Aqueous misdirection can occur following many types of intraocular surgery, including cataract surgery with1-5 and without6 intraocular lens implantation, trabeculectomy,7 and seton implant surgery.8 It has occurred following laser surgical procedures such as laser suture lysis of trabeculectomy flap sutures,9 laser iridotomy,10,11 Nd: YAG laser posterior capsulo tomy,12 and noncontact Nd:YAG laser cyclophotocoagulation.13 Aqueous misdirection has also been reported in eyes that have not undergone prior surgery, with and without the use of miotics. 17 Patients who have aqueous misdirection in one eye are at risk of having it in their other eye.10
Aqueous misdirection is initially treated medically with cycloplegics, aqueous suppressants, and hyperosmotics.18 Nd: YAG laser hyaloidotomy5,19,21 and argon laser shrinkage of ciliary processes22 have been employed successfully in cases refractory to medical treatment. Surgical vitrectomy and disruption of the hyaloid face has been effective in cases refractory to medical and laser treatment.4,23
A 65-year-old man presented with the complaint of sudden visual loss in his right eye. Glaucoma surgery had been performed on his right eye 1 year earlier at another institution. His left eye had been blind for 20 years. He was not using any ophthalmic medications.
On examination, the visual acuity was light perception in the right eye and no light perception in the left eye. The left eye was phthisical. The intraocular pressure in the right eye was 1 3 mm Hg. The right eye had a cystic superior filtering bleb, a 2+ nuclear sclerotic cataract with posterior subcapsular opacification, a surgical iridectomy superiorly with posterior synechiae, and a deep and quiet anterior chamber. A fundus examination of the right eye revealed a large cup and a retinal detachment with a macular detachment, although visualization of the fundus was limited by the cataract. A B-scan ultrasound examination confirmed the existence of a fractional retinal detachment involving the macula (Fig. 1). The axial length, as measured by ?-scan ultrasound, was 19.85 mm.
Figure 1. Ultrasound of the right eye showing retinal detachment.
Figure 2. The shallow anterior chamber of aqueous misdirection after pars plana vitrectomy, scleral buckle, and extracapsular cataract extraction with posterior chamber intraocular lens implantation.
The patient underwent surgery to remove the cataract and repair the retinal detachment. Extracapsular cataract extraction with posterior chamber intraocular lens implantation was performed first using a temporal 7-ram scleral incision. An intraoperative fundus examination revealed a rhegmatogenous retinal detachment complicating peripheral reticular retinoschisis with an outer layer retinal break and many inner layer breaks. A pars plana vitrectomy was performed with an inferotemporal infusion and superior sclerotomies. Subretinal fluid was drained from a retinotomy with perfluorocarbon, followed by perfluorocarbon-SF6 20% gas exchange. Cryotherapy was performed, and an encircling scleral band with a sleeve was applied.
On the first postoperative day, an examination of the right eye revealed a visual acuity of light perception, an intraocular pressure of 19 mm Hg by applanation, a deep anterior chamber, and a flat retina. Topical prednisolone acetate 1%, gentamicin 0.3% drops, and homatropine were started for the right eye. On the second postoperative day, the anterior chamber was shallow and the intraocular pressure was 26 mm Hg by applanation, with a filtering bleb still present. Topical timolol 0.5% (every 12 hours) and apraclonidine 0.5% (every 8 hours) were ordered for the right eye, and oral acetazolamide (500 mg twice daily) sustained-release capsules were prescribed. During the next 2 days, the filtering bleb flattened. On the 11th postoperative day, pain developed in the right eye. The intraocular pressure was 37 mm Hg by applanation. The patient was given oral glycerol (35 g in 50% solution).
The Glaucoma Service was consulted and a diagnosis of aqueous misdirection was made (Fig. 2). The anterior chamber deepened instantly after NdrYAG laser posterior capsulotomy and hyaloidotomy were performed through the preexisting superior surgical peripheral iridectomy. During the next 2 days, applanation intraocular pressures in the right eye were between 1 8 and 22 mm Hg with the patient's use of topical timolol 0.5%, apraclonidine 0.5%, prednisolone acetate 1%, and gentamicin 0.3%.
One week later, on the 23rd postoperative day, the patient returned to the emergency room complaining of pain in his right eye. The visual acuity was finger counting at 3 feet, the intraocular pressure by applanation was 40 mm Hg, and the anterior chamber was shallow. An Nd: YAG laser capsulotomy and hyaloidotomy were repeated in the same location. Instantaneous deepening of the anterior chamber resulted. By the afternoon, the anterior chamber was once again shallow and the intraocular pressure was 43 mm Hg by applanation. An Nd: YAG laser capsulotomy and hyaloidotomy were repeated a third time, and were followed once again by instantaneous deepening of the anterior chamber. Atropine 1 % drops for the right eye and acetazolamide (500 mg orally twice daily) sustained-release capsules were added to the medical regimen. Four days later, the intraocular pressure in the right eye was 18 mm Hg by applanation and there was a deep anterior chamber.
