A comparative study of a modified filtering trabeculotomy and conventional trabeculectomy

Figures & data

Figure 1 Surgical technique of modified filtering trabeculotomy.

Notes: (A) A rectangular half-thickness scleral flap is created. (B) A deeper tongue- shaped scleral flap is formed to allow access to Schlemm’s canal. (C) A trabeculotomy is performed to both sides. (D) The superficial scleral flap is secured with single sutures after the deeper flap is removed.

Table 1 Demographic data of both groups at baseline

Demographic	Conventional trabeculectomy, n=87	Modified filtering trabeculotomy, n=30	P-valuea
Eye			0.8
Right	46 (52.9)	15 (50.0)
Left	41 (47.1)	15 (50.0)
Age, years	66.9±9.2	66.7±10.0	0.9
Range	46–88	47–86
Sex			0.3
Male	43 (49.4)	11 (36.7)
Female	44 (50.6)	19 (63.3)
BCVA, logMAR	0.10 (0.00–0.22)	0.05 (0.00–0.22)	0.6
IOP, mmHg	23.0 (20.0–27.0)	23.0 (20.0–27.0)	0.9
Treatment with topical glaucoma drugs	86 (98.9)	30 (100.0)	1.0
Topical glaucoma medications, n	3 (2–3)	3 (3–4)	0.04
Type of glaucoma			0.02
POAG	67 (77.0)	20 (66.7)
PEXG	19 (21.8)	6 (20.0)
PG	1 (1.2)	4 (13.3)
Previous ocular surgery			0.03
None	50 (57.5)	14 (46.7)
Laser trabeculoplasty	29 (33.3)	10 (30.0)
Cyclodestructive	8 (9.2)	0 (0.0)
Laser peripheral iridotomyb	4 (4.6)	2 (6.7)
Phaco	9 (10.3)	9 (30.0)

Notes: Data are presented as absolute values (%), mean ± standard deviation, or median (interquartile range).

a Fisher’s exact test, χ² test, Mann–Whitney U-test, Student’s t-test, as appropriate.

b Laser peripheral iridotomy was performed in eyes with slightly narrow angles or pigmentary glaucoma.

Abbreviations: BCVA, best-corrected visual acuity; IOP, intraocular pressure; logMAR, logarithm of the minimum angle of resolution; PEXG, pseudo-exfoliative glaucoma; PG, pigmentary glaucoma; phaco, phacoemulsification; POAG, primary open-angle glaucoma.

Figure 2 Kaplan–Meier survival curve of complete success. Complete success was defined as an intraocular pressure (IOP) of <18 mmHg and IOP reduction of 30% or more without medication. Success rates were not significantly different (P_log-rank=0.25) between both groups during follow-up. One patient treated with modified filtering trabeculotomy (FTO) was lost to follow-up, therefore data were available for 29 patients (96.7%) prospectively followed for 12 months. Of the 87 conventional trabeculectomy (trab) patients, data for 71 patients (81.6%) were available at the 1-year visit. Patients with a follow-up of <12 months were counted as success or failure until the time point of drop out and were marked as censored.

Table 2 Complete successa

Follow-up, months	Conventional trabeculectomy	Modified filtering rabeculotomy	OR (95% CI)
			Crude	Conditionalb
1	66/87 (75.9)	24/28 (85.7)	1.91 (0.59–6.13)	2.51 (0.59–15.4)
3	66/79 (83.5)	23/27 (85.2)	1.13 (0.34–3.83)	1.23 (0.28–7.56)
6	59/76 (77.6)	22/24 (91.7)	2.02 (0.54–7.59)	2.65 (0.48–28.3)
12	59/71 (83.1)	23/29 (79.3)	0.78 (0.26–2.32)	0.69 (0.16–2.94)

Notes: Data are number of patients with complete success/number of patients examined at follow-up (proportion of success at follow-up).

a Complete success: IOP <18 mmHg and 30% IOP reduction without glaucoma medication.

b Conditional logistic regression, accounting for pair-matching.

Abbreviations: CI, confidence interval; IOP, intraocular pressure; OR, odds ratio.

