Retinopathy of prematurity

The development of the rat model of retinopathy of prematurity

Retinopathy of prematurity (ROP) is a potentially blinding disease affecting premature infants. ROP is characterized by pathological ocular angiogenesis or retinal neovascularization (NV). Models of ROP have yielded much of what is currently known about physiological and pathological blood vessel growth in the retina. The rat provides a particularly attractive and cost effective model of ROP. The rat model of ROP consistently produces a robust pattern of NV, similar to that seen in humans. This model has been used to study gross aspects of angiogenesis. More recently, it has been used to identify and therapeutically target specific genes and molecular mechanisms involved in the angiogenic cascade. As angiogenesis occurs as a complication of many diseases, knowledge gained from these studies has the potential to impact nonocular angiogenic conditions. This article provides historical perspective on the development and use of the rat model of ROP. Key findings generated through the use of this model are also summarized.

Arterial oxygen fluctuation and retinopathy of prematurity in very-low-birth-weight infants

OBJECTIVE

To determine the influence of arterial oxygen fluctuation on development of threshold ROP.

STUDY DESIGN

Retrospective study of 231 infants, < or =1500 g birth weight, who were admitted to Arkansas Children's Hospital NICU from January 1993 to June 1995. Fluctuation in partial pressure of dissolved arterial oxygen (PaO(2)) was expressed as coefficient of variation (CoV) for each infant. We investigated the relationship between CoV at three intervals and the risk of developing threshold ROP.

RESULTS

The odds ratio (OR) of developing threshold ROP versus prethreshold ROP or less associated with a 10% increase in the CoV during the first 5 days of oxygen therapy was 1.44, and during the first 10 days was 1.51. When analysis was restricted to infants receiving 30 days of therapy, the OR during the first 5 days of therapy was 1.67, during the first 10 days was 1.82, and during days 11-30 was 1.68.

CONCLUSIONS

Very-low-birth-weight infants experiencing fluctuating PaO(2) are at higher risk of threshold ROP.

Peripheral retinal ablation for threshold retinopathy of prematurity in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

In premature infants with threshold retinopathy of prematurity (ROP) does peripheral retinal ablation, by any means, reduce the incidence of adverse ophthalmic outcome?

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included a search of the Cochrane Neonatal Group Register of Clinical Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts from pediatric and ophthalmologic meetings, letters and expert informants. Search terms included "Retinopathy of Prematurity" [MeSH Terms], "Retrolental Fibroplasia" [All Fields] and "Lightcoagulation" [All Fields] or "Cryosurgery" [All Fields]. In addition, a personal bibliographic database was used as a cross-reference.

SELECTION CRITERIA

All trials in human premature infants with threshold ROP utilizing random or quasi random allocation to either peripheral retinal ablation of the avascular retina, by any means, or concurrent control group with independent outcome assessment were initially selected for review. Following methodologic review, only studies using random allocation were selected for data extraction.

DATA COLLECTION AND ANALYSIS

Relevance and validity were assessed by the two authors and consensus reached. Each author extracted clinical outcomes from valid reports independently. Data analysis was conducted according to the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Two randomised trials were identified. Data from these studies show that peripheral retinal ablation reduces the risk of (1) early unfavorable retinal structure from 47. 9% to 28.1% (absolute risk reduction 19.8% [95% CI 27.9 - 11.8%]), (2) unfavorable retinal structure in early childhood from 44.3% to 26.3% (absolute risk reduction 18% [95% CI 27.0 - 9.1%]) and (3) unfavorable visual acuity in early childhood from 63% to 50.6% (absolute risk reduction 12.2% [95% CI 21.2 - 3.1]). In addition, visual fields in sighted eyes were slightly smaller in the treated (51.3 degrees +/- 11.8 degrees ) group as compared to the control (58.2 degrees +/- 14.5 degrees ) group.

REVIEWER'S CONCLUSIONS

Peripheral retinal ablation reduces the incidence of adverse ophthalmic outcome in premature infants with threshold ROP. In sighted eyes, peripheral retinal ablation may reduce the size of the visual field. At this stage, long term outcomes remain unknown.