Pre-Descemet Endothelial Keratoplasty Research Articles

Relationship of posterior peripheral corneal layers and the trabecular meshwork: an immunohistological and anatomical study

Background/AimWith the popularity of endothelial keratoplasty (EK) procedures, Descemet membrane (DM) EK and pre-Descemet EK, considerable work has been done on understanding the posterior corneal anatomy. Most of the information...

Optimized Kalinnikov-Dinh technology for effective pre-Descemet's endothelial keratoplasty (PDEK) graft preparation and preservation.

We report an optimized Kalinnikov-Dinh technology for pre-Descemet's endothelial keratoplasty (PDEK) that involves the use of a ring fixator, base, 30G needle connected to a 5-ml syringe with a spring-loaded plunger, and storage media. Our method allows to minimize graft preparation failure and preserves the PDEK graft efficiently, by reducing complications associated with the formation of type 1 big bubbles, including bubble rupture, perforation of Descemet's membrane and endothelium, and formation of type 2 or mixed type of big bubbles, and may contribute to increasing the number of surgeons performing PDEK around the globe.

The pre-Descemet's layer (Dua's layer, also known as the Dua-Fine layer and the pre-posterior limiting lamina layer): Discovery, characterisation, clinical and surgical applications, and the controversy.

The pre-Descemet's layer/Dua's layer, also termed the Dua-Fine layer and the pre-posterior limiting lamina layer, lies anterior to the Descemet's membrane in the cornea, is 10 μm (range 6-16) thick, made predominantly of type I and some type VI collagen with abundant elastin, more than any other layer of the cornea. It has high tensile strength (bursting pressure up to 700mm of Hg), is impervious to air and almost acellular. At the periphery it demonstrates fenestrations and ramifies to become the core of the trabecular meshwork, with implications for intraocular pressure and glaucoma. It has been demonstrated in some species of animals. The layer has assumed considerable importance in anterior and posterior lamellar corneal transplant surgery by improving our understanding of the behaviour of corneal tissue during these procedures, improved techniques and made the surgery safer with better outcomes. It has led to the innovation of new surgical procedures namely, pre-Descemet's endothelial keratoplasty, suture management of acute hydrops, DALK-triple and Fogla's mini DALK. The discovery and knowledge of the layer has introduced paradigm shifts in our age old concepts of Descemet's membrane detachment, acute corneal hydrops in keratoconus and Descemetoceles, with impact on management approaches. It has been shown to contribute to the pathology and clinical signs observed in corneal infections and some corneal dystrophies. Early evidence suggests that it may have a role in the pathogenesis of keratoconus in relation to its elastin content. Its contribution to corneal biomechanics and glaucoma are subjects of current investigations.

Outcomes of Pre-Descemet Endothelial Keratoplasty for Failed Therapeutic Penetrating Keratoplasty.

The aim of this study was to analyze the outcomes of pre-Descemet endothelial keratoplasty (PDEK) for failed therapeutic penetrating keratoplasty. This was a retrospective, interventional study that involved 12 eyes of 12 patients with failed therapeutic penetrating keratoplasty that underwent PDEK. All cases had a minimum follow-up of 12 months. The main outcome measures were best-corrected visual acuity, graft clarity, endothelial cell density loss, and graft survival. Corneal clarity was graded on a scale from 0 to 4, where grade 4 denoted an absolutely clear cornea and grade 0 denoted a totally opaque cornea. Three cases underwent PDEK, 6 cases PDEK with phacoemulsification, and 3 cases underwent PDEK with pupilloplasty. The mean follow-up period for all cases was 18.5 ± 4.9 months. The mean preoperative and postoperative best-corrected visual acuity (in Snellen decimal equivalent) was 0.02 ± 0.01 and 0.54 ± 0.17, respectively, at the last follow-up. Postoperatively, corneal clarity grade 4 was present in 9 eyes, grade 3 in 2 eyes, and grade 2 in 1 eye. Mild subepithelial haze was noted in 2 eyes. The percentage of endothelial cell density loss was 28.2% ± 10.6%. No correlation was observed between the postoperative graft clarity and preoperative specular count (r = -0.021, P = 0.512). Rebubbling was performed for 1 eye that developed partial graft detachment in the first postoperative week. One patient had an episode of rejection that was managed with systemic and topical steroids. In patients with failed therapeutic penetrating keratoplasty, PDEK can be a useful alternative for visual rehabilitation as it demonstrates favorable visual outcomes with a good graft survival rate.

