Learning to see after early and extended blindness: A scoping review

Abstract

Purpose: If an individual has been blind since birth due to a treatable eye condition, ocular treatment is urgent. Even a brief period of visual deprivation can alter the development of the visual system. The goal of our structured scoping review was to understand how we might better support children with delayed access to ocular treatment for blinding conditions.

Method: We searched MEDLINE, Embase and Global Health for peer-reviewed publications that described the impact of early (within the first year) and extended (lasting at least 2 years) bilateral visual deprivation.

Results: Of 551 reports independently screened by two authors, 42 studies met our inclusion criteria. Synthesizing extracted data revealed several trends. The data suggests persistent deficits in visual acuity, contrast sensitivity, global motion, and visual-motor integration, and suspected concerns for understanding complex objects and faces. There is evidence for resilience in color perception, understanding of simple shapes, discriminating between a face and non-face, and the perception of biological motion. There is currently insufficient data about specific (re)habilitation strategies to update low vision services, but there are several insights to guide future research in this domain.

Conclusion: This summary will help guide the research and services provision to help children learn to see after early and extended blindness.

Keywords: access to health; childhood cataract; deprivation amblyopia; early blindness; neurorehabilitation.

Figure 1

PRISMA flow diagram [papers linked by study: (Umezu, ; Umezu et al., 1990, 1991) and (Mochizuki, 1976, 1977, 1979)].

Figure 2

Characteristics of publications. The timeline shows each publication linked to the (logarithmic) timeline by a dotted line. Each vertex represents an author, and co-authorship is represented with solid gray lines. This network analysis highlights collaborative research teams. Each research team with 2 or more publications is assigned a letter [(A–D), label color reflects country of institute with which the corresponding author affiliates]. Publications are represented with a dot, connected to each contributing author, the size of which represents the number of participants, and the color represents the country of the majority of the participants. The summary (lower left) shows number of publications by country; the outer ring shows country of institute with which the corresponding author is affiliated, and the inner pie shows the corresponding country of the majority of sight recovery participants for each study. Colors assigned to country are consistent across pie chart summary and network analysis timeline, as highlighted by country codes in the legend.

Figure 3

Characteristics of participants. In the (left-most) column “study details” we highlight the research group (based on those highlighted in Figure 2), the visual ability focused on, as well as the number of participants and percent female. In the second column “visual deprivation,” we include the range for each study of duration of visual deprivation, from 2 years (inclusion criteria) or minimum from study to the maximum for study. The third column “recovery time” displays time between ocular treatment and participation in the research project. Darker shaded bars indicate the study noted changes over time. The fourth (right-most) column “Post-treatment VA” shows the range of estimated VA outcomes for participants (in some cases notation was inferred before conversion, so logMAR values are estimates only). The darker shaded region is the estimated pre-surgical acuity across studies. NR, Not reported; VA, Visual Acuity; ^*only a subset of participants met our criteria, but analysis (excluding duration, recovery time, and VA presented here and in Figure 4) included all participants.

Figure 4

Extent of visual deprivation. In the left and middle subplots, VA is plotted against years of visual deprivation and years of visual experience (between ocular treatment and assessment), respectively.

Figure 5

Visual abilities overview. The (left) column breaks down visual skills discussed across the review. The (middle) column zeros in on the subset of visual abilities which were compared to a control group (after the first 6 months of sight recovery). Of the visual skills compared to controls, the right column categorizes them as “Typical” (reported within variability of control group) or “Atypical” (reported outside variability of control group) for each specific task. In the (right) panel, dot size represents the number of participants (meeting our inclusion criteria) for each visual skill assessed. sCSF, spatial contrast sensitivity function; tCSF, temporal contrast sensitive function.

Figure 6

Expected outcome summary. The (left) column includes all visual skills suspected to be typical after visual deprivation. The bubbles on the left of each subplot highlight the number of studies which discussed this skill across all study types, the bubbles on the right of each subplot highlight the number of studies which compared this skill to a control group. Visual skills which have been discussed in the literature, but not compared to a control group are bolded, and those which are suspected to be atypical and are likely in need of more research are highlighted with a shaded bar. Only visual skills which remain relevant more than 6 months after the ocular treatment are included (e.g., Molyneux's question is excluded). sCSF, spatial contrast sensitivity function; tCSF, temporal contrast sensitive function.