Purpose
To determine the various causes of unexpected incomplete visual rehabilitation at 6 months postoperative after Descemet membrane endothelial keratoplasty (DMEK).
Design
Retrospective study of prospectively collected data at a tertiary referral center.
Methods
From a larger group of 400 consecutive DMEK surgeries, the last 200 consecutive eyes were reviewed for visual discomfort despite a best-corrected visual acuity (BCVA) of ≥20/25 (≥0.8) or unexpected subnormal BCVA (≤20/28; ≤0.7) at 6 months after DMEK. Biomicroscopy, funduscopy, Pentacam imaging, noncontact specular microscopy, anterior segment optical coherence tomography, and surgical videos were used to determine the causes of incomplete visual rehabilitation.
Results
A total of 69 eyes out of 178 eyes that were included in the analysis (38.8%) presented with incomplete visual rehabilitation after DMEK, further categorized as “primarily patient-related” in 40 of 178 (22.5%), “primarily graft-related” in 21 of 178 (11.8%), and a combination of “patient-/graft-related” in 8 of 178 cases (4.5%). Unrecognized pre-existing ocular pathology and/or posterior segment disease in 19 of 178 eyes (10.7%), clinically significant corneal irregularities and/or central corneal scarring often secondary to long-standing preoperative corneal edema in 14 of 178 eyes (7.9%), or (partial) graft detachment in 20 of 178 eyes (11.2%) were the main causes of unexpected incomplete visual rehabilitation. Transient or persistent monocular ghost images or diplopia occurred in 10 of 178 eyes (5.6%), sometimes requiring contact lens fitting.
Conclusions
In contrast to earlier endothelial keratoplasty techniques that may frequently be associated with undefined transplant-related subnormal visual outcomes, incomplete visual rehabilitation after DMEK may virtually always be explained by concomitant ocular pathology or evident graft failure.
Since 1998, we have introduced various techniques for endothelial keratoplasty, popularized as “deep lamellar endothelial keratoplasty” (DLEK), Descemet stripping (automated) endothelial keratoplasty (DSEK/DSAEK), and Descemet membrane endothelial keratoplasty (DMEK), a method for selective transplantation of Descemet membrane (DM) through a clear corneal tunnel incision. Although the visual outcome in endothelial keratoplasty may compare favorably to penetrating keratoplasty (PK), DLEK and DSEK/DSAEK may not always give full visual recovery. Despite the elimination of irregular astigmatism as the main optical complication after PK, with these procedures the optical quality of the cornea may be compromised owing to rather undefined irregularities in the donor posterior stroma and/or the host-to-donor stromal interface.
In contrast, clinical experience suggests that recovery to the eye’s full visual potential may be obtained after DMEK, with up to 80% of eyes reaching a best-corrected visual acuity (BCVA) of 20/25 (0.8) or better within 6 months after surgery. If so, incomplete visual recovery (BCVA ≤20/28; ≤0.7) in the remaining eyes should let itself be explained by identifiable causes. In other words, low visual outcome after DMEK would require further diagnostic evaluation, since it cannot be attributed to undefined imperfections in optical quality as in DSEK/DSAEK.
In the current study, we reviewed 200 consecutive DMEK cases to test this hypothesis, in order to define causes of incomplete visual recovery after DMEK, to further reduce the risk of unexpected low visual outcome after DMEK, and to define guidelines for surgeons to improve their clinical outcome in endothelial keratoplasty.
Methods
From a larger group of 400 consecutive DMEK surgeries, the last 200 consecutive operated eyes (181 patients, 76 male and 105 female, ranging from 20-90 years in age; average age 67.1 ± 13.2 years) were reviewed for subjective visual complaints despite a BCVA of ≥20/25 (≥0.8) or unexpected low visual outcome (BCVA ≤20/28 [≤0.7]) at 6 months after DMEK. These 200 consecutive surgeries were performed between March 30, 2010 and October 25, 2011. The retrospective study of prospectively collected data with patient informed consent for research participation was conducted in compliance with the Institutional Review Board and Informed Consent requirements, in adherence to the tenets of the Declaration of Helsinki, at the Netherlands Institute for Innovative Ocular Surgery. The study was submitted to http://www.clinicaltrials.gov (Study registration NCT00521898 ).
