Comparison of preoperative 10-Hz visual evoked potentials to contrast sensitivity and visual acuity after cataract extraction

SSFVEP as a potential electrophysiological examination for evaluating visual function of fundus diseases with vitreous hemorrhages: a clinical study

To investigate the sensitivity and potential application of steady-state flash visual evoked potentials (SSFVEP) in assessing the visual function of fundus diseases with vitreous hemorrhage. 18 patients diagnosed with monocular vitreous hemorrhages in the fundus were examined the flash visual evoked potentials (FVEP) and SSFVEP in both eyes. The difference in the P2-wave amplitude of FVEP and the average amplitude of SSFVEP waveform between the diseased eyes and those without vitreous hemorrhage were statistically compared. There was no significant difference in the waveform of FVEP between both eyes. The amplitude of P2-wave from FVEP of the diseased eye was slightly lower than that without vitreous hemorrhage. However, the difference was not statistically significant (P = 0.111). The waveform of SSFVEP in the eye without vitreous hemorrhage showed a towering shape, while that of the diseased eye was flat. The average amplitude of SSFVEP in the diseased eye was statistically lower than that without vitreous hemorrhage (P = 0.036). The difference ratio of SSFVEP amplitude between both eyes was significantly greater than that of FVEP amplitude (P = 0.028). In some fundus diseases with vitreous hemorrhage, SSFVEP had a higher sensitivity than FVEP, providing a novel potential application for visual function assessment.

Changes in the Parameters of Visual Evoked Potentials in Media Opacities

Purpose

This study compared flash visual evoked potentials (VEPs) parameter differences between eyes with unilateral opaque media and their normal contralateral counterparts.

Patients and Methods

We included 178 patients with unilateral media opacity and normal contralateral eye in each patient. The diseased eyes had normal ultrasonographic findings and were candidates for keratoplasty or anterior segment reconstruction. The patients underwent electrophysiological testing by the flash VEPs recording with the use of 1.4Hz (transient) and 8Hz (flicker) frequencies.

Results

The medians of P2 implicit times were significantly higher in eyes with media opacity than in normal eyes, with median differences between both eyes of -6.7 ms. Furthermore, the median N2P2 amplitude was 9.70 µv with media opacity compared with 11.00 µv in the normal eyes, with a significant difference of 1.3 (p = 0.002). The flash VEPs median parameters recorded at a frequency of 8-Hz showed significant differences in medians of spectral plots of 0.6 µv between normal and abnormal eyes. The same for the signal-to-noise ratio, where the difference in medians was 3 dB. Analysis of the difference between both eyes (normal-abnormal) in each patient showed in P2 implicit time a difference range of -49 to 54.7 ms with a median difference of -3 ms. The difference in amplitudes of recorded N2P2 showed a median of 2.13 µv. There was a statistically significant but weak negative correlation between N2P2 amplitude (r spearman = -0.173, p = 0.021) and the grades of corneal opacity.

Conclusion

Preoperative flash VEPs recording is useful for evaluating visual function in patients with unilateral media opacity to determine the future benefits of keratoplasty or anterior segment reconstruction. There are no correlations between the flash VEP parameters or the difference between the 2 eyes and the grades of corneal opacity.

Predicting visual function after an ocular bee sting

PURPOSE

To report a case of toxic optic neuropathy caused by an ocular bee sting.

METHODS

Case report and literature review.

RESULTS

A 44-year-old female presented with no light perception vision 2 days after a corneal bee sting in her right eye. She was found to have diffuse cornea edema with overlying epithelial defect and a pinpoint penetrating laceration at 6 o'clock. There was an intense green color to the cornea. The pupil was fixed and dilated with an afferent pupillary defect. A small hyphema was seen, and a dense white cataract had formed. A diagnosis of toxic endophthalmitis with associated toxic optic neuropathy was made. The patient underwent pars plana vitrectomy and lensectomy with anterior chamber washout. She was also placed on systemic broad-spectrum antibiotics. She had noted clinical improvement over the course of her hospitalization and was discharged with light perception vision. A corneal opacity precluded viewing of the fundus. We utilized ganzfeld electroretinography and flash visual evoked potentials (2 and 10 Hz) to assess the visual function. Both tests were normal and predicted improvement following restorative surgery. She underwent a secondary lens implantation with penetrating keratoplasty 7 months later. This was followed by an epiretinal membrane peel 1 year after the bee sting. Her best corrected visual acuity improved to 20/80.

CONCLUSION

Toxic endophthalmitis and toxic optic neuropathy can be complications of ocular bee sting. We discuss the management of this rare occurrence and the role of electroretinographic testing and visual evoked potentials in predicting visual outcome.

