes a better corneal bed for the healing process (most patients benefit)

63
Q

what medications are patients on post LASIK?

A

antibiotic 1 week, Pred Forte QID 1 week, Restasis BID 1 month, AT’s QID 1 month, omega 3, punctal plugs

64
Q

what is diffuse lamellar keratitis (sands of the Sahara)?

A

LASIK complication - interface inflammation, WBCs (neutrophils) but no infection noticed first 12-72 hours

65
Q

will patients have symptoms if they have grade 1 DLK?

A

usually no - treat before they have symptoms = use steroid more frequently (q1h for 24 hours) will see at first or 1 week visit

66
Q

what are the signs of diffuse lamellar keratitis?

A

no conjunctival injection, no AC inflammation, no NaFl stain

67
Q

what causes diffuse lamellar keratitis?

A

no precise etiology - suspected autoimmune response

68
Q

what happens if you do not treat DLK?

A

if not treated aggressively it can cause a stromal interface melt - neutrophils release proteolytic enzymes that digest or melt the stroma

69
Q

what happens in grade 2 DLK?

A

may have mild ocular discomfort, BCVA is reduced by 1-2 lines, hyperopic shift is seen and the risk of corneal melt is higher

70
Q

what happens in grade 3 DLK?

A

(should never get to this state) - patients complain of extremely blurred vision and glare (BCVA is drastically reduced), large hyperopic/astigmatic shift, dense infiltration and can resemble severe PRK haze

71
Q

how do striae stain?

A

fluorescein makes it easier to see as valley’s and mountains with negative staining

72
Q

when is striae after LASIK a concern?

A

only is there is loss of BCVA or subjective quality of vision, glare or halos

73
Q

what are the treatments for striae?

A

mechanical problem = caro ball smoothing, flap lift and stretch, flap lift with epithelial debridement/hypotonic saline, flap suture and therapeutic PTK

74
Q

why would fematosecond provide less epi-ingrowth than blades (microkeratome)?

A

blades all have tapered or gradual entry into cornea -all FSL had either a 65 or 70 degree side cut from the lamellar dissection to the anterior surface of the cornea

75
Q

what is the most common infection in laser vision correction?

A

MRSA

76
Q

when will patients complain of a MRSA infection?

A

day 1 looks normal and then the patient calls in pain between 2-4 days

77
Q

what are some characteristics of MRSA infections after LASIK?

A

slow to heal, significant pain, and non-healing peripheral infiltrates

78
Q

which patients are more at risk of developing MRSA?

A

health care workers, known carriers of MRSA, and patients with blepharitis

79
Q

what do you give patients pre-op for prophylaxis for MRSA?

A

aggressive treatment for blepharitis to reduce lid colonization by staphylococcus, hot compress, lid hygiene, regular Zymar or Vigamox QID for 5-7 days or Tobradex ST

80
Q

what can you give to patients during the LASIK procedure to reduce MRSA?

A

regular Betadine lid prep

81
Q

what can you give patients post-op for MRSA prophylaxis?

A

regular Zymar or Vigamox QID, add polytrim or Neosporin QID and consider Tobradex ST

82
Q

what is the treatment protocol for corneal infiltrates post refractive surgery?

A

Assume MRSA infection is resistant to Zymar/Vigamox until culture, lift flap (LASIK) and culture (PRK, LASIK) Irrigate Vancomycin 25mg/ml under flap increase Zymar/Vigamox q1h add vancomycin 25mg/ml 130min (or bacitracin/polytrim/neosporin) follow up every 12-24 hours

83
Q

what complication is seen in this photo?

A

epithelial ingrowth (starts in periphery vs. DLK which starts centrally)

progressive

84
Q

what complication is seen in this photo?

A

significant epithelial ingrowth

Ocular Disease part 2 (7 decks)

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