So, What Has Vision Done For Me Lately? Prepared for ICBO Ontario, CA By: R. A. Hohendorf OD April 2010
Why do we need vision? We need vision for two quite different but complementary reasons We need vision to give us detailed knowledge of the world beyond ourselves knowledge that allows us to recognize e things from minute to minute and day to day We also need vision to guide our actions in that world at the very moment they occur
Definition Of Vision Vision is the deriving of meaning and direction of action as triggered by light It is our dominant sensory system It is a pervasive process of the human being It is not accommodation, convergence, depth perception, visual closure, eyesight, visual acuity nor visual fields These are some parts of the visual process Vision is more than the sum of its parts
A Communication Tool Principles Supported By Modern Neuro-Science
Vision as an Emergent An emergent is more than the sum of its parts Vision is not the only emergent Vision is a continuum in constant flux Visual memory is our past Eyesight is the present Visual imagery is the possibilities of the future
Parts The problem with looking at parts and reductionist thinking Clock example (thank you Rob Lewis) Vision in particular is very difficult to look at parts and understand d in its complexity Vision is an Emergent
Interesting Visual Perspectives We sample things visually at 3-5timesper second yet our perception is constant We see things after they have happened The power of visual imagery and anticipation Visual motor skill exception
Anticipation Experiments that have tested people s reaching and grasping under monocular viewing conditions have shown that the reaches are much slower, more tentative and less accurate than the same movements made under normal binocular viewing conditions. It is binocular information that allows us to make grasping movements that are calibrated correctly for distance and tailored to the real size of the object.
Binocularity and Grasping Our hand and fingers adopt the final posture of the grasp well before we make contact. At about 2/3rds the way to the object begin to close in on the object.
A Review Of The Visual Pathway (The Parts) Known Pathways Magnocellular and Parvocellular Pathways Visual Attention ti Metrics
Visual Pathways
Magno and Parvo Two types of retinal cells that send input to the brain Magno Fast Large receptive fields Motion detection Mid brain and posterior parietal projection
Magno and Parvo Parvo Slower (relatively speaking) Smaller receptive cells Color V1 projection Tiling Concepts
Rod and Cone Retinal Distribution
M & P Cell Absolute Densities in the Retina From E.Hussey JBO Vol 14/2003 Speculations on the nature of visual motion optometric implications
Magno and Parvo Myths Rod and Cone myths: All magnocellular cells are rods All parvocellular cells are cones Central and Peripheral Vision myths: All central visual field cells are cones All Peripheral visual field cells are rods Dorsal and Ventral Pathway myths: All magnocellular cells are dorsal stream cells All parvocellular cells are ventral stream cells
Visual attention We cannot attend to everything we see all the time (most likely at any time) We select an area of space from which to derive meaning and direct action Some anatomy figures 10% of V1 input is from the eyes More V1 connections from RAS than from eyes Feed forward connections
Measuring things Metrics In inches, feet, meters, cubits The problem with where is the metric of the brain is not in societal terms Visual metrics Any of the above? Seems to be anthropometric units Specifically the body part(s) related to produce the range and facility of movement to perform an activity
Metrics The use of scene-based metrics means that the brain can construct this representation in great detail without having to compute the absolute size, distance and geometry of each object in the scene.
A Universal Yet Different Metric Parietal lobe Center of Spatial map End of Dorsal pathway Seems to broadcast to various other brain motor areas so we can use hands, feet, or any other body part as the current metric Necessary to perform the desired action gracefully
Why two systems? Visual perception p is there to let us make sense of the outside world and to create representations of it in a form that can be filed away for future reference. In contrast, the control of a motor act requires accurate information about the actual size, location, and motion of the target object. This information has to be coded in the absolute metrics of the real world.
Why Two Systems? The dorsal stream works in real time and stores the required visuomotor coordinates only for a very brief period at most for a few hundred milliseconds. The ventral stream, on the other hand, is designed to operate over a much longer time scale.
The visuomotor system is largely isolated from perception. Its modus operandi seems to be to disregard information from much of the scene when guiding goal-directed movements like grasping, restricting itself to the critical visual information that is required for that movement. The visuomotor system works in real time. When a delay is imposed, perception intrudes. And if perception is influenced by an illusion so is the delayed movement.
