Introduction
This is a major cause of blindness in children
- Prevalence of around 31.9% worldwide
- Retinal vascularisation usually completes at 32WG, just before birth, but it is dependent on oxygen gradients.
- It begins at 16WG, with hypoxia inducing VEGF
- Following premature birth, the child is exposed to hyperoxia, inhibiting VEGF
- The subsequent increase in the metabolic demand of the eye triggers a excessive release of VEGF, leading to poor neovascularisation
Dead Giveaways
The appearance of ROP is very distinct, and dependent on the phase, stage and zone
Basic view:
Phase 1:
Follows from birth, and is the delayed development of normal retinal vasculature from down-regulation of VEGF
Consists of stage 1 and 2
Phase 2:
Follows after phase 1
Abnormal upregulation of VEGF causes proliferation of new vessels
These vessels are very leaky, and can enter the vitreous, causing vision loss
Consists of 3rd stage onwards (images from Moran core)
Stage 1:
The lack of formation of vasculature leaves an avascular peripheral retina
Characterised by a flat junction demarcation line, which in this image can just be made out by tracing along the vasculature
Stage 2:
Demarcation line grows to form a ridge
Most ROP stops at stage 1 or 2, and so only monitoring is required as treatment
The ridge line is very evidently seen, being broader and thicker
Stage 3:
Beginning of phase 2. The incomplete vasculature leads to ischaemia
The vasculature cannot support the high demand of the retina, and so the response is to trigger more VEGF release
In ROP PLUS disease, the existing vessels slowly become tortuous and dilated
We can see there is an indistinct velvet appearance now, and rugged borders.
The risk of retinal detachment has a cicatricial sequelae, and thus poor structure and visual outcome
Haemorrhages seen at the ridge, indicating fibrovascular tissue present, and neovascularisation at border.
Stage 4:
Has 2 versions, A and B
A = Fovea is uninvolved
B = Fovea is involved
Associated with a severe change in the retinal structure due to the abnormal vessel growth.
New BV leakage causes fluid build up in the retina, leading to a total or partial exudative retinal detachment
Subtotal retinal detachment starts at the fibrovascular edge, causing anterior retina to undergo traction.
Stage 5:
Also associated with 2 versions, A and B
Usually not reached, unless aggressive in nature
The total detachment caused by the tractional forces can cause:
A = evolvement into a funnel shape
B = closure of that funnel
Shows stage 5 A, where the funnel shape is beginning to form, and the retina is collapsing into the centre.
diagnostic features
Risk:
Low birthweight of infants (65%)
Birth before 32WG
Birth weight < 1500g
The lower the weight and earlier the birth, the more involved the central zones are, and thus the more advanced
Zones:
Clock hours also used to identify the extent of disease Zone 1: Radius of circle is 2x the distance from ONH to fovea, ONH as centre
Zone 2: Concentric to zone 1, but radius is from ONH to ora serrata
Zone 3: Residual temporal crescent anterior to zone 2
Plus Disease:
Tendency to progress, and poor prognostic sign
Dilated veins, tortuous arteries in at least 2 quadrants
No pupil dilation
Iris vessels also affected
More severe stage 3
Threshold Disease:
Blindness in 50% without therapy
5 continuous or 8 non-continuous clock hours of extraretinal neovascularisation in zone 1 or 2
Associated with plus disease
Aggressive ROP
Posterior location in zone 1 or zone 2, with plus disease, and ill-defined in nature
Leads to stage 5
Treatment:
Depends on circumstance and severity
High O2 supplement for premature infants causes increased incidence of ROP
100% O2 --> higher level of blindness
50% O2 --> associated with increased death rates
Reduced oxygen can be helpful in phase 1, but not effective in phase 2
Early retinal ablation via laser therapy should be used for infants with high progression risk of RD and vision loss
Laser photocoagulation for threshold disease in successful in 85% of cases
Complications include VF loss, induced myopia and retinal destruction
Intravitreal anti-VEGF can be helpful
Lens sparing pars plana vitrectomy can treat detachment, and is successful for 89% of infants with stage 4A