Flashcards in Lasers & surgery Deck (11):
Needle gauge for sclerostomy
Typically, a 23-gauge needle is used to create the sclerostomy through which the tube will be inserted.
A tighter sclerostomy (e.g. 25-gauge) is sometimes indicated in certain situations (e.g. in eyes with thin sclera).
Argon Laser Trabeculoplasty (ALT)
50-micron spot, 0.1-second duration, and a power titrated between 300 and 1000 mW.
40-50 spots, 180 deg (IOP spike if 360)
Slight blanching of ant pigmented TM
Works in PXF>PDG>POAG; not LTG
Not in juvenile or trauma
Takes 4-6 weeks to work
80% effective at IOP lowering x 1yr
ICE syndrome and laser
The slit lamp photo shows corectopia, some iris atrophy, and a subtle "beaten bronze" appearance of the corneal endothelium. The gonioscopy shows some peripheral anterior synechiae. In addition, this female patient is presenting in a unilateral manner. These features are classic for "iridocorneal endothelial" (ICE) syndrome which is an ocular disease that causes a secondary angle closure type of glaucoma.
There are 3 variants of ICE syndrome (i.e. "Cogan-Reese syndrome"; "Chandler syndrome"; and "essential iris atrophy"), all of which feature an abnormal corneal endothelium ("beaten bronze") and whose ocular signs may overlap with each other.
The predominant feature in Cogan-Reese syndrome is the presence of multiple, pedunculated iris nodules; the major feature in Chandler syndrome is corneal edema; and the major feature in essential iris atrophy is corectopia and hole formation.
Chandler syndrome is the most common of the ICE syndromes. Glaucoma may develop in 50% of patients with ICE syndrome. Laser trabeculoplasty has no role in the treatment of ICE syndrome.
patient with the highest risk of developing hypotony maculopathy
The patient with the highest risk of developing hypotony maculopathy is a young myopic person. Of the answer choices, pigmentary glaucoma is the one classically found in young myopic individuals. It is not known how long hypotony maculopathy can remain untreated before vision loss is permanent. Many glaucoma surgeons believe 3 months is a reasonable time to wait before attempting to increase intraocular pressure surgically.
Answer choice "A" describes a person with nanophthalmos. These individuals are markedly hyperopic and are at risk for choroidal effusions after glaucoma surgery. Answer choice "B" refers to a person with phacomorphic glaucoma. Answer choice "C" refers to a person with pseudoexfoliation glaucoma.
Lens rim artifact
This is an example of a lens rim artifact that can occur if the trial lens that is used is too far from the patient's eye or not centered correctly. This causes the rim of the lens to block the patient's peripheral visual field. This type of artifact is present in approximately 10% of all central fields when a trial lens is used. This defect is not necessarily always completely-circular and thus may mimic glaucomatous defects (e.g. nasal steps). The most commonly-involved quadrant is the temporal field.
Risk factors for lens rim artifact include higher hyperopic corrections and older age.
Ahmed valve HTN phase
The "hypertensive phase" of the Ahmed implant describes the phenomenon whereby a significant number of eyes will experience an abrupt IOP elevation even after the IOP was low initially after Ahmed insertion. This typically occurs around 4-6 weeks after surgery.
Selective Laser Trabeculoplasty (SLT)
YAG machine: 400um 0.3ns 0.4-1.8mJ (SLT)
40-50 spots, 180 or 360 deg
Lower energy to target melanin in cells
Use with caution in pigment dispersion
Can re-treat if necessary
Thinner, more avascular bleb
Increases endophthalmitis risk
Increases success rate
Avoid in myopics (risk of hypotony)
5-FU less potent, more corneal toxicity
What gauge for sclerostomy?
Types of valves
Valve: Ahmed, Krupin, White pump
No valve: Baerveldt, Moltino, Schocket
If no valve, needs suture but possible hypertensive phase