Ultrasound biomicroscopy (U B M), developed by Pavlin et al. in
1995, uses high frequency ultrasound (50 MHz) to produce in vivo image
of the anterior segment with resolution as high as 50 um. It is possible to
study in detail and to quantify precisely anatomic relations among the
anterior segment structures (Pavlin et al., 2008).
The advantages of UBM for glaucoma alongside OCT that the
resolution is quite good with OCT, but because it uses optical waves, the
big limitation is its ability to visualize what's happening behind the iris
pigment epithelium. UBM's acoustic waves enable us to see behind the
iris to get a complete anterior segment picture (Ahmed, 2011).
The advantages of UMB over OCT that UBM gives the ability to
see the interior structure of the eye lesions included (iris nevi and iris
cysts). Cyst walls and ciliary body cysts can be visualized much better
with the UBM. OCT certainly delivers very good corneal and anterior
chamber angle imaging, but UBM goes deeper (Ahmed, 2011).
Ultrasound biomicroscopy is used to study the functional anatomy
of the filtering bleb using high frequency (50 MHz) probe, which
provides high resolution of image of filtering blebs. It was possible to
obtain longitudinal and transverse images of filtering blebs, to measure
the height, to evaluate the reflectivity inside and to follow the route under
the scleral flap, so a correlation between bleb shape and intraocular
pressure could be evaluated in glaucomatous patients treated with
trabeculectomy (Avitabile et al., 1998).
Ultrasound biomicroscopy was used to examine the aqueous
drainage route beneath the scleral flap. The thickness of the aqueous
2
Introduction
drainage route beneath the scleral flap was found to be correlated with the
development of a filtering bleb. The size of the bleb was correlated with
the intraocular pressure. Thus, preservation of the aqueous drainage route
beneath the scleral flap probably influenced by the development of a
filtering bleb following trabeculectomy (Jinza et al., 2000).
Trabeculectomy is performed as a treatment for many types of
glaucoma in an attempt to lower the intra-ocular pressure. Mitomycin C
is an antimetabolite applied between the sclera and conjunctiva during the
initial stages of trabeculectomy to prevent excessive post-operative
scarring and thus reduce the risk of failure. Intra-operative mitomycin C
reoduces the risk of surgical failure in eyes that have undergone no
pervious surgery and in eyes at high risk of failure e.g. uveitic, aphakic,
pseudophakic and neovascular glaucomas (Wilkins et al., 2003).
In a study performed by Okada et al., 2009, the MMC was
reported to inhibit expression and effect of chymase and mast cells in the
conjunctival scar after trabeculectomy. |
