Diabetic retinopathy is the most severe of the several ocular complications of diabetes (Frank, 2004). It has few visual or ophthalmic symptoms until visual loss develops (Davis, 1998). Studies such as the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study Group (UKPDS), have concluded that loss of vision and blindness can be prevented by early detection and treatment (Cunha-Vaz, 1998). The National Retinal Screening Programme is aimed to help achieve this goal by prompt identification and effective treatment if necessary of sight threatening diabetic retinopathy, at the appropriate stage during the disease process. Although laser treatments have been available for past 30 years, unfortunately diabetic retinopathy remains a leading cause of blindness amongst the working age population (Kohner, 2007).
This is an opportunity for me to add to my continuing professional development.
I hope to share my newly acquired wealth of knowledge on the subject with my colleagues, which in turn should serve to raise awareness of the serious nature of this complication. I hope to better educate my patients of the importance of adhering to national retinal screening programme and attempt to explore reasons as to why the uptake of this free service is not as much as one would hope.
The main pathophysiological defect lies at the level of the retinal capillaries, which undergo progressive degeneration over time. This results in haemorrhages and exudates, along with formation of microaneurysms and closure of small vessels .The affected segments of the ischaemic retina as a consequence of these changes elaborate growth factors encouraging new vessel formation and fibrous ingrowth (Barnett, 2008).
Classification is based on the degree of pathology seen on slit-lamp examination of the eye. It is not correlated to the degree of vision, which may be almost normal until the very late stages of the disease (Patient UK).
The following classification highlights the recognized progressive stages of retinopathy.
(Taken from Barnett, 2008).
Background Retinopathy – This is common even at diagnosis and includes microaneurysms, dot retinal haemorrhages and hard exudates without visual deterioration.
Maculopathy – These are retinal ischaemic changes n the macular region, including ring-shaped exudates. Ischaemic maculopathy due to capillary closure within the macular area or a mixed form of the two may also occur. Maculopathy is the most common cause of blindness.
Preproliferative retinopathy-This may include cotton wool spots, (areas of retinal ischaemia /infarction), venous abnormalities. These changes are highly predictive of the development of the proliferative retinopathy within 2 years.
Proliferative retinopathy-This indicates severe ischaemia of the retina leading to new vessel formation in the optic disc or in the periphery of the retina or iris. Untreated this can cause visual loss or blindness. New vessels formation may b asymptomatic until they rupture leading to pre-retinal subhyaloid or vitreous hemorrhage.
Maculopathy can co-exist with any of the other stages.
The duration and degree of hyperglycaemia is highly indicative of development and progression of retinopathy (Fong, 2004); however it is difficult to comment whether this implies aggressive disease or poor control.
Hypertensive, obese and individuals with dyslipidaemia are also at an increased of developing retinopathy. Pregnant women may occasionally develop rapidly progressing diabetic retinopathy (Patient UK).