In persons with congenital nystagmus (CN), the incessant to and fro oscillations of the eyes produce continuous motion and smear of the retinal image. However, unlike many patients in whom nystagmus is acquired, individuals with CN rarely report the visual world to be moving. A robust extraretinal signal has been shown to exist for the eye movements in CN, which neurologically """"""""cancels"""""""" much of the retinal image motion.
One aim of the proposed research is to document how operation of this """"""""cancellation"""""""" process depends upon the foveation periods of the CN waveform - brief intervals of relatively low eye velocity during which a target of regard is imaged at or near the fovea. A related aim is to compare the temporal characteristics of the """"""""cancellation"""""""" of CN to that for smooth eye movements in normal subjects, to determine whether the """"""""cancellation"""""""" mechanism is altered in CN. In addition to perceiving a stationary world, persons with CN typically don't perceive visual targets to be smeared.
A second aim of this research is to quantify the extent to which perception of image smear is reduced in subjects with CN and evaluate the contributions of three potential mechanisms: l) masking of smeared retinal images by a clearer image that is available during the foveation periods in the CN waveform, 2) suppression of image smear by the extraretinal signals for CN, and 3) neural sharpening of the moving retinal image by """"""""deblurring"""""""", as has been reported to occur in normal vision.
The third aim of this research is to document the effects of the retinal image motion in CN on two basic visual functions. First, sensitivity to changes in target orientation will be measured in subjects with CN and compared to the variability of torsional eye position, during both the entire CN waveform and just the foveation periods. Second, thresholds for perceiving stereoscopic depth will be measured and related to parameters of CN eye movements and to visual acuity. The stereothresholds of normal subjects for targets that move to simulate the retinal image motion in CN will document how stereopsis is affected by the CN retinal image motion per se. These results will also clarify how normal subjects maintain fine stereopsis, despite substantial retinal image motion and vergence errors that accompany voluntary head movements. Over all, the results of the proposed research will define how the potentially debilitating symptoms of oscillopsia and perceived image smear are prevented in subjects with CN, and how the characteristics of CN affect visual orientation sensitivity and stereopsis. A more complete picture than currently available of the visual capabilities and limitations of individuals with CN will result.
| Ukwade, Michael T; Bedell, Harold E (2012) Spatial-bisection acuity in infantile nystagmus. Vision Res 64:1-6 |
| Chung, Susana T L; LaFrance, Martin W; Bedell, Harold E (2011) Influence of motion smear on visual acuity in simulated infantile nystagmus. Optom Vis Sci 88:200-7 |
| Bedell, Harold E; Tong, Jianliang; Aydin, Murat (2010) The perception of motion smear during eye and head movements. Vision Res 50:2692-701 |
| Bedell, Harold E; Tong, Jianliang (2009) Asymmetrical perception of motion smear in infantile nystagmus. Vision Res 49:262-7 |
| Tong, Jianliang; Ramamurthy, Mahalakshmi; Patel, Saumil S et al. (2009) The temporal impulse response function during smooth pursuit. Vision Res 49:2835-42 |
| Patel, Saumil S; Bedell, Harold E; Tsang, Dorcas K et al. (2009) Relationship between threshold and suprathreshold perception of position and stereoscopic depth. J Opt Soc Am A Opt Image Sci Vis 26:847-61 |
| Bedell, Harold E; Ramamurthy, Mahalakshmi; Patel, Saumil S et al. (2008) The temporal impulse response function in infantile nystagmus. Vision Res 48:1575-83 |
| Tong, Jianliang; Stevenson, Scott B; Bedell, Harold E (2008) Signals of eye-muscle proprioception modulate perceived motion smear. J Vis 8:7.1-6 |
| Chung, Susana T L; Patel, Saumil S; Bedell, Harold E et al. (2007) Spatial and temporal properties of the illusory motion-induced position shift for drifting stimuli. Vision Res 47:231-43 |
| Tong, Jianliang; Aydin, Murat; Bedell, Harold E (2007) Direction and extent of perceived motion smear during pursuit eye movement. Vision Res 47:1011-9 |
Showing the most recent 10 out of 61 publications
