Evaluation and Analysis of Visual Function in ROP (Retinopathy of Prematurity)

The Visual Hand Display: A Focus on Collaboration

When young children experience subnormal vision, an array of evaluation tools and techniques is used to assess visual function. Some children who have retinopathy of prematurity may require surgery. Post-operatively, at the Children's Low Vision Center in Boston, the pediatric ophthalmologist evaluates the child's visual functioning using a variety of devices. A tool called the Visual Hand Display has been introduced to enhance the physician's methods of evaluation, thereby achieving greater understanding of the child's visual responses. Collaborations among the doctors, educators, therapists, and patients are emphasized.

The pattern visual-evoked potential in former preterm infants with retinopathy of prematurity

PURPOSE

Flash and pattern visual-evoked potentials (VEPs) were recorded in 89 former preterm infants (< or = 1500 g birth weight), in whom retinopathy of prematurity (ROP) developed that spontaneously regressed without macular detachment (stages 2-4a).

METHODS

Linear and stepwise regression analyses were performed to determine the correlations between transient pattern-reversal P1 VEP latency (n = 154 eyes) at a mean of 7.2 years (median, 6.9 years) postnatal age using a check size nominally equivalent to 20/100 (30 minutes) and the following nine parameters: three immaturity parameters (gestational age at birth, birth weight, and ROP zone at 1 month postnatal age); one postnatal insults parameter (worst ROP stage); two structural outcome parameters (macular ectopia and vessel traction); one functional outcome parameter (visual acuity); and two methodological parameters (postnatal age at VEP testing and VEP amplitude).

RESULTS

Linear regression analyses, with P1 VEP latency as a dependent variable, identified the worst ROP stage (r = +0.42; P < 0.0001), macular ectopia (r = +0.42; P < 0.0001), visual acuity (r = -0.40; P < 0.0001), and vessel traction (r = +0.35; P < 0.0001) as significant correlates. Stepwise regression analysis demonstrated that worst ROP stage and macular ectopia accounted for 18% and 4% of the cumulative variance, respectively.

CONCLUSIONS

P1 VEP latency correlates with postnatal insults, structural outcome, and functional outcome parameters in former preterms in whom ROP developed that spontaneously regressed without macular detachment. A permanent arrest in the development of the macula and/or prolonged traction on the incompletely developed macula may alter VEPs.

VEP acuity, FPL acuity, and visual behavior of visually impaired children

Forced-choice preferential-looking (FPL) and pattern-visual-evoked potential (VEP) acuity tests were conducted with 42 children with bilateral moderate to severe visual impairment (age, 4 months to 9 years). Within this group of children, FPL acuity testing was more successful than VEP acuity testing (98% versus 64%). Mean FPL acuity was better than mean VEP acuity (20/155 vs 20/290, P less than .002). For the children who completed both FPL and VEP acuity tests, an acuity difference score (FPL minus VEP) was derived, and compared to difference scores based on normative data. Significant differences were found between visually impaired (VI) and control difference scores (P less than .001). Difference scores of VI were larger than and opposite in sign to the control scores. Rating scores of visual behaviors supported the concurrent validity of the FPL acuities (P = .01), but not the VEP acuities.

Measurement of low vision in children and infants

The authors evaluated a preferential looking technique (Teller acuity cards) and a set of gross behavioral indicators (visual function battery) for the ability to rank visually impaired children and infants on the basis of their visual function. Fourteen older children with a diagnosis of cicatricial retinopathy of prematurity who were capable of giving Snellen acuities and a group of 31 preverbal infants with decreased vision due to a variety of causes were tested. Teller acuity card and visual function battery findings were highly correlated with each other (and with Snellen acuities in the older group); however, the Teller acuity cards provided better discrimination in the moderately visually impaired range, whereas the visual function battery was better in the severely impaired range. It is concluded that, in children and infants, visual function over the entire spectrum of low vision can be characterized by using a combination of the Teller acuity cards and the visual function battery.