Surgical Procedures Flashcards
What does laser stand for?
light amplification by stimulated emission of radiation
What is coherence?
spatial-precise focusing widths of several microns, temporal-monochromatic wavelength
What is fluence?
flux integrated over time, energy delivered per unit area (spot size, power/wattage, exposure time)
What do resonance mirrors do?
allow amplification of the laser energy as the photons bounce back and forth between two mirrors within an optical cavity or tube
3 main types of laser-tissue interactions:
photothermal, photochemical, photoionization
What is photothermal?
photocoagulation and photovaporization, rise in temperature that denatures proteins
What is photochemical?
photoradiation (PDT) and photoablation (Excimer), formation or destruction of chemical bonds
What is photoionization?
electrons stripped from tissue creates expanding plasma cloud and ensuing acoustic shock wave disrupting tissues (Nd:YAG)
3 unique characteristics of lasers:
coherent, monochromatic, collimated
What is coherence?
strong correlation between the electric fields across the beam (cross section)
What is monochromatic?
specific wavelength absorbed by specific tissue, allows for tissue selectivity
What is collimated?
minimal divergence of the beam (energy is stable across the whole beam) these two features allow for specific application to ophthalmology as small spot sizes can be used and specific tissues targeted
What wavelength do red (blood) tissues absorb?
blue and green laser light
What wavelength do brown (pigment) tissues absorb?
yellow, blue and green
Which wavelengths penetrate deeper?
longer wavelengths
Cornea absorbs
UV/100-280 nm (excimer)
Hemoglobin absorbs
yellow/555, green/542 (Nd:YAG)
Xanthphyll absorbs
blue/400
Melanin absorbs**
blue/400 (argon/green) – absorption decreases with increased wavelength
Water absorbs
infrared (YAG, diode)
What is a peripheral iridotomy?
creates opening in iris for alternate flow of aqueous
What is an indication for a PI?
narrow angle/iris bombe
What is the benefit of a PI?
helps prevent future ACG but IOP may increase in some and not without complications
What may cause a PI to fail?
choroidal thickening, abnormal iris activity secondary to peripheral iris roll (not true bombe)
What is a laser peripheral iridotomy?
superior or temporal hole within iris crypt
What do you prescribe before a LPI?
pilocarpine 2% to make iris stretched tight
Why might both Nd:YAG and argon lasers be used for a LPI?
allows for photocoagulation, argon laser burns tissue and allows the Nd:YAG laser to poke a hole in it, reduces risk of bleeding
Which laser is more effective in a light iris for a LPI?
YAG
Difference between temporal and superior LPI:
superior may have more visual symptoms than temporal because tear prim can refract light under lid and actually focus it onto retina; temporal image is severely defocused resulting in decreased sensation; temporal may also have less pain
What is the post-op care for a LPI?
check IOP before they leave, steroid QID, pilocarpine, potentially hypotensive
Why use a steroid in LPI post op?
prevents scarring and closure
What are LPI complications?
IOP spike, hyphema, corneal epi/endo burns and edema, correctopia, iritis, lens opacity, monocular diplopia, retinal burns, LPI scarring over
What is a laser peripheral iridoplasty?
laser therapy inducing cicatricial iris-retraction of the iris stroma peripherally to pull it away from the angle in angle closure or plateau iris
What are indications of a laser peripheral iridoplasty?
angle closure non-responsive to LPI, plateau iris, malignant glaucoma post RD
What laser is used for a laser peripheral iridoplasty?
argon laser 200-400mW with 5 to 10 spots per quadrant
What is the post op of a laser peripheral iridoplasty?
similar to LPI, keep on steroids and watch for complications
Why should you recommend surgical treatment to patients?
non-adherence, challenges maintaining multiple medications, lack of medical control, laser or microinvasive tx before advanced incisional surgery, patient understands risks and benefits, operate before blindness
What is an argon laser trabeculoplasty?
