Optical coherence tomography of the preterm eye: from retinopathy of prematurity to brain development

Preterm infant retinal OCT markers of perinatal health and retinopathy of prematurity

The increasing survival of preterm infants has led to the importance of improving long-term outcomes associated with preterm birth. Antenatal and perinatal insults not only impact mortality, but also long-term disability. While in the intensive care nursery, preterm infants are also exposed to various stressors that lead to long-term cognitive deficits. It is therefore critical to identify early, low-stress, non-invasive biomarkers for preterm infant health. Optical coherence tomography (OCT) is a powerful imaging modality that has recently been adapted to the infant population and provides noninvasive, high-resolution, cross-sectional imaging of the infant eye at the bedside with low stress relative to conventional examination. In this review we delve into discussing the associations between preterm systemic health factors and OCT-based retinal findings and their potential contribution to the development of non-invasive biomarkers for infant health and for retinopathy of prematurity (ROP).

Visuopathy of prematurity: is retinopathy just the tip of the iceberg?

Research on retinopathy of prematurity (ROP) focuses mainly on the abnormal vascularization patterns that are directly visible for ophthalmologists. However, recent findings indicate that children born prematurely also exhibit changes in the retinal cellular architecture and along the dorsal visual stream, such as structural changes between and within cortical areas. Moreover, perinatal sustained systemic inflammation (SSI) is associated with an increased risk for ROP and the visual deficits that follow. In this paper, we propose that ROP might just be the tip of an iceberg we call visuopathy of prematurity (VOP). The VOP paradigm comprises abnormal vascularization of the retina, alterations in retinal cellular architecture, choroidal degeneration, and abnormalities in the visual pathway, including cortical areas. Furthermore, VOP itself might influence the developmental trajectories of cerebral structures and functions deemed responsible for visual processing, thereby explaining visual deficits among children born preterm.

Retinal structural changes in preterm children without retinopathy of prematurity

PURPOSE

The aim of this study was to compare all retinal layers' thickness in full-term and preterm children without retinopathy of prematurity (ROP).

METHODS

Cross-sectional study including two groups of patients: group 1 children with history of preterm gestation without ROP (gestational age < 37 weeks) and group 2 healthy children with history of full-term gestation. All subjects underwent an ophthalmic examination including spectral domain-optical coherence tomography. After automatic retinal segmentation, each retinal layer thickness (eight separate layers and overall thickness) was calculated in all nine Early Treatment Diabetic Retinopathy Study areas. Demographic, systemic, gestational, and birth data were collected. Generalized additive regression models were used to analyze the data.

RESULTS

Fifty-one children (51 eyes) were recruited, 19 full-term and 32 preterm children, mean age at ophthalmic examination of 10.58 (4.21) and 14.13 (3.16), respectively. In multivariable analysis, the preterm group's retinal thickness was significantly decreased in total retina nasal outer sector, ganglion cell layer (GCL), and inner plexiform layer (IPL), specifically GCL temporal outer (p = 0.010), GCL superior outer (p = 0.009), IPL temporal outer (p = 0.022), and IPL superior outer (p = 0.004), when compared with full-term group. From the variables compared only with birth head circumference that influenced the models, a non-linear association was identified and consequently modeled with splines through a generalized additive model.

CONCLUSION

This study suggests that preterm children without ROP have structural retinal alterations, mostly in GCL and IPL in outer areas of the macula. Therefore, it is crucial to question gestational history since these retinal changes may be found later in life leading to useless investigation.

The safety and effectiveness of 0.16 mg bevacizumab plus or minus additional laser photocoagulation in the treatment of retinopathy of prematurity

Purpose

Retinopathy of prematurity (ROP) is the leading cause of preventable blindness in premature infants. Antivascular endothelial growth factor (anti-VEGF) therapy has been used increasingly in treatment as a pharmacological alternative to laser therapy. In this study, we evaluate the results of low-dose anti-VEGF treatments.

Methods

Design: Retrospective--observational study. Infants who had been evaluated for ROP disease between February 2016 and February 2017 were assessed. We retrospectively reviewed the ROP stages, treatment results, and complications. Laser photocoagulation (LPC) and intravitreal bevacizumab (0.16 mg IVB) were used for treatment and fundus fluorescein angiography (FFA) was also performed in some of the cases.

Results

IVB was applied to 43 infants. A macular hole was seen in one infant's eye after IVB. LPC was applied to avascular areas in 21 infants. In three patients, persistence of the disease was observed after administration of a low dose of IVB. Additional LFK was performed in these patients. None of the infants who received LPC had any complications.

