Proceedings of: Workshop on Improving Building Design for Persons with Low Vision

Other Health Problems with Low Vision Patients

Okay, the other thing to keep in mind is these people are old and they have other health problems. More than half or two-thirds will report they’re in good to excellent health when they come to the clinic (slide 51). Of course, we don’t see the ones that can’t get to the clinic to go to get help, so there is a bit of a sample bias here – and that’s true for all ages.

Frequency Distribution of Health Problems

But when you ask them about their health, they have all the same diseases that anybody in that age group would have (slide 52). They report diabetes, heart problems, heart attacks, high blood pressure, neurological problems. Back pain is a real common one. Thirty-percent said they have back pain.

These co-morbidities that you have to consider [as part of] the overall health burden that this population has. And you’re adding a visual impairment on top of all the bricks they’re carrying. So the effects of visual impairment in this population can be magnified compared to the effects in a younger population. A lot of times compensation is more difficult, because of the other things they’re dealing with.

Cognition and Emotional States

I think given the time limit, you can scroll ahead, because I want to make a particular point about – let me just say one thing is that depression is also a problem with this group (slide 53). Thirty percent of people with low vision have clinically significant depression and they become isolated and don’t go out. A lot of this is related to fear of falling (slide 55), not getting outside the home. Life space shrinks down to very few social interactions.

Falls and Injuries

So talking about falls: Just in general, if you look at the epidemiology literature, there was actually a Safety and Seniors Act that was passed in 2007 or 2008. It was called the Act of 2007 of Putting Emphasis on Preventing Falls and Injuries in the Older Population. But a third of the people who reach 65 have fallen at least once in the preceding year (slide 64). About a third of the people over 65 have a strong fear of falling and that limits their activities. And this prevalence of both falls and fear of falling increases with age.

Well, in terms of hip fractures, 90 percent of the hip fractures occur in this population because of falls (slide 65). Visual acuity loss turns out to be a major independent risk factor for hip fractures. I’ll give you those numbers in a minute. Relative to people who have 20/20 visual acuity – if you test for all the other variables – hip fractures double in the acuity range of 20/30 to 20/40. They triple in the range of 20/50 to 20/70. We’re not even up to Medicare paying for it. And then once you get up into Medicare’s definition of low vision, it quadruples. So you have four times the risk of hip fracture if you have low vision by Medicare definition than you if you don’t – all else being equal.

Accidents [are] the leading cause of death in seniors; falls account for about 50 percent of accident of deaths, car accidents account for the other 50 percent (slide 66). The death rate from all causes increases 20 percent for people who are 20/25 relative to 20/20 (slides 67 and 68). It goes up to 25 percent more for people who are 20/32 – it’s just a small change, one line. And less than 20/30 – that’s not even into what we conventionally considered a low vision category – 20/40s kind of important. They take your driver’s license – put restrictions on your driver’s license. The death rate is 60 percent higher. So the 30 million figure might not be too far off if we’re thinking in terms of the impact it could have on safety.

So probably the reason for this is that as you age, you get nerve degeneration occurring in the vestibular apparatus. That’s the inner ear that controls your balance (slide 71). And you also get nerve degeneration occurring in the stretch receptors and appropriate receptive feedback that you’re getting from your muscles and joints (slide 70). And making your balance – three systems are involved: your vestibular system, which senses accelerations; your receptive feedback from your muscles and joints and your vision (slide 69). [These] are called flow fields that tell you that you’re moving relative to your environment. If you have two of those three systems intact, you can control your balance. If you drink a lot, that screws up the vestibular system, okay? But it also, in doing that – because of dehydration – it also induces what we call vestibular-ocular reflex that, for kind of a nice name, we call it getting dizzy. And balance tests tend to be good diagnoses that you are having too much to drink.

If you lose two of these systems, you cannot maintain your balance. If we have just neurodegeneration going on, we’re probably increasing the load on vision to maintain balance as we grow older. Added to that, neural-degenerative diseases like peripheral artery disease and things like that in this composite, and so [there is] more reliance on vision. And even so, small changes in vision seem to have a big impact on both.

Mobility

So we can get more or less back on schedule, I’ll not go through the details of these other slides, except to show you that for all functions, they decrease pretty systematically with visual acuity and with contrast sensitivity (slides 72 – 77). But notice that mobility is very poor to begin with. Normal here would be about five. So even for people with very good contrast sensitivity and going back even for people with very good visual acuity, mobility is the worst affected and it stays bad. And as the vision gets worse, the other functions come down, but mobility gets clobbered early and stays clobbered. And blind spots do the same kind of thing. Mobility gets clobbered early and stays clobbered. These are all independent effects.

So the focus really has to be – the biggest bang really has to be on mobility (slide 78). And what can be done – I’ve already heard people talk about; I don’t think I’m going to tell you anything new – but increase contrast. Glass doors are not good for people who have visual impairments; reduce camouflaging clutter. Increase the light, but not too much; you want to reduce glare. What that means is get the light sources out of the line of sight, okay?

Increase safety is a big part and we saw pictures of stairs and other things. And the emphasis here really has to be on steps, stairs and drop-offs. That’s where the falls occur, either on the top of the steps or the bottom of the steps or off a curb. And the changes in surface elevation – ramps on sidewalks – these types of things. Even on a small ramp to go up to change a level can be a deadly hazard for someone who can’t see that transition. And transitions from surface texture – going from carpet to tile – can be a tripping hazard. To people who can’t see that texture change, that could increase the risk.