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Refractive > Photoablation: Complications and Adverse Effects > Flashcards

Photoablation: Complications and Adverse Effects Flashcards

1
Q

General Complications Related to Laser Ablation

A

Overcorrection, Undercorrection, Optical Aberrations, Central Islands, Decentered Ablations, Corticosteroid-Induced Complications, Central Toxic Keratopathy, Infectious Keratitis

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2
Q

Complications Unique to Surface Ablation

A

Persistent Epithelial Defects, Sterile Infiltrates, Corneal Haze

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3
Q

Complications Unique to LASIK

A

Microkeratome Complications, Epithelial Sloughing, Flap Striae, Traumatic Flap Dislocation, Diffuse lamellar keratitis, LASIK infectious keratitis, Pressure-induced stromal keratopathy, Epithelial ingrowth, Interface debris

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4
Q

Complications Related to Femtosecond Laser LASIK Flaps

A

Opaque bubble layer and possible sequelae, Transient light sensitivity, Rainbow glare, Ectasia

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5
Q

When occurs Overcorrection?

A

if significant stromal dehydration develops prior to initiation of the excimer treatment, as more stromal tissue will be ablated per pulse

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6
Q

Overcorrection - more in young or old?

A

in older individuals, as their wound-healing response is less vigorous and their corneas ablate more rapidly

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7
Q

Myopic regression can be induced by

A

abrupt discontinuation of corticosteroids

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8
Q

How to decrease undercorrection?

A

Topical mitomycin C, administered at the time of initial surface ablation, can be used to modulate the response, especially in patients with higher levels of ametropia. Sometimes the regression may be reversed with aggressive administration of topical corticosteroids

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9
Q

Minimal time after which re-treatment can be made?

A

re-treatment generally no sooner than 3 months postoperatively. It is recommended that the surgeon wait at least 6–12 months for the haze to improve spontaneously before repeating surface ablation

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10
Q

When Optical Aberrations are more common?

A

after treatment with smaller ablation zones (<6.0 mm in diameter), after attempted higher spherical and cylindrical correction, and in patients with symptoms prior to refractive surgery. exacerbated in dim-light conditions when mydriasis occurs

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11
Q

Central Island - definition

A

steepening of at least 1.00 D with a diameter of less than 1 mm compared with the paracentral flattened area

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12
Q

Central Island - symptoms

A

visual acuity, monocular diplopia and multiplopia, ghost images, and decreased contrast sensitivity

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13
Q

Central Island - treatment

A

most central islands diminish over time, especially after surface ablation, although resolution may take 6–12 months. Treatment options such as topography-guided ablations may be helpful in treating persistent central islands

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14
Q

Centration is crucial for myopic or hyperopic?

A

Centration is even more crucial for hyperopic than myopic treatments

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15
Q

Decentration - causes

A

patient’s eye slowly begins to drift and loses fixation, if the surgeon initially positions the patient’s head improperly, or if the patient’s eye is not perpendicular to the laser treatment. The incidence of decentration increases with surgeon inexperience, hyperopic ablations, and higher refractive correction, due to longer ablation times

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16
Q

sufficient reproducible accuracy of IOP measurement in eyes after refractive ablation

A

Dynamic contour tonometry

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17
Q

Central Toxic Keratopathy - when

A

opacification. within days after uneventful LASIK or PRK. activated keratocytes without inflammatory cells. result in anterior curvature flattening without alteration of posterior curvature in anterior segment tomography. Resolve with time

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18
Q

Central Toxic Keratopathy - signs

A

opacification, Marked hyperopic shift is often observed and tends to resolve over time.

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19
Q

Infectious Keratitis - more common after LASIK or surface ablation

A

Surface ablation

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20
Q

Infectious Keratitis - patogens

A

gram-positive organisms, including Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), Streptococcus pneumoniae, and Streptococcus viridans

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21
Q

What to do it Infectious Keratitis following LASIK?

A

lift the flap, scrape the stromal bed for culture and sensitivity testing, and irrigate with antibiotics prior to flap repositioning. If there is lack of clinical progress, additional scrapings and irrigation may be necessary, the flap may be amputated, and the antibiotic regimen may be altered

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22
Q

Persistent epithelial defect increases the risk of

A

corneal haze, irregular astigmatism, refractive instability, delayed recovery of vision, and infectious keratitis

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23
Q

Sterile Infiltrates - causes

A

The use of bandage contact lenses, using topical NSAIDs for longer than 24 hours without concomitant topical corticosteroids

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24
Q

Corneal Haze - when appears and disappears?

A

typically appears several weeks after surface ablation, peaks in intensity at 1–2 months, and gradually diminishes or disappears over the following 6–12 months. Late-onset corneal haze may occur several months or even a year or more postoperatively

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25
Q

Persistent severe haze - causes

A

greater amounts of correction or smaller ablation zones

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26
Q

Persistent Corneal Haze - treatment + prevention of recurrence

A

superficial keratectomy or phototherapeutic keratectomy (PTK). topical mitomycin C (0.02%), with PTK or debridement, may be used to prevent recurrence of subepithelial fibrosis.

