To Determine the Correlation of Haemoglobin A1c Levels With Diabetic Retinopathy In Type Ii Diabetes Mellitus

Abstract

BACKGROUND: Diabetes is the commonest metabolic abnormality in the world. Type II diabetes (NIDDM) is the commonest form of diabetes constituting nearly 90% of diabetic population. Diabetic retinopathy is a common and specific microvascular complication of diabetes, and remains the leading cause of preventable blindness in working-aged people. HbA1c is a powerful univariate correlate of retinopathy. Decrease in glycosylated haemoglobin levels is associated with a significant decrease in the progression of DR. The existence of thresholds of glycaemia has not been studied often in patients with type II diabetes mellitus. OBJECTIVES: 1. To determine the correlation of blood levels of haemoglobin A1c to the presence of diabetic retinopathy in patients with type II diabetes mellitus. 2. To correlate the severity of diabetic retinopathy with levels of haemoglobin A1c. METHODOLOGY: The present study was carried out as a one year cross sectional descriptive observational design between January 1, 2010 and December 31, 2010 at KLES Hospital and MRC. A total of 100 type II diabetes patients with retinopathy changes and recent HbA1c levels known were included. Participants with very hazy ocular media and pregnant women were excluded. Informed consent were taken followed by relevant history, general physical examination, complete ophthalmic examination and detailed fundus evaluation and seven field fundus photography. The retinopathies were documented in accordance with the modified ETDRS classification. FBS levels and HbA1c levels by high X performance liquid chromatography were noted. Statistical correlations were done by SPSS statistical data package editor, version 17.0 OBSERVATIONS AND RESULTS: 100 patients included in our study. The mean age of participants in this study was 61.74  8.83 and out of the 100 participants, 72 males and 28 females with M:F ratio of 2.57 : 1. The mean age of 100 patients at diagnosis was 46.82  6.94 and mean duration of diabetic age was 12.48 4.65. The mean of Glycosylated haemoglobin (HbA1c) in the study population is 9.29 + 1.57. Our study included 13% mild NPDR, 21% moderate NPDR, 49% severe NPDR, 13% PDR and 4% high risk PDR. 15% participants had CSME, 11% in NPDR and 4% in PDR. The age at diagnosis was significantly associated with the severity of retinopathy (p<0.0001). The severity of retinopathy and the duration of diabetes was found to be statistically significant (p=0.0267). There was significant association between visual acuity of the patient and the severity of retinopathy (p=0.006). Severity of retinopathy was not associated with life style (P=0.5869) and smoking (p=0.28915). There was noted a highly significant increasing trend of severity of retinopathy with raise in HbA1c (p=0.0003), with shift of HbA1c from mild NPDR to severe NPDR is highly significant (p<0.0001) and from moderate NPDR to severe NPDR is very significant (p=0.007). HbA1c was also significantly associated with presence of CSME (p=0.0166). FBS was not associated with severity of retinopathy and presence of CSME. The severity of retinopathy was significantly associated with duration of treatment by oral hypoglycaemic drugs (p=0.030) and not with insulin therapy (p=0.880). The threshold of HbA1c for occurrence of mild NPDR with 95% C.I was 7.6%. XI CONCLUSION: The poor metabolic control as demonstrated by high HbA1c is significantly associated with severity of retinopathy and presence of CSME. From the analysis of our study, we recommend to maintain HbA1c levels below 7.6% which may reduce the risk of development and progression of diabetic retinopathy. Duration of diabetes and high HbA1c levels are found to be the major predictors of diabetic retinopathy in type II diabetes mellitus.