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Primary congenital glaucoma is a rare disease that is not usually seen by the general ophthalmologist. Only one out of 10 000–18 000 newly born children in European populations presents with this disease. However, being a disease of usually recessive inheritance, the incidence may be 10 times higher in communities with high consanguinity, and in these cases the disease may manifest early and often in a more severe form. Cases presenting soon after birth are difficult to treat, especially in the presence of cloudy corneas. Most cases without cloudy corneas are diagnosed late, either by the family members or, less frequently, by an ophthalmologist or paediatrician at a routine neonatal examination. Even after the condition has been suspected, the mean interval between detection and first presentation at the ophthalmologist was still 2.2 months according to a recent study1 in Germany despite adequate access to ophthalmic care.
Despite its low incidence, the management of congenital glaucoma is lifelong and largely dependent on surgical intervention. Primary congenital glaucoma occurs once every 12 000 births, giving an incidence of 0.008% as compared with 0.8% in primary open angle glaucoma in adult caucasians.2 3 Hence, only one of 100 new glaucoma patients will be a patient with primary congenital glaucoma. However, the life expectancy of a newborn with primary congenital glaucoma is 5 times longer than the life expectancy of the elderly patient with POAG. Even with a similar frequency of follow-up visits, a patient with primary congenital glaucoma patient would comprise 5% of a general glaucoma practice. However, because of the frequency of follow-up, the proportion may be much higher.
If we assume that the average glaucomatologist is practising for 25–30 years, one newborn affected with congenital glaucoma will need three or more generations of ophthalmologists to care for them. As the therapy is primarily surgical, the longevity of the surgical procedure becomes very important. A congenital glaucoma patient passing away now at the age of 82 years would have had the concepts and technique of treatment of the mid-1920s at their birth. Similarly, a procedure we perform today for these patients will have an impact on the patient’s later life more than twice of our own life expectancy.
A number of surgical approaches have been tried for this condition. Goniotomy was introduced by Barkan4 in 1942 and trabeculotomy was first described by Allen and Burian5 in 1962 and by Harms and Dannheim.6 Hitherto, there have been few attempts, such as 360° trabeculotomy8 to improve, modify and change surgical techniques in congenital glaucoma. This slow evolution in surgical approach owes more to the low incidence of the disease and hence the lack of willingness of the individual surgeon to accept learning curves with changing techniques rather than outstanding surgical success. It may possibly also be due to the fact that different subspecialities care for this disease in different countries, such as the glaucoma specialist in Europe, and the paediatric ophthalmologist in the USA.
In order to improve surgical care for these eyes it should be considered that centres providing surgery for congenital glaucoma should have at least 20 new cases per year as well as considerable experience in adult glaucoma surgery. This means that few centres (even one or two) would cover all new cases of a whole country like UK or Germany with a birth rate of 600 000–700 000 per year. Management of these cases involves considerable aftercare, both in repeated examinations (often under general anaesthesia) and in the management of concomitant amblyopia. Further glaucoma surgery is often needed. In our own studies,1 7 9 the rate of re-operations was between 1.9 and 2.5 if all procedures were counted over the follow-up period, and this rate has been mirrored elsewhere.10
There has been considerable discussion over a long time as to whether goniotomy or trabeculotomy is the better primary surgical approach,7 9 11 and at what stage of the disease other operations are considered—such as combined trabeculotomy/trabeculectomy, trabeculectomy or tube implants—and whether the use of antimetabolites is justified.12 Deciding on the type of procedure is also dependent on the presence or absence of the Schlemm canal which can vary considerably, depending on the form of glaucoma such as primary congenital, secondary congenital with additional angle anomalies (Axenfeld–Rieger, Sturge–Weber, aniridia or other syndromes), or secondary acquired glaucomas such as aphakic childhood glaucoma. Some diagnostic help may be provided from the development and adaptation of new imaging techniques of the anterior segment to visualise the Schlemm canal, that is high-resolution optical coherence tomography (OCT) or ultrasound biomicroscopy (UBM).
The challenges of the congenital glaucoma surgery technique as compared with adult glaucoma surgery particularly lie in the handling of the scleral tissue when dissecting and closing the scleral flap if an outer approach such as a trabeculotomy is used. The 10/0 suture melts easily through the scleral flap tissue of a newborn or very young child, creating holes that may result in overfiltration and hypotony. 11/0 sutures are sometimes needed, using round needles. In addition, there is very little evidence on how to dose antimetabolites if they are needed in refractory cases. In fact, they may exert rather variable actions, particularly if the tissue is soft or the sclera thin.
In paediatric glaucoma care, obviously safer techniques for congenital glaucoma surgery would solve some of these problems. Tamcelik and Özkiris addressed this question in a large comparative retrospective study on viscotrabeculotomy versus classical trabeculotomy, in children of less than 12 months of age, published in this issue (see page 10.1136/bjo.2007.114389).13 Viscotrabeculotomy is a modification of classical trabeculotomy where viscoelastics are injected into Schlemms canal before introducing the trabeculotomy probe. These authors achieved a considerable increase in qualified success (defined by <18 mm Hg) comprising 91,3% in viscotrabeculotomy as compared with 68.6% in classical trabeculotomy in 51 and 58 eyes, respectively, of a cohort of 64 children with a minimum of follow-up of 3 years. Both the number of medications needed and the number of re-operations were more favourable in the viscotrabeculotomy group. They attributed the higher success rate to a dilatation of Schlemm’s canal and a prevention of blood reflux into the anterior chamber. They also hypothezised that suppression of polymerisation of fibrin to fibrinogen would remove the stimulus for fibroblastic proliferation and could contribute to their better results in viscotrabeculotomy. Although this data was retrospectively analysed, the strict selection of including cases only with primary congenital glaucoma with a manifestation at age <1 year, the relatively long minimal follow-up (>3 years), and the rather large number of similar cases make this study a valuable basis for further development of Schlemm canal surgery in congenital glaucoma.
Viscotrabeculotomy is different from viscocanalostomy and other non-penetrating glaucoma surgery such as deep sclerectomy. Deep sclerectomy has been used for congenital glaucoma by some authors14 15 and was discussed conflictingly.15–17
Newer glaucoma surgical techniques like trabecular ablation with special laser technology or electrocautery, stent implantation or choroidal shunts have not yet been sufficiently evaluated for childhood glaucoma but could open up new perspectives of surgery in the future.
In addition to long-term IOP results, functional outcome over longer follow-up periods is crucial when reporting results. For these patients, not only visual acuity and amblyopia but also related problems such as strabismus and binocular vision are an issue.1 18
Concepts for improving surgical techniques in congenital glaucoma surgery are urgently needed. Information on the long-term outcome of surgical procedures used nowadays is even more crucial in childhood glaucoma surgery than in adult glaucoma surgery. The scientific glaucoma community should be encouraged to perform multicentre clinical trials in congenital glaucoma surgery to evaluate and compare present techniques, as well as establish a concept for using antimetabolites in children and develop new surgical techniques. The World Glaucoma Association (WGA), in its educational branch, has recently started an initiative to develop consensus on diagnostic and therapeutic procedures in congenital glaucoma.
Competing interests: None declared.
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