ABSTRACT

We present patient characteristics and follow-up results of cases with anterior chamber dexamethasone implant migration. The common feature of all six presented cases was vitrectomized eyes. Four of the patients had sutured intraocular lens (IOL) implantation due to complicated cataract surgery, one had combined retinal detachment surgery with sutured IOL implantation, and one had vitrectomy for diabetic intravitreal hemorrhage cleaning and uncomplicated cataract surgery. Anterior chamber implant migration caused corneal edema in all cases and elevated intraocular pressure in three cases. In two cases, the dexamethasone implant was directed into the vitreous cavity after maximum pupillary dilation and corneal manipulation with cotton tip applicator with the patient in reverse Trendelenburg position. There was no other complication until dexamethasone implant degradation, with clear cornea at final examination. In two cases, the implant was removed from the anterior chamber by aspiration, but keratoplasty surgery was planned due to endothelial cell loss and persistent corneal edema during follow-up. In the last two cases, the dexamethasone implant was redirected into the vitreous chamber with a 23-gauge catheter and anterior chamber maintainer but they migrated into the anterior chamber again. In one of these patients, the implant was aspirated by catheter and corneal transplantation was performed due to corneal edema, while the other patient’s implant was redirected into the vitreous chamber with no further anterior migration. The risk of dexamethasone implants migrating into the anterior chamber of vitrectomized eyes and those with sutured IOL implantation should be kept in mind and the patient should be informed and advised to see an ophthalmologist immediately before permanent corneal endothelial damage occurs.

Introduction

Ozurdex (Allergan Inc. Irvine, CA, USA) is a rod-shaped, biodegradable dexamethasone implant 6 mm in length and 0.46 mm in diameter that is injected into the intravitreal cavity using a 22-gauge needle. It is effective in the treatment of macular edema due to retinal vein occlusion, non-infectious uveitis affecting the posterior segment, and diabetic macular edema.^1,2,3 After implantation, the Ozurdex polymer matrix releases 0.7 mg preservative-free dexamethasone into the intravitreal cavity and degrades into lactic acid and glycolic acid. The most common complication reported after dexamethasone implantation is an increase in intraocular pressure, which peaks at about 3 months.^4,5 In addition to the side effects of dexamethasone reported in the literature, such as cataracts and increased intraocular pressure, the implantation procedure itself involves the risk of complications like dislocation to the anterior chamber, corneal endothelial damage, secondary corneal edema, and implantation in the lens.^6,7,8 Migration of a dexamethasone implant into the anterior chamber is a rare complication that can be managed by directing the implant back into the vitreous cavity or removing it from the anterior chamber through a corneal incision.^7,9,10 In this series of six cases, we discuss risk factors, clinical course, and treatment approaches for migration of dexamethasone implants to the anterior chamber.

Discussion

In this study, we present information pertaining to patients who were followed up and treated for dislocation of dexamethasone implants into the anterior chamber. The patients included 3 women and 3 men between the ages of 60 and 79 years. All of the affected eyes were vitrectomized and pseudophakic. One patient (Case 1) had posterior capsule defect, zonular dialysis, and IOL implantation in the sulcus, 4 patients (Cases 2, 4, 5, and 6) had undergone sutured IOL implantation after complicated cataract surgery, and 1 patient (Case 3) had undergone intracapsular IOL implantation with no posterior capsule defect. Anterior chamber migration of a dexamethasone implant is a rare complication and risk factors include previous vitrectomy, aphakic eyes, posterior capsule opening, and lying in prone position.^7,11 Long plane journeys within the first week after dexamethasone implantation were also reported to be a risk factor for anterior chamber dislocation by increasing vitreous pressure due to changes in air pressure.¹² The clinical findings and risk factors of our patients were consistent with the information in the literature. All of our patients had undergone PPV and had posterior capsule defect and/or zonular dialysis.

In the event of a dexamethasone implant in the anterior chamber, the implant can be removed from the anterior chamber via a corneal incision or directed back into the vitreous cavity.¹³ In addition, spontaneous return of the implant to the vitreous cavity has also been reported.¹⁴ The procedure of guiding the implant back into the vitreous cavity by placing the patient in supine position after pupil dilation was first described by Kishore and Schaal.⁹ Mateo et al.¹⁵ reported scleral fixation of the dexamethasone implant using a 10-0 suture. In 2 of our patients with dexamethasone implant in the anterior chamber (patients 2 and 4), the patients were placed in reverse Trendelenburg position after pharmacological dilation and the implant was guided back into the vitreous cavity by manipulating the cornea with a sterile cotton tip applicator. In 2 other patients (patient 3 and patient 5 after first migration), the implant was moved from the anterior chamber back into the vitreous cavity using a 23-G catheter and anterior chamber maintainer. In the patients with severe corneal edema and elevated IOP (patients 1, 6, and 5 after second migration), the dexamethasone implant was removed from the anterior chamber using a 23-G catheter. One of the 2 dexamethasone implants detected in the anterior chamber in patient 1 was implanted in our center, while the other was most likely implanted as a second dose within a short period at another center. This could not be explained conclusively.

