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Chapter 3: The prevalence of delayed visual maturation

This chapter looks at the use of a vision screening assessment for infants born to substance misusing mothers.

Method

Vision screening was discussed by the Study Nurse with the family health visitor at the time of initial contact. The health visitor was provided with the protocol, equipment and completed the data forms. Training for the health visitor was arranged at the first joint home visit.

The vision screen was developed in consultation with the specialist pre-school functional vision assessment team, based at the Raeden Regional Child Development Centre (Raeden Centre Assessment Charts, revised 2000). The criteria were developed from several sources and used principles of functional visual assessment (The Oregon Project, 1991; Orr, 1999; Sonksen et al, 1991, 1995; Sheridan, 1997). The study required three observations or simple tests at each assessment as shown on the form ( Appendix 2). The equipment used was a standardised plastic ball and small brightly coloured sweets ("Smarties"). The introduction of the assessment in the community did not involve great expenditure as the skills required were already within the training and expertise of health visitors. Any additional training was in regard to the precise application of the structured tests, the vision screening and the NAS screening i.e . this was a low cost health visitor intervention.

As vision development is related to gestational maturity, the date of assessment was corrected for preterm birth. Infants were therefore assessed at 2, 4, 8, 12, and 24 weeks from the expected date of delivery.

If any of the three visual tasks on each assessment was not achieved, the infant was seen within one week at the hospital follow up clinic. The vision screen was repeated, the eyes examined and a full neurodevelopmental examination undertaken. Infants with eye problems were referred to the paediatric eye clinic for confirmation of the diagnosis.

Results

Infants were screened by the health visitors using the vision assessment (but may not have undergone all three tests). The number and timing of the failed tests is as shown in Table 4 below. The number not assessed at each stage is small.

Table 4: Vision tests and fails by age of infant

19 of the 72 recruited infants were seen in the hospital follow up clinic because of failed vision screening (26.4%)

• 14 failed once
• 4 failed twice
• 1 failed four screens (one of which was at either 2 or 4 weeks)

8 infants (8/72) were referred to the eye clinic where the following diagnoses were confirmed:

• 3 nystagmus
• 4 squints
• 1 coloboma

Summary

• The health visitor aimed to complete the vision screen test on the 72 infants recruited to the study at 2, 4, 8, 12 and 24 weeks following expected date of delivery (a small number were not assessed).
• 19 of the 72 infants were referred to the hospital outpatient clinic because they failed the test, and 8 of these were diagnosed with eye problems (nystagmus, squint or coloboma).

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