RETINAL FEATURE DETECTION SERVICE PROTOCOL CONDITION GUIDANCE

1 Diabetic retinopathy

Diabetic retinopathy causes damage to blood vessels of the eyes; diabetic retinopathy does not usually affect sight until these changes are advanced. At least 75% of people who have diabetes for more than 20 years will have some form of DR (World Health Organization, 2014). Annual screening is an effective way of preventing sight loss caused by diabetes, but if no treatment is given this can result in vision loss. Known risk factors that increase the risk of developing DR include duration and type of diabetes, poorly controlled HbA1c, high blood pressure, retinopathy stage and gender. DR develops gradually and the severity of DR is classified using grading classifications that correspond to disease progression.
1.1 R0 classification
The R0 classification occurs when no diabetic retinopathy or maculopathy is present, and there is little chance that the patients vision is effected other than possible blurring from lens swelling due to hyperglycemic episodes or cataract formation due to poor sorbital metabolism (see Figure 1 for an example image of a patient with a R0 classification).

Figure 1: An example image of a patient who would be classed as R0. There are no visible signs of DR. The image is clearly visualised as we can see the retinal vessels within 1 disk diameter of the centre of both disc and fovea.

1.2 R1 classification

The next stage in disease progression is a R1 classification. This is not too serious, however there is some noticeable pericytic loss in the blood vessels, perhaps a few small microaneurisms (circled in yellow in Figure 2) and/or superficial flame haemorrhages may be visible in the retina. There may also be some exudates where leakage takes place. The patent is notified about these changes but no further action will be taken until next year’s screen. Again, as with the R0 classification, there is little chance of the patients vision being affected over all (see Figure 2 for an example of the fundus image of a patient with an R1 classification).

Figure 2: An example of an R1 classification. Such an image may contain background microaneurysm (s) retinal haemorrhage(s) ± any exudate not within the definition of maculopathy. This image shows a yellow circle around a microaneurysm in an otherwise ‘quiet’ retina with no other observable signs of retinopathy.

1.3 R2 Classification

R2 Classification is defined by substantial amounts of pericytic damage that lead to deeper rounder haemorrhages. Axoplasmic flow blockage may form Cotton Wool Spots (CWS) that result in ischemic areas. Typically this will stimulate a release of vascular endothelial growth factor hormone (VEGF) in the retina leading to intra retinal microvascular abnormalities (IRMA). These are tiny new vessels trapped within the retina (circled in yellow in Figure 3), venous beading and venous loops. Multiple deep, round or blot haemorrhages are also symptomatic of R2. Patients are refereed for non-urgent referral to the hospital eye de
partment as there is significant risk to their vision. Patient may already be suffering with some vision loss

Figure 3: An example of the R2 classification. This figures depicts Pre-proliferative venous beading, venous loops or reduplication, intra-retinal microvascular abnormalities (IRMA), multiple deep, round or blot haemorrhages, and some cotton wool spots seen inside the yellow circles.

1.4 R3A Classification

A fundus image that is classed as R3A typically contains new vessels at the disc (NVD) or elsewhere (NVE) triggered by VEGF. These new vessels can proliferate on the surface of the retina growing towards ischemic areas. This deranged repairing mechanism is the cause of vitreous and sub-haloid haemorrhages. New vessels are often supported by a structure of fibrous tissue, these can adhere to parts of the retina causing significant traction, detaching or distorting of the retina. Patients can become blind if haemorrhage occurs as a result (circled in yellow in Figure 4).

Figure 4: This image demonstrates the R3A classification. Proliferative new vessels on disc (NVD) new vessels elsewhere (NVE) and pre-retinal haemorrhage (circled in yellow on the right).

1.5 R3S Classification

The R3S classification is made if the proliferate features appear stable in comparison to the previous year’s images (exhibiting no change) with the inclusion of a photocoagulation grade (P1) (see Figure 5). These patients can stay in surveillance indefinitely until such time as the referral outcome grader (ROG) adds them back in to screening. Doing so will prevent the patients from being unnecessarily referred back to the hospital eye service by inexperienced graders unless reactivation of stable treated retinopathy or referable non diabetic retinopathy is found.

