Giuseppe Mirabella

Reduced Grating Acuity Associated with Retinal Toxicity in Children with Infantile Spasms on Vigabatrin Therapy

PURPOSE To determine whether visual functions are decreased in children with infantile spasms and vigabatrin-attributed retinal toxicity. METHODS Contrast sensitivity and grating acuity were measured by using sweep visual evoked potential (VEP) testing in 42 children with infantile spasms (mean age, 29.23 +/- 18.31 months). All children had been exposed to vigabatrin (VGB) for a minimum of 1 month. These children were divided into retinal toxicity and no toxicity groupings based on 30-Hz flicker amplitude reductions on the full-field electroretinogram. A multivariate analysis of variance (MANOVA) compared visual functions between children with and without retinal toxicity. RESULTS The MANOVA showed that visual function was significantly affected by VGB retinal toxicity. Further univariate analysis revealed that grating acuity was significantly reduced in children with toxicity. No differences in contrast sensitivity were found between children with toxicity and those without. CONCLUSIONS Reduced visual functions from VGB-attributed retinal toxicity can be detected in children with infantile spasms with the sweep VEP.

Visual Development of Human Milk–Fed Preterm Infants Provided With Extra Energy and Nutrients After Hospital Discharge

BACKGROUND Human milk (HM) is the optimal way to nourish preterm low birth weight (LBW) infants after hospital discharge. However, there are few data on which to assess whether HM alone is sufficient to address hospital-acquired nutrition deficits, and no adequately powered studies have examined this question using neurodevelopment as an outcome. The purpose of this work was to determine whether adding extra energy and nutrients to the feedings of predominantly HM-fed LBW infants early after discharge improves their visual development. Visual development was used in this study as a surrogate marker for neurodevelopment. METHODS At discharge, 39 predominantly HM-fed LBW infants (750-1800 g, 1288 ± 288 g) were randomized to receive human milk alone (control) or around half of the HM received daily mixed with a multinutrient fortifier (intervention) for 12 weeks. Grating acuity (ie, visual acuity) and contrast sensitivity were assessed using sweep visual-evoked potential tests at 4 and 6 months corrected age. RESULTS At 4 and 6 months corrected age, intervention infants demonstrated higher grating acuity compared to those in the control group (intervention: 7.8 ± 1.3 and 9.7 ± 1.2 [cycles/degree] vs control 6.9 ± 1.2 and 8.2 ± 1.3, P = .02). Differences in contrast sensitivity did not reach statistical significance (P = .11). CONCLUSION Adding a multinutrient fortifier to a portion of the expressed breast milk provided to predominantly HM-fed LBW infants early after discharge improves their early visual development. Whether these subtle differences in visual development apply to other aspects of development or longer term neurodevelopment are worthy of future investigation.

Effects of age, viewing distance and target complexity on static ocular counterroll

The ocular counterroll (OCR) reflex generates partially compensatory torsional eye movements during static head roll tilt. We assessed the influence of age, viewing distance and target complexity on the OCR across the age span (13-63 years; n=47), by recording eye movements during head-on-body roll tilt (0+/-40 degrees in 5 degrees steps) while subjects viewed simple vs. complex targets at 0.33 and 1m. We found that subjects > or = 31 years had lower gains than those < or =30 years, but only for far targets. Consistent with prior reports, far targets elicited higher OCR gains than near targets, and target complexity had no effect on gains, suggesting that visual input is primarily used to maintain vergence during OCR.

Effects of Earth-Fixed vs Head-Fixed Targets on Static Ocular Counterroll

OBJECTIVE To investigate whether static ocular counterroll (OCR) gain is reduced during viewing of an earth-fixed vs a head-fixed target. METHODS Twelve healthy individuals were recruited. The target consisted of a red fixation cross against a grid pattern at a viewing distance of 33 cm. The target was mounted on a wall (earth fixed) or was coupled to the head (head fixed). Changes in mean torsional eye position were plotted as a function of head position steps (0 degrees +/- 25 degrees in 5 degrees steps), and sigmoidal fits were performed. Mean static OCR gain was calculated by taking the derivative of the fitted functions. RESULTS Mean static OCR gain was 40% lower with a head-fixed target (-0.084) than with an earth-fixed target (-0.141) (P < .001). CONCLUSION The reduction in static OCR gain during viewing of a head-fixed target indicates that static OCR is partially negated when a target moves with the head.

