preemie-l ROP
DDerleth@aol.com
Mon, 17 Jun 1996 12:43:11 -0400
This is a note I posted on the America Online premie bulletin board many
months ago, and have saved on a disk. I thought it might be helpful in view
of the recent discussion of ROP:
There have been many questions and comments about ROP (retinopathy of
prematurity, what was called RLF or retrolental fibroplasia years ago), so I
thought I'd put in my two cents.
ROP is a disease of the blood vessels that supply blood to the retina, which
is the part of the eye that turns light into electrical impulses that are
carried back to the brain via the optic nerve for processing. In a term
baby, the vessels start at the back of the eye on the inside surface of the
eyeball, (where the optic nerve comes into the eye), and go along the inside
surface of the eyeball until they end at the edge of the iris. The iris is
the part of the eye that is blue or brown or whatever. When babies are born
prematurely, those blood vessels have not yet grown all the way to the iris
and, for reasons not well understood, they grow abnormally after the baby is
born. Years ago, when premies as small as the tiny ones that get ROP today
did not survive, premies could get ROP and go blind from getting too much
oxygen. It is very clear that there is much more to the ROP of today than
too much oxygen. (If only it was that simple!) I understand that it was that
"old style" ROP that blinded Stevie Wonder, the musician.
The stages, numbered 1 to 5, describe what's going on in there, which can
only be seen by a fairly sophisticated form of the eye exam. Stage 1 means
there is a flat but visible line blocking the forward progress of the vessels
toward the iris. In stage 2, the line has become a ridge that grows off the
surface of the retina. In stage 3, the ridge has abnormal blood vessels
growing off the top of that ridge into the clear jelly that fills the
eyeball. These abnormal blood vessels can pull the retina off the inside
surface of the eyeball, a retinal detachment. Stage 4 is partial detachment,
stage 5 is total detachment. Once detachment starts, especially if the part
of the retina called the macula (the part of the retina that "sees" what we
are looking directly at) is involved, the problems are vastly greater, and
blindness is a real risk.
This disease gets going at 4-6 weeks of age, most commonly in the smallest
premies. The first eye exam is usually done at about 6 weeks of age. It
tends to hit its peak around the due date, and fade thereafter. If that peak
gets far enough into stage 3, (I'll skip the details here), and
reaches a point we call threshold, surgery has a good chance of stopping the
disease before detachment. The window of time between hitting threshold and
being too late can be short, which is why babies nearing threshold (or
"pre-threshold") get eye exams so often, typically every few days.
There are two forms of surgery, cryo (which kills tissue by freezing it) and
laser (which kills tissue by burning it), that basically do the same thing.
The idea is to knock out the retina in front of the normal blood vessel's
current progress, because that is where the chemicals that stimulate the
growth of the abnormal vessels originate. Cryo was thoroughly tested in a
large study in the 1980s, and is the "old" standard therapy. Laser is not as
well tested, but presumably works just as well, and has some advantages.
Laser is easier to use farther back in the eye, leaves less eyelid swelling,
and can be done in the NICU in some centers. Cryo has more experience behind
it, and is easier to use farther forward in the eye. Neither of these
surgeries involves any cutting.
Even when the ROP peaks at a mild stage, longer term problems can still
happen. The main worries are the need for glasses (nearsightedness, mostly)
and strabismus ("lazy eye"), both of which are relatively treatable. In the
grand scheme of things, these are fairly minor problems, but they are still a
headache. It is not known if ROP will cause any issues as these kids become
older adults. Blindness is pretty rare these days, but can still happen. I
think the worst thing about ROP is that, if it gets to a scary point, it does
so right about the time parents are getting ready to take their baby home,
when they've already been through so much and are finally starting to relax a
little bit.
That's a quick summary of a difficult topic. I hope it helps.
Doug