Figure 5: An example of stable R3S DR.  Proliferative features including fibrous tissue (with no traction) and round laser photocoagulation burns that indicate previous laser treatment are present. There are no bleeds or other retinal features that have worsened since discharge from the eye clinic.

1.6 M1 Classification

Finally the M1 Classification indicates maculopathy, pathology associated with the macula. Maculopathy, is typically as a result of ischemia (no blood circulation) or oedema (water logging from blood plasma) affecting the macula. Ischemic maculopathy is impossible to treat because the starved blood cells die. Oedema on the other hand may respond to treatment. Microaneurysms and haemorrhages overlaying the macular do not necessarily mean significant leakage is occurring, however if these features are within one disc diameter of the centre of the fovea with an accompanying visual acuity (VA) of worse than 6/12 there may be a relationship. This patient would be referred on for urgent laser treatment.

Figure 6:  Shows an example of a retina that would be graded M1. Exudates (lipids) can be seen within 1 disc diameter (DD) of the centre of the fovea. These features typically appear as a line towards the centre of the fovea (tracking), or as a ring (circinate) around the centre of vessel plasma leakage.

2 A central retinal vein occlusion (CRVO) (a) and Branch retinal Vein Occlusion (BRVO) (b), both are the result of  hypertensive haemorrhaging within the retina which is a common finding requiring urgent referral, if caught early enough could prevent further damage occurring including blindness

Figure 7: Image showing a central retinal vein occlusion (a) and a branch retinal vein occlusion (b). Within this image we can see the optic disc, and many superficial flame shaped haemorrhages (typical of hypertensive bleeds) radiating from the optic disc out along the nerve fibres giving the illusion of a flame.

3 Central retinal atrial occlusion (CRVO) (a) and Branch retinal atrial Occlusion (BRVO) (b), both are the result blockage typically located in the bifurcation of an artery within the retina.

Figure 8: These images show atrial occlusion which may have been cause by plaque from the carotid artery, if the microembolism is spotted early enough a referral may lead to an intervention that could not only prevent blindness, but also a stroke and potently death.

4 Dry AMD This may indicate that a patient is entitled to claim for CVI registration / welfare benefits for vision loss / prevent them from driving if necessary

Figure 9: Showing confluent patches of drusen (a) and geographical atrophy in dry AMD

5 Wet AMD this is one of the most common forms of blindness in the aging population if discovered early enough can be successfully treated and vision can be restored.

Figure 10: Showing a sub retinal neovascular membrane (a) interestingly when photographed the previous year is was not visible in the traditional ‘Redfree’ green/blue viewing channel (b), but it was visible in Spectra’s  red channel filter (c)

6 Optic disc swelling Papilledema

The swelling of the optic nerve as it enters the back of the eye due to raised intracranial pressure, If detected early enough it can markedly change the prognosis for patients identified and could potentially save their life.

Figure 11: Showing the swollen looking optic disc sometimes difficult to see without clear fundus imaging

7 CHERPE Congenital Hypertrophy of the Retinal Pigment Epithelium – Multiple, bilateral lesions can be associated with Gardner’s syndrome, an autosomal dominant disease which invariably results in colon cancer by the fifth decade of life. Any suspicious lesions will be reported on if seen.

Figure 12: Showing this darkened patch and is sometimes misdiagnosed as a choroidal nevus, sometime multiple CHERPE can be spotted that look like paw prints on the back of the retinal and are sometimes referred to as ‘Bear tracks’

8 Choroidal Nevus Where detected this patent images should be compared to previous to look for change or suspicious features this can indicate possible melanomas and potentially save a life.

Figure 13: showing a choroidal nevus within the retina, most are perfectly harmless although can be difficult to find, however Spectra’s Red channels makes light work of identifying these lesions.

9 Cataracts are more common in diabetic patients.

In addition the fundus can vary in colour due to differences in the retinal pigmented epithelium between individuals. For example the retina may appear green or brown in Asian and Afro-Caribbean eyes. This difference in coloration coupled with a media opacity can hinder a graders ability to detect retinal pathology as the images may appear blurred or murky.