الفهرس 
Aim of the workOnly 14 pages are availabe for public view
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Abstract
Glaucoma in infants is commonly associated with structural abnormalities of the anterior segment of the globe. High resolution imaging of the anterior segment in eyes with infantile glaucoma could help in determining the nature and extent of structural abnormalities and influence therapeutic decision making.
With UBM, the anterior chamber (AC) angle, iris, ciliary body, lens and posterior chamber (PC) can be imaged in details in infants with glaucoma. In these patients, the anterior segment anatomy could not be seen because of dense corneal opacities (Azuara-Blanco, 1997).
Primary infantile glaucoma or trabeculodysgenesis is the most common glaucoma of infancy, these cases have an isolated maldevelopment of trabecular meshwork not associated with other developmental ocular anomalies.
The presence of elongated ciliary processes in congenital glaucoma had been previously described and proved by histopathological examination, and explained as a result of inward traction due to the enlarging diameter of the eye creating traction on the zonules attached to a non enlarging lens (Maumenee, 1959). In the year 2000, Dietlein and his colleagues emphasized also the unique morphology of the ciliary body with massively elongated processes.
Prominent schwalbe’s line could be identified as a point of high reflectivity echoes at the back of the corneal periphery to which the iris was adherent. In these cases there is association with iris hypoplasia as a constant finding that proved the diagnosis of Reiger’s anomaly. Previous description of hypertrophies anteriorly placed schwalbe’s line as a highly reflective internal band was given by Pavlin and Foster, (1995).
High IOP induces corneal oedema in infantile eyes and hampers inspection of the anterior segment. Consequently UBM is useful for assessing the morphology of the anterior segment. For example when Peter’s anomaly is clinically suspected, the diagnosis is only confirmed by UBM. Moreover, value of UBM raised when diagnosis of Peter’s anomaly was made as absence of Decsemet’s membrane with lenticulocorneal touch at the site of posterior notching was found in presence of corneal opacity that may change the surgical decision for such a case. Azaura-Blanco and his colleagues in 1997 reported similar findings regarding the diagnosis of Peter’s anomaly using UBM in 3 cases by Nischal and his colleagues declared the value of UBM in confirming the diagnosis of Peter’s anomaly in 70% of eyes examined with congenital corneal opacification.
Thinning of the iris was found in cases with trabeculodysgenesis as well as in all cases with Riger’s and Peter’s anomalies. In 1982 Quigley speculated that as the eye enlarge, the iris is stretched and the overlying stroma appears thin.
Ciliary body hypoplasia was diagnosed by a decrease in number and thickness of ciliary processes; this was described by Okamoto and his coworkers in 2004. In aniridic patients accompanied with iris hypoplasia, they speculated that hypoplasia of ciliary body influences the uveoscleral out flow, which may, at least in part, play a role in development of glaucoma.
UBM is able to reveal anterior chamber angle configuration in cases with primary congenital glaucoma with no previous surgical history as well as the specific morphologic patterns of different glaucoma procedures. As the situation in refractory glaucoma often seems disparate to the parents, the tendency to seek treatment in different ophthalmic centers is remarkably high.
The history of previous pressure lowering surgery is often extensive and the topography of glaucoma interventions can be unclear, even in the rare cases in which documentations is available. Under these circumstances, UBM can be of great help for identifying the previously treated area or even recognizing the type of glaucoma surgery, especially if gonioscopy is unfeasible because of corneal opacities.
Cases with no previous surgical managements had a specific AC angle configuration defined by UBM. It comprised a relatively wide chamber angle, insertion of the iris in front of the scleral spur and highly reflective tissue strands in front of the trabecular meshwork. These findings are in agreement with those reported in 2000 and 2002 by Dietlein, Cheweikh and their co workers respectively.
