Dear Bud,
Having only one eye affects the ability to aim, read, and perceive distance. Let me address these issues separately. Then I address mechanics to help one-eyed golfers.
I. AIMING
In terms of sighting lines, the fact that you have only one good eye is a positive help, as this eliminates possible problems from eye dominance (there is no "dominance" when there is only one eye in use).
II. READING
Perceiving Basic Flat Surfaces: Texture Gradient and Visual Perspective to Surface
In terms of reading the surface contour and the distance of the putt, having one eye can be a detriment because it takes two eyes to generate a sense of depth and to generate "disparity" cues between the retinal images of one eye versus the other looking at the same place or object. Reading the surface is in large part appreciating how the curvature of the surface affects the perspectival diminution of surface detail ("texture gradient") as the distance increases. Oddly enough, this is not particularly a two-eyed process. If you stand at one end of a long hall with a checker pattern carpet running its length, the lines of the walls and ceiling and floor converge in perspective at the far end of the hallway, and the checks appear smaller with increasing distance in a very regular way. This perspective and this diminution pattern of the apparent size of the checks does not really require two eyes to perceive, and looking at this with one eye is sufficient to perceive that the floor is flat and how far off the end of the hall is.
The above views depend upon the position of your eyes relative to the surface and the direction of the gaze, and the above views have eyes where an adult standing in the hallway would have eyes (about 5 feet above the floor beneath the feet) with the gaze more or less horizontal to the floor looking at the wall at the end of the hallway 5 feet above the floor and not gazing down at some specific part of the floor (e.g., halfway down the floor). This of course is the dominate perspective for viewing a green, except for the fact that greens are not level like a floor.
Here is a perspective looking straight down at the surface beneath the feet:
Here is a perspective looking down a hill onto a surface that levels out past the bottom of the hill:
Here is a general side-by-side comparison of the texture gradient as seen straight-down and from an oblique angle:
I imagine that "depth perception" might strengthen the sense of distance, but the vanishing point effect of the perspective does not really need this depth perception to register distance. The diminution of the checks does not need depth perception at all.
Here is an illusory hallway designed in the Renaissance:
"An even more impressive illusion was achieved in the Palazzo Spada, where the architect Francesco Borromini designed a columned passage to appear 35 meters long when it was in fact just 8 meters in length: The floor of the hallway slopes upward, and the ceiling and walls converge. Even the "hedges" at the end of the hall are miniaturized, as is the sculpture in the center. Unfortunately the museum didn't let visitors walk up the hallway for action photos, so I had to generate this picture from a postcard after the fact." (From Dave Munger, Euro-update 3: Don't mess with perspective, Cognitive Daily, 13 june 2007.)
One of the hidden cues in perceiving flat surfaces over distance is the relationship of the horizontal to the vertical, as in floor to wall. The floor is only "level" when all points on the floor are the same distance below a given height on the wall (assuming the walls are perpendicular to the IDEAL floor plane).
Here are laser devices to check the level of the floor:
On the golf course, this translates into using background references, like trees and buildings and lake surfaces to get a reference comparison of vertical-horizontal to apply to the green surface. Here the flag stick and trees serve as good indicators of true vertical:
Perceiving Contour Changes: Texture Gradient, Background Scenery, Shading and Perspective
The next stage is to note how perception of contour change differs from flat surfaces. Here is a wrinkled carpet:
Note how the converging lines indicate the fold, as seen in this simple drawing:
Here is a more general depiction of the texture gradient pattern when the surface contour has a wrinkle like this:
Note the different visual perspectives of the above two views. The straight-down view does not benefit much if at all from the surrounding frame of reference, whereas an oblique perspective has the background reference (similar to walls in the hallway).
Views from the fairway give good background scenery cues to contour, slope and slant. This scene at Royal Melbourne (with a slight uphill from the fairway perspective) has a very straight vertical flag stick and a very straight horizontal line across the sky where the blue sky divides from the white sky:
Here is another view where the regularity of the color gradient of the sky (blue highest changing to lighter blue closer to the surface) helps disentangle background-foreground conflicts.
