Therapeutic penetrating keratoplasty for recalcitrant microbial keratitis: An update

Table 1 Characteristics of included studies on therapeutic keratoplasty for recalcitrant infective keratitis

Ref.	Country	Design	Eyes (TPK for keratitis)	Etiology (%)	Mean graft size (mm)	Mean follow-up (months)	Regrafts	Recurrence and complications	Graft clarity and survival (%)	Favourable visual outcomes
Robaei et al[57], 2015	United Kingdom	Retrospective case series	50 (26 TPK, 24 OPK)	Acanthamoeba	NA	62.2 months	26.9% TPK, 12.5% OPK	1 in TPK	-	54.2% TPK, 26.9% OPK
Kitzmann et al[62], 2009	United States	Retrospective comparative case series	31 (22 TPK, 8 OPK)	Acanthamoeba	8.25 TPK, 8.50 OPK	-	55% TPK, 11% OPK	41% TPK, 22% OPK	9 (41%) TPK, 8 (89%) OPK	11 (50%) TPK
								Glaucoma - 32% TPK, 11% OPK		8 (89%) OPK
Kashiwabuchi et al[58], 2008	Brazil	Retrospective	32	Acanthamoeba	NA	24 ± 16 months	12 (37.5%)	Recurrence: 6%	45%	44%
								Graft failure: 56.2%		Mean VA 20/50
								Glaucoma: 40%
Abu Dail et al[59], 2024	Germany	Retrospective case series	28	Acanthamoeba	8.1 ± 0.4 mm	53 ± 42 months	8 (29%)	1 (4%) recurrence, 21 % glaucoma	-	14 (50%)
Zhang et al[50], 2023	-	Retrospective	59 (36 TPK, 23 LK)	Acanthamoeba	NA	NA	NA	10, 6 in TPK, 4 in LK	-	> 20/60 in 14 (38.9%) TPK, 15 (65.2%) LK
Bagga et al[15], 2020	India	Retrospective	23 DALK; 10 large size > 8 mm group, 13 < 8 mm group	Acanthamoeba	9.5 mm, 8 mm	5 months	NR	2 (20%)	32% advanced group, 74.1% in moderate group	NR
								1 (7.7%)
Kwitko et al[60], 2024	Brazil	Retrospective cohort	23; 17 early TPK vs 6 late TPK after 5 months	Acanthamoeba	NA	117 ± 79.61, 105.50 ± 60.90	NR	Early TPK 11.8% (2/17) vs 50% (3/6) late TPK	NR	9 (52.9%) in early vs 2 (33.3%)
Acharya et al[44], 2024	India	Retrospective	16	Pythium insidiosum	10.3 mm, 11.7 mm on repeat	8.9 ± 9.8 months	7/16	9/16	1/16 (6 months)	Mean UCVA 2.04 ± 0.77
Kate et al[51], 2023	India	Retrospective	50	Pythium insidiosum	NA	18.4 months	29/50 (58%)	Secondary glaucoma 20%	10/50 (20%)	Median VA 20/125
Saksurakan et al[31], 2024	Thailand	Retrospective	18 TPK, 2 DALK, 1 femtosecond-ALK	Microsporidia	NA	46	1/18 in TPK	4 (22%) TPK	NR, 8 graft failures	Range 20/40 to perception of light only
							1/3 in ALK	1/3 in ALK

Missing data reflect non-reporting in original studies. Visual acuity outcomes have been standardized to Snellen equivalents where possible. Sample size stratification by pathogen type is included when explicitly reported. Range of visual outcome: 20/20 to no light perception; median corrected distance visual acuity 20/30. TPK: Therapeutic penetrating keratoplasty; NA: Not available; ALK: Anterior lamellar keratoplasty; DALK: Deep anterior lamellar keratoplasty; LK: Lamellar keratoplasty; NR: Not reported separately; OPK: Optical penetrating keratoplasty; UCVA: Uncorrected visual acuity; VA: Visual acuity.

Table 2 Pooled outcomes of therapeutic keratoplasty in severe keratitis

Outcome measure	Pooled result (95%CI)	Interpretation
Anatomical success (globe intact)	89% (88%-91%)	Eye preserved without requiring evisceration or enucleation in 9 out of 10 cases
Therapeutic success (infection cured)	91% (89%-92%)	Infection eradicated post-TPK in majority of eyes
		Recurrence of primary infection occurs in 9% overall (higher if fungal)
Clear graft at final follow-up	45% (43%-48%)	Proportion of grafts remaining clear (no significant opacity or failure) at last follow-up
		Many grafts turn opaque or fail over time despite initial success
Functional visual recovery	20% (range 15%-25% across studies)	Eyes achieving ambulatory vision (≥ 6/60) after TPK were a minority
		Poor initial ocular condition and graft complications limit visual acuity in most cases

Pooled estimates (random-effects) are derived from the 10 included studies using weighted averages based on sample size (95% confidence intervals in parentheses). “Functional vision” generally corresponds to ambulatory vision (approx ≥ 6/60 or ≥ 20/200 Snellen) at final follow-up; because definitions varied, a range is given instead of a pooled value. Statistical analyses were performed using IBM SPSS Statistics (Version 26). Heterogeneity across studies was assessed using I² statistics where applicable. TPK: Therapeutic penetrating keratoplasty; CI: Confidence interval.