Primary congenital glaucoma is used to describe the rise of intraocular pressure (IOP) that occurs in the first few months of life due to an abnormality in the aqueous outflow pathways.1 It is the most common type of glaucoma in childhood,2 with variable incidences among different populations,3 and is more common and severe in communities with high rates of consanguineous marriages, such as in the Middle East.4 Primary congenital glaucoma is essentially a surgical disease, with treatment options including angle,5 filtering,6 combined angle and filtering,4,7 and tube8 surgery, and cyclodestruction.9 More severe cases such as those that are worse at presentation and present early (eg, those presenting in the Middle East) reportedly fare better with combined angle and filtering procedures than either alone.5 Filtering surgery is dependent on the creation and maintenance of a patent fistula between the anterior chamber and subconjunctival space. Fibrosis in the latter is a feared sequela in younger patients, hence the need for wound modulating agents, including mitomycin C, 5-fluorouracil, and, more recently, anti-vascular endothelial growth factors8 (prototype: bevacizumab). Of those in common use, intra-operative application of mitomycin C remains an effective and potent option. There is considerable variation among glaucoma surgeons in the concentration and duration of mitomycin C applications, ranging from 0.1 to 0.5 mg/mL10–12 and from 1 to 5 minutes13–16 of application. There is no prospective study comparing two different durations of mitomycin C application in filtering or combined procedures in primary congenital glaucoma. It is the author's preference to perform combined angle and filtering procedures for cases of primary congenital glaucoma, even in those few cases presenting with clear corneas. This study was conducted to compare the effect of two different intraoperative exposure durations of 0.4 mg/mL of mitomycin C in combined angle and filtering surgery for primary congenital glaucoma.
Patients and Methods
The study was conducted on 75 eyes of 54 children diagnosed as having primary congenital glaucoma who were operated on in the Department of Ophthalmology at Alexandria Main University Hospital, Alexandria, Egypt. The study was approved by the local ethics committee of the Faculty of Medicine of Alexandria University. Informed consent was obtained from the care providers of all children involved in the study. All surgeries were performed by the same surgeon (NHB).
All study eyes underwent combined trabeculotomy–trabeculectomy with mitomycin C.15 In brief, for all operated eyes, a fornix-based conjunctival flap and a triangular scleral flap 4 × 4 × 4 mm in size were fashioned. Study eyes were then randomized by a coin flip (conducted by an attendant nurse, with three coin flips performed per choice) to determine mitomycin C application (0.4 mg/mL) underneath the scleral flap for a duration of either 1 (MMC 1 group; 35 eyes of 24 children) or 2 (MMC 2 group; 40 eyes of 30 children) minutes. This was followed by thorough irrigation, localization of Schlemm's canal, trabeculotomy (using a Neuhann trabeculotome to open 60° of the angle on either side of the incision, totaling 120°), trabeculectomy (using Kelly punch), peripheral iridectomy, and closure of the scleral flap (10-0 nylon sutures inserted at the apex and on either side of the triangular scleral flap and kept moderately tight to allow egress of fluid injected into the anterior chamber through a paracentesis with the anterior chamber maintained) and conjunctiva (10-0 nylon mattress suture). Filtration was titrated at the end of the surgery by fluid injected through a paracentesis, allowing slow elevation of a conjunctival filtering bleb with the anterior chamber maintained.
The postoperative treatment included topical steroid (dexamethasone) eye drops to be administered hourly and gradually tapered during a period of 6 weeks, and topical antibiotic (gatifloxacin) and topical cycloplegic (cyclopentolate) eye drops five and three times daily for 6 weeks, respectively.
Postoperative examinations were conducted on day 1 (office examination) postoperatively, followed by examinations under anesthesia at 1, 3, 6, 9, 12, and 24 months. Because the IOP may not be adequately controlled, with the possibility of progressive optic nerve damage and without corneal signs that would be evident in an office examination, and it may not be possible to accurately obtain data with an office examination, examinations under anesthesia were conducted at every follow-up time point. No anesthesia-related adverse event occurred during the study. Examinations under anesthesia in the Alexandria Main University Hospital are conducted via sevoflurane inhalational anesthesia. Due to the known effect of inhalational anesthesia on measured IOP (artifactually lower), the examination circumstances were standardized for all patients and eyes examined regarding the anesthetic, technique, and timing of IOP measurement (immediately following induction of anesthesia and before any manipulation of the airway).
