Retinopathy of Prematurity

Description

A bilateral proliferative retinopathy affecting premature babies was originally described by Terry in the USA in 1942. It arises from the disruption of the anterior growth of the retinal vasculature in premature infants, normally complete at 32 weeks (nasal retina) to 40-42 weeks (temporal retina). Campbell in Australia in 1954 discovered a link between the onset of retinopathy of prematurity (ROP) and the administration of high levels of oxygen in incubators.  It was later found that other factors were also involved, including a short gestational age, typically less than 32 weeks and a birth weight of less than 1500 grams and especially if less than 1250 grams. Other risk factors include a multiple birth, hypercarbia, apnoea and intraventricular hemorrhage.

Classification And Signs

An international classification of ROP was published in 1984 and 1987. ROP is classified according to the location of involved retina (divided into three zones), the extent of retinal involvement in clock hours, the stage the disease has reached and other changes.

ROP is classified into five clinical stages:

1. Anterior retina is avascular, with a grey demarcation line seen most prominently in the temporal peripheral retina
2. A ridge of elevated tissue develops at the grey demarcation line
3. Extraretinal fibrovascular proliferation develops at the ridge. Both retinal and vitreous haemorrhages may occur
4. Tractional retinal detachment may commence in the far periphery. Stage 4A – the fovea is not involved; stage 4B if the fovea is involved
5. Total retinal detachment: stage 5A- open funnel, and stage 5B- closed funnel.

“Plus” disease indicates dilation of the retinal veins and tortuosity of the arteries and is recorded by adding a plus sign to the stage number. Zone 1 disease carries the poorest prognosis and refers to the posterior pole area seen with a 28-dioptre lens centered on the optic disc.

In a minority of patients, possible complications from scarring include amblyopia, myopia, strabismus, a dragging of the macula and optic disc, the development of a falciform retinal fold, retinal detachment and retrolental fibrovascular tissue (retrolental fibroplasia). This may lead to the appearance of a white pupil or leucocoria. A secondary angle-closure glaucoma may develop in these eyes. Rubeosis may also be present.

Prevalence

Over 500 cases of blindness from ROP are reported in the USA annually. In one report, over 50% of premature babies weighing less than 1250 grams had ROP.

Significance

Even though the majority of ROP cases show a spontaneous regression of signs, the disease may potentially cause severe bilateral vision loss if not blindness. The prognosis is usually guarded.

Differential  Diagnosis

Familial exudative vitreoretinopathy, Norrie’s disease. Other causes of leukocoria must be excluded including retinoblastoma, toxocara, persistent hyperplastic primary vitreous, congenital cataract, and Coats’ disease.

Management

Review

All at-risk babies should be regularly screened for signs of ROP, at perhaps six-month intervals, using a 28-diopter lens, speculum and scleral depression. At-risk babies include those born before 36 weeks, those that weighed less than 1500 grams at birth and those that have received oxygen.

Laser treatment

The application of laser photocoagulation via an indirect ophthalmoscope to the avascular retina may be considered in order to minimize the likelihood of retinal detachment. Cryotherapy may have more side-effects. If the disease is at stage 1 or 2 no treatment may be necessary, although it has also been suggested that ROP at any stage involving zone 1 should be treated.

Incisional surgery

In stages 4 and 5, scleral buckling and/or vitrectomy surgery may be successful, however the prognosis for the retention of useful vision is poor.

Refractive correction or low vision aids

Partially sighted children may need low vision and other rehabilitation services.

Oral medication

The use of vitamin E dietary supplementation is controversial.