We tell our partner photographers that it is not necessary to dilate a patient’s eyes in 85-90% of cases. But when is it a good idea to dilate, and what is the real value of dilation?
Several years ago we asked Dr. Harry Green of UC Berkeley Digital Health to join us in presenting the arguments for and against dilation to our Learning Community. That topic remains relevant, and we’d like to summarize the presentation here. After you’ve read the summary, you might want to visit that presentation from March 2012.
Ten to fifteen percent of retinal image sets are insufficient for interpretation when pupils are not dilated. Some pupils simply are too small or too reactive to get good images without dilation. The result is dark areas - small pupil artifacts, probably not avoidable by adjusting the flash. Each successive image tends to be darker than the ones before as the pupil struggles to recover from the flash of light. With dilation, that same eye can be imaged with adequate views of the optic nerve and macula.
Pupil size decreases naturally with age and with some types of drug abuse. Surgical trauma or other trauma can change the pupil’s size and even its orientation in the eye. And then some people have perfectly normal pupils that are just small. Diabetes, as well as age, can make pupils sluggish, so your target population (diabetes patients) are at risk for pupils that might need dilation. Further, diabetics who have had laser treatment for advanced retinopathy are even more likely to have small pupil size. After dilation, pupil size for these patients is far less dependent on light, which means your need to wait between photos is dramatically reduced. A patient with a cataract in the middle of the pupil can often be successfully imaged with dilation, allowing for access to the area around the cataract.
Dilation allows you to successfully capture more viable images from more patients. The quality of these images will be much better, allowing for more accurate grading. That makes the entire screening process more effective. Be sure to consult the EyePACS Photographer Handbook and read the dilation protocol before proceeding.
Does dilation make the patient visit take longer? Because it takes a while for the drops to take effect, one would think the screening would take longer overall. However, once the pupils are dilated, the eyes can be successfully imaged much more quickly. Consider the alternative. When you’re dealing with a patient with small or reactive pupils, you will have to allow about 60 seconds for the pupil to recover each time. After they relax with eyes closed, you must realign for the next photo. Considering the time for the intake form, 16 minutes to capture eight photos, and time to upload to the EyePACS site, screening an undilated patient with small or reactive pupils is likely to take you up to 26 minutes.
On the other hand, when you dilate the pupils, patients can fill out their intake forms while dilating, and you, the photographer, can use this time to attend to other responsibilities or get the next patient ready. With dilation, your alignment, focusing and photographing can proceed more quickly, and there’s no waiting between photos (because the pupils are now nonreactive). The patient does not move the head, so realignment is unnecessary. If you snap eight images in four minutes and upload them to the EyePACS site, you have probably invested a total of 25-30 minutes on this patient – just a fraction more than on the undilated patient.
Also, if these are diabetes patients coming in for a regular primary care visit, they could have their eye exam first and then, while still safely in the clinic (and perhaps wearing sunglasses), continue on to the lab or the diabetes educator or the PCP or nurse for the other important care they need.
Dilation has a downside also, of course. Patients find the discomfort of the drops, however, brief, disconcerting, and they might be restless as they wait for 15 minutes before beginning the imaging process. Afterward, they suffer from photophobia (light sensitivity) for a few hours and really should not drive for two hours. For these reasons we do not recommend routine dilation.
A very small percentage of patients can experience adverse reactions: dilation that lasts for many hours, even up to three days; hypersensitivity to the drops, causing redness and irritation; eye infection from a contaminated bottle. The most serious potential adverse reaction is angle closure glaucoma. Rare as it is, such an outcome can be prevented by using only the tropicamide solution instead of using both tropicamide and phenylephrine. Patients who have been dilated should always be advised what to watch for that might indicate an adverse reaction, as described in the full presentation.