Contrary to popular belief, optometrists don’t dilate patient’s pupils because we enjoy listening to our patients complain. We dilate the pupils in order to obtain the best possible view of the retina, optic nerve and blood vessels inside the eye. It also allows a better assessment of the lens for signs of cataracts.
Think of examining the eye like a trying to look through a hole in the front of a ping pong ball to see a design painted on the inside. Making the hole bigger makes it a lot easier to look inside and see farther out. That’s especially true when the ping pong ball is wiggling around! Unfortunately, when you shine a light in the eye, the pupils get smaller, making it even harder to get a good view to assess the health of the eye. If you were trying to see details of the back of the eye, which eye in the photo above would you prefer to examine?
Signs of both ocular and systemic diseases can be seen in the back of the eye. For example, glaucoma causes changes in the appearance of the optic nerve. Yellow deposits called drusen or dark specs of pigment accumulate in the macula in macular degeneration. Small holes or tears in the retina can lead to a retinal detachment. Diabetes and hypertension can cause hemorrhages in the retina and/or changes in the appearance of the retinal vessels. Primary cancers such as choroidal melanomas and retinoblastomas can be seen there as well as metastases from the breast, lung and other organs. And the list goes on and on.
How often you need to be dilated and the type of drops used depend on several factors. Age, pupil size and reactivity, iris color, medical conditions, risk factors, signs and symptoms, the level of patient co-operation and previous response to dilation should all be taken into consideration. With the equipment and lenses available today, we may be able to get an adequate view without dilation or use milder drops that wear off quicker and won’t affect your focusing as much. However, dilation always maximizes our view. Even patients with unusually large pupils may require dilation in some situations.
Many offices are now marketing the Optos optomap laser scanning image as a premium option, often as a high tech “alternative” to dilation. An image made with laser light has a sexy wow factor for patients but, in my opinion, the optomap is not an adequate substitute for dilation. It certainly should not be done in lieu of physical examination of the retina by the doctor.
Optos claims that it has a field of view of “up to 200 degrees” and “conventional devices” are only 30 degrees. A good quality, 200 degree image requires a skilled technician and a cooperative patient with decent sized pupils (even laser energy has to go through the pupil to make an image) and no corneal or lens problems. And that 200 degrees only covers the horizontal direction. Unfortunately, pathology doesn’t just occur in the horizontal meridian. I have an optometrist friend that has significant scarring in the inferior retina from surgery for a retinal detachment that did not show up in an optomap of her retina.
I’m also not sure what “conventional device” they are talking about. Even the basic instruments I used in optometry school 30 years ago gave up to a 60 degree (full circle) single view in a fully dilated patient. The edge of the retina could be seen by having the patient look in different directions. Current technology gives even wider views with smaller pupils. It also provides greater magnification than the optomap and a stereo view, both of which are critical in identifying subtle changes in the retina or optic nerve.
I’m not against taking images of the eye. They allow us to document the eye for future comparison and they are a great tool for patient education. One of the biggest benefits of retinal imaging is that it allows a faster, more thorough examination of the eye with better comfort for the patient. The macula and optic nerve are in the posterior pole of the eye where patients are most sensitive to light. In some patients it’s tough to get more than a quick peek of this critical area between blinks and their watering eyes cause a lot of reflections that block the view. With retinal photography, we can quickly capture an image that can be viewed on the monitor for as long as desired. We can zoom in on any areas of interest for better detail and a variety of filters can be applied to the image to highlight specific details. No examination with lenses can provide the same field of view and magnification in one view.
However, I would argue that an optomap is inferior to a digital retinal photo in most cases. While the Optos can get farther in the periphery under optimal conditions, the bulk of pathology is found in the posterior pole where the macula and optic nerve are located. Also, most problems in the periphery either need to be treated or they don’t. So while you want to be able to see pathology in the periphery, a photograph isn’t as helpful in management and treatment. The optomap image is very distorted and much lower resolution compared to a digital retinal photo. Retinal photos can also be taken in offset pairs to provide a 3D view of the posterior pole and multiple images can be combined with software to expand the field of view included in a photo.
If your goal in paying extra for an optomap is to get a neat, high tech laser scanning image of your retina, then the optomap may be for you. But don’t think that it will provide the same quality of view that is achieved by dilation and examination by the doctor using modern equipment and lenses and, I dare say, even examination without dilation in many instances.
If your goal is a high quality, cost-effective health assessment of your eyes, have them dilated as needed for an overall stereo view of the eye. Have high resolution retinal photos of the posterior pole if you want the detail, analysis, documentation and wow factor that they provide.
Dilation is not always necessary at every exam but, regardless of the equipment used, it usually allows for a better health assessment of your eyes. Isn’t that why you’re having your eyes examined in the first place?
Check out these examples of optomap images I received from the previous doctors of some of my patients compared to the retinal photos I took and decide for yourself.
- Optomap image of patient #1. That yellow/white disc with blood vessels coming out of it is the optic nerve. The darker patch just left of that is the macula. They are in the posterior pole of the eye. You can see that there is a wide view of the temporal retina (to the left) but very little view of the superior, nasal and inferior retina. Even with the wider temporal view, you can barely see the retinal defect peeking through the eyelashes at 8:00.
- Retinal photo of the peripheral defect in patient #1. This is a retinal photo of the same defect seen between the lashes at 8:00 in the optomap image above. Peripheral images are harder to capture in a retinal camera but have better detail when you can get them. The hazy white zone is from reflection of the flash off the iris when the patient is looking off center.