Introduction

Retinopathy of prematurity (ROP) is a proliferative disorder of the retinal vasculature occurring in preterm babies. It is an important cause of avoidable childhood blindness. The incidence of ROP in developing countries such as India is increasing due to improving neonatal services leading to improved survival of premature infants. The incidence of ROP in India varies from 24% to 47%, while aggressive ROP occurs in 4 to 5% of the screened infants.¹

The clinical features, screening guidelines and management options are very clearly defined and therefore it is an ideal disease to screen and manage. The screening criteria followed in our country is given by Rashtriya Swasthya Bal Karyakram, Government of India.² The diagnosis of ROP is based on the clinical features as described by the International Classification of ROP (ICROP) system in terms of the zone and stage of ROP, and presence of plus disease.³ Type 1 ROP is treatable ROP which broadly includes AROP or stage 2-3 with plus disease in zone 1 or zone 2. AROP is defined by presence of junction in zone 1 or posterior zone 2, absence of stage, presence of avascular loops at the junction, flat neovascularization and prominent plus disease which if not treated can rapidly progress to stage 4 ROP.¹

The treatment options for AROP include laser photocoagulation, intravitreal anti-VEGF injection, vitrectomy, and a multipronged combination of these individual options. AROP has traditionally been treated with laser photocoagulation of the avascular retina. Severe constriction of the visual field and induction of myopic refractive error are the common occurrences while late angle-closure glaucoma and cataract development are rare adverse effects of laser treatment in AROP. The progression of APROP can occur despite laser treatment leading to unfavorable outcomes such as peripheral TRD (stage 4a) and rarely stage 4b/stage 5/falciform fold formation.¹

Intravitreal anti-vascular endothelial growth factor injections have become the mainstay of treatment in the current era because of the benefits of continued revascularization of retina, better visual field and lesser refractive error following treatment.^4–6 However, the failure of regression leading to persistent avascular retina (PAR) and disease reactivation are two significant limitations of anti-VEGF monotherapy, and these require retreatment. The retreatment rates vary from 7.8% to 75%.¹ Only Ranibizumab has been FDA approved for treatment of type 1 ROP and the reactivations are very common with ranibizumab monotherapy.

The combination treatment can be a suitable midway option. The anti-VEGF agent provides immediate resolution of the TVL and ‘plus’ disease (as early as day one after injection), while laser treatment helps in complete regression of the new vessels and takes care of the avascular anterior retina permanently.^{1,7–11} However, the field restriction and myopic refractive error risk will exist if laser is done to the entire avascular retina. In zone 1 AROP, this would again require laser of a lot of retina and lead to high refractive error. A balance could be zone 2 posterior sparing laser i.e. laser in zone 3 and zone 2 anterior area and sparing zone 1 and zone 2 posterior area.

Therefore, in this study, we will evaluate the effect of additional zone 2 posterior sparing laser following intravitreal anti-VEGF injection in the management of zone I AROP.

There is only one study by Gangwe et al¹¹ where they considered zone 1 sparing laser in early laser group (group 1) and mandatory complete laser at 6 weeks in the deferred laser group (group 2) in patients with zone 1 AROP and found recurrence- 2 eyes (6.7%) in group1 vs 14 eyes (45.1%) in group 2; 27 eyes in group 1 & 29 eyes in group 2 had favourable structural outcomes (P = 0.61) at 6 weeks after laser; lesser laser spots were required in Group 2 compared to group 1; refractive error was 1D in Group1 vs 0.5D in Group2 at 6 months (P = 0.002). The role of zone 2 sparing laser has not been evaluated and compared with observation in literature.

Rationale of Study

The rationale of combined therapy in AROP is to provide the synergistic effect of anti-VEGF treatment and laser photocoagulation. Anti-VEGF agents act by blocking the existing VEGF and laser act by suppressing further production of VEGF. Combination of anti-VEGF injection and laser therapy for zone 1 AROP would reduce the rate of reactivation and would overcome the disadvantages of anti-VEGF monotherapy but still have issues related to visual field loss and refractive error due to laser ablation. For zone 1 AROP, combination of anti-VEGF injection with zone 2 posterior sparing laser would retain the benefits such as early regression, continuous vascularization of posterior retina, and reduced chance of PAR and recurrence but also reduce the magnitude of problems related to laser ablation and need for general anesthesia for laser in bigger babies.

Methodology

Study design- It will be a parallel group open-label single centre randomized control trial.