A scar in the trabecular meshwork
How does the ALT work?
blue-green argon laser used on anterior TM and absorption by pigment in TM yields shrinkage of collagen in trabecular lamellae expanding schlemm’s canal
How does an ALT expand Schlemm’s?
two laser spots are made within the TM and cause contraction of the TM in between the two laser spots, pulls schlemm’s canal towards anterior chamber and allows for more outflow
What is the mechanism of the ALT?
reduces debris by upregulating phagocytosis
What are indications for an ALT?
particularly effective in pigmentary and pseudoexpoliative glaucoma because laser is absorbed by more pigment
What is the pre-treatment of an ALT?
apraclonidine 1% or brimonidine 0.2%
What is the ALT procedure?
topical anesthetic, 3 mirror gonio lens, treatment 180 or 360 degrees, 50-100 burns, 50 microns size, 0.6-1.0 watts, 0.1 sec exposure time, treat in anterior TM
What are ALT complications?
IOP spike, iritis, PAS, heme, K edema/burns, limited repeatability
Why does an ALT have limited repeatability?
once you scar that area of TM, you’ve damaged the tissue, don’t want to scar the entire TM
What was discovered in the glaucoma laser trial of 1984?
eyes treated with ALT before meds had IOP 1.2 mmHg lower, better VF, fewer cup changes; 30% of ALT had initial IOP increase with 12% being over 10 mmHg
What laser is used in a SLT?
q-switched ND:YAG laser, frequency doubled selective for pigment (1064 nm wavelength down to 532 nm) 3 ns oulse, 400 micron spot size, 40-50 spots per 180 degrees
What is q switching?
really rapid pulse of energy, prevents burning of tissue (not a hot laser)
What is the mechanism of SLT?
induces cytokine release from melanosomes, macrophage activity decreases TM debris and MMP activity increases porosity of TM endothelium; potential vasoactive effect on endothelial cells
Explain the SLT laser impact:
large spot size with low energy per area (fluence) so no coagulative damage aka cool laser
What does Dr. Dork call the SLT mechanism?
scrubbing bubbles of the TM, clean out TM so we increase aqueous outflow via macrophage activity
Is SLT repeatable?
yes but 2nd treatment tends to show less effect and 3+ treatments not very effective
Is SLT better in more or less pigmented angle?
more, more pigment=more absorption of energy
What are SLT complications?
risk of IOP spike, more energy absorbed=more risk of complications
What technique should you consider with SLT?
treat 180 degrees then go back and do the other 180 at f/u
What is the SLT post-op?
NSAID qid 2-5 days or nothing, continue hypotensives
Why do we not use a steroid in an SLT?
we do NOT want to inhibit the response, we want the immune response to break up inflammation
When does the max IOP response of a SLT occur?
4-6 weeks, 20% IOP decrease (5-6 mmHg)
What do the microscopic images of ALT vs SLT show?
ALT laser burn to the tissue causes the adjacent tissue to stretch, SLT has no effect on tissue
Compare SLT and ALT:
equal efficacy with reduced side effects using SLT, may do SLT after ALT
SLT/MED study results:
60% of eyes having SLT 360 degrees had IOP decrease >30%
What was the LiGHT study?
laser in glaucoma and ocular hypertension trial
What was the primary and secondary outcome of the LiGHT study?
primary- quality of life, secondary clinical effective ness (target IOP) and visual function
Results of LiGHT study:
equal QOL between med and SLT group, glaucoma symptom score worse in med group, overall cost more in med group, more visits at target IOP in SLT program, slightly more disease progression in med group
Why might an SLTdo better than medication?
non concern for adherence, no change with diurnal efficacy
What are the SLT review points?
effective, no photocoagulative damage to TM, repeatable, upregulates phagocytic activity, targets melanosomes (want less intense tx in pts with excessive pigment
What is the endolaser to CP (ECP)
uses endoscopic delivery of argon or green laser to ciliary body
Where does the ECP work?
limbal or pars plana entry
What is ECP often performed in conjunction with?
vitreoretinal surgery
What are ECP complications?
pain, iritis w/ synechiae, hypotony, phthisis, zonular damage, reduced accom, pupil distortion, CME, IOP spike, RD, conjunctival burn, choroidal detachment, intraocular heme, endophthalmitis
What is cyclophotocoagulation CPC?
diode laser therapy to CB with trans-scleral approach, similar to ECP but is administered outside the eye, used as a last ditch effort
Which has more pain CPC or ECP?
