Today, eyewear startup Warby Parker announced it has donated half a million pairs of glasses since it was first founded three years ago. According to the company’s promotional materials, “for every pair of glasses” it sells, it provides “a pair to someone in need.”

The above statement quite clearly suggests that if Warby Parker has donated 500,000 pairs of glasses, it has also sold 500,000 pairs of glasses.

As Warby Parker publicly details, the company works directly with VisionSpring to provide glasses to those in need, and it does so by way of a cash donation. According to VisionSpring, which spoke to us by phone, Warby Paker calculates how many pairs they’ve sold every month and makes a cash donation the following month. Since Warby Parker considers these cash donations to be a “glasses donation” in its promotional materials, the company’s 500,000 sales figure could just be a month off.

To be safe, there may be a noteworthy lag in VisionSpring’s distribution process, which means that the 500,000 sales figure is more of a minimum than a maximum for Warby Parker.

Regardless, this proves that Warby Parker has indeed sold at least 500,000 pairs of glasses, unless it’s fudging the numbers.

Now, let’s look back at Warby Parker’s 250,000 milestone from October 2012. Comparing the two, Warby Parker has sold as many glasses in the past nine months as it did in its first 27 months.

In other words, Warby Parker’s growth rate is accelerating quite heavily if these figures are correct, but the company still has quite a long way to go before it can make a dent in its key rival: the eyewear monopoly that is Luxottica.