Screening for age-related macular degeneration using nonstereo digital fundus photographs.

Age-related macular degeneration (AMD) is a disease with significant visual morbidity and accounts for the majority of blind registrations in the developed world including the UK. Certain forms of neovascular AMD are amenable to treatment but require expeditious referral to a retinal specialist. AIM: To evaluate the possibility of using nonstereo fundus photographs as a low-cost screening tool for neovascular AMD. DESIGN: Retrospective review of patients referred to the macular clinic of a teaching hospital in London. METHODS: A total of 198 randomised digital fundus photographs, without any other clinical information, were presented to two independent ophthalmic interns who graded them into one of the three categories: normal, age-related maculopathy (ARM), or neovascular age-related macular degeneration (AMD) to determine the urgency of referral to clinic. The results were compared with the known diagnosis for each patient and sensitivities and specificities for each diagnostic category calculated. RESULTS: The intraobserver Kappa statistic was 0.75 and 0.91 for grader 1 and 2, respectively. The interobserver Kappa was 0.54. The mean sensitivity and specificity for the identification of ARM was 60.5 and 76.3%, respectively The mean sensitivity and specificity for the identification of AMD was 85.7 and 78.8%, respectively. CONCLUSION: Nonstereo digital fundus photograph is a reasonable screening tool for CNV and may aid in decreasing the visual morbidity it causes by enabling timely referrals and treatment

A mechanical eyeball phantom for uveal melanoma radiosurgery by cyberknife

A treatment option for uveal melanoma has been investigated using the Cyberknife system, due to its advantage of real-time image guidance during therapy. However, unpredictable eyeball movement imposes challenges to the state-of-art technology. As a solution, we derived a 2D/3D transformation algorithm that is based on the pupil’s 2D coordinates captured by an optical tracking system to predict the tumor’s 3D positions in real-time. In order to validate our developed algorithm and other methods, a mechanical phantom that can simulate the eyeball’s movement is highly desirable.We designed a mechanical phantom that consists of a camera module, an eyeball module with an embedded “tumor", an eyeball holder module, and an eyeball moving module. All materials are made with acrylic or nylon plastics with the exception of the linear motion stages and the camera.In the calibration procedure, the phantom is scanned using a CT scanner. By using the recorded pupil’s coordinates and extracted tumor coordinates, the 2D/3D transformation model yields 0.39 ± 0.09 mm root-sum-squared error for five calibration positions between the actual 3D coordinates and the predicted coordinates. In the validation procedure, the eyeball is rotated to 11 different positions through the mechanical phantom. The 2D/3D transformation model yields 0.58 ± 0.27 mm root-sum-squared error for these positions between the Cyberknife-identified 3D coordinates and the predicted coordinates. The eyeball’s position can be controlled within millimeter accuracy.The designed mechanical phantom is suitable for validating image-guided radiosurgery methods. Further dynamic evaluations can confirm these methods for clinical applications