This fairway perspective of a rolling green looks very similar to the carpet with folds. The perception of the contour also benefits from the background scenery and the light-shade aspect of the surface, with tops light and downslopes shaded. Note how the flag stick and the general uprightness of the trees coincide vertically.
The distant fairway margin behind the green indicates a left-right uphill (high side on the right). This contrasts with the general top of the green left-right at the flag stick showing a slight downhill slant left-right (low side on the right). A true horizontal reference (and derivatively a true vertical reference) allows this comparison and judgment. (This would all be more lifelike if the picture were enlarged to the point that there was no picture frame like a box visible. That's cheating.)
The light-shade contrasts on this surface also indicate contour shape:
In general, shading indicates slant and more specifically concavity and convexity (bumps, lumps, hillocks, depressions, bowls, etc.):
Perceiving Contour Changes: Slant / Fall Line Orientation
The basic orientation of a sloped-but-flat surface indicates the relationship between the surface and gravity. The "fall line" thru a cup on the green, the straight-uphill and straight-downhill direction of the surface, is the local orientation of the flat-but-tilted area around the hole. Greens typically have a generalized "fall line" for the green surface taken as a Gestalt whole. This broader perspective up away from the local area (which is more of a straight-down view) comprehends the fringe line of the green. The fringe helps define an overall uphill-downhill orientation. By standing at the lowest elevation on the fringe of the green and looking across the green to the highest elevation along the fringe, the golfer perceives this generalized uphill-downhill orientation of the green as a whole. The local fall line at the cup is typically not too far off this overall fall line orientation.
The local fall line is always perpendicular to the equal-elevation "contour lines" of a contour map of the green. The small arrows below indicate fall lines, and the contour lines indicate equal-elevation points along the surface.
Fall lines correlate with the underground drainage features of the green complex. Here are typical drainage patterns using the "herring bone" collection into a central off-ramp:
Some areas of greens have poor drainage and after a good rain, these depressions are revealed:
Perceiving Contour Changes: Graphic Representations of Surface Shape
All representations of surface shape are elaborations on the texture gradient and the perspective as discussed above, plus grids (check patterns), contour equal elevation lines, fall lines, and 3D effects such as shading and slice-of-earth platforms.
Augusta National's 14th green animation.
These contour and fall line maps are no different:
There are other features available for green reading as well.
Perceiving Contour Changes: Mow Stripes
Greens are always mowed in parallel stripes, first one direction and then the opposite direction, alternating across the green. The direction of the stripes is varied daily by the Greenkeeper so as to avoid training the green to a rigid grain pattern. Down the mow stripe, the mower lays the grain down. So mow stripes mix up the grain and tend to neutralize grain over the course of weeks or months, but on any give day, the grain slightly follows the mow direction.
Mow stripes don't ordinarily coincide with the overall green fall line, but are oriented athwart the fall line. That's okay, so long as you don't let the mow stripes have too dominate a role in influencing your perception inaccurately.
The crisscrossing mow stripes on this green reveal the folds of the contour:
The converging lines show the upsloping hill to the flagstick, where the top has a light appearance. The stripes near the closest fringe also reveal bends in the contour.
This green faintly indicates the mow stripes:
Perceiving Contour Changes: Feet and Balance and Sense of Upright
The human internal system for knowing surface contour uses the inner ear (vestibular) organs, the proprioception of balance in gravity especially in the feet, and the visual sense of orientation to the far horizon of the scenery. Other cues feed into this basic internal system.
This system is how human's walk, by catching themselves from falling after leaning forward.
The same system underlies the movement of the Segway transporter: the person leans forward and the Segway detects the imbalance with gyroscopes and then commands the tires to wheel the Segway forward at just the right speed to "catch" and counteract the falling, so the lean is all you get and the Segway rolls along.
Segway lean initiates wheel rolling
German Polezei showing that good posture is required to keep the Segway stationary for a publicity photo -- the Segway trains good posture!