Site of study- Patients will be recruited from the ROP clinic at Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, Delhi. It will be a single centre study

Duration of study- Duration will be 12 months following the ethical and CTRI clearance

Participants

o   Eligibility criteria:

§  Zone 1 aggressive ROP

o   Exclusion criteria

§  Zone 2 disease

§  Stage 4 or 5 disease

§  Corneal or lenticular opacities

§  Parents not willing or giving consent

o   Both eyes of all patients will be treated similarly; only one eye (randomly selected by coin toss) will be chosen for statistical analysis to account for fellow eye correlation due to same-group 2-eye study design; if one eye has any exclusion criteria, then only the eligible fellow eye will be enrolled.

o   Patients will be enrolled after ethical clearance and after obtaining appropriate consent.

Intervention- It will be a parallel group randomized trial. All enrolled patients will undergo intravitreal ranibizumab injection as per the standard operating procedures. Following injection, the patients will either receive additional zone 2 posterior sparing laser ablation at 1 week (cases) or will be observed and followed-up as per the standard operating procedures, mentioned later (controls). Randomization of patients into cases and controls will be done as per computer random table at the time of intravitreal injection.

Allocation concealment will be done using sequentially numbered, sealed, opaque envelopes

-       Intravitreal Ranibizumab procedure- The infants, who will be cleared from neonatology, will receive 0.25mg in 0.025 ml intravitreal ranibizumab in each eye in an OT setting under strict aseptic conditions under topical anesthesia by a trained surgeon. Both eyes will be anaesthetized using 0.5% of Proparacaine hydrochloride ophthalmic solution followed by cleaning, draping and parts preparation. Intravitreal injection will be administered 1.5mm away from the limbus, in the most exposed part as per the ease of the surgeon. Each eye will receive the injection in a single setting. After the procedure, 0.5% moxifloxacin eye drops will be instilled in each eye.

-       Zone 2 posterior laser procedure: Retinal laser will be performed 1 week after injection in pediatric high dependency unit (PHDU) after clearance from the neonatologist. Pupils will be dilated using 0.5% tropicamide and 2.5% phenylephrine instilled twice, 10 minutes apart, at least 30 minutes before the treatment. The baby will be fed and burped 30 to 60 minutes before treatment. Adequate topical anesthetic drops will be instilled. Analgesic agent, fentanyl will be used intravenously in the dose of 2μg/kg bolus given 15 minutes prior to procedure followed by continuous infusion of 1μg/kg/hour increased as needed to a maximum of 3μg/kg/hour, till the completion of procedure (as part of the PHDU SOP). The pediatrician will monitor the vitals of the baby. The assistant will restrain the baby while the treating ophthalmologist will perform the procedure using laser indirect ophthalmoscopy and 20D or 28D condensing lens. Retinal laser ablation will be done using frequency-doubled Nd: YAG (532 nm) green laser with standard treatment parameters to achieve near-confluent laser burns of moderate intensity. Laser will be done in zone 2 anterior and zone 3 region as described by ICROP3.

In case of any adverse event such as apnea or bradycardia, the procedure will be stopped, and the situation will be reassessed once the pediatrician stabilizes the baby. If laser is not possible at 1 week due to any reason, it could be done till the next 3 days. If not, then those eyes would be excluded from the study.

Post-procedure, standard treatment with topical antibiotic, cycloplegic, steroids and artificial tears will be prescribed for 1 week duration.

Controls- Controls will include patients being observed without additional laser following intravitreal injection.

Outcome or Study variables

-       Patients will be followed-up at 1 week following anti-VEGF and then 2 weekly with dilated fundus examination and digital fundus photography (RetCam 3 imaging system) till 16weeks following injection or 50 weeks PMA whichever is earlier.

-       The study will be open label. The observation in both arms would not be masked as laser scars would be obviously discernible on examination in cases.

-       The following variables will be noted by a trained observer-

o   Regression of plus disease

o   Failure of regression with injection (failure of regression will be considered as persistence of plus disease; persistent disease will be non-resolution noted at 1 week visit following injection and confirmed 3 days later and will be treated with laser with or without sparing of zone 1 as per the discretion of the outcome investigator)

o   Progression of disease to stage 4 (will be managed as per standard operating procedures with vitrectomy)

o   Extent of vascularization

o   Persistent avascular retina (failure of progression of vascularization noted on 3 consecutive visits 2 weeks apart i.e. over a month period) and its extent; PAR will be managed with laser once the study period is over

o   Recurrence of ROP- stage and plus disease- and its timing (Recurrence will be defined as reappearance of stage and/ or plus disease after initial resolution of acute phase; it will be managed as per standard operating procedures; zone 1 recurrence will be treated with repeat ranibizumab injection and zone 2 or zone 3 recurrence will be treated with laser)

o   Refractive error at last follow-up (under atropine; rice grain size 1% atropine eye ointment applied three times per day for 3 days before the refraction)

o   Unfavorable anatomical outcome- progression to stage 5 or sequalae (macular drag or fold)

o   Safety assessment

§  Ocular

·      Lens injury, retinal detachment and endophthalmitis following intravitreal injection

·      Corneal edema, cataract, vitritis and exudative retinal detachment following laser treatment

§  Systemic

·      Adverse event during injection or laser procedure such as apnea, respiratory arrest, and bradycardia, as evaluated by observing anesthetist or pediatrician

Parents not completing follow up at 6 weeks (for primary objective) will not be included in the statistical analysis. However, those completing follow-up after 6 weeks but not till 50weeks PMA or 16 weeks post-injection, will be included in the analysis. Parents will be contacted by phone to encourage revisit and assess the outcomes.

