Gonioscopy

GONIOSCOPY

Sanket Parajuli

Introduction • Greek : gṓ nḗ : angle , Ộs’k-pḗ : view

• Gonioscopy - examination of eye to look at the angle of anterior chamber from anterior part of iris to the posterior part of cornea using gonio-lens and slit lamp.

• Alexois Trantas:(1907) First visualized angle in an eye with

Keratoglobus

• Maximilian Salsmann:(1914) Father of Gonioscopy. First introduced Goniolens

HISTORY

• Koeppe :

Designed improved Contact lens and gave the method biomicroscopy of angle of anterior Chamber with slit lamp.

• Manuel Uribe Troncoso:

Developed Gonioscope for magnification & illumination of Angle. First to write a Comprehensive book on Gonioscopy

• Otto Barkan: Established use of Gonioscopy

in Management of Glaucoma.

• Goldmann:(1938) Introduced Gonioprism.

Purpose

• Biomicroscopic view of iridocorneal angle

• Vital for both classification of glaucoma and management

• Done initially in all glaucoma patients and suspects

Principle of gonioscopy

• When light passes from a medium with a greater index of refraction to one with a lesser index, the angle of refraction (r) is larger than the angle of incidence (i).

• When r equals 90 degrees, i is said to have attained the critical angle.

• When i exceeds the critical angle, the light is reflected back into the first medium.

• The critical angle for the cornea-air interface is approximately 46 degrees.

• Light rays coming from the anterior chamber angle exceed this critical angle and are therefore reflected back into the anterior chamber, preventing visualization of the angle

• The solution is to eliminate the cornea (optically).

• Because the index of refraction of a contact lens approaches that of the cornea, there is minimal refraction at the interface of these two media, which eliminates the optical effect of the front corneal surface. Therefore, light rays from the anterior chamber angle enter the contact lens and are then made to pass through the new contact lens & air interface by one of two basic designs.

• In direct gonioscopy, the anterior curve of the contact lens (goniolens) is such that the critical angle is not reached, and the light rays are refracted at the contact lens & “air interface.

• In indirect gonioscopy, the light rays are reflected by a mirror in the contact lens (gonioprism) and leave the lens at nearly a right angle to the contact lens & “air interface

(a) The normal eye: light from iridocorneal angle is reflected back into eye and thus cannot be seen

(b) The direct goniolens: As the index of refraction of lens is similar to that of cornea, light enters lens and is then refracted by lens to enable observer to view angle

(c) The indirect goniolens: principle similar to direct lens but, once light has entered lens, it is reflected by a mirror.

Common Goniolens and Types

Lens Description

1. Indirect goniolens

• Goldmann single mirror • Goldmann 3 mirror

Mirror inclined at 62⁰Mirror inclined at 59⁰

• Zeiss four mirror All mirrors at 64 , no fluid bridge requried⁰

• Posner four mirror Modified zeiss with handel

• Sussman four mirror Hand held zeiss model

• Ritch trabeculoplasty lens Four mirror’s : 2 at 59 and 2 at 62 , with a ⁰ ⁰convex lens over two of the mirror’s

2. Direct goniolens

• Koeppe Dome shaped lens

• Barkan Quarter sphere, surgical and diagnostic lens

• Swan-jacob Surgical goniolens for children

Direct GonioscopyInstruments : goniolens , gonioscope or hand bio-microscope (10 -20x) and a light source

• Constructs a view of surface of lens in a domed or slanted configuration

• Exiting light rays strike contact lens/air interface at a steeper than critical angle

• Light then pass through to the observer

• Light rays from angle are viewed directly, without reflection inside lens

• Slit-lamp: not required • Patient position: supine

Direct type Goniolensesa. Diagnostic lenses: Koeppe (several sizes)b. Surgical lenses : used for angle surgery– Barkan– Swan-Jacob.

Indirect Gonioscopy• Instrument's : Gonioprism and a slitlamp• Most widely used gonioprism : Goldmann

– Goldman single mirror• Height of the mirror : 12 mm• Angle of the mirror : 62 ⁰• Central well diameter : 12mm• Posterior radius of curvature : 7.38 mm

– Goldmann three mirror• One mirror for examination of anterior

chamber : 59⁰• Two mirror’s for examination of fundus.