Due to the absence of bleb grading systems specific to childhood glaucoma surgery, blebs were evaluated according to parameters similar to those used in the Indiana Bleb Appearance Grading Scale system,17 with minor simplifications. The three other parameters evaluated were vascularity (pale or vascular), elevation (low or elevated), and extent (diffuse or localized). Special attention was given to the development of cystic blebs. Figure A (available in the online version of this article) shows different bleb morphologies encountered in the study eyes.
Composite image showing different bleb morphologies encountered in the included eyes: (A) pale, low bleb; (B) pale, elevated bleb; (C) injected, low bleb; (D) injected, low bleb; (E) pale, elevated bleb; (F) injected, elevated bleb; (G) pale, cystic bleb; (H) pale, cystic bleb; (I) injected, cystic bleb; and (J) pale, cystic bleb.
Success of the initial glaucoma surgical procedure was defined by a composite primary end point18 of an IOP of less than 16 mm Hg under general anesthesia, without any IOP-lowering medications and with no hypotony-related complications and/or lack of IOP-related progression of the disease as evidenced by worsening of the ocular biometric characteristics (eg, the corneal diameter, axial length, or cup–disc ratio) beyond the normal for the age group studied. The need for another surgical intervention classified that eye as a failure and complications were noted.
Data were analyzed using SPSS software (version 20; SPSS, Inc., Chicago, IL). The distribution of quantitative variables was tested for normality using the Kolmogorov–Smirnov test. The correlation between quantitative variables was tested using the Spearman rank correlation test. Quantitative variables were compared between groups using the Mann–Whitney U test and over different time points using the Friedman test. The Pearson chi-square test was used to test the association between two qualitative variables. In all statistical tests, a P value of .05 was used, below which the results were considered to be statistically significant. A power calculation was not done for this study.
The study was conducted on 75 (40 right, 54%) eyes of 54 (29 males, 53.7%) children with primary congenital glaucoma. The mean age at presentation was 6.7 ± 4.1 months (range: 2 to 16 months; median: 6 months) and 7.7 ± 5.7 months (range: 1 to 32; median: 6.5 months) in the MMC 1 and MMC 2 groups, respectively (P = .538). The baseline demographic and clinical characteristics of the study groups are presented in Table 1. There were no statistically significant differences between the study groups with regard to age (P = .538), gender (P = .585), laterality (P = .531), or preoperative clinical characteristics. The clinical examination data of the eyes that were successful in the initial procedure are presented in Table A and Figure B (available in the online version of the article) and the bleb characteristics of the study eyes are presented in Table 2.
Patient Demographics and Baseline Clinical Characteristics
Composite image demonstrating line graphs of the clinical examination data of the included eyes with successful initial surgical procedure. IOP = intraocular pressure; MMC 1 group = patients who underwent combined trabeculotomy–trabeculectomy with intraoperative mitomycin C application for 1 minute; MMC 2 group = patients who underwent combined trabeculotomy–trabeculectomy with intraoperative mitomycin C application for 2 minutes; C/D = cup–disc
Bleb Characteristics Among Study Groups at Final Follow-up Time Point
The IOP was statistically insignificantly lower in the MMC 2 group than in the MMC 1 group at all follow-up time points, except for a marginal significance at postoperative month 6 that was not maintained thereafter (P values preoperatively and 1, 3, 6, 9, 12, and 24 months postoperatively: .543, .400, .546, .032, .233, .536, and .718, respectively). Both groups demonstrated a statistically and clinically significant reduction of IOP from the preoperative values at all follow-up time points (P values at 1, 3, 6, 9, 12, and 24 months postoperatively: < .001, < .001, < .001, < .001, < .001, and < .001 for the MMC 1 group, and < .001, < .001, = .003, = .003, = .001, and = .001 for the MMC 2 group, respectively). Reversibility of optic nerve cupping was noted in both groups at all postoperative follow-up time points. All blebs were Seidel negative. The bleb appearance at the end of the follow-up period was different for both groups; blebs were pale, low, and diffuse in the MMC 1 group and elevated, localized, and cystic, although equally pale in the MMC 2 group. There were no statistically significant differences between groups in any of the studied bleb characteristics.