Conclusion

IVB is increasingly becoming the first-line treatment for ROP. For severe ROP, 0.16 mg IVB is effective. Using LPC to treat avascular areas after 70 weeks' gestational age (GA) may decrease the risk of late recurrence and appears to be a safe treatment to use.

HANDHELD SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY IMAGING THROUGH THE UNDILATED PUPIL IN INFANTS BORN PRETERM OR WITH HYPOXIC INJURY OR HYDROCEPHALUS

PURPOSE

The authors investigated feasibility of undilated handheld spectral domain optical coherence tomography (SDOCT) retinal imaging in preterm infants and children with neurologic abnormalities.

METHODS

Under an institutional review board-approved protocol, the authors attempted handheld SDOCT imaging of the retina, choroid, and optic nerve in infants and young children without pupil dilation. Scans were analyzed for quality and successful capture of foveal, optic nerve, and retinal structural parameters and abnormalities.

RESULTS

The authors obtained images through an undilated pupil of 11 infants/children over 28 eye imaging sessions, 27 at the bedside without sedation, and one under anesthesia. Infants had retinopathy of prematurity (n = 8), hypoxic ischemic encephalopathy (n = 2), or obstructive hydrocephalus (n = 1 child). Pupil sizes ranged from 1.0 mm to 3.5 mm. The authors captured fovea and optic nerve scans in 25/28 eye imaging sessions, with scans of adequate quality to discern prespecified foveal and optic nerve morphology, and of the 25 sessions, the choroidal-scleral junction was visible in all but 6 sessions.

CONCLUSION

Undilated, handheld SDOCT imaging is a potential alternative method to evaluate the retina and optic nerve in patients with relative contraindication to pharmacological pupil dilation. This approach will enable the study of the eye-brain connection and ocular manifestations of neurologic diseases.

Oxidative stress in the retina: implications for Retinopathy of Prematurity

Oxygen supplementation has been used as a part of respiratory care for preterm and term newborns since the beginning of 19^th century. Although oxygen administration can be life-saving, reactive oxygen species (ROS) and reactive nitrogen species (RNS) due to hyperoxia can have detrimental effects in the developing organs of the preterm infants, with both short and long term consequences. Oxygen toxicity on the immature tissues of preterm infants can contribute to the development of several diseases like retinopathy of prematurity (ROP) and bronchopulmonary dysplasia (BPD). The vascular development of human retina is completed at term, whereas the neural retina develops up to 5 years of age. Disruption of the normal retinal neurovascular growth is the pathognomonic feature of ROP, and can lead to vision threatening disease or even blindness. It is estimated that at least 100,000 infants all over the world will be blind every year due to ROP, which is the leading cause of blindness in children. In this review we will discuss the role of ROS and RNS in the development of ROP, and how through historical, epidemiological, and developmental aspects of this devastating disease, we can design future research for its prevention and treatment.

Simultaneous Fluorescein Angiography and Spectral Domain Optical Coherence Tomography Correlate Retinal Thickness Changes to Vascular Abnormalities in an In Vivo Mouse Model of Retinopathy of Prematurity

Background

Retinopathy of prematurity (ROP) is a condition of abnormal retinal vascular development (RVD) in premature infants. Fluorescein angiography (FA) has depicted phases (early, mid, late, and mature) of RVD in oxygen-induced retinopathy (OIR) mice. We sought to establish the relationship between retinal structural and vascular changes using simultaneous FA and spectral domain optical coherence tomography (SD-OCT).

Method

63 mice were exposed to 77% oxygen at postnatal day 7 (P7) for 5 days, while 63 mice remained in room air (RA). Total retinal thickness (TRT), inner retinal thickness (IRT), and outer retinal thickness (ORT) were calculated at early (P19), mid (P24), late (P32), and mature (P47) phases of RVD.

Results

TRT was reduced in OIR (162.66 ± 17.75 μm, n = 13) compared to RA mice at P19 (197.57 ± 3.49 μm, n = 14), P24, P32, and P49 (P < 0.0001). ORT was similar in RA and OIR mice at all ages (P > 0.05). IRT was reduced in OIR (71.60 ± 17.14 μm) compared to RA (103.07 ± 3.47 μm) mice at P19 and all ages (P < 0.0001).

Conclusion

We have shown the spatial and temporal relationship between retinal structure and vascular development in OIR. Significant inner retinal thinning in OIR mice persisted despite revascularization of the capillary network; further studies will elucidate its functional implications in ROP.