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BOARDS2: Cornea/lens/prepostop > Refractive Surgery > Flashcards

Refractive Surgery Flashcards

1
Q

Refractive surgery after presbyopia

A

Monovision
Cornea inlay (pinhole)
CLEX

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2
Q

Refractive surgery before presbyopia

A

LASIK
SMILE
Phakic IOL
PRK

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3
Q

Relative contraindications for refractive surgery

A 
Large pupils 
DM
Lattice degeneration
DED
Blepharitis 
Chronic eye rubbing 
Other ocular surface disease 
Uncontrolled POAG
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4
Q

Large pupils and refractive surgery

A

May result in increased aberrations and halos driving at night.
Treatment zone needs to be larger
Wavefront guided best for them

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5
Q

DM and refractive surgery

A

Uncontrolled BS may result in fluctuations in refractive error.
Poor wound healing

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6
Q

Lattice and refractive surgery

A

May increase the risk of retinal breaks during or after refractive surgery.

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7
Q

DED and refractive error

A

May be exacerbated by refractive surgery as the corneal nerves are temporarily damaged during the procedure.
Patients may experience reduced vision with dry eyes
Must use aggressive lubrication with AT post op

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8
Q

Absolute contraindications for refractive surgery

A

Pts under 18
Unstable refractive error (>0.50D change) within the last year
Refractive error outside of the treatment zone
Inadequate CCT (minimum of 250um residual stroma for LASIK and 400um for PRK
Unrealistic expectations
Pregnancy
Kones, active HSK/HZK or CL induced warpage
Connective tissue disease, collagen vascular disease, immunocompromised

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9
Q

What is the minimum stromal thickness needed after LASIK

A

250um

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10
Q

How thick is the flap in LASIK

A

160-200um (microkeratome)

120um (laser)

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11
Q

What is the ablation depth in LASIK

A

15um/diopter

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12
Q

Radial keratotomy

A

No longer performed
Involves making radial incision in the corneal stroma with a diamond knife in order to flatten the cornea and reduce myopia. The precision of the final refractive error was difficult to control and was suboptimal; it was common for patients to end up with a hyperopic refractive error

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13
Q

PRK

A

The corneal epithelium is removed completely and an excimer laser is used to directly ablate the anterior stroma to reshape the corneal tissue and correct form myopia, hyperopia, and/or astigmatism

The laser essentially creates a corneal abrasion, resulting in extremely poor vision in the immediate post op period, a slo recovery (the entire corneal epi must regrow) and more post op discomfort compared to LASIK. Pts monitored closely and are treated with topical ophthalmic steroids that are slowly tapered over the course of several weeks,

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14
Q

Treatment range for PRK

A

-8 to +4D

Up to 4D cyl

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15
Q

What refractive surgery is best for thin corneas?

A

PRK

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16
Q

Advantages of PRK over LASIK

A 
No flap complications 
Less risk of corneal infection
Requires less corneal thickness 
Less post op higher order aberrations 
Decreased risk of post op DED
Less expensive
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17
Q

LASIK

A

First performed in 1990, has became the most popular refractive surgery. During the procedure, a corneal epithelial flap is created with a microkeratome, an excimer laser is used to ablate the underlying anterior corneal stroma, and the epithelial flap is then folded back in place. LASIK can be used to correct hyperopia, myopia, and astigmatism, although the treatment ranges are larger for myopia

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18
Q

Treatment ranges for LASIK

A

-10 to +4D

Up to 5D cy

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19
Q

What is a good option for refractive surgery in patients who’s refractive error exceeds the treatment range for LASIK?

A

(-10D to +4)

CLEX

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20
Q

Healing in LASIK

A

Heal faster, less pain, and have less post op corneal haze compared to PRK

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21
Q

Intralasik

A

The same procedure as LASIK except the corneal epithelial flap is made with a laser instead of a microkeratome

The corneal flap created by a femtosecond laser is thinner, leaving more tissue behind for ablation; it is also associated with decreased post op dryness

Intralasik removes the risk of a mechanical malfunction with the microkeratome, resulting in a thinner, more uniform flap.

