Journal of American Association for Pediatric Ophthalmology and Strabismus
Major articleFunctional magnetic resonance imaging as a tool for investigating amblyopia in the human visual cortex: A pilot study*,**
Section snippets
Subjects
Subjects included 5 patients with amblyopia (15-56 yrs. old) and 6 controls (25-48 yrs. old). Control subjects had no history of amblyogenic factors and had normal logMAR VA in each eye (mean VA, OD and OS, −0.17 (20/13.5)). Control subjects had a mean stereoacuity of 30 sec of arc based on the Randot stereoacuity test (Stereo Optical Co, Chicago, Ill) and normal contrast sensitivity functions in each eye based on the VCTS 6500 (Vistech Consultants Inc, Dayton, Ohio). Subjects with amblyopia
Monocular data
A statistically significant difference was found in the interocular cortical activation discrepancy of subjects with amblyopia versus that of the control group. The mean for the APD measure is reported in Table 1 along with the SE for the mean, as calculated for the 3 response measures (average signal change, area, and sum).
The population main effect was found to be statistically significant for all 3 response measures, as shown in Figure 3, where corresponding P values are reported.
Discussion
The results suggest that BOLD-contrast FMRI can detect amblyopia-related interocular cortical activation differences. Stimulation of the amblyopic eye elicits less total area and mean level of activation in the occipital cortex than stimulation of the dominant eye. An example of this effect is illustrated in Figure 6, which shows the occipital cortex activation patterns recorded for a subject with amblyopia under monocular stimulation of the dominant and amblyopic eyes with a 1 cpd stimulus.
Acknowledgements
The authors would like to thank Edward Herderick, BS, Jim Ibinson, BS (Biomedical Engineering Center, The Ohio State University), Jim Murakami, MD, and Mark Smith, MS (Department of Radiology, Columbus Children's Hospital).
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Cited by (52)
New concepts concerning the neural mechanisms of amblyopia and their clinical implications
2012, Canadian Journal of OphthalmologyCitation Excerpt :A number of neuroimaging studies114-149 have investigated the loci and extent of cortical deficits in humans with amblyopia using such techniques as positron emission tomography,114-119 anatomic121-124 and fMRI,123,125-149 and magnetoencephalography.150-152 Some neuroimaging studies have suggested that V1 may be normal,114,123,133,136,153 in contrast to many other neuroimaging studies115-119,121,125-127,129,134,140,141,148,154,155 and the large body of neurophysiologic work36,48-61,65-67 that have pointed to V1 as the first locus of dysfunction. The discrepancy among these studies may result from differences in techniques or stimuli used, as well as from differences in patient characteristics (e.g., amblyopia subtypes).
Relationship among fMRI, contrast sensitivity and visual acuity
2011, Brain ResearchCitation Excerpt :Given these difficulties, it is not surprising that fMRI studies typically employ 5–10 subjects. For example, Algaze et al. (2002) employed 11 subjects, Miki et al. (2001) 8 subjects, Lee et al. (2001) 14 subjects, Choi et al. (2001) 9 subjects, Goodyear et al. (2000) 10 subjects, Menon et al. (1997) 5 subjects, Imamura et al. (1997) 8 subjects, Singh et al. (2000) 10 subjects and Barnes et al. (2001) 10 or 11 subjects. As a consequence, the total number of subjects employed in the current study is about average for an fMRI study.
Instruction dependent activation during optokinetic nystagmus (OKN) stimulation: An FMRI study at 3 T
2010, Brain ResearchCitation Excerpt :The stimulus was delivered within the bore of the MRI scanner using an LCD projector (Sony VPL-X1000) fitted with a custom lens (Buhl Optical, Pittsburgh, PA). The visual stimulus was projected onto a rear-projection screen mounted on the head coil and visible to the subject through a tilted mirror placed above the subject's head (Algaze et al., 2002). The screen was placed 20–23 cm from subjects' eyes, depending on head size.
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This project has been supported by the Ohio Lions Eye Research Foundation. This study was conducted at The Ohio State University and Children's Hospital, Columbus, Ohio.
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Reprint requests: Cynthia Roberts, PhD, 270 Bevis Hall, 1080 Carmack Rd, Columbus, OH 43210; e-mail, [email protected].