Neural circuit involved in idiopathic infantile nystagmus syndrome based on FMRI.

PURPOSE: To identify the neural circuitry of idiopathic infantile nystagmus syndrome (INS), characterized by an early onset alternating series of slow and rapid eye movements that can manifest in different waveforms and genetic lines. The neural circuitry of INS is currently unknown. METHODS: A novel functional magnetic resonance imaging (fMRI) method, referred to as the null zone fMRI technique, was used to identify the neural circuitry for INS. In the null zone fMRI technique, a gaze position with minimal nystagmus within the null zone was linked to the fMRI "off" condition and a gaze position with robust nystagmus outside of the null zone was linked to the fMRI "on" condition. Eye movements were monitored with an fMRI compatible eye tracker and observed in real time to ensure subject compliance in "on" and "off" states. Subjects with INS (n = 4) included three family members (a mother and two daughters) with presumed autosomal dominant INS, as well as age- and gender-matched normal controls (n = 3). RESULTS: Three of four subjects with INS demonstrated significant increased activation of the declive of the cerebellum, whereas no normal subjects under identical conditions showed activation of the declive of the cerebellum. Both groups showed significant activation in the occipital lobe (Brodmann areas 17, 18, 19, and cuneus). CONCLUSION: A novel fMRI method demonstrated that the declive of the cerebellum is actively involved in INS. These are the first results to identify the cerebellum, and specifically the declive, as a possible site involved in the ocular motor dysfunction known as INS.

Normative database of donor keratographic readings in an eye-bank setting.

PURPOSE: To generate a normative donor topographic database from rasterstereography images of whole globes acquired in an eye-bank setting with minimal manipulation or handling. SETTING: Eye-bank laboratory. METHODS: In a retrospective study, rasterstereography topographic images that had been prospectively collected in duplicate of donor eyes received by the Central Ohio Lions Eye Bank between 1997 and 1999 were analyzed. Best-fit sphere (BFS) and simulated keratometry (K) values were extracted. These values were recalculated after application of custom software to correct any tilt of the mapped surfaces relative to the image plane. The mean value variances between right eyes and left eyes, between consecutive scans, and after untilting were analyzed by repeated-measures analysis of variance and t tests (P.05, Kolmogorov-Smirnov). There was no difference between right and left eyes or consecutive scans (P>.05). The mean values changed when the images were tilt-corrected (P<.05). The right eye BFS, Kflat, and Ksteep values of 42.03 diopters (D) +/- 1.88 (SD), 42.21 +/- 2.10 D, and 43.82 +/- 2.00 D, respectively, increased to 42.52 +/- 1.73 D, 43.05 +/- 1.99 D, and 44.57 +/- 2.02 D, respectively, after tilt correction. CONCLUSIONS: Keratometric parameter frequency distributions from the donor database of tilt-corrected data were normal in distribution and comparable to parameters reported for normal eyes in a living population. These findings show the feasibility and reliability of routine donor-eye topography by rasterstereography. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Effect of soft contact lenses on optical measurements of axial length and keratometry for biometry in eyes with corneal irregularities.