When the patient presented for a scheduled appointment 2 weeks later, his visual acuity was hand motions in the right eye. He had an intraocular pressure of 45 mm Hg by applanation and a shallow anterior chamber once again. The patient was taken to the operating room. A 15° blade was used to puncture the posterior capsule and anterior hyaloid through a corneal paracentesis incision and the preexisting iridectomy. The anterior chamber deepened instantly. An infusion line was inserted through a second paracentesis incision and a vitreous cutter was inserted through the first corneal incision to create a large opening in the posterior capsule and hyaloid face. A pediatric-size Ahmed glaucoma valve (New World Medical Inc., Rancho Cucamonga, CA) had been attached to sclera in the inferonasal quadrant before the anterior chamber was entered. The pediatric implant was used to allow for easier placement in the presence of the scleral buckle. A 3-mm length of the implant tube was inserted into the anterior chamber with an anterior-facing bevel. Donor sclera was used to cover the extraocular portion of the tube before the fornix-based conjunctival flap was closed.
Figure 3. Deep anterior chamber with an intraocular pressure of 6 mm Hg after capsulo-hyaloidotomy with implantation of an Ahmed glaucoma valve (New World Medical Inc., Rancho Cucamongo, CA). The faint image of the tube in the anterior chamber can be seen in the lower right-hand corner of this photograph.
Figure 4. Recurrence of aqueous misdirection 3 weeks after the capsulo-hyaloidotomy-seton implant procedure.
During the first 6 postoperative days, the visual acuity of the right eye was hand motions. The intraocular pressure by pneumotonometry ranged from 5 to 6 mm Hg, and the anterior chamber was deep (Fig. 3).
The patient was discharged. Three weeks later he returned with a flat anterior chamber, the implant tube buried in iris, and no bleb over the implant plate. The intraocular pressure by pneumotonometry was 27 mm Hg (Fig. 4).
The patient was returned to the operating room. A three-port vitrectomy was repeated. The anterior chamber once again deepened after a hyaloido-capsulo-iridectomy was performed superiorly, establishing a definitive communication between the vitreous cavity and the anterior chamber. Seven months later, the patient had a visual acuity of 5/200 in his right eye, a deep anterior chamber, a flat retina, and an applanation intraocular pressure of 12 mm Hg with timolol 0.5% (twice daily).
To the best of our knowledge, this is the first reported instance of aqueous misdirection occurring after pars plana vitrectomy in a patient who did not previously have this condition. Our patient had a large surgical iridectomy that we observed to be patent throughout the multiple recurrences of a shallow anterior chamber. Although blockage of the iridectomy by an inflammatory membrane or synechiae to posterior structures could cause a similar clinical picture through a pupillary block mechanism, we did not observe this to be the case. After each recurrence of anterior chamber shallowing, the entire chamber deepened instantaneously on disruption of the hyaloid face, which created a communication between the vitreous cavity and the anterior chamber.
There are other reports of cases in which aqueous misdirection recurred after pars plana vitrectomy that was employed as treatment for this condition. Byrnes et al. reported on 21 patients who underwent pars plana vitrectomy as treatment for aqueous misdirection refractory to medical management.23 As in our case, all 21 patients had undergone recent intraocular surgery, 19 having undergone recent trabeculectomy. All of the eyes were smaller than average, ranging from 19 to 21.5 mm in axial length. In 6 of 20 cases with adequate follow-up, aqueous misdirection recurred after initial vitrectomy. In 3 of these 6 patients, aqueous misdirection resolved with medical or laser treatment, whereas the other 3 were treated successfully with a second vitrectomy procedure.
Early reports of surgical treatments for aqueous misdirection discussed the necessity of disruption of the hyaloid face along with pars plana vitreous aspiration18 or anterior vitrectomy.24 Aqueous misdirection most likely developed in our patient after pars plana vitrectomy because the hyaloid face had been left intact. Little described a case of aqueous misdirection that developed after trabeculectomy in a phakic eye and recurred after initial core vitrectomy, and again after pars plana vitrectomy with cataract extraction without intraocular lens placement.25 Finally, the aqueous misdirection responded to Nd: YAG laser capsulotomy. As in our case, the anterior hyaloid must have been intact after the first two procedures. With laser treatment and subsequent surgical disruption of the vitreous face with a vitreous cutter, we were able to break the attack of aqueous misdirection and restore anterior chamber formation several times. Unfortunately, aqueous misdirection recurred after each of these treatments, evidently because of blockage of the opening made in the hyaloid face, perhaps by an inflammatory membrane.
Lynch et al. described aqueous misdirection in Pseudophakie eyes and hypothesized on the involvement of an inflammatory reaction in blocking the flow of aqueous across zonules or between the lens capsule and the ciliary processes.26 A similar mechanism may account for the recurrence of aqueous misdirection in our case after hyaloidotomy. Weiss et al. compared pars plana vitrectomy with vitreous aspiration as treatment for aqueous misdirection.27 Aqueous misdirection resolved in nine of nine patients after vitrectomy, but recurred in three of eight patients after vitreous aspiration. This probably was due to more effective disruption of the anterior hyaloid in the vitrectomy group.
As demonstrated by our case, the treatment of aqueous misdirection can be frustrating and accompanied by several recurrences. Aqueous misdirection has occurred after almost every form of intraocular surgery and ophthalmic laser procedure, as well as in eyes with no history of ophthalmic surgery. If medical and laser treatment fail to correct this condition, adequate disruption of the hyaloid face must be achieved during pars plana vitrectomy to prevent recurrence.
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