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

Targeting adenosine A2A receptors for early intervention of retinopathy of prematurity

Retinopathy of prematurity (ROP) continues to pose a significant threat to the vision of numerous children worldwide, primarily owing to the increased survival rates of premature infants. The pathologies of ROP are mainly linked to impaired vascularization as a result of hyperoxia, leading to subsequent neovascularization. Existing treatments, including anti-vascular endothelial growth factor (VEGF) therapies, have thus far been limited to addressing pathological angiogenesis at advanced ROP stages, inevitably leading to adverse side effects. Intervention to promote physiological angiogenesis during the initial stages could hold the potential to prevent ROP. Adenosine A2A receptors (A2AR) have been identified in various ocular cell types, exhibiting distinct densities and functionally intricate connections with oxygen metabolism. In this review, we discuss experimental evidence that strongly underscores the pivotal role of A2AR in ROP. In particular, A2AR blockade may represent an effective treatment strategy, mitigating retinal vascular loss by reversing hyperoxia-mediated cellular proliferation inhibition and curtailing hypoxia-mediated neovascularization in oxygen-induced retinopathy (OIR). These effects stem from the interplay of endothelium, neuronal and glial cells, and novel molecular pathways (notably promoting TGF-β signaling) at the hyperoxia phase. We propose that pharmacological targeting of A2AR signaling may confer an early intervention for ROP with distinct therapeutic benefits and mechanisms than the anti-VEGF therapy.

Visual outcomes and their association with grey and white matter microstructure in adults born preterm with very low birth weight

Individuals born with very low birth weight (VLBW; < 1500 g) have a higher risk of reduced visual function and brain alterations. In a longitudinal cohort study, we assessed differences in visual outcomes and diffusion metrics from diffusion tensor imaging (DTI) at 3 tesla in the visual white matter pathway and primary visual cortex at age 26 in VLBW adults versus controls and explored whether DTI metrics at 26 years was associated with visual outcomes at 32 years. Thirty-three VLBW adults and 50 term-born controls was included in the study. Visual outcomes included best corrected visual acuity, contrast sensitivity, P100 latency, and retinal nerve fibre layer thickness. Mean diffusivity, axial diffusivity, radial diffusivity, and fractional anisotropy was extracted from seven regions of interest in the visual pathway: splenium, genu, and body of corpus callosum, optic radiations, lateral geniculate nucleus, inferior-fronto occipital fasciculus, and primary visual cortex. On average the VLBW group had lower contrast sensitivity, a thicker retinal nerve fibre layer and higher axial diffusivity and radial diffusivity in genu of corpus callosum and higher radial diffusivity in optic radiations than the control group. Higher fractional anisotropy in corpus callosum areas were associated with better visual function in the VLBW group but not the control group.

Visual function in adults born preterm with very low birth weight-A two-country birth cohort study

PURPOSE

The purpose of the study was to investigate visual function and vision-related general health in adults that were born preterm with very low birth weight (VLBW: birth weight < 1500 g) in their 30s-40s.

METHODS

We recruited 137 adults born preterm with VLBW and 158 term-born controls aged 31-43 years from two birth cohorts: the Helsinki Study of Very Low Birth Weight Adults (Finland) and the NTNU Low Birth Weight in a Lifetime Perspective study (Norway). We used neonatal data and measured refraction, best-corrected visual acuity (BCVA) using the Early Treatment Diabetic Retinopathy Study (ETDRS) chart, contrast sensitivity, visual fields, intraocular pressure (IOP), self-reported vision-targeted health status with the National Eye Institute Visual Function Questionnaire-25.

RESULTS

VLBW adults had a lower BCVA ETDRS score than controls: mean (SD) better eye 86.7 (13.4) versus 90.2 (4.4), p = 0.02; mean (SD) worse eye 82.3 (14.9) versus 87.6 (4.6), p = 0.003. VLBW adults also had lower contrast sensitivity thresholds in several spatial frequencies and scored lower than controls in eight out of the 12 subscales of self-reported vision-targeted health status. Refraction, visual fields and IOP were similar between groups. Two VLBW participants were blind. None had been treated for retinopathy of prematurity.

CONCLUSION

We suggest that lower visual function and vision-related health represent life-long consequences of prematurity and VLBW in the studied 31- to 43-year-old cohort. The underlying mechanisms remain to be determined.

Neonatal sepsis as a cause of retinopathy of prematurity: An etiological explanation

Retinopathy of prematurity (ROP) is a complex neonatal disorder with multiple contributing factors. In this paper we have mounted the evidence in support of the proposal that neonatal sepsis meets all requirements for being a cause of ROP (not a condition, mechanism, or even innocent bystander) by means of initiating the early stages of the pathomechanism of ROP occurrence, systemic inflammation. We use the model of etiological explanation, which distinguishes between two overlapping processes in ROP causation. It can be shown that sepsis can initiate the early stages of the pathomechanism via systemic inflammation (causation process) and that systemic inflammation can contribute to growth factor aberrations and the retinal characteristics of ROP (disease process). The combined contribution of these factors with immaturity at birth (as intrinsic risk modifier) and prenatal inflammation (as extrinsic facilitator) seems to provide a cogent functional framework of ROP occurrence. Finally, we apply the Bradford Hill heuristics to the available evidence. Taken together, the above suggests that neonatal sepsis is a causal inducer of ROP.

