Built-in accessibility for Windows Phone and Tablet are both rather recent developments. Consequently, there are not many outside resources available for low-vision assistance. At this point your best option for accessibility support is via the Microsoft Accessibility Answer Desk, available in North America from 5 am to 9 pm Pacific during the week, and 6 am to 3 pm on the weekends. You can reach the Answer Desk via a web contact form or by calling 800-936-5900.
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The Windows Touchscreen Tablet Ease of Access Center