By Eva Briggs, MD
I recently made a new friend who, despite powerful eyeglasses, has low vision caused by retinopathy of prematurity (ROP).
This disorder affects premature infants, especially those born very early. It can also affect infants born weighing less than three pounds. Poor early weight gain and genetic factors also influence the development and severity of ROP.
The retina is the layer at the back of the eye containing specialized cells called rods and comes. These cells detect and respond to incoming light and convert it to nerve signals that travel to the brain.
The retina contains blood vessels that start to develop before 16 weeks of gestation. In very premature infants, this process hasn’t been completed prior to birth.
After a baby is born, they are exposed to oxygen levels higher than were present in utero. This causes the developing retinal blood vessels to constrict. The retina then experiences decreased blood flow. This triggers the release of a substance called vascular endothelial growth factor (VEGF). VEGF prompts new blood vessel growth, called neovascularization.
Excess vessel growth impairs the retina’s ability to do its job correctly. Eventually excess blood and vessels may be reabsorbed leaving behind hard membranes that can pull on the retina causing it to detach.
Affected babies have no obvious symptoms on casual exam. Detecting ROP requires an exam by an ophthalmologist. This exam uses drops to dilate the pupils and special tools to visualize the retina. Current recommendations call for screening infants born before 31 weeks of gestation and infants weighing less than 1,250 grams (2.76 pounds).
ROP is classified in several ways.
The zone indicates which segment of the retina is involved. There are five stages, from least severe stage 1 to most severe stage 5. There is also “plus” disease, with vessels that are dilated and twisted along with other findings. Plus disease is an indicator of severe disease requiring treatment.
Early stages of ROP don’t lead to blindness and may resolve on their own. But monitoring is required as the disease can progress. Treatment of severe disease usually entails laser treatment to affected areas of the retina. Disease that progresses to retinal detachment may require surgery.
ROP can cause the following vision problems:
• Refractive errors — this is most common — nearsightedness or farsightedness requiring glasses.
• Strabismus — muscle imbalance that prevents the eyes from aligning, with eyes that may turn in or out.
• Amblyopia — significant difference in vision between the two eyes, which can cause the weaker eye to lose vision permanently.
• Retinal detachment — the back layer of the eye pulls away from the surrounding tissues which can cause blindness if not promptly treated.
• Glaucoma — increased pressure inside the eye, also capable of damaging vision.
ROP was first described in 1942. Some famous people with ROP include the musicians Stevie Wonder and Derek Paravicini and actor Tom Sullivan.
Eva Briggs is a retired medical doctor who practiced in Central New York for several decades. She lives in Marcellus.