Introduction
Background
Retinopathy of Prematurity (ROP) is a potentially blinding condition affecting premature infants. Published data from developed countries reported 5.5%–20% of childhood blindness were due to ROP.1–5 The American Academy of Ophthalmology estimated this number to be approximately 50 000.1 Development of ROP was attributed to a myriad of factors with low birth weight (BW) and low gestational age (GA) as the most significant risk factors for this condition. ROP leads to disorganised proliferation of the retinal blood vessels causing retinal haemorrhage, scarring and retinal detachment.2 3 Advancements in neonatal care have increased the survival rate of preterm or low BW infants through oxygen supplementation, antenatal steroids, resuscitation and proper nutrition of these infants.3 As more preterm infants survive due to improved management, so does the possibility of developing ROP and potential childhood blindness.
Most international ROP screening guidelines which were revisited stated that infants screened must meet one or more of the following criteria: (1) BW of 1500 g or less, or (2) GA of 30 weeks or less, or (3) infants who are older than 30 weeks or heavier than 1500 g with a complicated postnatal course, or identified by neonatologist as being at risk for developing ROP, especially in the presence of the following risk factors: necrotising enterocolitis, intraventricular haemorrhage, sepsis or bronchopulmonary dysplasia.6 7 While recent publications noted that prevalence and severity of the disease have been decreasing among developed countries,1 the opposite was observed in developing countries including the Philippines, wherein, presence of ROP was reported to occur in neonates with higher BW and later GAs.2 8 In 2017, a call for re-evaluation regarding the practice of retinopathy screening and management was initiated by Clare Gilbert, emphasising individualised management catering to the locality.9
In a local study done by Del Mundo and Chua (2019),6 the investigators found that the leading treatable cause of blindness among children was ROP (47.7%) and cataract (5.8%).7 Effectively screening and treating infants who may be at risk for developing ROP is of utmost importance to prevent blindness.
A local study by Corpus et al8 showed that in a cohort of 105 infants diagnosed with ROP, when only GA and BW in the Philippine Academy of Ophthalmology (PAO)-Philippine Pediatric Society (PPS) 2005 screening criteria were applied (without the third criterion), 16.2% or 17 infants with GA of 33–36 weeks and BW >1500 g would have been missed. Of the 17 missed infants, mean GA was 34 weeks with the oldest at 36 weeks, while mean BW was 1858 g, with the heaviest at 2515 g. Although majority (16 infants) had type 2 ROP and most (15 infants) had identifiable risk factors, there were no risk factors identified for two infants.
Realising that first world ROP screening guidelines may not necessarily apply to our local setting, the Philippine Academy of Ophthalmology PAO recommended new screening guidelines to cover older and bigger infants. The 2013 Philippine guidelines for screening and referral of ROP include any of the following: (1) infants with GA of <35 weeks, or (2) infants with a BW of <2000 g, or (3) infants with GA of ≥35 weeks or BW ≥2000 g which was assessed by the attending paediatrician to have an unstable clinical course or with identifiable risk factors.1
Published data estimate that there were 6.6%–28.3% of infants coming from developing nations who develop ROP but are not detected because they exceeded the international screening cut-off of <32 weeks GA or <1500 BW.8
The 2013 revised guidelines developed by the PAO together with its ROP Working Group (ROPWG), the Philippine Society of Paediatric Ophthalmology and Strabismus and the Vitreoretinal Society of the Philippines were envisioned to have a better detection rate than the old PAO-PPS 2005 guidelines, which was based on the 2003–2004 American Academy of Pediatrician Section of Pediatric Ophthalmology guidelines,10 that screened younger (less than 32 weeks) and smaller (less than 1500 g) preterm babies. The revision targeted ‘zero infants blind from ROP’. Both guidelines had a third often overlooked criterion that encompasses all with unstable course and/or neonatal risk factors regardless of the baby’s GA or BW.
Increasing the cut-off GA and BW increases the number of infants requiring ROP evaluations. ROP examinations require topical cycloplegic–mydriatic that may have systemic side effects. According to a study done by Kremer et al in 2019, systemic absorption of topical mydriatic agents was associated with clinically significant and life-threatening side effects among infants undergoing ROP screening. The authors noted significant changes in heart rate, blood pressure, increased prevalence of necrotising enterocolitis and apnea.11 A local study done by Mesina-Bayana and Arroyo (2005) stated that commercially available topical cycloplegic–mydriatic agents did not have any significant side effects among adult Filipino patients12; however, these preparations are of higher concentration than needed for ROP screening purposes and current packaging is for adult dosing not neonatal dosing.11 The actual conduct of the screening may in some instances cause unstable vital signs in a fragile neonate, with some authors highlighting reduction in heart rate due to the oculo-cardiac reflex in approximately 10% of infants following ROP screening.11 Unwarranted ROP examinations also burden the health system, not only its physicians, but also its government-subsidised insurance system—the Philippine Health Insurance Corporation. As such, this study aimed to find out if there was a significant difference between the detection rates for ROP of the two guidelines with differing cut-offs in terms of GA and BW. Being initially part of a multicentre study that would have prospectively evaluated the new 2013 guidelines, the institution adopted the 2013 Revised Philippine Guidelines for ROP screening soon after its publication. Five years hence, we now have the opportunity to compare the detection rates of the new guidelines vis-à-vis the 2005 PAO-PPS screening guidelines using the same patient cohort.
This study compared the detection rates of the 2013 Revised Philippine Guidelines and the 2005 PAO-PPS Screening Criteria in identifying infants who develop ROP. It also determined the incidence of ROP in the Philippine General Hospital (PGH) using both guidelines, and established the correlation between GA, BW and presence of risk factors with the development of ROP either on initial screening and/or subsequent follow-up. Lastly, the most common intervention or plan on screening and follow-up were also identified.
Operational definition of terms and acronyms
Retinopathy of prematuriy (ROP)
A condition in which there is abnormal growth of retinal blood vessels that may sometimes lead to blindness.
Plus disease
A degree of dilation and tortuosity of the posterior retinal blood vessels meeting or exceeding that of a standard photograph.13
Type 1 ROP
Defined as zone I, any stage ROP with plus disease; zone I, stage 3 ROP without plus disease; or zone II, stage 2 or 3 ROP with plus disease.13
Type 2 ROP
Defined as zone I, stage 1 or 2 ROP without plus disease or zone II, stage 3 ROP without plus disease.13
Aggressive posterior retinopathy of prematurity (APROP)
APROP, characterised by severe plus disease, flat neovascularisation in zone 1 or posterior zone 2, intraretinal shunting, haemorrhages and a rapid progression to retinal detachment.14
Gestational age (GA)
Age in weeks of the infant based on ultrasound (preferred) or the last menstrual period.
Birth weight (BW)
Weight in grams of the infant when born.
Corrected age
GA plus chronological age of the infant.
Anti-vascular endothelial growth factor (anti-VEGF)
Drug that is administered through the intravitreal route to decrease the concentration of VEGF, thus, minimising vasoproliferation.