Retinopathy of Prematurity (ROP) is an eye condition affecting infants born prematurely, involving the abnormal growth of blood vessels in the retina. Without proper development, these vessels can cause significant vision problems.
Understanding Retinopathy of Prematurity
Normal retinal vessel growth completes around the time of full-term birth. When infants are born too early, this development is interrupted, making them susceptible to abnormal vessel proliferation. The primary risk factors include prematurity, particularly birth before 31 weeks of gestation, and a low birth weight, less than 1,500 grams. Contributing factors can involve oxygen therapy, respiratory distress, and various systemic health issues common in very premature infants.
The Stages of ROP Explained
ROP progresses through stages, each characterized by specific changes in the retina. “Stage 0” ROP describes an immature retina without signs of abnormal vessel development. Stage 1 ROP presents with a demarcation line, a thin, flat white line that separates the vascularized (with blood vessels) from the avascular (without blood vessels) retina. This line indicates the boundary where normal vessel growth has stopped.
Stage 2 ROP involves the demarcation line evolving into a ridge, which is a raised, wider structure. This ridge signifies a halt in normal vessel development and the beginning of abnormal growth. Stage 3 ROP involves extraretinal fibrovascular proliferation, where abnormal blood vessels and fibrous tissue grow from the ridge into the vitreous gel, the clear substance filling the eye. These abnormal vessels are fragile and can bleed, potentially causing scarring.
Stage 4 ROP is characterized by partial retinal detachment, where the retina begins to pull away from the underlying layers of the eye. This detachment can be either extrafoveal (outside central vision) or involve the macula (central vision). Stage 5 ROP represents total retinal detachment, where the entire retina has separated from the back of the eye. This complete detachment leads to severe vision impairment or blindness if not treated promptly.
Beyond the Stages: Additional Classification Factors
ROP classification incorporates factors that help determine the disease’s severity and guide treatment decisions. The “zone” indicates the location of ROP within the retina: Zone I is the innermost area near the optic nerve, Zone II extends peripherally from Zone I, and Zone III covers the most anterior, peripheral retina. Disease in Zone I or posterior Zone II is more concerning due to its proximity to the macula.
“Extent” refers to the amount of retina affected, measured in clock hours. “Plus disease” is a significant indicator, characterized by dilated (widened) and tortuous (winding) blood vessels in the posterior retina. The presence of plus disease signifies a more active and severe form of ROP. Aggressive posterior ROP (AP-ROP) is a rare, severe variant that progresses rapidly, involving Zone I or posterior Zone II, and quickly leads to retinal detachment without prompt intervention.
Treatment and Management Approaches
Treatment for ROP varies depending on the stage and classification factors, with the goal of preventing retinal detachment and preserving vision. Mild cases, such as Stage 1 and some Stage 2 ROP without plus disease, are managed through observation with regular eye examinations. Many of these cases resolve spontaneously as the retinal vessels continue to mature. If the disease progresses or if plus disease is present, intervention becomes necessary.
Laser photocoagulation is a common treatment for more advanced ROP, such as Stage 3 or severe Stage 2 with plus disease. This procedure uses a laser to ablate the avascular (non-vascularized) peripheral retina, which reduces the signals that drive abnormal vessel growth. Anti-VEGF eye injections, such as bevacizumab, are another option, targeting vascular endothelial growth factor, a protein that promotes abnormal blood vessel formation. These injections can temporarily halt ROP progression, allowing normal vessel growth to resume.
Surgical options are reserved for the most severe stages, particularly Stage 4 and Stage 5 ROP, where retinal detachment has occurred. Scleral buckling involves placing a silicone band around the outside of the eye to indent the sclera, pushing the retina closer to the choroid and reattaching it. Vitrectomy is a more complex procedure where the vitreous gel and any scar tissue pulling on the retina are removed, allowing the retina to reattach.
Prognosis and Long-Term Outlook
The long-term visual outcome for infants with ROP depends on the initial severity and the effectiveness of treatment. Infants with mild ROP, particularly those observed without intervention, experience full recovery with normal vision. However, even successfully treated cases of more advanced ROP may lead to long-term visual issues. These may include myopia (nearsightedness), strabismus (misaligned eyes), and amblyopia (lazy eye). In severe, untreated, or unresponsive cases, especially Stage 5 ROP, significant vision loss or blindness can occur.