Finding food in a changing world: Small-scale foraging habitat preferences of an insectivorous passerine in the Alps.

Organisms living in high-elevation habitats are usually habitat specialists who occupy a narrow ecological niche. To envision the response of alpine species to a changing environment, it is fundamental to understand their habitat preferences on multiple spatial and temporal scales. However, information on small-scale habitat use is still widely lacking. We investigated the foraging habitat preferences of the migratory northern wheatear Oenanthe oenanthe during the entire presence at a breeding site in the central Alps. We repeatedly observed 121 adult and juvenile individuals. We applied Bayesian logistic regression models to investigate which habitat characteristics influenced foraging habitat selection on a fine spatial scale, and how habitat use varied temporally. Throughout their presence on the breeding grounds, northern wheatears showed a consistent preference for a mosaic of stones and bare ground patches with slow-growing, short vegetation. The proximity of marmot burrows was preferred, whereas dense and low woody vegetation was avoided. After arrival at the breeding site, short vegetation, preferably close to the snow, was favored. The preference for open habitat patches that provide access to prey underlines the critical role of small-scale habitat heterogeneity for northern wheatears. The strong and consistent preference for a habitat that is under pressure from land-use and climate change suggests that this alpine bird species may be sensitive to habitat loss, leading to a potential range contraction. We highlight the need to conserve habitat diversity on a small spatial scale to ensure the long-term availability of suitable habitat for northern wheatears in the Alps.

Influence of Intraoperative Air Tamponade Time on Graft Adherence in Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To study the influence of different intraoperative air tamponade times on graft adherence after Descemet membrane endothelial keratoplasty (DMEK). METHODS: In this interventional case series, we evaluated 117 eyes with Fuchs endothelial corneal dystrophy (FECD) that underwent DMEK using intraoperative air tamponade times of 60 minutes (group I; n = 39), 45 minutes (group II; n = 39), or 30 minutes (group III; n = 39). At 1 and 6 months postoperatively, graft adherence status, endothelial cell density, central pachymetry, and postoperative complications were recorded. RESULTS: At 1 month, 19 of the 117 eyes (16.2%) showed a clinically significant detachment (>1/3 of the graft surface area and affecting visual axis): 6 eyes in group I (15.4%), 5 eyes in group II (12.8%), and 8 eyes in group III (20.5%) (P = 0.82). A minor detachment (<1/3 of the graft surface area and not affecting visual axis) was observed in 6 eyes in group I (15.4%), in 7 eyes in group II (17.9%), and in 4 eyes in group III (10.3%) (P = 0.82). The overall rebubbling rate was 11%, with no difference among the groups (P = 0.07). Mean endothelial cell density decrease at 6 months was 41% (±17%) (P = 0.56), whereas mean central pachymetry decreased by 23 (±10) % (P = 0.77), with no differences between the groups. CONCLUSIONS: The incidence of graft detachment after DMEK for FECD did not differ between the eyes that had a 60-, 45-, or 30-minute intraoperative air tamponade. Reducing the intraoperative air tamponade time to 30 minutes may be considered for DMEK in eyes with uncomplicated FECD.

Histopathology of Failed Descemet Membrane Endothelial Transfer.

OBJECTIVES: To describe the postmortem histologic features after an unsuccessful Descemet membrane endothelial transfer (DMET) and assess any potential clinical implications. METHODS: Postmortem, an eye from a patient who previously underwent unsuccessful DMET for pseudophakic bullous keratopathy (PPBK) was harvested and processed for morphologic evaluation. RESULTS: Clinically and histologically, the host cornea showed evidence of diffuse stromal edema. Although the edges of the surgical descemetorhexis were well visualized, there was no evidence of endothelial migration or repopulation of the posterior stroma from any direction. A multilayered, retrocorneal membrane was present that appeared to originate from the trabecular meshwork. CONCLUSIONS: Descemet membrane endothelial transfer and "descemetorhexis alone" may be insufficient treatment for eyes operated on for PPBK, that is, eyes with a significantly depleted or dysfunctional endothelium.

