Gonioscopy PDF

NV3234 GONIOSCOPY Dr Sumithira Narayanasamy Angle structure - refresh Anterior chamber angle (ACA) of the eye  anatomical angle created by the root of the iris and the peripheral corneal vault.  Is made up these structures  Iris  Ciliary Body (CB) – longitudinal muscle of t...

NV3234 GONIOSCOPY Dr Sumithira Narayanasamy Angle structure - refresh Anterior chamber angle (ACA) of the eye  anatomical angle created by the root of the iris and the peripheral corneal vault.  Is made up these structures  Iris  Ciliary Body (CB) – longitudinal muscle of the eye  Scleral Spur (SS) – protrusion of sclera into the anterior chamber  Trabecular Meshwork (TM) – drains aqueous humor via anterior chamber, divided into anterior and posterior section  Schwalbe’s Line (SL) – end of descemet’s membrane, a very fine glossy line Why evaluate anterior chamber angle? ❑ Accurate diagnosis of glaucoma (open angle or close angle) ❑ Detect potential risk of angle closure prior to pupil dilation ❑ To rule out anterior segment inflammation ❑ Suspicion of peripheral anterior synechiae, angle recession or iridodialysis post-trauma Angle evaluation techniques ❑ Pen torch method ❑ Smith’s method ❑ Van Herrick’s technique ❑ Split limbal technique ❑ Gonioscopy ❑ Optical coherence tomography (OCT) Pen torch method  The simplest technique (small children or biomicroscope not possible)  Eye is shined with pen torch at temporal canthus  Based on the amount of eye illuminated the ACA can be graded  Limitation:  Not very accurate – influenced by penlight position Van Herick’s technique  A quantitative method of assessing the size of the ACA using the slit lamp biomicroscope.  Compare the size of an optic section width on the cornea to the gap between the section and the reflection on the iris.  An angle of 60° should be used consistently to allow for standardisation of measurements.  Limitation:  Unable to assess superior angle, which is most likely to close Grading gonioscopy Gonioscopy  A technique used for visualisation of anterior chamber angle.  Considered as the gold standard!  Fundamental part of comprehensive exam.  WHY  Obligatory for all glaucoma patient and suspected case.  Repeat periodically for patients with angle closure glaucoma  differentiation between angle closure and secondary glaucoma.  Help visualize the angle during the procedures such as laser trabeculoplasty and goniotomy  Divided into 2 types: →DIRECT  →INDIRECT Indication:  Primary open angle glaucoma and risk factors  Narrow anterior chamber angle – before pupillary dilation  Narrow angle glaucoma – evaluation of peripheral anterior synechiae (PAS)  Secondary open angle glaucoma and risk factors  Risk of angle neovascularisation  Risk of angle recession following trauma  Evaluation of risk for foreign intraocular body  Structural irregularities of the iris  Post laser peripheral iridotomy Contraindication  Hyphaema or mirohyphaema due to ocular trauma  Recent intraocular surgery  Lacerated or perforated globe Optical Principle  Total internal reflection within anterior chamber  Light rays from angle exceeds critical angle, so rays reflected back into AC, preventing direct visualisation of angle With gonio lens Gonioscopic view :  Direct Gonioscopy It is performed with a steep convex lens which permits light from the angle to exit the eye closer to the perpendicular at the lens – air interface. These lenses are used with a operating microscope. Direct gonioscopy is useful but fairly impractical for routine use. Koeppe Barkan Swan Jacob  LENS DESCRIPTION KOEPPE Prototype diagnostic lens RICHARDSON SHAFFER Small Koeppe lens used for Infants LAYDEN For gonioscopic examination of premature infants BARKAN Prototype surgical gonio lens THORPE Surgical & diagnostic lens for operating Rooms SWAN JACOB Surgical gonio lens used in children  Direct Gonioscopy Advantages Disadvantages ▪ Height of observer can be changed ▪ Suitable for sedated, Inconvenient comatose and children Special equipment ▪ Panoramic view required ▪ Less distortion Difficult to master ▪ Useful in examining Does not stabilize globe fundus with small pupil ▪ Straight view Light reflex from cornea ▪ Simultaneous Cannot perform observation of both indentation gonioscopy eyes are possible ▪ No coupling fluid is required Indirect Gonioscopy  Indirect gonioscopy uses mirrors or prism to over come the problem of total internal reflection.  Moreover , it uses the slit lamp’s illumination and magnification system to its advantage.  LENS DESCRIPTION GOLDMANN SINGLE MIRROR Mirror inclined at 62 degrees GOLDMANN THREE MIRROR One mirror for gonioscopy, two for retina; coated front surface for laser use ZEISS FOUR MIRROR All 4 mirrors inclined at 64 degrees for gonio;requires holder;fluid bridge not required. POSNER FOUR MIRROR Modified Zeiss four mirror gonioprism with attached handle SUSSMAN FOUR MIRROR Handheld Zeiss type Gonioprism THORPE FOUR MIRROR Four gonioscopy mirrors; inclined at 62 degrees;requires fluid bridge RITCH TRABECULOPLASTY Four gonioscopy mirrors; two inclined at LENS 59 degrees & two at 62 degrees with convex lens over two LATINA TRABECULOPLASTY One mirror for Trabeculoplasty LENS Goldmann 1 mirror Zeiss 4 mirror Goldmann 3 mirror  Indirect Gonioscopy Advantage ▪ Quick & convenient Disadvantage ▪ No special equipment Inadvertent pressure on required cornea ▪ Allows differentiation Mirror image is between appositional & confusing synechial closure Coupling fluid is ▪ Can create corneal required wedge Angle grading SCHEIE’S SHAFFER’S GRADING GRADING RP CENTRE Speath GONIOSCOPIC GONIOSCOPIC GRADING GRADING Shaffer’s grading Keep in your mind! ▪ Formed as a result of iris insertion into ciliary body ▪ Width depends on level of iris insertion ▪ Appear narrower in hyperopes and wider in myopes Ciliary body band ▪ Color: grey to dark brown ▪ Posterior sclera that is attached to the ciliary body posteriorly and corneo-scleral meshwork Scleral spur anteriorly ▪ Color : prominent white line  Trabecular meshwork  Pigmented band anterior to scleral spur  Although extent of TMW is from root of iris to schwalbe’s line it is considered as 2 portions a) Anterior - between schwalbe’s line and ant. Edge of schlem’s canal Involved in lesser degree of aqueous out flow b) Posterior – Functional part , primary site of aqueous out flow Appearance of funtional TMW depends on amount of pigment deposition Trabecular meshwork ▪ Not pigmented at birth but with aging changes from faint to dark brown ▪ Pigment deposition may be homogeneous or irregular ▪ When lightly pigmented blood reflex in Schlemm’s canal may be seen as a red band ▪ Termination of descement’s membrane ▪ It is marked only by a slight change in colour from trabecular meshwork or by a faint Schwalbe’s line white line. ▪ Important landmark in identifying the gonioscopic anatomy in confusing angle Remembering angle structures  An useful acronym I Can’t See This Stuff  Iris, Ciliary body band, Scleral spur, Trabecular meshwork, Schwalbe’s line 1.Check and sterile goniolens. Put gel adequetly. 2.Set up px correctly, epicanthus. 3.Set up your slit lamp esp. your hand rest which need to be stabilize to hold gonio lens. Make your own arm rest. DEMO 4.Find thumbnail and position it up. Now you act look inferior angle. Goldmann goniolens 3 mirror GG