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Gonioscopy
- 1. GONIOSCOPY P U SH K A L K ATA R A
- 2. INTRODUCTION • Method ofevaluating the anterior chamber angle • Used therapeutically for procedures such as laser trabeculoplasty & goniotomy • Term coined by Trantas in 1907, • He visualized the angle in an eye with keratoglobus by indenting the limbus • Goldmann in 1938, introduced the gonioprism • Barkan, established use of gonioscopy in management of glaucoma
- 3. OPTIC PRINCIPLES • Angleof AC cannot be visualized directly through intact cornea • Light from angle structures undergo ‘Total Internal Reflection’ at anterior surface of precorneal tear film
- 4. • When lighttravels from a medium of higher to one of lower refractive index, it will be reflected at the interface • Unless the angle of incidence is less than a certain ‘critical angle’ dependent on their refractive index difference (46º for tear film-air interface) • Goniolenses eliminates total internal reflection by replacing tear film-air interface with a tear film-goniolens interface
- 5. TYPES • Direct Goniolens –Provides direct view of the angle – Eg: Koeppe, Swan-Jacob • Indirect Goniolens – Provides mirror image of opposite angle – Eg: Goldmann, Zeiss
- 6. GENERAL PROCEDURE • Ambientillumination low-completely dark • Size & intensity of slit beam to absolute minimum • Patient seated at slit lam & advised that lens will touch the eye • Both eyes should remain open • Drop of local anaesthetic instilled • Coupling fluid (eg: hypermellose 0.3%) placed on contact surface of lens • Patient is asked to look upwards & lens is inserted rapidly to avoid loss of coupling fluid • Afterwards, lens should be cleaned & sterilized
- 7. DIRECT GONIOSCOPY • Workby constructing the viewing surface of lens in a domed or slanted configuration • Such that exiting light rays strike the contact lens-air interface at a steeper than critical angle, so they pass through the observer • Patient should be supine • Useful but impractical for routine use
- 8. TYPES OF DIRECTGONIOLENS 1. Koeppe 2. Richardson-Shaffer 3. Huskins Barkan 4. Sieback 5. Swan Jacob 6. Layden 7. Worth
- 9. KOEPPE GONIOLENS • Mostcommonly used for diagnostic direct gonioscopy • Used with handheld microscope with separate light source • Provides a panaromic view of the angle
- 10. • Richardson-Shaffers- smallKoeppe lens used for infants • Huskins-Barkan- prototype surgical goniolens used for goniotomy • Swan-Jacob- also for surgical purpose • Worth- anchors to cornea by partial vacuum • Sieback- tiny goniolens which floats on cornea • Layden- evaluating neonatal angle
- 11. ADVANTAGES & DISADVANTAGES •Greater flexibility • Panaromic view • Angle becomes deep in supine position, easy to see • Detailed examination of minor structures possible • Lesser distortion of anterior chamber • Can be used in sedated or anaesthetized patients • Straight view • Both eyes can be examined simultaneously • Inconvenient • Light reflexes from cornea • Time consuming • Benefits of slit lamp not available
- 12. INDIRECT GONIOSCOPY • Providesmirror image of opposite angle • Can be used only with a slit lamp • Uses mirrors/prisms to overcome total internal reflection • Two types : – Non-Indentation • Eg: Goldmann, Magna, Ritch – Indentation • Eg: Zeiss, Posner, Sussman
- 13. NON-INDENTATION GONIOSCOPY • ClassicGoldmann lens has three mirrors • Coupling agent is required • Excess pressure narrows angle appearance
- 14. NON-INDENTATION GONIOSCOPY ADVANTAGES • Easyto use • Excellent view • Stabilizes the globe (can be used in laser trabeculoplasty) • Peripheral retina can be seen DISADVANTAGES • Curvature of lens is more than cornea, coupling agent required • Blurs vision & fundus • Needs to be rotated 360º
- 15. INDENTATION GONIOSCOPY • IncludeZeiss, Posner, Sussman, all are 4-mirror gonioprisms • No need for a coupling agent • Examiner observes the effect on angle width
- 16. ZEISS GONIOPRISM • 4identical mirrors angled at 64 • allows examination of four quadrants without rotation
- 17. • Posner- sameas zeiss but made of plastic than glass • Sussman- No handle
- 18. INDENTATION GONIOSCOPY ADVANTAGES • Easyto perform when mastered • All four quadrants seen • Allows differentiation of appositional & synaechial angle closure • No coupling agent DISADVANTAGES • Difficult to master • Mirror image can be confusing • May open the angle artificially
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- 20. SCHWALBE’S LINE • Mostanterior structure • Appears whitish to variably pigmented • Demarcates peripheral termination of Descemets membrane • Best identified by locating corneal wedge • Sampaolesi line – pigment deposits at or anterior to schwalbes line – Eg: Pseudoexfoliation syndrome, Pigment Dispersion Syndrome
- 22. TRABECULAR MESHWORK • Liesb/w schwalbes line & scleral spur • Avg width 600um • Smooth in infants • Coarse & pigmented with age • Anterior part non-functional • Posterior pigmented functional part has greyish blue translucent appearance
- 23. SCLERAL SPUR • Anteriormost projection of sclera • Appears as a narrow, dense, shiny, whitish band • Yellows with age
- 24. CILIARY BODY BAND •Just behind the scleral spur as pink to dull brown or grey band • Portion of ciliary body which is visible in the angle as a result of insertion of iris into ciliary body
- 25. ROOT OF IRIS •Iris contour is slightly convex or flat • Radial marking & crypts are present • IRIS PROCESSES- Normal Variants – Appear as fine strands extending from iris to scleral spur
- 26. GRADING OF ANGLEWIDTH 1. Shaffer System 2. Scheie Classification 3. Spaeth System 4. Van-Herick Method
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- 28. VAN-HERIK METHOD • Usesthe slit lamp alone to estimate the AC angle
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- 38. BLOOD IN SCHLEMMSCANAL