Dr. Cheung’s Blog 5/1/2014

Dr. Cheung’s Blog 5/1/2014

May 1, 2014

The TSA of an Eye Exam

I just returned from a three-day trip to Hong Kong with my family.  The sole purpose of the trip was for my six-month old twins to meet my mother whose health has been declining.  Her mind is slipping away from Alzheimer’s and her body is ravaged by Parkinson’s and stomach cancer.  It was a bittersweet journey, as it was the first and probably the last time for them to meet.  My mom had several relatively lucid intervals per day, each lasting no more than fifteen minutes.  During one such interval, I asked my mom if my son Theo looked like me when I was a baby.  Without missing a beat, she nodded yes.  It was priceless, knowing that she understood my question and who the twins are.  The sixteen hour journey and four sleepless nights were all worth it.

On our way back from Hong Kong, I was pleasantly struck by how easy it was to go through the airport security there.  No undressing my belt and shoes in public.  The babies were wheeled through the metal detector in their car seats and stroller.  It was a breeze.  In contrast, going through TSA in Seattle was a bear.  They actually asked us to remove the twins out of their car seats along with every little toy dangling from the handle bar of their car seats.  The car seats were then scanned, as was the stroller.  Thankfully, they didn’t body scan the twins or asked us to taste the bottles of formula milk.

This difference in experience in airport security screening reminded me of a clinical encounter that I had several weeks ago in my office.  The patient was a middle age man who came in with some flashes and floaters.  He hesitated with the dilated fundus exam because he had to go back to work after his visit.  He asked why I could not just take a picture of his retina which was what his previous eye doctor did.  I explained to him the importance of a good retina exam through a dilated pupil and there is really no substitute for it.  Luckily, he relented and sure enough, he had an early retinal tear and was successfully treated with a laser and prevented the development of a full blown retinal detachment.

The dilated fundus exam is an integral part of any comprehensive eye examination.  It is the most effective way to screen for glaucoma and retinal conditions such as macular degeneration and diabetic retinopathy.  An annual dilated fundus exam is recommended for individuals 65 years and older.  Without dilation of the pupils by drops, the pupils can constrict to 2 mm or even smaller with light stimulation in some people.  It is impossible to accurately assess the retina through  such a small opening and many retinal conditions, particularly those that affect the peripheral retina such as retinal tear, will be missed.   A retinal camera can provide some clue to retinal pathologies in the central part of the retina but it is practically useless for the peripheral retina.  As a screening tool, not only is the retinal camera not sensitive enough, it is also not cost effective.  The patients often incur an additional cost because it may not be covered by their insurance.

When the pupils are dilated with drops to 5 mm or more,  an ophthalmologist can accurately assess the lens for any cataract formation.  The optic nerve can be visualized to look for signs of early glaucoma or swelling due to increased pressure in the brain.  The macula, the central part of the retina, where there is the highest density of photoreceptors, can also be carefully examined for early signs of macular degeneration or diabetic hemorrhages.  The blood vessels can be assessed for high blood pressure damages and we can also look for tumors and retinal thinning or defect in the periphery.

In children, a dilated fundus exam is also paramount for those at risk or suspected to have retinoblastoma.  Without a good exam of all parts of the retina, this cancer of the eye can extend through the optic nerve into the brain and is potentially lethal.  The pupils of premature babies are also frequently and safely dilated to detect for retinopathy of prematurity – abnormal blood vessels development in premature retina that can lead to retinal detachment and permanent blindness.

In adults, we typically use agents that will keep the pupils dilated for four hours.  Near vision will remain blurred during this time because both the pupil dilating muscle (the iris dilators) and the focusing muscle (the ciliary muscle) are affected by these agents.  In children, because of their tremendous focusing power, we often use stronger agents to temporarily paralyze the focusing muscle.  Doing so will give us the most accurate glasses prescription in children.  The trade of, however, is that the near vision may remain blurred for a day.

The side effects for dilating the pupilsare generally mild and tolerable.  Blurred near vision and light sensitivity are the most common complaints.  Allergic reactions to dilating agents may result in red eyes, rash or swelling of the eyelids but they are transient.  Small children can occasionally become sleepy after dilation.  Very rarely, dilation may precipitate an angle-closure glaucoma attack for those individuals with anatomic narrow angles.

The dilated fundus exam is akin to TSA screening.  It is time-consuming, inconvenient and the yield is generally low.  In low risk population without any symptoms, the rate of detection of clinically significant fundus lesions is estimated to be about 1 to 3 %.  I have yet to meet a patient that enjoys the dilated fundus exam.  I dreaded having my own pupils dilated six months ago and the previous one was done about six years ago. I also have yet to meet a traveler that sings TSA praises.  However, if I have to choose, I would pick a dilated fundus exam over a retinal camera and the TSA over the Hong Kong airport security over and over again.   The consequences of not doing a proper screening-another terrorist attack or blindness- are unimaginable.