Premature baby mothers should know: fundus screening

Author: Peng Chunxia, ​​deputy chief physician, Beijing Children's Hospital, Capital Medical University

Reviewer: Li Li, Chief Physician, Beijing Children's Hospital, Capital Medical University

Retinopathy of prematurity

Retinopathy of prematurity (ROP) is a neovascular proliferative retinopathy caused by premature birth and oxygen inhalation, which interrupts the normalization of retinal blood vessels, followed by hypoxic damage after oxygen inhalation stops, which stimulates abnormal proliferation of retinal blood vessels. ROP is a treatable blinding eye disease, but the treatment window is very short and requires close observation of the fundus. It is currently the leading cause of blindness in children in developed countries.

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The occurrence of retinopathy of prematurity

Normal Vascularization: The sequence of ocular vascularization is critical to understanding the mechanisms of ROP. The retina is avascular until approximately 16 weeks of gestation. Between 15 and 18 weeks of gestation, the retina begins to vascularize. Blood vessels emerge from the optic disc (where the optic nerve enters the eye) and grow toward the periphery. Vascularization is complete on the nasal side of the retina by approximately 36 weeks of gestation. By 40 weeks of gestation, the temporal side of the retina is usually fully vascularized.

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Onset of ROP: The retinal blood vessels of premature infants have not developed to the periphery of the retina. Because the organs of premature infants are not fully developed, they need oxygen support therapy. The inhalation of high-concentration oxygen inhibits the normal development of retinal blood vessels. As the general condition improves, oxygen inhalation is stopped, and the ischemia of the unvascularized retina stimulates abnormal retinal vascularization, causing the occurrence of ROP. In severe cases, blindness may occur if no interventional treatment is given.

What kind of premature babies need fundus screening?

The Chinese Clinical Guidelines for Retinopathy of Prematurity (2014 Edition) state: ① Perform ophthalmological screening on premature infants and low-birth-weight infants with a birth weight of less than 2000g or a gestational age of less than 32 weeks; ② Perform ophthalmological screening on patients with severe illness or a clear history of prolonged oxygen inhalation who are considered to be at higher risk by pediatricians.

When should fundus screening be performed?

The Chinese Clinical Guidelines for Retinopathy of Prematurity (2014 Edition) state that the first examination should begin 4 to 6 weeks after birth or at 31 to 32 weeks of corrected gestational age.

Conditions for termination of examination: Follow-up can be terminated if one of the following conditions is met: ① The retinal vascularization has reached the ora serrata on the nasal side and is 1 optic disc diameter away from the ora serrata on the temporal side; ② The corrected gestational age is 45 weeks, there is no pre-threshold lesion or threshold lesion, and the retinal blood vessels have developed to zone III; ③ The retinal lesions are regressed.

American Academy of Pediatrics criteria: Screening begins at 30 weeks’ corrected gestational age (PMA) and 4 weeks’ chronological age for infants born at 22 to 26 weeks’ gestational age and ≥27 weeks’ gestational age, respectively. Although treatable ROP rarely occurs before 31 weeks’ PMA, we begin screening at 30 weeks’ PMA to account for the possibility of scheduling errors and delays due to medical conditions, as well as to allow for scheduling flexibility. Repeat screening every 1 to 3 weeks until retinal vessels have fully grown to the ora serrata (peripheral retina). If ROP develops, screening should be more frequent, depending on the severity and rate of progression of the disease.

For infants who are discharged home before their retinal vessels mature, parents must understand the importance of timely follow-up.

Under what circumstances does retinopathy of prematurity require treatment?

Pre-threshold and aggressive ROP requires interventional treatment.

Threshold ROP used to refer to the threshold for treatment, but now treatment is initiated when infants have high-risk pre-threshold ROP (also called type I ROP). The following are all considered type I ROP:

● Any stage of ROP in zone I with additional lesions.

●Stage 3 ROP in zone I without additional lesions.

●Stage 2 or 3 ROP in zone II with additional lesions.

In some cases, it may be reasonable to treat the eye that does not meet the criteria for Type I ROP. For example, if one eye has Type I or worse ROP and is being treated, and the other eye has active ROP but does not meet the criteria for Type I ROP, both eyes may be treated simultaneously, particularly if there are significant or persistent changes in the less severely affected eye. This decision must be made on an individual basis.

Telemedicine screening

Telemedicine systems can be used to identify infants with potentially severe ROP. This requires the use of wide-angle digital fundus photography to create digital retinal images. Up to six standardized images are taken. The images are then transmitted remotely for interpretation. Initially, telemedicine was used to provide remote screening in remote areas where ophthalmologists with ROP screening skills were not available, but today telemedicine is increasingly being used as the primary screening modality even in areas where such ophthalmologists are available. When using telemedicine screening methods, the AAP/AAO/AAPOS/AACO joint statement recommends that the same protocols as for ophthalmoscopy screening (see above) be followed and that infants at risk should have at least one indirect ophthalmoscopy performed by a qualified ophthalmologist before initiating treatment or discontinuing screening.

Prognosis

After standardized screening and timely treatment, most children have normal vision. Among them, 7% to 15% of children with moderate to severe ROP will have long-term visual impairment, and children with severe ROP (stage 3 and above) are at the greatest risk. Children with ROP in zone III only rarely experience decreased vision.

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References

Chiang MF, Quinn GE, Fielder AR, et al. International Classification of Retinopathy of Prematurity, Third Edition[J]. Ophthalmology, 2021: S0161-6420(21)00416-4.

Fundus Disease Group of the Ophthalmology Branch of the Chinese Medical Association. Clinical Guidelines for Retinopathy of Prematurity (2014)[J]. Chinese Journal of Ophthalmology, 2014, 50(12): 933-935.

Update: Retinopathy of prematurity: treatment and prognosis, updated on 2021-4-21.

Update: Pathogenesis, epidemiology, classification and screening of retinopathy of prematurity, updated on 2020-1-2.