Retinopathy of Prematurity

Fig.1: Nurses caring for a premature infant, Philadelphia General Hospital, (UPennNursing)

The first wave of ROP occurred following the introduction of Oxygen Cot therapy in pediatric hospitals. (Ryan H.) The oxygen therapy was intended increase survival rates of babies born before 31 weeks of gestation. Though the oxygen therapy does improve infant survival, many went on to develop aberrant vascularization of the retina classified as ROP.

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The pathology of ROP presents in two phases.

1. During hyperoxia due to oxygen therapy, hypoxic VEGF signaling is suppressed and vascularization of the peripheral retina fails.
2. Removal from hyperoxic environment drives plethoric VEGF signaling, causing tortuosity of existing blood vessels and ectopic vascularization

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Depending on the severity of the two stages, infants can fit into five stages of ROP progression.

 

1. Fig.2A – A faint demarcation line can be seen between vascularized and avascularized retina. Normally heals without intervention.
2. Fig.2B – The demarcation line begins form a ridge. Tufts of vasculature can be seen at the ridgeline. However, often heals without intervention.
3. Fig.2C – Extraretinal vasculature can be seen in the vitreous of the eye. Occasionally heals without intervention, but often treatment is considered at this stage.
4. Fig.2D – Partial retinal detachment. Scar tissue formation, bleeding, and abnormal vesicle formation pulls the retina away from the wall of the eye.
5. Full retinal detachment, without intervention the infant will have severe visual defects and even blindness.

 

Fig2: Stages of ROP severity (Hartnett)

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Standard of Care

The most effective treatment for ROP is Laser or Cryo-therapy.

The basis of both techniques is to destroy the avascular peripheral retina, and with it the aberrant VEGF signaling. This allows the core and most sensitive vision to persist without the risk of retinal detachment. Though, this technique does remove peripheral vision, it is often the best chance for preserving vision in late stage III+ infants. (Huu et al.)

 

Another emerging treatment for ROP is a class of VEGF inhibitors, which block the aberrant VEGF signal following oxygen level cycling.

Though these treatments have shown some promise, no large scale well controlled clinical trial has shown improved visual outcomes with VEGF inhibitors over the standard of care laser therapy (Mintz-Hittner et al.)

Further, following the anti-VEGF treatment the vascular pattern is atypical or incomplete once vascularization resumes. Differences in foveal architecture have also been noted following these treatments. (VanderVeen et al.)

 

Other treatments for the more severe stages of ROP,

Scleral Buckle: In stage IV or V ROP, where the retina has partially or fully detached, a silicone band is placed around the eye and tightened. This keeps the vitreous gel from tugging on the scar tissue and allows the retina to flatten back against the wall of the eye. It must be removed months to years after implantation to prevent permanently altering eye morphology.

Vitrectomy: Generally only performed on stage V afflicted infants. The vitreous of the eye is removed and replaced with saline, then the scar tissue can be removed allowing the remaining retina to relax back against the wall of the eye.

 

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Also See : Diabetic Retinopathy