Since the introduction of the glaucoma drainage device (GDD), the success rate of surgical treatment for refractory glaucoma, such as failed trabeculectomy, neovascular glaucoma, uveitic glaucoma, and glaucoma with wide conjunctival scarring, has improved significantly, compared with conventional trabeculectomy.
Corneal damage after surgery, such as cataract surgery, trabeculectomy, vitrectomy, laser iridotomy, and cyclophotocoagulation, are thought to occur only during treatment. The amount of change is greater and more variable in glaucoma drainage device group than the trabeculectomy group (figure). Moreover, corneal endothelial cell loss after glaucoma drainage device surgery is particularly significant due to its continuity.
Previous studies have reported corneal damage after use of the GDD. McDermott et al. reported endothelial cell loss averaging two cells per mm2 per postoperative month after Molteno implant drainage procedures, but no clinically significant progressive trend in endothelial cell loss was seen in patients undergoing uncomplicated procedures. However, Topouzis et al. reported that the most frequent complication was corneal decompensation or corneal graft failure, and most failures after 12 months of follow-up from Ahmed glaucoma valve (AGV) implantation resulted from corneal complications. The frequency of corneal decompensation after glaucoma implant surgery with long-term (≥ 2 years) follow-up ranged from 5–27%.
A longitudinal study by this team using a baseline preoperative specular microscopic examination reported a cell loss of 10.6% a year after AGV implantation. The second study by this group reported a 15.3% cell loss at 1 year and an 18.6% cell loss at 2 years after AGV implantation. The cell losses at 1 and 2 years after surgery were significantly greater than those of the controls.
This is the third 5-year report stating the endothelial cell loss was significant only up to 2 years after surgery, compared with control eyes without AGV. Although there was a more rapid loss of endothelial cells in the AGV group compared with the control group for 5 years (−7.0%/year and −0.1%/year, respectively; p < 0.001), the average cell loss, measured at the central cornea, decreased with time from −10.7% during the first year to −2.7%/year from 3 years to the final follow up (45.3 ± 20.6 months), and the statistically significant difference compared with the control group was maintained only during the first 2 years after surgery. However, although there was no statistical significance compared to the control eyes, the endothelial cell density decreased 2 years after surgery: −4.2% 2–3 years after surgery and −2.7% 3 years after surgery. Nevertheless, there is a possibility that a prospective study with a larger number of cases may yield different results.
After excluding previous penetrating keratoplasty cases, the cumulative risk of corneal decompensation was 3.3% at 5 years after surgery in uncomplicated cases that did not involve apparent contact between the tube and the cornea. Because the rate of endothelial cell loss remained the same according to this study, regardless of the baseline cell count, patients with low endothelial cell densities before surgery were at a higher risk of corneal decompensation.
Therefore, surgeons must be very careful not to damage the cornea during GDD surgery for the treatment of refractory glaucoma, and all patients treated with the GDD procedure should be monitored for possible corneal problems for more than 2 years.
For patients with low corneal endothelial cell counts or previous penetrating keratoplasty, surgical options other than GDD should first be considered, and the patient warned of possible complications from corneal decompensation.
McDermott ML, Swendris RP, Shin DH, et al. Corneal endothelial cell counts after Molteno implantation. Am J Ophthalmol 1993;115:93–6.
Topouzis F, Coleman AL, Choplin N, et al. Follow-up of the original cohort with the Ahmed glaucoma valve implant. Am J Ophthalmol 1999;128:198–204.
Kim CS, Yim JH, Lee EK, et al. Changes in corneal endothelial cell density and morphology after Ahmed glaucoma valve implantation during the first year of follow up. Clin Experiment Ophthalmol 2008;36:142–7.
Lee EK, Yun YJ, Lee JE, et al. Changes in corneal endothelial cells after Ahmed glaucoma valve implantation: 2-year follow-up. Am J Ophthalmol 2009;148:361–7.
Kim KN, Lee SB, Lee YH, et al. Changes in corneal endothelial cell density and the cumulative risk of corneal decompensation after Ahmed glaucoma valve implantation. Br J Ophthalmol Published Online First: [3/10/2015] doi:10.1136/bjophthalmol-2015-306894
Figure Legend: Scatter plot of the corneal endothelial cell density at baseline and 12 months after trabeculectomy and Ahmed glaucoma valve implantation for treating glaucoma. The amount of change was greater and more variable in Ahmed glaucoma valve implant group than the trabeculectomy group.
TRAB: trabeculectomy, AGV: Ahmed glaucoma valve, CE: corneal endothelial cell (unpublished data)
Kim KN1, Lee SB2, Lee YH2, Lee JJ1, Lim HB1, Kim CS2.[expand title=”Show Affiliations”]
1Department of Ophthalmology, Chungnam National University Hospital, Daejeon, Korea.
2Department of Ophthalmology, Chungnam National University Hospital, Daejeon, Korea Department of Ophthalmology, Chungnam National University College of Medicine, Daejeon, Korea [/expand]
To evaluate changes in the corneal endothelial cell density (ECD) and corneal decompensation following Ahmed glaucoma valve (AGV) implantation.
This study was retrospective and observational case series. Patients with refractory glaucoma who underwent AGV implantation and were followed >5 years were consecutively enrolled. We reviewed the medical records, including the results of central corneal specular microscopy. Of the 127 enrolled patients, the annual change in endothelial cell density (%) was determined using linear regression for 72 eyes evaluated at least four times using serial specular microscopic examination and compared with 31 control eyes (fellow glaucomatous eyes under medical treatment). The main outcome measures were cumulative risk of corneal decompensation and differences in the endothelial cell density loss rates between subjects and controls.
The mean follow-up after AGV implantation was 43.1 months. There were no cases of postoperative tube-corneal touch. The cumulative risk of corneal decompensation was 3.3%, 5 years after AGV implantation. There was a more rapid loss of endothelial cell density in the 72 subject eyes compared with the 31 controls (-7.0% and -0.1%/year, respectively; p<0.001). However, the rate of loss decreased over time and statistical significance compared with control eyes disappeared after 2 years postoperatively: -10.7% from baseline to 1 year (p<0.01), -7.0% from 1 year to 2 years (p=0.037), -4.2% from 2 years to 3 years (p=0.230) and -2.7% from 3 years to the final follow-up (p=0.111).
In case of uncomplicated AGV implantation, the cumulative risk of corneal decompensation was 3.3%, 5 years after the operation. The endothelial cell density loss was statistically greater in eyes with AGV than in control eyes without AGV, but the difference was significant only up to 2 years post surgery.