In areas of the angle treated with goniotomy, a triangular cleft at the region of the trabecualr meshwork was detected. This finding was the hallmark of the procedure and was present in all cases regardless of IOP control. Azuara-Blanko et al., 1997, Dietlein et al., 2000 and El-Cheweikh et al., 2002 reported similar findings.
Trabeculotomy could also be detected as a discontinuation within the highly reflective strands in front of trabecular meshwork with recession of iris behind scleral spur. Dietlein and his co workers in 2000 reported similar findings, however, they also reported the presence of highly reflective tissue remnants at the trabeculotomy site, supposedly belonging to the posterior of the trabecular meshwork.
Sagging of iris was found in the areas of the angle exposed to previous operation. This is consistent with hypothesis that thickened cords of uveal meshwork hold the iris anteriorly preventing the scleral spur from rotating possteriorly, thus superficial incision of the thickened uveal meshwork allow the iris root to DROP posteriorly with accompanying posterior rotation of the scleral spur (Maumenee, 1959).
The relationship between morphology seen by UBM and the effectiveness of surgery seems tenous. The correlation between UBM finding and pressure reducing techniques effectiveness could be governed by unknown factors. Moreover, UBM analysis after glaucoma microsurgery is subjected to technical limits of resolution as reported by Dietlein et al., in 2000. Also El-Cheweikh and her co workers in 2002 had the same conclusion.
UBM is also useful in demonstrating and consequently proper management of some postoperative complications which weren’t detected clinically due to the presence of corneal opacity as post operative iritis with inflammatory cells in the AC and PC associated with inflammatory membrane following trabeculotomy.
In 2007, Gupta and co workers reported a quantitative information about morphology and measurements of the anterior segment in the cases of congenital glaucoma, which will help in the decision and undergoing pressure lowering surgery in these cases.
In 2008 Oberacher-Velten and his colleagues reported that corneal ultrasound biomicroscopic pachymetry appears to be a valuable additional measure in the follow-up of infants and small children requiring glaucoma surgery.
In 2009 See reported that UBM is one of the more recently various imaging modalities that allow a more objective assessment of the anterior segment structures and peripheral anterior chamber depth that can used in mass screening programs for eyes at risk of angle closure glaucoma.
UBM is an imaging technique that uses high frequency ultrasound to produce images of the eye at near microscopic resolution.
UBM probe with a 50 MHz transducer, achieves a resolution of approximately 50 microns and has tissue penetration of 4-5 mm. thus it allows detailed observation of the anterior segment of the eye in a way that helped us in studying different types of glaucoma.
Moreover, UBM is of great value in congenital glaucoma especially in cases with corneal opacities. It could demonstrate associated congenital anomalies and could determine different types of primary congenital glaucoma.
As the situation in refractory glaucoma often seems desperate to the parents, the tendency to seek treatment in several different ophthalmic centers is remarkably high. The history of previous lowering surgery is often extensive and the topography of glaucoma interventions can be unclear, even in the rare cases in which documentation is available.
Under these circumstances, UBM can be of great help for identifying the previous treated area or even recognizing the type of glaucoma surgery, especially if gonioscopy is unfeasible because of corneal opacities.
Ultrasound biomicroscopy is proved to be a useful non invasive method for evaluating infants with glaucoma especially in cases with corneal opacities.
UBM could demonstrates associated congenital anomalies and differentiate different types of primary congenital glaucoma.
UBM proved to be the only way to confirm a diagnosis of Peter’s anomaly when clinically suspected.
In cases of unknown previous glaucoma surgery, UBM can be used to identify the type and to localize the site of previous surgery in congenital glaucoma. Thus assisting surgical planning for subsequent glaucoma management.
The correlation between the UBM morphology and the effectiveness of filtering surgery is less convincing than previously demonstrated in adults, possibly underlining the importance of individual non surgical factors for prognosis in congenital glaucoma,
Future studies with the use of higher resolution UBM probes can succeed in visualizing and assessment of trabecular meshwork and sclemm’s canal.