Preliminary Assessment of the Usefulness of the DIO

Peter Frampton Begins Clinical Trial of the DIO Digital Indirect Ophthalmoscope

Preliminary Assessment of the Clinical Usefulness of the DIO Hand Held Fundus Camera

By Peter Frampton
MCOptom BappSc (Optom)(AUS) MSc (Dist) Dip Tp (AS) Dip Tp (SP)

INTRODUCTION

As part of our ongoing investment into improving patient care we purchased a DIO Hand Held Fundus Camera, six months ago. Our Clinical Governance audit had identified the need for a more versatile camera but until the DIO we were not convinced any would have the image quality necessary for diabetic retinopathy screening. Since purchasing the camera we have now had a software upgrade and the image quality is even better.  At the time of acquisition we did not intend the DIO to replace the Topcon NW6, but rather to allow photography of patients who would otherwise be unable to sit at a camera or slit lamp.  If the DIO gains NSC approval, I believe it would be a great advantage for practitioners who see a lot of domiciliary or less mobile patients.

Our practice has long been committed to improving access to care. Our award winning patient transport service was introduced in 2002 specifically to facilitate access to a fully equipped practice (Frampton 2007). (FIG 1 - PHOTO OF VAN)

Our initial service audit (Frampton 2007), before DIO purchase, included an outcome audit of patients with Diabetic Retinopathy. Of the 100 consecutive patient records audited, 39 had diabetes. The availability of the collection service dictated that we tended to see the majority of patients who find it difficult to access care. Consequently, 13% of patients with diabetes, brought in via the collection service, were unable to sit at the camera or slit lamp, severely compromising the screening sensitivity. This failure rate, due solely to physical incapacities, is probably a conservative estimate as it does not include the patients who could not access the practice, even with the transport facility, and who would require a true domiciliary visit. I am unaware of national audit figures, but a failure rate of 20% due simply to an inability to access a standard camera would not be unreasonable.

THE DIO

The instrument can be mounted at a slit lamp or used hand held. (FIG 2 AND FIG 3 - PHOTOS OF DIO AT SLIT LAMP AND HAND HELD)

Unlike standard fundus cameras there are no integrated patient fixation points. The patient is asked to fixate on the photographers shoulder. Regardless of the retinal view required the photographer places the internal target, not visible to the patient, on the Optic Nerve. The retinal view required is set at the PC which then moves the fixator so that the new field is gained once the fixator is re-aligned with the ON. The camera defaults to a central photo when either right or left eye is designated.

Early difficulties were found when photographers, experienced with conventional cameras, tended to place the fixator at the centre of the field required. Once accepted that the patient is not expected to move the eye but the photographer moves the camera it seems infinitely logical to line the fixator on the ON, the most identifiable landmark within the eye.

Initially using the camera mounted at the slit lamp gave new operators more confidence, however in many respects the unit is more easily used hand held as the operator can readily pivot the camera on the supporting thumb to line up any fundus view.

The field of view is 50°x40°, greater than conventional cameras. The rectangular image seems to generate initial concern with new users; however the fault here is in our traditional expectation of what a fundus photograph should look like and is not a fault of the DIO.

The instrument is extremely robust and comes with a strong carry case. Its’ size and robustness means we routinely take it to domiciliary visits as well as move it from room to room within the practice. This feature has to be attractive to mobile diabetic screening services; the DIO would not require a specialised vehicle, could be transported to, and accommodated in, GP surgeries easily and would undoubtedly be less susceptible to transport and storage breakdowns.

FULL CLINICAL AUDIT

We are now commencing a full clinical audit.

All able patients will be photographed with both the conventional Topcon NW6 and the DIO. The photographs will be compared for grading failures and pathology identification to assess sensitivity and specificity.

A second aim is to assess, over a larger patient sample, the amount of patients unable to be photographed without the DIO.

Our, admittedly limited, experience with the upgraded software is very promising. Figure 4 shows central photos of the same patient taken with the conventional Topcon NW6 and the DIO. The clinically significant features of retinopathy are identifiable in both images and I am confident that the full audit will demonstrate equivalent sensitivities and specificities for both cameras.

REFERENCES

Frampton P. (2007). Ministry of Transport. Optician, 09/02/07; 25-27.