EyeNet Magazine


 
Ophthalmic Pearls: Comprehensive
Make the Most of Digital Cameras
By Andrew P. Doan, MD, PhD, Michael V. Boland, MD, PhD, and Thomas A. Oetting, MD
Edited by Ingrid U. Scott, MD, MPH, and Sharon Fekrat, MD
 
 

As residents, we frequently present cases during morning rounds. However, many cases are seen “after hours,” when it is difficult to document problems because photography services are not available. Over the last three years, we developed an economical method for photographing ocular findings using a $300 digital camera.

Both ophthalmologists in training and those in practice can utilize this technique to provide high-quality external and anterior segment photography services for their patients without the expense of a slit-lamp mounted photography system costing more than $15,000. 

Using Digital Cameras to Take External Photographs
Since our budgets do not allow us to try out a variety of cameras, we have used the Canon PowerShot S230 and SD110 to take external photographs of the eye. However, the principles described below apply to other cameras as well.1

Focus. All digital cameras have an auto-focus system. The PowerShot’s AiAF system automatically attempts to select the best focus. For clinical photography, we have found that the AiAF should be turned off and the camera set to “center focus.” As the name implies, center focus forces the camera to focus only on the center object. This is important, for instance, when a lid lesion is of interest, as the AiAF system may focus on the eyelashes instead of the lesion.

Speed. The ISO setting should be set to auto until the physician is more experienced with different ISO speeds.2

Flash. This may or may not be needed, depending on ambient lighting. We recommend trying to capture images with both the flash and no-flash settings to see which provides a better image.

Macro mode. The most important setting is the macro function, which allows the camera to focus on close objects. Depending on the camera, object distance to the lens may vary from two to four inches in macro mode. Because it allows images to be taken from a short distance, the macro setting provides detailed images of the eye. Each digital camera has an indicator to note whether a subject is in focus. With the cameras we use, for instance, when the shutter button is pressed halfway down, a green box appears on the LCD viewfinder when the area of interest is in focus. 

Video. Most digital cameras also offer video capturing. We have used this feature to document abnormalities of ocular movement, including nystagmus.

Using Digital Cameras With the Slit Lamp
Using the settings outlined above with a slit lamp, we have used digital cameras to capture high-resolution images of the anterior segment.

Settings. For slit-lamp photography, the camera needs to be set to the following: 1) center focus, 2) auto ISO, 3) macro mode and 4) no flash. 

Focus. To take a photograph, focus on the desired anterior segment finding with the slit lamp using either the left or right biomicroscope ocular. Through the same eyepiece and using the LCD viewfinder on the camera, center and focus on the subject by moving the camera away or toward the eyepiece. Ideally, a spacer between the eyepiece and camera lens can be made, but using a finger works well, too.

Remember to depress the shutter halfway down until the green box appears indicating that the subject is in focus. If a yellow box appears, then reposition the camera slightly and depress the shutter halfway down again.

Light source. For certain ocular findings, such as keratic precipitates, iris transillumination defects or lens opacities, an external light source is not necessary. Because digital cameras lack the dynamic range of the eye, however, most anterior segment photographs require an external light source. We balance a Finhoff transilluminator on the arm of the slit lamp or have an assistant hold the transilluminator. Without an external light source, the camera will usually make a poor choice regarding exposure, and the result is an image that is either too dark or too bright. The external light source provides enough background illumination so that the camera can capture the scene correctly.

Video. As with external photography, video can be acquired through the slit lamp. We have demonstrated this by documenting a Seidel positive traumatic wound.

Conclusion
Inexpensive digital photography is altering the educational environment at our institution. It is proving to be a great method to document ophthalmic diseases and to obtain opinions from faculty at a later, more convenient time. In addition, we have used images to educate patients and family members about diseases by displaying them on computer monitors or on the camera’s LCD display. With an unrestricted grant for resident education arranged by Allergan, residents at the University of Iowa are photographing ophthalmic cases with their compact digital cameras and presenting them at departmental morning rounds and on the Web.3

There also is promise for this approach in clinical practice. Armed with a computer, optional photo printer and digital camera, ophthalmologists can offer high-resolution exterior and anterior segment photography services for their patients at an affordable price.

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1 Models from Minolta, Nikon and Pentax work well as long as there is a macro mode.
2 ISO stands for International Standards Organization.
3 www.eyerounds.org

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Drs. Doan and Boland are senior ophthalmology residents and Dr. Oetting is associate professor of ophthalmology; all are at the University of Iowa. They have no financial interests in any of the products mentioned in this article.
 


Digital Photography Basics

With rapid expansion in technology, ophthalmologists now have numerous choices of digital cameras at affordable prices. As first-year ophthalmology residents, we started using the Canon PowerShot S230 Digital Elph, which is a 3.2 megapixel (MP) camera that stores images on a Compact Flash memory card. The Canon S230 has been replaced with an equivalent model, the Canon PowerShot SD110, which maintains the 3.2 MP resolution but uses a Secure Digital memory card.

Size. Both cameras are less than 3.5 inches long and weigh less than 6 ounces, and they fit nicely into a pocket or in a cell-phone case attached to the belt. After we demonstrated the utility of these cameras to the department, they are now provided as standard equipment for all residents.

Resolution. The high resolution and portability of these cameras make them ideal for use in a diverse clinical setting where one would like to obtain external and slit-lamp photographs. We have found that a 3 MP resolution exceeds our needs for documenting clinical findings, making digital copies of imaging studies and presenting cases. However, for those who demand higher resolutions, Canon also offers the PowerShot S410 and S500, which provide 4 and 5 MP resolution, respectively, for less than $400. 

Archiving. Storing and organizing digital images after acquisition is one of the problems with this approach. We currently store images on a secured personal computer. A simple system is to store images by patient (be careful of HIPAA constraints) or by disease process. A more sophisticated system would allow both.

As practices move to electronic medical records, however, this problem will disappear. At the Academy Joint Meeting in 2004, for example, a wide variety of companies offered systems that allow the uploading of digital files to individual electronic charts. As residents, we have organized images from “classic” and unusual cases into folders such that they can be found later. Using this approach, some of the University of Iowa residents will have a library of more than 4,000 images after finishing their training.



____________________________________________________________________________________________

1 Models from Minolta, Nikon and Pentax work well as long as there is a macro mode.
2 ISO stands for International Standards Organization.
3 www.eyerounds.org.

____________________________________________________________________________________________

Drs. Doan and Boland are senior ophthalmology residents and Dr. Oetting is associate professor of ophthalmology; all are at the University of Iowa. They have no financial interests in any of the products mentioned in this article.
 



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