Confocal microscopy study of donor-recipient interface after Descemet's stripping with endothelial keratoplasty

To compare corneal confocal microscopy of eyes with Fuchs' endothelial corneal dystrophy after two different endothelial surgeries

PURPOSE

To study the features of corneal confocal microscopy of eyes with Fuchs' endothelial corneal dystrophy (FECD) after successful Descemet stripping automated endothelial keratoplasty (DSAEK) versus Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Thirty-two eyes affected by FECD with corneal oedema requiring a corneal graft were treated with DSAEK (15 eyes) or DMEK (17 eyes). All patients underwent in vivo corneal confocal microscopy (IVCCM) at 6 months postoperatively. We evaluated preoperative and postoperative corrected distance visual acuity (CDVA) and the correlation with IVCCM characteristics.

RESULTS

Using IVCCM, Z-scan curve analysis showed similar subepithelial reflectivity peaks between the two groups (DSAEK 1256 SU ± 514 vs DMEK 1118 SU ± 408, p = 0.411), while the interface reflectivity was significantly higher in the DMEK group (1511 SU ± 357) than in the DSAEK group (1029 SU ± 413, p = 0.002).

CONCLUSION

Comparing the corneal confocal microscopic characteristics after DMEK with those after DSAEK and their correlation with visual outcome at 6 months, we hypothesized that the presence of a third reflectivity peak in the Z-scan curves of DSAEK patients could justify the poorer visual outcome with this endothelial surgery than with DMEK.

Diseases of the corneal endothelium

The corneal endothelial monolayer and associated Descemet's membrane (DM) complex is a unique structure that plays an essential role in corneal function. Endothelial cells are neural crest derived cells that rest on a special extracellular matrix and play a major role in maintaining stromal hydration within a narrow physiologic range necessary for clear vision. A number of diseases affect the endothelial cells and DM complex and can impair corneal function and vision. This review addresses different human corneal endothelial diseases characterized by loss of endothelial function including: Fuchs endothelial corneal dystrophy (FECD), posterior polymorphous corneal dystrophy (PPCD), congenital hereditary endothelial dystrophy (CHED), bullous keratopathy, iridocorneal endothelial (ICE) syndrome, post-traumatic fibrous downgrowth, glaucoma and diabetes mellitus.

Evaluation of interface reflectivity and corneal aberrations following Descemet's stripping automated endothelial keratoplasty

PURPOSE:

This study aims to evaluate visual outcome after Descemet's membrane stripping automated endothelial keratoplasty (DSAEK) and relate to interface and corneal higher-order aberrations (HOAs).

MATERIALS AND METHODS:

We enrolled 16 eyes of 16 patients (eight males and eight females) in this interventional case series and followed DSAEK operation for about two to 20 months. OCULUS Pentacam, as well as other ophthalmic evaluations in follow-up visits, examined interface reflectivity and HOAs. Statistical relations were analyzed.

RESULTS:

There was statistically significant correlation between interface reflectivity and best corrected visual acuity (BCVA) (r = 0.56, P = 0.021). Pachymetry (central corneal thickness) and BCVA had a moderate correlation (r = 0.6, P = 0.013). There was no statistically significant correlation between pachymetry and follow-up time (r = −0.36, P = 0.16). Negative correlation between follow-up and interface reflectivity was also not statistically significant (r = −0.24, P = 0.35). Coma had a significant correlation with BCVA in cornea and cornea front maps (r = 0.74, P = 0.009 and r = 0.71, P = 0.013, respectively).

CONCLUSION:

Significant correlation between interface reflectivity and BSCVA was found, and anterior corneal HOAs are significantly higher than posterior HOAs.

Descemet stripping automated endothelial keratoplasty in Fuchs' corneal endothelial dystrophy: anterior segment optical coherence tomography and in vivo confocal microscopy analysis

Background

To evaluate the in vivo corneal changes using in vivo confocal microscopy (IVCM) and anterior segment optical coherence tomography (AS-OCT) in patients with Fuchs’ dystrophy who underwent Descemet stripping automated endothelial keratoplasty (DSAEK) and the relationship between these changes and the postoperative visual recovery up to 1-year follow-up.

Methods

Before DSAEK and 1 day, 3, 6 and 12 months after surgery 31 patients (39 pseudophakic eyes) underwent a complete ophthalmological evaluation including best corrected visual acuity (BCVA), IVCM (subepithelial haze, interface haze, graft thickness) and AS-OCT (graft thickness).