CPCe
Where is the CPC performed?
laser probe applied at limbus to cause trauma to ciliary processes to reduce aqueous production
What are CPC complications?
uveitis, K edema, pain, uveitis, hyphema, phthisis bulbi, high IOP spikes permanently, reduction in central VA
When is CPC indicated?
poorly controlled OAG or MMG, use as cryo cycloablation, advanced glaucoma after filter, secondary glaucoma (like neovascular), instead of endolaser
What is a goniotomy?
superficial incision into uveal TM, removes obstruction to aqueous outflow
When is goniotomy indicated?
congenital glaucoma– poor formation of TM resulting in reduced outflow
When should a goniotomy be performed?
between 1 month and before 2 years
What tool is used for a goniotomy?
laser or phaco probe (trabecutome) hx done with scapel like tool
What is the newest form of goniotomy therapy?
kahook dual blade, MIGS
What is a trabeculectomy?
opening made from sclera through or above TM into anterior chamber for direct drainage of aqueous into sub conj bleb
What is the standard for advanced/significant incisional surgery for glaucoma?
trabeculectomy
Where does a bleb drain?
conjunctival and episcleral veins
What are the two anti-metabolites and what do they do?
mitomycin C and 5FU, chemotherapeutic agents that reduce scarring after the procedure
Explain mitomycin C:
used more often now, less pain, MMC soaked sponge place over sx site or via injection during procedure, then thorough lavage
Explain 5-flurouracil:
injected in area daily for 1 week after sx procedure
Trab + antimetabolite risks:
less risk of failure, greater risk of over filtration and leak, risk of too much aqueous draining resulting in low IOP
What is the trabeculectomy post op?
DO NOT USE GLC MEDS, every appointment VA, IOP, slit lamp, day 1 start steroid-antibiotic and possible atropine (decrease over filtration and pushes iris toward angle), week 2 switch to steroid only, month 1 steroid taper, monthe 2 dilate, end steroid
Bleb evaluation (ELVIS):
elevation (not too much), location (11 or 12 oclock), vascularization (not too much), infection (creamy white), seidel
Bleb management:
massage, needling, laser suture lysis, revision of surgery
What is the bleb massage?
pressure on globe 180 degrees away form the bleb, pushes aqueous out and into bleb
What is bleb needling?
break up scar tissue on top of bleb
What is bleb laser suture lysis?
break open suture to open up the flap a bit more
What are trab complications?
flat anterior chamber, high IOP/failure, heme, infection/blebitis, endophthalmitis, choroidal effusion (over-filtration), K edema, bleb rupture
How do you stop an active seidel?
double pressure patch, large diameter CL (22mm), consider atropine
How do you stop over-filtration?
autologous injection (coagulative factors can seal the inside of the bleb), simmons shell
How do you manage high IOP after bleb surgery?
consider massage, increase steroids, revision
What are filtering devices?
trab w/ tube and reservoir, device rests where bleb is and contains perforations to allow aqueous to percolate out, tube keeps it open, goo for neovascular component or if pt is at risk for their bleb opening up
Valved vs valveless drainage:
valve-ahmed, less- molteno, baerveldt
What is the ahmed valve?
silicone tube with one or two polypropylene plates, valve opens at pressure of 12 and closes at 8-10
What is the molteno and baerveldt?
molteno is most widely used, silicone tube w/ 1 or 2 polypropylene plates 13 mm in diatere, the baerveldt is a silicone tube with large diameter 250-350 mm^2 barium impregnated silicone plate
What are glaucoma drainage device complications?
similar to that of trabs, ocular motility disturbance, tube or plate extrusion, tube migration (contact with iris or cornea), complications usually require surgical revision
What is a viscocanalostomy VCL?
small sclerostomy into roof of schlemm’s canal, catheterization and viscoelastic fluid irrigated through canal
What does a VCL do?
dilates canal and collector channel to increase aqueous outflow, possible mild bleb formation
What is the VCL efficacy?
initial 1 year equivalent effect to trab with lower side effects and complications, esp in congenital, not as effective as trab in some studies of POAG
What is the success rate of VCL?
