DOCTOR'S ROLE IN EARLY DETECTION OF DIABETIC RETINOPATHY AND PREVENTION OF BLINDNESS FROM ITS COMPLICATIONS

Diabetic retinopathy (DR) is a microangiopathy, which is caused by chronic hyperglycemia, affecting the retinal arterioles, capillaries and venules, complications of which lead to incurable blindness. Approximately 10% of the diabetic population has type I diabetes mellitus (DM) which is diagnosed before the age of 30 years1 and rest is type II which is diagnosed after the age of 30 years. In UK 2% general population is affected by DM. In developed countries, diabetic retinopathy is an important and leading cause of blindness in working age group where as in developing western countries this figure occupy 12% of the blindness. In developing countries like Nepal, cataract still remains a main cause of blindness and diabetes is not considered as a major problem. However due to a rapid urbanization and modernization of population, diabetes mellitus is becoming an endemic disease and bringing a new challenge in blindness reduction program.


INTRODUCTION
The exact cause of diabetic microangiopathy is unknown. It is believed that exposure to hyperglycemia over an extended period leads to several hematological and biochemical changes which ultimately cause loss of pericytes, basement membrane thickening and microvascular (endothelial) decompensation.
Hematological and biochemical abnormalities responsible for severity 1-3 of retinopathy include: • Increased platelet adhesiveness • Increased erythrocytes aggregation • Abnormal serum lipids

DOCTOR'S ROLE IN EARLY DETECTION OF DIABETIC RETINOPATHY AND PREVENTION OF BLINDNESS FROM ITS COMPLICATIONS
• Defective fibrinolysis • Abnormalities in serum and whole blood viscosities etc.
The diabetic retinopathy has features of microvascular occlusion leading to retinal ischemia and vascular leakage. The ischemic retina is responsible for abnormal new vessels formation in the retina and in optic disc, which later on may be main cause of marked loss of vision (vision < 5/60).
Such conditions are vitreous hemorrhage, tractional macular detachment or combined mechanisms retinal detachments.
Vascular leakage on the other hand is responsible for exudative maculopathy, cystoid macular oedema or clinically significant macular oedema, which causes mild to moderate loss of vision.
After about 20 years of diabetes, nearly all patient with type I diabetes mellitus and more than 60% of patient with type II diabetes mellitus have some degree of retinopathy. 4

CLASSIFICATION
DR is classified on the basis of its severity. It has been attempted by Hirschberg in 1980 with the objective of recording the natural history of the disease, the time for intervention, and the mode of intervention and evaluation of its efficacy.
There are various classifications and most commonly used classifications 3,5,6 in current practice used:

CLINICAL FEATURES AND EARLY DETECTION OF DR
The prevalence of retinopathy in diabetic population increases with the duration as well as with the type of diabetes and age of the patient.
It is rare to find DR in children of less than 10 years of age. 7 Patient with DR changes may or may not have ocular symptoms. Mostly symptoms reflect the advanced stage of DR. However asymptomatic case is not excluded from the severity. It may have any stage of DR from no retinopathy to NPDR and HR-PDR. Presentations of DR and fundus evaluation are as follows: I. Asymptomatic-until macula is involved or VH or TRD occurs II. Defective vision -mild to moderate visual loss usually is caused by macular involvement where as marked loss of vision is due to VH or macular TRD III. Floaters -In diabetic patient having floaters of recent onset, VH should be suspected IV. Fundus examination -There are several methods of fundus evaluation like direct ophthalmoscope, indirect ophthalmoscope, slit lamp biomicroscopy and fundus photography etc. Direct ophthalmoscopy is simple and better method to detect diabetic retinopathiy changes. In first check up it should be performed after pupillary dilation so that posterior pole is well visualized. For dilation, eye drops like 1% tropicamide or 2.5% to 10% phenylephrine can be used. In diabetic patient, posterior pole examination is very important where retinopathy signs have to be looked for, particularly in and around the optic disc, macular area, superior and inferior arcades and temporal to the macula. DR signs include micro aneurisms (early sign of DR), 8 dot and blot hemorrhages, hard exudates, cotton wool spots, new vessels in and outsides the optic disc, vitreous or subhyaloid hemorrhages etc. (Table I )

: Normal Fundus of Right Eye (No DR changes even after 19 yrs duration of Diabetes mellitus)
If fundus evaluation is difficult due to cataract or any other reason, even after pupil dilation, it is advisable to be evaluated by an ophthalmologist.

GUIDELINE FOR MANAGEMENT
Although a lot of researches 11 have been done, there is no single modality to prevent or cure DR and it is still under research. The ways to prevent moderate to severe visual loss in diabetes are: 1. Careful eye examination and regular follow-up 2. Referral to ophthalmologist or vitro-retinal surgeon for laser photocoagulation treatment or vitrectomy surgery

EYE EXAMINATION AND FOLLOW UP SCHEDULE
Once diabetes mellitus is diagnosed, physician should evaluate the fundus as described above or should refer to an ophthalmologist expert in retinal diseases or to the vitreoretinal surgeon for base line evaluation. In subsequent visits apart from regular fundus evaluation, patient's physician (family physician. general physician, pediatrician etc) can play a key role in prevention of rapid progression of DR by regular assessment of diabetes mellitus and other high risks factors 12 e.g. diabetic nephropathy, hypertension, systemic infection, pregnancy, hyper-triglyceridemia or hyper-cholesterolemia, renal failure, renal transplantation etc. These uncontrolled conditions may lead to irreversible sight loss and even death of patient.
Hence it is important for patient's doctors* to plan a careful program of evaluation, education and follow-up of any ocular condition whether the patient is symptomatic or not in spite of having good vision. 13 Eye examination and follow up schedules are described in Tables  II and III. 14,15

REFERRAL TO THE OPHTHALMOLOGIST OR VITREORETINAL SURGEON
Timely detection and identification of DR stage are crucial in its management. 16 This ability entirely depends upon the experience and skill of the doctors (physician, ophthalmologist, and pediatrician) and also affected by the presence of hazy media (due to cataract), choroidal sclerosis and featureless retina. In such situations doctors can refer the case to a vitreoretinal surgeon.
There are few general criteria defined by ETDRS for referral and management of the diabetic retinopathy cases: 17 Clinically significant macular oedema (CSME) a. Retinal chickening located ≤ 500 µ from the center of the macula or b. hard exudates with retinal thickening of the adjacent retina located ≤ 500 µ from the center of macula or c. a zone of retinal thickening 1 disc area or larger in size located ≤ disc diameter from the center of macula Combined efforts of all doctors and strict adherence to above guideline and criteria can only make it possible to prevent unnecessary visual loss of patient with significant retinopathy. It will also be cost effective to the society and help to maintain normal life style of diabetic patients.