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27
Q

Corneal Haze - refraction

A

refraction is often inaccurate, typically with an overestimation of the amount of myopia

28
Q

Microkeratome Complications - causes

A

Defects in the blade, poor suction (ssanie), or uneven (nierównomierny) progression of the microkeratome

29
Q

thin or buttonhole flap is created - what to do?

A

flap should be replaced and the ablation should not be performed. The flap is allowed to heal before another refractive procedure is attempted, typically 3–6 months later. bandage contact lens is applied to stabilize the flap. Although a new flap can usually be cut safely using a deeper cut after at least 3 months of healing, most surgeons prefer to use a surface ablation technique

30
Q

Risk factor for free cap

A

A flat corneal curvature (<40.00 D) is a risk factor for creating a free cap because the flap diameter is often smaller than average in flat corneas

31
Q

free cap is created instead of a hinged (zawieszony na zawiasach) flap - what to do?

A

if the stromal bed is large enough to accommodate the laser treatment, the corneal cap is placed in a moist chamber while the ablation is performed. It is important to replace the cap with the epithelial side up and to position it properly on a dried stromal bed, using the previously placed radial marks. A bandage contact lens can help protect the cap

32
Q

Epithelial Sloughing - risk factors

A

EBMD, age, in bilateral LASIK procedures with mechanical microkeratomes, the second eye has a greater likelihood of sustaining an epithelial defect (57%) if an intraoperative epithelial defect developed in the first eye

33
Q

Techniques suggested to decrease the rate of epithelial defects/Sloughing

A

limiting medications to avoid toxicity, using chilled proparacaine, minimizing use of topical anesthetic, using nonpreserved drops until just before performing the skin prep or starting the procedure, having patients keep their eyes closed after topical anesthetic is administered, frequent use of corneal lubricating drops, meticulous microkeratome maintenance, and shutting off suction on the microkeratome reverse pass. Femtosecond - reduced incidence.

34
Q

Epithelial defects - complications

A

increased incidence of postoperative diffuse lamellar keratitis, infectious keratitis, flap striae, and epithelial ingrowth

35
Q

Flap Striae - when do they occur

A

most (56%) flap folds are noted on the first postoperative day, and 95% are noted within the first week

36
Q

Risk factors of Flap Striae

A

excessive irrigation under the flap during LASIK, thin flaps, and deep ablations with mismatch of the flap to the new bed

37
Q

flap slippage

A

Folds that are parallel and emanate from the flap hinge grouped in the same direction indicate flap slippage, which requires prompt intervention. Topography not useful

38
Q

Macrostriae

A

full-thickness, undulating (falisty) stromal folds. occur because of initial flap malposition or postoperative flap slippage. Macrostriae may occur as patients attempt to squeeze their eyelids shut when the speculum and drape are removed.

39
Q

Macrostriae - what to do

A

apply momentary medical grade compressed air and instruct the patient to not overly squeeze the eyelids upon removal of the speculum. A protective plastic shield is often used for the first 24 hours to discourage the patient from touching the eyelids and inadvertently disrupting the flap.

40
Q

Flap dislocation - how to see

A

Careful examination will disclose a wider gutter on the side where the folds are most prominent

41
Q

Flap dislocation - what to do

A

Flap slippage should be rectified (sprostowany) as soon as it is recognized because the folds rapidly become fixed. Under the operating microscope or at the slit lamp, an eyelid speculum is placed, the flap is lifted and repositioned, copious irrigation with sterile balanced salt solution is used in the interface, and the flap is repeatedly stroked perpendicular to the fold until the striae resolve or improve.

42
Q

What to do in cases of intractable macrostriae

A

a tight 360° antitorque running suture or multiple interrupted sutures using 10-0 nylon may be placed and retained for several weeks, but irregular astigmatism may still be present after suture removal

43
Q

Microstriae - what are they and how do they look like?

A

fine, hairlike optical irregularities that are best viewed on red reflex illumination or by light reflected off the iris. They are very small folds in the Bowman layer

44
Q

Microstriae - how to detect them?