Rolling along with the Segway means keeping the good skeletal alignment and only "leaning" the whole body, not bending forward, so the only angle that really changes is in the ankle joint mediating the plantar and the legs.
Ankle joint changing
Standard gait in walking features nonconscious ankle proprioception as the stable base for upright walking:
The pressure on different parts of the sole of the feet changes during the gait and also during walking upon level or contoured surface, as the body reacts to stay in balance in gravity.
The instincts have excellent correlations between ankle angle and lean. When standing on a hill facing uphill, the plantar conforms to the tilt and this without lean will mislocate the body's center of gravity backwards and cause the person to fall backwards downhill, so the person leans forward into the hill to maintain balance and equilibrium, resulting in an ankle angle that perfectly matches the tilt of the hill. Hence, the ankle proprioception directly corresponds to slope in gravity.
Facing uphill, leaning the body's COG forward places more weight on the balls of the feet. Facing downhill, the body reacts by leaning backwards to rebalance the COG, and this places more weight above the heels. Standing on a sidehill down to the right, the body reacts by righting itself in gravity leaning uphill to the left, and places greater weight above the left edges of the feet, and vice versa for a leaning uphill to the right.
Leaning forward facing uphill
Leaning back facing downhill
Leaning uphill to the right
Leaning uphill to the left
Walking in a circle around on the green surface (or a general flat but tilted area of the green) indicates when the body and ankles are at the top and bottom of the tilted circle, as here ONLY leaning onto the edges is invloved (6 and 12 on the clockface, with the 6-12 line thru the cup being straight uphill-downhill). At the point in the circle when the person faces straight uphill or downhill, ONLY extra pressure on the toes / balls of the feet and heels is involved (3 and 9 on the clockface).
Perceiving Contour Changes: Visual Acuity Near and Far of Texture Detail
Reading a green surface contour is perceiving the pattern of change of the characteristic surface detail features. In the case of a checkerboard, the detail is a check. A checkerboad that tilts top-towards the person's face and eyes has less diminution of detail size with increasing distance than does a checkerboard laying flat on a table viewed from an oblique angle. In the case of a green, however, the characteristic detail is the grass blade or small patch of grass. This Bermuda green has a fairly large surface detail pattern:
Aerated greens have grossly larger detail patterns more closely conforming to a checkerboard pattern or a pegboard pattern:
The more uniform and homogenous the grass surface, the finer the characteristic detail, as in Augusta National in May:
14th Green at Augusta National, with "speckle" pattern of light and dark contrasts approximately 1/16th or so in diameter.
Human visual acuity is typically measured in terms of the Snellen chart at 20 feet, with normal eyesight defined as the ability to discriminate two points in space as separate from that distance. This separation is very small as an angular separation. "In the term "20/20 vision" the numerator refers to the distance in feet from which a person can reliably distinguish a pair of objects. The denominator is the distance from which a person with standard VA would be able to distinguish them--the distance at which their separation angle is 1 arc minute." (
Wikipedia, Visual acuity.) The minimum angle of resolution (MAR) is taken to be 1 minute of arc for a normal person. (See
Psychophysics of Vision: Visual Acuity, by Michael Kalloniatis and Charles Luu, Webvision, University of Utah.) An "arc minute" is 1/60th of one degree of angle. At 20 feet, this is a gap of about 1/32nd of an inch.
If the grass detail at Augusta National is at most 1/16th of an inch, the human ability to discriminate detail at 20 feet is two times greater than required (1/16th an inch has two sections 1/32" in width). At 40 feet, however, the ability to discriminate 1/16th-inch detail is lost, as acuity at this range is two times less than at 20 feet, so "all cats are gray in the dark" and the green surface at 40 feet looks like an homogenous detail-less green color. For the vast majority of golfers, the surface detail of a finely manicured and homogenous green disappears at the range somewhere just past about 40 feet.
