Preferred retinal loci relationship to macular scotomas in a low-vision population.

http://redwood.psych.cornell.edu/papers/Field_Brady_1997.pdf

Visual sensitivity, blur and the sources of variability in the amplitude spectra of natural scenes

Image enhancement has been shown to improve face recognition by visually impaired observers. We conducted three experiments in an effort to refine our understanding of the parameters leading to this effect. In experiment 1 we found that the band of spatial frequencies between 4 and 8 cycles/face is critical for face recognition. In experiment 2 we found that enhancement of these frequencies and the resulting image distortion actually reduced recognition performance for normal observers. Since the degradation of performance by low vision is larger than the effect of distortion, the enhancement that reduces performance for normal observers may still be beneficial for the visually impaired observer. Experiment 3 found that patients tend to prefer images enhanced at frequencies higher than the critical frequencies found in experiment 1. Such individually selected enhancement did not improve recognition in comparison with uniformly applied enhancement. The lack of an enhancement effect may be due to the small variability in enhancement frequencies selected by our subject population.

Image enhancement for the visually impaired: the effects of enhancement on face recognition.

Compared to most ophthalmic technologies, adaptive optics, or AO, is relatively young. The first working systems were presented in 1997 and, owing in part to its complexity, the development of AO systems has been relatively slow. Nevertheless, AO for vision science is coming of age and the scope of applications continues to increase. Applications of AO can be broadly split along two lines; for retinal imaging and for testing visual function. This review will focus on the applications of adaptive optics for testing visual function. Since this represents only a subset of the field of AO for ophthalmoscopy, it is possible to cite virtually every paper that has been published in the field to date. As such, this is a comprehensive review whose intent is to get all readers up to speed on the state of the art. More importantly, perhaps, this review will focus on the types of science that can be accomplished with AO with a view to future applications. The reference list alone is informative, since the reader will quickly discover that the community that is using AO for vision science is rather small. Looking at the dates for the cited papers, the reader will also discover that the field is rapidly expanding.

Adaptive optics for studying visual function: a comprehensive review.

Aims: (1) To explore the relation between performance on tasks of familiar face recognition (FFR) and face expression difference discrimination (FED) with both perceived disability in face recognition and clinical measures of visual function in subjects with age related macular degeneration (AMD). (2) To quantify the gain in performance for face recognition tasks when subjects use a bioptic telescopic low vision device. Methods: 30 subjects with AMD (age range 66–90 years; visual acuity 0.4–1.4 logMAR) were recruited for the study. Perceived (self rated) disability in face recognition was assessed by an eight item questionnaire covering a range of issues relating to face recognition. Visual functions measured were distance visual acuity (ETDRS logMAR charts), continuous text reading acuity (MNRead charts), contrast sensitivity (Pelli-Robson chart), and colour vision (large panel D-15). In the FFR task, images of famous people had to be identified. FED was assessed by a forced choice test where subjects had to decide which one of four images showed a different facial expression. These tasks were repeated with subjects using a bioptic device. Results: Overall perceived disability in face recognition did not correlate with performance on either task, although a specific item on difficulty recognising familiar faces did correlate with FFR ( r = 0.49, p r = −0.69, p r = −0.79, p Conclusion: Distance and reading visual acuity are closely associated with measured task performance in FFR and FED. A bioptic low vision device can offer a significant improvement in performance for face recognition tasks, and may be useful in reducing the handicap associated with this disability. There is, however, little evidence for a correlation between self rated difficulty in face recognition and measured performance for either task. Further work is needed to explore the complex relation between the perception of disability and measured performance.

https://bjo.bmj.com/content/bjophthalmol/86/9/1019.full.pdf

Face recognition in age related macular degeneration: perceived disability, measured disability, and performance with a bioptic device

Digital image enhancement has been proposed as an aid for the visually impaired The capability of two enhancement techniques to improve recognition of images by patients with central scotoma or cataracts was evaluated using image-processing simulations and direct patient testing Enhancements and simulations were based on measurements of contrast sensitivity loss for patients with macular disease Contrast sensitivity loss was measured using Gabor-type localized stimuli and paradigms that are appropriate for analyzing form perception The simulations using the contrast sensitivity data suggested that patients with moderate visual loss (20/70-20/200) may have difficulty recognizing faces and may benefit from enhancement by both of the techniques used Ability to recognize celebrities from enhanced images improved for 39 of the 46 patients tested The improvement was significant (P less than 005) for 16 of the 38 patients with central visual loss and for 3 of 8 patients with anterior segment media opacities tested The simulations suggest that the benefits of image enhancement may be similar or even greater for recognition of other types of images

Image enhancement for the visually impaired. Simulations and experimental results.

The authors evaluate whether patients demonstrate improved face recognition when viewing enhanced images. Difficulty with face recognition is a frequent, early complaint of many patients with macular disease. Faces can be recognized when low-pass filtered to a large degree or high-pass filtered. To evaluate actual face recognition rather than the ability to discriminate among test faces, the authors tested the patient's ability to recognize celebrities, which is more robust than the recognition of unfamiliar faces. It is shown that all patients demonstrated better face recognition with the enhanced images than with the original, untouched images. Analysis of the difference between the two areas under the receiver operating curves indicated a statistically significant increase in recognition for 8 out of 17 patients. Patients reported that the enhanced images were significantly clearer, sharper, and easier to see. >

G.M. Young

Papers

Image enhancement for the visually impaired. Simulations and experimental results.

Digital image enhancement for the visually-impaired: simulations and results