Your gait and peripheral vision: Part 2. There is more to it than what you do/don’t see.

Written by Dr. Shawn Allen

Yesterday we did a blog post on the loss of peripheral vision from drooping eye lids leading to the necessity (not vanity based) of a minor surgical procedure called a blepharoplasty.  Here was that blog post (link), it had some important research based points you need to know.

Vision is typically the predominant sensory system used for guiding locomotion. Online visual control is critical for adjusting lower limb trajectory and ensuring proper foot placement, including optimal limb/foot crossing velocity, optimal trail-foot horizontal distance and lead-toe clearance. Research suggests that peripheral visual cues play a large role in this online gait control. 1

We have discussed many of these issues, the conscious and subconscious importance of vision on human gait, in many of our blog posts over time.  Namely, blog posts on dual-tasking attention, negotiating stairs, and even in tandem walking holding hands. These all require a degree of peripheral vision function otherwise gait problems, including falls, rise on the risk list.

According to Timmis and Buckley (2), “although gaze during adaptive gait involving obstacle crossing is typically directed two or more steps ahead, visual information of the swinging lower-limb and its relative position in the environment (termed visual exproprioception) is available in the lower visual field (lvf).”  Their study determined exactly when lvf exproprioceptive information is utilized to control/update lead-limb swing trajectory during obstacle negotiation. 

Their study determined that “when (the) lower visual field (lvf) was occluded, foot-placement distance and toe-clearance became significantly increased; which is consistent with previous work that likewise used continuous lvf occlusion”. Their findings suggest that “ lvf (exproprioceptive) input is typically used in an online manner to control/update final foot-placement, and that without such control, uncertainty regarding foot placement causes toe-clearance to be increased. Also that lvf input is not normally exploited in an online manner to update toe-clearance during crossing: which is contrary to what previous research has suggested.” 2

Elliot and Buckley (3) showed the importance of peripheral visual cues in the control of minimum-foot-clearance during overground locomotion. In their study, 

From their abstract: “eleven subjects walked at their natural speed whilst wearing goggles providing four different visual conditions: upper occlusion, lower occlusion, circumferential-peripheral occlusion and full vision. Results showed that under circumferential-peripheral occlusion, subjects were more cautious and increased minimum-foot-clearance and decreased walking speed and step length. The minimum-foot-clearance increase can be interpreted as a motor control strategy aiming to safely clear the ground when online visual exproprioceptive cues from the body are not available. The lack of minimum-foot-clearance increase in lower occlusion suggests that the view of a clear pathway from beyond two steps combined with visual exproprioception and optic flow in the upper field were adequate to guide gait. A suggested accompanying safety strategy of reducing the amount of variability of minimum-foot-clearance under circumferential-peripheral occlusion conditions was not found, likely due to the lack of online visual exproprioceptive cues provided by the peripheral visual field for fine-tuning foot trajectory.”

These appear to be important studies on the effects of vision and peripheral vision and proprioceptive cues.  How we move our bodies depends much on visual cues, the ones we know we see, and the ones we are unaware that we “see”. Take this to the next level, imagine how the blind must adapt to gait without these cues. That is gait topic we will save for another time.

So, the gait analysis you are doing with your runners, your athletes, your clients takes into consideration their vision right ? Hmmmm, some how we just know that many gait gurus just sat back in their chairs and let out a long exhale. We go even more rogue in podcast 95 when we discuss head tilt and the vestibular system, we know that one is almost always overlooked. Another long exhale we presume.

Shawn Allen … .  one of the gait guys

References:

1. Exerc Sport Sci Rev. 2008 Jul;36(3):145-51. doi: 10.1097/JES.0b013e31817bff72.Role of peripheral visual cues in online visual guidance of locomotion. Marigold DS¹.

2.Gait Posture. 2012 May;36(1):160-2. doi: 10.1016/j.gaitpost.2012.02.008. Epub 2012 Mar 17.Obstacle crossing during locomotion: visual exproprioceptive information is used in an online mode to update foot placement before the obstacle but not swing trajectory over it.Timmis MA¹, Buckley JG.

3. Gait Posture. 2009 Oct;30(3):370-4. doi: 10.1016/j.gaitpost.2009.06.011. Epub 2009 Jul 22.Peripheral visual cues affect minimum-foot-clearance during overground locomotion.Graci V¹, Elliott DB, Buckley JG.

“I keep walking into doorframes,” : A visual aspect of problematic gait you likely have not considered.

Written by Dr. Shawn Allen

Recently i had an elderly client come in to see me, we were working on some arthritic knee problems post-total knee arthroplasty. He mentioned to me that he recently had eye surgery because he was having some gait difficulties. My brain immediately when into age related gait decline, you know, balance kind of stuff.  He mentioned that he was banging into door frames because he was not clearing the sides of the door frames and was also banging up his knees, ankles, thighs and toes on many other things.  He said he had been getting anxious about his gait and thought he might be experiencing some kind of neurologic gait problem. He wasn’t trusting his gait, he feared leaving his house. He happened to mention it to his eye doctor a few months ago and here is what he told him .  

“Your upper eye lids are drooping so much that they are obliterating your peripheral vision. You can’t avoid banging into things that you cannot see. Your peripheral vision is imperative for normal safe gait.”

Drooping eyelids are an inevitable effect of getting older, but the sagging eyelids can impair peripheral vision and magnify gait risks. The procedure known as a blepharoplasty is a simple procedure performed on the upper eyelid when the lid drops down and creates a lateral blind or fold blocking out the lateral eye fields. When looking to the extremes of lateral gaze or depending on peripheral vision this fold blocks the lateral field on the affected eye while the bridge of the nose blocks the same lateral field of the other eye. Effectively, the lateral gaze and peripheral vision becomes progressively narrowed. 

Watch the gait of your elderly clients. Observe how they move about your office, around furniture, tables, door frames. Ask if their gait is uncertain. Ask if they are running into things for no apparent reason.  Think about this next time you are walking in close proximity of the elderly, just because you see them in your peripheral vision, does not mean they can see you.  Remember, their balance and stability is likely not what yours is, it might not take much to knock them over for what appears to be little reason at all.

From the Graci study: 

“However, under CPO conditions (circumferential peripheral visual field occlusion), the doorframe led to a further reduction in crossing velocity and increase in trail-foot horizontal distance and lead-toe clearance, which may have been because of concerns about hitting the doorframe with the head and/or upper body.”

From their conclusions, “exteroceptive cues are provided by the central visual field and are used in a feed-forward manner to plan the gait adaptations required to safely negotiate an obstacle, whereas exproprioceptive information is provided by the peripheral visual field and used online to “fine tune” adaptive gait. The loss of the upper and lower peripheral visual fields together had a greater effect on adaptive gait compared with the loss of the lower visual field alone, likely because of the absence of lamellar flow visual cues used to control egomotion.”

Shawn Allen, one of the gait guys.

1. Optom Vis Sci. 2010 Jan;87(1):21-7. doi: 10.1097/OPX.0b013e3181c1d547.Utility of peripheral visual cues in planning and controlling adaptive gait.Graci V¹, Elliott DB, Buckley JG.

2. http://abcnews.go.com/blogs/health/2013/05/31/eye-lifts-fine-line-between-cosmetic-and-therapeutic/