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Finding diabetic retinopathy: tools for detection and management

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Figure 1. Axial B Scan showing cystoid macular oedema, VA = 6/12

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Dr Simon Little

PhD MScOptom GradCertOcTher

North Lakes Optometry QLD

Product

Keeler Spot Retinoscope

Topcon SL-D7 slitlamp

Volk SuperField NC lens

Volk Super 66 lens

Volk SuperQuad 160 lens

Topcon 3D OCT-1 Maestro

 

Most of us examine diabetic patients in our practices every day. We have the knowledge and skills to detect and monitor diabetic eye disease, and are on the front line in the detection and monitoring of diabetic retinopathy. Liaising with general practitioners, diabetic educators, diabetologists, endocrinologists and ophthalmologists, we are essential contributors to diabetic health care, despite the lack of a formal comprehensive structure for diabetic eye care.

In my practice, all diabetic patients are tested for retinopathy at first presentation. Many of my diabetic patients are referred by their general medical practitioner or diabetic nurse when their diabetes is first diagnosed. Retinopathy is not unusual at diagnosis, particularly for those patients who might have been diabetic without symptoms for some years. I also see some patients with diabetic eye disease who subsequently have the diagnosis of diabetes confirmed.

Diabetic eye examination

After careful history-taking, visual acuities are recorded, both at six metres and at near for each eye. I then perform subjective refraction, including pinhole acuity as required. I find my old Keeler Spot Retinoscope very useful for getting an impression of the clarity of the ocular media; it is particularly good for detecting posterior subcapsular lens opacities.

It is important to establish whether visual acuity less than 6/6 and N5 is due to developmental causes such as amblyopia, or potentially progressive causes such as cataract or diabetic maculopathy. Any unexplained reduction in vision or abnormal level of vision requires further investigation or referral, as would anomalies of binocular vision. Cranial nerve palsies affecting ocular motility are more common in these patients.

I use a Topcon SL-D7 slitlamp to check the anterior eye, particularly looking for rubeosis iridis as well as cataract, and so on. I use a Volk SuperField NC lens for an initial assessment of the vitreous and fundus. If I see sight-threatening retinopathy at this stage in a patient who is not already under the care of an ophthalmologist, I may refer immediately. The level of Medicare benefit payable simply does not permit further investigation when it is obvious that a specialist should become involved.

Otherwise, I use a Volk Super 66 lens (equivalent to a Digital 1.0x) to assess the optic nerve heads and maculae. This lens allows good stereopsis for macular oedema detection and good magnification to look for new vessels on and around the discs. A good and possibly better alternative to this would be the Volk Digital High Mag with 1.3x magnification. The reviews for this lens are good, but I have yet to try one.

For wide-field viewing I use a Volk SuperQuad 160 lens, which gives a distortion-free view out to the ora serrata when pupils are sufficiently dilated. Using this lens at the slitlamp is much better for my back than using a headset BIO and the view is much better as well. I first used the SuperQuad 160 lens when working in hospital eye departments in the UK and have yet to find a better way of obtaining a wide-field overview of the ocular fundus.

In addition to the slitlamp and Volk lenses, I now use my Topcon 3D OCT-1 Maestro to take retinal photographs and to check for and monitor macular oedema. While this wonder of technology, which sits next to my slitlamp on a double-width table, can take B scans of sight-threatening cystic changes in the macula (Figure 1), it is also useful in more subtle cases. Primary care optometry has great case-finding potential. Our role in the detection and monitoring of diabetic eye disease should be recognised and funded as an important aspect of diabetic health care.

CASE REPORT

Fit and well but macular haemorrhages lurk

AP, a 41-year-old house painter presented with early presbyopic symptoms. He had no other symptoms and reported good general health and an active lifestyle including playing touch footy and riding a mountain bike on rough terrain for about one hour several times a week. His last medical examination had been about a year earlier. He had been checked for type 2 diabetes as his father and older brother are both type 2 diabetic patients.

He read 6/4.5 R and L unaided and required a +1.00 near add to allow him to work comfortably at 30 centimetres. Apart from asymptomatic small, flat, nasal-sided pterygia, the external eye examination was unremarkable.

Slitlamp biomicroscopy with the Super 66 lens revealed a few dot haemorrhages just within the foveal avascular zone in each eye (Figure 2).

E002 Figure 2. Dot haemorrhages around the macula-F

Figure 2. Dot haemorrhages around the macula

Scrolling through the B Scan on the OCT images shows the position of each haemorrhage in the inner plexiform layer and the shadow cast on the layers below (Figure 3).

E002 Figure 3. Axial B Scan showing haemorrhage position and the shadow below it-F

Figure 3. Axial B Scan showing haemorrhage position and shadow below it

ETDRS grid on the OCT confirms the absence of macular oedema (Figure 4).

E002 Figure 4. OCT ETDRS grid showing normal macular thickness-F

Figure 4. ETDRS grid showing normal macular thickness



As this patient had macular haemorrhages, he visited his GP to arrange a fasting blood sugar test. Type 2

diabetes was confirmed a few days later. Because his maculopathy was non-sight-threatening, I will review him again in six months. Co-management with the GP will continue unless and until we need to get an ophthalmologist involved.



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