The same thing can be observed looking at the tiny print in a phone book or newspaper. The publishers know how small the typeface can be made to save space and expense and cram content on a single page before human visual acuity gives out, so the type size is already near the limit of acuity. This means that if you find a tiny letter "i" and focus on the gap between the stem and the dot, and then extend the page outward farther from the eyes slowly, a distance arrives where the letter "i" morphs into the letter "l" as the ability to discriminate the gap disappears.
For this reason, people who have Lasik surgery get a boost reading greens. Their visual acuity at distance is improved, sometimes dramatically, and this enhances the ability to perceive changes in detail texture with greater precision throughout a wider swath of the surface. This "broader" area gives better understanding or appreciation of local contour in context. The result is a more accurate read of shape. (This boost ameliorates over time, however, as the person grows accustomed to the better visual detail.) many PGA Tour players have exceptional visual acuity, and this helps their green reading.
Perceiving Contour Changes: More on Perspective
Whenever the distance to the end of the putt outstrips the comfort zone of a golfer's visual acuity for surface detail discrimination, the golfer would be well served to walk over to the far end of the putt for a closer examination. Walking while looking somewhat obliquely into the green is probably better and more informative than looking more or less straight down. Similarly, the golfer is better served looking "up" into the green contour from the low side than looking downhill: the informational richness of looking at a checkerboard tilted towards the face rather than one tilted away from the face is obvious. Even so, the golfer wants to maintain a reasonable obliqueness in the perspective when looking uphill, and this often means not getting too close to the anticipated path of the putt, but standing downhill from the path, usually in the vicinity of 4-6 feet downhill.
It is also a good idea to split the putt in half left-right and then stand below the path at a point on an equilateral triangle. For a 20-foot putt, this point is 10 feet along and 17 feet downhill. From this point, the direct line from golfer to ball is 20 feet, the direct line from golfer to hole is 20 feet, and the length of the putt from left to right is 20 feet. For a 10-foot putt this point is 5 feet left-right and about 8 feet downhill from the path.
Standing behind the ball or standing behind the hole similarly requires an optimal separation back from ball (or hole) to see ball and path and hole (or to see hole and path and ball, from behind the hole) at once without having to shift the head up and down from one to another. This distance for most adults standing upright is at least 5-6 feet. "The normal human visual field extends to approximately 60 degrees nasally (toward the nose, or inward) in each eye, to 100 degrees temporally (away from the nose, or outwards), and approximately 60 degrees above and 75 below the horizontal meridian. In the United Kingdom, the minimum field requirement for driving is 60 degrees either side of the vertical meridian, and 20 degrees above and below horizontal. The macula corresponds to the central 13 degrees of the visual field; the fovea to the central 3 degrees." (
Wikipedia, Visual Field.) The normal "resting state" of vision has the eyes angling down out of vertical around 30 degrees. Combined, this "natural" viewing angle takes in an "away from the feet as the body faces forward" direction starting around 50 degrees down from horizontally level from the eye height and continuing about 40 degrees "upward / farther along" from this. For a normal adult with eyes close to 6 feet above the ground, this near-point is about 5 feet away from the feet and the putt path is another 2-3 feet farther, with good vision 2-3 feet either below or above the path. So this perspective is roughly 8 feet downhill from the path for most people. (See also Heuer, H. and Owens, D.A. (1989), Vertical gaze direction and the resting posture of the eyes, Perception, 18, 363 ± 377; Hueur, H., et al. (1991), Preferred vertical gaze direction and observation distance, Ergonomics, 34, 379 ± 392; Mon-Williams, M., et al. (1998),
Gaze angle: a possible mechanism of visual stress in virtual reality headsets, Ergonomics, vol. 41, no. 3, 280 ± 285, citing mean downward angle of about 34 degrees but subject to individual variation for resting head position.) Gaze angles much above 30 degrees downward tend to inject some "esophoric" vergence, or depth fusion of target a little shorter than the actual distance to the target. (Id.)
Squatting and even adopting the "spider crawl" perspective behind the ball or behind the hole for examining the surface contour alters the available information depending upon the obliquity of regard.
