Explore the connection between heat and CVI. Understand the physical and visual effects, as shared by individuals with CVI and their families.

This summer many of us attended the Perkins CVI Conference. One of the best sessions featured a panel of individuals with CVI. They spent time describing what it’s like to live with the CVI, including its many physical ramifications. Many of them report that they experience pain, migraines, nausea, flu-like symptoms or auto-immune issues that they attribute to the stress and fatigue that comes from living with CVI. 

They also shared how heat impacts their body generally and vision specifically. Over the past several years, individuals with CVI and care partners have shared many examples about heat and CVI. While little research exists on the topic, we have anecdotes that demonstrate it’s a worthwhile area to explore.

I recently had the opportunity to chat with an adult with CVI who graciously described what it’s like for her on a hot day. Out of respect for her privacy, we’ll call her Gillian. “Obviously, the hotter it is, the worse it is,” she says. “I get quite ill in the heat generally, so I can feel very sick and fatigued and quite dizzy. My visual field can be smaller. Everything can be a bit more white and washed out. 

“I’ve been working the last few days in this heat. I might be pulling into a train station that I know, and yet it looks completely different and I don’t recognize it. I could be in a meeting room and my vision gets really bad and I struggle to hear and understand what people are saying more. If I’m trying to navigate a familiar route home on my own, I notice my vision is a lot worse. It’s more blurry.”

Tina Zhu Xi Caruso, an adult with CVI, agrees. “Especially when it’s hot or there’s a large crowd. The worst is when it’s a combo of both.” Tina is a photographer and rendered this image simulating her vision when she runs under these conditions. “I lose my sight,” she explains.

“Living in Iceland, heat isn’t that much of an issue for me on a daily basis,” says Dagbjört Andréstóttir, opera singer and adult with CVI. “But when I’m abroad in summertime, my visual field shrinks even more or my vision becomes unusable.”

Gillian explains that her higher-order visual functions weaken in the heat. She experiences optic ataxia (difficulty using vision to reach for or point to objects) and gives the example of placing a glass on the counter. She’s likely to miss the counter completely under hot conditions.

Other physical symptoms 

It’s common for people with CVI to report that the heat leads to dizziness, mental fog, nausea, low energy, weakness, and difficulty with other senses like hearing.

Gillian adds that when she experiences visual fatigue, “it can be harder to hear and understand people. It’s that classic CVI thing of don’t try and look at listen at once. I can maybe do it for so long, but then the vision starts to go and it gets hard to understand.”

Social interactions get stickier too. “I definitely struggle more with the social interaction and all of those things in the hotter weather. It’s almost like my tolerance for everything is lower because I’m autistic as well. So that can be a challenge.” 

Gillian asks us to envision the quintessential summer barbecue. “After a couple of hours, I’m just so exhausted, and I just can’t put up that facade anymore, right?”

Parent Kathryne Hart notes the global impact of heat on her son who has CVI and dysautonomia (a general term for disorders that affect automatic body processes, such as body temperature and breathing). He also takes medications that prevent sweating and make it harder to cool down; for example, some seizure medications will have this side effect. 

“He starts vomiting in hot weather,” says Kathryne. “We live in the Deep South so A/C is a necessity on the bus and in school for him. Heat exhaustion symptoms include dizziness, blurred vision, and headache. So I would not be surprised to see CVI affected by hot weather in anyone with co-morbidities.”

Hot weather isn’t the only culprit. One parent notes that exercise or a hot shower can cause what their teenager calls “delirium.” In these situations, “sensory inputs like vision, hearing, and touch are displaced and scary. Vision is disrupted and lost first, followed by hearing and touch. In this delirium, it is impossible to plan using conscious thought so my child won’t know what to do and looks ‘stuck.’ They can’t plan motor movements or speak, but will move and respond if given short, direct verbal prompts to get them to a safe place. If we are warm for too long, then the impact can be a cognitive fog along with other symptoms that lasts for days.” 

Ways to deal with the heat

• Avoid it when possible.
• Pace yourself and incorporate breaks.
• Sit in the shade or a dark place – air conditioning is a plus.
• Use a cool compress on the neck, forehead and wrists.
• Make plans to access a cooler or freezer to refresh compresses and other devices, like a cooling vest.
• Find a fan.
• Drink water and electrolytes.

“Heat is tough for Henry,” says CVI parent Rachel Bennett. “It’s a huge migraine trigger. He visually fatigues so quickly in the heat. If he doesn’t have migraine, he still loses most of his energy if he’s out in the heat for too long and needs a dark room, cold compress on his neck, and electrolyte water to recharge. This is why the summer is so hard. Even when we try to cool him down in a pool, he also gets cold really easily and has to wear a full wet suit in 85-degree pool water.”

Another parent describes their teenager’s heat intolerance. “Between 70-80 degrees Farenheit, depending on humidity and direct sun, my child can use external cooling devices to manage for some amount of time. Above 80 degrees they must be indoors in air conditioning. This is a huge barrier because we have to be flexible on things that are planned weeks out, such as O&M, a friend’s picnic, or going to a performance where there is not sufficient air conditioning.” 

They add, “this scary impact of heat is very much like that described by adults with Multiple Sclerosis, Myalgic Encephalomyelitis, and Long Covid, so we follow these communities for ideas.” 

How to be a good companion in the heat

For friends and family who are spending quality time in the heat with someone with CVI: Thank you for your patience. 

“I obviously feel really bad about it, like I don’t want to be just snappy and grumpy and horrible and stressed to everyone,” Gillian laments. “I don’t like that. It just happens.” 

How can you help someone with CVI in the heat? Gillian says, “I think number one would try to be on the understanding of the difficulties they’re facing, and that, like me, they might be snappy, they might be grumpy, they might be tired and overwhelmed, and they might be struggling, and that might not be because they’re trying to be difficult. They might just be overwhelmed.

“And just try to understand if they can’t handle the heat and socializing or studying and all of those things, they might need that support to cool down before they can sort of think straight.” 

It’s hot out there! People globally are dealing with extremely high temperatures. The first rule of being a helpful hot-weather companion for someone with CVI is to recognize that this is a real challenge. Individuals with CVI will have different symptoms and preferences for how to deal with the heat, but they all need people around them who recognize their signs and support them appropriately.