March 15, 2000
Norma Devine, Editor
On Wednesday, March 15, 2000, Dr. Rick Wilson, a glaucoma specialist at Wills, and the glaucoma chat group discussed “Congenital Glaucoma.” Dr. Rick (“Eyeguy”) Cohn, a glaucoma specialist in Orlando, Florida, paid us a surprise visit. Here are some of the highlights.
Dr. Wilson: Welcome new chatters.
Moderator: The topic tonight is congenital glaucoma. Does anyone have congenital glaucoma or a child with it?
P: My son is two years old and has had congenital glaucoma since he was five months old. I would like to know the longevity of an Ahmed Valve and what happens.
Dr. Wilson: There is often a decrease in effectiveness with time. The reservoir for the Ahmed is medium sized and often requires medication, in addition to the flow through the shunt, even shortly after its insertion.
P: My son’s pressures are 19 and 11 with Timoptic and Azopt daily. I am curious, is there a typical length of time, say 3-5 years before it fails? Then what would be my options?
Dr. Wilson: Does you son have shunts in both eyes or just one?
P: My son has Ahmed Valves in both eyes.
Dr. Wilson: The options are to add another plate and tube to one side or to revise the plate that is there by removing the scar tissue surrounding it.
P: What is an Ahmed valve, and what is it used for?
Dr. Wilson: Valves are tiny tubes that drain fluid from the anterior chamber of the eye usually to a plate sewn onto the equator of the eye. The fluid flows to the plate, which keeps the scar tissue from growing together. A pocket of fluid is formed, which drains slowly through the scar tissue surrounding the plate.
P: How do you know if a baby has glaucoma? Are babies given a test at birth?
Dr. Wilson: A baby’s eyes are quite elastic. If the pressure is raised in the eye, the eye stretches and small breaks appear in the cornea, which causes tearing, light sensitivity and a big, cloudy cornea. These are the signs that bring the baby to the ophthalmologist.
P: Do you recommend intraocular lenses for children with Ahmed valves? My son is aphakic now and had a cataract due to his 10 surgeries and meds.
Dr. Wilson: I do recommend lenses for children if there is enough support in the eye for the lens without sewing the lens in.
P: How do you put the lens in without sewing it in? My doctor says he would not recommend this, due to the valve placement.
Dr. Wilson: Normally, when the natural lens is taken out, we save the clear sack that was around the cataract and use it to support the artificial lens.
P: How has your son been with having to through all of this?
P: He is amazing. He now wears glasses and is patched six hours a day. He gets around beautifully and if you didn’t know his history you would not know there is anything wrong with his eyes, except that the right one appears a bit larger. He is pretty well adjusted to the drop regimen and office visits. Children are resilient.
Moderator: “Eyeguy” has entered the room. The topic tonight is congenital glaucoma.
Dr. Wilson: Hi, Eyeguy. Good to have you back.
Eyeguy: I’m an Orlando, Florida, glaucoma specialist, Rick Cohn, M.D.
P: Dr. Wilson, would that procedure need to be done at the time of removal or can it be done later?
Dr. Wilson: It could be done later, but more deterioration could be caused to the cornea than if it were done at the same time.
P: Rick what is the highest pressure you have ever taken?
Dr. Wilson: It’s hard to measure over 80, but I’ve had quite a few pegged up against the 80.
P: Dr. Rick, what does the doc look at to read IOP? Is it something like a thermometer?
Dr. Wilson: It is a tonometer, which touches the eye and flattens a 3 mm diameter area of your cornea. The force needed to flatten that area is directly related to the intraocular pressure.
P: Can the tonometer cause iatrogenic damage?
Eyeguy: The Imbert-Fick principle
Dr. Wilson: It can transmit infection rarely, or scrape the cornea.
P: Dr. Rick, what is the doc looking at when he says the number? I mean is it a gauge where the mercury rises to a certain point?
Dr. Wilson: He or she is looking at a gauge.
P: Thanks, Dr. Rick. After hundreds of readings, I was never quite sure.
P: Would the scraping of the cornea with the tonometer, over time, contribute to, say, cataracts or blurred vision or some degeneration?
Dr. Wilson: No. It is very rare for any problems with tonometry to be seen.
P: Dr. Wilson, I have read that in giving drops you should wait 10 minutes between them. My doctor and the Glaucoma Research Foundation have said that in giving drops to children, wait five minutes in between meds. Are children and adults different in any way when it comes to giving meds? Also, how long should you use an opened bottle of medicine?
Dr. Wilson: I advise waiting 10 minutes between drops at any age. Most people hurry that interval, so it is far safer to try for ten and cheat than try for 5 and cheat. I rarely advise using a bottle over 4 to 6 weeks.
P: Rick, how often does the tonometer scrape the cornea?
Eyeguy: Almost never.
Eyeguy: Rick, do you favor goniotomies or setons in congenital glaucoma?
Dr. Wilson: Eyeguy, 360 degree goniotomy, then filamentary trabeculotomy, then trab with mitomycin, then shunt.
P: Doctors, what’s a goniotomy?
Dr. Wilson: A goniotomy is an incision into an abnormal membrane blocking access of aqueous fluid to the drain in the eye. This opens up the drain to aqueous for drainage.
P: So you perform all those things at one time on a child?
Eyeguy: One at a time.
Dr. Wilson: No. Start with the first and safest. Escalate if the first surgery fails, or the cornea is too cloudy to see to do it. Then I also move onto the next procedure.
P: Rick, when is goniotomy indicated?
Dr. Wilson: If the IOP is above normal in a patient less than 1 1/2 years of age.
P: Doctor, I have trouble driving at night. Is it due to loss of contrast sensitivity?
Dr. Wilson: Contrast sensitivity is one of the first abilities to go with vision. That’s why you have trouble at night. There is decreased contrast when it’s dark.
P: What is a normal pressure for a 6 to 8 year old?
Dr. Wilson: The usual pressure for that age group is 10 to 14 mmHg.
P: Is there another type of test in place of visual field test with more accurate results?
Dr. Wilson: My favorite is the SITA Standard Humphrey.
P: What is a blue/yellow field test?
Dr. Wilson: Short Wavelength Perimetry or Blue on Yellow is supposed to pick up glaucoma about two years before conventional white on white does. However, there is a lot of “noise” in the testing, and it is difficult to interpret.
P: What do you mean by “noise”?
P: Probably artifact.
Dr. Wilson: Noise is static that confuses the message of the visual field test.
Dr. Wilson: I’m flying to Dallas tomorrow, so will call it a night. I’m glad to see Eyeguy again. We had Paul Palmberg the other night as a guest. Everyone have a good week.
End of highlights for March 15th chat.