Natyashastra
दीप्ता विकसिता क्षुब्धा गम्भीरा समतारका । उत्फुल्लमध्या दृष्टिस्तु वीरा वीररसाश्रया ॥ ५२॥
Vīrā: The Glance which is bright, fully open, agitated, serious, and in which eyeballs are at the centre of the eye (lit. leyel) is called Vīrā (heroic), and it is used in the Heroic Sentiment.
english translation
dIptA vikasitA kSubdhA gambhIrA samatArakA । utphullamadhyA dRSTistu vIrA vIrarasAzrayA ॥ 52॥
hk transliteration by Sanscript