• The posterior radius of curvature is such that both the lens need viscous material to fill the space

Four mirror lens

Zeiss four mirror lens• All mirrors at an angle of 64⁰ • eliminating need for rotating • Original four mirror - Unger Holder Posner - fixed holder Sussman - held directly

• Posterior curvature of all these lens is equal to that of cornea which allows the patient’s own tears to form the fluid bridge

Posner four-mirror lens

Sussman four - mirror lens

GONIOLENS USED IN INDIRECT GONIOSCOPY

A) 4 MIRROR

B) 3 MIRROR

C) 2 & 1 MIRROR

Goldmann two mirror gonioprism

• Both the mirrors are inclined at 62°• It need to be rotated once to examine the whole angle.• Laser trabeculoplasty

4 mirror lens

• Allow quick examination of all 4 quadrants without any need for rotation of the goniolens

• Eg Zeis, Posner, Sussman. They are non suction type

3 mirror lens• D or apical mirror : angle examination• Other two : peripheral retina• Central /equatorial lens : macular examination• D shaped mirror should be first placed at 12o’ clock position

and eventually rotated thrice to view the other 3 quadrants

• eg. Goldmann

2 & 1 mirror lens• used in patients with small interpalpebral fissures• 2 mirror lens need to be rotated once for viewing all quadrants• 1 mirror needs to be manipulated like the 3 mirror lens.

• All 4 mirrors inclined at 64 degrees for gonio

ZEISS FOUR MIRROR

• Handheld

SUSSMAN FOUR MIRROR

• Four gonioscopy mirrors; inclined at 62 degrees; requires fluid bridge

THORPE FOUR MIRROR

Four mirror lens

• Zeiss four mirror lens, all at an angle of 64⁰ eliminating the need for rotating

• Original four mirror is on a Holder• Posner has a fixed holder• Sussman can be held directly• Posterior curvature of all these lens is equal to that of cornea

which allows the patient’s own tears to form the fluid bridge

DIRECT

ADVANTAGE DISADVANTAGE

• Observer’s height can be changed

• Done on sedated, comatosed & Children

• Panoramic view of Angle• Less distortion of AC• Useful in examining fundus

with small pupil

• Inconvenient• Special equipments required• Difficult to master

INDIRECT

ADVANTAGE DISADVANTAGE

• Most commonly performed• Quick & Convenient• No special equipment

required• Allows differentiation

between Appositional & Synechial closure

• Can create corneal wedge

• Inadvertent Pressure on Cornea

• Mirror image is confusing• Exaggerates the degree of

angle narrowing in Goldmann lens

• Opens the angle in four mirror lenses

DIRECT V/S INDIRECT

Features DIRECT Indirect

View Panoramic view of iridocorneal angle with ability to adjust view by examiner.

Segmental

Eyes Both eyes can be examined simultaneously

One Eye at a time

Coupling (viscous) material

Not required required

Image Direct view as for surgery Mirror image seen

Indentation Can not be done Can be done

INDIRECT GONIOCOPY: SLIT LAMP TECHNIQUE

GENERAL GUIDELINES:• Explain the procedure to the patient• Reassure the patient & ensure cooperation• Do an external examination first to rule out corneal abrasion,

infection, edema• Perform tonometry before gonioscopy• Use anaesthesia (4% lignocaine)• Pay attention to patient comfort• Pay attention to alignment by adequately supporting forearm (using

an elbow rest)• Perform examination in dark room• Examiner should use right hand to evaluate left eye & vice versa• Disinfect lens prior & after every use• Use suitable gonio lens. 3 mirror (suction type ) are best for starters

SLIT LAMP SETTINGS

• 10-25X magnification is used• Fairly short and narrow beam• Viewing & illumination arm in same axis. illumination arm may be

moved paraxially to view the temporal & nasal recess• Focus light on the D shaped mirror• Avoid throwing light into the pupils• Magnification & illumination may be increased to view finer details

like blood vessels and foreign bodies

• NOTE: Images are reversed but never crossed!!

Recording findings

• Simple descriptive words are more helpful than using numerical .

• Three features : post most structure pigmentation iris pattern• Any abnormalities should be noted

• Wash with soap & water• Soaking the lens for 5-10 min in fresh solution of Sod.