The percentage of success in the MMC 1 and MMC 2 groups was 91.5% and 78.5%, respectively. The time intervals to failure of the initial glaucoma surgical procedure are presented in Table 3. Evidence of success or failure was checked at every postoperative follow-up evaluation. All failed eyes in both groups presented with a cloudy cornea. Parental consanguinity was present in failed patients in 56% and 100% of eyes in the MMC 2 and MMC 1 groups, respectively. There was no statistically significant difference between the failed eyes in either group regarding age at presentation or the preoperative clinical characteristics except for the corneal diameter, which was notably higher in the MMC 2 group, although clinically insignificant. There were no statistically significant differences between the success rates among the study eyes at all time points. Figure 1 presents the Kaplan–Meier survival curves for the success rates of both procedures.
Time Intervals to Failure of First Procedure and the Clinical Criteria of Failed Eyes
Kaplan–Meier survival curves for the success rates of both procedures. MMC 1 group = patients who underwent combined trabeculotomy–trabeculectomy with intraoperative mitomycin C application for 1 minute; MMC 2 group = patients who underwent combined trabeculotomy–trabeculectomy with intraoperative mitomycin C application for 2 minutes
The estimated survival rates were 22.4 (95% confidence interval [CI]: 20.8 to 24.1) and 20.2 (95% CI: 17.9 to 22.8) for the MMC 1 and MMC 2 groups, respectively, which were not statistically significantly different (P = .106). Complications noted (Table 4) included posterior subcapsular cataracts that developed in a total of 4 eyes (2 eyes in each group). Additionally, 3 eyes (7.5%) in the MMC 2 group developed hypotony optic disc edema that persisted throughout the 24 months of follow-up. There were eyes in both groups that maintained an IOP reading of 0 mm Hg, although only 3 eyes (of 3 patients) in the MMC 2 group developed optic disc edema. This complication was not encountered in the MMC 1 group. None of the included eyes developed any infectious complication (eg, blebitis or bleb-associated endophthalmitis) during the study period of 24 months. For the eyes that failed the initial glaucoma surgical procedure, none of the demographic or preoperative clinical characteristics were correlated to the failure. No anesthesia-related adverse event occurred during the study.
The aim of the current study was to compare the outcome of combined angle and filtering surgery for primary congenital glaucoma using two exposure durations of 0.4 mg/mL of mitomycin C. The demographic data of the study patients reveals a slight male preponderance, which is in accordance with reports of primary congenital glaucoma being more common in males,19–21 and presentation commonly within the first year of life, which is similar to most cases of primary congenital glaucoma.2,21 Studying the clinical data of the two study groups demonstrated that there was no significant difference in success rates between groups. Additionally, there seemed to be a trend for a higher failure rate at 2 years in the MMC 2 group (23% vs 9% for the MMC 2 vs MMC 1 group, respectively; Table 3).
Although the IOP is an important criterion for diagnosis and follow-up, this must be considered in the context of the known effect of inhalational anesthesia on measured IOP; hence, standardization of examination circumstances is important. Both mitomycin C exposure durations were equally successful in reducing the IOP and controlling the disease condition. This is in line with other reports on the efficacy of combined angle and filtering procedures in controlling IOP in primary congenital glaucoma.4,7,22 Additionally, the longer exposure duration (2 minutes) was associated with a clinically insignificantly lower IOP throughout the 2 years of follow-up and the occurrence of hypotony-related optic disc edema.
An additional feature already reported in childhood glaucoma in general,23,24 the reversal of optic disc cupping, was also demonstrable in both arms of the study.
Bleb morphology is a major concern in glaucoma filtering surgery. The development of thin, cystic, avascular blebs is already documented with antimetabolite use,4,10 although one recent report refutes this.6 The findings in the current study are in line with the shorter exposure duration in Jayaram et al.'s study.6 Alternatively, the longer exposure duration was associated with more blebs being pale, localized, elevated, and, most importantly, cystic.6 Although none occurred in the current study period, infectious complications remain a lifelong risk in such unhealthy blebs.