Phacoemulsification, pinhole pupilloplasty, and pre-Descemet's endothelial keratoplasty for keratoconus with Fuchs' endothelial dystrophy.

The comorbidity of keratoconus with Fuchs' endothelial dystrophy with cataract is a rare clinical combination. We present an amalgamation of surgical techniques to manage the above clinical conditions and its complications in single setting. The modified triple procedure, namely, the phacoemulsification, pinhole pupilloplasty, and pre-Descemet's endothelial keratoplasty (PDEK) in the order of description is followed in single sitting. Lens removal by phacoemulsification, correction of irregular astigmatism by pinhole pupilloplasty (pinhole optics), and exchanging the endothelial layer for PDEK forms the main segments of the triple procedure. This combination of techniques may decrease the risk of multiple surgeries and its related complications. Moreover, it will allow the patient for faster visual rehabilitation by improving the uncorrected visual acuity and visual quality.

A new surgical approach to pre-Descemet's endothelial keratoplasty

The study aimed to develop new surgical methods of obtaining and preserving pre-Descemet's endothelial keratoplasty (PDEK) graft in order to reduce the loss of donor material. The study was conducted on 30 sclerocorneal discs, which were divided into three groups. The first group consisted of 10 sclerocorneal discs to which the standard PDEK graft preparation technique was applied. The second group consisted of 10 sclerocorneal discs, where the PDEK graft preparation was done using the optimized method 1 involving the KD Ring fixator, KD Base for PDEK, KD-30G needle with 5 mL syringe connected to the spring-load plunger, a preservative solution. The third group consisted of 10 sclerocorneal discs with PDEK graft prepared using the optimized method 2, which differed from the optimized method 1 in additional use of the KD artificial chamber for PDEK. When successfully acquiring the type-1 "big bubble", the dissected PDEK graft was preserved for further use in clinical practice using our own technique. In the first group, formation of the type-1 «big bubble» was achieved only in 5 out of 10 donor corneas (50%). Bubble ruptures happened in 4 cases (40%) and type-2 «big bubble» occurred in 1 case (10%). In the second group (optimized method 1) the type-1 «big bubble» was achieved in 9 cases (90%), while in the third group (optimized method 2) the type-1 «big bubble» was achieved in 10 cases (100%), proving the effectiveness of our PDEK graft preparation technique. We presented a novel surgical approach for acquiring and preserving PDEK graft that minimizes almost all the difficulties that surgeons face, including bubble rupture during pneumodissection and hydrodissection, formation of type-2 and mixed type bubble, and obtaining a PDEK graft of the required size; the details of the surgical technique have been refined. The proposed technique for graft preparation and preservation can be easily implemented in eye banks and is convenient for clinical practice.

Posterior Corneal Curvature Changes After Pre-Descemet's Endothelial Keratoplasty: A Prospective Analysis.

To assess the changes in the posterior corneal curvature after pre-Descemet's endothelial keratoplasty (PDEK) and correlate with the visual outcomes. Eyes with pseudophakic bullous keratopathy, aphakic bullous keratopathy, and Fuchs dystrophy undergoing PDEK were included. The main outcome measures were the topography (OrbscanIIz, Bausch and Lomb) indices-total corneal power (TCP) in diopters (D), radius of the posterior curvature (mm), and best-fit sphere of the posterior corneal surface (BFS in D) at preoperative and postoperative 1 month, 3 months, and 6 months. Overall, 43 eyes of 43 patients with a mean age of 68 ± 9.6 years were studied. The mean preoperative TCP 43.1 D ± 2.3 reduced to 42.4 D ± 2.6 at 3 months (P < 0.010). There was a statistically significant decrease in the mean posterior corneal curvature at 1 month and 3 months postoperatively (P = 0.002). There was no significant change in the TCP and posterior corneal curvature at 6 months (P > 0.05). The mean BFS showed an increase at 1 month (53.45 ± 5.2 D) and 3 months (52.95 ± 5.1 D) and decrease at 6 months (51.90 ± 5.3 D). The overall change in BFS (P > 0.05) was not significant. There was significant improvement in visual acuity (P < 0.05). The best-corrected visual acuity was ≥20/40 in 79.07% and ≥20/60 in 100% at 6 months. There was no statistically significant correlation between the change in the best-corrected visual acuity and TCP, posterior corneal curvature, or BFS. Although there was immediate postoperative change in the posterior curvature, no significant change was induced by PDEK.

