Authors	Year	Study period	Region	No. of grafts	Types of graft	No. of eyes with PKIK	Age, years (mean ± SD)	Female %	Incidence %	Time of PKIK after keratoplasty (months)
Dohse et al. (24)	2020	2007–2018	US	2,098	PK and EK	86	64.7 ± 21.7	59.3	4.1 (PK: 5.9, EK: 1.3)	28.7 (28.5 for PK, 30.4 for EK)
Griffin et al. (25)	2020	2004–2015	UK	1,508	PK, DALK, and epikeratophakia	66 (72 episodes)	56.0 ± 20.7	49	4.77	25 months
Okonkwo et al. (26)	2018	1997–2014	UK	759	PK, DALK, and DSAEK	41 (59 episodes)	73.0 ± 19.4	53.7	5.4	–
Sun et al. (27)	2017	2000–2009	Taiwan	871	PK	52 (67 episodes)	65.5 ± 16.9	–	7.7	27.1 ± 28.0 days (range, 0–86 days)
Chen et al. (28)	2017	2003–2007	Taiwan	648	PK	42	49.1 ± 21.5	40.5	6.5	12.0 ± 9.5 months
Edelstein et al. (29)	2016	2007–2014	US	354,930	PK, EK, and ALK	66	–	–	0.02	29 days (1–216 days range)
Constantinou et al. (30)	2013	1998–2008	Australia	650	PK	122	75.0 ± 14.8 (failed graft), 61.8 ± 16.3 (clear graft)	58.8	18.8	72.0 ± 32.4 (failed graft), 114.0 ± 97.2 (clear graft)
Wagoner et al. (12)	2007	1998–2002	US	2,103	PK	102	50.4	42.2	4.9	38.2% occurred within 12 months
Tavakkoli and Sugar (31)	1994	1976–1992	US	885	PK	36	–	–	4.9	–
Leahey et al. (32)	1993	1976–1992	US	773	PK	18	58.9	72.2	–	21.5 months (range 1–53 months)
Bates et al. (33)	1990	1983–1988	UK	1,700	PK	30	55	41	1.76	10 months (range 1–168)
Fong et al. (34)	1988	1978–1985	US	2,006	PK	66 (68 episodes)	61	–	3.3	–
Al-Hazzaa and Tabbara (35)	1988	1983–1986	Saudi Arabia	947	PK	113	–	31	11.9	5.4 months (range 10 days−12 months)