Results

Graft thickness measurements by AS-OCT were strongly correlated to those obtained using IVCM at every follow-up stage (intraclass correlation coefficient = 0.95 to 0.97 between 3 and 12 months, P < 0.001 for all coefficients). No correlation between BCVA and graft thickness measured by AS-OCT at any follow-up stage was found, while at 3 and 6 postoperative months the correlations between BCVA and preoperative subepithelial haze (r = 0.61, P < 0.001 and r = 0.46, P = 0.002), interface haze (r = 0.51, P < 0.001 and r = 0.46, P = 0.003), postoperative subepithelial haze (r = 0.43, P = 0.004 and r = 0.39, P = 0.001) were significant.

Conclusions

The study confirmed corneal subepithelial haze and interface haze as important factors limiting visual acuity after DSAEK, while graft thickness was not related to BCVA.

[Corneal examination in patients with bullous keratopathy before and after endothelial keratoplasty]

OBJECTIVE

To evaluate corneal status in patients with bullous keratopathy before and after endothelial keratoplasty.

MATERIAL AND METHODS

A total of 16 patients (18 eyes) with bullous keratopathy were examined before and after DSAEK. Confocal microscopy ("Nidek", Japan) was used for corneal status evaluation.

RESULTS

Follow-up examinations were performed 3, 6, and 24 months after the surgery. In all patients minor corneal opacity persisted for the whole follow-up period but tended to decrease. It is shown that visual acuity is most dependent on light scattering in the anterior stroma.

CONCLUSION

Anterior stromal haze is shown to have greater impact on visual acuity than opacities, folds, and birefringent deposits within the host-donor interface. Duration of bullous keratopathy, patient's age, and comorbidity are the factors that influence anterior and deep stromal haze development and changes over time.

Optimizing outcomes with Descemet's membrane endothelial keratoplasty

PURPOSE OF REVIEW

To review recent advances in posterior lamellar keratoplasty and to describe strategies that enhance the outcome of Descemet's membrane endothelial keratoplasty (DMEK) and should lead to a more widespread use of this technique.

RECENT FINDINGS

DMEK offers significant advantages over Descemet's stripping automated endothelial keratoplasty (DSAEK) such as less immune reaction and better visual acuity because of less higher order aberrations. Donor selection should exclude donors under 50 years because of tissue elasticity; several advanced techniques now allow donor preparation from both cold and organ-cultured tissue in about 99% minimizing the risk of graft loss. Oversizing the area of Descemet's stripping in relationship to graft size enhances graft attachment and use of a standardized approach for graft delivery. Air bubble-driven nontouch unfolding techniques and, possibly, gas tamponade in the anterior chamber further enhance graft attachment and reduce surgery-induced endothelial cell loss. Graft orientation is made earlier by marking, slit beam and optical coherence tomography. Novel understanding of the functional anatomy of Descemet's membrane as well as migration of endothelial cells will allow to further refine DMEK and improve its outcome.

SUMMARY

Although the superiority of DMEK over Descemet's stripping automated endothelial keratoplasty in terms of safety and functionality had been further elucidated, remarkable progress has been made in the recent past regarding tissue preparation, insertion and intraoperative manipulation that will foster the more widespread use of DMEK among corneal surgeons.

In vitro pilot analysis of uniformity, circularity, and concentricity of DSAEK donor endothelial grafts prepared by a microkeratome

PURPOSE

The aim of this study was to analyze Descemet stripping automated endothelial keratoplasty donor endothelial grafts, prepared by using a microkeratome, in terms of uniformity, circularity, and concentricity.

METHODS

In this pilot study, 12 human donor corneas were prepared by means of a microkeratome and imaged using the Visante anterior segment optical coherence tomography along 4 meridians. The microkeratome enters and exits the corneal tissue at an angle, creating a donor graft bed with a uniform stromal (US) thickness in between the angled edges. We termed the angled portion the "nonuniform stromal transitional annulus" (STA), the point of entry and exit of the microkeratome the "epithelium-to-epithelium" (E-E) diameter, and the length of the US bed the "US" diameter. The E-E and US diameters were measured to create a model of each donor graft, from which circularity and concentricity were calculated. The STA length and height were measured, and the slope was calculated.

RESULTS

The mean E-E diameter was 10.69 ± 0.32 mm (range, 9.46-11.75 mm) and the mean US diameter was 8.96 ± 0.40 mm (range, 7.62-10.28 mm). The microkeratome generated elliptical rather than circular cuts, with a mean eccentricity of 0.34 ± 0.098 (range, 0.22-0.58). Eccentricity values between 0 and 1 represent ellipses, with zero characterizing a circle. The US ellipses and E-E ellipses were not concentric, with a mean deviation of the centers of the shapes of 177.06 ± 92.06 μm (range, 21.95-322.22 μm). The mean STA length was 0.73 ± 0.31 mm (range, 0.25-1.89 mm), the mean height was 0.43 ± 0.08 mm (range, 0.28-0.64 mm), and the mean slope was 34.11 ± 14.00° (range, 8.43-53.67°).