Another safety issue related to the study design is the repeated examinations under anesthesia at every follow-up time point. In the short term, inhalational sevoflurane anesthesia is safe and no anesthesia-related event occurred during the study. In the long term, there are concerns about the repeated exposure to inhalational anesthetics on the long-term neurological and cognitive development of children.25 Unfortunately, this is an issue that will be clarified only with long-term follow-up.
Studying the eyes that were not successfully treated in either group revealed that no preoperative demographic or clinical characteristic could be related to the cause of failure, although other reports cite younger ages at the time of surgery as associated with higher failure rates.26 It might be possible that patients who were not treated successfully represented genetically distinct forms of primary congenital glaucoma with greater degrees of severity.
Limitations of the current study include the addition of an angle procedure to the filtering procedure rather than testing the filtering procedure effect in isolation, the comparison of only two exposure durations of one concentration of mitomycin C rather than extending the study to include arms with different mitomycin C concentrations and/or different exposure durations, the lack of formal assessment of visual function for the study eyes, the inclusion of both eyes of some patients in the data analysis rather than one eye only, the relatively small sample size, and the relatively short follow-up duration of only 2 years. Extended reports of longer follow-up durations are likely to yield valuable data and are thus encouraged. Additionally, lack of genetic testing for study patients might have resulted in inclusion of genotypically distinct, although phenotypically identical, children, with the resultant inherent inaccuracy of comparing the results of surgical procedures.
Because both exposure durations of mitomycin C yielded comparable postoperative IOP values and the longer exposure durations were associated with a more unhealthy bleb appearance, higher reoperation rate, and higher chance of hypotony-related complications, there seems to be no advantage in using mitomycin C with an exposure duration of 2 minutes. A mitomycin C exposure duration of 1 minute would be recommended for use in combined angle and filtering surgery for primary congenital glaucoma.
- Weinreb RN, Grajewski AL, Papadopoulos M, Grigg J, Freedman S. Childhood Glaucoma: WGC Consensus 9. Amsterdam, the Netherlands: Kugler; 2013:6.
- Aziz A, Fakhoury O, Matonti F, Pieri E, Denis D. Epidemiology and clinical characteristics of primary congenital glaucoma [article in French]. J Fr Ophtalmol. 2015;38:960–966. doi:10.1016/j.jfo.2015.04.018 [CrossRef]
- Taylor RH, Ainsworth JR, Evans AR, Levin AV. The epidemiology of pediatric glaucoma: the Toronto experience. J AAPOS. 1999;3:308–315. doi:10.1016/S1091-8531(99)70028-5 [CrossRef]
- Al-Hazmi A, Awad A, Zwaan J, Al-Mesfer SA, Al-Jadaan I, Al-Mohammed A. Correlation between surgical success rate and severity of congenital glaucoma. Br J Ophthalmol. 2005;89:449–453. doi:10.1136/bjo.2004.047761 [CrossRef]
- Girkin CA, Rhodes L, McGwin G, Marchase N, Cogan MS. Goniotomy versus circumferential trabeculotomy with an illuminated microcatheter in congenital glaucoma. J AAPOS. 2012;16:424–427. doi:10.1016/j.jaapos.2012.05.013 [CrossRef]
- Jayaram H, Scawn R, Pooley F, et al. Long-term outcomes of trabeculectomy augmented with mitomycin C undertaken within first 2 years of life. Ophthalmology. 2015;122:2216–2222. doi:10.1016/j.ophtha.2015.07.028 [CrossRef]
- Mandal AK, Bhatia PG, Bhaskar A, Nutheti R. Long-term surgical and visual outcomes in Indian children with developmental glaucoma operated on within 6 months of birth. Ophthalmology. 2004;111:283–290. doi:10.1016/j.ophtha.2003.05.027 [CrossRef]
- Mahdy RA. Adjunctive use of bevacizumab versus mitomycin C with Ahmed valve implantation in treatment of pediatric glaucoma. J Glaucoma. 2011;20:458–463. doi:10.1097/IJG.0b013e3181efbea5 [CrossRef]
- Autrata R, Rehurek J. Long-term results of transcleral cyclophotocoagulation in refractory pediatric glaucoma patients. Ophthalmologica. 2003;217:393–400. doi:10.1159/000073068 [CrossRef]
- Rodrigues AM, Júnior AP, Montezano FT, de Arruda Melo PA, Prata J Jr, . Comparison between results of trabeculectomy in primary congenital glaucoma with and without the use of Mitomycin C. J Glaucoma. 2004;13:228–232. doi:10.1097/00061198-200406000-00010 [CrossRef]
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- Ozkiris A, Tamcelik N. Long-term results of trabeculectomy with different concentrations of mitomycin C in refractory developmental glaucoma. J Pediatr Ophthalmol Strabismus. 2005;42:97–102.
