Macular thickness and retinal nerve fiber thickness analysis in ocular dominance / Espessura macular e fibra nervosa da retina análise de espessura no domínio ocular

Abstract Objective: To compare macular and peripapillary retinal nerve fiber layer thicknesses of dominant eye and non-dominant eye using optical coherence tomography (OCT). Methods: 104 eyes of 52 healthy young adults were included. Ophthalmological examinations; including measuring refraction, best corrected visual acuity, intraocular pressure (IOP) measurement, slit-lamb biomicroscopy, dilated fundus examination, measuring of central macular thickness (CMT), and peripapillary retinal nerve fiber layer (PRNFL) thickness were performed on each subject. Hole-in-the-card test was used to detect the ocular dominance. Results: There were 25 females (48%) and 27 males (52%) in the study. Eight participants had left eye dominance (15%), forty-four participants had right eye dominance (85%). Mean CMT was 192.5µm in dominant group and 191.9 µm in non-dominant group. There was no statistically significant difference between dominant eye group and non-dominant eye group in either macular thickness or peripapillary retinal nerve fiber layer thickness. Conclusions: No difference between macular and peripapillary retinal nerve fiber layer thicknesses were detected in dominant and non-dominant groups. Further evaluation is needed.

Resumo Objetivo: Comparar as espessuras da camada de fibras nervosas da retina macular e peripapilar do olho dominante e não dominante usando a tomografia de coerência óptica (OCT). Métodos: 104 olhos de 52 adultos jovens saudáveis foram incluídos. Exames oftalmológicos; incluindo medidas de refração, melhor acuidade visual corrigida, medição da pressão intraocular (PIO), biomicroscopia de fenda-cordeiro, exame do fundo dilatado, medição da espessura macular central (CMT) e espessura da camada de fibras nervosas da retina peripapilar (PRNFL) foram realizadas em cada sujeito. O teste Hole-in-the-card foi usado para detectar a dominância ocular. Resultados: houve 25 mulheres (48%) e 27 homens (52%) no estudo. Oito participantes tinham deixado a dominância do olho (15%), quarenta e quatro participantes tinham dominância do olho direito (85%). A CMT média foi de 192,5 µm no grupo dominante e 191,9 µm no grupo não dominante. Não houve diferença estatisticamente significativa entre o grupo dominante de olho e o grupo de olho não dominante tanto na espessura macular quanto na espessura da camada de fibras nervosas da retina peripapilar. Conclusões: Não houve diferença entre as espessuras das camadas de fibras nervosas da retina macular e peripapilar nos grupos dominante e não dominante. Mais avaliações são necessárias.

Extracellular signal-regulated kinase (ERK) activity during sleep consolidates cortical plasticity in vivo.

Ocular dominance plasticity (ODP) in the cat primary visual cortex (V1) is induced during waking by monocular deprivation (MD) and consolidated during subsequent sleep. The mechanisms underlying this process are incompletely understood. Extracellular signal-regulated kinase (ERK) is activated in V1 during sleep after MD, but it is unknown whether ERK activation during sleep is necessary for ODP consolidation. We investigated the role of ERK in sleep-dependent ODP consolidation by inhibiting the ERK-activating enzyme MEK in V1 (via U0126) during post-MD sleep. ODP consolidation was then measured with extracellular microelectrode recordings. Western blot analysis was used to confirm the efficacy of U0126 and to examine proteins downstream of ERK. U0126 abolished ODP consolidation and reduced both phosphorylation of eukaryotic initiation factor 4E (eIF4E) and levels of the synaptic marker PSD-95. Furthermore, interfering with ERK-mediated translation by inhibiting MAP kinase-interacting kinase 1 (Mnk1) with CGP57380 mimicked the effects of U0126. These results demonstrate that ODP consolidation requires sleep-dependent activation of the ERK-Mnk1 pathway.

