An optometric pespective on screening
As an optometrist who is involved in a retinal screening programme using slit-lamp biomicroscopy and who also uses a digital retinal camera in practice, I have a number of comments on the exchange of views regarding screening for diabetic retinopathy. I believe that the terms “technical failure” and “ungradeable images” are often used interchangeably, when in fact they are not the same. A technical failure implies that the camera did not obtain an image when it should have done, whilst an ungradeable image does not necessarily imply any failure of the equipment. This confusion has given rise to the myth that digital cameras will reduce the number of ungradeable images compared with film. A common technical failure is due to blinking, usually resulting in no useful image. This is identified immediately with a digital system, and a further photograph taken. Cataracts are a common cause of ungradeable images but there is no equipment failure. So digital cameras reduce some technical failures, but there is no evidence that they are intrinsically better with poor images. However, it is the case that a good retinal view can often be obtained through cataract by slit-lamp biomicroscopy when a photograph is of poor quality. Taylor and Riley found in a general optometric practice that 6% of their patients with diabetes were ungradeable by any means, whilst a further 12% were ungradeable from photographs alone. The usual reason was cataract, with the majority of these patients aged over 70. Simply referring any patient with an ungradeable photograph, as suggested by Clements, will swamp over stretched ophthalmologists, unless an efficient 2nd level of grading is available. Clements suggests that training optometrists to use fundus lenses may be challenging. This plainly misunderstands the current competencies of optometrists, most of whom use such lenses regularly and many of whom are already involved in the 60 or so retinal screening programmes throughout the UK. Patient education and involvement is very desirable, as is providing an instant result for the patient, but both of these require the ability to grade fully at the time of photography, which will require an ophthalmologist, an optometrist or a highly trained grader. The most appropriate screening arrangements will vary from area to area. With a large general practice, a visiting mobile camera may make sense. In my area, with a high proportion of single-handed GP practices, it may be more problematic. Given the current interest in retinal cameras, I predict that in a short number of years the largest installed base of such cameras will be in optometric practices. Most of these will be recent models and will meet the resolution standards of the National Screening Committee. It would seem sensible to make use of these rather than duplicate costs. 1. Taylor L, Riley A. Internal Practice Audit. 2001 Optometry Today 27th Oct. 2001.
Competing interests: No competing interests