What Is Retinopathy of Prematurity?
Retinopathy of prematurity (otherwise called ROP) is a type of disease that involves the abnormal expansion of the neonatal retinal blood vessels. It is related to factors such as receiving oxygen therapy. Although in recent years people have become aware of the disease, some parents and even non-specialist doctors do not know enough about the disease. Due to this, many premature infants do not get examined for retinopathy and that can adversely affect their vision overall.
What Causes Retinopathy of Prematurity?
Some possible risk factors for Retinopathy of Prematurity include premature delivery, abnormally low birth weight, and oxygen therapy.
Premature Delivery and Low Birth Weight
The retina is immature and there is a demarcation line present that cannot be crossed by the grey blood vessels. This way, the blood vessels cannot grow at a normal pace.
- The risk of ROP accelerates the longer oxygen therapy goes on, the higher the amount of inhaled oxygen concentration gets, and the higher the arterial blood oxygen partial pressure gets. The risk of developing ROP in CPAP or other methods of mechanical ventilation is higher than in hood inhalation.
- The oxygen concentration comes to a halt after the oxygen is given, and following that procedure, the tissue is relatively hypoxic (inadequate oxygen in the tissues). That promotes the chances ROP in the infant. The fluctuation of the partial arterial pressure of oxygen plays a key role in the progression of ROP.
- Hypoxia, anemia, hyperbilirubinemia (an increase of bilirubin in the blood), acidosis, blood transfusion, PDA (patent ductus arteriosus), hypothermia, and the dilatation of the cerebral ventricles caused by numerous factors.
- The mother having suffered from anemia or multiple pregnancies.
- Beta-blockers entering the fetus via the placenta and increasing its choroidal vascular tone, thereby promoting the progression of ROP.
- Partial pressure of carbon dioxide in the arteries. Dangerously low amounts of carbon dioxide can result in retinal vasoconstriction then retinal ischemia and eventually, ROP.
- Racial factor: Caucasians have a preeminent risk of serious illness.
What are the Symptoms of ROP?
It is common at three to six weeks after the birth of premature infants and is clinically divided into an active period and a fibrous membrane formation period.
The Activity Period
1. Vascular Change Stage
This is observed in the early course of the disease. The arteries and veins go through a tortuous expansion. The diameter of the vein also sometimes grows three to four times larger than the normal diameter. Brush-like capillaries are observed at the ends of blood vessels in the perimeter of the retina.
2. The Retinopathy Stage
The vitreous body starts to appear cloudy, and the fundus starts to appear hazier. The increase of retinal neovascularization is most of the time located near the equator. However, it can also be seen in the anterior or posterior pole of the equator. The retina in the eye is clearly lifted with crawling blood vessels on the surface, often accompanied by retinal hemorrhages of various sizes.
3. Early Proliferation Stage
The previously mentioned limited retinal protuberances appear in the proliferated vascular cord, and the treatment is developed into the vitreous body. This causes a small detachment of the retinal periphery or posterior pole of the fundus.
4. Moderate Hyperplasia Stage
The detachment range is seen to expand to more than half of the retina.
5. The Extremely Proliferative Stage
Complete retinal detachment is observed, and sometimes a large quantity of blood in the glass cavity can be seen.
Not all cases go through the aforementioned five stages
The Fibrous Membrane Formation Period
When the active period does not disappear on its own, the fibrous membrane is finally scarred and deformed depending on the degree of severity from 1 to 5 degrees.
The retinal blood vessels appear narrow, and the periphery of the retina appears grey and turbid. It is often dotted with small irregular pigment dots. There is also turbidity observed in the nearby vitreous often accompanied by myopia.
Organic masses appear in the perimeters of the retina. The optic disc and retinal blood vessels are pulled by the organic masses to move to one side. A pigmented arc is observed on the edge of the opposing optic disc, and the optic disc fades.
