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Purpose To evaluate the clinical outcome of Descemet membrane endothelial keratoplasty (DMEK) performed in eyes with comorbid keratoconus (KCN) and corneal endothelial dysfunction. Methods Twenty-five consecutive eyes of 14 patients with comorbid stable KCN underwent DMEK for corneal endothelial dysfunction; best spectacle corrected visual acuity (BSCVA), maximum corneal curvature (Kmax), maximum corneal power (Pmax), central corneal thickness (CCT), and intra- and postoperative complications were assessed. Results Excluding eyes requiring re-transplantation for primary graft failure (n = 3), all eyes showed improvement in BSCVA, reaching ≥ 20/40 (0.5) in 86%, ≥ 20/25 (0.8) in 55%, and ≥ 20/20 (1.0) in 27% by one month postoperatively; 90%, 76%, and 48% by 6 months postoperatively; and 88%, 76%, and 47% by 12 months postoperatively. CCT decreased from 571μm preoperatively to 485μm at 1 month (p Conclusion DMEK is technically feasible in eyes with comorbid KCN and may give excellent outcomes visual and refractive outcomes, including significant corneal flattening, which may potentially create a visually significant hyperopic shift in patients with severely ectatic corneas.

Currently, there are very few well-established treatments to stimulate corneal endothe-lial cell regeneration in vivo as a cure for corneal endothelial dysfunctions. The most frequently performed intervention for a damaged or dysfunctional corneal endothe-lium nowadays is corneal endothelial keratoplasty, also known as lamellar corneal transplantation surgery. Newer medical therapies are emerging and are targeting the regeneration of the corneal endothelium, helping the patients regain their vision with-out the need for donor tissue. Alternatives to donor tissues are needed as the aging population requiring transplants, has further exacerbated the pressure on the corneal eye banking system. Significant ongoing research efforts in the field of corneal regen-erative medicine have been made to elucidate the underlying pathways and effector proteins involved in corneal endothelial regeneration. However, the literature offers little guidance and selective attention to the question of how to fully exploit these pathways. The purpose of this paper is to provide an overview of wound healing characteristics from a biochemical level in the lab to the regenerative features seen in the clinic. Studying the pathways involved in corneal wound healing together with their key effector proteins, can help explain the effect on the proliferation and migration capac-ity of the corneal endothelial cells. (Translational Research 2022; 248:111-127)

The aim of this study was to review the postoperative course and imaging features of 7 eyes that presented with corneal hydrops after Bowman layer (BL) transplantation was performed for advanced keratoconus to determine the potential mechanisms of hydrops formation.A retrospective analysis was performed of 7 eyes of 5 patients with advanced keratoconus that underwent midstromal BL transplantation at 2 tertiary referral centers and developed acute corneal hydrops on average 64 (±30) months (range 14-104 months) postoperatively. Corneal tomography and anterior segment optical coherence tomography (AS-OCT) images were reviewed to document the postoperative and posthydrops course.For all eyes, the post-BL transplantation course was uneventful until hydrops development. Despite stable postoperative topographies in 5 of 7 eyes, eyes developed hydrops with typical hypodense areas on AS-OCT that were limited to the stromal layers posterior to the BL graft. With AS-OCT (6/7 eyes), 2 eyes showed a break in Descemet membrane, whereas Descemet membrane was intact across the cornea in 2 eyes; in 2 eyes, the images were inconclusive. All patients admitted to continued eye rubbing, and all but 1 had a clinically significant allergy and/or atopic constitution. Most eyes (5/7) showed a relatively quick (visual) recovery within 1 to 4 months after hydrops.Hydrops formation in keratoconic corneas after midstromal BL transplantation may indicate that a break in Descemet membrane is secondary to hydrops development (and not vice versa). With a midstromal BL graft in situ limiting hydrops dimensions, resolution of the hydrops seemed relatively quick with recovery to prehydrops visual acuity in most eyes.

