Diabetic retinopathy stabilization after renal transplantation.

Abstract

Dear Editor, We read the article “The effects of renal transplantation on diabetic retinopathy: Clinical course and visual outcomes” by Roy et al., with interest.[1] The authors aimed to elucidate the clinical course of diabetic retinopathy (DR) after renal transplantation (RT) in a hospital-based cohort. They concluded that RT stabilized the retinopathy status in the majority of patients although in a minor subset the disease course was unpredictable. We congratulate the authors for their lightening study. We would like to inform two errors which we think to be done by mistake and make some contributions about study. DR and diabetic nephropathy are the main microvascular complications of diabetes, representing the leading cause of blindness and end-stage renal disease.[2] There is a strong association between severity of retinopathy and level of kidney function.[3] Also there are several studies reporting the stabilization of the retinopathy after RT or simultaneous pancreas and kidney transplant (SPK).[1] Firstly, we want to inform two errors which we think to be done by mistake. In fourth paragraph of the discussion part, the authors informed that Chow et al., studying the effect of renal and pancreatic transplant on the status of retinal transplant found a stable visual acuity in the follow-up period. But actually in this study, Chow et al., examined the course of DR in insulin-dependent diabetic recipients of a SPK, not the status of “retinal transplant”. The authors reported in sixth paragraph of the discussion part that Chow et al., reported stabilization in 76% of DR patients post SPK transplant. But this rate was shown as 75% in Table 5 of Roy and coworkers’ article. There are many risk factors affecting the progression of the DR such as duration of diabetes, age at diagnosis, glycemic exposure, hypertension, nephropathy, pregnancy, smoking, microalbuminuria, and/or lower levels of serum hemoglobin.[4] We think that to standardize all these factors is difficult in such a study. But a control group composed of patients with similar grade DR and characteristics with the study group could be used to evaluate the effect of RT more objectively. The authors reported that 44% of the subjects underwent cataract surgery after RT and this increase was thought to cause from the use of systemic steroids in the posttransplant period. It's reported that systemic steroid use causes especially posterior subcapsular cataract (PSC).[5] So to detect the type of the cataract and rate of patients with PSC would support their comments. Also the authors reported that the higher rate of stabilization of DR in study of Mittal et al., was caused from short follow-up period (12 months). But Roy et al., reported an initial worsening till second quartile (21-46 months) and 80% stabilization of DR status by the last quartile (>75 months) in their study. So if the higher rate was due to the shorter follow-up time, Roy et al., should find a higher rate of stabilization in first quarter too in their study. This looks like a contradiction.