(display so that they can be graded) to the same level as modern digital cameras. 3. That the device compares favourably in terms of cost effectiveness and affordability compared to digital photography when used in a screening programme. 8.5 GRADING AND REFERRAL A national consensus grading protocol was agreed for England and Wales27 with the following key principles: - to detect any retinopathy - to detect the presence of sight threatening diabetic retinopathy(STDR) - to allow precise quality assurance at all steps - to minimise false positive referral to the hospital eye service The grading and referral protocol is available on the English Programme website1 . A Grading and Assessment Sub-Committee of the English National Screening Programme Advisory Group is currently working to tighten up some of the definitions within the current grading protocol and any updates will be circulated to Programme Managers and Clinical Leads of Screening Services in England. The Scottish Diabetic Retinopathy Grading Scheme protocol is available on the Scottish Collaborative website2 and on the Scottish Government website28 . 8.6 ROLE OF THE OPHTHALMOLOGIST IN SCREENING The role of the ophthalmologist in the delivery of screening and management of patients with diabetes is pivotal. The responsibilities of the ophthalmologist are: 69 - to form a team with one or more diabetologists to lead the delivery of the screening programme. A specific linked ophthalmologist is required for each individual programme. - to involve local management structures at PCT and SHA level - to act as higher level grader as appropriate to local methodology - to act as quality assurance reference standard after suitable training - to ensure the training and accreditation of local screening staff - to agree and monitor local quality assurance - to ensure access to prompt treatment within agreed quality standards - to organise the collection and prompt transfer of data on vision and disease outcome within the minimum data set to central data collection networks. This will be best achieved through the establishment of dedicated clinics for the management and follow-up of cases detected through screening. In September 2010 the Royal College of Ophthalmologists produced Preferred Practice Guidance29 on Diabetic Retinopathy Screening (DRS) and the Ophthalmology Clinic set up in England, which produces useful extra information for Ophthalmologists working in England. SECTION 9: RETINAL LASERS Photocoagulation for diabetic retinopathy is performed with the use of a variety of ophthalmic lasers. The technological advances in this field have made efficient laser equipment that can deliver effective treatments in both clinical set up as well in operating theatre. 9.1 METHOD OF LASER APPLICATION Laser energy may be applied to the retina either through the dilated pupil using a contact lens or the indirect ophthalmoscope, or externally through the sclera. Transpupillary laser is normally applied using the slit lamp bio-microscope and a contact lens. The superiority of the modern wide-angled contact lenses has made use of 3 mirror contact lens very infrequent in clinical practice. Contact lenses such as the VOLK® , MAINSTER® or RODENSTOCK® lenses give a good view of the macula, the equatorial and pre- and post- equatorial regions of the retina. These lenses give an inverted image but provide easy access to the retina even in the presence of media opacity such as mild to moderate cataract. Lasers can also be applied using a non-contact indirect method such as the 90 dioptre or 66 dioptre or superfield lenses again using a biomicroscopy technique with the slitlamp biomicroscope. These lenses may also be used with special adaptation of an indirect ophthalmoscope, however a 20D lens is usually used for laser treatment (PRP) with indirect ophthalmoscope; this technique offers the advantage of good access to peripheral retina and is the method of choice when applying laser during a general anaesthetic. It is very important to remember that the spot size may vary with the different types of lenses that are used and the operator should be familiar with the lens he or she normally uses. A sample of different spot sizes achieved with different lenses is shown in Appendix 1, Section 10. Trans-scleral laser therapy may also be used and a special attachment for the DIODE laser is available for this application. The laser intensity is monitored through an indirect ophthalmoscope and lens. 9.2 LASERS Optical radiations produced by gas or solid lasers are unique in that they are emitted at effectively one wavelength. Dye lasers are produced with inorganic dyes and have varying wavelengths. Gas lasers (ARGON and KRYPTON) produce optical radiations in the visible spectrum while the newer Diode lasers produce energy in the infrared band. The infrared lasers can be either continuous or multipulsed (Micropulse). Lasers act by inducing thermal damage after absorption of energy by tissue pigments. The three main retinal pigments are luteal pigment, haemoglobin and melanin and the appropriate laser wavelength can be used to be selectively absorbed in one or more of these three pigments. The main target cell, however, is the pigment epithelium and it is this site where much of the tissue damage is induced. 73 9.2.1 The Argon Laser The Argon laser has been in wide use for treatment of diabetic retinopathy. The Argon laser produces two major peaks of energy in the 488nm and 514nm wavelengths. The 488nm wavelength has been shown by reflection off the contact lens to cause operator blue colour vision damage and this wavelength is now filtered out of the system(1-4). The 514nm wavelength has a potential for causing similar damage but this has as yet not been proven; to prevent reflection of this wave band there is a barrier filter and the aiming beam is replaced with a HeNe (helium neon) laser which is coaxial with the treating laser beam. This green laser energy is absorbed both by haemoglobin and by pigment epithelium. It is therefore possible with this wavelength to directly close microaneurysms or close new blood vessels and if applied over a retinal