Fundus Reading Hood University of Wisconsin-Madison College of Engineering-Biomedical Engineering BME 200/300 December 7th, 2005 Project Members: Leah Brandon - Team Leader Adam Dahlen - Communications Nate Kleinhans - BWIG Sara Worzella - BSAC Client: Dennis Hafford Research Specialist Fundus Photograph Reading Center Madison, WI Advisor: John Webster Ph.D. Department of Biomedical Engineering University of Wisconsin – Madison Abstract: In the grading of retina scans at the Fundus Photograph Reading Center, normal office light interferes with the graders ability to efficiently identify lesions and other spots on the retina that are indicative of certain diseases. Since these lesions are often very small it is imperative to have a standard environment in which the scans can be graded. The design of a monitor hood that blocks ambient light is the key element in obtaining accurate grading of retina scans.1 §1. Problem Statement The goal of this project is to develop a monitor hood that will block ambient light for the photograph graders at the Fundus Photograph Reading Center. Determining problematic sites in retinal scans is used to diagnose disease states in the eyes. A controlled environment is necessary for grading of these scans in order to assure correct identification of problematic sites. Creating a monitor hood will provide this controlled environment. §2. Background The Fundus Reading Center is a facility located on the UW-Madison campus. The photograph reading center “strives to further the understanding and treatment of preventable blindness through interpretation of ophthalmic images in clinical studies” (eyephoto.ophth.wisc.edu). Photographs, like those in Figure 1, are received at the Reading Center and are graded for ophthalmic research. The focus of ophthalmic research at the Fundus Reading Center consists of five main categories: Diabetic Retinopathy, Age-related Macular Degeneration, Hypertensive Changes of the Retina, Studies of the Ocular Complications of AIDS (CMVR), and Age-related Eye Disease Study (AREDS). Since the retina can be assessed by noninvasive methods such as retinal photography, analyzing these photographs is preferred in relation to other invasive procedures. For example, retinal changes have been observed in many cases of hypertension and sclerosis. Figure 1. Fundus Photographs http://www.jhu.edu/wctb/coms/patient/photog/fundus.htm2 Figure 2. A stereoscope similar to those used at the Fundus Reading Center When a patient is photographed, special cameras take images of the eye with the patient’s pupil dilated. This procedure causes no discomfort to the patient and provides a photograph that details “the retina, the retinal vasculature, and the optic nerve head, optic disc from which the retinal vessels enter the eye” (www.jhu.edu). The purpose of grading photographs at the Fundus Center is for retinal quality. This quality is important the viewing of arteriolar abnormalities and lesions of diabetic retinopathy. To insure quality of the photographs, there are many grading protocols for the readers to assess these ophthalmic images. (eyephoto.ophth.wisc.edu) The stereoscope also plays a role in grading retinal images and must be accounted for in our design. Stereo images are pairs of photographs of the same subject. (stereo.thurstons.org) There are many techniques to view stereo images on the computer monitor such as parallel free vision and cross vision. (www.findarticles.com) However, the Fundus Reading Center uses a stereoscope to facilitate this process. The purpose of viewing through a stereoscope is to view a pair of images as a single 3-D image. The stereoscope (Figure 2) is used by the grader while viewing the photographs. A lever on the side adjusts mirrors to converge the images. A horizontally-centered position is necessary for proper viewing of the ophthalmic images. The image will become more distorted the further from the center the stereoscope is positioned. The viewer may have to adjust and rotate from this horizontal position to attain stereo. There are two components that must be taken into consideration when viewing the images: the horizontal and vertical positions, as in a Cartesian grid. Horizontally, if that3 Figure 3. Photodon Monitor Hood (http://www.photodon.com/mgrh.htm) landmark is at the origin for one image but at a different level vertically, turning your head can correct and re-align the images. Another problem occurs at the angle a person looks down at the screen; the eyes actually look down at a 30° angle. To correct this vertically, the monitor is positioned lower than the eyes and often tipped up slightly. (Hafford email) The viewing of these images requires precision and accuracy of viewing conditions. Ambient light poses a problem. Problematic reflections on computer screens occur in two categories. The first category is with too much light falling on the screen. This type of reflection reduces contrast and washes out the image. The second category of reflections occurs from bright areas in the environment surrounding the computer monitor. These reflections superimpose on the screen image and make it hard to see. (www.pc.ibm.com) §3. Literature Search A patent search reveals Patent 5,900,979, Patent 5,243,463, Patent D422,579, Patent 6,356,439, and Patent 6,394,615 which all describe monitor hoods for both laptops and desktop computers. Further information on these patents can be found in Table 1 in Appendix A. Related monitor hoods are available from companies such as ColorGear, CompUshade, Photodon, Ergomart, and Hoodman (Figure 3). These monitor hoods range from $25-$80. The goal of these devices is to reduce glare and background light. These products do not focus specifically on the reading of ophthalmic images or blocking all ambient light. An extended viewing window is also not part of their design.4 §4. Design Constraints The Fundus Reading Hood will be designed for LCD monitors and must block ambient so that the light intensity does not exceed 64 lux inside the hood. The design should be lightweight, sturdy, and self-supporting, with non-transparent fabric. The length must be adjustable and extend out 60.96 cm while keeping the monitor viewable at any length. While attached to the monitor, the design cannot extend significantly behind the monitor nor can it extend more than 38.10 cm in front of the monitor when not in use. The
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