CONCLUSIONS

Microkeratome cuts created nonuniform, noncircular nonconcentric donor grafts. Asymmetry and nonuniformity of donor tissue may help explain suboptimal visual outcomes.

Correlation between visual acuity and interface reflectivity measured by pentacam following DSAEK

PURPOSE

Descemet-stripping automated endothelial keratoplasty (DSAEK) is an advanced method of lamellar endothelial keratoplasty. In comparison with penetrating keratoplasty, visual rehabilitation seems to be faster. Final visual outcome of DSAEK, however, seems to be limited, especially in comparison with Descemet membrane endothelial keratoplasty (DMEK). DSAEK cases without graft failure often do not show any definite correlate for the reduced optical performance. In this study, we tried to correlate visual acuity following DSAEK with interface reflectivity as measured by a rotating Scheimpflug system.

METHODS

We examined 14 eyes of 13 patients with the pentacam for 2-11 months following DSAEK. Reflectivity of the interface region in the centre of the optical axis as well as central corneal thickness was determined. Statistical correlation between interface reflectivity and best spectacle-corrected visual acuity, central corneal thickness and follow-up time was drawn (multifactorial linear regression analysis).

RESULTS

Statistically significant correlation between interface reflectivity and BSCVA as well as follow-up time was found. Reflectivity was highest in regions of interface (metal) particles. There was no statistically significant correlation between interface reflectivity and central corneal thickness.

CONCLUSION

We present a measurable correlate for reduced visual outcome following DSAEK despite a clear graft. Inverse correlation between interface reflectivity and best spectacle-corrected visual acuity (BSCVA) indicates that irregularities or scarring in the interface region may influence the optical quality following DSAEK.

Interface haze associated with topical nonsteroidal anti-inflammatory drug use after descemet stripping automated endothelial keratoplasty

PURPOSE

To determine if topical nonsteroidal anti-inflammatory drug (NSAID) use after Descemet stripping automated endothelial keratoplasty (DSAEK) is associated with the development of interface haze.

METHODS

A retrospective case-control study of patients undergoing DSAEK surgery.

RESULTS

Of the 61 patients receiving topical NSAIDs, 51% were noted to develop interface haze, and 9% of the control group (N=100, no NSAID) developed haze. There was no significant difference in best corrected visual acuity between the 2 groups.

CONCLUSIONS

Topical NSAID use is associated with the development of interface haze, although it may not be visually significant and could be related to confounding factors.

[Relationship between donor-receptor interface and visual acuity in DSAEK]

OBJECTIVE

To evaluate the relationship between best corrected visual acuity and donor-recipient interface resulting after Descemet's Stripping with Automated Endothelial Keratoplasty (DSAEK).

METHODS

Retrospective review of 46 clinical histories after DSAEK intervention in which 22 patients who fulfilled the inclusion criteria (two with bilateral DSAEK), were studied. All were operated on by the same ophthalmologist from January 2010 until April 2011. Surgical indications were: 19 (72.2%) bullous keratopathy, 3 (12.5%) Fuchs endothelial dystrophy, and 2 (8.3%) previous failed keratoplasty. The visual acuity (VA) was recorded preoperatively, and at three and six months after the operation; the latter two being compared with the interface between donor and recipient after DSAEK measured in a Scheimpflug corneal topography camera (Pentacam(®) model).

RESULTS

After DSAEK surgery 19 eyes had improved visual acuity at three months, and 20 eyes at six months (P<.001). This improvement was compared with the decrease in optical density of the resulting donor-receptor interface, with apositive and significant relationship being found between them (Rho interface 3 months, and improved AV 6 months 0.44, P<.001). However, the interface is negatively and significantly related with visual acuity (Rho 3 m: -0.41, P=.045). Also, patients who had a denser stroma had a worse postoperative visual acuity in relative terms when compared with those who had a less damaged stroma.

CONCLUSIONS

Patients undergoing DSAEK with worse preoperative visual acuity had a greater improvement visual in absolute values and however, they may have achieved a lower relative visual acuity than could be related to a higher refractive interface, as a result of a more damaged preoperative corneal stroma.