Hypochlorite [ 1:10 household bleach : water]• Rinsing with sterile water• Air drying• 3% H2O2 or 1% Formaldehyde can also be used.• Direct surgical gonioscopes [ Koeppe, Swan Jacob] can be

sterilized with ethylene oxide.

Sterilization and disinfection

• Contact investigation patient discomfort.• Conjunctival infection.• Slit lamp illumination-> pupil constriction-> opens up the

angle• Wide inter observer variations.• Indentation corneal folds, distorted view of angle structures,

epithelial injury.

Limitations

• Painful inflamed eye

• Acute glaucoma with edematous cornea

• Mydriatic drugs- obscure angle by bunching up iris

• Suspected open globe injury

Contraindication

Normal Angle Structures

• visible in the AC as a result of iris insertion into ciliary body

• Width depends on level of iris insertion

• Myopes :Wider• Hyperopia : narrow• Color: grey to dark brown

Ciliary Body Band (CBB)

Ciliary Body Band

Wide CBB Wide CBB Narrow or absent CBB

Physiological Pathological hypermetropia

Myopia Angle recession (blunt trauma)

Anterior insertion of iris

Aphakia cyclodialysis

• This is the posterior Lip of scleral sulcus

• Attached to – ciliary body- posteriorly– corneo-scleral meshwork anteriorly

• Color : prominent white line

Scleral spur

• Pigmented band anterior to scleral spur• Although extent of TM 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 schlemm’s cannal• Involved in lesser degree of aqueous out flow

b) Posterior – Functional part , primary site of aqueous out flow• Appearance of functional TM depends on amount of pigment

deposition

Trabecular Meshwork (TM)

• At birth no pigment • With age: faint to dark brown

• Pigment deposition : homogeneous or irregular

• When lightly pigmented blood reflex in schlemm’s cannal may be seen as a red band

Trabecular Meshwork

• When a thin slit of light hits the irido-corneal angle at an angle of 10 -15⁰ ⁰

• Two light reflections are seen – External corneal surfaces– internal corneal surfaces

• useful technique to identify the trabecular meshwor– Nonpigmented– Excessively pigmented

Corneal Wedge

Schwalbe’s Line

• Junction between anterior chamber angle structures and cornea where the descement’s membrane terminates

• Fine ridge anterior to TM• Identified by a small built up

of pigment • Landmark for TM in narrow

angle

Sampaolesi’s line

• Schwalbe’s line, the termination of Descemet’smembrane and the most anterior structure of theiridocorneal angle may have pigment scatteredaround and on it (in pseudoexfoliation syndromethis is termed Sampaolesi’s line), particularly inferiorlyat 6 o’clock (mirror at 12 o’clock).

Contour

• Flat- Deep AC• Concave- Shallow AC , Hyperopia• Convex- High Myopia, Pigment Dispersion Syndrome• Abnormal Rolling- Plateau iris

Iris

IRIS PROCESS PAS• Fine• Extend into scleral Spur• Follow concavity of Recess• Underlying Structures are seen• Iris moves with indentation• Broken with angle Recession

• Broad• Extend Beyond Scleral Spur• Bridge concavity of Recess• Obscures the View• Resists Movement• Intact in Recession

ANGLE BLOOD VESSELS

NORMAL NEOVASCULARIZATION

• Radial Orientation• Thick• Non Branching• Do not cross Scleral Spur

• Fine• Arborising• Crosses Scleral Spur

Manupulative Gonioscopy

• Over the Hill• Indentation

• Special maneuver to view over a steep iris

• Done by asking patient to look in direction of mirror or by moving mirror towards angle being viewed

Over The Hill/Dive Bomber’s View

Indentation Gonioscopy

• When iris covers the trabecular meshwork (TM) its easy to mistake:– Non-pigmented TM for scleral spur– Pigmented Schwalbe’s line for TM– Apposition for synechiae

• Indentation Gonioscopy is particularly useful in these cases

• Useful when iris surface is convex– Done when recognition of angle

structures is difficult• Performed in all glaucoma cases– Differentiates appositional vs

synechial closure in pupillary block– Measures extent of angle closure– Identifies plateau iris configuration– Identifies lens induced angle

closure

Plateau iris

S - shaped configuration of iris

• When posterior (pigmented) part of trabecular meshwork is not visible in more than 180 degrees of angle without indentation or manipulation