The fibrous organic membrane stretches the retina, forming one or several folds. One fold is located on the temporal side while another is located on the nasal side. The ones found on the supratemporal inferior side are a rare occurrence. Retinal blood vessels are not distributed along this fold, making it different from congenital retinal folds.
The fibrous membrane, or a part of the retina, one that is separated from the organizing, is visible after the lens, and the pupil collar is blocked. The red-light reflection of the fundus can be observed because the ophthalmoscope has not been covered.
The entire lens is covered by a fibrous membrane or a detached retina. A jagged and elongated ciliary process can be seen in the periphery of the pupil. The anterior chamber appears very shallow, and there are often front and back adhesions iris adhesions. It can also cause corneal opacity due to secondary glaucoma or extensive anterior iris adhesion. The eyeballs are smaller than normal and inverted as well.
How Is Retinopathy of Prematurity Treated?
The main solution to ROP is early detection. An eye-screening system should also be set up for premature infants.
An anti-glaucoma surgery (damage prevention of the optic nerve) should also be considered in case the front and back adhesions of the iris have formed and are relatively extensive.
ROP does not necessarily progress from stage I to V continuously. Approximately, only 10% of cases suffer from total retinal detachment, therefore it is only important for observation to be carried out for the disease at stage I and stage II. If the disease progresses to the threshold stage, it must be treated right away.
Consequently, early detection and treatment of the threshold ROP is the most effective treatment of the disease. As of today, surgical treatment is sought out as the main solution.
1. Cold Treatment
The continuous cold treatment of the area around the retina for the threshold ROP can prevent half of the cases from progressing to detachment of the posterior retina, macular folds, posterior lens fibrosis, and other conditions seriously affecting the vision of the premature infant.
However, cold treatment does come with side effects.
2. Laser Photocoagulation Treatment
Photocoagulation treatment has evidently brought about favorable results with the initial stages of ROP. Compared to condensation treatment, this treatment has a better effect on ROP stage I and II. This type of operation procedure is more precise, and it is known to reduce vitreous hemorrhage, intraocular inflammation, and postoperative bulbar conjunctival edema. Photocoagulation is the first solution sought out for threshold ROP.
Another treatment called the Diode Laser Treatment is usually preferred in some countries.
3. Scleral Cerclage
In case the threshold ROP is not controlled and it progresses to stage IV or stage V, ROP can still be detected in the ocular fundus, and a scleral cerclage treatment can be considered a plausible option. Scleral cerclage relieves the retina, and traction can enhance the absorption of the subretinal fluid and promote the reattachment of the retina. This ultimately helps prevent the disease from progressing to stage V. Some prematurely born children can still heal on their own without needing surgery.
In this type of operation, if the retinal detachment is the wide funnel type, about 40% of it can be reset. The narrow funnel type, however, is far more complicated. Normally, in only 20% of the cases, the retina can be partially (or completely) anatomically reset following the vitrectomy treatment. The final recovery of visual function in children is extremely limited.
1. Oxygen Therapy for Pre-Threshold ROP
Given that oxygen therapy is known to stimulate the progression of ROP, oxygen is prohibited for premature babies for a fixed amount of time (carefully, because this can still increase the chances of mortality in premature babies).
2. Neovascularization Inhibitor
This method is yet to be patented as it is still in its development stages and is undergoing animal and human experimentation. The inhibitor may be available in the form of an emulsion, ointment, liquid medicine, or fomentation.
How can Retinopathy of Prematurity be Prevented?
Restricting the use of oxygen therapy in infancy is the only preventative measure that might prove effective. Oxygen can only be given at a concentration of 40% in severe, life-threatening cases like cyanosis.
The early application of vitamins in large doses may also demonstrate a certain preventative effect.
ROP is a serious disease, but it can be avoided via early detection and timely treatment. As already discussed, most cases are not seen to continue to the last stage, i.e., stage V.
In summary, the potential and apparent complications of retinopathy must be closely paid attention to, and preventative measures and treatment must be applied instantly.