Identifying causes for poor visual outcome after DSEK/DSAEK following secondary DMEK in the same eye

PURPOSE

To identify causes of reduced visual acuity after Descemet stripping (automated) endothelial keratoplasty (DSEK/DSAEK) and to determine whether such eyes can be successfully 'repaired' with a secondary Descemet membrane endothelial keratoplasty (DMEK).

METHODS

Twelve eyes of 12 patients, who underwent secondary DMEK to manage poor visual outcome after initial DSEK/DSAEK, were evaluated with biomicroscopy, Pentacam imaging, and specular and confocal microscopy, before and at 1, 3 and 6 months after DMEK.

RESULTS

Four causes of reduced optical quality of the transplanted host cornea could be identified in DSEK/DSAEK: five eyes (42%) showed large host-Descemet remnants within the visual axis during surgery; six eyes (50%) irregular graft thickness; six eyes subtle 'stromal waves'; and nine eyes (75%) high reflectivity at the donor-to-host interface. After DMEK graft replacement, all corneas cleared and achieved a best corrected visual acuity of ≥20/25 (≥0.8), except for one with a partial Descemet graft detachment. Pachymetry values decreased from 670 (±112) μm before to 517 (±57) μm after secondary DMEK. Higher-order aberrations (Coma and Trefoil) at the posterior surface tended to be lower (p = 0.07) in DMEK grafts than in DSEK/DSAEK grafts.

CONCLUSION

Host-Descemet remnants at the donor-to-host interface, interface reflectivity, graft thickness irregularity and donor stromal contraction may contribute to poor visual outcome after DSEK/DSAEK, without causing permanent host corneal damage, as in most cases, complete visual recovery could be achieved by performing a secondary DMEK.

In vivo evaluation of DSAEK interface with scanning-laser confocal microscopy

BACKGROUND

Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) allows selective replacement of the endothelium. Post-operative haze and particles can affect the interface quality and, ultimately, visual outcome. In this study, we evaluated DSAEK interface with in vivo laser confocal microscopy (LCM) in order to: (i) correlate interface status with best corrected visual acuity, and (ii) with time from surgery; (iii) correlate interface particle number with best corrected visual acuity. Host-donor interface was imaged and graded using a published reflectivity scale. Particles at the interface were counted.

METHODS

18 eyes of 16 patients (6 males and 10 females); mean age: 74 ± 8.3 years which underwent DSAEK were examined by means of in vivo laser confocal microscopy between 1 and 24 months after surgery. Host-donor interface was imaged and graded using a published reflectivity scale. Particles present at the interface were counted.

RESULTS

Interface reflectivity was 2.17 ± 1.2 and significantly correlated with visual acuity (Spearman correlation coefficient -0.83; P < 0.001), and with time after surgery (Spearman correlation coefficient -0.87; P < 0.001). Visual acuity was 0.67 ± 0.27. The number of particles was 205 ± 117.8; no correlation was found between this number and visual acuity (Spearman correlation coefficient -0.41; P = 0.15).

CONCLUSION

DSAEK interface imaged with LCM is helpful in diagnosing poor host-donor interface quality in DSAEK surgery. A good quality interface is related to a better visual acuity. Moreover, the quality of the interface appears to improve as time passes from the surgery. Interface quality is related with visual acuity and improves with time from surgery. LCM should be considered as an added tool in post-DSAEK follow-up of patients. Finally, our study shows that the presence of particles does not influence visual outcome.

Corneal transplantation

Corneal transplantation or keratoplasty has developed rapidly in the past 10 years. Penetrating keratoplasty, a procedure consisting of full-thickness replacement of the cornea, has been the dominant procedure for more than half a century, and successfully caters to most causes of corneal blindness. The adoption by specialist surgeons of newer forms of lamellar transplantation surgery, which selectively replace only diseased layers of the cornea, has been a fundamental change in recent years. Deep anterior lamellar keratoplasty is replacing penetrating keratoplasty for disorders affecting the corneal stromal layers, while eliminating the risk of endothelial rejection. Endothelial keratoplasty, which selectively replaces the corneal endothelium in patients with endothelial disease, has resulted in more rapid and predictable visual outcomes. Other emerging therapies are ocular surface reconstruction and artificial cornea (keratoprosthesis) surgery, which have become more widely available because of rapid advances in these techniques. Collectively, these advances have resulted in improved outcomes, and have expanded the number of cases of corneal blindness, which can now be treated successfully. Femtosecond-laser-assisted surgery, bioengineered corneas, and medical treatment for endothelial disease are also likely to play a part in the future.

