Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Aug. 10, 2022
Document and Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
Document Transition Report	false
Entity File Number	001-38150
Entity Registrant Name	KALA PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0604595
Entity Address, Address Line One	1167 Massachusetts Avenue
Entity Address, City or Town	Arlington
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02476
City Area Code	781
Local Phone Number	996-5252
Title of 12(b) Security	Common Stock, $0.001 par value per share
Trading Symbol	KALA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		73,208,140
Entity Central Index Key	0001479419
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Amendment Flag	false