Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

Example Input: Abstract: In an earlier report, the authors demonstrated a trend toward progressive hyperopia in radial keratotomy (RK) patients examined between one and three to four years postoperatively. In those 109 cases, the surgeries were performed using a metal-blade instrument. In the following study, the metal-blade series was updated to a total of 225 procedures, and a more recent series of 300 procedures performed on 228 patients was examined in which a diamond-knife cutting instrument was used. Patients had uncorrected visual acuity determination, cycloplegic refractions with best corrected visual acuity measurements and keratometry measurements. The authors demonstrated a hyperopic shift in the distribution of postoperative spherical equivalent (SE) values across time such that higher proportions of cases in both metal-blade and diamond-knife series were at least 1.0 diopter (D) away from emmetropia at 24 and 48 months than was the case at 12 months after surgery. Regression analysis determined that none of the preoperative or surgical variables known to affect refractive outcome of RK (alone or in combination) could account for the changes in refraction seen during the course of postoperative time. In general, changes in keratometry paralleled refractive changes, but were somewhat smaller in magnitude.
Example Output: Progressive hyperopia in radial keratotomy. Long-term follow-up of diamond-knife and metal-blade series.

Example Input: Abstract: Parasitic, bacterial, and viral infections may all be associated with transfusion of whole blood and components, including packed red blood cells, platelets, fresh-frozen plasma, and cryoprecipitate. Proper collection and storage techniques, careful donor selection, and laboratory screening of donor blood for evidence of syphilis, hepatitis B, and human immunodeficiency virus (HIV) infection form the basis for prevention of transfusion-transmitted infections. Viral hepatitis, notably non-A non-B hepatitis, is the most frequent infectious risk of transfusion in the United States today. The risk of HIV infection is very low because of voluntary donor self-deferral and screening of donated blood for evidence of the infection.
Example Output: Current issues in transfusion therapy. 1. Risks of infection.

Example Input: Abstract: We correlated the level of vitiligo antibodies to the extent of depigmentation in thirty-two patients with vitiligo. Vitiligo antibodies were assayed by protein A-sepharose immunoprecipitation method. Antibodies were present in four of eight (50%) patients with minimal vitiligo (less than 2% body surface involved), in nine of ten (90%) patients with moderate vitiligo (2 to 5% surface involved), and in thirteen of fourteen (93%) patients with more extensive disease (greater than 5% surface involved). The level of vitiligo antibodies in the three groups expressed as a binding index was 2.9% +/- 2.03, 5.6% +/- 2.92, and 8.0% +/- 3.03 SD, respectively. These results suggest that there is a relation between the incidence and level of vitiligo antibodies and the extent of depigmentation in vitiligo.
Example Output:
Correlation between vitiligo antibodies and extent of depigmentation in vitiligo.