Sample size: Considering the study by Gangwe et al.¹¹ where the proportion of eyes with recurrence of disease in patients of AROP following intravitreal ranibizumab monotherapy vs. combined laser and intravitreal ranibizumab injection at 6 weeks was 45.1% vs 6.7%, and alpha error of 5%, power of study 80% and 1:1 case: control allocation, the estimated sample size is 24 eyes in each group. As per convenience, 25 eyes will be recruited in each group.

Data capture- This will be done as per a clinical form entailing all the study features as mentioned above.

Data entry and analysis- The data from the clinical forms will be entered in an Excel workbook. Data analysis will be done using SPSS.23 software. The analyses of variables with continuous data will be performed as mean (with standard deviation) and median (with the range) while the categorical data will be expressed as frequency. Comparison between the groups will be done using Student-t test or Mann Whitney U test depending upon the data distribution. P value <0.05 will be considered statistically significant.

References

1.         Kumawat D, Sachan A, Shah P, Chawla R, Chandra P. Aggressive posterior retinopathy of prematurity: a review on current understanding. Eye (Lond). 2021 Apr;35(4):1140–58.

2.         Rashtriya Bal Swasthya Karyakram (RBSK), Ministry of Health & Family Welfare. Government of India. Guidelines for universal eye screening in newborns including ROP. 2016. 25–58 p.

3.         Chiang MF, Quinn GE, Fielder AR, Ostmo SR, Paul Chan RV, Berrocal A, et al. International Classification of Retinopathy of Prematurity, Third Edition. Ophthalmology. 2021 Oct;128(10):e51–68.

4.         Stahl A, Lepore D, Fielder A, Fleck B, Reynolds JD, Chiang MF, et al. Ranibizumab versus laser therapy for the treatment of very low birthweight infants with retinopathy of prematurity (RAINBOW): an open-label randomised controlled trial. Lancet. 2019 Oct 26;394(10208):1551–9.

5.         Mintz-Hittner HA, Kennedy KA, Chuang AZ. Efficacy of Intravitreal Bevacizumab for Stage 3+ Retinopathy of Prematurity. New England Journal of Medicine. 2011 Feb 17;364(7):603–15.

6.         Stahl A, Sukgen EA, Wu WC, Lepore D, Nakanishi H, Mazela J, et al. Effect of Intravitreal Aflibercept vs Laser Photocoagulation on Treatment Success of Retinopathy of Prematurity: The FIREFLEYE Randomized Clinical Trial. JAMA. 2022 Jul 26;328(4):348–59.

7.         Parchand SM, Agrawal D, Gangwe A, Saraogi T, Agrawal D. Combined intravitreal ranibizumab and zone I sparing laser ablation in infants with posterior zone I retinopathy of prematurity. Indian J Ophthalmol. 2021 Aug;69(8):2164–70.

8.         Kumari A, Surve A, Azad SV, Chawla R, Chandra P, Thukral A, et al. An Observational Study of Different Treatment Practices for Aggressive Posterior Retinopathy of Prematurity. J Pediatr Ophthalmol Strabismus. 2021;58(6):370–6.

9.         Kim R, Kim YC. Posterior Pole Sparing Laser Photocoagulation Combined with Intravitreal Bevacizumab Injection in Posterior Retinopathy of Prematurity. J Ophthalmol. 2014;2014:257286.

10.       Yoon JM, Shin DH, Kim SJ, Ham DI, Kang SW, Chang YS, et al. OUTCOMES AFTER LASER VERSUS COMBINED LASER AND BEVACIZUMAB TREATMENT FOR TYPE 1 RETINOPATHY OF PREMATURITY IN ZONE I. Retina. 2017 Jan;37(1):88–96.

11.       Gangwe AB, Agrawal D, Gangrade AK, Parchand SM, Agrawal D, Azad RV. Outcomes of early versus deferred laser after intravitreal ranibizumab in aggressive posterior retinopathy of prematurity. Indian J Ophthalmol. 2021 Aug;69(8):2171–6.