Purpose To report endothelial cell density (ECD) after posterior lamellar keratoplasty (PLK). Design Prospective, interventional case series. Methods In a single institution, PLK was performed in 15 eyes of 15 patients with pseudophakic bullous keratopathy (PPBK), Fuchs endothelial dystrophy (FED), or both. In 11 eyes, the donor tissue was inserted unfolded through a 9.0-mm sclerocorneal incision. In four eyes, the donor was folded and inserted through a 5.0-mm incision. The ECD measurements were performed in each patient at regular intervals until three years after surgery, and then in all patients simultaneously at 54 to 84 months after surgery. Results Three patients were not available for follow-up. One graft had decompensated. In the remaining 11 eyes, ECDs ranged from 368 to 1576 cells/mm 2 . Monophasic and biphasic regression models of ECD against time were fitted for each technique separately. Conclusions After PLK, ECD declined at a high rate. Both early- and longer-term loss rates may be related to surgical technique.

For the same diamond blade extension, uphill (centripetal) radial keratotomy incision direction achieves greater depth and consequently greater refractive effect than downhill (centrifugal) incisions. To determine which factors may account for this difference, two uphill and two downhill incisions were made with a double-edged diamond blade set to 90% central pachometry in 26 human donor eyes at 15 or 60 mm Hg. Uphill incisions made with the perpendicular blade had greater mean incision depth than downhill incisions made with the oblique blade at 15 mm Hg (83.6 +/- 3.9% and 68.2 +/- 5.2%) (p0.0005) and at 60 mm Hg (86.3 +/- 3.1% and 79.7 +/- 1.7%) (p0.0005). Uphill and downhill incisions both made with the perpendicular blade had equal depth (85.4 +/- 4.9% and 83.7 +/- 3.5%) (p0.1). The perpendicular blade edge created a straight, and the oblique edge an S- or J-shaped, histological incision configuration. Corneal profile pictures taken during each incision showed the knife to tilt opposite of the incision direction and to move at a constant angle to the limbal plane, producing a smaller optical clear zone (OCZ) in the posterior stroma than intended with uphill incisions. Greater refractive effect with uphill incisions may be explained by the perpendicular blade being more effective in incising corneal lamellae, and the creation of a smaller posterior OCZ. Intraocular pressure variations during surgery may affect achieved incision depth of downhill, but not of uphill, incisions.

Radial keratotomy (RK) is currently performed with four or eight semi-radial incisions. To evaluate the effect of a theoretically more stable three-incision RK pattern, centripetal incisions were made in 16 human donor eyes (eight pairs), using a double-edged diamond blade set to 90% of central pachymetry and a 3.5 mm optical clear zone. Intraocular pressure was maintained at 15 mm Hg during surgery and while keratometry readings were made. One randomly selected eye of each pair had three radial incisions made at 12, 4 and 8 o'clock; the other eye had four radial incisions at 12, 3, 6, and 9 o'clock. Corneal flattening was 6.08 diopters (D) with four incisions and 4.84 D with three incisions (P less than .05). Astigmatism increased 0.44 D and 0.69 D, respectively (P greater than .1). Histologically measured mean incision depth (77.4%) did not differ significantly between the groups (P greater than .1). This study shows that 80% of the effect of a four-incision RK pattern can be obtained with a theoretically more stable three-incision pattern.

PURPOSE To evaluate the predictability of the depth of stromal pockets made in the posterior cornea for the excision of anterior or posterior lamellar corneal buttons with a planned thickness. METHODS Stromal corneal pocket dissections were created in human eye bank eyes by making a peripheral arcuate keratotomy incision at 60, 80, or 95% of central pachymetry and creating a pocket from the bottom of the incision across the cornea. Pocket depth was measured by pachymetry immediately after surgery and by light microscopy. RESULTS Mean achieved central pocket depth differed by 0.03+/-0.03 mm from the intended depth. Variation in depth across the pocket decreased from 0.07+/-0.02 mm for pockets made at 60% of the intended depth to 0.05+/-0.01 mm for pockets made at 80% depth, and 0.04+/-0.02 mm for pockets made at 95% depth (p < 0.01). Pachymetric and histological measurements of relative pocket depth averaged 64+/-9% and 73+/-7%, respectively, for pockets made at 60% of the intended depth, 82+/-7% and 86+/-3% for pockets made at 80% depth, and 91+/-7% and 92+/-3% for pockets made at 95% depth. The difference between pachymetric and histological relative pocket depth measurements decreased with deeper pocket depth (p < 0.01). CONCLUSIONS In the posterior cornea, stromal pockets can be created to within 30 microm from the intended depth. Variation in depth throughout the pocket decreases with deeper pocket depth. Pachymetry is a reliable method to check the achieved pocket depth during surgery; the accuracy of pachymetry readings improves with deeper pocket depth.