I-PDEK: Microscope-integrated OCT-assisted pre-Descemet endothelial keratoplasty.

Four patients with pseudophakic corneal edema were subjected to pre-Descemet endothelial keratoplasty (PDEK) under the direct guidance of microscope-integrated optical coherence tomography (i-OCT). i-OCT facilitated successful type 1 big bubble formation during donor preparation, debridement of the hypertrophic epithelium, planning and placement of surgical wounds, descemetorrhexis with removal of remnant Descemet membrane tags, and identification of correct donor orientation and interface details. It was also possible to discern the stability of intraocular lens, flat iris configuration, adequate stromal hydration, and wound apposition on i-OCT. Preoperative visual acuity was counting fingers (50%), 0.78 logMAR (25%), and 1.48 logMAR (25%), whereas postoperative visual acuity was 0.6 logMAR (50%) and 0.3 logMAR (50%). At 6-months of follow-up, all grafts were clear and well attached, the mean central corneal thickness, graft size, graft thickness, and endothelial cell loss were 557.25 ± 13.45 μm, 7.75 ± 0.20 mm, 25.5 ± 2.64 μm, and 21.6 ± 0.02%, respectively. To conclude, i-OCT helped during various surgical steps of PDEK.

Characterization of Endothelial Cell Loss in Pre-Descemet Endothelial Keratoplasty Graft Preparation.

To characterize the pattern and factors affecting endothelial cell loss (ECL) in pre-Descemet Endothelial Keratoplasty (PDEK) graft preparation. A prospective study was performed to characterize the pattern of ECL and the impact of inflation pressure in PDEK. Donor corneas were randomized to inflation with air versus Optisol GS storage media. PDEK preparation was performed under continuous pressure monitoring. Trypan blue was used to grade the tissue as acceptable (<25% ECL) or unacceptable (≥25% ECL). Rate of unacceptable ECL was correlated with injection media type and inflation pressure. A retrospective study was then performed of all attempted PDEK preparations at Lions Gift of Sight to evaluate impact of donor tissue factors on ECL. Donor age and tissue preservation time were evaluated and correlated with ECL with PDEK bubbling. Twenty-five corneas were tested prospectively. A reticular pattern of ECL that varied in severity occurred with bubbling. There was no difference in peak inflation pressure or mean expansion pressure between air (706.0, 510.7 mm Hg) and Optisol GS (852.9, 653.0 mm Hg). Increasing peak inflation pressure and mean expansion pressure were associated with an increased risk for unacceptable ECL. On retrospective evaluation of 131 attempted PDEKs, only 44.0% of cases with successful bubbles had acceptable endothelium after processing. Increasing donor age and decreasing preservation time were associated with increased rates of acceptable endothelium. PDEK processing can result in a reticular pattern of ECL. Higher inflation pressures are associated with greater ECL. Older donor tissues with shorter preservation times might be preferable for PDEK.

Optimizing pre-Descemet endothelial keratoplasty technique.

Pre-Descemet endothelial keratoplasty (PDEK) is an alternative technique to Descemet membrane endothelial keratoplasty (DMEK). The preparation of PDEK tissue by pneumatic dissection is simple and reproducible. The PDEK clamp helps to consistently obtain a type 1 big bubble. The mean size of type 1 big bubble is 7.255 ± 0.535 × 6.745 ± 0.668 mm. The volume of air required to obtain type 1 big bubble is 0.14 to 0.37 mL. Dissection of PDEK tissue can be achieved by trephination or manual excision. Insertion of tissue into the recipient eye can be by injection or pulling. Unfolding techniques used for PDEK are similar to those used in DMEK. Unlike DMEK, PDEK tissue is easier to handle and unscroll and allows use of younger donors. It could help surgeons converting to endothelial keratoplasty, with significant advantages in preparation, handling, and unscrolling in the eye.