Ultrastructural and in vivo confocal microscopic evaluation of interface after Descemet's Stripping Endothelial Keratoplasty in rabbits

PURPOSE

To study healing at the donor-recipient interface after Descemet's Stripping Endothelial Keratoplasty (DSEK) in rabbits by ultrastructural and in vivo confocal microscopic evaluation.

METHODS

The right eye of eight New Zealand White rabbits underwent DSEK. Postoperatively, each rabbit was subjected to routine slitlamp examination daily for 2 weeks and then weekly for 6 weeks. In vivo confocal microscopic evaluation was performed at 1, 2, 4 and 8 weeks. Two rabbits were randomly chosen at 1, 2, 4 and 8 weeks for transmission electron microscopic examination.

RESULTS

Interface haze decreased with each follow-up visit. Activated keratocytes and associated cellular processes were evident throughout all the follow-ups with in vivo confocal microscopy. Highly reflective particles were left at the interface until the end-point of the study. Upon ultrastructural evaluation, increased rough-surface endoplasmic reticulum in keratocytes, clefts, folds and retained Descemet's membrane (DM) were found.

CONCLUSION

Clefts lack of adherence at the interface and degenerated keratocyte may make up the highly reflective particles. In addition, retained DM does not appear to affect adhesion and very minimal healing is produced at the DM-stroma smooth interface, which permits better quality of vision in Descemet's membrane endothelial keratoplasty.

In vivo and in vitro analysis of topographic changes secondary to DSAEK venting incisions

INTRODUCTION

Descemet's stripping automated endothelial keratoplasty (DSAEK) venting incisions may induce irregular corneal astigmatism. The study examines in vivo and in vitro astigmatic effects of venting incisions.

PATIENTS AND METHODS

In vivo analysis examined eleven eyes of eleven patients who had received DSAEK with venting incisions. A chart review of the eleven eyes including assessment of pre and postoperative refraction and topography was performed. In vitro analysis examined three cadaver eyes which received topographic imaging followed by venting incisions at 4 mm, 6 mm, and 7 mm optical zones. Topographic imaging was then performed again after the incisions.

RESULTS

Postoperative topographies of eleven eyes demonstrated localized flattening at incision sites and cloverleaf pattern astigmatism. There was a significant difference in corneal irregularity measurement (P = 0.03), but no significant difference in shape factor or change of topographic cylinder. The cloverleaf pattern was found in cadaver eyes with incisions placed at 4 mm and 6 mm optical zones but not at the 7 mm zone.

CONCLUSION

DSAEK venting incisions can cause irregular corneal astigmatism that may affect visual outcomes. The authors recommend placement of venting incisions near the 7 mm optical zone.

Ultra-thin donor tissue preparation for endothelial keratoplasty with a double-pass microkeratome

PURPOSE

To quantify and describe practically a novel technique for donor tissue preparation in Descemet stripping endothelial keratoplasty to approach the superior visual outcomes of Descemet membrane endothelial keratoplasty.

DESIGN

Experimental laboratory investigation.

METHODS

SETTING

Institutional.

STUDY POPULATION

Eleven human donor corneas.

INTERVENTION

Double-pass of microkeratome over donor corneas-first with a thicker cutting depth and subsequently with a thinner cutting depth.

MAIN OUTCOME MEASURES

Donor tissue profiles and residual bed thicknesses.

RESULTS

After the first pass of the microkeratome, the average cut thickness using the 250-μm cutting head was 342.5 ± 14.8 μm (range, 332 to 353 μm), that using the 300-μm head was 343.8 ± 39.2 μm (range, 315 to 411 μm), and that with the 350-μm head was 467.7 ± 50.1 μm (range, 419 to 519 μm). We used the 200-μm cutting head only once with a cut depth of 210 μm. For the second pass, when using the 110-μm head, the cutting depth averaged to 167.8 ± 28.8 μm (range, 133 to 203 μm). The 130-μm cutting head yielded a cut depth of 199.7 ± 24.4 μm (range, 180 to 227 μm). Two corneas were perforated during the second pass. The average final thickness of the residual bed was 121 ± 32.2 μm (range, 52 to 160 μm).

CONCLUSIONS

Double-pass harvest for ultra-thin Descemet stripping automated endothelial keratoplasty could improve optical outcomes by obtaining donor Descemet stripping automated endothelial keratoplasty tissue with thinner residual beds. Further studies are needed with larger sample sizes to establish algorithms for appropriate cutting head thickness in each pass. Potential additional endothelial cell loss with the second pass of the microkeratome also should be evaluated.