Important feature identification for perceptual sex of point-light walkers using supervised machine learning.

The present study aimed to elucidate the dynamic features that are highly predictive in the biological and perceptual sex classification of point-light walkers (PLWs) and how these features behave in sex classification using supervised machine learning. Fifteen observers judged the sex of 21 PLWs from a side view. A fast Fourier transform was applied to retrieve the spectral components from the multiphasic hip and shoulder movements. An exhaustive search identified the most important features for biological and perceptual sex classifications. An individual conditional expectation (ICE) with a support vector machine (SVM) model was used to interpret the behavior of each important feature. The observers judged the biological sex from side-view PLWs with an accuracy of 62.9% for 10 male PLWs and of 57.0% for 11 female PLWs. The SVM model for biological sex prediction demonstrated that the third harmonic of hip motion played a dominant role in achieving a high predictive accuracy of 90.5% with few feature interactions. In the model of perceptual sex prediction, however, an accurate prediction of 85.7% was achieved using five spectral components of hip and shoulder motions, where the ICE plots of the features followed heterogeneous courses, suggesting feature interactions. The machine learning model suggests that biological sex classification depends mainly on local cues of the PLW. However, the high-performance model of perceptual sex classification involves interactions of various frequency components of hip and shoulder motions, suggesting more complex processes in sex perception.

The effect of character stroke width on legibility: The relationship between duty ratio and contrast threshold.

Stroke width is an important factor affecting letter legibility. Although there seems to be a critical or optimal value for stroke width, it has been difficult to estimate quantitatively because shape deterioration and the increase of stroke width are covariates. This study attempted to predict the optimal value of stroke width considering it as a duty ratio. The duty ratio is related to the amplitude of the fundamental frequency, with the maximum amplitude of the fundamental frequency occurring at a duty ratio of 0.5. The fundamental frequency decreases when the duty ratio is set either lower or higher than 0.5. Based on previous research indicating that letters also have a critical band (CB), or the frequency band which contributes most to letter recognition, which corresponds to their fundamental frequency, we hypothesized that the amplitude of CB is related to the legibility of letters. We measured the contrast thresholds using square-wave gratings and letters of differing duty ratios. In both the grating and letter stimuli, the amplitude of CB reached its maximum when the duty ratio was around 0.5. Contrast thresholds for stimuli with various duty ratios were accurately predicted by the amplitudes of CB and the contrast thresholds in the individual's sine-wave grating. Our results suggest that the amplitude of a single critical component contributes significantly to the legibility of letters, even though they contain diverse frequency components.

Improvement of Low Luminance Visual Acuity in Patients with Chronic Central Serous Chorioretinopathy after Half-Dose Verteporfin Photodynamic Therapy.

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.

Unresolvable Pixels Contribute to Character Legibility: Another Reason Why High-Resolution Images Appear Clearer.

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.

Effects of luminance contrast and character size on reading speed.

Both luminance contrast and character size are critical factors affecting reading performance. Previous studies reported on the effect of luminance contrast on the reading-speed function, that is, the relationship between reading speed and character size. In particular, when contrast was reduced, the critical print size (CPS) was found to shift to a larger character size even though the maximum reading speed and function shape did not change [Japanese Journal of Ophthalmology 52(1) (2008) 44-47]. In the present study, the effect of luminance contrast on the reading function was quantitatively examined. Japanese phrases with a luminance contrast of 0.03-0.99 were prepared as stimuli. Observers with normal vision were asked to read aloud phrases with several character sizes. Then, the reading functions were obtained for each luminance contrast. CPS was found to increase as the luminance contrast decreased. The relationship between contrast and CPS was linear in log-log coordinates, that is, log-CPS increased as the log-contrast of the characters decreased. It was found that the contrast of the stimulus systematically affects the location of the reading function.

Low luminance visual acuity in patients with central serous chorioretinopathy.