Figure 3 Intraocular pressure (IOP) results over 12 months of follow-up. IOP was significantly reduced in both groups during follow-up (P<0.001). IOP was significantly lower in the modified filtering trabeculotomy (FTO) group than in the conventional trabeculectomy (trab) group at 1 day and 6 months after surgery. No statistical differences between groups were found for the remaining time points. One patient treated with FTO was lost to follow-up, therefore the data for 29 patients (96.7%) were prospectively followed for 12 months. Of the 87 trab patients, data for 71 patients (81.6%) were available at the 1-year visit.

Notes: The black line in the center of each box plot represents the median, the boxes represent the 25th and 75th percentiles, the upper and lower bars are the 1.5 interquartile ranges, and the circles are outliers.

Figure 4 Scatter plots of (A) intraocular pressure (IOP) and (B) visual acuity (VA) results compared with preoperative values for both groups. (A) Eyes below the line of 18 mmHg and 30% IOP reduction fulfilled both criteria of success with or without medication (qualified success). (B) The association of preoperative VA with values at 12 months differed between the trabeculectomy (trab) and modified filtering trabeculotomy (FTO) groups (P-value for interaction <0.01). Postoperative VA was significantly better in patients undergoing FTO.

Notes: A single circle or triangle represents one eye with preoperative and postoperative IOP and VA at 12 months, respectively. The oblique line indicates no change of IOP or VA. Circles or triangles above the oblique line define a higher postoperative IOP or decrease in VA.

Table 3 Postoperative complications and interventions

Complication/intervention	Conventional trabeculectomy, n=87	Modified filtering trabeculotomy, n=29	P-valuea
Early complication (≤90 days)
Elevated IOP (IOP >25 mmHg)	9 (10.3)	10 (34.5)	0.006
Hypotony (IOP <5 mmHg)	18 (20.7)	7 (24.1)	0.8
Choroidal detachment	2 (2.3)	3 (10.3)	0.2
Shallow anterior chamber	3 (3.4)	0 (0.0)	0.7
Conjunctival leakage	5 (5.7)	1 (3.4)	0.8
Hyphema (≥1 mm layered blood)	4 (4.6)	14 (48.3)	<0.001
Iris incarceration	2 (2.3)	0 (0.0)	1.0
Bleb scar	15 (17.2)	4 (13.8)	0.9
Early intervention
Laser suture lysis, eyes	41 (47.1)	21 (72.4)	0.03
Number of sutures, median (IQR)	1 (1–2)	2 (1.5–3.5)	<0.001
5-FU bleb injections, eyes	57 (65.5)	18 (62.1)	0.9
Number of injections, median (IQR)	5 (3–7)	5.5 (3–6)	0.7
Bleb needling	15 (17.2)	4 (13.8)	0.9
Scleral flap revision (overfiltration)	9 (10.3)	4 (13.8)	0.8
Scleral flap revision (elevated IOP)	0 (0.0)	4 (13.8)	0.01
Conjunctival suture	2 (2.3)	0 (0.0)	1.0
Iris reposition	2 (2.3)	0 (0.0)	1.0
Nd:YAG laser goniopuncture	–	3 (10.3)	–
Late complication (>90 days)
Elevated IOP (IOP >25 mmHg)	0 (0.0)	1 (3.4)	0.7
Hypotony (IOP <5 mmHg)	0 (0.0)	2 (6.9)	0.1
Conjunctival leakage	1 (1.3)	0 (0.0)	1.0
Iris incarceration	0 (0.0)	1 (3.4)	0.7
Bleb scar	5 (6.4)	3 (10.3)	0.4
Late intervention
Bleb needling	5 (6.4)	3 (10.3)	0.4
Iris reposition	0 (0.0)	1 (3.4)	0.7
Nd:YAG laser goniopuncture	–	2 (6.9)	–

Notes: Data are absolute values (%) or median (interquartile range), as stated.

a P-values derived from conditional logistic or linear regression, as appropriate.

Abbreviations: 5-FU, 5-fluorouracil; IOP, intraocular pressure; IQR, interquartile range; Nd:YAG, neodymium-doped yttrium aluminum garnet.