Ultrasound biomicrosopy in glaucoma
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UBM provides high-resolution ultrasound images of ocular structures anterior to the pars plana. It was developed in the 1980s and can be used to evaluate glaucoma mechanisms and treatments. UBM allows quantification of anterior chamber angle structures and assessment of conditions like angle closure, open-angle glaucoma, and filtering surgeries. It provides useful information when the eye precludes examination by other methods due to opacity or anatomy.
Ultrasound biomicrosopy in glaucoma
- 2. Ultrasound biomicroscope (UBM) is a high frequency ultrasound machine used to image ocular structures anterior to the pars plana region of the eye Provides images of the tissues and structures in vivo at microscopic resolution
- 3. Princess Margaret Hospital at Toronto, Canada in 1989. Dr . Stuart Foster
- 4. They developed three probes - 50, 80 & 100 Mhz for clinical trials . 50 MHz is an ideal compromise between depth and resolution to visualize the entire anterior segment. The first commercially available machine was developed by Zeiss in 1991.
- 5. There are three main components of the UBM machine. 1.Transducer 2. High-frequency signal processing. 3. Precise motion control
- 6. This radiofrequency travels the body tissue and is reflected back to the transducer. The reflected radio frequency is processed by the signal processing unit. Transducer The signal processing unit in UBM is specially designed to handle high frequency signals. Subtle movements. Special motion control device. Mounted on a pulley with the piezoelectric crystal fixed on a large handle 50 MHz
- 7. Technique Supine position Eye is open Piezoelectric crystal of the transducer is open Saline or sterile methylcellulose. Crystal of the transducer is placed in saline approximately 2 mm. from the eye surface
- 8. Normal anatomy Lateral resolution - 50µ Axial resolution - 25µ Depth of penetration- 4-5 mm. Field of view is 4 x 4mm Scan rate is 5 frames/second. Cornea is the first structure. Corneo-scleral junction
- 11. Quantification of anterior chamber angle The scleral spur is the most important landmark. Radio-opaque shadow of the sclera merges with the relatively radiolucent shadow of the cornea
- 12. Trabecular iris angle (TIA) – Angle formed with the apex at the iris recess and the arms passing through the TM at a point 500 microns from scleral spur and the point on iris perpendicularly opposite. (30±11 degrees)
- 13. Iris thickness (ID1) – along the same line ID2 – 2 mm from the iris root ID3 – thickest point near the pupillary margin
- 14. Angle recess area – triangular area bordered by the anterior iris surface corneal endothelium and a line perpendicular to the endothelium drawn to the iris surface at a point 750 microns from the scleral spur. Iris irregularity accounted for
- 15. Evaluation of the anterior chamber angle in Asian Indian eyes by UBM and gonioscopy (Kaushik et al) 106 eyes – narrow angles,57 eyes – open anglesNarrow angles Open angles Mean AOD 250 58±49 176±47 Mean AOD500 102±84 291±62 Mean TCPD 653±124 883±94
- 17. Biometry of the Anterior Segment Corneal thickness Anterior chamber depth Posterior chamber depth IOL thickness Iris thickness Ciliary body thickness Scleral thickness . Cannot determine lens thickness
- 18. Determination of the Mechanism of Primary Glaucoma Able to determine the mechanism of elevated IOP (angle-closure vs open-angle) by showing the relationship between the peripheral iris and the trabecular meshwork. Imaging is possible, even in eyes with corneal edema or corneal opacification that precludes gonioscopy.
- 19. Open-angle glaucoma Can measure the anterior chamber angle in degrees Assess the configuration of the peripheral iris Evaluate the iris insertion in relation to the trabecular meshwork
- 20. WIDE OPEN ANGLE WITH FLAT IRIS PLANE
- 21. OPEN ANGLE WITH ANTERIORLY BOWED IRIS PLANE
- 22. Determination of the Occludability of the Angle Dark room provocative testing Studies the spontaneous occlusion of the angle under conditions of decreased illumination Provides useful qualitative information about angle recess anatomy.
- 24. Indentation UBM Apposition closure-angle opens on indentation
- 25. Indentation UBM gonioscopy, new method for assesing the angle Angles widened with indentation. The angle changes in eyes with relative pupillary block were significantly greater than in eyes with peripheral anterior synechie (PAS) or plateau iris configuration (PIC). Useful for diagnosing relative pupillary block, PAS, and PIC.
- 26. Determination of the Mechanism of Secondary Glaucoma Pigment Dispersion Syndrome Wide open angle and typical posterior bowing of the peripheral iris causing reverse pupillary block
- 27. Plateau iris syndrome Abnormally steep anterior angulation of the peripheral iris. Anterior insertion of the iris on to the anterior ciliary body. Can also confirm the double hump sign by use of indentation UBM, a special technique that applies mild pressure on peripheral cornea with the skirt of the eyecup.
