RESUMO
Presbyopes show that for targets presented within a 28 degrees clear field of view, gaze is accomplished by head and eye movements with head movements making an average contribution of 24%. A clear field of view which incorporates the factor of segment width provides an underestimation because of the factor of head movements. By including the effect of head movements, a fixed segment width provides a much wider clear field of view which we term the usable field of view.
Assuntos
Óculos , Fixação Ocular , Cabeça , Movimento , Óptica e Fotônica , Presbiopia/terapia , Movimentos Oculares , HumanosRESUMO
The initial stages of light and dark adaptation in the human visual system cannot be explained by a simple relation between sensitivity and pigment bleaching. We found changes in sensitivity in the goldfish ganglion cells similar to those seen in humans, and our results from experiments suggest that a change in gain, rather than an overloading of the ganglion cell activity, is responsible for the sensitivity loss. Furthermore, long wavelength background lights selected to stimulate only the long wavelength receptor mechanism produce only the early sensitivity changes in the medium wavelength cone mechanism being monitored at the ganglion cell. This suggests that the early gain changes occur due to neural interaction where different receptor signals merge.
Assuntos
Percepção de Cores/fisiologia , Retina/fisiologia , Adaptação Ocular , Animais , Adaptação à Escuridão , Carpa Dourada , LuzRESUMO
The EOG ratio is an established clinical test of retinal function. Since its development by Arden and coworkers in 1962, it has been thought of as simply a rod-medicated response. Using scotopically matched red and blue lights, we found a 24% larger response to the red light than to the blue light, establishing that a cone contribution exists in the EOG ratio of normal subjects.
Assuntos
Eletroculografia , Células Fotorreceptoras/fisiologia , Cor , Adaptação à Escuridão , Humanos , Luz , Estimulação Luminosa/métodosRESUMO
The evaluation of 116 normal ratios with a 10 ft. lambert ganzfield illumination confirmed that ratios over 200% can be considered as normal. Individual variation led to the proposed classification of 175% to 200% as being low or suspicious. Ratios below 175% are abnormal and are useful in establishing the diagnosis of pathology.
Assuntos
Eletroculografia , Doenças Retinianas/diagnóstico , Adolescente , Adulto , Idoso , Animais , Criança , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Células Fotorreceptoras , Coelhos , Retinose Pigmentar/diagnósticoRESUMO
At threshold the eye is known to sum quanta as though the total catch were important and not the distribution on the retina. In humans, spatial summation is larger under dark adapted conditions. The extent of this spatial summation is studied in goldfish retinal ganglion cells which are known to receive both rod and cone inputs. The area of summation in single ganglion cells is found to be much larger for rod input compared to cone input. It seems that in single ganglion cells, the spatial summating properties increase markedly in the dark due largely to the neural organization of rod and cone input.