An analysis of the role of vision anomalies in reading interference.

Several reviews of the literature have shown a relation between vision anomalies and reading problems. The studies have been correlational - comparative in nature and thus have not established causal relations. This paper suggests that before experimental studies are conducted to establish causation, studies of the process by which vision anomalies produce reading interference need to be conducted. The paper discusses the factors to consider in studying vision and reading interference. The factors are: nature of the vision anomaly, type and severity of symptoms produced, type of reading interference (perceptual or functional deficiency), amount and type of near task demands, reading skill, and reading development stage.

Vision anomalies and reading skill: a meta-analysis of the literature.

We report a meta-analysis of studies of the relation of vision anomalies to reading skill. Meta-analysis is a quantitative technique for combining the results of multiple studies that reduces the subjectivity of literature reviews. The results of the analysis of 34 studies of vision anomalies and reading skill that met the criteria for inclusion in the meta-analysis showed that hyperopia, exophoria at near, vertical phoria, anisometropia, and aniseikonia are associated with below average reading performance. Myopia and esophoria and esophoria at far are associated with average and above average reading performance. Reduced visual acuity, astigmatism, esophoria at near, fusional convergence and divergence, strabismus, nearpoint of convergence, and stereopsis were not found to be associated with reading performance.

The reading process and learning to read.

This paper provides a description of two models of the reading process and the relation of these models to learning to read, reading instruction and the identification and treatment of reading problems.

Binocular anomalies and reading problems.

This paper reviews and evaluates the research literature on the relationship of binocular anomalies to reading problems. The weight of the evidence supports a positive relationship between certain binocular anomalies and reading problems. The evidence is positive for exophoria at near, fusional vergence reserves, aniseikonia, anisometropia, convergence insufficiency, and fixation disparity. There is some weak positive evidence for esophoria at near and mixed evidence for stereopsis. The evidence on lateral phorias at distance is negative.

Refractive error and the reading process: a literature analysis.

The literature analysis of refractive error and reading performance includes only those studies which adhere to the rudaments of scientific investigation. The relative strengths and weaknesses of each study are described and conclusions are drawn where possible. Hyperopia and anisometropia appear to be related to poor reading progress and their correction seems to result in improved performance. Reduced distance visual acuity and myopia are not generally associated with reading difficulties. There is little evidence relating astigmatism and reading, but studies have not been adequately designed to draw conclusions. Implications for school vision screening are discussed.

Vision and reading disability: research problems.

This paper reviews and analyzes the methodological problems of the studies of the relationship of vision and reading disability. Procedures that lead to false positive and false negative findings are discussed. False positive findings can be due to problems in subject selection procedures and criteria, failure to take into account correction of vision problems, use of unselected comparison groups, using unskilled testers, small sample size, and data analysis problems. False negative findings can be due to experimenter expectations, lack of a comparison group, statistical tests and use of clinical samples and failure to rule out competing explanations.