Spatial Localisation and Visual Direction Flashcards
(22 cards)
What is oculocentric vision?
Oculocentric vision refers to the visual direction each eye has relative to its own retina, with the fovea corresponding to the principal visual direction.
What is local sign in terms of vision?
Local sign refers to the unique visual direction each point on the retina has relative to the fixation point. It enables us to distinguish objects based on their retinal location.
What is egocentric vision, and how does it differ from oculocentric vision?
Egocentric vision is the perception of the world from the perspective of an imaginary cyclopean eye, which represents the fused visual information from both eyes. It differs from oculocentric vision, where each eye perceives its own retinal location of visual direction.
What is the cyclopean eye, and what role does it play in binocular vision?
The cyclopean eye is an imaginary point located between the two foveae, used as the center for binocular visual direction in egocentric vision. It helps in combining visual information from both eyes into a single perception.
What are corresponding points in binocular vision?
Corresponding points are retinal locations in each eye that, when stimulated by the same object, result in the perception of a single image. These points are necessary for binocular single vision.
What is the law of identical visual directions?
The law of identical visual directions states that if an object stimulates corresponding points in both eyes, the object will appear to be located in the same visual direction in both eyes, resulting in binocular single vision.
What is the horopter, and how is it defined?
The horopter is the locus of points in space where objects will fall on corresponding retinal points in each eye, resulting in binocular single vision. The horopter is typically represented by the Vieth-Müller circle.
What is the Vieth-Müller circle, and how does it relate to the horopter?
The Vieth-Müller circle is a theoretical circle that passes through the nodal points of both eyes and the fixation point. It is often used to represent the horopter, assuming perfect ocular symmetry.
What is Panum’s Fusional Area?
Panum’s Fusional Area is the region on the retina where the eyes can still achieve binocular single vision despite slight misalignments. Objects within this area are fused into one image, while objects outside this area lead to physiological diplopia.
What is physiological diplopia?
: Physiological diplopia occurs when objects fall outside of Panum’s Fusional Area and stimulate disparate retinal points in each eye, causing double vision. This is a normal phenomenon and occurs in peripheral vision.
What are disparate points in the context of visual direction?
Disparate points are retinal locations in each eye that do not correspond to each other, leading to physiological diplopia when stimulated by the same object outside of Panum’s Fusional Area.
What is the relationship between vergence and fusional reserves?
Vergence is the movement of both eyes in opposite directions (convergence or divergence), and fusional reserves refer to the ability of the eyes to maintain binocular single vision when subjected to misalignment. The eyes use fusional reserves to adjust vergence and compensate for disparities.
What is the difference between crossed and uncrossed diplopia?
Crossed diplopia occurs when objects are located in front of the horopter, and the images appear to be crossed.
Uncrossed diplopia occurs when objects are located behind the horopter, and the images appear uncrossed.
What is ocular dominance, and how is it determined?
Ocular dominance refers to the tendency for one eye to be more involved in visual processing and control, leading to better acuity and precision in that eye. It can be determined using tests like the hole-in-card or pointing tests
What is Panum’s Fusional Space, and how does it relate to binocular vision?
Panum’s Fusional Space is the three-dimensional region around the horopter where objects can be seen as fused in binocular vision. Beyond this space, physiological diplopia occurs.
What is the significance of crossed and uncrossed diplopia in terms of vergence?
Crossed diplopia occurs when an object is within Panum’s Fusional Space and the eyes converge too much (towards the nose), while uncrossed diplopia occurs when the object is outside the fusional area and requires the eyes to diverge (moving outward).
What are the clinical implications of physiological diplopia?
Physiological diplopia helps us understand how the visual system copes with slight misalignments, but it also highlights how precise binocular alignment is necessary for tasks like reading, driving, and sports. Treatment may involve vision therapy or prism glasses for those with convergence or divergence issues.
How does the concept of the cyclopean eye help in visual localization?
The cyclopean eye represents a fused visual system, combining input from both eyes and forming a unified perceptual direction. It plays a crucial role in determining how we localize objects in space based on the visual direction from both eyes.
What is vergence adaptation and its importance in binocular vision?
Vergence adaptation refers to the eyes’ ability to adjust their vergence movements to maintain binocular single vision in response to changes in the visual environment, such as shifts in fixation or object distance.
What is the role of vergence in maintaining binocular single vision (BSV)?
Vergence movements are essential for aligning both eyes and ensuring that corresponding points in each retina are stimulated. These movements allow the brain to fuse the visual input from both eyes into a single image, resulting in binocular single vision.
What does the concept of corresponding points explain about binocular fusion?
Corresponding points explain how the visual system merges the images from both eyes into one, allowing for binocular fusion and a single unified perception of the world. This process is critical for maintaining stable and clear vision in both eyes.
How is physiological diplopia used to test the quality of vergence?
Testing for physiological diplopia helps assess vergence function by determining the limits of Panum’s Fusional Area. The ability to fuse images without double vision (diplopia) is a key indicator of normal vergence.
