Subconjunctival Microinvasive Glaucoma Surgeries

Conclusion

Both the Xen gel stent and PreserFlo MicroShunt have demonstrated promise for a wide application for glaucoma patients with a range of glaucoma severity and medication burden. These devices provide patients with IOP lowering effects similar to traditional incisional surgery such as trabeculectomy or tube shunt surgery, but with fewer risks than these more invasive alternatives. These devices have demonstrated impressive efficacy so far and decrease the risk of both early and late hypotony because of their valve-less intrinsic flow-limiting design. Still, there need to be additional randomized, prospective studies comparing these gel stents and microshunts both to each other and to other traditional glaucoma surgeries.

Table 1. Xen surgical outcomes
Authors	Year	Study design	Potential conflicts of interest	Primary cohort	Comparative group	Study duration (months)	Number of eyes	Previous glaucoma surgery (%)	Combined with CEIOL	MMC application	Preop IOP (mean ± SD)	Preop meds (mean ± SD)	Postop IOP (mean ± SD)	Postop meds (mean ± SD)	% IOP reduction	Needling rate, %
Perez-Torregrosa et al.	2016	Prospective, noncomparative	None	POAG	None	12	30	None	100%	0.1 ml of 0.1 mg/ml	21.2 ± 3.4	3.07 ± 0.69	15.03 ± 2.47	0.17 ± 0.65	29.34	None
DeGregorio et al.	2017	Prospective, noncomparative	None	Primary or secondary OAG	None	12	41	2.4	100%	0.1 ml of 0.1 mg/ml	22.5 ± 3.7	2.5 ± 0.9	13.1 ± 2.4	0.4 ± 0.8	41.82	2.4
Galal et al.	2017	Prospective, noncomparative	None	POAG	None	12	13	None	76.92%	0.1 ml of 0.1 mg/ml	16 ± 4	1.9 ± 1	12 ± 3	0.3 ± 0.49	29.4	30.7
Grover et al.	2017	Prospective, multicenter, noncomparative FDA study	Allergan: sponsor, study design, data interpretation, manuscript preparation; all authors with allergan affiliations	POAG	None	12	65	84.6	None	0.2 mg/ml for 2 min (sponges)	25.1 ± 3.7	3.5 ± 1.0	15.9 ± 5.2	1.7 ± 1.5	35.6	32.3
Schlenker et al.	2017	Retrospective, multicenter, comparative	4/9 authors with Allergan affiliation, but no allergan involvement in funding or study design	Primary/secondary OAG, mixed mechanism, or primary angle closure	Trabeculectomy with MMC (0.2 mg/ml injection or sponges)	Xen: 15. Trab: 17.8	354 (185 Xen, 169 trab)	None	None	0.05–0.2 ml of 0.2 mg/ml	24	3	13	0	45.83	43.2
Mansouri et al.	2017	Prospective, comparative	2/7 Authors with allergan affiliation	Primary or secondary OAG	Combined Xen/CE	12	149	None	73.2	0.1 ml of 0.02 mg/ml	20 ± 7.1	1.9 ± 1.3	13.9 ± 4.3	0.5 ± 0.8	31%	37
Hengerer et al.	2017	Retrospective, noncomparative	None	POAG, PXFG	None	12	242	43.4	16.1	0.1 ml of 0.01 mg/ml	32.19 ± 9.1	3.13 ± 1.0	14.24 ± 4.0	0.3 ± 0.7	54.1	27.7
Karimi et al.	2018	Retrospective, noncomparative, multicenter	5/10 Authors with allergan affiliation	POAG, PXFG, NTG	None	12	259	7.5	27.8	0.1 ml of 0.2 mg/ml	19.3 ± 6.0	2.6 ± 0.1	13.5 ± 3.3	1.1 ± 0.5	26.4	40.9
Widder et al.	2018	Retrospective, noncomparative	None	Primary/secondary OAG, PXFG	None	8.5	261	18.4	21	0.1 ml of 0.1 mg/ml	24.3 ± 6.6	2.6 ± 1.1	16.8 ± 7.7	0.2 ± 0.7	30.9	34
Heidinger et al.	2019	Retrospective, noncomparative	1/5 Authors with allergan affiliation	POAG, PXFG	None	18	199	30.7	69.3	0.1 ml of 0.1 mg/ml	22.8 ± 6.9	2.9 ± 1.0	16.4 ± 3.8	1.8 ± 1.4	20.1	22.1
Kalina et al.	2019	Prospective, noncomparative	None	POAG, PXFG, NTG	None	12	47	4.2	57.4	0.1 ml of 0.2 mg/ml	22.34 ± 7.34	2.96 ± 1.2	13.61 ± 2.9	0.75 ± 1.27	33	29.8
Mansouri et al.	2019	Prospective	3/5 Authors with allergan affiliation	POAG, PXFG	None	24	110		74	0.1 ml of 0.2 mg/ml	19.8 ± 5.8, 19.8 ± 8.2	2 ± 1.5	14.35 ± 3.7	0.5 ± 0.8	27	43

