Flashcards in Retinopathy of Prematurity Deck (98)
What did ROP used to be called?
Why was the first multicenter, randomized controlled trial from 1953-1954 known as the trial that changed oxygen use?
- included 18 hospitals
- n= 786 infants < 1500g > 2 dol
- identified oxygen toxicity as the cause of neonatal blindness
What were the results from that study?
survival was similar with FiO2 < 50% as conventional therapy, but the incidence of ROP was very different (72% with conventional tx and 33% with limited O2)
What were the policy ∆ made after that study?
the use of O2 was restricted in nurseries and FiO2 < 40% was considered safe
What was the unintentional effect of restricting the use of O2 therapy in nurseries?
- for every baby whose sight was saved, 16 died
- many more developed CP
What is ROP?
a disorder of the developing retinal vasculature resulting from interruption of normal progression of newly forming retinal vessels
What is the progression of ROP following the initially hyperoxic insult?
vasoconstriction and obliteration of the advancing capillary bed > followed by neovascularization extending into the vitreous > retinal edema > retinal hemorrhages > fibrosis > traction on, and eventual detachment of, the retina
What is the foveal pit?
a depression off center in the macula of the retina; only takes up < 1% of retinal size but is the area of most acute vision (50% of the visual cortex of the brain), only cones are present and no blood vessels
What is cicatricial ROP?
What percentage of blindness in preschool children in the US is a result of ROP?
When does threshold dz occur?
threshold dz occurs at a median age of PCA of 36-37 wk regardless of GA at birth of chronologic age
In the normally developing retina, when do retinal vessels develop?
there are no retinal vessels until 16 wk GA
What occurs at 16 wk GA?
in response to a stimulus ( relative hypoxia stimulates the release of angiogenic factors as the retina thickens), cells derived from the mesenchyme traveling in the nerve fiber layer emanate from the optic nerve head and enter the ocular cavity (grow like a splay)
What are the cells that emanate from the optic nerve?
precursors to the retinal vessel system
What happens to the primitive retinal vessel system after it splays from the optic head?
a fine capillary network advances through the retina to ora serrata, or retinal ridge. more mature vessels form behind this advancing network.
When is vascularization of the ora serrata complete?
Nasal side: ~ 8 months GA
Temporal side: term
What is the risk of ROP once the retinal vasculature is completely vascularized?
no longer susceptible to insults that lead to ROP
Under what fetal conditions does normal retinal vascularization occur?
HYPOXIC environment of the uterus; best pO2 is about 25-30 mm/Hg
Why are VEGF and ILG-1 important?
regulation of the process of retinal vascularization involves various factors including VEGF and ILG-1 working in combination
What controls VEGF production?
available O2 in the environment
What is the effect of hypoxia on VEGF production?
What is the effect of hyperoxia on VEGF production?
What is the function of IGF-1?
When is IGF-1 present in the fetus?
levels increase in 3rd trimester (becomes abundant in amniotic fluid)
What is the effect of protein deficiency and IGF-1?
very low levels of IGF-1
What is the function of VEGF?
causes retinal angiogenesis
What are the two stages of ROP?
1) early vasoconstriction and obliteration of the capillary network
What is the response of the developing retinal capillary network to premature birth?
In response to hyperoxic insult, VEGF production ceases. This causes angiogenic development to stop, vessels constrict and "buds shrink". The entire vascular area becomes metabolically quiet for about 4 weeks
Why are IGF-1 levels low in the LBW infant in the early postnatal period?
loss of maternal levels (loss of placenta) and poor nutrition