- Giampani J Jr, Borges-Giampani AS, Carani JCE, Oltrogge EW, Susanna R Jr, . Efficacy and safety of trabeculectomy with mitomycin c for childhood glaucoma: a study of results with long-term follow-up. Clinics (Sao Paulo). 2008;63:421–426. doi:10.1590/S1807-59322008000400002 [CrossRef]
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Patient Demographics and Baseline Clinical Characteristics
|Characteristics||MMC 1 Group||MMC 2 Group||P|
|Patients||24 (100%)||30 (100%)||.585|
| Male||13 (54%)||16 (53%)|
| Female||11 (46%)||14 (47%)|
|Eyes||35 (100%)||40 (100%)||.531|
| Right||19 (54%)||21 (53%)|
| Left||16 (46%)||19 (48%)|
|Age at presentation (mo)||.538|
| Mean ± SD||6.7 ± 4.1||7.7 ± 5.7|
| Range||2 to 16||1 to 32|
|Preoperative IOP (mm Hg)||–|
| Mean ± SD||18.4 ± 5.1||18.1 ± 6.1|
| Range||10 to 34||6 to 30|
|Preoperative corneal diameter (mm)||–|
| Mean ± SD||13.0 ± 0.9||13.0 ± 0.8|
| Range||10.5 to 15||11 to 14|
|Preoperative cloudy cornea||29 (83%)||33 (83%)||–|
|Preoperative C/D ratio||–|
| Mean ± SD||0.7 ± 0.2||0.7 ± 0.2|
| Range||0.2 to 1||0.1 to 1|
|Preoperative axial length (mm)||–|
| Mean ± SD||23.53 ± 1.91||23.99 ± 1.93|
| Range||20.82 to 26.61||21.42 to 30.59|
Bleb Characteristics Among Study Groups at Final Follow-up Time Point
|Characteristic||MMC 1 Group (n = 35)||MMC 2 Group (n = 40)||P|
| Pale||34 (97.1%)||38 (95%)|
| Vascularized||1 (2.9%)||2 (5%)|
| Low||29 (82.9%)||28 (70%)|
| Elevated||6 (17.1%)||12 (30%)|
| Diffuse||26 (74.3%)||21 (52.5%)|
| Localized||9 (25.7%)||19 (47.5%)|
|Cystic||6 (17.1%)||13 (32.5%)||.20|
Time Intervals to Failure of First Procedure and the Clinical Criteria of Failed Eyes
|Criteria||MMC 1 Group (3 Eyes, 8.5%)||MMC 2 Group (9 Eyes, 22.5%)||P|
| Males||1 (33%)||4 (44%)||–|
| Females||2 (67%)||5 (56%)||–|
| Right||1 (33%)||6 (67%)||–|
| Left||2 (67%)||3 (33%)||–|
|Time interval of first procedure failure (mo)||–|
| Mean ± SD||6.1 ± 1.8||7.3 ± 6.0|
| Range||4.3 to 7.9||2.6 to 21.6|
|Age at presentation (mo)||.158|
| Mean ± SD||3.7 ± 1.5||5.4 ± 3.8|
| Range||2 to 5||1 to 13|
|Preoperative IOP (mm Hg)||.191|
| Mean ± SD||17.3 ± 3.1||20.2 ± 3.9|
| Range||14 to 20||14 to 26|
|Preoperative corneal diameter (mm)||.036|
| Mean ± SD||12.5 ± 0.5||12.9 ± 1.4|
| Range||12 to 13||10 to 14.5|