Monovisión con lente intraocular monofocal en pacientes présbitas / Monovision with monofocal intraocular lens in prebyopic patients

OBJETIVO: Describir los resultados refractivos obtenidos mediante la cirugía del cristalino en pacientes présbitas hipermétropes y miopes con monovisión. MÉTODOS: Se realizó un estudio descriptivo, prospectivo, longitudinal con 21 pacientes, 13 miopes y 8 hipermétropes sometidos a cirugía del cristalino para corregir la presbicia con el método de la monovisión en el Servicio de Microcirugía del Instituto Cubano de Oftalmología Ramón Pando Ferrer entre febrero del 2009 y febrero del 2010. Las variables utilizadas fueron: agudeza visual con corrección preoperatoria y posoperatoria y sin ella, lejos y cerca, y equivalentes esféricos. Se utilizó la media y desviación estándar para presentar la información. RESULTADOS: En el preoperatorio la agudeza visual promedio mejoraba de un valor de 0,7 y 0,9 corregida para miopes e hipermétropes respectivamente a 0,88 y 0,94 de agudeza visual binocular sin corrección para estos mismos grupos en el posoperatorio, corrigiendo de esta manera equivalentes esféricos promedios de -8,27 D y +6,26 D en cada grupo. La agudeza visual cercana promedio para ambos grupos fue de Jeager 2 y los equivalentes esféricos promedios alcanzados para visi¾n lejana fueron de -0,32 D para miopes y +0,26 D para hipermétropes; en visión cercana, o sea, en el ojo no dominante es de -1,6 D para el primer grupo y -1,3 D para el segundo grupo. CONCLUSIONES: Se halló mejoría indudable de la agudeza visual sin corrección tanto para la visión lejana como para la cercana después de la cirugía. Los equivalentes esféricos fueron ampliamente modificados para ambos grupos tanto en los ojos dominantes como en los no dominantes para facilitar el resultado visual en ambas distancias. Los resultados obtenidos corroboran que la monovisión produce un mayor beneficio en la visión cercana que el perjuicio que provoca en la visión lejana lo que la hace muy exitosa para cierto grupo de pacientes

OBJECTIVES: To describe the refractive results achieved in presbyopic patients, both hyperopic and myopic, with monovision METHODS: A prospective, longitudinal and descriptive study was carried out in 21 patients, 13 myopic and 8 hyperopic, who underwent lens surgery to correct presbyopia based on the monovision procedure at the Microsurgery Service of the Ramón Pando Ferrer Cuban Institute of Ophthalmology from February 2009 to February 2010. The variables were pre and postoperative visual acuity with/without correction, both near and distant, and spheral equivalents. Mean and standard deviation values were used to present all variables. RESULTS: It was found that average visual acuity with correction improved from 0,7 and 0,9 in myopic and hyperopic patients respectively to 0,88 and 0,94 of binocular visual acuity without correction in the postoperative phase, thus correcting their average spheral equivalents of 8,27 diopters (D) and +6,26 D in each group. The average visual acuity for near vision for both groups was Jeager (J) 2 and the average spheral equivalents reached for distant vision were -0,32 D for myopic and +0,26 D for hyperopic patients. For near vision, i.e. in the non- dominant eye, the spheral equivalent values were 1,6 D for the first group and 1,3 D for the second group. CONCLUSIONS: After surgery there was an undoubted improvement in visual acuity without correction, in near as well as in distant vision. Spherical equivalents were widely modified for both groups in both the dominant and the non-dominant eye, improving vision at both distances. The achieved results corroborate that the benefits brought about by monovision in near vision are more important than the damages it causes in distant vision, making it very successful for certain groups of patients

Mountains and valleys: binocular rivalry and the flow of experience.

Binocular rivalry provides a useful situation for studying the relation between the temporal flow of conscious experience and the temporal dynamics of neural activity. After proposing a phenomenological framework for understanding temporal aspects of consciousness, we review experimental research on multistable perception and binocular rivalry, singling out various methodological, theoretical, and empirical aspects of this research relevant to studying the flow of experience. We then review an experimental study from our group explicitly concerned with relating the temporal dynamics of rivalrous experience to the temporal dynamics of cortical activity. Drawing attention to the importance of dealing with ongoing activity and its inherent changing nature at both phenomenological and neurodynamical levels, we argue that the notions of recurrence and variability are pertinent to understanding rivalry in particular and the flow of experience in general.

Distribution of calbindin-28kD and parvalbumin in V1 in normal adult Cebus apella monkeys and in monkeys with retinal lesions.