Indications for DMEK were Fuchs endothelial dystrophy (169/200 eyes), bullous keratopathy (BK) (24/200 eyes: pseudophakic or aphakic bullous keratopathy [21], buphthalmos [2], and corneal trauma [1]), low visual outcome with clear cornea after DSEK/DSAEK (6/200 eyes), and posterior polymorphous dystrophy (1/200) ( Table 1 ).
| Indication for Surgery | Total (n = 200) | Excluded (n = 22) | Included (n=178) | |||||
|---|---|---|---|---|---|---|---|---|
| Low Visual Potential b (n = 17) | Lost to Follow-up (n = 5) | Total (n = 178) | Complete Visual Rehabilitation c (n = 109) | Incomplete Visual Rehabilitation d (n = 69) | ||||
| BK | 24 | 8 | 1 e | 15 | 6/15 | (40%) | 9/15 | (60%) |
| DSEK/DSAEK a | 6 | 0 | 1 | 5 | 3/5 | (60%) | 2/5 | (40%) |
| PPMD | 1 | 0 | 0 | 1 | 0/1 | (0%) | 1/1 | (100%) |
| FED | 169 | 9 | 3 e | 157 | 100/157 | (64%) | 57/157 | (36%) |
a Low visual outcome after DSEK/DSAEK.
b Eyes with low visual potential diagnosed before DMEK surgery.
c Eyes reaching a best-corrected visual acuity (BCVA) of ≥0.8 and presenting no visual complaints.
d Eyes reaching a BCVA of ≤0.7 or reaching ≥0.8 and presenting visual complaints.
e Two patients required a secondary transplantation at 1 month and at 4 months after DMEK. Indications for DMEK in these cases were BK and FED, respectively.
Out of the 200 patients, a total of 69 eyes (68 patients, 28 male and 40 female, ranging from 30-90 years in age; average age 69.2 ± 14.2 years) showed visual discomfort or incomplete visual recovery, and were further evaluated.
Donor Tissue
From donor globes, corneoscleral buttons were excised less than 36 hours postmortem and stored by organ culture in modified minimum essential medium (EMEM) at 31°C. After 1 week of culture, endothelial cell morphology and viability were evaluated and the corneoscleral buttons were mounted endothelial side up on a custom-made holder with a suction cup. DM was stripped off from the posterior stroma, so that a 9.5-mm-diameter flap of posterior DM with its endothelial monolayer was obtained. Owing to the elastic properties of the membrane, a “Descemet roll” formed spontaneously, with the endothelium at the outer side. Each Descemet roll was then stored “free-floating” in organ culture medium until the time of transplantation (ie, after another 5-10 days).
Surgery
In recipient eyes, a 3.0 mm tunnel incision was made just within the limbus, entering the anterior chamber. With an inverted Sinskey hook (D.O.R.C. International, Zuidland, Netherlands) and/or Descemet scraper (D.O.R.C. International), a circular portion of DM was scored and stripped from the posterior stroma with a complete air-fill of the anterior chamber, so that a 9.0-mm-diameter “descemetorhexis” was created, and the central portion of DM was removed from the eye.
The donor Descemet roll was stained with a 0.06% trypan blue solution (VisionBlue; D.O.R.C. International) and sucked into a custom-made glass injector (DMEK inserter; D.O.R.C. International). Using the injector, the donor Descemet roll was inserted into the anterior chamber and the graft was oriented endothelial side down (donor DM facing recipient posterior stroma) by careful, indirect manipulation of the tissue with air and fluid. While maintaining the anterior chamber with fluid and air, the graft was gently spread out over the iris. Then, an air bubble was injected underneath the donor DM to position the tissue onto the recipient posterior stroma. The anterior chamber was completely filled with air for 60 minutes followed by an air-liquid exchange to pressurize the eye. Each surgical procedure was recorded on DVD (Pioneer DVR-RT601H-S; Pioneer, Tokyo, Japan).