PURPOSE: To assess the repeatability and reliability of IOLMaster (Carl Zeiss Meditec, Inc., Dublin, CA) axial length and keratometry measurements (K readings) with a soft contact lens on normal eyes. The method is designed for eyes with corneal irregularities or after endothelial keratoplasty. METHODS: Biometry was performed on 20 healthy right eyes of volunteer subjects with mean age, 27.3 +/- 4.9 years; axial length, 24.77 +/- 1.04 mm; and K reading, 43.48 +/- 1.69 D. Axial length and keratometry were measured and repeated with -0.5 D SofLens38 (Bausch & Lomb, Rochester, NY) and Acuvue2 (Johnson & Johnson, New Brunswick, NJ) soft contact lenses. Repeatability and reliability were evaluated. Contact lens thickness was measured directly by corneal optical coherence tomography (OCT). RESULTS: Axial lengths increased 59 +/- 10 microm with SofLens38 and 134 +/- 13 microm with Acuvue2, and these changes correlated with the OCT contact lens thicknesses (P = 0.995). The axial length variability remained constant (P = 0.18), measuring 24 +/- 10 microm for SofLens38 and 23 +/- 8 microm for Acuvue2 compared with 20 +/- 7 microm with no lens. K readings of 43.08 +/- 1.66 D with SofLens38, 42.79 +/- 1.57 D with Acuvue2, and 43.48 +/- 1.69 D with no lens corresponded to differences of -0.40 +/- 0.12 D with SofLens38 and -0.69 +/- 0.19 D with Acuvue2. The K-reading variability increased slightly from 0.04 to 0.09 D with either lens. CONCLUSIONS: Low-power soft contact lenses enable reliable and repeatable IOLMaster axial length and K-reading measurements. Correcting for the measurable lens thickness and lens effects, a <0.5-D error in the Sanders-Retzlaff-Kraff (SRK) II power formula is predicted.

The effects of L-dopa on the functional magnetic resonance imaging response of patients with amblyopia: a pilot study.

PURPOSE: We investigated the effects of a single dose of levodopa (L-dopa) on the level and extent of visual cortex activation of subjects with amblyopia and normal subjects using blood oxygenation level-dependent functional magnetic resonance imaging (fMRI). SUBJECTS AND METHODS: Six patients with amblyopia and 9 control patients were recruited. A baseline fMRI session was followed by a second session 90 minutes after the dose of L-dopa. Visual stimuli included vertical sinusoidal gratings with spatial frequencies of 1 and 2 cpd that were counterphased at 4 Hz. Stimuli were presented monocularly and binocularly. The fMRI response was characterized by the total volume and the average level of activation within the occipital cortex. An interocular absolute difference (IDIF) was defined in terms of said measures for between-population analysis of monocular data. RESULTS: After the administration of L-dopa, visual acuity improved significantly ( P = 0.026) from 0.72 +/- 0.21 (mean +/- SD) to 0.64 +/- 0.24 LogMAR in the amblyopic eye, although remaining the same in the dominant eye and in the eyes of control subjects. The response to L-dopa was found to be population-specific, as indicated by a significant treatment-by-population interaction for the volume of activation IDIF ( P = 0.018) measure: subjects with amblyopia exhibited a post-treatment increase in the volume of activation IDIF whereas control subjects showed a less prominent decrease. This post-treatment increase of IDIF in subjects with amblyopia may be explained by the decrease in the volume of activation found for the amblyopic eye after L-dopa ( P = 0.038). No L-dopa-related activation changes were detected for dominant eye or binocular stimulation in the amblyopic group, and no change was detected in control subjects. CONCLUSION: L-dopa elicits a population-specific modulation of the fMRI response, namely, a reduced total volume of activation from the amblyopic eye despite improvement in visual acuity.

Biotechnology apprenticeship for secondary-level students: teaching advanced cell culture techniques for research.

The purpose of this article is to discuss small-group apprenticeships (SGAs) as a method to instruct cell culture techniques to high school participants. The study aimed to teach cell culture practices and to introduce advanced imaging techniques to solve various biomedical engineering problems. Participants designed and completed experiments using both flow cytometry and laser scanning cytometry during the 1-month summer apprenticeship. In addition to effectively and efficiently teaching cell biology laboratory techniques, this course design provided an opportunity for research training, career exploration, and mentoring. Students participated in active research projects, working with a skilled interdisciplinary team of researchers in a large research institution with access to state-of-the-art instrumentation. The instructors, composed of graduate students, laboratory managers, and principal investigators, worked well together to present a real and worthwhile research experience. The students enjoyed learning cell culture techniques while contributing to active research projects. The institution's researchers were equally enthusiastic to instruct and serve as mentors. In this article, we clarify and illuminate the value of small-group laboratory apprenticeships to the institution and the students by presenting the results and experiences of seven middle and high school participants and their instructors.