Objective To evaluate the clinical effect of using a ring-shaped donor cornea in partial lamellar keratoplasty for early-stage Mooren's ulcer.Methods It was a retrospective case series study.Partial lamellar keratoplasty was performed on 11 eyes with Mooren's ulcer.The patients were treated for symptoms for a week or more.A residual ring-shaped section of a donor cornea was used after partial penetrating keratoplasty.A trephine (7.75-8.00 mm) was used to mark the central cornea.An ophthalmic knife was used to deepen the trephine groove to an extent dictated by the size of the lesion in order to excise the lesion adequately.If corneal perforation appeared before or during the operation,it was repaired using a very thin layer of lamellar cornea larger than the perforation and sutured to the perforation hole with 10-0 sutures.Then a ring-shaped donor graft was used to repair the lesion area.Visual acuity,condition of the lesion,and complications were monitored for 6-36 months.Repeated measures analysis of variance were used.Results Compared to pre-surgery,uncorrected visual acuity improved by a mean of 1.36±1.21 Snellen chart lines at 1 month,1.72±1.47 lines at 3 months and 1.86±2.04 lines at 6 months.Best spectacle-corrected visual acuity improved by a mean of 0.46±0.93 Snellen chart lines at 1 month,0.73±1.10 lines at 3 months and 1.55±1.75 lines at 6 months.There were significant difference before and after surgery at uncorrected visual acuity (F=5.630,P＜0.05) and best spectacle-corrected visual acuity (F=5.925,P＜0.05).One patient had graft epithelial defect and was cured with an amniotic membrane transplant after 20 days.One patient had a recurrence after 19 months and was cured with a second lamellar keratoplasty.No rejections were detected.Conclusion A ring-shaped donor cornea in partial lamellar keratoplasty for Mooren's ulcer is a useful option when medical treatment fails.It cannot only control the development of the disease,but also preserve the visual axis of the clear cornea and to a large extent save the donor cornea.