BACKGROUND: The aim was to determine the low luminance visual acuity in eyes with central serous chorioretinopathy. METHODS: Seven eyes of seven patients with central serous chorioretinopathy and six eyes of six age-matched normal volunteers were examined. Low luminance visual acuity charts were created by an Apple Power Mac G5 computer and displayed on a cathode ray tube monitor (SONY GDM-F500). The background luminance was set at six different levels from 78.20 cd/m(2) to 0.37 cd/m(2). The visual acuities of the eyes with central serous chorioretinopathy at each of the six luminance levels were compared to those from their fellow eyes and to normal eyes. RESULTS: The mean visual acuities varied from 0.13, 0.23, 0.29, 0.42, 0.62 to 0.70 logMAR units as luminance varied from high to low. At the lowest luminance (0.37 cd/m(2)), five of the seven eyes could not read any character. The mean visual acuities of the fellow eyes at the same luminance levels were 0.03, 0.06, 0.11, 0.20, 0.27 and 0.45 logMAR units and those of the normal volunteers were 0, 0.03, 0.08, 0.14, 0.23 and 0.38 logMAR units, respectively. The visual acuities of the eyes with central serous chorioretinopathy were significantly poorer than those of the normal eyes at all luminance levels except 0.37 cd/m(2) (p < 0.05 for all). CONCLUSIONS: Although the eyes from all three groups had 0 logMAR units visual acuity under standard testing condition, the visual acuity of the eyes with central serous chorioretinopathy were significantly worse at low luminance levels. The low luminance visual acuity may provide information on the visual disturbances reported by central serous chorioretinopathy patients with 0 logMAR units visual acuity.

How normal eyes perform in reading low-contrast texts.

PURPOSE: To assess the performance of normal eyes in reading low-contrast texts. METHODS: We selected 14 subjects aged 20 to 31 years (mean, 23 +/- 3 years) with corrected visual acuity of 1.0 or better. The subjects were asked to read texts when the contrast between the characters and background was adjusted to 100%, 40%, 20%, and 10%. Using a computer-generated reading chart, reading acuity (RA), critical character size (CCS), and maximum reading speed (MRS) were assessed. The reading performance was compared at various contrast levels. RESULTS: When the contrast between the characters and background was 100%, 40%, 20%, and 10%, the mean RA (logMAR) was -0.08 +/- 0.07, 0.03 +/- 0.09, 0.13 +/- 0.09, and 0.26 +/- 0.11, respectively; the mean CCS (logMAR) was respectively 0.10 +/- 0.09, 0.18 +/- 0.09, 0.29 +/- 0.14, and 0.41 +/- 0.10. The mean MRS (characters/min) was 379.2 +/- 41.9, 369.7 +/- 43.3, 369.2 +/- 60.2, and 343.7 +/- 67.0, respectively. In all subjects, a decrease in contrast was associated with an increase in RA and CCS, but the MRS was not affected. CONCLUSIONS: In normal eyes, even when reading low-contrast texts, increasing the character size makes it possible to maintain the same MRS as when reading high-contrast texts.

Effect of learning on listening to ultra-fast synthesized speech.

A text-to-speech synthesizer that would produce easily understandable voices at very fast speaking rates is expected to help persons with visual disability to acquire information effectively with screen reading softwares. We investigated the intelligibility of Japanese text-to-speech systems at fast speaking rates, using four-digit random numbers as the vocabulary of the recall test. We also studied the fast and intelligible text-to-speech engine, using HMM-based synthesizer with the corpus with fast speaking rate. As the results, the statistical models trained with the fast speaking corpus was effective. The learning effect was significant in the early stage of the trials and the effect sustained for several weeks.

How spatial orientation of Japanese text affects fixation points in patients with bilateral macular atrophy.

PURPOSE: To ascertain the retinal area used by patients with bilateral macular atrophy when reading Japanese text of different character sizes written horizontally or vertically. In addition, to determine fixation points as part of the first of a series of studies designed ultimately to enhance the quality of life of these patients through the improvement of reading acuity. METHODS: Seventeen patients (34 eyes) with bilateral macular atrophy were tested to determine the retinal area employed for reading (R fixation point). Sentences were arranged either horizontally or vertically and projected onto the retina using a scanning laser ophthalmoscope. We also determined the fixation point using microperimetry (M fixation point). The positional relationships between these two fixation points and the scotoma were examined. RESULTS: The R and M fixation points were the same in 20 of the 34 eyes. Multiple R fixation points were found in 11 eyes. The R fixation point was frequently positioned above the lesion when reading horizontally (nine eyes), while it was often positioned in the area nasal to (eight eyes) or temporal to (six eyes) the lesion when reading vertically. CONCLUSIONS: Fixation points changed frequently in these patients with bilateral macular atrophy depending on the spatial orientation of the text. These data should be used in the future to help patients learn how to use the preferred retinal locus to improve their reading skills and enhance their quality of life.