Several proteins have their normal patterns of distributions altered by monocular visual deprivation. We studied the distribution of the calcium-binding proteins calbindin-28kD (Cb) and parvalbumin (Pv) in V1 in normal adult Cebus apella monkeys and in monkeys with monocular retinal lesions. In normal monkeys, the interblobs regions in layers 2/3 and the layer 4B are intensely labeled for Cb, while Pv reaction showed a complementary labeling pattern with a stronger staining in layers 4A, 4C and in the blob regions in layers 2/3. In monkeys with monocular retinal lesion, the laminar distribution of these proteins was differentially affected, although both reactions resulted in stronger labeling in non-deprived ocular dominance columns. While Cb reaction resulted in stronger labeling in layers 1 through 5, Pv labeling was heavier in layers 2/3, 4A and 4C. There was a clear reduction in the intensity of neuropil staining for both Pv and Cb in deprived ocular dominance columns with little or no reduction in number of labeled cells. This reduction could thus be attributed to activity-dependent changes at synapses level.

Absence of binocular summation, eye dominance, and learning effects in color discrimination.

We evaluated binocular summation, eye dominance, and learning in the Trivector and Ellipses procedures of the Cambridge Colour Test (CCT). Subjects (n = 36, 18-30 years old) were recruited among students and staff from the University of São Paulo. Inclusion criteria were absence of ophthalmological complaints and best-corrected Snellen VA 20/20 or better. The subjects were tested in three randomly selected eye conditions: binocular, monocular dominant eye, and nondominant eye. Results obtained in the binocular and monocular conditions did not differ statistically for thresholds measured along the protan, deutan, and tritan confusion axes (ANOVA, P > 0.05). No statistical difference was detected among discrimination ellipses obtained in binocular or monocular conditions (ANOVA, P > 0.05), suggesting absence of binocular summation or of an effect of eye dominance. Possible effects of learning were examined by comparing successive thresholds obtained in the three testing conditions. There was no evidence of improvement as a function of testing order (ANCOVA, P > 0.05). We conclude that CCT thresholds are not affected by binocularity, eye dominance, or learning. Our results differ from those found by Verriest et al. (1982) using the Farnsworth-Munsell 100 Hue test and Hovis et al. (2004) using the Farnsworth-Munsell panel D-15 test.

Differential expression of Zif268 and c-Fos in the primary visual cortex and lateral geniculate nucleus of normal Cebus monkeys and after monocular lesions.

The transcription factors c-Fos and Zif268 have been used as markers of neuronal activity, and they also have been implicated in neuronal plasticity. In this study, we investigated the expression of c-Fos and Zif268 proteins in the lateral geniculate nucleus (LGN) and in the cortical primary visual area (V1) of normal adult Cebus apella monkeys and in animals with monocular lesions. In the LGN, the reaction for c-Fos showed immunopositive cells in both magnocellular (M) and parvocellular (P) layers; however, the label was heavier in P layers. In animals that suffered monocular lesions, the immunocytochemistry for c-Fos showed more labeling in layers related to the normal eye compared with those of the lesioned eye. No specific label was observed after the reaction for Zif268 in the LGN. In V1, the reaction for both Zif268 and c-Fos showed a pattern of lamination in which heavier labeling was found in layers 2/3, 4A, 4C, and 6. After monocular lesions, we observed a clear pattern of ocular dominance columns in V1 for both c-Fos and Zif268, in which the columns related to the normal eye are more heavily labeled than those related to the lesioned eye. This pattern is more evident in layer 4C after c-Fos reaction, whereas, after Zif268, it is more clearly observed in layers 2/3. These results suggest that, in addition to be regulated by functional activity, these transcription factors are involved in different processes during cortical reorganization.

Effects of the Amazonian psychoactive beverage Ayahuasca on binocular rivalry: interhemispheric switching or interhemispheric fusion?

An early theoretical analysis supposed changes in hemispheric integration as the basis of altered state of consciousness induced by psychoactive drugs. Brain imaging studies revealed right cortical activation after administration of hallucinogens. Recent studies on binocular rivalry suggest that interhemispheric switching is the neural substrate of the perceptual oscillations observed during dichoptic stimulus presentation. The current study tested perceptual alternation in ceremonial participants, who ingested the South American hallucinogenic beverage ayahuasca, to examine the claim that there might be changes in interhemispheric function under the influence of hallucinogens. Ingestion of ayahuasca resulted in a decrease of rivalry alternation rates, increased length of one percept and there was evidence of phenomenal fusion. The findings are in line with results of brain activation studies and support the concept of interhemispheric fusion in altered states of consciousness.