Overview
Definition:
Retinopathy of prematurity (ROP) is a potentially blinding condition affecting premature infants, characterized by abnormal blood vessel development in the retina
It is a leading cause of preventable blindness in children.
Epidemiology:
Incidence varies globally but is higher in underdeveloped countries due to poor antenatal and neonatal care
In India, ROP affects a significant proportion of premature births, with an estimated 30-40% of infants born before 30 weeks gestation developing ROP
Risk factors include prematurity, low birth weight, prolonged oxygen therapy, sepsis, and respiratory distress syndrome.
Clinical Significance:
Timely screening and appropriate management of ROP are crucial to prevent vision loss and severe visual impairment
Understanding the specific timing recommendations based on gestational age and birth weight is fundamental for pediatricians and neonatologists to ensure all at-risk infants are evaluated promptly, aligning with national and international screening protocols.
Screening Guidelines
General Indications:
All infants born at < 30 weeks gestation or with birth weight < 1500 grams should undergo ROP screening
Infants with birth weight between 1500-2000 grams or gestational age 30-32 weeks should be screened if they have significant comorbidities such as an unstable clinical course, oxygen requirement, or suspected intra-uterine growth restriction.
Timing By Gestational Age:
For infants born < 30 weeks gestation: First screening at 31 weeks postmenstrual age (PMA)
For infants born 30-32 weeks gestation: First screening at 30 weeks PMA or 14 days of life, whichever is later
For infants born > 32 weeks gestation: Screening is generally not indicated unless significant risk factors are present.
Timing By Birth Weight:
For infants weighing < 1000 grams: First screening at 30 days of life
For infants weighing 1000-1500 grams: First screening at 30 days of life or 2 weeks after birth, whichever is earlier
For infants weighing > 1500 grams: Screening is typically based on gestational age and comorbidities rather than weight alone, but a baseline examination by 4-6 weeks of age is prudent if any risk factors exist.
Follow Up Schedule:
The frequency of follow-up examinations depends on the findings of the initial screening
If no ROP is detected, examinations may be spaced out
If ROP is present, especially Stage 1 or 2, examinations are usually done every 1-2 weeks
If ROP progresses to Stage 3 or is present in the "Plus disease" zone, treatment should be considered, and examinations may be more frequent.
Cessation Of Screening:
Screening can cease when the infant reaches 45-50 weeks PMA and there is complete retinal vascularization with no evidence of active ROP or regressed ROP
Even if ROP has regressed, the infant may still require follow-up until full vascularization is confirmed.
Diagnostic Approach
History Taking:
Detailed birth history including gestational age, birth weight, antenatal steroids, mode of delivery, and any complications during pregnancy or delivery
Neonatal history focusing on respiratory support (duration and concentration of oxygen), ventilation, sepsis, blood transfusions, and any medications used
Family history of eye conditions or blindness.
Physical Examination:
A complete neonatal physical examination is essential
For ROP screening, a dedicated ophthalmic examination is performed by a trained ophthalmologist using indirect ophthalmoscopy and scleral indentation under mydriasis
This allows visualization of the peripheral retina, which is crucial for detecting abnormal vascularization.
Ophthalmic Examination Details:
Examination involves assessing pupil dilation (using tropicamide and phenylephrine), then using an indirect ophthalmoscope with a 20-30 diopter lens
Scleral indentation is performed to view the far periphery of the retina
The examination is staged according to the International Classification of ROP, which describes the extent (zones), severity (stages), and presence of "plus disease" (dilated and tortuous retinal vessels).
Imaging Modalities:
While indirect ophthalmoscopy is the gold standard, wide-field imaging systems are increasingly used for documentation and screening
Optical coherence tomography (OCT) can be helpful in assessing retinal structure, particularly in cases of advanced ROP or when indirect ophthalmoscopy is difficult.
Differential Diagnosis:
Conditions that can mimic ROP include Coats disease, persistent fetal vasculature (PFV), familial exudative vitreoretinopathy (FEVR), and retinopathy of prematurity (ROP) in its various stages
Accurate diagnosis is based on the characteristic pattern of abnormal vascular growth and location seen on funduscopic examination.
Management
Indications For Treatment:
Treatment is indicated for threshold ROP, defined as Stage 3 ROP in Zone I or Zone II with 5 or more contiguous clock hours or 8 or more total clock hours of ROP, or any ROP with "plus disease"
Early treatment is also considered for pre-threshold ROP in Zone I or Zone II with specific high-risk features.
Laser Photocoagulation:
The primary treatment modality
Transconjunctival diode laser photocoagulation is applied to the avascular peripheral retina to ablate neovascularization and prevent its progression
This is typically performed using a laser indirect ophthalmoscope.
Anti-vascular Endothelial Growth Factor Therapy:
Intravitreal injections of anti-VEGF agents (e.g., Bevacizumab, Ranibizumab) are an effective alternative or adjunct to laser therapy, particularly in aggressive posterior ROP or when laser treatment is technically challenging
Careful monitoring is required due to potential systemic absorption and ocular side effects.
Vitrectomy:
Surgical intervention indicated for eyes with cicatricial ROP that has progressed to retinal detachment
This complex procedure aims to reattach the retina and preserve vision but has a high risk of complications and visual impairment.
Supportive Care:
Optimizing the infant's general health is paramount
This includes careful management of oxygen therapy, nutrition, temperature control, and prevention of infections
Reducing exposure to bright light may also be beneficial in some cases.
Complications
Retinal Detachment:
The most severe complication, leading to irreversible vision loss
Occurs when fibrovascular tissue contracts and pulls the retina away from the underlying choroid.
Refractive Errors:
Myopia is common, often severe
Astigmatism and hyperopia can also occur.
Strabismus:
Misalignment of the eyes, common in infants with ROP, particularly if retinal detachment has occurred.
Amblyopia:
Reduced vision in one eye that does not develop properly during the critical period of visual development
Often associated with strabismus or refractive errors.
Glaucoma:
Secondary glaucoma can develop due to inflammation and neovascularization in the anterior segment of the eye.
Cataract:
Less common, but can occur secondary to inflammation or surgical procedures.
Long Term Visual Impairment:
Even with successful treatment, many infants experience long-term visual impairment, ranging from reduced visual acuity to legal blindness, requiring ongoing ophthalmic and low-vision support.
Key Points
Exam Focus:
The most critical aspect for DNB/NEET SS is knowing the exact gestational age and birth weight cutoffs for screening and the corresponding timings for the initial examination and subsequent follow-ups
Understand the indications for treatment and the different treatment modalities (laser, anti-VEGF, vitrectomy)
Remember the stages and zones of ROP and the definition of "Plus disease".
Clinical Pearls:
Always check the baby's PMA (postmenstrual age) and birth weight
If unsure about the PMA, calculate it from the Last Menstrual Period (LMP) or crown-rump length (CRL)
Coordinate closely with the ophthalmology team
Educate parents about the importance of ROP screening and the potential for vision loss.
Common Mistakes:
Missing screening examinations due to inadequate follow-up systems or misinterpreting guidelines
Delaying treatment for threshold ROP
Over-treating infants who do not meet criteria
Inadequate documentation of findings and treatment
Failing to recognize the importance of comorbidities in borderline cases.