The night is overtaking our computer screens.

It’s coming in the form of dark mode, a trendy feature in the tech industry in which the standard bright backgrounds are substituted with a muted navy or black. Twitter launched its dark mode for web in 2017, while Facebook Messenger introduced a dark mode feature in April of this year. Most notably at WWDC last week, Apple announced it will include a dark mode option in iOS 13, which launches this fall. Apple claims that dark mode will “make every element on the screen easier on your eyes,” while some users assert that dark mode is better for people with people with migraines.

But there’s little data to show that dark mode is actually easier on the eyes for most people. Even for users with vision impairments, dark mode isn’t necessarily better than other accessibility options that have been available for years, though there is little research on the subject overall.

One thing is certain: in most daily settings and for most people, dark mode will do nothing to increase productivity or ease eye fatigue. It’s likely nothing more than another aesthetic option — not a life-changing accessibility tool or productivity-enhancer.

In fact, for most people, dark modes will decrease readability and productivity. A 2003 study looked at how users’ task comprehension was affected by different screen display conditions, including negative polarity (light text on a black background) and positive polarity (black text on a white background). It found that test subjects had an easier time completing tasks when the screens were in a positive polarity mode.

Dark mode is likely nothing more than a reasonable aesthetic option — not a life-changing accessibility tool or productivity-enhancer.

Another study, from 2013, looked at the impact of positive and negative polarity on both young and elderly subjects, since an older person’s worsening eyesight could theoretically determine how they’re affected by screen brightness and contrast. The study found that both populations performed better when screens were in a light mode.

Though black text on a white background may technically be the most efficient way to use a screen, dark mode devotees do have one point: the feature may be genuinely useful at night.

That’s because, like looking at a light bulb in a dark space, or attempting to see down a dim hallway from a brightly lit room, if a phone screen is significantly brighter or darker than the surrounding area, the eye will have trouble adjusting. Anyone who’s ever had to squint at their phone screen when checking it before dawn or attempted to view a dark television image in a bright room will be familiar with the experience. This type of situation, according to the Mayo Clinic, can lead to eye strain, with symptoms including eye dryness, fatigue, and headache. In the long run though, it likely won’t lead to lasting damage.

Many smartphone models and computers now come equipped with ambient light sensors, which adjust the brightness of a screen relative to the light of the room you’re in. But for those who are particularly sensitive to light, or simply dislike the warm tone of Apple’s night mode, dark mode features may be a welcome addition.

“Dark mode can be very helpful for people who have sensitivity to brightness, because it reduces the overall intensity of the screen,” says Lauren Milne, an assistant professor of computer science at Macalester College whose research focuses on accessibility issues. “Many people with low vision, especially people with tunnel vision, prefer white text on a black background as they find it easier to distinguish the words.” For years, operating systems have allowed for color inversion, in which dark screen colors are made light and vice versa, but such settings can have an unsettling Andy Warhol-esque effect that may not always be welcome or aesthetically pleasing.

But according to Syed Billah, a PhD candidate in computer science at Stony Brook University, dark mode may not be as effective for low-vision users as the more traditional color inversion. In his research on accessible technology for people with vision impairments, he found that users with certain conditions, like glaucoma, preferred large text in high-contrast modes. In these modes, text appears as yellow, white, or green on a black background. “This is quite different than Mac’s dark mode,” he says. “Dark mode uses different shades of gray, boundaries [and] edges are not very prominent [or] discernible in dark mode, and it doesn’t work for the non-Mac applications very well.”

So while Twitter’s dark mode, for example, may be attractive to people with normal vision, with its navy blue background and white or grey text, it may not work as an accessibility feature for people who genuinely need it. That isn’t to say that dark mode is harmful — just that it won’t make screens any easier to see for people with vision impairments.

Remember, though, that there isn’t a lot of research on modern dark mode interfaces that extends beyond their impact on readability for users with normal vision. Conceivably, well-executed dark modes could improve the experiences of people with photophobia (light sensitivity) or other vision impairments. But because there’s such a dearth of information on the topic, it’s difficult to know to what extent it could help, or what the best implementation of dark mode would be.

“I really wish there were more good, up-to-date studies on the light-on-dark versus dark-on-light issue,” says Silas Brown, a partially-sighted computer scientist at Cambridge University. People with brain conditions that can affect visual processing, such as dyslexia, migraines, and autism, can have sensitivity to light and certain color combinations, but “all of these brain conditions are poorly understood, and each one is really an umbrella term for a whole range of sub-conditions, so we certainly can’t say display settings help in every case.”

Still, Brown and Milne both say that multiple options are better than none, and some people may find that dark mode will help them have better experiences with their screens. “I am always happy when a [developer] officially adds options like dark mode,” says Brown. “It enables individual users to find out for themselves if it makes a difference in their particular case or not.”

It’s great that Apple and others are offering the option to use dark mode, though it isn’t necessarily the best way to look at your screen in bright ambient lighting. But because many of us look at our screens all day every day — and often at night — we need more research about the healthiest ways for those screens to work. Right now, there are a lot of gaps. This is especially true for people with low vision, people who get migraines, and those with other visual impairments. Dark mode may be a cute update for now, but there’s potential for something much better — if companies ever decide to make this kind of accessibility a genuine priority.