Data Analysis
Before and at 1 day, 1 week, and 1, 3, and 6 months after surgery, subjective refraction, BCVA, biomicroscopy, and funduscopy were documented. Scheimpflug imaging and topography (Pentacam; Oculus, Wetzlar, Germany), noncontact specular microscopy (Topcon Medical Europe BV, Capelle a/d IJssel, The Netherlands), and anterior segment optical coherence tomography (OCT) (Slit-lamp OCT; Heidelberg Engineering, Heidelberg, Germany) were performed, and slit-lamp photographs (Topcon Medical Europe BV) were taken. Surgical videos were reviewed and intraoperative and/or postoperative complications were recorded. All data were collected and evaluated using a SQL database.
Results
Causes of Incomplete Visual Rehabilitation After Descemet Membrane Endothelial Keratoplasty
From a total of 200 DMEK eyes, 22 were excluded from analysis ( Table 1 ): 17 had low visual potential diagnosed prior to surgery, and for 5 eyes the 6-month examination was not available (3 were lost to follow-up, but presented functional grafts in the recorded visits; and 2 underwent a secondary corneal transplant at 1 and at 4 months after DMEK, respectively).
Of the remaining 178 eyes, a total of 69 eyes (38.8%) showed visual discomfort or incomplete visual recovery, and were further evaluated.
The causes of incomplete visual rehabilitation could roughly be categorized as “primarily patient-related” factors in 40 of 178 eyes (22.5%) and “primarily graft-related factors” in 21 of 178 eyes (11.8%); in addition, 8 of 178 eyes (4.5%) showed a combination thereof ( Figure 1 , Table 2 ).
| n (Total n = 178) | % | |
|---|---|---|
| Patient-related | ||
| Maculopathy | 17/178 | 9.6 |
| Corneal irregularities/scarring | 14/178 | 7.9 |
| Diplopia/ghost images | 10/178 | 5.6 |
| Cataract | 5/178 | 2.8 |
| High myopia | 3/178 | 1.7 |
| Glaucoma | 2/178 | 1.1 |
| PCO | 2/178 | 1.1 |
| Diabetic retinopathy | 1/178 | 0.6 |
| Opticopathy | 1/178 | 0.6 |
| DM remnants | 1/178 | 0.6 |
| (− 8 [eyes with 2 patient-related factors]) | −8 | |
| Total no. of eyes a | 48/178 | (27) |
| Graft-related | ||
| (Partial) graft detachment >1/3 | 12/178 | 6.7 |
| Partial graft detachment <1/3 | 8/178 | 4.5 |
| Delayed graft function | 9/178 | 5.1 |
| Total no. of eyes a | 29/178 | 16.3 |
a A total of 8 of 178 eyes (4.5%) presented a combination of donor- and patient-related factors; 40 of 178 eyes (22.5%) showed only patient-related and 21 of 178 eyes (11.8%) only graft-related factors.
Of the 178 eyes, 109 (61.2%) presented a BCVA of ≥20/25 (≥0.8) and no visual complaints, 12 (6.7%) had visual complaints in the presence of a BCVA of ≥20/25 (≥0.8), 38 (21.3%) had a BCVA between ≤20/28 (≤0.7) and ≥20/40 (≥0.5), and 19 (10.7%) had a BCVA ≤20/50 (≤0.4).
“Patient-related” factors
The most common “patient-related” cause for incomplete visual rehabilitation after DMEK was macular pathology (17/178 eyes; 9.6%), with visual acuities ranging from counting fingers (1/60) to 20/28 (0.7). Age-related macular degeneration (ARMD) and/or changes in the retinal pigment epithelium (RPE) were diagnosed in 13 of 178 cases (7.3%), macular pucker was diagnosed in 3 of 178 cases (1.7%), and cystoid macular edema was diagnosed in 1 case (0.6%). Of these 17 eyes with a maculopathy, 7 eyes were diagnosed with an additional reason for a low visual outcome: anterior corneal irregularities were found in 2 eyes ( Figure 2 ), 1 eye showed a paracentral Descemet membrane remnant at the donor-to-host interface ( Figure 3 , Top), and 4 eyes had a (partial) graft detachment ( Figure 1 ).
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