On February 22, 2019, we completed a registered rights offering to existing stockholders in which we sold approximately 5,976,000 units at $5.792 per unit, which was the adjusted closing price of our common stock on that date. Each Unit consisted of a share of our common stock and a warrant to purchase an additional share of our stock for $11.76. The warrants had a five-year life and trade on Nasdaq under the symbol EYESW.

On March 6, 2017, we completed a registered rights offering to existing stockholders in which we sold approximately 1,706,000 units at $11.76 per unit, which was the adjusted closing price of our common stock on that date. Each unit consisted of a share of our common stock and a warrant to purchase an additional share of our stock for $11.76. The warrants have a five-year life and have been approved for trading on Nasdaq under the symbol EYESW.

We extended the term of 1.7 million warrants issued in our March 2017 rights offering by approximately two years effective as of February 15, 2019 as part of our February 2019 rights offering. We determined the fair value of the March 2017 Warrants immediately before and after the modification. The fair value of the March 2017 Warrants after the modification was increased by approximately $1.6 million, resulting in an accounting adjustment to additional paid-in capital and accumulated deficit in the consolidated statements of shareholders’ equity. The assumptions used in the determination of fair value of the warrants before and after the extension included a risk free interest rate of 2.50% and 2.49%, expected volatility of 81% and 82%, and expected lives of 3.08 years and 5.08 years, respectively and 0% dividend yields for both.

Upon close of our May 2020 registered offering we issued 375,000 warrants to our underwriter. These warrants are exercisable at $1.25 per share and expire on May 5, 2025. At March 31, 2021, 10,125 of the warrants are still outstanding.

A summary of warrants activity for the three months ended March 31, 2021 is presented below (in thousands, except per share and contractual life data).

	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life (in Years)
Warrants outstanding as of December 31, 2020		7,759		$	11.66		3.21
Issued		—
Exercised		(67	)		11.76
Forfeited or expired		—
Warrants outstanding as of March 31, 2021		7,692		$	11.75		2.96
Warrants exercisable as of March 31, 2021		7,692		$	11.75		2.96