Microkeratome-assisted anterior lamellar keratoplasty for the correction of high-degree postkeratoplasty astigmatism

Purpose: To describe the surgical technique and report the outcomes of patients treated with microkeratome-assisted anterior lamellar keratoplasty (MALK) for the correction of high-degree postkeratoplasty astigmatism. Methods: Four eyes of 2 patients with extremely high (>10 D) and irregular [surface asymmetry index >1.0 D] post-penetrating keratoplasty astigmatism occurring after complete suture removal underwent MALK and were followed for at least 3 years after the procedure. In all cases, 250-mm lamellar keratectomy was performed, followed by 2 full-thickness incisions through the penetrating keratoplasty scar and the placement of an appropriately sized donor graft, which was secured with a double-running 10-0 nylon suture. All sutures were removed in all eyes within 1 year from surgery. Corrected distance visual acuity, refraction, corneal topography, and endothelial cell density were noted at each examination. Results: At the last follow-up examination (3 years or longer after MALK), corrected distance visual acuity had improved to 20/20, refractive astigmatism had decreased to an average of 2.1 D (in all cases within 4.5 D), and the average surface asymmetry index had reduced from 2.27 to 0.56. Conclusions: MALK is an effective and safe technique for the correction of high-degree postkeratoplasty astigmatism

Multiple Manifestations of Microstimulation in the Optic Tectum: Eye Movements, Pupil Dilations, and Sensory Priming

It is well established that the optic tectum (or its mammalian homologue, the superior colliculus) is involved in directing gaze toward salient stimuli. However, salient stimuli typically induce orienting responses beyond gaze shifts. The role of the optic tectum in generating responses such as pupil dilation, galvanic responses, or covert shifts is not clear. In the present work, we studied the effects of microstimulation in the optic tectum of the barn owl (Tyto alba) on pupil diameter and on eye shifts. Experiments were conducted in lightly anesthetized head-restrained barn owls. We report that low-level microstimulation in the deep layers of the optic tectum readily induced pupil dilation responses (PDRs), as well as small eye movements. Electrically evoked PDRs, similar to acoustically evoked PDRs, were long-lasting and habituated to repeated stimuli. We further show that microstimulation in the external nucleus of the inferior colliculus also induced PDRs. Finally, in experiments in which tectal microstimulations were coupled with acoustic stimuli, we show a tendency of the microstimulation to enhance pupil responses and eye shifts to previously habituated acoustic stimuli. The enhancement was dependent on the site of stimulation in the tectal spatial map; responses to sounds with spatial cues that matched the site of stimulation were more enhanced compared with sounds with spatial cues that did not match. These results suggest that the optic tectum is directly involved in autonomic orienting reflexes as well as in gaze shifts, highlighting the central role of the optic tectum in mediating the body responses to salient stimuli

Deep Anterior Lamellar Keratoplasty After Descemet Stripping Automated Endothelial Keratoplasty

Purpose To report the indications and long-term outcomes of deep anterior lamellar keratoplasty (DALK) performed after Descemet stripping automated endothelial keratoplasty (DSAEK) in cases of visually significant stromal opacities. Design Retrospective, interventional, consecutive case series. Methods SETTING: Private hospital. STUDY POPULATION: Thirteen eyes that underwent DALK after DSAEK at our institution. Indications for DALK after DSAEK included both stromal opacities persisting after DSAEK and stromal opacities occurring secondarily in post-DSAEK corneas. DALK was always performed in a standardized fashion including exchange of a disc of full-thickness recipient cornea (up to the DSAEK stromal surface),7.0 mm in diameter, with a donor lamella obtained by microkeratome-assisted dissection, punched to 7.0 mm and sutured into place with a double running 10-0 nylon suture. MAIN OUTCOME MEASURES: Best spectacle-corrected visual acuity (BSCVA), manifest refraction, and endothelial cell density (ECD). Results Mean follow-up was 26 ± 18 months (range = 6â60 months). Indications for DSAEK were full-thickness graft failure (n = 8), DSAEK graft failure (n = 3), and pseudophakic bullous keratopathy (n = 2). Indications for subsequent DALK were persisting stromal opacity (n = 9) and stromal opacities newly occurred after DSAEK as a result of HSV keratitis (n = 2) or interface infection (n = 2). After complete suture removal, mean BSCVA was 20/28 (0.14 ± 0.8 logMAR) in eyes without ocular comorbidities affecting visual acuity (n = 7), while refractive astigmatism was within 4 diopter (D) in all but 1 eye (average = 3.2 ± 1.4 D). No intraoperative complications were recorded. Conclusions Performing DALK on DSAEK eliminates the need for open-sky surgery, achieving visual results comparable to those of penetrating keratoplasty, while sparing a healthy endothelial graft

Adaptation to sub-optimal hosts is a driver of viral diversification in the ocean

Marine cyanophages infect oceanic cyanobacteria that are important contributors to global primary production. By using an experimental evolution approach, here the authors show that adaptation to sub-optimal cyanobacterial hosts result in genomic diversification of cyanophage populations

Outcomes of ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) performed in eyes with failure of primary Descemet membrane endothelial keratoplasty (DMEK)

Aim: To evaluate the outcomes of ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) performed in eyes after failure of primary Descemet membrane endothelial keratoplasty (DMEK). Methods: This was a retrospective, non-comparative interventional case series done in a tertiary care hospital. The study group included 21 eyes of patients which underwent UT-DSAEK following the failure of primary DMEK. Outcome measures included best spectacle-corrected visual acuity (BSCVA) and endothelial cell density (ECD) both recorded 6 and 12 months postoperatively as well as central graft thickness (CGT) measured 6 months after UT-DSAEK. Results: When considering only eyes without comorbidities (17 of 21), 12 months after UT-DSAEK, BSCVA was ≥20/25 in 12/13 (92%) eyes and ≥20/20 in 4/13 (30%) eyes. Mean ECD loss rate was 38.9% at 12 months postoperatively (range 8%-57%). Six months postoperatively, CGT averaged at 81±34 μm (range 34-131 μm). No intraoperative complications were recorded. Postoperatively, one patient (no. 8) had graft wrinkles that were fixed 2 days following UT-DSAEK. Four patients have developed intraocular lens (IOL) opacification, and two of them underwent IOL exchange. No other postoperative complications were recorded. Conclusions: UT-DSAEK is instrumental in the management of primary DMEK graft failure, allowing visual rehabilitation which is comparable with that of repeat DMEK