Fixation stability after surgical treatment of strabismus and biofeedback fixation training in amblyopic eyes.

BACKGROUND: Visual fixation may be affected in amblyopic patients and, moreover, its stability may be associated with the effects of amblyopic treatments on visual performance in patients with strabismus. Therefore, fixation stability is a relevant biomarker that might predict the recurrence of amblyopia after a therapeutic intervention. Microperimetric biofeedback fixation training (BFT) can stabilize visual fixation in adult patients with central vision loss. It was the purpose of the present study to evaluate the effects of BFT on fixation stability in adult amblyopic patients after surgical intervention to treat strabismus. METHODS: Participants were 12 patients with strabismus (mean age = 29.6 ± 8.5 years; 6 females) and 12 healthy volunteers (mean age = 23.8 ± 1.5 years; 9 females). The protocol included ophthalmological and microperimetric follow-ups to measure fixation stability and macular sensitivity. BFT was applied monocularly to four amblyopic eyes either on the spontaneous preferential retinal locus or to a fixation area closer to the anatomical fovea after surgical treatment of strabismus. RESULTS: Baseline measurements showed significantly altered microperimetric average threshold in amblyopic eyes compared to fellow eyes (p = 0.024) and compared to control eyes (p < 0.001). Fixation was unstable in amblyopic eyes compared to control eyes (p < 0.001). Fixation stability did not significantly change after surgical alignment of strabismus (p = 0.805). BFT applied to operated eyes resulted in a more stable fixation with improvements of about 50% after three months of training. CONCLUSIONS: Fixation stability improvements following BFT highlight its potential use in adult amblyopic eyes after the surgical alignment of the strabismus. Future investigations may also consider applying this method in combination with standard treatments to improve vision in amblyopic patients.

Inhaled H2 or CO2 Do Not Augment the Neuroprotective Effect of Therapeutic Hypothermia in a Severe Neonatal Hypoxic-Ischemic Encephalopathy Piglet Model.

Hypoxic-ischemic encephalopathy (HIE) is still a major cause of neonatal death and disability as therapeutic hypothermia (TH) alone cannot afford sufficient neuroprotection. The present study investigated whether ventilation with molecular hydrogen (2.1% H2) or graded restoration of normocapnia with CO2 for 4 h after asphyxia would augment the neuroprotective effect of TH in a subacute (48 h) HIE piglet model. Piglets were randomized to untreated naïve, control-normothermia, asphyxia-normothermia (20-min 4%O2-20%CO2 ventilation; Tcore = 38.5 °C), asphyxia-hypothermia (A-HT, Tcore = 33.5 °C, 2-36 h post-asphyxia), A-HT + H2, or A-HT + CO2 treatment groups. Asphyxia elicited severe hypoxia (pO2 = 19 ± 5 mmHg) and mixed acidosis (pH = 6.79 ± 0.10). HIE development was confirmed by altered cerebral electrical activity and neuropathology. TH was significantly neuroprotective in the caudate nucleus but demonstrated virtually no such effect in the hippocampus. The mRNA levels of apoptosis-inducing factor and caspase-3 showed a ~10-fold increase in the A-HT group compared to naïve animals in the hippocampus but not in the caudate nucleus coinciding with the region-specific neuroprotective effect of TH. H2 or CO2 did not augment TH-induced neuroprotection in any brain areas; rather, CO2 even abolished the neuroprotective effect of TH in the caudate nucleus. In conclusion, the present findings do not support the use of these medical gases to supplement TH in HIE management.

Preliminary Findings on the Optimization of Visual Performance in Patients with Age-Related Macular Degeneration Using Biofeedback Training.

Biofeedback training has been used to improve fixation stability in subjects with central vision loss, but the psychophysiological mechanisms underlying the functional improvements resulted was not reported. The aim of this study was to investigate the effects of microperimetric biofeedback training on different visual functions and self-reported quality of vision in subjects with age-related macular degeneration. This case-control study included six subjects (72.0 ± 6.1 years of age) diagnosed with age-related macular degeneration (wet or dry) with low vision (best corrected visual acuity ranging from 0.5 to 0.1 in the study eye) and five healthy volunteers (64.2 ± 3.7 years of age). Ophthalmological and functional examinations were obtained from all subjects twice with an approximately 3-month interval. Subjects with central vision loss performed 12 sessions (10 min each) of biofeedback training between the two examinations. Functional evaluation included: microperimetry, spatial luminance contrast sensitivities, color vision thresholds, visual acuity, and reading speed. Visual performance during daily activities was also assessed using a standardized questionnaire. The ratio (2nd/1st examination) of the spatial luminance contrast sensitivity at lower spatial frequencies were much higher for the training subjects compared with the controls. In addition, self-reported quality of vision improved after the training. The significant improvement of the visual function such as spatial luminance contrast sensitivity may explain the better self-reported quality of vision. Possible structural and physiological mechanisms underlying this neuromodulation are discussed.

Cataract surgery anaesthesia: is topical anaesthesia really better than retrobulbar?

PURPOSE: To compare the effectiveness for the patient of retrobulbar anaesthesia (RBA) and topical anaesthesia (TA) in cataract surgery by phacoemulsification. METHODS: We performed a prospective, randomized study on 115 patients operated at our clinic using the two anaesthesia techniques. The RBA group comprised 57 patients (20 women, 37 men; age 72 +/- 10 years); the TA group comprised 58 patients (20 women, 38 men; age 74 +/- 10 years). Measured parameters were: blood pressure; heart rate; blood oxygen saturation level; serum adrenaline, noradrenaline and cortisol levels; white blood cell count; indicated pain during the procedure, and pain as reported by the patient afterwards. Two psychological tests were used: the State-Trait Anxiety Inventory (STAI), and the patient-selected face-scale test. Statistical analysis was performed using Student's t-test and the chi-square test. Results were also analysed using a logistic regression model. RESULTS: Both types of anaesthesia were adequate for the surgical procedure. In the RBA group fewer patients experienced pain during surgery (p < 0.01) and fewer recalled any perioperative discomfort. With RBA the objective parameters were more stable than with TA, and systolic blood pressure was significantly lower (p = 0.01). The logistic model was able to predict perioperative pain with 93% certainty. Pain sensitivity was higher in younger patients and in patients with higher initial cortisol and noradrenaline serum levels. CONCLUSIONS: Both methods of anaesthesia are appropriate, but phacoemulsification with TA is more painful than with RBA. In hypertonic patients and younger patients who are more susceptible to pain, TA should be avoided or used in combination with individualized sedation.