In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.

Context: Environmental conditions (eg, latitude) play a critical role in the susceptibility and severity of many autoimmune disorders, including multiple sclerosis (MS). Here, we investigated the mechanisms underlying the beneficial effects of immune regulatory processes induced in the skin by moderate ultraviolet B (UVB) radiation on central nervous system (CNS) autoimmunity.', 'Effects of UVB light were analyzed in a murine model of CNS autoimmunity (experimental autoimmune encephalomyelitis). Additionally, patients with relapsing-remitting MS were treated with narrowband UVB phototherapy. Immunomodulatory effects were examined in skin biopsies, serum samples, and immune cells of the peripheral blood.', 'Regulatory T cells (Tregs), which are induced locally in the skin-draining lymph nodes in response to UVB exposure, connect the cutaneous immune response to CNS immunity by migration to the sites of inflammation (blood, spleen, CNS). Here, they attenuate the inflammatory response and ameliorate disease symptoms. Treg-inducing tolerogenic dendritic cells (DCs) were further necessary for induction of this systemic immune regulation by UVB radiation, because ablation of Langerhans cells abolished the UVB-induced phenotype. MS patients treated with UVB phototherapy showed an increase in induced Tregs and tolerogenic DCs accompanied by the downregulation of the T-cell effector cytokine interleukin 21. The treatment further induced elevated serum levels of vitamin D.\Question: Does ultraviolet B light attenuate the systemic immune response in central nervous system autoimmunity?
Local UVB radiation of the skin influences systemic immune reactions and attenuates systemic autoimmunity via the induction of skin-derived tolerogenic DCs and Tregs. Our data could have implications for the understanding or therapeutic modulation of environmental factors that influence immune tolerance.

Context: Studies over many years have demonstrated that preoptimization and attention to appropriate perioperative care is associated with a substantial decrease in surgical mortality. This review discusses ways in which patient preparation and perioperative support can minimize surgical mortality and morbidity.', 'Scoring systems continue to be developed in order to classify categories of surgical risk. Objective physiologically based assessments can also identify high-risk groups of patients. Debate continues over the indications for specific interventions such as beta-blockade or statin therapy. There is continuing interest in perioperative optimization of oxygen delivery. A multimodality approach paying attention to a range of possible interventions appears to be beneficial. Audit, training, experience and a sufficient volume of procedures are all factors associated with surgical mortality.\Question: Does excellent anaesthesia need patient preparation and postoperative support to influence outcome?
The provision of a high-quality service throughout the perioperative period is vital for a successful outcome. Patients need to be assessed well before major elective surgery to determine if they fall into a high-risk category. Some patients may benefit from a change in management. Postoperatively, critical-care support should be available backed by level 1 (enhanced ward) care with input from outreach or medical emergency teams 24 hours per day, seven days a week.

Context: To assess the alterations in keratometric astigmatism following the 25-gauge transconjunctival sutureless pars plana vitrectomy versus the conventional pars plana vitrectomy.', 'Sixteen consecutive patients were enrolled into the study. Conventional vitrectomy was applied to eight of the cases and 25-gauge transconjunctival sutureless vitrectomy was performed in eight patients. Keratometry was performed before and after the surgery.', 'In the 25-gauge transconjunctival sutureless pars plana vitrectomy group, statistically significant changes were not observed in the corneal curvature in any post-operative follow-up measurement (p > 0.05); whereas in the conventional pars plana vitrectomy group, statistically significant changes were observed in the first postoperative day (p = 0.01) and first postoperative month (p = 0.03). We noted that these changes returned to baseline in three months (p = 0.26).\Question: Do keratometric alterations following the 25-gauge transconjunctival sutureless pars plana vitrectomy versus the conventional pars plana vitrectomy?
Both 25-gauge transconjunctival sutureless and conventional pars plana vitrectomy are effective surgical modalities for selected diseases of the posterior segment. Surgical procedures are critical for the visual rehabilitation of the patients. The post-operative corneal astigmatism of the vitrectomised eyes can be accurately determined at least two months post-operatively.