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22
Q

LASEK or E-LASIK

A

The same procedure as LASIK, but the corneal epithelial flap is created using dilute alcohol instead of a microkeratome. Similar to intralasik, the procedure avoids complications related to malfunction of the microkeratome

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23
Q

Epi LASIK

A

The same procedure as LASIK but with a blunt plastic blade used to create the corneal epithelial flap rather than a microkeratome

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24
Q

INTACs

A

PMMA rings are inserted in the peripheral corneal stroma in order to flatten the cornea (shortens the corneal arc length). ICR is approved for the treatment of keratoconnus (the rings help stabilize and support the base of the Kone, allowing for an improved RGP CL fit

Reversible, the rings can be removed or exchanged

25
Q

Treatment range for INTACs

A

-0.75D to -3D and less than 1D of cyl

Does not treat hyperopia

26
Q

CLEX

A

This procedure involves removal of the natural, clear lens in exchange for an IOL that will alter the refractive power of the eye, it is essentially cataract surgery without the cataract.

An option for patients whose corneal thickness is too thin for LASIK

The patient will NOT have accommodation after surgery, unless the multifocal IOL or an accommodating IOL is unplanned (not an ideal surgery for pre presbyopic patients)

Larger treatment range

27
Q

Phakic IOL (implantable CL)

A

An IOL is implanted into a phakic eye, this allows for alteration of the eyes refractive power, without removing the patients ability to accommodate. The implanted IOL can be placed in the AC or PC, a surgical PI is rewuire to prevent angle closure

28
Q

Astigmatic keratectomy

A

Circumferential corneal incisions are made with a diamond blade in order ro relax the cornea in the steepest meridian to minimize corneal astigmatism. Incisions are usually made parallels to the limbus to correct moderate to high astigmatism

29
Q

Conductive keratoplasty

A

Radio frequency energy is applied to the peripheral cornea, causing the collagen fibers to shrink and the central cornea to steepen. This is no longer a popular procedure because patietns have residual large white spots in the peripheral cornea

30
Q

Treatment rage for CK

A

+0.75 to +3.00

May also be used to treat <0.75 residual astigmatism after previous intraocular surgeries

Regression is expected to occur after 2-3 years. The surgery can be repeated

31
Q

Wavefront guided ablation

A

Custom corneal surgery that reduces higher order aberrations in addition to correcting the refractive error. It can be performed with LASIK and PRK, and theoretically results in better quality vision with improved contrast, improved acuity, and decreased glare

32
Q

What is DLK

A

Rare, inflammatory, non infectious reaction at the lamellar interface (between the corneal flap and the corneal stroma). It most commonly present within 2-3 days after surgery. Patients often complain of blurred vision, photophobia, pain, and FB sensation

33
Q

DLK etiology

A

Poorly understood. Thought to occur in response to toxins during surgery. It is less common with disposable microkeratome

34
Q

DLK appearance

A

Fine, granular, sand-like infiltrates. It may lead to severe vision loss secondary to corneal scarring and/or corneal melting if not properly treated

35
Q

Treatment for DLK

A

Mild: pred acetate Q1h -or- durezol q2h

Severe: oral steroids and/or flap is lifted and irrigated

36
Q

Pain post op

A

More prevalent in the first 24 hours after surgery especially in PRK. It is secondary to the corneal wound, or flap complications in LASIK. High Dk SCL can be used as BCL to improve healing and comfort

37
Q

What are the two most common complications post op after refractive surgery

A

Dry eye

Residual refractive error

38
Q

Dry eye disease post op refractive surgery

A

The most common side effect (up to 33%); typically removes after 1-2 months. DED is worse with decreased corneal sensitivity (although patients may not have severe symptoms). Treatment involves aggressive lubrication (AT, gels, and/or ointments) and/or punctal plugs

39
Q

Glare and haloes post refractive surgery

A

More in smaller ablation zones, larger pupils, monovision correction, and higher order aberrations

40
Q

Refractive surgery complications

A 
DLK
DED
Glare and halos 
Reduced low contrast VA
Infection
Residual refractive error 
Irregualr astigmatism/aberrations 
Corneal haze 
Corneal ectasia 
Flap complications 
Epithelial ingrowths
41
Q

