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Editors Selection IGR 17-1
Laser and surgical treatment: Aqueous drainage devices in pediatric glaucoma
Comment by Franz Grehn on:
21178 Aqueous drainage device surgery in refractory pediatric glaucomas: I. Long-term outcomes, O'Malley Schotthoefer E; Yanovitch TL; Freedman SF, Journal of AAPOS, 2008; 12: 33-39
See also comment(s) by James Brandt •21179 Aqueous drainage device surgery in refractory pediatric glaucoma: II. Ocular motility consequences, O'Malley Schotthoefer E; Yanovitch TL; Freedman SF, Journal of AAPOS, 2008; 12: 40-45
See also comment(s) by James Brandt •Pediatric glaucoma surgery is a challenging field of glaucoma care. These children live five times as long as the average elderly POAG patient, and need at least three generations of ophthalmologists to be cared lifelong. Cumulative side effects and failures of surgery thus have a greater impact on vision than they have in POAG surgery. O'Malley Schotthoefer et al. (705 and 708) have undertaken a valuable study to determine the outcomes of tube surgery for the two major problematic types of prediatric glaucomas, i.e., congenital glaucoma and secondary aphakic glaucoma. They report success rate and complication profile in one paper, and the motility consequences in a second paper. Although this is a retrospective approach, this study is a consecutive case series (no cases omitted) and therefore may even have possible advantages over prospective studies: 1) It reports an 'average-life' situation without the optimized follow-up of a prospective study; 2) it has a longer follow-up; and 3) the study includes a rather high number of eyes (cases), namely 38 eyes of 30 children in the congenital glaucoma group and 41 eyes of 32 children in the aphakic group.
The major message of the study is that tubes can have a fairly good success rate in the two types of pediatric glaucoma that were included in the study. Of particular interest is the congenital glaucoma group, because this group is a selection of failed cases, that had had two previous angle surgeries on average, whereas in the aphakic group there were virtually no previous glaucoma surgeries. In addition, the age at surgery was very young in the congenital glaucoma group, i.e., 0.75 yrs, whereas in the aphakic group the age at surgery was 4.3 yrs. Eighty-four percent of the congenital glaucoma cases had corneal edema prior to surgery (not specified whether due to high IOP or previous surgery).
Tubes can have a fairly good success rate in some types of pediatric glaucomaFor the congenital glaucoma group, this data support the view that tubes can be used as an alternative to repeated and probably unsuccessful filtering procedures. This is of particular interest as congenital glaucoma eyes at that age have significantly reduced stiffness of their eye walls, which may make leakage around the tube more likely, tube placement technically more difficult, and hypotony more dangerous as compared to the scleral properties of aphakic eyes at an age of four years. Success rates of both groups were fairly equal: At one year, the success rate of the congenital glaucoma group was 89% and of the aphakic group 90%, respectively. This is encouraging, as it is as high as in prospective tube studies in adult glaucoma. However, the success rate at five years is 70% for both groups (similar to other retrospective studies of primary congenital glaucoma with angle surgery, but better than filtration surgery in aphakic childhood glaucoma), and 42% and 55% for the Kaplan-Meier analysis at ten years. From this data one could conclude that the operation will last for about ten years on average (or: in 50% of cases). Similar to adult tube surgery success rates, a rather high number of additional medications (two for aphakic and three for congenital glaucoma cases on average) are needed to maintain success (i.e., qualified success). Complete success rates (without medication) are not reported. Furthermore, the IOP criterion for success in this study was < 21 mmHg, a target that is no more used in adult glaucoma surgical studies (see European Glaucoma Society Guidelines).
The preponderance of Baerveldt implants in the aphakic group as compared to more Ahmed implants in the congenital glaucoma group may have had some influence on the results. Therefore, no direct conclusions on efficacy should be drawn from comparing the results of the aphakic versus the congenital group. One of the less expected problems of using tubes was the development of six cataracts out of 30 phakic eyes of the congenital glaucoma group, four of which underwent surgery. This is a challenge, as cataract surgery may trigger failure of filtration and increase the risk of retinal detachment, when considered over the whole life expectancy of these children. Tube revision and repositioning was rather frequent in congenital glaucoma cases (i.e., 10/38, five for corneal touch), and in the aphakic group (nine of 41), all for corneal touch. No penetrating keratoplasty due to surgical complications was needed for any case. Retinal detachment was not infrequent (8%), but was always occurring to aphakia.
The complication rate of tubes versus filtering procedures in adult surgery is controversial (see Stein et al., Ophthalmology 2008; 115: 1109-11169; Gedde et al., Am J Ophthalmol 2006). However, the cases of pediatric glaucoma presented here would have had very limited benefit from filtration or angle surgery and therefore cannot be compared with these studies.
Strabismus may be due to the disease itself, particularly in unilateral or asymmetric cases of congenital glaucoma. When tube systems are used, strabismus may also be caused by mechanical alterations. Bearveldt implants are considered more risky for motility problems. However, in this study, no clear difference in the occurrence of motility problems between the two types of implants were obvious (ten motility problems in eyes with Ahmed implant, 12 motility problems in eyes with Baerveldt implant). The rate of horizontal deviations after surgery tripled in the congenital glaucoma group (four before and 12 after) and doubled in the aphakic glaucoma group (seven before and 13 after). Eight new vertical deviations in the congenital glaucoma group and two new vertical deviations in the aphakic group were reported, probably due to the more restricted orbital volume in congenital glaucoma cases (smaller orbit due to younger age, but larger eyes due to buphthalmus).
Binocular function is, of course, a difficult issue to test before surgery and even at an early age after surgery. With the length of follow up of the present study, some of the cases could be tested. Only six out of 33 children that could be tested had fusion or some stereo vision. This is less favorable compared to a recent study on congenital glaucoma of similar follow-up after angle surgery (Alsheikheh et al., Graefes Arch Clin Exp Ophthalmol 2007). In this study, stereopsis (Lang-I test) was positive in 17 out of 30 children who could be tested.
In summary, these two papers add significant information to our understanding of tube surgery in childhood glaucoma and are particularly valuable for developing strategies for aphakic secondary childhood glaucoma and refractory congenital glaucoma.
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