Prediction of refractive error and its progression: a machine learning-based algorithm.

OBJECTIVE: Myopia is the refractive error that shows the highest prevalence for younger ages in Southeast Asia and its projection over the next decades indicates that this situation will worsen. Nowadays, several management solutions are being applied to help fight its onset and development, nonetheless, the applications of these techniques depend on a clear and reliable assessment of risk to develop myopia. METHODS AND ANALYSIS: In this study, population-based data of Chinese children were used to develop a machine learning-based algorithm that enables the risk assessment of myopia's onset and development. Cross-sectional data of 12 780 kids together with longitudinal data of 226 kids containing age, gender, biometry and refractive parameters were used for the development of the models. RESULTS: A combination of support vector regression and Gaussian process regression resulted in the best performing algorithm. The Pearson correlation coefficient between prediction and measured data was 0.77, whereas the bias was -0.05 D and the limits of agreement was 0.85 D (95% CI: -0.91 to 0.80D). DISCUSSION: The developed algorithm uses accessible inputs to provide an estimate of refractive development and may serve as guide for the eye care professional to help determine the individual best strategy for management of myopia.

The retinal locus of fixation in simulations of progressing central scotomas.

Patients with central scotoma use a preferred retinal locus (PRL) of fixation to perform visual tasks. Some of the conditions that cause central scotoma are progressive, and as a consequence, the PRL needs to be adjusted throughout the progression. The present study investigates the peripheral locus of fixation in subjects under a simulation of progressive central scotoma. Five normally sighted subjects participated in the study. A foveally centered mask of varying size was presented to simulate the scotoma. Initially, subjects developed a peripheral locus of fixation under simulation of a 6° scotoma, which was used as a baseline. The progression was simulated in two separate conditions: a gradual progression and an abrupt progression. In the gradual progression, the diameter of the scotoma increased by a fixed amount of either 1° or 2° of visual angle, thus scotomas of 8°, 10°, and 11° of visual angle were simulated. In the abrupt progression, the diameter was adjusted individually to span the area of the visual field used by the current peripheral locus of fixation. Subjects located the peripheral locus of fixation along the same meridian under simulation of scotoma progression. Furthermore, no differences between the fixation stability of the baseline locus of fixation and the incremental progression locus of fixation were found whereas, in abrupt progression, the fixation stability decreased significantly. These results provide first insight into fixation behavior in a progressive scotoma and may contribute to the development of training tools for patients with progressive central maculopathies.

Transfer of an induced preferred retinal locus of fixation to everyday life visual tasks.

Subjects develop a preferred retinal locus of fixation (PRL) under simulation of central scotoma. If systematic relocations are applied to the stimulus position, PRLs manifest at a location in favor of the stimulus relocation. The present study investigates whether the induced PRL is transferred to important visual tasks in daily life, namely pursuit eye movements, signage reading, and text reading. Fifteen subjects with normal sight participated in the study. To develop a PRL, all subjects underwent a scotoma simulation in a prior study, where five subjects were trained to develop the PRL in the left hemifield, five different subjects on the right hemifield, and the remaining five subjects could naturally chose the PRL location. The position of this PRL was used as baseline. Under central scotoma simulation, subjects performed a pursuit task, a signage reading task, and a reading-text task. In addition, retention of the behavior was also studied. Results showed that the PRL position was transferred to the pursuit task and that the vertical location of the PRL was maintained on the text reading task. However, when reading signage, a function-driven change in PRL location was observed. In addition, retention of the PRL position was observed over weeks and months. These results indicate that PRL positions can be induced and may further transferred to everyday life visual tasks, without hindering function-driven changes in PRL position.

Can positions in the visual field with high attentional capabilities be good candidates for a new preferred retinal locus?

The sustained component of visual attention lowers the perceptual threshold of stimuli located at the attended region. Attentional performance is not equal for all eccentric positions, leading to variations in perception. The location of the preferred retinal locus (PRL) for fixation might be influenced by these attentional variations. This study investigated the relation between the placement of sustained attention and the location of a developed PRL using simulations of central scotoma. Thirteen normally sighted subjects participated in the study. Monocular sustained attention was measured in discrete eccentric locations of the visual field using the dominant eye. Subsequently, a six degrees macular scotoma was simulated and PRL training was performed during eight ten-minutes blocks of trials. After training, every subject developed a PRL. Subjects with high attentional capabilities in the lower hemifield generally developed PRLs in the lower hemifield (n=10), subjects with high attentional capabilities in the upper hemifield developed PRLs in the upper hemifield (n=2) and one subject with similar attentional capabilities in the upper and lower hemifield developed the PRL on the upper hemifield. Analyzed individually, the results showed that 70% of the subjects had a PRL location in the hemifield where high attentional performance was achieved. These results suggest that attentional capabilities can be used as a predictor for the development of the PRL and are of significance for low vision rehabilitation and for the development of new PRL training procedures, with the option for a preventive attentional training in early macular disease to develop a favorable PRL.

A preferred retinal location of fixation can be induced when systematic stimulus relocations are applied.

Patients with central vision loss obtain visual information by fixating on an object eccentrically with a preferred retinal locus of fixation (PRL). Patients do not always choose the most efficient PRL position, and as a consequence, visual performance is not always fully exploited. This study investigates whether PRLs can be induced by applying systematic stimulus relocations. The PRL was trained using a central scotoma simulation in 15 healthy subjects. They performed different visual tasks during four sessions, after which their reading performance was evaluated. In five subjects the stimulus was relocated to the left hemifield whenever a saccade would place the stimulus on the opposite hemifield. In five different subjects the relocation was inversed: The stimulus was located in the right hemifield. The relocation was 7.5° of visual angle and it was applied horizontally. Five additional subjects naturally chose the PRL location. They were used as the control group to evaluate the development of a PRL. After training, subjects performed visual search tasks on static stimuli. Evaluation after training showed that systematic stimulus relocations can be used to influence the development of the PRL. These results might be significant for the development of training strategies for the visually impaired.