An important concept in SEO is ensuring that your website is accessible. This means that your site is more widely accessible by providing support for people such as those who are visually impaired. The video below provides a brief introduction to what accessability means in the context of SEO.
Use Alt Text
Alt text is text that is attached to an image that replaces the image if either the image won’t load correctly, or if a site reader is being used by a vision-impaired visitor. The site reader will read the alt text in place of the image.
Having the font size on your site large enough to be easily read is important to user experience, the more so if the user of the site is vision impaired. Be sure that your text is at least 14 point.
Even if a font is large enough, it can be hard to read if the font color doesn’t have sufficient contrast with the background color.