- 28. Indentation UBM on an eye with a plateau iris
- 30. IRIS BOMBE
- 31. Pupillary block (A) The angle shows appositional closure owing to anterior bowing of the iris. (B) The angle is open with a flattened iris after laser peripheral iridotomy.
- 32. ANIRIDIA
- 34. Congenital glaucoma Common features- thin stretched out ciliary body, abnormal tissue at the iridocorneal angle, abnormal insertion of the ciliary body In cases of cloudy cornea and unknown previous glaucoma surgery, UBM can be used to identify the type and localization of previous surgery in congenital glaucoma, thus assisting surgical planning for subsequent management
- 35. Post trabeculotomy-remants of tm,iris strands
- 36. POST TRAUMATIC GLAUCOMA Angle recession: Posterior displacement of the point of attachment of the iris to the sclera Widening of the ciliary body face with no disruption of the interface between the sclera and ciliary body.
- 37. Blood in anterior chamber Disinsertion of iris root
- 38. Cyclodialysis cleft Detachment of the ciliary body from its normal location at the scleral spur. Particularly useful in the presence of hazy media, hypotony, and/or abnormal anterior segment anatomy
- 39. PSEUDOPHAKIC AND LENS INDUCED GLAUCOMA Phacomorphic glaucoma Glaucoma due to anterior subluxation of lens. Circumference of intact zonules and the extent of zonular dialysis in pseudoexfoliation syndrome
- 40. In case of intraocular lens (IOL)-induced glaucoma can clearly delineate the position of the optic and haptic especially helpful in pseudophakic bullous keratopathy in determining the cause of glaucoma
- 42. Malignant glaucoma Extremely shallow anterior chamber Occluded angle Forward rotation of the ciliary body with or without fluid in the suprachoroidal space
- 43. Evaluation of Cysts and Tumors Causing Angle Closure Internal character of a lesion (solid or cystic) Resticted anterior ciliary body or is restricted to the iris To measure the full extent of the lesion Progression or regression of the tumor.
- 44. Evaluation of glaucoma therapy Patency of peripheral laser iridotomy
- 45. Determining Functional Status of a Filtering Surgery After trabeculectomy- Patency of sclerostomy aperture Patency of peripheral iridectomy Filtering bleb - flat, shallow, or deep The grading of the bleb is done according to intrableb reflectivity, visibility of the route under the scleral flap, formation of cavernous fluid filled space, and bleb height.
- 46. 4 grades : low reflective (L) high reflective (H) encapsulated (E) flat (F). Eyes with good IOP control mainly have L type blebs. These have low to moderate intrableb reflectivity, a visible intrascleral route and higher intrableb height. F and E blebs generally denote a surgical failure.
- 47. Non-penetrating Deep Sclerectomy Evaluate the functional status of the surgery Can evaluate the thickness and demonstrate a non-perforated continuous trabeculum and Descemets membrane. UBM examination after long-term follow-up shows the presence of an intrascleral space and a filtering bleb. Collagen implants used to augment deep sclerectomy can also be visualized.
- 48. Aqueous drainage tubes UBM is instrumental in diagnosing the presence and cause of occlusion of aqueous drainage device UBM can demonstrate peritubular filtration as a cause of ocular hypotony after glaucoma shunt device implant
- 49. Evaluation of Postoperative Complications after Trabeculectomy UBM can be used to detect and evaluate the extent of postoperative complications such as ciliochoroidal effusion and cyclodialysis. In ciliochoroidal effusion UBM shows the ciliary body to be edematous and separated from the sclera by a sonolucent collection of supraciliary fluid
- 51. UVEITIC GLAUCOMA Uveitis, especially pars planitis, is also an important cause of glaucoma. Greiner et al used UBM to grade pars planitis as follows: grade 0 = no cells grade 1 = mild cells grade 2 = marked cells grade 3 = organization of cells.
- 52. EVALUATION OF SUCCESS OF CILIO- DESTRUCTIVE PROCEDURE UBM has been used to image early and late ciliary body alterations after trans scleral cyclophotocoagulation to establish the position of the ciliary body to ensure correct laser probe placement to locate ciliary body residuals for retreatment, and to rule out scleral damage after the procedure.
- 53. CONCLUSIONS An indispensable tool in qualitative and quantitative assesment of anterior segment. an excellent view of the pathology occurring in the anterior and posterior chambers of the eye and thereby providing a clear insight into the cause of aqueous obstruction.