You are a resident on your glaucoma rotation seeing a 62-year-old woman who is a day 1 post-op, following trabeculectomy. At the end of yesterday’s case, the IOP was 3 mmHg. However, this morning she has a pressure of 52, and her vision is hand motion. On slit lamp exam, the anterior chamber is flat and there is cornea-lenticular touch (she is phakic). The surgical peripheral iridotomy appears patent. The bleb is raised. You are unable to get a reliable view into the posterior segment; however, on B-scan there is no evidence of suprachoroidal hemorrhage or posterior masses.
What is your next step?
A. Administer atropine
B. Administer miotic drops to alleviate angle closure
C. Bring the patient to the OR immediately
D. Perform AC tap to lower pressure
E. Perform lysis of flap sutures
The correct answer is A.
In this case, your 1 day post-trabeculectomy patient presents with a high IOP and flat/shallow AC. The differential diagnosis here includes pupillary block, suprachoroidal hemorrhage, or aqueous misdirection (malignant glaucoma). Here, the presence of a patent PI and the absence of findings on ultrasound rule out pupillary block and suprachoroidal hemorrhage, making malignant glaucoma the most likely diagnosis. The mechanism of malignant glaucoma is debated; though, most described mechanisms center around the posterior diversion of aqueous humor that becomes entrapped posterior to or within the vitreous body. (Choice D would be unhelpful because the aqueous is no longer in the AC. Moreover, the issue here is not related to the flap’s functionality. In this scenario, the flap appears to be functioning, as a raised bleb is seen, making E incorrect.) Dr. Harry Quigley has proposed that expansion of the choroidal layer contributes to increased IOP, which causes aqueous to leave the AC. If the vitreous is unable to allow for free aqueous flow, the aqueous can become trapped posterior to the vitreous, and cause anterior movement of the vitreous, lens, and iris (See Figure 1). Regardless of the mechanism, treatment for malignant glaucoma is typically carried out in a step-wise fashion. The first step is administration of cycloplegic drops, which cause a posterior shift in the iris/ciliary body Therefore, choice A (administer atropine) is correct. Miotic drops should be avoided because they cause an anterior shift of the lens-iris diaphragm (Choice B). Additional medical therapy includes aqueous suppressants and osmotic agents that dehydrate the vitreous body. Once medical therapy has been tried, you should proceed to procedural or surgical intervention (Choice C). In aphakic or pseudophakic patients, a YAG posterior capsulotomy with disruption of the anterior hyaloid face may be enough to restore the pressure gradient between the anterior and posterior segments. In this phakic patient, you may try to disrupt the anterior hyaloid through the patient PI; however, the most likely next step after trialing medical therapy is surgery. Typically, this involves a core vitrectomy with disruption of the anterior hyaloid face. In a pseudophakic patient, an irido-zonulo-hyaloido-vitrectomy (IZHV) may also be helpful.
References:
https://glaucomatoday.com/articles/2006-nov-dec/1106_34.html, https://pmc.ncbi.nlm.nih.gov/articles/PMC3038515/#CIT44,