title: Intrastromal corneal ring in penetrating keratoplasty: evidence-based update 4 years after implantation.
abstract: OBJECTIVE
  To report the clinical outcomes of an intrastromal corneal ring (ISCR) used in penetrating keratoplasty (PKP) that was designed to decrease postoperative corneal astigmatism, stabilize refraction, accelerate healing, and possibly reduce immune reactions.
  
  
  METHODS
  An 8 mm cobalt-titanium-molybdenum alloy ring was sutured into the PKP wounds. A prospective study compared the outcomes of PKP in 179 consecutive cases with a ring (Group 1) and 101 consecutive patients without a ring (Group 2). The ring was used in different types of endoepithelial degeneration as well as in keratoconus stage IV. Patients with macular pathology were included.
  
  
  RESULTS
  The mean age of Group 1 patients was 67 years (range 9 to 96 years). Postoperative best corrected visual acuity after 1 year was almost identical in both groups (20/42 in Group 1 and 20/45 in Group 2) as were the cylinder values (Group 1, 2.64 diopters [D] +/- 1.44 (SD) versus Group 2, 2.83 +/- 1.52 D). There were 2 immune reactions in group I as compared to 6 (1.2% vs 7%, P value 0.02) in group II within 4 years of the procedure. Evaluation was performed by the Kaplan-Meier method.
  
  
  CONCLUSIONS
  Advantages of the ISCR were observed outside the targeted goals of improving the amount of astigmatism and maintaining refractive stability. Best corrected visual acuity and cylinder development were similar in Groups 1 and 2, whereas, there was a highly reduced immune rejection rate. The ring also appeared to act as a barrier to superficial vessels.
authors.affiliation: Clinic Krumeich, Bochum, Germany. jk@krumeich.de
authors.forename: Jorg H
authors.initials: JH
authors.lastname: Krumeich
authors.forename: Gernot
authors.initials: G
authors.lastname: Duncker
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D002648:Child; D002858:Chromium Alloys; D003319:Corneal Stroma / Q000503:physiopathology / Q000601:surgery*; D019317:Evidence-Based Medicine; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015948:Keratoplasty, Penetrating / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011446:Prospective Studies; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D014792:Visual Acuity / Q000502:physiology
chemical_list: D002858:Chromium Alloys