Outcome and Histopathology of Secondary Penetrating Keratoplasty Graft Failure Managed by Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To describe the clinical outcome and histopathology of Descemet membrane endothelial keratoplasty (DMEK) performed for secondary graft failure after penetrating keratoplasty (PK). METHODS: A total of 11 eyes from 10 patients who underwent DMEK for secondary PK graft failure at a tertiary referral center were included in this retrospective study. Best-corrected visual acuity, endothelial cell density, and central pachymetry were evaluated before and at regular time intervals up to 36 months after DMEK and complications were recorded; 1 post mortem cornea was available for light microscopy. RESULTS: At their last follow-up visit (on average, 16 months after DMEK), 7 of 11 transplanted corneas were clear. In the 7 eyes with clear grafts, 5 had a best-corrected visual acuity of ≥20/25 (≥0.8), central pachymetry averaged 535 (±70) µm, and endothelial cell density averaged 1045 (±500) cells/mm. Of the 11 eyes, 4 required rebubbling in the early postoperative phase; 1 eye was left with a small (<1/3) detachment. Light microscopy of the pathology specimen showed complete attachment of the DMEK graft onto the preexisting PK posterior stroma, with interface scarring over DMEK graft folds and underneath the graft area that had initially been detached. CONCLUSIONS: DMEK may be a viable option to manage secondary PK graft failure with acceptable outcomes in many cases. Rebubbling for graft detachment may be anticipated, especially because of preexisting glaucoma conditions (severe decompensation, hypotony, and tubes from glaucoma-draining devices). Graft reattachment may occur through interface scarring.

Case Report of Quarter-Descemet Membrane Endothelial Keratoplasty for Fuchs Endothelial Dystrophy.

PURPOSE: To describe a further modification of Descemet membrane endothelial keratoplasty (DMEK), using a quarter of an untrephined full-size donor Descemet membrane (DM) sheet ("Quarter-DMEK"). METHODS: A 58-year-old patient underwent Quarter-DMEK for Fuchs endothelial dystrophy in his pseudophakic right eye, with a single quadrant of a full-size, 11.5-mm-diameter DM graft. RESULTS: Best-corrected visual acuity improved from 20/50 (0.4) before surgery to 20/40 (0.5) at 1 day, 20/30 (0.7) at 1 week, 20/25 (0.8) at 1 month and 20/20 (1.0) at 3 months after surgery. Central endothelial cell density decreased from 2700 cells/mm before surgery to 1551 cells/mm at 1 week, 1104 cells/mm at 1 month, and 846 cells/mm at 3 months after surgery. Pachymetry returned to normal values within the first month. No complications were observed. CONCLUSIONS: Quarter-DMEK may give fast visual rehabilitation within the first month similar to visual outcomes after circular DMEK or semicircular DMEK (hemi-DMEK). If long-term endothelial cell density would prove acceptable in a larger number of cases, quarter-DMEK may have the potential to quadruple the availability of donor endothelial tissue for endothelial keratoplasty.

Histopathologic Features of Descemet Membrane Endothelial Keratoplasty Graft Remnants, Folds, and Detachments.

PURPOSE: To describe the histologic features of postmortem eyes after Descemet membrane endothelial keratoplasty (DMEK) and their potential clinical implications. DESIGN: Histopathologic study. PARTICIPANTS: Eleven postmortem DMEK corneas of 8 patients who underwent surgery for Fuchs endothelial dystrophy, with an average postoperative time of 4±1.9 years (range, 7 months-6.5 years). METHODS: Eleven corneas transplanted with a DMEK graft were procured after death and processed for light microscopy evaluation. MAIN OUTCOME MEASURES: Histologic findings at the donor-host interface and at the host edge. RESULTS: Of the 11 corneas available for analysis, 9 showed normal anatomic features in the corneal center; that is, the donor-host interface resembled that of a virgin eye. One eye also had an anatomically normal periphery, but the remaining 10 eyes showed specific abnormalities in the periphery. Nine demonstrated overlapping of the DMEK graft onto the host edge of the descemetorhexis (and in 6 of these, the overlapping tissue showed a contracted inward fold at its peripheral edge with scar tissue); 1 eye showed a dense, acellular scar overlying a portion of the DMEK graft that clinically had shown a detachment followed by spontaneous adherence; 3 eyes showed subtle graft folds with scar tissue anteriorly; in 2 eyes (of the same patient), the anterior banded layer of the host Descemet membrane (DM) was still in situ across the cornea (both of these eyes had required rebubbling); and 2 eyes showed host DM remnants within the corneolimbal tunnel incision that may have interfered with incisional wound healing. CONCLUSION: Incomplete host DM removal may relate to postoperative DMEK graft detachment and wound instability. Graft detachments may reattach with interface scarring. Rebubbling procedures may be performed within 4 to 6 weeks, before portions of the detached graft scar. Subtle DMEK graft folds may explain subjective reports of monocular diplopia.