Prematurity And The Eye ✅ Flashcards
When does vascularisation of the retina begin?
Around 14 weeks gestation
When is vascularisation of the retina complete?
Term
What stimulates vascularisation of the retina?
Vascular endothelial growth factor (VEGF-A) and insulin like growth factor (IGF-1), which work synergistically
What induces VEGF production?
Physiological fetal retinal hypoxia
Is IGF-1 production oxygen dependant?
No, it is oxygen independent
What do rising levels of IGF-1 stimulate?
Retinal angiogenesis during the second and third trimester
What is retinopathy of prematurity?
A neovascular disorder
Who does retinopathy of prematurity affect?
Infants born at less than 32 weeks gestational age
What are important additional risk factors for retinopathy of prematurity?
- Extremely low birth weight (<1000g)
- Early supplemental oxygen requirements
- Acidosis
What % of babies born <1000g will develop ROP?
50%
What percent of babies born under 1000g will reach the threshold for treatment of ROP?
15%
Who should be screened for ROP?
All babies born under 32 weeks completed gestation and less than 1500g
What are the phases of development of ROP?
- Hyperoxic phase
2. Hypoxia phase
What happens in the hyperoxic phase in ROP?
Delivery into a high oxygen environment causes down regulation of VEGF, halting the normal progression of vascular tissue into the developing anterior retina
What happens in the hypoxic phase of ROP?
The unvasclarised anterior retina becomes increasingly ischaemic as it matures, VEGF is up regulated and leads to neovasularisation from the ridge of mesenchymal spindle cells at the anterior border of the vascularised retina
What happens in the hypoxic phase of ROP if left untreated?
The abnormal new vascular network creates a tractional retinal detachment and blindness
What does the international classification of ROP classify on the basis of?
- Stages of ROP development
- Zones of location in the retina
What is stage 1 of ROP?
Demarcation line at anterior edge of vascularised retina
What is stage 2 of ROP?
The line becomes thickened edge
What is stage 3 of ROP?
The ridge develops neovascularisation
What is stage 4 of ROP?
Localised tractional retinal detachment
What is stage 5 of ROP?
Funnel retinal detachment
What is plus disease in the classification of ROP?
Dilatation and tortuosityof the retinal vessels
What are the zones of ROP?
Need a pic, but basically zone 1 includes disc and fovea, then expands out to zone 3
What is aggressive posterior ROP?
Zone 1 disease, neovascularisation is not localised to the ridge
What are the most aggressive forms of ROP?
Zone 1 and posterior zone 2
What is the treatment threshold for ROP based on?
- The zone of the disease
- Disease stage
- Presence of retina vascular dilatation and tortuisity (plus disease)
What is the importance treatment of timely in ROP?
It can prevent progression to retinal detachment and blindness
What has recently been discovered to correlate with the development of ROP?
A drop off in postnatal weight gain
What does a drop off in postnatal weight gain mirror?
A fall in IGF-1 levels
What is the clinical relevance of the development of ROP being correlated to a drop off in postnatal weight gain?
A computer based algorithm based on postnatal weight gain is being developed, which may help future identification of babies most at risk
What is currently the preferred treatment for severe ROP?
Laser ablation of the avascular, ischaemic anterior retina
What is a promising new treatment for severe ROP?
Intra-vitreal injection of an anti-VEGF agent
Give 2 example of anti-VEGF agents
Bevacizumab
Ranibizumab
What is the advantage of anti-VEGF treatment over laser in ROP?
Easier and quicker to perform
What is the disadvantage of anti-VEGF treatment over laser in ROP?
Systemic absorption depresses serum VEGF levels for several weeks which may have systemic consequences, and the resultant prolonged absence of VEGF in the eye also delays the normal vascularisation of the anterior retina
What is the result of the delayed vascularisation of the anterior retina with anti-VEGF agents?
It is non-perfused and ischaemic tor months beyond term
What is anti-VEGF treatment reserved for in the UK?
The most severe cases, where laser therapy is not possible or sufficiently effective