Taken to extreme, getting the eyes the SAME level as the grass is tantamount to examining a checkerboard by holding it level with the pupils and looking only at the edge of the board. This can be done sometimes by stepping off the green downhill a bit to level the eyes with the surface:
Or the golfer can adopt the "spider crawl" posture of Camillo Villegas:
This has SOME informational value, as the exact shape of the surface is compared to background references. A flat surface looks like a horizontal line against the background, and a humped surface has a curved shape against a horizontal-vertical reference background, and a left-right sloped surface looks like a line tilted one side higher in relation to the background. Squatting at a certain distance back from the ball or hole can be done to provide a resting state gaze angle with a good near-far angle of obliqueness, but this limits the near-far range of the putt that can profitably be examined without excessive up-down eye gaze shifts of up-down head shifts between near and far. And too far out, the angle down to the surface is simply too oblique for meaningful detail. When squatting and using a standard 30-degree down resting gaze, the range of good vision starts about 2 feet away and runs for another 4 or so feet. Beyond this, the eyes and / or head must shift up-down to see a longer range. For a 10-15 foot putt, the golfer will typically raise his head a bit to take in the whole scene at once.
III. DISTANCE
Distance perception is a complex overlaying of perceptual processes, knowledge, and memory. All greens are about the same size. Typical PGA Tour greens are 6,000 square feet, and the courses with the smallest greens have greens averaging about 3,500 square feet. Augusta National greens average about 6,150 square feet. A circular shaped green this size would have a maximum linear distance across the diameter thru the center from one side to the other of about 45 feet, so most golfers can stand anywhere on such a green and still see almost all the far surface with some discrimination of detail. A more "kidney" shaped green of this area might be shaped more or less rectangularly with 120 feet x 50 feet or so. These shapes present a distinct possibility that the distance to the critical ending area of a putt is beyond human visual acuity. This is knowledge, either explicit or implicit, from having seen or played numerous courses. So all golfers of modest experience have a pretty good idea about distances of putts within a standard range of green sizes.
Golfers also remember their home greens about as well as they remember the layout of their living room in total darkness. The human brain maps familiar space and keeps these maps permanently in the hippocampus for ready reference. (See OÕKeefe J, Nadel L. 1978. The Hippocampus as a Cognitive Map. Oxford: Oxford University Press; Mizumori, S. J. Y. (2007). Hippocampal Place Fields: Relevance to Learning and Memory. Oxford Univ. Press; Mizumori, S. J. Y. (2006).
Hippocampal place fields: A neural code for episodic memory? Hippocampus, 16, 685-690;
Mizumori Lab, Publications, University of Washington) This is a memory-based understanding of distance.
During the round of golf, perception-based understandings of distance come at the golfer in a steady stream, from planning the first putt on the green reached in regulation to planning the approach shot from the fairway working backwards to planning the tee shot. There is also the stream of perceptions of green size and putt distance while walking up the fairway to the green, watching others walk about on the green, walking on the green to mark the ball and read the putt, and watching others putt and seeing how their putts arrive at the hole.
These perception processes are only partially dependent upon two eyes, and monocular cues to size and distance are more numerous and potentially more potent as well.
"
Monocular cues
Motion parallax - When an observer moves, the apparent relative motion of several stationary objects against a background gives hints about their relative distance. This effect can be seen clearly when driving in a car nearby things pass quickly, while far off objects appear stationary. Some animals that lack binocular vision due to wide placement of the eyes employ parallax more explicitly than humans for depth cueing (e.g. some types of birds, which bob their heads to achieve motion parallax, and squirrels, which move in lines orthogonal to an object of interest to do the same).
Depth from motion - A form of depth from motion, kinetic depth perception, is determined by dynamically changing object size. As objects in motion become smaller, they appear to recede into the distance or move farther away; objects in motion that appear to be getting larger seem to be coming closer. This a form of kinetic depth perception. Using kinetic depth perception enables the brain to calculate time to crash distance (TTC) at a particular velocity. When driving, we are constantly judging the dynamically changing headway (TTC) by kinetic depth perception.
