Ocular complications of diabetes mellitus
The fight against diabetes showing foot, eye, and heart as globe which are susceptible to diabetic complications.
10th World Congress of the International Diabetes Federation
in Vienna showing leaking retinal vessels. 
50 years of the Federation of Diabetes 1950-2000
Section 11 Special management problems
11.1 Pre-proliferative retinopathy
By definition, this stage precedes overt neovascularization, and is characterized 
by venous beading and dilatation, large blot retinal haemorrhages, cotton-wool 
spots (in the absence of systemic hypertension), intra-microvascular abnormalities, 
and areas of capillary underperfusion as shown by fluorescein angiography61
However, the definition of pre-proliferative retinopathy is difficult since not all 
patients who develop proliferative retinopathy pass through the preproliferative 
phase, and many do not show all the features described above. Accordingly, we 
recommend the concepts of ‘high risk’ and ‘low risk’ retinopathy (see section 2 on 
clinical classification).
It is, however, an important stage to recognize since 10 to 50 % of patients with
‘high risk’ (pre-proliferative) retinopathy will develop overt proliferative changes 
within 1 year62. Such patients require at least 4 monthly follow up to allow the 
earliest detection of proliferative changes. On theoretical grounds, all patients 
should go through the preproliferative stage. That this is not the case may well 
be due to the relatively transient nature of the some of the lesions. In addition, 
pre-proliferative retinopathy in the presence of a posterior vitreous detachment 
cannot a priori progress to proliferative retinopathy although rubeosis iridis can 
still occur (see below). Cotton wool spots have a time course of 6-12 months, 
and blotch haemorrhages as well as IRMA’s disappear once extensive capillary 
closure has developed.
Opinions differ on whether to treat pre-proliferative retinopathy. Most studies 
have failed to show any benefit, provided that adequate follow up is achieved63
In mild forms where less than two of the features of the condition are present,
and particularly where there are only a few cotton wool spots, progression is not 
certain and indeed spontaneous regression may occur64.  In the United States 
the preferred practice in cases of bilateral pre-proliferative retinopathy is to 
treat one eye with pan-retinal photocoagulation and observe the second eye 
at three monthly intervals.
11.2 Rubeosis iridis
This is a manifestation of severe retinal ischaemia and heralds the onset of 
rubeotic glaucoma. In the presence of clear media, further immediate 
photocoagulation should be applied since regression can be induced although 
this is perhaps better documented following central retinal occlusion65. However 
rubeosis is often associated with advanced PDR rendering it impossible to apply 
further laser due to vitreous haemorrhage. In these circumstances prompt 
vitreous surgery is required to enable preoperative photocoagulation to be carried 
out (see above). The results of the Early Vitrectomy Study show the benefits of 
surgery in eyes with severe neovascularization and vitreous haemorrhage54; the 
presence of rubeosis indicates that surgery cannot be further delayed. Ultrasound 
examination is mandatory to exclude retinal detachment, since co-existing rubeosis 
implies a poorer prognosis for surgery (see above).
Glaucoma due to rubeosis responds poorly to standard trabeculectomy procedures66
When trabeculectomy is combined with mitomycin-C however, the results are more 
encouraging67, and compares favourably with other anti-proliferative agents such as 
5-Fluorouracil68 as well as other surgical procedures such as drainage tubes and cyclo-
cryotherapy. When it is possible to apply further photocoagulation, trabeculectomy 
with mitomycin should be delayed for 1-4 weeks to allow as much regression of the 
rubeosis as possible prior to surgery66. In eyes which are already blinded by rubeotic 
glaucoma, topical steroids together with atropine is the appropriate palliative 
11.3 Systemic hypertension
In both IDDM and NIDDM patients systemic hypertension is commoner than in non-
diabetics69,70 (see risk factors above). Since it is well recognized that systemic 
hypertension hastens the development of background and proliferative 
retinopathy4,5,20,71, it is important that ophthalmologists identify signs of coexisting 
hypertensive retinopathy. Some of the features of accelerated hypertensive 
retinopathy such as retinal haemorrhages, cotton wool spots and capillary closure 
are similar to diabetic changes, but there are often subtle differences with, in 
particular, flame shaped retinal haemorrhages being characteristic of hypertension. 
The thickening of the arterial wall of the retinal vessels together with A-V nipping 
are also consistent features of systemic hypertension.
Whilst the association between hypertension and diabetic retinopathy is established, 
there are few studies regarding the effects of treatment of hypertension on diabetic 
retinopathy. In one reported study, it has been shown that treating hypertension 
minded result in improvement of retinopathy72. Since both diabetic retinopathy and 
nephropathy are the result of microangiopathy, it should be the concern of those 
treating patients with retinopathy to attend to concomitant hypertension. ACE 
inhibitors appear to control hypertension well in these circumstances and may 
therefore be the drugs of choice.
At the present time, it is reasonable to expect ophthalmologists to recognize the 
effects of hypertension on diabetic retinopathy and if not already diagnosed, to 
draw it to the attention of the physicians. It should be realized however, that 
prevention of the visual damage associated with retinopathy can only be achieved 
in the early stages. Treatment of established maculopathy or PDR is not 
accompanied with visual improvement, only with halting the disease process.
11.4 Retinal vein occlusion
Diabetes is recognized as a predisposing factor in the causation of retinal venous 
occlusion73. Many cases of branch or central vein occlusion occur in diabetics 
without retinopathy in which the management is the same as in non-diabetics 
ie pan-retinal laser photocoagulation if significant areas of capillary non-perfusion 
have been identified by fluorescein angiography, in order to prevent retinal 
neovascularization or rubeosis iridis74. Although the natural history of branch 
retinal vein occlusion is probably little different in diabetics without retinopathy, 
there is a significant higher rate of neovascular glaucoma75 and such patients 
require evaluation of the extent of retinal ischaemia by fluorescein angiography 
to enable timely photocoagulation to be applied. 
Retinal venous occlusion occurring in patient with established diabetic retinopathy 
may prove more difficult to assess and treat. Where there are already extensive 
haemorrhages and exudates from diabetic retinopathy, the subsequent development 
of a venous occlusion can be missed and must be considered where ‘asymmetric 
retinopathy’ has developed
Epidemiology Clinical features Risk factors Screening
Lasers and lenses. NVD,, NVE.. Maculopathy
Vitrectomy. Cataract Special problems Counselling
References.. AAO guidelines Atlas of Retinopathy Contact lenses
Main index Main page.