Khurana et al.⁷ reported that corneal edema developed when anterior chamber migration occurred within the first 3 weeks after dexamethasone implantation, but did develop in migrations occurring between 5 weeks and 3 months after implantation. All of the patients in our series presented with early migration, within 1 month of implantation, and severe corneal edema was observed in 3 of the patients (patients 1, 5, and 6). Keratoplasty was planned for patient 6 and patient 1, who had 2 implants in the anterior chamber, due to persistent bullous corneal changes and very low endothelial cell counts. Patient 5 underwent keratoplasty due to bullous keratopathy and corneal endothelial failure. The patients who did not develop corneal edema were those who presented to our clinic promptly after onset of their complaints and received rapid intervention.

Kang et al.¹⁶ retrospectively analyzed 924 cases of intravitreal dexamethasone injection. Anterior chamber migration of the implant occurred in 4 patients within 2 to 6 weeks. In 2 patients, the implant was guided back into the vitreous cavity. In the other 2 patients, implant migration occured twice in one and 3 times in the other before the implants were surgically removed. One of the patients underwent keratoplasty. All of the affected eyes lacked posterior capsule integrity.¹⁶ In our case series, 2 dexamethasone implants were detected in the anterior chamber of 1 patient (Case 1). They were removed from the anterior chamber by aspiration using a 23-gauge catheter. Keratoplasty was planned for this patient in the cornea unit because he developed bullous keratopathy and corneal endothelial decompensation. In the case of 2 other patients (Cases 2 and 4), the implant was maneuvered back into the vitreous cavity by applying pressure to the cornea with a sterile cotton tip applicator with the patient in supine position after pupil dilation and reverse Trendelenburg positioning. This resulted in no further problems until implant degradation and the cornea was clear at final examination. In 2 of our patients (Cases 3 and 5), the implant was removed from the anterior chamber and surgically repositioned in the vitreous cavity using a 23-G catheter and anterior chamber maintainer. However, in both patients, repeat migration of the dexamethasone implant was observed. In 1 of these patients (Case 3), the implant was surgically repositioned again with no further problems, while in the other patient (Case 5) explantation was performed using a 23-G catheter. This patient later underwent keratoplasty due to corneal endothelial failure and bullous keratopathy. The implant was also explanted from another patient (Case 6) using a 23-G catheter. Keratoplasty was planned in the cornea unit due to the development of corneal endothelial failure and bullous keratopathy. In all of our patients, the dexamethasone implant migrated into the anterior chamber within 1 to 4 weeks of implantation. Five patients (Cases 1, 2, 4, 5, and 6) lacked posterior capsule integrity and all patients had undergone PPV.

Goncalves et al.¹⁷ retrospectively analyzed 468 patients who received dexamethasone implant injections at multiple centers and determined the prevalence of implant migration to be 1.6%. They also reported a significant relationship between implant migration and cataract surgery (p=0.043), intraocular lens status (p=0.005), and vitrectomy (p=0.057). Öner et al.¹⁸ injected a dexamethasone implant for macular edema in a patient who underwent PPV and scleral-fixated IOL implantation after complicated cataract surgery. Fifteen days after the implantation, the patient exhibited corneal edema and anterior chamber migration of the dexamethasone implant. Explantation was performed, but corneal edema persisted at 4-month follow-up. All of our patients had history of cataract surgery and vitrectomy. Four had sutured intraocular lenses, 1 had an open posterior capsule, zonular dialysis, and a sulcus lens, and 3 patients developed bullous keratopathy.

In cases of anterior chamber dislocation of dexamethasone implants, the implant should be removed or repositioned in the vitreous cavity as soon as possible in order to prevent permanent corneal edema due to corneal endothelial damage. Pupil dilation and reverse Trendelenburg positioning followed by positional guidance of the implant toward the vitreous by cornea manipulation with a sterile cotton tip applicator is a noninvasive procedure that can be used as a first approach in suitable patients. Patients should be advised to avoid long trips and the prone position after dexamethasone implantation and to see an ophthalmologist immediately if they experience any ocular complaints.

Risk factors for anterior chamber migration of dexamethasone implant such as PPV, previous complicated cataract surgery, lack of posterior capsule integrity, and zonular dialysis should be evaluated carefully and implantation should be avoided in patients who are at risk.