Presented by:- Dr. Soumendra Datta 2nd yr PGT.

The Angle of Anterior Chamber bounded-

The Angle width -

Anteriorly by back of corneaPosteriorly by the anterior surface of iris

wide in myopicNarrow in hyper metropes

3. Trabecular meshwork- It is seen as band just anterior to the scleral spur. It‘s anterior non functional spur lies adjacent to the schwalbe line and has whitish color and posterior pigmented functional part lies adjacent to the scleral part and has greyish blue translucent appearance.

4. Schwalbe line- It is the most anterior structure appearing as opaque line. It demarcatas the peripheral termination of descemet membrane and anterior limit of the trabeculum.

Clinically the angle structure can be visualized by gonioscopic examination. Starting from

posterior to anterior, the angle recess is form by following structures:-

1.Cilliary Body- Formed by anterior most part of the Cilliary body between its attachment to the

scleral spur and insertion of iris. It is covered by the iris process in varying extent. It is wider in myopes. It

appear as grey or dark brown band.

2. Scleral spur- It is the posterior portion of the scleral sulcus and appear as prominent white line on

gonioscopy.

SL – Schwalbe LineTM- Trabecular MeshworkSS - Scleral SpurCBB – Ciliary Body Band

Blood vessels may normally be visible in the angle. If angle vessel that bridges the scleral spur is seen, it is probably abnormal.

Iris processes may be confused with peripheral anterior synechiae.

The canal is located directly anterior to the scleral spur and is normally not seen. However, during gonioscopy, blood may reflux in to the canal exposing its dimensions.

Excessive Trabecular pigment at the 12 o'clock position occurs in only 2.5% of individuals and is usually pathologic. This goniophotograph shows excessive Trabecular pigment representing pigmentary dispersion syndrome.

Torch Light Slit Lamp Gonio Lenses

Ultrasound Biomicroscopy Optical Coherence Tomograph Pentacam

Eclipse sign, which indicates decreased axial anterior chamber depth

(seen in angle closure glaucoma) can be elicited by shining a pen

light across the anterior chamber from temporal side and noting a

shadow on the nasal side.

Slit-lamp estimation of the limbal anterior chamber depth (LACD) by

the van Herick technique was developed as a non-contact approach

for estimating angle width. To perform this evaluation, the

illumination column of the slit lamp is offset from the central axis of

the microscope by 60º to the temporal side. A bright, narrow beam of

light is directed perpendicular to the ocular surface at the limbus.

LACD measurement is performed by comparing the depth of the

peripheral anterior chamber depth to the thickness of the cornea.

The original description outlined a four-point grading scheme of LACD—with LACD

graded as < 25%, >25% to 50%, or >100%

Curiously, this original scheme did not include a grade for the category 50--100%.

However, gonioscopic angle closure is seen rarely in persons with van Herick >50%

Foster proposed a modified scheme with increased precision of LACD measurement.

The original grade 1 was sub-divided into 0%, 5%, and 15% corneal thickness, and a

grade of 75% CT was added to compensate for the gap between the original grades 3 and

4.

The grade < 15% CT gave sensitivity and specificity at 84% and 86% for detection of

narrow angles Using a cutoff of < 25% specificity decreased to 65%, but sensitivity

increased to 99%.

1. Inter-observer reproducibility for the van Herick test may be high

2. It can only be performed if the limbus is clear, so eyes with pterygium or scarred temporal corneas cannot be graded.

Limbal anterior chamber depth of 15%

Corneal Slit bean

Anterior chamber

Iris Slit bean

Limbal anterior chamber depth

Corneal thickness

When peripheral anterior chamber depth is thought to be shallow (i.e. less than 1/4 th of corneal thickness by van Herick technique) , careful gonioscopic examination of angle is required

Gonioscopy is performed for several reasons:

To determine the mechanism of glaucoma (i.e., open or closed angle, pigment dispersion, plateau iris, etc.);

To identify persons at risk of developing angle closure glaucoma; and To monitor changes in the Anterior Chamber Angle over time as part of clinical care or

research.Principle of Gonioscopy:

The angle of the anterior chamber cannot be visualized directly through the intact cornea because light emitted from the angle undergoes total internal reflection at the anterior surface of the precorneal tear film.The critical angle for the cornea air interface is approximately 46 º.

In direct gonioscopy, the anterior curve of the contact lens- the goniolens-is such that the critical angle is not reached, and the light rays are reflected at the contact lens- air interface.

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

The Angle of Incidence of Light rays originating from angle structures is greater than the critical angle of the cornea-air interface (46 ) resulting in ̊�total internal reflection

Direct Gonioscope Indirect Gonioscope

Koeppe Direct Gonio lenses (Gonio Prism)

Goldmann Single Mirror Zeiss Four Mirror

Indirect Gonio Lenses (Gonio Mirrors)- used in conjunction with slit lamp

Direct Gonioscopy

Advantages Disadvantages

Patient comfort Second microscope andillumination

Possibly better view

Space needed

Nose can block temporal angle

Astigmatic distortion

Indirect Gonioscopy

Advantages Disadvantages

Uses the slit lamp Bubbles can block the view

Variable magnification

Plastic can scratch

No astigmatic aberrations

Need rotating head on slit lamp toget slit view nasally and temporally

System System Basis Angle Structures Classification

Scheie 1957 Extent of angle structures visualized

All structures seen Wide open open

Iris root not seen Grade I

Cilliary body band not seen

Grade II

posterior trabeculum obscured

Grade III

only Schwalbe's line visible

Grade IV closed

System System Basis Angle Structures Classification

Shaffer 1960 Angular width of the recess

Wide open (30 degrees to 45 degrees)

