Ashtangasamgraha 32.10

32.10

prasādana eva cūrṇastīkṣṇāñjanābhisantapte cakṣuṣi prayujyamānaḥ pratyañjanasaṃjñāṃ labhate |

ṣaḍvidhaṃ vā pratirasabhedādañjanam |

dvividhameva vā tīkṣṇaṃ mṛdu ca ||

The very soothing collyrium in powder form, when applied to an eye tormented by sharp collyrium, obtains the designation 'counter-collyrium' (pratyañjana).
Alternatively, collyrium is sixfold according to the division of each taste;
or it is just twofold: sharp and mild.