A

hairlike optical irregularities that are best viewed on red reflex illumination or by light reflected off the iris. Computer topographic color maps do not usually show these subtle irregularities. However, disruption of the surface contour may result in irregularity of the Placido disk image. In addition, application of dilute fluorescein often reveals so-called negative staining

45
Q

Diffuse lamellar keratitis - factors

A

accumulation of WHITE blood cells in interface under the flap. association with EPITHELIAL DEFECTS. corneal ABRASIONS or infectious KERATITIS. FOREIGN material on the surface of the microkeratome blade or motor, trapped MEIBOMIAN gland SECRETIONS, POVIDONE-IODINE solution (from the preoperative skin preparation), marking INK, SUBSTANCES produced by LASER ABLATION, contamination of the sterilizer with gram-negative endotoxin, and RED BLOOD cells in the interface

46
Q

Diffuse lamellar keratitis - treatment

A

stages 1 and 2 usually respond to frequent topical corticosteroid application, stages 3 and 4 usually require lifting the flap and irrigating, followed by intensive topical corticosteroid treatment. In cases of suspected DLK not responsive to corticosteroids within 7–10 days of initiation, the diagnosis should be reconsidered, as infectious keratitis or pressure-induced stromal keratopathy (PISK) can mimic DLK and require corticosteroid cessation.

47
Q

DLK - when and characteristic feature

A

within 24 hours, most intense at the periphery and diminishing toward the center of the cornea. localized and confined to the area of the flap interface; it does not extend far beyond the edge of the flap

48
Q

post-LASIK infectious keratitis - when and how

A

begins 2 or 3 days after surgery and involves a more focal inflammatory reaction that is not confined to the lamellar interface

49
Q

post-LASIK infectious keratitis - patogens

A

gram-positive organisms, followed in frequency by those caused by atypical mycobacteria

50
Q

Pressure-induced stromal keratopathy - what is ti and what is the cause

A

diffuse stromal and interface opacity, result of elevated IOP, associated with prolonged corticosteroid treatment

51
Q

Pressure-induced stromal keratopathy - when

A

after 10 days to 2 weeks

52
Q

differentiators between DLK and PISK

A

with DLK, the onset is earlier and the IOP is not elevated. IOP should be measured both centrally and peripherally in suspected cases, possibly with a pneumotonometer or Tono-Pen, because applanation pressure may be falsely lowered centrally in PISK by fluid accumulation in the lamellar interface

53
Q

Epithelial ingrowth - treatment

A

There is no need to treat isolated nests of epithelial cells in the peripheral lamellar interface that are not advancing and are not affecting vision. However, if the epithelium is advancing toward the visual axis, is associated with decreased vision from irregular astigmatism, or triggers overlying flap melting, it should be removed by lifting the flap, scraping the epithelium from both the underside of the flap and the stromal bed, and then repositioning the flap. Recurrent epithelial ingrowth can be treated with repeated lifting and scraping, with or without flap suturing or using fibrin glue at the flap edge. Some surgeons treat the undersurface of the flap with absolute alcohol to identify and treat any residual epithelium.

54
Q

Interface debris - what can be tolerated

A

Small amounts of lint (wata), nondescript (nieokreślony) particles, or tiny metal particles from stainless steel surgical instruments are usually well tolerated. A small amount of blood that may have oozed into the interface from transected peripheral vessels may also be tolerated and typically resolves spontaneously with time

55
Q

Interface debris - what cannot be tolerated

A

significant amount of blood usually elicits an inflammatory cell response and should be irrigated from the interface at the time of the LASIK procedure

56
Q

Opaque bubble layer - composition

A

carbon dioxide and water

57
Q

Opaque bubble layer - why not nice

A

Laser tracking systems can be significantly impaired by the OBL. Epithelial gas breakthrough

58
Q

Opaque bubble layer - what to do

A

Time and/or mechanical massage will allow for OBL to dissipate

59
Q

Transient light sensitivity - when and what is it

A

Several weeks to months after LASIK with femtosecond laser flaps, some patients experience acute onset of pain and light sensitivity in an otherwise white and quiet eye with excellent uncorrected visual acuity

60
Q

Transient light sensitivity - treatment

A

topical corticosteroids (eg, prednisolone acetate, 1%, every 2 hours) and topical cyclosporine A, titrated to the clinical condition. Almost all cases respond to treatment and resolve in weeks to months

61
Q

Rainbow glare - what is it

A

optical adverse effect of treatment with the femtosecond laser, is described as bands of color around white lights at night

62
Q

Ectasia - risk factors

A

predisposed to developing corneal ectatic disorders or have a significantly reduced postablation residual stromal bed (RSB), preoperative topographic abnormalities, younger patient age, thinner corneas, higher myopic corrections, and patients who have undergone several laser ablations

63
Q

Ectasia - more often after surface ablations or LASIK?

A

more frequently after LASIK than after surface ablation

64
Q

Ectasia - treatment

A

corneal crosslinking, rigid gas-permeable or hybrid contact lens wear, symmetric or asymmetric intrastromal ring segments

65
Q

most common and anticipated complication of refractive surgery

A

Dry eye after LASIK

66
Q

anesthesia after flap

A

lasting 3–6 months and may less frequently persist for years. As a result, many patients develop keratopathy, decreased tear production, and related symptoms as a result of the neurotrophic state of their cornea

Refractive (12 decks)

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