A novel marker for predicting type 1 retinopathy of prematurity: C-reactive protein/albumin ratio

PURPOSE

We aimed to investigate whether the C-reactive protein (CRP) to albumin ratio (CAR) an inflammatory predictor can be used as a marker for the development of ROP.

METHODS

Gestational age, birth weight, gender, neonatal, and maternal risk factors were recorded. The patients were divided into two groups: those who did not develop ROP (ROP -) and those who developed ROP (ROP +). The ROP + group was further separated into two groups: those who required treatment (ROP + T) and those who were not treated (ROP + NT). The following parameters were noted in the first postnatal week and at the end of the first postnatal month: CRP, albumin, CAR, white blood cell (WBC), neutrophil, lymphocyte, neutrophil-to-lymphocyte ratio (NLR), distribution red cell width (RDW), platelet (Plt), and RDW/platelet ratio.

RESULTS

We evaluated 131 premature infants who met the inclusion criteria. There was no difference between the main groups in hemogram parameters and CAR at the postnatal first week. WBC count (p = 0.011), neutrophil count (p = 0.002), and NLR were high (p = 0.004) in the ROP + group at the end of the postnatal 1st month. The CAR level at the end of the first month was higher in the ROP + group (p = 0.027). CAR was similar between the ROP + T and ROP + NT groups (p = 0.112) in the postnatal first week but higher in the treatment-required group at the end of the first month (p < 0.01).

CONCLUSION

High CAR and high NLR at the end of the postnatal first month can be used to predict the development of severe ROP.

Visual function correlates with neurodevelopment in a population cohort of school-aged children born extremely preterm

AIM

To investigate visual function and neurodevelopment in a geographically defined population cohort of school-aged children born extremely preterm.

METHODS

All children born extremely preterm in Central Norway between 2006 and 2011 (n=65) were identified, and 36 (median age, min/max: 13, 10/16) were included. Best-corrected visual acuity (BCVA), contrast sensitivity (four spatial frequencies), parent-reported challenges and neuropsychological testing in learning, executive functions, motor skills, perception, reaction time, working and visual memory, processing speed, and pattern separation were measured. Brain MRI (3T) was acquired and read by a neuroradiologist.

RESULTS

Median (min/max) BCVA letter score was 85 (35/91) in the better and 82 (13/89) in the worse eye. ROP participants (n=7) had lower contrast sensitivity in the two highest spatial frequencies (p = 0.024 and p = 0.004). Parent-reported challenges correlated negatively with BCVA (learning: p = 0.014; executive functions: p = 0.002; motor skills: p = 0.000; and perception: p = 0.001), while motor skills correlated negatively with one (p = 0.010) and perception with two (p = 0.003 and p = 0.009) of four spatial frequencies. Neuropsychological tests were reduced relative to norms. None had MRI-verified preterm brain injury.

CONCLUSION

Visual function was subnormal and correlated with parent-reported challenges in a small cohort of extremely preterm school-aged children, indicating that visual function may be a marker of neurodevelopmental outcomes.

Retinopathy of prematurity

Retinopathy of prematurity (ROP) is a devastating neurovascular disease of the retina in newborn infants that can lead to vision deficits or even blindness. In this concise review we discuss our current knowledge about diagnosis, etiology, pathogenesis, intervention, and outcomes of the disease. Major advancements have been made both in categorizing the disease in the new International Classification of Retinopathy of Prematurity, Third Edition classification and in treating severe ROP with anti-vascular endothelial growth factor (VEGF) agents. New development always creates new questions and opens up new areas of research. We will discuss in this review both the benefits and downsides of the new anti-VEGF treatment approaches in ROP, especially in light of our improved understanding of the underlying ROP pathophysiology. We also offer pointers to areas where more research is needed.

Extreme prematurity: Risk and resiliency

Individuals born extremely preterm (before 28 weeks of gestation) comprise only about 0.7% of births in the United States and an even lower proportion in other high resource countries. However, these individuals account for a disproportionate number of children with cerebral palsy, intellectual deficit, autism spectrum disorder, attention deficit hyperactivity disorder, and epilepsy. This review describes two large multiple center cohorts comprised of individuals born extremely preterm: the EPICURE cohort, recruited 1995 in the United Kingdom and the Republic of Ireland, and the Extremely Low Gestational Age Newborn (ELGAN), recruited 2002-2004 in five states in the United States. The primary focus of these studies has been neurodevelopmental disorders, but also of interest are growth, respiratory illness, and parent- and self-reported global health and well-being. Both of these studies indicate that among individuals born extremely preterm the risks of most neurodevelopmental disorders are increased. Early life factors that contribute to this risk include perinatal brain damage, some of which can be identified using neonatal head ultrasound, bronchopulmonary dysplasia, and neonatal systemic inflammation. Prenatal factors, particularly the family's socioeconomic position, also appear to contribute to risk. For most adverse outcomes, the risk is higher in males. Young adults born extremely preterm who have neurodevelopmental impairment, as compared to those without such impairment, rate their quality of life lower. However, young adults born extremely preterm who do not have neurodevelopmental impairments rate their quality of life as being similar to that of young adults born at term. Finally, we summarize the current state of interventions designed to improve the life course of extremely premature infants, with particular focus on efforts to prevent premature birth and on postnatal efforts to prevent adverse neurodevelopmental outcomes.