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System allows smartphone camera to document external ocular pathology
The system, which includes an adhesive gel pad and accessory lenses, uses slit beam illumination with or without the slit lamp ocular.
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I have long believed that photography is an underutilized resource in our visually oriented specialty. If a relevant picture can be introduced without disruption of the clinical visit, it can greatly enhance the doctor-patient interaction as well as improve the medical record. Smartphone cameras have finally made it possible to achieve that goal.
Numerous adaptations of smartphones for slit lamp photography have been described. It has been demonstrated that the newest phone cameras can produce images comparable to dedicated photo slit lamp systems at a lower cost. However, the utilization of these phone-specific mounting devices has been hampered by the proliferation of phone models and their rapid obsolescence. In addition, because the systems function exclusively through the slit lamp ocular, they do not address the need to document lesions involving the full face, both eyes and lids, orbital lesions, ocular rotations and misalignment, pupil abnormalities and the ocular adnexa, which requires a larger field of view.
This article will introduce a far more comprehensive system that can employ any current model smartphone to document external ocular pathology with slit beam illumination with or without the slit lamp ocular. This system is the logical evolution of a predecessor system published in 2010 that employed a compact independent digital camera. The new system assumes some of the features and affordability of the original one but utilizes the ubiquitous smartphone cameras that have largely replaced the small digital cameras for instant photography.
Description of the hardware
Two of the principal obstacles to widespread use of smartphones for slit lamp photography are addressed: 1) the proliferation of phone models and their frequent revision and 2) the lack of a true macro mode in smartphone cameras.
To solve the first of these issues, I devised a unique phone mounting system that utilizes a reusable adhesive gel pad that will accommodate virtually any smartphone shell design and camera lens position, thereby eliminating the need for phone-specific hardware (Figure 1). The large high-quality polyurethane adhesive pad will support the naked phone body or a smartphone case that has a smooth, glossy front surface. The gel pad leaves no residue on the phone or case, and when the surface becomes soiled or dull, it can be washed with mild liquid hand soap and water and air dried to restore its adhesive properties.
The polycarbonate platform to which the gel pad is affixed is friction-fitted to the adjustable aluminum camera arm so that it can be positioned farther away for full-face or orbit imaging and closer for anterior segment detail. The phone camera support arm is attached to the slit lamp carriage via a plate-spindle bracket that is inserted into the central hole in the slit lamp support column (Figure 2). That arrangement provides a stable photo platform in relation to the patient and allows adjustment of the components for both magnification and slit beam integration.
Figure 1. The adhesive gel pad is mounted on the removable third arm that is attached to the slit lamp carriage. An accessory plus lens is positioned for the Apple iPhone 5 camera.
Images: Graether JM
Figure 2. The mounting hardware viewed from the rear to demonstrate the horizontal slots to accept the accessory trial lenses for focus.
Macro functionality is acquired by the placement of standard trial set lenses anterior to the smartphone camera lens (Figure 3). These lenses, mounted in the optical path, provide the specific range of focus needed for the camera-subject distance. Three slots are placed across the top of the platform in front of the gel pad to accommodate the plus lenses (Figure 2). That arrangement produces high-quality images while allowing for a much greater range in the field of view than that obtained through the slit lamp ocular. For most external photos, I leave a +5.5 D lens in place and occasionally add an additional lens for higher magnification.
The slit beam and ambient room light are supplemented by a headrest-mounted flexible single LED light and/or a rheostat-controlled indirect LED light as needed for the subject material.
Alternative hardware is provided that allows the adhesive gel pad to support the phone camera in front of one slit lamp ocular (Figure 3). This route is selected if red-reflex lighting or transillumination of the iris is required or very high magnification of anterior segment pathology is needed (Figures 4 and 5). The ring clamp is attached to the ocular or the rubber eye shield depending on the slit lamp model. The hardware is adjusted so that the surface of the gel pad is in the vertical plane just in front of the ocular (Figure 3). The phone is advanced so that the ocular is imaged in the center of the screen, and the distance of the mounted phone to the ocular is adjusted for the best image. Digital magnification will reduce the vignetting of the edges of the image. Focusing is accomplished with movement of the slit lamp joystick.
I have found that I take far more photos with the external hardware than through the ocular. When the picture is used for patient education, the ability to include familiar ophthalmic landmarks for orientation and then zoom in on the pathology is helpful to patient understanding.
Figure 3. An iPhone 5 mounted on the adhesive pad in front of the slit lamp ocular to record a red-reflex photo of the cloudy lens capsule.
Figure 4. Anterior segment detail recorded without the use of the slit lamp optical system yet lighted by the slit beam. (Neurotrophic cornea with neovascularization.)
Figure 5. Cornea guttata imaged through the slit lamp ocular with the iPhone 5 mounted in front of the ocular on the adhesive gel pad.
Discussion
This comprehensive external photo system for the smartphone is easily assembled for use with any suitable slit lamp. It accommodates all current model smartphones and presumably new models as they emerge. It enhances the capability of the smartphone by making its optical system suitable for a wide range of still and video photography by the simple addition of readily available trial set lenses. By adjusting the focusing range of the camera to the useful range of the slit lamp platform, the highly desirable features of smartphone cameras can be more fully utilized. These include the low light sensitivity, the high screen resolution and the ability to instantly change the image magnification on the screen, which aid in photo composition and in recording and demonstrating the ophthalmic pathology. Now images as large as the full face and as small as minute anterior segment detail can be documented with the same system, largely independent of the slit lamp optics. The pathology is imaged on the smartphone screen and immediately recorded exactly as viewed. Although the optical system of the slit lamp is still available when needed, the photography is not limited to that restricted field of view. Video recordings of ocular rotations, lid movement, pupil abnormalities and other dynamic phenomena are made possible within a stable photo environment. The still images or videos can be transferred by email or hardwire connection to a computer, consultant or electronic health record.
Because the cost of this system is relatively low, estimated at about $500, it can be quickly amortized. The equipment is deductible as a professional expense. Photos can be charged for if they contain information not recordable just by the description or if they document disease progression, especially in potentially vision-threatening conditions such as severe infections, inflammations, corneal ulcers or possibly malignant tumors. The rationale for the photo and its interpretation must be included in the record. The photo may also help justify the level of service for that visit, even if not directly charged. Perhaps, more importantly, the use of photography can increase the level of satisfaction with the professional service and its perceived value on the part of your patient.
Because of familiarity with the smartphone by most eye professionals and the relative simplicity of its operation, this system makes slit lamp photography more readily accessible for documentation and patient education at a modest cost. The patient and family appreciate the opportunity to see his or her pathology. It also gives the clinical staff an opportunity to participate in and learn from the encounter. It should be particularly useful where equipment is shared by multiple users, as is frequently found in teaching environments.