S. P. Taylor

Further studies of the Café Wall and Hollow Squares illusions.

The effect of varying the contrast on the apparent convergence is measured for both the Café Wall and the Hollow Squares (Taylor—Woodhouse) illusions. The apparent convergence is dependent on the contrast, and also on the size of the stimulus, and varies in the same way for both illusions. This strengthens the argument that the illusions are not independent, as Taylor and Woodhouse originally claimed. McCourt has discussed brightness induction as a basis of the Café Wall illusion. Consideration of this theory leads to some interesting examples of interactions of the two illusions, and to a further, very strong, variation of the illusion in a real-life situation.

Clinical evaluation of the Humphrey auto refractor

A study is made of the accuracy and repeatability of the Humphrey autorefractor (HAR) objective refraction for different refractive groups as measured against subjective refraction. The value of the autofogging mechanism in objective refraction for different refractive groupings is assessed.

THE X‐CHROM LENS–A CASE STUDY

Abstract A deuteranomalous male was filled with an X‐chrom tens in his non‐Dominant eye. The effect of wearing this lens on subsequent colour Vision classification as shown by a number of different test is described.

A New Illusion and Possible Links with the Münsterberg and Fraser Illusions of Direction

In the course of an investigation of the Münsterberg illusion, a new illusion has been produced. The illusion is reduced to its simplest form and possible links to the original Münsterberg and Fraser illusions are suggested.

The effect of reduced viewing time on colour vision in normal subjects and those with abnormal ocular conditions

Abstract The effect of restricting viewing time to 3.75 ms in normal subjects is to produce a tritan‐like colour response on the City University colour vision test. This response pattern is consistent and is repeatable for standard illuminant C at 600 Ix. Supplementary tests suggest that the effect is due to a defect of the blue/yellow opponent system rather than a true tritan defect. The same test when repeated on subjects with amblyopia or retinal pathology provides different results which may aid in the differential diagnosis of some visual disorders.

The effect of restricted viewing time on the performance of colour defectives using the City University Colour Vision Test.

Abstract The effect of restricting viewing time to 3.75 ms on the performance of so en red/green colour defectives is studied using the City University Colour Vision Test. One further subject who was screened as colour‐defective but not classified on the City plates was studied in she same way and results for the subject are presented separately. The results arc compared to those for normal observers who exhibit a tritan‐classified defect when viewing time is restricted to 3.75 ms.

Preliminary assessment of the Dex Frame for assisting children with specific learning difficulties

A device called the Des Frame has recently been marketed as an aid for children with specific learning difficulties. Using a test of reading speed and a test of reading accuracy we have attempted to evaluate the device. Two groups of children with learning difficulties were used, one having sole use of the device and being allowed to carry it with them and a second group who only used the device when attending for remedial tuition and assessment. The results show that no significant improvement occurred in reading performance of the groups with learning difficulties using the Dex Frame as compared with a control group. The teachers of the groups did, however, feel that on an individual basis some children (< 10%) expressed that they felt more comfortable using the device.