Densitometry Analysis of Corneal Backscatter After Pre-Descemet Endothelial Keratoplasty for Pseudophakic Bullous Keratopathy.

To quantify corneal backscattering by densitometry analysis after pre-Descemet endothelial keratoplasty (PDEK). This is a prospective observational case series. Setting: Tertiary care hospital. Postoperative PDEK eyes with best-corrected visual acuity (BCVA) ≥20/40 without comorbidity. Slit-lamp examination, Scheimpflug imaging (Pentacam; Oculus, Wetzlar, Germany), endothelial cell density (cells/mm), and central corneal thickness (Visante; Carl Zeiss AG, Oberkochen, Germany) were performed. Corneal densitometry values for the entire depth of the cornea were compared between post-PDEK eyes and fellow eyes (non-PDEK). Mean densitometry (grayscale units, GSUs) of the anterior, posterior, central, total depth and concentric zones (0-2, 2-6, 6-10, and 10-12 mm) of the cornea. Overall, 35 eyes (21 PDEK eyes and 14 control eyes) were evaluated. The mean total densitometry values in the anterior, central, and posterior corneas were 40.7 ± 7.6 GSU, 25.3 ± 4.8 GSU, and 20.9 ± 3.4 GSU, respectively. On inter-zone comparison between central and peripheral cornea, there was a statistically significant difference (P < 0.05) between 0 to 2 mm and 6 to 12 mm zones. There was no correlation between endothelial cell density and central corneal thickness with densitometry. However, there was a significant correlation of BCVA with corneal densitometry in 0 to 2 mm (r = 0.519, P = 0.016) and 6 to 2 mm (r = 0.556, P = 0.009) zones. In eyes with BCVA 20/20, there was no significant difference between PDEK and control eyes in the total corneal densitometry in the entire depth of the cornea (P = 0.662). Clinically clear corneas with visual acuity 20/20 showed no difference in the total corneal densitometry as compared to their fellow eye. Corneal backscatter was higher in the anterior cornea and in the central 0 to 6 mm zone.

Technique for Ensuring Type I Bubble Formation for Pre-Descemet Endothelial Keratoplasty Preparation.

To describe a technique that ensures the production of a type 1 bubble when preparing pre-Descemet endothelial keratoplasty (PDEK) grafts with a high rate of predictability. Donor corneas were placed on a support disc, and a blunt instrument was used to score 360 degrees of the peripheral Descemet membrane and endothelium just inside the trabecular meshwork. Air was injected in several short bursts and several stages with a 30-gauge needle on a 3-mL syringe 2.0 mm away from the limbus to create a type 1 big bubble. The technique was tested by 2 operators (M.S. and A.S.-J.) in 26 human donor corneas, including 12 for possible transplantation, over a 9-month period. Anterior segment optical coherence tomograph (AS-OCT) was performed in 1 case proving a type 1 bubble. A type 1 big bubble was successfully created in 24 of 26 attempted cases (92.3%). The technique was used successfully to obtain PDEK tissue for transplant in 9 eyes. One case was not technically acceptable because of diffuse cell loss (>10%); however, the bubble preparation itself was successful. One case had a mixed bubble because of incomplete scoring, resulting in a Descemet membrane endothelial keratoplasty graft used for transplant. One case failed to form any bubble likely because the scoring was too central. Of a total of 26 cases, 14 cases were for practice. The Soper technique significantly improved the success rate of creating a type 1 bubble for PDEK preparation.

Native means of graft stabilization: Host descemetic scaffolding and wound scaffolding to decrease the risk for graft detachment in DMEK and PDEK

The main postoperative complication of Descemet membrane endothelial keratoplasty and pre-Descemet endothelial keratoplasty (PDEK) is graft detachment. We report a technique in which the host Descemet membrane or the incision is used for graft scaffolding. The descemetorhexis is created 0.5mm smaller than the graft from between 1 quadrant to 360 degrees, preferably in two opposite quadrants. Using the Jacob technique of pressurized air infusion (air pump-assisted PDEK), the host Descemet membrane is gently teased from under the graft with a reverse Sinskey hook and allowed to overlap the graft from the posterior aspect in a scaffolding manner. Wound scaffolding within the incision is attained by pulling any overlapping part of the graft into the inner part of the corneal incision instead of allowing it to lie posterior to the inferior lip. Both these scaffolding maneuvers give an extra degree of scaffolding or support that provides graft stability and thereby decreases the risk for graft detachment.

