小田 浩一

Patients with central serous chorioretinopathy (CSC) often complain of visual difficulties under low luminance conditions. In this study, we evaluated low luminance visual acuity (LLVA) after half-dose verteporfin photodynamic therapy (hdPDT) in eyes with CSC. The study included eight eyes of eight patients with chronic CSC that underwent hdPDT. The best-corrected visual acuity, LLVA and optical coherence tomography (OCT) findings were evaluated at baseline, and at 1, 3, 6, 9, and 12 months after hdPDT. LLVA was measured at six levels of background luminance. Serous retinal detachment was completely resolved in all eyes. Although the mean LLVA at 1 month did not improve significantly compared to baseline at all luminance levels, significant improvements were observed at 3, 6, 9, and 12 months (p < 0.05). In OCT images, although the ellipsoid zone was not detectable in all eyes before hdPDT, it was observed in 2 eyes at 1 month, in 7 eyes at 3 months, and in all eyes from 6 months. The LLVA and the ellipsoid zone improved similarly with postoperative time courses. In conclusion, hdPDT improves LLVA in eyes with chronic CSC. The recovery of the ellipsoid zone may play a part in improving LLVA after hdPDT.

This study examined the effect of character sample density on legibility. As the spatial frequency component important for character recognition is said to be 1 to 3 cycles/letter (cpl), six dots in each direction should be sufficient to represent a character; however, some studies have reported that high-density characters are more legible. Considering that these seemingly contradictory findings could be compatible, we analyzed the frequency component of the character stimulus with adjusted sample density and found that the component content of 1 to 3 cpl increased in the high-density character. In the following three psychophysical experiments, high sample density characters tended to have lower contrast thresholds, both for normal and low vision. Furthermore, the contrast threshold with characters of each sample density was predicted from the amplitude of the 1 to 3 cpl component. Thus, while increasing the sample density improves legibility, adding a high frequency is not important in itself. The findings suggest that enhancing the frequency components important for recognizing characters by adding the high-frequency component contributes to making characters more legible.

<p>This study aims to explain as quantitatively as possible the readability of Japanese characters in terms of certain elements in the multi-dimensional, and rather qualitative, space of font design. Based on a review of previous studies, two main dimensions have been selected as the most influential on readability ; the relative character size in the bounding box, which we call style, and the stroke width, which we call weight (when discussed in a categorical way). The Gothic fonts were chosen as the target because they are well known to be the most legible. Behavioral evaluations of readability were conducted instead of subjective judgments. In accordance with the reading acuity measurement MNREAD-J, short and easy-to-read sentences were presented to participants, and the time required to read them aloud was recorded along with any reading errors ; this provided three readability indices. Sentences were rendered in one of 12 different fonts consisting of four kinds of style-Old, Standard, Modern, and UD-times three weight levels-Light, Regular, and Bold. Findings for the style suggest that the enlargement of relative size represents a tradeoff with narrowed inter-letter spacing. This means that good legibility of single letter design may not result in good readability of letters in sentences. However, the weight had a notable effect especially in small sizes. Two readability indices were predicted relatively well by participants' acuity and stroke width. The effect of stroke width had a ceiling between 10 and 15 ％ of the letter size.</p>

フリークライミングは視覚障害者にも適したスポーツであり，教育的利用価値があるスポーツと言える。著者らは2008年より筑波技術大学の視覚障害学生を対象とした体育集中授業として導入された「フリークライミング」の授業指導を行ってきた。ここでは視覚障害に配慮した上で，登るという身体的な技術指導のみならずパートナーシップや自己責任などに着目した心理的効果を引き出す独自のプログラムを実施した。本研究の目的はこのプログラムの有用性を検証することである。2010年度の受講生9名（男性5名，女性4名，弱視9名）を対象に，フリークライミング（以下，クライミングと略す）の体験過程と前後での変化を調べるため自己効力感尺度，自由記述式質問紙，インタビュー，ビデオ分析を行い，総合的に考察を試みた。その結果，クライミングを活用した体育カリキュラムの有用性が示された。

遠方に提示される大型電子化提示教材の文字サイズを臨界文字サイズで規定する可能性を明らかにするため、シミュレーションによる実験1とロービジョン者による実験2を行った。実験1は、文字サイズ(3水準)と読書形態(2水準)を要因とする2要因の要因計画法であった。ロービジョンシミュレーションの実験結果から、臨界文字サイズ未満と以上の間で読書速度に有意差がみられたことと、読書評価テストと実験結果の間に相関がみられたことから、臨界文字サイズは大型電子化提示教材の文字サイズの推定に利用できることが示唆された。実験2の結果は、実験1と同様の結果がみられるケースと、そうでないケースの存在が明らかになった。実際にロービジョン者の文字サイズを推定する場合は、臨界文字サイズを基準にし、あわせて内省報告を重視する必要性があることが明らかになった。

An interesting field of basic research in psychology of sensation and perception named "psychophysics of reading" developed in the process of solving problems practitioners have been facing in the fields of special education and rehabilitation for persons with visual impairments. Psychophysical study of relationship between stimulus dimensions, such as spatial resolution, contrast, and visual field size and reading speed gave us basic understanding about our reading behavior as well as a good tool to help persons with visual impairments find suitable aids and environmental modification in order to ease their reading difficulty. Especially the reading speed function of print size for each patient gives us a very sensitive measure about patient's quality of vision. As an example, one of our recent findings showed that the reading function explained the claim of degraded vision from a patient with ring scotoma better than usual visual acuity measure.

加齢黄斑変性のロービジョン患者に対し文字を拡大するためのロービジョンエイド(以下エイドとする)の処方方法として、MNREAD-Jでの読書評価を基準にエイドの倍率を予測し行う方法と、従来行われている視力を基準にエイドの倍率を予測し行う方法とを比較し、エイドの処方としてどちらが有効かを検討したのでその結果を報告する。<br>対象は、新聞を読むためのエイドを処方した両眼性滲出型加齢黄斑変性の瘢痕期のロービジョンの患者19名であった。MNREAD-Jでの読書評価を基準に行う方法では、測定された臨界文字サイズと新聞の文字サイズの比を基にエイドの倍率を予測した。視力を基準に行う方法では、新聞を読むために必要な視力を0.4とし、これと患者の視力の比を求めてエイドの倍率を予測した。<br>視力から予測した倍率は、全例で、最終的に処方された倍率より低い値を示した。回帰直線を求めると、視力から予測した倍率は実際の処方倍率の4分の1程度しかないのに対し、臨界文字サイズから予測した倍率は、処方倍率とほぼ一致することが分かった。さらに、MNREAD-Jによる初期評価で測定された最大読書速度を使うとエイドの処方の妥当性を客観的に評価することができた。<br>加齢黄斑変性によるロービジョンでは、エイドの処方方法として、MNREAD-Jを用いて読書を直接測定し、臨界文字サイズを基準に倍率を予測し処方を行う方法が、視力を基準にする従来の方法よりも、より正確・客観的な方法であるといえる。