|Preoperative cloudy cornea||3 (100%)||3 (33%)|
|Preoperative C/D ratio||.500|
| Mean ± SD||0.8 ± 0.14||0.8 ± 0.07|
| Range||0.7 to 0.9||0.7 to 0.9|
|Preoperative axial length (mm)||.413|
| Mean ± SD||22.82 ± 1.95||22.66 ± 1.75|
| Range||21.53 to 25.08||19.63 to 25.91|
|Complication||MMC 1 Group||MMC 2 Group|
|Eyes||35 (100%)||40 (100%)|
|Posterior subcapsular cataracts||2 (6%)||2 (5%)|
|Hypotony optic disc edema||–||3 (8%)|
|Clinical Examination Data of study eyes with successful initial Surgical Procedure|
|Mean (± standard deviation, range, median)||Preop||1 month||3 months||6 months||9 months||12 months||24 months|
|Intraocular pressure (mmHg)||MMC 1||18.4 (5.1, 10 – 34, 17)||8.2 (4.9, 1 – 20, 8)||7.6 (2.9, 3 – 13, 8)||7.4 (3.8, 1 – 14, 7)||6.8 (2.3, 2 – 10, 8)||5.3 (2.5, 0 – 10, 5.5)||5.5 (3.5, 0 – 16, 6)|
|MMC2||18.1 (6.1, 6 – 30, 18)||6.0 (4.0, 0 – 18, 6.0)||6.5 (4.2, 0 – 16, 6)||4.5 (2.3, 0 – 8, 4)||4.9 (3.2, 0 – 10, 5.5)||5.3 (3.1, 0 – 12, 6)||4.8 (2.8, 0 – 10, 6)|
|Corneal Diameter (mm)||MMC 1||13.0 (0.9, 10.5 – 15, 13)||12.9 (0.9, 10.5 – 15, 13)||13.1 (0.9, 10.5 – 15, 13)||12.9 (0.9, 10.5 – 14, 13)||13.1 (0.8, 11.5 – 15, 13)||13.3 (1.0, 11 – 15, 13.5)||13.3 (0.8, 11 – 14, 13.5)|
|MMC 2||13.0 (0.8, 11 – 14, 13)||12.9 (0.8, 11 – 14.5, 13)||12.9 (0.6, 11 – 14, 13)||13.0 (0.5, 12 – 14, 13)||12.8 (0.7, 11.5 – 14, 12.8)||13.2 (0.6, 12 – 15, 13)||13.1 (0.6, 11.5 – 14, 13)|
|Cup-disc ratio||MMC 1||0.7 (0.2, 0.2 – 1, 0.7)||0.4 (0.4, 0 – 1, 0.3)||0.4 (0.4, 0 – 1, 0.4)||0.5 (0.4, 0 – 1, 0.5)||0.5 (0.3, 0 – 0.9, 0.4)||0.4 (0.3, 0 – 0.9, 0.4)||0.4 (0.4, 0 – 1, 0.3)|
|MMC 2||0.7 (0.2, 0.1 – 1, 0.7)||0.3 (0.2, 0 – 0.9, 0.3)||0.4 (0.3, 0 – 0.8, 0.4)||0.4 (0.3, 0 – 0.7, 0.3)||0.3 (0.3, 0 – 0.7, 0.2)||0.4 (0.3, 0 – 0.8, 0.4)||0.4 (0.4, 0 – 1, 0.1)|
|AL (mm)||MMC 1||23.53 (1.91, 20.82 – 26.61, 23.29)||23.16 (1.91, 19.94 – 25.96, 23.23)||23.21 (1.81, 20.05 – 26.85, 23.37)||23.79 (1.81, 21.19 – 26.85, 23.47)||23.79 (2.22, 20.71 – 27.86, 23.70)||24.28 (1.74, 20.85 – 27.62, 24.44)||24.08 (1.87, 21.31 – 27.41, 24.07)|
|MMC 2||23.99 (1.93, 21.42 – 30.59, 23.96)||22.87 (1.51, 20.50 – 28.18, 22.64)||22.92 (1.14, 20.71 – 24.76, 22.79)||22.96 (1.46, 21.91 – 26.91, 22.22)||22.74 (1.18, 21.13 – 25.56, 22.76)||23.00 (1.37, 20.73 – 25.59, 23.10)||23.33 (1.93, 21.42 – 29.1, 22.97)|