Triple procedure for pseudophakic bullous keratopathy in complicated cataract surgery: Glued IOL with single-pass four-throw pupilloplasty with pre-Descemet's endothelial keratoplasty

Pseudophakic bullous keratopathy is a major deterrent to visual recovery after a complicated cataract surgery. Decentered intraocular lenses (IOLs) incite chronic inflammation that often leads to bullous keratopathy. The triple procedure of glued IOL allows secondary IOL fixation along with single-pass four-throw pupilloplasty that prevents the slippage of air into the vitreous cavity and maintains air tamponade followed by pre-Descemet's endothelial keratoplasty that supplants the endothelial layer, thereby retaining its functionality.

Use of Pressurized Air Infusion For Pre Descemet's Endothelial Keratoplasty (PDEK) - The Air Pump Assisted PDEK Technique.

Purpose:To assess the advantages offered by the air pump assisted PDEK technique that utilizes pressurized Anterior Chamber (AC) air infusion.Methods:Pressurized air infusion was provided through an anterior chamber maintainer connected to the fluid air exchange system of a posterior vitrectomy machine during surgery.Results:Pressurized air infusion within the AC helped perform Descemetorhexis, prevented bleeding during Peripheral Iridectomy (PI) and synechiolysis, prevented oozing of blood from peripheral corneal neovascularization into the AC and thus helped maintain a non-fibrinous AC environment. In addition, it helped in precise graft manipulation, centration, edge unfolding and unwrinkling after it was floated against the stroma as well as faster graft adhesion. It also prevented AC depth fluctuations during intra-cameral maneuvers and prevented intra-operative as well as post-operative graft detachment.Conclusions:This technique makes several steps of surgery easier and improves graft adhesion.

Elastin Content and Distribution in Endothelial Keratoplasty Tissue Determines Direction of Scrolling

Descemet membrane endothelial keratoplasty (DMEK) and pre-Descemet endothelial keratoplasty (PDEK) tissues always scroll with the endothelial cells (EC) outside. We designed a study to understand the reason for this behavior. Experimental study. Elastin content in Descemet membrane (DM), pre-Descemet layer (PDL), central and peripheral stroma, sclera, and trabecular meshwork were measured by the Fastin elastin assay kit. Distribution of elastin in DM, PDL, and anterior lens capsule (ALC) were examined by immunohistology. The effect of recombinant elastase enzyme and the effect of complete removal of EC and epithelial cells on the scrolling of DM and ALC, respectively, were studied. PDL showed the highest elastin content among the different tissues studied. Elastin localized as a distinct anterior band in the DM and was uniformly distributed in the PDL demarcating the latter from corneal stroma. Enzymatic treatment of DM with elastase reversed scrolling and corresponded with degradation or disappearance of elastin. Removal of EC did not affect the direction of scrolling. ALC behaved in the same manner with regard to distribution of elastin, scrolling, and removal of epithelial cells. This pattern of elastin distribution in DM explains why DMEK and PDEK tissues always scroll with the EC outside. This behavior is not influenced by the EC. High elastin content and uniform distribution in the PDL suggest a structural difference from the posterior stroma.

Pre-Descemet’s Endothelial Keratoplasty (PDEK): Learning Curve in the First Brazilian Cases

Purpose: To describe the learning curve of pre-descemet endothelial keratoplasty (PDEK) and the intraoperatory findings of the first 5 cases performed at Federal University of Sao Paulo. Methods: Five PDEK procedures were performed by the same surgeons; four cases used pneumodissection and one case used reverse hydro-bubble technique to obtain the donor graft. All cases were recorded and the following intraoperative variables were measured: type of bubble obtained, button size used and time of opening and centralization of the graft in the recipient anterior chamber. Results: Type-1 Big Bubble (BB) was achieved in three of the four cases that air dissection was used. In the fourth case of pneumodissection, there was simultaneous formation of type-1 and type-2 BB. When balanced saline solution was used for dissection, type-2 BB was obtained. Every time type-2 BB was formed, the procedure was then converted to Descemet Membrane Endothelial Keratoplasty (DMEK). When only type-1 BB was achieved, the PDEK was uneventful with an easier, manipulation of the tissue and a quicker opening in the recipient anterior chamber. Namely, grafts that included pre-Descemet’s layer were less elastic and less curled. The graft size used varied from 7.50 to 7.75mm. Conclusion: PDEK is a recent technique of endothelial keratoplasty. Early outcomes suggest potential advantages in the learning curve over the prior procedures, especially by the facilitated manipulation of PDEK graft in the anterior chamber. Although results with this technique seem promising, the potential advantages need to be confirmed with long-term postoperative follow-up.

