Authors:
Farid Al-Zawaideh MD, FRCOphth *, Jawad Ma'ayah MD**, Walid Qubein, MD*

* From the Department of Ophthalmology in Royal Medical Services.
** From the Department of Internal Medicine in Royal Medical Services.

Correspondence:
Dr. Farid Hani Al-Zawaideh, uveitis and medical retina specialist at Royal Medical Services.
E-mail: fareedhani72@yahoo.com

Introduction

Diabetic retinopathy is a leading cause of blindness in industrialised countries and a major cause of blindness in the population of working age^1-2. The prevalence of diabetic retinopathy has been reported ranging from 8% to 55.6%^3-4. Few reports have estimated the prevalence of diabetic retinopathy in elderly patients to be less than that in young patients ^5-6.

The prevalence of diabetic retinopathy is higher in type I diabetics than in those with type II disease^5,7. Prolonged hyperglycaemia and increased levels of HbA1c is reported with higher risk of retinopathy⁸. Other factors which were also reported with higher risk of retinopathy include duration of diabetes⁹, serum creatinine levels 10 and serum cholesterol¹¹.

The aim of this study was to estimate the prevalence of diabetic retinopathy in patients diagnosed to have diabetes after the age of 60 and to study its relationship with type and duration of diabetes, HbA1c level, and cholesterol and creatinine levels.

Patients and Methods

This study was conducted on Prince Ali Ben Al-Hussein Hospital in Karak city in Southern Jordan during the period between November 2006 and October 2007. 170 diabetic patients over the age of 60 attending internal medicine clinic were enrolled in the study. Full medical history was taken including type and duration of diabetes. Investigations included HbA1c, serum cholesterol, and creatinine measurement. All patients were referred to an ophthalmologist. Ophthalmologic examination included Snellen's visual acuity, anterior segment examination via slit lamp, and posterior segment examination via +78 lens.

Fluorescein angiography was performed in visually threatening retinopathy. Diabetic retinopathy was staged and studied in relation to type and duration of diabetes, glycaemic control, and creatinine and cholesterol levels. Stages of diabetic retinopathy included no retinopathy, mild, moderate and severe non-proliferative retinopathy and proliferative retinopathy. Severe non-proliferative retinopathy and proliferative retinopathy and clinically significant macular oedema were considered as severe diabetic retinopathy.

The HbA1c levels were estimated using a high performance liquid chromatography method and was divided into three groups (less than 5%, 5-7%, and more than 7%) and studied in relation with retinopathy. P-value was calculated and was considered significant if less than 0.05.

Results

The mean age of patients was 66.4 with 1.2:1 male to female ratio. 152 patients (89.4%) had type II diabetes mellitus and 18 patients (10.6%) had type I. 34 patients (20%) were found to have diabetic retinopathy; half of them had severe non proliferative or proliferative diabetic retinopathy (Table 1). Clinically significant macular oedema was evident in 20 patients (11.8%). Table 2 shows relation between diabetic retinopathy and the studied risk factors. Diabetic retinopathy was more significantly associated with type I diabetes, duration of diabetes of more than 10 years and HbA1c level of more than 7%. Higher serum cholesterol and creatinine levels were associated with more risk of retinopathy but this was not statically significant.

Table 1 Number and percentage of patients according to stage of diabetic retinopathy.

a Diabetic retinopathy
b Non proliferative diabetic retinopathy
c Proliferative diabetic retinopathy
d Clinically significant macular oedema

Table 2 Relation of diabetic retinopathy with type and duration of diabetes, glycaemic control, serum creatinine and cholesterol.

Discussion

The prevalence of diabetic retinopathy was reported to range from 8% to 55.6% by different investigators^3-4. Few reports have studied the prevalence of diabetic retinopathy in elderly patients; some of them found it to be lower than in younger patients^5-6. Cahill M and his colleagues found the prevalence of diabetic retinopathy in patients diagnosed to have diabetes mellitus after the age of 70 to be 14%¹². In our study the prevalence was 20% which is about half of the overall prevalence in our area.

Half of the patients with diabetic retinopathy were found to have type I diabetes mellitus though this type was found only in 10.6% of patients. The vast majority of patients with type I diabetes (17 out of 18) had diabetic retinopathy and almost two thirds of patients with severe retinopathy were of insulin dependant type. We recommend a close follow up period for patients with insulin dependant diabetes. Regarding duration of diabetes, we confirmed what was previously found that the longer the duration the higher risk of retinopathy. Our data found statistical significance of the duration of diabetes was more than 10 years.
Poor glycaemic control is reported with higher risk of diabetic complications. The HbA1c, glycated hemoglobin test, or glycohemoglobin is an important blood test used to determine how well diabetes is being controlled. It provides an average of blood glucose control over a 6 to 12 week period. We studied the risk of diabetic retinopathy in three sub groups according to HbA1c. The first group showed good glycaemic control with HbA1c < 5%, the second group with fair control (HbA1c between 5-7%) and the last group with the poor control with HbA1c > 7%. A reciprocal relation was found between retinopathy and the level of HbA1c; this was statistically significant with HbA1c of more than 7%. It is recommended that glycaemic control be strongly promoted and that HbA1c investigations routinely carried out.

High blood urea, creatinine cholesterol, and triglycerides are also reported as risk factors for the development of retinopathy. Our data showed high incidence of retinopathy in patients with elevated cholesterol and creatinine but this was not statistically significant.
In conclusion, the prevalence of diabetic retinopathy in elderly patients is lower compared to overall prevalence in other age groups. Factors with higher risk of progression included type I diabetes, longer duration, poor glycaemic control and higher cholesterol and creatinine levels. We recommend a regular ophthalmologic examination for patients older than 60 years and more frequent follow up visits for patients with insulin dependant type or with disease onset of more than 10 years with regular laboratory monitoring with HbA1c, serum cholesterol and creatinine.

References