Aqueous misdirection is complication of intraocular surgery

Speaking during a session on complications of surgery, Dr. Tello said he and his colleagues at New York Medical College, where he is assistant professor of clinical ophthalmology, and the New York Eye and Ear Infirmary, where he is associate director of the glaucoma service, have identified two mechanisms for the condition, which is also called malignant glaucoma or ciliary block glaucoma. In either case, medical management is the first line of treatment, with surgery as a backup.

Both mechanisms were identified by use of ultrasound biomicroscopy, Dr. Tello said.

Managed medically, surgically Aqueous misdirection can be managed medically or surgically, with medical management being the first line of defense, Dr. Tello said. The goal of medical treatment is to restore normal flow of aqueous humor into the anterior chamber and to interrupt the abnormal vitreociliary relationship, a goal that can be achieved in 50% of cases within 4 to 5 days, he said.

Medications used for treatment include topical steroids such as prednisolone acetate 1%, applied every 1 to 2 hours to reduce inflammation, Dr. Tello said.

"Intensive cycloplegia is used to reverse the anterior rotation of the ciliary body, aqueous suppressants to decrease the amount of aqueous humor, and hyperosmotics to decompress the vitreous," he said. "Once the clinical picture has improved, cycloplegic agents are gently tapered off, however, it is recommended to treat these patients chronically with cycloplegic agents if malignant glaucoma recurs."

Surgery is indicated when pressure remains high despite medical treatment, Dr. Tello said. "Disruption of the anterior hyaloid using the Nd:YAG laser to eliminate vitreociliary block and allow movement of aqueous into the anterior segment is the treatment of choice in aphakic and pseudophakic eyes that medical treatment has not improved," he said.

The Nd:YAG hyaloidotomy should be performed through the peripheral iridectomy to avoid blockage of the aqueous flow with the IOL, although it can be performed through the pupil in aphakic patients, Dr. Tello said.

"If the clinical picture of aqueous misdirection is not improved medically and if the patient presents with ciliary body detachment, the patient may benefit from surgical drainage through a sclerotomy," he said. "If the ciliary body is not detached, these patients do require vitrectomy.

"In these cases, the vitreous cutter should be introduced through an incision somewhat anterior, to disrupt the anterior hyaloid as well as the zonular apparatus," he said. "If the anterior chamber remains shallow despite a vitrectomy with the angle closed, the patient will require cataract extraction, lensectomy, or removal of the IOL."

Aqueous misdirection is characterized clinically by an elevated IOP, shallow or flat anterior chamber, patent iridectomy, and normal posterior segment examination by ophthalmoscopy or B-scan ultrasonography. It is most often seen as a complication of glaucoma filtering surgery in eyes with chronic angle-closure glaucoma, Dr. Tello explained.

However, it can also occur after cataract extraction, transscleral cytophotocoagulation, laser iridectomy, or laser suture lysis. It has also been associated with central retinal vein occlusion and retinopathy of prematurity, and after the start of pilocarpine treatment of eyes that have undergone filtering surgery.

The Glaucoma 2004 meeting was supported through an unrestricted educational grant from Pfizer Ophthalmics. The New York Eye and Ear Infirmary (providing accreditation) and Ophthalmology Times jointly sponsored the program, with cooperation and support from the University of Medicine & Dentistry of New Jersey and the Manhattan Eye, Ear and Throat Hospital.