Lasers, Vitreoretinal Surgery, and Injections

Question 1

effect of photocoagulation on tissues

Answer 1

thermal damage via protein denaturation and coagulative necrosis

Question 2

color wavelength of choice for retinal vascular lesions and CNV

Answer 2

green (514 nm)

Question 3

color wavelength best for penetrating vitreous heme? for nuclear sclerotic cataracts?

Answer 3

both red (647 nm)

Question 4

which color laser causes deeper burns and more discomfort

Answer 4

red (647 nm)

Question 5

absorption curve of hemoglobin?

Answer 5

two peak: blue, and then green-yellow. minimal absorption of red

Question 6

absorption curve of xanthophyl?

Answer 6

one peak at blue. minimal absorption of other wavelengths

Question 7

which laser color has minimal scatter through NSC, low xanthophyl absorption, and little potential for photochemical damaged

Answer 7

yellow (570)

Question 8

contrast negative-power planoconcave v high plus-power lenses for laser photocoagulation

Answer 8

• negative-power planoconcave: upright image, good resolution, narrow view. favored for macular treatments
• high plus-power lenses : inverted image, worse resolution, wider view. favored for PRP

Question 9

guidelines for macular laser treatment

Answer 9

not within 500 um of fovea center. small spot size, (100-200 um) short duration (

Question 10

PRP laser spot size and duration

Answer 10

200-500 um, 0.05 - 0.2 s

Question 11

three laser parameters that increase risk of Bruch’s membrane rupture

Answer 11

small spot size, high power, short duration

Question 12

next step when subretinal heme develops during laser photocoagulation of CNV?

Answer 12

increase digital pressure on contact lens and continue lasering

Question 13

what type of photic damage is produced by PDT?

Answer 13

photochemical

Question 14

how long to stay out of sun after verteporfin?

Answer 14

2-5 days

Question 15

advantages of indirect and of direct visualization systems for vitrectomy?

Answer 15

indirect: wider view, better view through media opacities, gas tamponades, and miotic pupils
direct: better mag, better stereopsis

Question 16

ICG is used in vitreoretinal surgery to stain which structure?

Answer 16

ILM

Question 17

lifespan of SF6 and C3F8 inside the eye at nonexpansile concentrations?

Answer 17

2 and 8 weeks, respectively

Question 18

main advantage of small gauge vitrectomy

Answer 18

no need to suture wounds

Question 19

indications and outcomes of PPV w/ membrane peel for ERM

Answer 19

indicated for reduced vision or visual distortion interfering with binocularity, generally 20/40-20/60 or worse. 2/3 of patients will have 2-line improvement but may take 6-12 months to fully improve

Question 20

indications for surgery for macular hole? steps to surgery? dyes and stains used?

Answer 20

stage 2 or greater (50% stage 1 spontaneously resolve). PPV + membrane peel + air or gas tamponade and face-down positioning. ICG, brilliant blue G, tryptan blue and, triamcinolone are used to identify ILM and vitreous

Question 21

use of vitrectomy for submacular hemorrhage?

Answer 21

early studies showed no benefit. newer techniques may improve outcomes but are still controversial

Question 22

when should pre-op anti-VEGF be given prior to PPV for vit heme?

Answer 22

10 days pre-op

Question 23

indications for vitrectomy in tractional RDs?

Answer 23

involving or threatening the macula, or if combined RRD/tractional RD

Question 24

types of and most common causes of post-op endophthalmitis

Answer 24

• acute-onset ( 6 weeks): P. acnes, coag-neg staph, fungi

- bleb-related (often months to years post-op) - Strep spp. and Haemophilus

Question 25

conclusion from endophthalmitis vitrectomy study

Answer 25

LP: vitrectomy | HM or better: tap and inject

Question 26

presentation and management of P. acnes endophthalmitis

Answer 26

- chronic post-op endophthalmitis (however not always after 6 weeks) with peripheral white plaque in capsular bag - PPV w/ injection of vanc next to or in capsular bag. if recurs, should consider subtotal or total capsulectomy with IOL exchange

Question 27

management of blebitis and blebitis with endophthalmitis

Answer 27

w/o endophth: topical or subconj abx | w/ endophth: intravitreal abx +/- PPV

Question 28

nuclear v cortical retained lens material

Answer 28

cortical often absorbed w/o inflammation. nuclear remnants usually cause chronic inflammation

Question 29

risk factors for suprachoroidal hemorrhage

Answer 29

``` "Too Much Alcohol Gives A Heart Attack" Tachycardia Myopia Advanced age Glaucoma Aphakia Hypertension Atherosclerotic disease ```

Question 30

management of intraoperative suprachoroidal hemorrhage

Answer 30

immediate closure of all wounds with removal of any incarcerated vitreous. then observe for 7-14 days

Question 31

risk factors for needle penetration of globe

Answer 31

high axial myopia, posterior staphyloma, previous scleral buckle, poor patient cooperation, inexperience of surgeon

Question 32

risk factors for post-phaco RRD

Answer 32

younger age, male sex, longer axial length

Question 33

name the classic indications for pneumatic retinopexy

Answer 33

1. confidence that all breaks have been found 2. clear media 3. all breaks in superior 8 clock hours 4. no grade C or D PVR 5. single break or multiple breaks w/in 1.5 clock hors 6. cooperative patient

Question 34

findings of Silicone Study

Answer 34

tamponade with SF6 inferior to silicone or C3F8. silicone with lower rates of hypotony than C3F8

Question 35

percent of reattachment of RD: 1. at initial surgery 2. at second surgery 3. final outcome after any number of surgeries

Answer 35

1. 80-90% 2. 70% 3. 90-100%

Question 36

protective factors and risk factors for success or RD repair

Answer 36

protective: demarcation lines, RDs caused by dialysis or small holes RF: aphakia, pseudophakia, giant retinal tear, PVR, uveitis, choroidal detachment, posterior breaks 2/2 trauma

Question 37

visual acuity outcomes for RD

Answer 37

mac-on: 85-90% regain pre-RD acuity mac-off: 1/3-1/2 regain 20/50 or better --mac off 1 week: 50% 20/70 or better

Question 38

most common complication of vitrectomy? prevalence? other relatively common important complication?

Answer 38

- nuclear sclerotic cataract - 90% older than 50 will get visually sign NSC by 3-6 months - open angle glaucoma

Question 39

type of cataract that silicone oil leads to

Answer 39

PSC

Question 40

rate of endophthalmitis from intravitreal injection

Answer 40

0.02 - 0.2%

Question 41

presumed source site of endophthalmitis from intravitreal injection

Answer 41

patient's conjunctiva

Question 42

organism with proportionally higher frequency in endophthalmitis from intravitreal injection compared to intraocular surgery

Answer 42

Strep viridans (oral flora)

Question 43

proven measures to decrease risk of endophthalmitis from intravitreal injection?

Answer 43

none are proven, however consensus is to use povidone-iodine 5% to ocular surface for 60-90s prior to injection