60% success rate at 60 months, may need ancillary laser procedure
What is iTrack?
current US product, ab-externo ciscovanalostomy with cataract surgery
What are MIGS procedures?
micro invasive glaucoma surgery increasing aqueous outflow through small incisional surgeries, commonly in conjunction with cataract surgery, mostly ab interno
What is ab-interno?
excision of TM through corneal incision (internal)
What is ab-externo?
excision of TM through sclera and conjunctiva (external)
What are FDA approved MIGS?
iStent, Hydrus, Xen 45 gel, cypass, omni 360
What MIGS are approved in conjunction with cataract surgery?
hydrus and istent
What is OMNI?
ab interno, combines canaloplasty with trabeculotomy, probe goes 360 and injects viscoelastic to stretch it open and then pulls tubing that pulls open the TM, can be done with cataract surgery or alone
What does OMNI treat?
three sources of outflow resistance, TM, schlemms and collector channels
What are OMNI complications?
hyphema, inflammation/debris from TM, K edema
Why is a hyphema from OMNI a good thing?
means reflux from episcleral plexus
What should you try with K edema?
rhopressa, it has a secondary application to Fuch’s
What is OMNI post op?
normal cataract type post op meds, it’s better in a day or 2
What is iStent?
small implant draining aqueous directly to Schlemm’s canal, used in conjunction with cataract sx
How is the iStent placed?
placed via small temporal corneal incision, placed into inferonasal quadrant and has improved result when closer to collector channels
What is the IOP decrease of iStent?
moderate, 4 mmHg
What is the iStent 2 efficacy?
24 months 75% had IOP reduction of 20% or more w/o meds (62% in cataract only)
What was the mean IOP decrease in iStent 2?
6.9 mmHg vs 5.4 in cataract only
What is iStent supra?
drains to suprachoroidal space, under investigation now
What is the hydrus microstent?
schlemm’s canal scaffolding device, dilates schlemm’s canal and allows alternate pathway into schlemms (90 degrees of schlemms), in conjunction with phaco IOL sx
What is the IOP decrease of the hydrus?
4 mmHg
What is the Xen45 gel stent
soft gel tube that allows aqueous drainage into sunconjunctival bleb, creates alternate pathway for aqueous to exit the eye
Is Xen45 gel externo or interno?
ab interno, approved on severe/refractory GLC
What is the Xen45 gel efficacy?
75% had IOP decrease of 20% or more on same or fewer meds, mean IOP decrease 9.1 mmHg
What is the added benefit of Xen45 gel?
reduction in topical meds by average of 1.1 meds
What is the variability in procedure for Xen gel?
externo and interno, placement in sub-conj or sub-tenon space, conjunctival flap opened or not, use of mitomycin c
What is a common complication solution for Xen?
needling is common
What is the cypass micro-stent?
shunt placed in anterior chamber to drain aqueous to supraciliary space, not on the market anymore
Is cypass interno or externo?
interno
What is the pressure gradient between the anterior chamber and supraciliary space?
3.5 mmHg, allows for good IOP decrease w/o hypotony, accessing similar pathway to uveal-scleral outflow
What is the cypass efficacy?
72.5% of eyes maintained 20% IOP reduction or greater at 24 months without meds (58% in cataract), 61% had diurnal IOP b/w 6 and 18 (43.5% in cataract)
How does cypass compare to cataract surgery alone?
32% improvement in IOP reduction
How did cypass do with acuity and hypotony?
only 3% hypotony in first 30 days post op, 8.8% lost >10 letters vs 15% in cataract
Why was cypass recalled?
voluntary recall in 2018, some patients had decreased K endothelial cell count, esp if stent was not advances as far into TM, company decided K endo cell loss not appropriate in mild GLC
What is the preserflo microshunt?
drains aqueous to subconj/sub-tenon’s bleb
Is preserflo interno or externo?
externo, slightly more invasice but less invasice than trab with the formation of a bleb
What is different about preserflo and FDA?
currently in trials, not in conjunction with cataract surgery, comparing efficacy against trabeculectomy
What is the preserflo efficacy?
mean IOP remaining below 15 mmHg, 50% IOP reduction at 3 year mark, 60% of patients are medicine free
Preserflo microshunt vs Xen gel:
comparable to slightly better IOP control and med reduction with preserflo microshunt
