[Clinical effects of pediatric penetrating keratoplasty for congenital corneal opacity].

Objective: To report the clinical results of pediatric penetrating keratoplasty (PKP) in patients under 3 years old with congenital corneal opacity. Methods: Retrospective study. Sixteen eyes of 12 patients who were treated with PKP in Aier Eye Hospital Group from June 2009 to December 2016 were enrolled in this study. All the patients were diagnosed as congenital corneal opacities: 8 cases (11 eyes) with Peter's anomaly I, 2 cases (3 eyes) with sclerocornea, and 2 cases (2 eyes) with corneal dermoid tumor combined with iris synechia. Seven cases (7 eyes) were under 1 year old. Eight cases (10 eyes) could not follow the light. Only 1 case (2 eyes) received PKP with extracapsular cataract extraction, and the others only had PKP. Postoperative examinations were performed more frequently than in adults, and sometimes general anesthesia was needed. Results: The follow-up period was from 8 months to 6 years (33.17±22.60 months). The postoperative visual acuity improvement was found in all eyes from 1 week to 1 month after surgery except a 3-year-old patient with corneal dermoid tumor with serious esotropia. All the surgeries were successful without intraoperative complications. Graft rejection occurred in 4 cases (4 eyes). The graft of a 33-month-old patient became semitransparent. The grafts of 2 cases under 1 year old were clear after drug therapy. And the vision of a 3-year-old patient with Peter anomaly improved obviously, but immune rejection occurred 2 years after surgery. The second PKP was performed, but rejection occurred again. Secondary glaucoma was found in the other eye early after operation; anti-glaucoma surgery failed, and the graft became cloudy. Graft infection associated with loosened sutures was observed in one case (2 eyes) of sclerocornea, and the second PKP failed. Conclusions: For the patients with congenital corneal opacities, there is often a noticeable visual improvement after PKP. Good postoperative care, appropriate amblyopia treatment and timely examination are the keys to success. (Chin J Ophthalmol, 2017, 53: 941-946).

Dynamical diffraction of high-energy electrons investigated by focal series momentum-resolved scanning transmission electron microscopy at atomic resolution.

We report a study of scattering dynamics in crystals employing momentum-resolved scanning transmission electron microscopy under varying illumination conditions. As we perform successive changes of the probe focus, multiple real-space signals are obtained in dependence of the shape of the incident electron wave. With support from extensive simulations, each signal is shown to be characterised by an optimum focus for which the contrast is maximum and which differs among different signals. For instance, a systematic focus mismatch is found between images formed by high-angle scattering, being sensitive to thickness and chemical composition, and the first moment in diffraction space, being sensitive to electric fields. It follows that a single recording at one specific probe focus is usually insufficient to characterise materials comprehensively. Most importantly, we demonstrate in experiment and simulation that the second moment µ20+µ02=〈p2〉 of the diffracted intensity exhibits a contrast maximum when the electron probe is focused at the top and bottom faces of the specimen, making the presented concept attractive for measuring local topography. Given the versatility of 〈p2〉, we furthermore present a detailed study of its large-angle convergence both analytically using the Mott scattering approach, and by dynamical simulations using the multislice algorithm including thermal diffuse scattering. Both approaches are in very good agreement and yield logarithmic divergence with increasing scattering angle.