Where Does The Visual Developmentally Optic pit Process Start? Eyes migrate ga from brain ba to forward adpo position o In real Life Use The eye? More specifically the retina? The retina is a piece of brain exposed to light in a mobile container There is at least one more probable possibility
Vision Starts Where? The dilemma of where to look first (next)? Implies the brain starts the visual process Based upon what information it needs (next) The visual process is a never ending sensory motor cycle Once started we want to see the next part Putting meaning to what we are seeing is a cycle there is no consistent start or stop points
Let s Make A Deal The eyes and brain have a contract The brain agrees to accept what the eyes send it.. as long as The eyes agree to look where the brain wants them to look next. Feed forward and feedback loops are set up which are essential components for learning to move with grace
How The Crux Of The Matter How is a new concept introduced to me by Greg Kitchener OD. Originally the descriptions of ventral and dorsal streams were in terms of what and where. It was Karl Pribram who first pointed out that t the difference, based on the experimental conditions, was better described as what and how how.
How It is important to realize that the "what" aspect is strongly linked to a verbal naming What about Where? Its metric is variable What is it linked to?
How Also, there is an Optometric attachment to the term where Where am I? where is it? In thinking about Pribram's suggestion of how it occurred to Greg Kitchener that the coordinates for a "where" e system were e dependent on how Expressing where is something is based upon how you will interact with it
Outside Optometry Cognitive Neuroscience seems to be working on many issues that we would consider visual In my neuroscience readings the how concept and terminology are common They seem to be zeroing in on the point that the brain processes information in order to figure out: HOW
Goodale and Milner stated: The modularity in the dorsal stream is based not on the particular visual features that are being extracted from the visual array so much as on the nature of the actions guided by vision. These actions include things like reading; saccadic (quick) eye movements; pursuit (slow) eye movements; grasping with the hand and whole-body locomotion.
Thinking Aloud Walking, reaching, driving or putting in an eye wire screw all have different coordinate (metric) systems based on the different natures of the interactions The basis in each case is ourselves and our abilities (as extended by tools) And the nature of the interaction In each case our "where" response depends d on "how
Intention The Nature Of The Interaction How we pick up a pencil to write vs. throw is dependant on how! The object (or tool) and our intentions are an integral part of how This incorporates: Body schema knowledge Motor planning Motor action Motor Feedback Gee! Also they are also parts of Visual Development and the Visual Process.
Thinking Aloud I understand that "where" seems more intuitive and obvious, but I suggest that this is because we tend to assume the "how" so strongly that how tends to become transparent This has tended to conceal the fact that the coordinates of "where" are not constant
Practicality We are constantly interacting with our environment. That interaction or planned interaction is always based upon the question HOW? HOW do we decide; Where am I?, Where is it?, What is it?, Who should I share this with? (The traditional 4 circles)
More Global - More Practical HOW is it we (decide to) choose a portion of space from which to derive meaning or direct action? HOW is it we (decide to) use ourselves to accomplish anything? To interact with our world in any way? HOW HOW is constant in our lives! HOW is what drives and literally moves us HOW
How How How can I do this? How can I get that done? The fundamental question HOW? is a dynamic, life long quest of our brains and db bodies. HOW drives our development and for Optometric purposes it drives the use and development of the visual process. HOW
So What? Most research is now shifting from where is it to acting upon objects. The traditional way we look at vision amongst ourselves is not the way the rest of the world is looking at it Not only is the eyesight vs. vision concept (we hold so dear) not acknowledged d by others, the purpose and action of vision as we know it is hidden as well
Opportunity I propose a uniting concept Instead of thinking acuity, phorias, ACA, VIP, think about these as part of the logistics of How If we think of the ways vision i helps us figure out and execute How, it will change our ability to communicate more effectively the role the visual process plays in living life
Application Specifically: How we communicate with others about the value of vision How we look at the services and materials we offer our patients How Optometry is in a unique position to help patients
Application Clinically it can also help understand and explain: The tests we use and how we interpret them Retinoscopy was shown to be related to patient interaction by Dr s Ilg, Getman, Streff at the Gessel Institute for Childhood Development/Yale as early as mid 1940,s Strengths and weaknesses of standardized testing
Application Lenses and their effect on the visual process Why patients respond differently to the same lens It not what a lens does to the patient it s what the patient does with the lens The visual process and its relationships to behavior Motor Changes and all the other different changes seen in patients t with Optometric treatment options
Application And Opportunity In Summary it helps us determine: What we can do to help patients when their vision i is interfering i with HOW they do their daily activities!!
Thank You! For your attention And for the opportunity to present to you at the 2010 ICBO