Frequency of Complications During Preparation of Corneal Lamellae Used in Posterior Lamellar Keratoplasty Using the Pneumodissection Technique (Big Bubble).

To determine the frequency of formation of various types of bubbles and the potential impact of donor and lamella parameters on this frequency, and to identify possible risk factors of unsuccessful "big-bubble" creation in preparation of pre-Descemet endothelial keratoplasty and Descemet membrane endothelial keratoplasty with peripheral stromal support. Donor age and sex, death to preservation time (DPT), storage time, presence of corneal scars (mainly a condition after cataract surgery), and endothelial cell density of 256 donor corneas were assessed before Descemet membrane endothelial keratoplasty with peripheral stromal support or pre-Descemet endothelial keratoplasty lamella preparation using the big-bubble technique. Mean donor age was 62.3 ± 8.5 years (28.3% women and 71.7% men). Mean endothelial cell density of the donor graft was 2866 ± 255 cells/mm. Mean DPT was 10.12 ± 4.88 hours, and mean storage time of the transplant before surgery was 6.5 ± 4.8 days. Corneal scars were present in 17 donor grafts (6.6%) after cataract surgery. Eleven corneas were devalued because of Descemet membrane rupture during preparation (4.3%). In 182 corneas, standard bubble type I was created (71.7%); in 27 corneas, bubble type II was created; eventually, both types of bubbles formed simultaneously (10.5%); in 47 corneas, no bubble was created (18.4%). We identified higher endothelial cell density, shorter DPT, and the presence of corneal scars after cataract surgery as risk factors threatening successful bubble formation. The only risk factor for creating type II bubbles was higher donor age in our study.

Phacoemulsification with single-pass four-throw pupilloplasty and pre-Descemet's endothelial keratoplasty for management of cosmetic iris implant complication

Placement of an anterior chamber iris implant for cosmetic reasons has been associated with development of various complications. Even after the implant has been explanted from the eye, it leaves a trail of after effects that necessitate surgical management. We describe a technique that comprises of performing phacoemulsification with single-pass four-throw pupilloplasty and a pre-Descemet's endothelial keratoplasty procedure for this eye with cosmetic iris implant complication.

Lamellar keratoplasty techniques.

Lamellar keratoplasty (LK) has revolutionized corneal graft surgery in several ways. Deep anterior LK (DALK) has eliminated risk of failure due to endothelial rejection. Endothelial keratoplasty (EK) has almost eliminated induced astigmatism and the “weak” graft–host junction as seen with penetrating keratoplasty (PK) and also reduced the risk of endothelial rejection. LK provided new insights into posterior corneal anatomy that led to better understanding and performance of DALK and to the development of another EK procedure, namely pre-Descemet's EK (PDEK). Surgical procedures for LK were further refined based on the improved understanding and are able to deliver better surgical outcomes in terms of structural integrity and long-term patient satisfaction, reducing the need of further surgeries and minimizing patient discomfort. In most specialist centers, anterior lamellar techniques like DALK and EK techniques like Descemet's stripping EK (DSEK) and Descemet's membrane EK (DMEK) have replaced the full-thickness PK where possible. The introduction of microkeratome, femtosecond laser, and PDEK clamp have made LK techniques easier and more predictable and have led to the innovation of another LK procedure, namely Bowman membrane transplant (BMT). In this article, we discuss the evolution of different surgical techniques, their principles, main outcomes, and limitations. To date, experience with BMT is limited, but DALK has become the gold standard for anterior LK. The EK procedures too have undergone a rapid transition from DSEK to DMEK and PDEK emerging as a viable option. Ultrathin-DSEK may still have a role in modern EK.