Occludable Angle

1. Scheie system: most posterior structure visible

2. Shaffer’s system : assess geometric angle width in 4 grades angle potential for occlusion

3. Spaeth system : three dimentional structure of angle - level of iris insertion and peripheral iris configuration.

Grading

GRADE STRUCTURE SEEN PROBABILITY0 CBB Seen No angle closure

I CBB Narrow No angle closure

II CBB not seen, SS Seen Rarely closure possible

III Posterior TM Not seen Closure likely

IV Schwalbe’s Line not seen Gonioscopicaly closed

Scheie System

SHAFFER’S SYSTEMModified Shaffer

Ciliary band visible

Scleral spur visible

Anterior TM visible

Schwalbe’s line visible

Schwalbe’s line not visible

• Level of Iris Insertion• Angular width• Iris configuration• Pigmentation of posterior Trabecular Meshwork

Spaeth System

Spaeth Systemstep 1: site of iris insertion The first grading decision assesses the site of the iris insertion, both as it appears functionally (without pressure on the cornea) and as it actually inserts anatomically (after indentation).A - Anterior to trabecular meshwork (i.e., Schwalbe’s line) B - Behind Schwalbe’s line (i.e., at level of trabecular meshwork) C - Centered at the level of the scleral spur D -Deep to the scleral spur (i.e., anterior ciliary body) E - Extremely deep in the ciliary body.

step 2: Angle width • As with the Shaffer system,

the geometric angle is estimated at the perceived intersection of the imaginary tangents formed by the peripheral third of the iris and the inner wall of the corneo-scleral junction.

• Though some examiners prefer increments of 10°, as with the Shaffer system, and others use increments of 15°

• Step 3: configuration of peripheral iris

The newer system describes four iris configurations, indicated by the first letter of their description• B - ‘bows 1 to 4 plus’ (usually indicative

of optically-appearing closure, altering with indentation)

• P -‘plateau’ • F - ‘f lat approach’: the commonest iris

appearance • C - ‘concave’ as in posteriorly bowed iris

Step 4: trabecular meshwork pigmentation

• minimal or no pigment is graded 1• dense pigment deposition is indicated as grade 4 • 2-3 inbetween

Example::• E40c, 4 + TMP

• An extremely deeply inserting iris root, in a 40° angle recess, with posterior bowing of the peripheral iris and extensive TM pigmentation (as might be seen in a myopic eye with pigment dispersion syndrome).

Angle Anomalies

POSSIBLE AFFECTS OF TRAUMA ON ANGLE

• ANGLE RECESSION – characterised by widely visible CBB due to tear between longitudinal and circular ciliary muscle fibres

• Cyclodialysis –disinsertion of ciliary body band from scleral spur, characterised by deep angle & decreased iop ; shows a white band on gonioscopy

• Intraocular foreign body lodged in the angle

• Lodged blood clots

SPECIFIC ANGLE CHARACTERISTICS

• FUCH’S HETEROCHROMATIC IRIDOCYCLITIS: fine fragile vessels

• PSEUDOEXFOLIATION SYNDROME: sampaolesi’s line & heavily pigmented trabecular meshwork

• PIGMENT DISPERSION SYNDROME: abnormal posterior bowing of iris

• PLATEU IRIS: flat configuration iris with peripheral hump mimicking narrow angle

• RAISED EPISCLERAL VENOUS PRESSURE :uniform linear reddish hue (blood in schlemm’s canal)

FOREIGN BODY IN ANGLE

• Hyphaema • Iridodialysis

• Angle recession (arrows) following blunt ocular trauma

• Neovascularization of an angle (arrows).

• Iris melanoma • Iris nevus

References 1. Textbook of Glaucoma – M. Bruce Shield 5th edition2. Diagnosis and Therapy of Glaucoma - Becker – Shaffer’s 8th

edition3. Ophthalmology – Yanoff and Duker 3rd edition4. Clinical Ophthalmology - Jack J Kanski 7th edition

Posterior Embryotoxon