Color vision - Correct interpretation of color, and especially lighting cues, allows the beholder to determine the shape of objects, and thus their arrangement in space. The color of distant objects is also shifted towards the blue end of the spectrum. (e.g. distant mountains.) Painters, notably Cezanne, employ "warm" pigments (red, yellow and orange) to bring features forward towards the viewer, and "cool" ones (blue, violet, and blue-green) to indicate the part of a form that curves away from the picture plane.
Perspective - The property of parallel lines converging at infinity allows us to reconstruct the relative distance of two parts of an object, or of landscape features.
Relative size - An automobile that is close to us looks larger than one that is far away; our visual system exploits the relative size of similar (or familiar) objects to judge distance.
Aerial perspective - Due to light scattering by the atmosphere, objects that are a great distance away have lower luminance contrast and lower color saturation. In computer graphics, this is called "distance fog". The foreground has high contrast; the background has low contrast. Objects differing only in their contrast with a background appear to be at different depths
Depth from Focus - The lens of the eye can change its shape to bring objects at different distances into focus. Knowing at what distance the lens is focused when viewing an object means knowing the approximate distance to that object.
Occlusion (also referred to as interposition) - Occlusion (blocking the sight) of objects by others is also a clue which provides information about relative distance. However, this information only allows the observer to create a "ranking" of relative nearness.
Peripheral vision - At the outer extremes of the visual field, parallel lines become curved, as in a photo taken through a fish-eye lens. This effect, although it's usually eliminated from both art and photos by the cropping or framing of a picture, greatly enhances the viewer's sense of being positioned within a real, three dimensional space. (Classical perspective has no use for this so-called "distortion", although in fact the "distortions" strictly obey optical laws and provide perfectly valid visual information, just as classical perspective does for the part of the field of vision that falls within its frame.)
Texture gradient - Suppose you are standing on a gravel road. The gravel near you can be clearly seen in terms of shape, size and colour. As your vision shifts towards the distant road the texture cannot be clearly differentiated.
Binocular and oculomotor cues
Stereopsis or Retinal disparity - Animals that have their eyes placed frontally can also use information derived from the different projection of objects onto each retina to judge depth. By using two images of the same scene obtained from slightly different angles, it is possible to triangulate the distance to an object with a high degree of accuracy. If an object is far away, the disparity of that image falling on both retinas will be small. If the object is close or near, the disparity will be large. It is stereopsis that tricks people into thinking they perceive depth when viewing Magic Eyes, Autostereograms, 3D movies and stereoscopic photos.
Accommodation - This is an oculomotor cue for depth perception. When we try to focus on far away objects, the ciliary muscles stretches the eye lens, making it thinner. The kinesthetic sensations of the contracting and relaxing ciliary muscles (intraocular muscles) is sent to the visual cortex where it is used for interpreting distance/depth.
Convergence - This is also an oculomotor cue for distance/depth perception. By virtue of stereopsis the two eye balls focus on the same object. In doing so they converge. The convergence will stretch the extraocular muscles. Kinesthetic sensations from these extraocular muscles also help in depth/distance perception. The angle of convergence is larger when the eye is fixating on far away objects."
(
Wikipedia, Depth perception.) Of the binocular cues, accommodation and convergence are essentially meaningless beyond about 20 feet as the optical system is then set to "infinity" with the lens as thin as possible and the eye muscles aiming both eyes parallel to infinity.
Part of "distance" is also uphill-downhill effects, as the energy of the putt for level distance is less than that required for the same linear measurement but with some elevation change uphill involved. So the golfer combines the reading skills for slope, slant and contour shape, plus the foot proprioception, to perceive uphill-downhill effects.
A golfer with only one good eye will focus more upon the monocular cues to distance (such as the known actual size of the hole and flag stick and having a caddy tend the flag routinely, walking around the hole for motion parallax, and similar tricks), and will also pace off the putts to supplement the visual deficits with kinesthetic cues. The neck turn from ball to hole that I teach is essentially a non-visual, kinesthetic "dialing in" of the distance by the instinctive association of neck-turn angle registered by nerves in the neck with specific distances along the ground sideways.