Table 1. Xen surgical outcomes

Authors

Year

Study design

Potential conflicts of interest

Primary cohort

Comparative group

Study duration (months)

Number of eyes

Previous glaucoma surgery (%)

Combined with CEIOL

MMC application

Preop IOP (mean ± SD)

Preop meds (mean ± SD)

Postop IOP (mean ± SD)

Postop meds (mean ± SD)

% IOP reduction

Needling rate, %

Perez-Torregrosa et al.

2016

Prospective, noncomparative

None

POAG

None

100%

0.1 ml of 0.1 mg/ml

21.2 ± 3.4

3.07 ± 0.69

15.03 ± 2.47

0.17 ± 0.65

29.34

None

DeGregorio et al.

2017

Prospective, noncomparative

None

Primary or secondary OAG

None

2.4

100%

0.1 ml of 0.1 mg/ml

22.5 ± 3.7

2.5 ± 0.9

13.1 ± 2.4

0.4 ± 0.8

41.82

2.4

Galal et al.

2017

Prospective, noncomparative

None

POAG

None

76.92%

0.1 ml of 0.1 mg/ml

16 ± 4

1.9 ± 1

12 ± 3

0.3 ± 0.49

29.4

30.7

Grover et al.

2017

Prospective, multicenter, noncomparative FDA study

Allergan: sponsor, study design, data interpretation, manuscript preparation; all authors with allergan affiliations

POAG

None

84.6

None

0.2 mg/ml for 2 min (sponges)

25.1 ± 3.7

3.5 ± 1.0

15.9 ± 5.2

1.7 ± 1.5

35.6

32.3

Schlenker et al.

2017

Retrospective, multicenter, comparative

4/9 authors with Allergan affiliation, but no allergan involvement in funding or study design

Primary/secondary OAG, mixed mechanism, or primary angle closure

Trabeculectomy with MMC (0.2 mg/ml injection or sponges)

Xen: 15. Trab: 17.8

354 (185 Xen, 169 trab)

None

0.05–0.2 ml of 0.2 mg/ml

45.83

43.2

Mansouri et al.

2017

Prospective, comparative

2/7 Authors with allergan affiliation

Primary or secondary OAG

Combined Xen/CE

149

None

73.2

0.1 ml of 0.02 mg/ml

20 ± 7.1

1.9 ± 1.3

13.9 ± 4.3

0.5 ± 0.8

31%

Hengerer et al.

2017

Retrospective, noncomparative

None

POAG, PXFG

None

242

43.4

16.1

0.1 ml of 0.01 mg/ml

32.19 ± 9.1

3.13 ± 1.0

14.24 ± 4.0

0.3 ± 0.7

54.1

27.7

Karimi et al.

2018

Retrospective, noncomparative, multicenter

5/10 Authors with allergan affiliation

POAG, PXFG, NTG

None

259

7.5

27.8

0.1 ml of 0.2 mg/ml

19.3 ± 6.0

2.6 ± 0.1

13.5 ± 3.3

1.1 ± 0.5

26.4

40.9

Widder et al.

2018

Retrospective, noncomparative

None

Primary/secondary OAG, PXFG

None

8.5

261

18.4

0.1 ml of 0.1 mg/ml

24.3 ± 6.6

2.6 ± 1.1

16.8 ± 7.7

0.2 ± 0.7

30.9

Heidinger et al.

2019

Retrospective, noncomparative

1/5 Authors with allergan affiliation

POAG, PXFG

None

199

30.7

69.3

0.1 ml of 0.1 mg/ml

22.8 ± 6.9

2.9 ± 1.0

16.4 ± 3.8

1.8 ± 1.4

20.1

22.1

Kalina et al.

2019

Prospective, noncomparative

None

POAG, PXFG, NTG

None

4.2

57.4

0.1 ml of 0.2 mg/ml

22.34 ± 7.34

2.96 ± 1.2

13.61 ± 2.9

0.75 ± 1.27

29.8

Mansouri et al.

2019

Prospective

3/5 Authors with allergan affiliation

POAG, PXFG

None

110

0.1 ml of 0.2 mg/ml

19.8 ± 5.8, 19.8 ± 8.2

2 ± 1.5

14.35 ± 3.7

0.5 ± 0.8

Subconjunctival Microinvasive Glaucoma Surgeries

An Update on the Xen Gel Stent and the PreserFlo Microshunt

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