Having previously organised events looking at glaucoma and diabetes, Haag Streit UK recently organised a day of lectures and workshops based upon macular disease and the latest technology available in imaging and assessing retinal disease.
The theme was introduced with an overview of retinal anatomy and its relation to disease from Bill Harvey (Optician clinical editor). Most common retinal lesions may be identified by their shape, colour, definition and a knowledge of their speed of presentation. Leakage from pre-capillary beds, as occurs with diabetes for example, results in either red cell collection or lipid precipitation from the plasma. These haemorrhages and exudates are restricted in their spread by the fact that they are present at the deeper layers of the retina (layers 5 and 6 typically) meaning that they adopt characteristic dot (or if bigger, blot) and discrete exudate appearances, well defined and distinct.
For significant leakage sites, the exudates may precipitate at the edge of the area of oedema, resulting in a circinate or arcuate lesion. This alerts the practitioner to the fact that the site of the leakage is central to the circinate lesion. Drusen, on the other hand, are not related to blood vessel disease but rather to the build up of photoreceptor activity breakdown product. Their distribution tends to follow the pattern of photoreceptor distribution and the lesions are more likely to be seen at the macula. An early indication of possible subsequent maculopathic progression, Harvey pointed out that drusen are not necessarily a sign of AMD but should alert the practitioner to look carefully for drusen build up, atrophic changes or pigment build up as signs of AMD.
Opening the floodgates
Chris Mody (Royal Hallamshire Hospital, Sheffield) gave an excellent review of the use of angiography in AMD investigation. He has a wealth of experience in this field and remembered using the Zeiss FF camera from the early 1970s. The first human angiogram was carried out as early as 1919 by Hesuer and proposed as a method of visualising retinal circulation by Novotny and Alvis in 1961. Recent years have seen the introduction of indocyanine green as a variation (see Optician, January 18, 2008). Fundus camera angiography had some limitations, such as a reliance on pupil dilation, light scatter from ocular tissues and no real time recording. Some of these are addressed by scanning laser ophthalmoscopy technology and Mody described his use of the Heidelberg Retina Angiograph which allows real time recording, better depth information and the ability to review the whole angiogram at any one time. Clarity and patient compliance are vastly improved, though this comes at a cost, with each unit averaging at around £80,000.
Mody went on to describe some of his studies, including one showing that oral fluorescein angiography is as effective as intravenous when assessing diabetic retinopathy and cystoid macular oedema, but less so for macular ischaemia.
Mody gave a second talk on the trials of anti-angiogenic treatments for choroidal neovascular AMD. Rather soberingly, he outlined how the specialised and repeated nature of the treatmnents were likely to prove a major burden on hospital resource. If one considers a two year treatment programme which involves six treatments and nine follow ups in the first year, and two treatments and 10 follow ups in the second year, this would mean that just seven patients required 105 patient episodes, 210 would require 3,050 episodes. The answer may have to be the inclusion of community-based practitioners in the follow up to prevent hospitals becoming completely congested.
Spectralis
Heidelberg has introduced its Spectralis OCT to the market recently and, as explained by the company's Dr Stephan Schulz, this has some significant features unique to it. The Spectralis name includes the OCT, and the angiogram SLO, available individually or as a combined unit. The spectral domain OCT includes eye-tracking which allows automatic repeat scanning at exactly the same position. This means improved accuracy for patients if there are eye movements, but also makes serial monitoring more accurate as the operator may be confident that exactly the same structures are being compared. Very high quality images are enhanced further by a Heidelberg Noise Reduction Technology function which gets rid of 'speckle noise'. A full review of this instrument will appear in Optician in the coming months.
AMD treatments
Adnan Tufail (consultant, Moorfields) rounded up proceedings with an excellent review of current AMD treatments. He began with a reminder that AMD has not just visual impact, recent surveys suggesting that up to a third of AMD patients suffer clinical depression. In explaining anti-angiogenic action, he said that angiogenesis is a form of wound healing and a natural process. He also outlined how original theories of 'wet' AMD had assumed it to be an inflammatory event which had then been dismissed. The latest models for CNV events include a complement activation inflammatory component in VEGF formation and activity so in some ways things had come full circle. In underlying the potential for anti-angiogenesis, Tufail emphasised the importance of practitioners understanding the benefits of giving up smoking and recommending an anti-oxidant rich diet.
With workshops on photography, imaging and indirect ophthalmoscopy, this was an informative and worthwhile day. Look out for future events.