The role of visual evoked potential and electroretinography in the preoperative assessment of osteo-keratoprosthesis or osteo-odonto-keratoprosthesis surgery

PURPOSE

To determine the value of electroretinography (ERG) and visual evoked potential (VEP) in predicting visual outcome in patients undergoing osteo-keratoprosthesis (OKP) or osteo-odonto-keratoprosthesis (OOKP) surgery.

METHODS

We performed a retrospective cohort study of 143 eyes in 101 patients who underwent OKP or OOKP surgery. The subjects underwent ERG, VEP testing or both up to 6 months prior to surgery. The ERG and VEP results were classified into four categories based on wave amplitude, latency and configuration. The main outcome was the maximum best-corrected visual acuity (maxBCVA) reached at any time postoperatively.

RESULTS

One hundred thirty-four cases had undergone preoperative ERG, 82 VEP and 73 both examinations. The sensitivities of ERG and VEP to detect maxBCVA≥0.05 were 68.5% and 87%, respectively, while the specificity was 63.2% for ERG and 47.4% for VEP. The maxBCVA was significantly better in patients with normal ERG (p=0.033) and those with normal VEP (p=0.048), once having defined appropriate normal and abnormal cut-off levels. When comparing fellow eyes in patients who underwent surgery in both eyes, maxBCVA was better in the eyes that had better VEP results (p=0.013).

CONCLUSION

Eyes demonstrating normal ERG or VEP achieved better visual outcome than those with abnormal results. In addition, VEP proved instrumental in determining the eye with the best prognosis when comparing both eyes of a given patient.

Stable isotope ratios indicate that body condition in migrating passerines is influenced by winter habitat

Although predicted some time ago, there has been little success in demonstrating that the overall fitness of migratory birds depends on the combined influences of their experiences over all seasons. We used stable carbon isotope signatures (delta13C) in the claws of migrating black-throated blue warblers Dendroica caerulescens to infer their wintering habitats and investigated whether winter habitat selection can be linked to condition during migration. Resident bird species with low delta13C corresponded to selection of more mesic habitats, and migrating birds with low delta13C were in better condition than conspecifics with higher delta13C signatures. These findings concur with empirical observations on the wintering grounds, where dominants (mostly males) tend to exclude subordinates from mesic areas (considered to be high-quality habitats). We believe that variation in condition during migration may be one of the key factors determining differences in arrival times and condition at the breeding areas, which in turn have a major influence on reproductive success.

Stable isotopes examined across a migratory divide in Scandinavian willow warblers (Phylloscopus trochilus trochilus and Phylloscopus trochilus acredula) reflect their African winter quarters

The C and N isotopes of feathers from two subspecies of willow warblers Phylloscopus trochilus trochilus and Phylloscopus trochilus acredula) are isotopically distinct. Our analysis of 138 adult males from 14 sites distributed across Sweden shows that the mean delta15N and delta13C values of subspecies acredula (from latitudes above 63 degrees N) were significantly higher than the mean delta15N and delta13C values of subspecies trochilus (from latitudes below 61 degrees N). The analysed willow warbler feathers had been moulted in the winter quarters and the observed isotopic signatures should thus reflect the isotopic pattern of food assimilated in Africa. The isotopic data observed in Sweden match the cline in morphology, both showing abrupt changes around 62 degrees N. This result agrees with data from ringing recoveries indicating that the two subspecies occupy geographically and isotopically distinct wintering grounds in Africa. Our isotopic data suggest that analysis of stable isotopes of C and N is a promising method to track wintering quarters of European birds that migrate to Africa.

Effects of wavelength on the timing and laminar distribution of illuminance-evoked activity in macaque V1

Responses to full-field colored flashes (red, blue, and green) were compared with those to illuminance-matched white flashes in area V1, optic radiations, and the lateral geniculate nucleus of two alert macaques. Laminar profiles of visual evoked potentials (VEPs), current source density, and multiunit activity were obtained using multicontact electrodes capable of sampling from all layers of cortex or lateral geniculate nucleus, simultaneously. In striate cortex, stimulation with colored flash enhanced transmembrane current flow dramatically in both layer 4c and the supragranular laminae. Stimulation with red evoked the largest enhancement in every electrode penetration. The mean peak amplitudes of current sinks evoked by red were 203% and 537% of those evoked by white light in layer 4c and the supragranular laminae, respectively. Color effects in V1 were preceded by an initial epoch of wavelength-insensitive activity. In layer 4c, the red effect reached significance, on average, at 47 ms, or approximately 24 ms after the onset of transmembrane current flow. In the supragranular layers, the red effect reached significance, on average, at 55 ms, or approximately 14 ms after the onset of current flow. Recordings from optic radiations in the white matter below V1 and from lateral geniculate nucleus showed no significant difference in the responses to color and illuminance-matched white light. Enhancement of supragranular current flow with color stimulation increased the contribution of these laminae to the generation of the surface VEP. Comparison of the surface VEP wave forms evoked by white and color stimuli may, therefore, help to differentiate the responses of the granular and supragranular laminae.