Infection after refractive surgery

A

Most commonly occurs at post opt days 1-2. The risk of infection with PRK is 1/1000-1/3500, and with LASIK is 1/5000

  • most commonly gram + mycobacterium
  • TX is lifting the flap and irrigating with ABX
  • inadequate or delayed treatment can result in corneal melting, irregular astigmatism, and/or scarring
42
Q

Residual refractive error after refractive surgery

A

Over or under correcting the refractive error and regression are more common in high refractive errors (>-8D). Pts can be fit with SCLs or with RGPs. A reverse geometry design lens may be most appropriate as the periphery of the cornea is steep and the center of the cornea is flat. Eventually an enhancent procedure can be considered

43
Q

Corneal haze after refractive surgery

A

Will present for several weeks following PRK as the corneal epithelium heals; rare following LASIK. The prevalence of long term corneal haze is 0.1% following LASIK and 1% following PRK in patietns with pre op refractive errors <6D; the risk increases for patietns with higher refractive errors.

44
Q

Treatment of corneal haze

A

Topical steroids

45
Q

Corneal ectasia after refractive surgery

A

Characterized by an abnormal bulging forward of a thin cornea; it is more likely to occur in high myopes (more cornea is ablated), or in patients with undetected keraconus, or forme fruste keratoconnus.

Treatment: RGPs, INTACs, or PK; there are also studies investigating riboflavin/UV-A light to increase corneal cross linking

46
Q

Microkeratome complications

A

Flap complications

Epithelial ingrowths

47
Q

What are the flap complications in LASIK

A 
Free caps 
Button holes 
Flap folds
Irregular flaps 
Subluxation 
Corneal perforation
48
Q

Free caps

A

More commonly occur with very flat corneas; the inadequate amount of cornea in the ring causes the microkeratome blade to cut the hinge of the flap

49
Q

Button holes

A

Cap perforation, a hole in the flap
More commonly occur in very steep corneas or in deep set eyes. The steep cornea can buckle in the ring, resulting in a hole in the flap with the pass of the keratome

50
Q

What type of flap folds are there

A

Macrostriae and microstriae

51
Q

When do flap folds occur

A

During the first day (56% of cases) or within the first week (95% cases)

52
Q

Macrostriae

A

Full thickness with undulating, parallel, stromal folds; they are commonly due to slippage or malpositioning during surgery.

Treatemtn is lifting and repositioning

53
Q

Microstriae

A

Fine, multi-directional folds in bowmans membrane that result in optical irregularities; they typically resolve on their own, and are only treated if they are visually significant

54
Q

Flap dislodgement after refractive surgery

A

More commonly occurs with microkeratome flaps compared to femtosecond laser flaps; it usually results from the patient accidentally touching thei eye or the eyelid during the immediate post op periods. They can be repositioned

55
Q

Epithelial ingrowths

A

Occur at 1 month
Less than 3% of cases
Appears as milky white deposits at the interface.
Treatment is indicated if the condition obstructs the visual axis and is progressive, or induces corneal astigmatism; treatment involves lifting the flap and scraping the epithelial cells away

56
Q

Wait time for enhancement on refractive surgery

A

Although enhancement procedures can be performed as early as 3m post LASIK and PRK, a 6 month wait is preferred to allow for stabilization of the refractive error. Patients can be corrected with glasses or CL until an enhancement procedure is indicated. Enhancement procedures after LASIK involve lifting the flap and re-ablation the cornea. Enhancement procedures after PRK can be performed over the top of the cornea

57
Q

Recommended retreatment criteria

A
  • refractive error >0,75D from the target refraction in an unhappy patient
  • uncorrected VA <20/30 in the distance eye in an unhappy patient
  • astigmatism >0.75D causing symptoms (ghosting)
58
Q

When is refractive surgery considered a success

A

If the patient achieves 20/40 VA or better. Appx 90-99% of patients with low refractive errors achieve this goal, and 75% of patients achieve 20/25 orbetter

59
Q

IOP and refractive surgery

A

Thinner cornea, gives false low reading

BOARDS2: Cornea/lens/prepostop (5 decks)

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