Timing of Surgery for Infantile Esotropia in Humans: Effects on Cortical Motion Visual Evoked Responses

PURPOSE Infantile esotropia is associated with maldevelopment of cortical visual motion processing, manifested as directional asymmetry of motion visual evoked potentials (mVEPs). The purpose of this study was to determine whether early surgery at or before age 11 months could promote the development of cortical visual motion processing in human infants, compared with standard surgery at age 11 to 18 months. METHODS Sixteen children with a constant, infantile esotropia >or=30 prism diopters and onset before age 6 months were recruited prospectively. Eight of them underwent early surgery at <or=11 months of age, and eight underwent standard surgery at 11 to 18 months of age. Seven age-matched normal subjects served as the control. At 2 to 2.5 years of age, mVEPs were measured during monocular viewing of a grating that shifted between two positions with a lateral displacement of 90 degrees at 10 Hz. Nasotemporal mVEP asymmetry was assessed by an amplitude asymmetry index and by the presence of a significant interocular phase difference. RESULTS The mean asymmetry index and interocular phase difference in the early surgery group were comparable to that in age-matched control subjects, and they were significantly lower than those in the standard surgery group. CONCLUSIONS Early surgery for infantile esotropia promotes the development of cortical visual motion processing, whereas standard surgery is associated with abnormal mVEPs. The results provide additional evidence that early strabismus repair is beneficial for cortical development in human infants.

Which way is upright and normal? Haptic perception of letters above head level.

In three experiments, the perception of the apparent orientation of block letters shown in various orientations above the subject’s head in the horizontal plane was examined. A block letter F with its front facing down toward the observer has two crossbars on its right side; the top is the part with the long crossbar, and the base has no bar. The experiments involved changing the locations of these parts with respect to the observer. In Experiment 1, the subjects using touch most often identified a letter as having its left and right sides in a normal orientation if the front of the block letter faced upwards away from the observer, with the bar on the right and the top of the letter farther from the subject than the letter’s base. In Experiment 2, the subjects judging visualuprightness favored positions in which the bars were on the right, the top of the block letter was near them, and the letter’s front faced downwards toward the observer. In Experiment 3, the subjects using touch most often assessed letters as being upright if the top of the letter was the farthest part and the bar was on the right. The results suggest that, when assessing orientation, subjects using touch favored positions that would be reached by a letter moving vertically upwards from table height, but subjects relying on vision favored positions reached by a letter moving in an arc centered on the subject’s head (on the eyes, in particular).

Effectiveness of Telescopic Magnification in the Treatment of Amblyopia: A Pilot Study

OBJECTIVE To compare the effectiveness of patching plus telescopic magnification vs patching alone in treating refractory amblyopia. METHODS Children aged 4 to 17 years who failed previous amblyopia treatment were recruited into this prospective study. Subjects were randomly assigned to either 30 minutes per day of patching of the fellow eye only (n = 7) or 30 minutes per day of patching of the fellow eye plus concurrent use of a telescope in the amblyopic eye (n = 8). MAIN OUTCOME MEASURE Best-corrected logMAR visual acuity score of the amblyopic eye after 17 weeks of treatment. RESULTS Both treatment groups demonstrated significant improvement in visual acuity in the amblyopic eye after 17 weeks (P = .001). Improvements in the patching-only group were slightly greater over the course of treatment, but this difference was not statistically significant (P = .06). At 17 weeks, mean visual acuity improvement from baseline was 0.14 logMAR (SD, 0.13 logMAR) in the patching-only group and 0.06 logMAR (SD, 0.17 logMAR) in the patching plus telescope group (P = .11). The 17-week visual acuity was at least 0.2 logMAR and/or improved from baseline by at least 0.2 logMAR in 2 patients in the patching-only group and none in the patching plus telescope group (P = .08). CONCLUSION Treatment of refractory amblyopia in children using telescopic magnification did not appear to confer any additional benefits over patching alone. APPLICATION TO CLINICAL PRACTICE Occlusion and penalization remain the standard of care for patients with amblyopia and should remain the benchmark against which other treatments are compared in clinical trials for amblyopia therapy. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00970554.