MECHANICS
The golfer with challenges for depth perception has a slight hand-eye coordination issue in the making of the stroke in terms of timing ball-putter square impact and starting the ball straight on line -- but not if properly trained. Fixing the head steadily at a given height above the ground at address results in the lens of the good eye establishing a very specific focal adjustment that makes the grass below the face (or the back of the ball) come sharply into focus. The way this happens is that a ring of tiny muscles arranged like the springs on a circular trampoline stretch the lens flat and thin for distant targets and then relax to allow the lens to puff back fatter for near targets. At the distance below the eyes to the ground for putting, usually about 4.5 feet or so, the lenses are pulled to a VERY specific tautness. Hence, focusing sharply on the ground behind the ball and KEEPING the focus is a good way to organize hand-eye coordination, head steadiness, and non-thinking brain processing during the stroke.
Another mechanical tip is to hang your arms and hands fully yet neutrally in gravity before assuming a grip on the aimed putter, and then taking hold of the putter handle without reaching out or in to the handle but leaving the arms hanging neutrally in gravity and walking them out to the handle as it is posed waiting for the golfer. This removes the bent elbows and the extra torquing of the putter in the hands -- both of which place unnecessary demands upon hand-eye coordination that could use a little help from stereopsis and depth perception. basically, a neutral setup allows you to make a stroke without hand-eye coordination but with internal feel of the usual motion instead. hand-eye coordination is always a "one-off" deal, whereas consistent structural setup and movement is always the same and never differs from putt to putt and has next to nothing to do with vision. The demands that a good, accurate, consistent stroke places upon the visual system is almost entirely a peripheral awareness of hand and putter head position during the stroke, which is to say -- not much.
Finally, to help organize the stroke mechanically in terms of where the putter head needs to move and how and where the ball needs to roll as it exits the setup, use this visual routine (which does not require two eyes): look at the putter head as aimed and commit to rolling the ball ONLY wherever the face aims; look at the aim line on the putter head for this direction of roll; project this aim line on the front side of the ball to identify the first 3-5 inches of grass blades in a single-file line over which the bottom of the ball must roll at the start of the putt; roll the ball over these grass blades and none other, and make sure to roll over the last blade as missing this last blade is not acceptable. This simple visual routine overcomes a lot of useless and harmful "visual chatter" (to use a synesthesia metaphor).
SUMMARY
The golfer with only one good eye has a benefit when aiming from behind the ball or from beside the ball. Otherwise, this golfer has a disadvantage in reading putts and perceiving distance.
For reading putts, this golfer needs to use the different perspective of the scene as a whole, the green as defined by its fringe outline, and the local area near the hole to take advantage of external cues to vertical and horizontal in gravity, and to perceive the fall line of the green generally as a whole and locally thru the cup. This golfer will also focus upon the texture gradient changes over a broad swath of green surface taking in the area of the putt and hole, which is mostly about perspective and light-dark contrast, and visual acuity. This golfer will also use motion and foot proprioception to gauge the surface contour.
For distance, this golfer will derive significant benefit from the special skills for reading putts that apply also to distance perception (e.g., texture gradient), and will focus upon monocular visual cues and kinesthetic cues (pacing putts and neck turn from ball to hole).
All together, having a deficit for "depth perception" in putting is not nearly as handicapping as most people seem to assume. The vaulted place given to "depth perception" in human perception is fairly overblown.
Cheers!
Geoff Mangum
Putting Coach and Theorist
Geoff Mangum's
PuttingZone
PuttingZone Clinics
Flatstick Forum
PuttingZone Channel on YouTube
PuttingZone Picasweb Image Gallery
Golf's most advanced and comprehensive putting instruction -- you're either in the PuttingZone, or not.
Over 2.5 million visits -- 200,000 monthly from 50+ countries -- and growing strong.
