Retina surgery & procedures Flashcards
Dyes used to stain ILM
Brilliant blue G is a vital dye stains the ILM macular surgery (MC in Europe). Better safety than ICG.
ICG
Triamcinolone has a variety of uses in Ophthalmology including: 1) visualization of vitreous during either anterior or posterior vitrectomy; 2) as a intravitreal or subTenon’s injection for inflammatory ocular conditions (e.g. pars planitis) or macular edema; and 3) as an alternative to excision for chalazia.
FTMH (full-thickness macular hole)
occur in approximately 2% of cases following ERM removal.
o. mechanisms for hole formation:
weakening of the glial structure of the retina induced by the decapitation of Müller cells
opening or de-roofing of intraretinal cysts
contraction of residual ILM
direct mechanical trauma
ILM-staining dye toxicity.
Observation: eccentric FTMH has minimal impact on the patient’s subjective visual function unless it occurs either close to the fovea (within one disc diameter) or in the nasal macula within the papillomacular bundle.
eccentric FTMH does not seem to readily accumulate SRF with subsequent RD though there may be a small risk in highly myopic patients.
idiopathic ERM
idiopathic ERM is almost always associated with the presence of a PVD
Increased risk of ERM in pts with:
moderate to high myopia
retinal vascular diseases (like DR and RVO)
A) ERMs are found in 2% of patients over the age of 50 and in 20% of patients over the age of 75 at autopsy.
B) Although histologic examination may reveal the presence of fibroblasts, macrophages, and hyalocytes, RPE cells and retinal glial cells (astrocytes and Muller cells) are predominately found.
C) PPV with MP = recommended procedure for the management of a symptomatic ERM. Although 50-75% of patients improve after surgery, VA rarely returns to the level that existed prior to ERM formation (but post-op VA improves for 6-12 mo s/p surgery). Metamorphopsia Sx improve the most
D) ILM peeling in conjunction with ERM removal prohibits ERM regrowth in the postoperative period. ERMs are unable to re-proliferate on the surface of the nerve fiber layer, which explains the popularity of ILM MP for this condition.
Vitrectomy using an indirect visualization system compared to a direct visualization system:
indirect visualization system advantage= WIDER viewing angle as well as an easier view through media opacities, small pupils, and gas bubbles.
Direct visualization systems have the advantage of greater stereopsis, but with a more limited field of view.
Anterior segment ischemia
Risks: encircling scleral buckles detachment of extraocular muscles use of local anesthesia *with* epinephrine overzealous photocoagulation or cryopexy inadequate patient hydration inadequate patient oxygenation
Hard to fix RD
Worse for aphakic and pseudophakic eyes
worst for RDs 2/2 PVR, giant tears, choroidal detachment, inflammation, and traumatic posterior breaks.
Pneumatic retinopexy criteria
Classic indications to use pneumatic retinopexy for RD repair is that the breaks are confined to the superior eight clock-hours.
absence of proliferative vitreoretinopathy grade C or D
Clear media
Confidence that all breaks have been found
Anatomy worrisome for RD
RD 2/2 giant retinal tears (tears > 90 degrees) =high redetachment rate 2/2 PVR.
2/2 high risk of failure: do PPV, PFC, laser photocoagulation demarcation and complete FAX.
Retinal detachment treatment in phakic eyes
scleral buckle
Best Px for RD reapir
Px best for RDs 2/2:
small holes or retinal dialyses and those associated with demarcation lines.
Lasers - type of damage of photo-____
Mechanical damage (Photodisruption) occurs when the absorbed light is strong enough to produce gas bubbles that result in a shock wave to mechanically disrupt tissues. YAG capsulotomy is an example of light energy causing mechanical damage.
Thermal damage (photocoagulation) is when absorbed light causes a rise in temperature of surrounding tissues. Laser photocoagulation (e.g. panretinal photocoagulation) is an application of this type of damage.
Photochemical damage is when light induces biochemical reactions that cause tissue destruction without a rise in temperature. Solar retinopathy and overexposure from an operating microscope are examples of photochemical damage.
Photoablation occurs when laser pulses selectively ablate small areas of tissue without harming adjacent tissue. It is much less destructive than photocoagulation. Excimer lasers use photoablation in corneal refractive procedures because it allows selective ablation of tissue without resulting in damage or subsequent scarring of adjacent corneal tissue.
To decrease the risk of rupture of Bruchs membrane should you use large or small spot size
Small, not large, spot sizes increase the risk of rupture of Bruch’s membrane and subsequent CNV.
less painful laser wavelength
Green lasers are preferred since they are effective and less painful than the other wavelengths.
Should you use pars plana magnet with retinal tear?
Answer: no
Use of a pars plana magnet in the presence of an associated retinal tear risks further retinal damage and possible detachment.
disadvantages of small-gauge (e.g. 25-G) vitrectomy
The disadvantages of small-gauge (e.g. 25-G) vitrectomy are increased risk of post-op hypotony, retinal tears, and endophthalmitis. These complications relate to these small-gauge wounds typically not being sutured closed at the end of the case.
MC complication s/p PPV
The most common complication after vitrectomy surgery is the development of a visually-significant cataract (~90%). Another noteworthy complication is the increased long-term risk of open-angle glaucoma (~10-20%) after vitrectomy.
Why do we peel the ILM?
Internal limiting peeling in conjunction with ERM removal prohibits ERM regrowth in the postoperative period. ERMs are unable to re-proliferate on the surface of the nerve fiber layer, which explains the popularity of internal limiting peeling during pars plana vitrectomy for this condition.
risk of retinal detachment (RD) in CE/IOL?
Risk of retinal detachment (RD) is increased in YOUNGER patients undergoing cataract extraction (not older).
Other major risk factors for a RD after cataract surgery include: zonular dehiscence RD in fellow eye axial length >23 mm male gender (less likely to have PVD)
Vitreous taps vs. aqueous tap needle size
Vitreous taps are generally obtained with a 25-gauge 1-inch needle, while aqueous samples are obtained with a 30-gauge needle on a tuberculin syringe. The needle for the vitreous tap should be aimed at the mid-cavity of the vitreous.
PDT
Regular vs. Reduced fluence?
Regular: 600mW/cm2
Reduced: 300mW/cm2
Anti-VEGF
Pegaptanib (Macugen)
pegylated anti-VEGF RNA aptamer
binds VEGF 165
0.3mg
Aflibercept (Eylea)
ligand-binding domain of VEGFR ½ + IgG Fc
binds VEGF-A & placental-like GF
2mg, 4mg
Bevacizumab (Avastin)
full-length Mab + Fc
targets VEGF-A
1.25mg, 2.5mg
Ranibizumab (Lucentis)
48kD Fab of Mab (<50kD to cross retina)
targets VEGF-A
0.3mg (DME), 0.5mg (AMD), 2mg
Panretinal Photocoagulation (PRP):
> 1200 spots, 500um, 0.1s, 1/5 apart
Side effects? Lost of peripheral vision Decrease in night or color vision Glare, photopsias Worsens macular edema Avoid 3:00 & 9:00? Pain from long ciliary nerves PRP before CE/IOL if view clear
Focal / Grid Laser:
50-100um, 0.1s
Whiten MA for focal or >1 spot size for grid
Treat CSME before PRP for hrPDR
Treat CSME before CE/IOL