[A case report illustrating the effectiveness of reading performance assessments in the diagnosis and treatment of psychogenic visual disturbances].

PURPOSE: An optimal strategy for treating psychogenic visual disturbances in adults has not been established. We report a patient with psychogenic visual disturbances who recovered his visual acuity and showed an improvement in his reading performance after undergoing training based on a reading performance assessment. CASE: A 37-year-old man who had been diagnosed as having myopic macular degeneration was referred to our clinic. Three months after his initial diagnosis, no changes in his fundi were observed, but his visual acuity had significantly decreased and his peripheral field of vision had become severely restricted. In view of his tunnel vision, the discrepancy among the visual acuity results obtained by different test methods, the results of a reading assessment, objective eye examination data, and his behavioral patterns, we diagnosed a psychogenic visual disturbance in the patient and referred him to an ophthalmologist and a psychiatrist for follow-up care. In our low vision clinic, we assessed his visual function, including reading performance, and developed a training program including reading, writing, and computer skills. We also provided information to help the patient find a job. The training program included instructions on how to manipulate reading aids and how to select reading materials to maximize his vision; these instructions were effective. Nine months after his rapid decrease in visual acuity, the results of his visual function tests showed an improvement. The patient also became motivated to find a job. CONCLUSION: Reading assessments are a useful tool for diagnosing psychogenic visual disturbances in adults and for coping with functional vision impairment.

[Fixation points and retinal sensitivity observed in reading text by patients with bilateral macular atrophy].

PURPOSE: To study by use of a scanning laser ophthalmoscope(SLO). How patients with bilateral macular atrophy use their retinas in reading Japanese sentences of varying sizes. METHODS: Thirty-eight eyes of 19 patients with bilateral macular atrophy were examined. Sentences of a fixed length (MNREAD-J sentences) were projected onto the patients' retinas with the SLO, and the size of the letters was varied. Patients were asked to read aloud the sentences slowly, and both their voices and retinal images were recorded simultaneously on videotape so that we could locate the retinal area they were using for reading. We compared these fixation points in reading with simple fixation points obtained by SLO microperimetry. RESULTS: In 21 eyes, the patients used the same area of the retina in all measurements. In 15 eyes, the fixation points for reading differed from the fixation area measured by microperimetry. In 8 of the 15 eyes, the fixation area for reading changed as the letter size was altered. In 2 eyes, oral reading was impossible, and no fixation point was established. CONCLUSIONS: The combination of SLO with reading evaluation clarified the fixation area for oral reading. Multiple fixation points were thought to be present quite commonly in eyes with macular degeneration. The fixation point was thought to be determined by the macular condition and the size of the letters being read.

Reading ability after macular translocation surgery with 360-degree retinotomy.

PURPOSE: To report reading ability using a standardized reading chart after macular translocation with 360-degree retinotomy in eyes with age-related macular degeneration (AMD) or with myopic choroidal neovascularization (mCNV). DESIGN: Interventional case series. METHODS: In 34 eyes of 34 patients with subfoveal choroidal neovascular membrane (AMD, 23; mCNV, 11), macular translocation surgery with 360-degree retinotomy and simultaneous extraocular muscle surgery were performed. The average age was 67.4 +/- 7.9 years, and the average follow-up period was 7.6 +/- 3.3 months. The best-corrected far visual acuity (FVA) was measured with a standardized visual acuity chart using Landolt Cs, and the critical print size (CPS) was determined with the Japanese version of the Minnesota reading chart (MNREAD-J Chart) preoperatively and postoperatively. Preoperative and postoperative change in the CPS was compared with the subjective visual improvement as assessed by a questionnaire. RESULTS: The postoperative improvement of FVA was statistically significant in eyes with mCNV (P =.010) but not significant in eyes with AMD (P =.495). The postoperative improvement of CPS was statistically significant both in eyes with AMD (P =.027) and in eyes with mCNV (P =.004). The subjective visual improvement was significantly correlated with the change of CPS in patients after a second better eye surgery. CONCLUSIONS: After macular translocation with 360-degree retinotomy, the improvement of reading ability was significant in eyes with both AMD and mCNV. We conclude that this surgical method is well suited to improve reading ability of patients with AMD or mCNV.