Grade 3–4, closure improbable

open

Moderately narrow (20 degrees)

Grade 2 closure possible

Extremely narrow (10 degrees)

Grade 1 closure probable

Partly or totally closed

Grade 0 closure present

closed

System System Basis Classification

Spaeth 1971 1. Insertion of iris root

2. Angular width of the recess

This system requires a combination of all three descriptors before deciding on classification.

3. Configuration of peripheral iris

1. In the management of patients with glaucoma, high resolution

ultrasound Biomicroscopy is helpful to define the anterior

chamber angle anatomy, when it cannot be seen

gonioscopically, as well as structure and relationships among

the iris, ciliary body, crystalline lens, intraocular lens and

anterior vitreous.

2. Frequencies of 20 to 50 MHz, which are used to image the

anterior segment, are referred to as high resolution ultrasound

Biomicroscopy

1.Anterior-segment optical coherence topography, or AS-

OCT, provides a noncontact, noninvasive means to image

the anterior chamber angle anatomy. The AS-OCT uses a

1310-nm wavelength, compared with the 820-nm

wavelength for posterior-segment imaging.

2. The AS-OCT has higher resolution, compared with high

resolution ultrasound Biomicroscopy, for imaging

structures in the iris and the angle anatomy.

Side-by-side comparison of optical coherence tomography image of the angle (left) and ultrasound Biomicroscopy image (right)

Basically it is 3-D rotating Scheimpflug camera. Pentacam is a diagnostic unit able to perform following five functions in 2 seconds:

Scheimpflug Image of Anterior Segment Three-dimensional anterior chamber analyzer Pachymetry Corneal topography Cataract analyzer

Principle of measurement

The Scheimpflug law says: To get a higher depth of focus, move the three planes, provided that the picture plane, the objective plane and the film plane has to cut each other in on line or one point of intersection.The Pentacam captures Scheimpflug images of the anterior segment through a rotating measurement

LIGHT--DARK CHANGESAngle appearance can change dramatically depending on the amount of illumination that strikesthe eye. When light shines on the eye the iris sphincter contracts and the peripheral iris movescentrally away from the angle. The result is in many cases a more open angle appearance.

Friedman reported that the fellow eyes of persons with unilateral acute attacks have more substantial angle narrowing in the dark than normal controls indicating that the dynamic response to external stimuli may play a role in the pathologic process.

UBM images of the same patient with the lights on (left) and the lights off (right image) showing marked angle narrowing in the dark.

CHANGES WITH CORNEAL INDENTATION

There is widening of the Anterior Chamber Angle with indentation according to

the report publish by Matsunaga and colleagues

PILOCARPINE EFFECTS ON Anterior Chamber Angle CONFIGURATION

The effect of pilocarpine on ACA configuration remains unclear, with some persons appearing to have shallower ACA after pilocarpine and others having greater angle opening. Hitchings demonstrated that when persons had a shallowing of the central anterior chamber depth in response to 4% Pilocarpine, the peripheral anterior chamber also shallowed, whereas if the central ACD did not shallow, the peripheral ACD widened.

Goldmann Applanation Tonometry

Tonometry is the objective measurement of IOP based on the force required to flattened the cornea or the degree of corneal indentation produce by a fixed force.

Goldmann Applanation Tonometry is based on the Imbert-Fick principle which states that pressure inside in ideal sphere is equal to the force necessary to flattened its surface divided by area of flattening.

The capillary attraction of tear meniscus and corneal rigidity cancel each other when the flattened area has a diameter of 3.06mm, as in Goldmann Applanation Tonometry.

Imbert-Fick’s principle Fluorescein-stained semicircles during Applanation

4. Tono-pen

3. Pascal Dynamic Contour Tonometer

2. Perkins Tonometer

1. Goldmann Tonometer

5. Schiotz Indentation Tonometer

6. Rebound Tonometer

These are based on the principle of Applanation but, instead of using a prism, the central part of the cornea is flattened by a jet of air.

1. Portable Air puff tonometer

2. Auto Non-Contact Tonometer

4. Portable Cordless Non-Contact Tonometer

3. Keeler’s hand-held Pulsair intelliPuff Tonometer

Clinical Condition Tonometer Preferred

Regular Cornea Goldmann Tonometer

Irregular Cornea Non-contact Air Puff Tonometer, Tono-pen

Eyes with Bandage contact lens Non-contact Air Puff Tonometer

Gas Filled eyes Tono-pen

Children under Anaesthesia Perkins, Tono-pen, Rebound Tonometer

Normal value – 11- 21mmHg

Diurnal Fluctuation in IOP – 24 hrs measurement of IOP at 3 to 4 hrs apart is more significant than single reading. Asymmetry in the IOP measurement between the two eyes of 5mmHg or more should arouse suspicion of glaucoma irrespective of single IOP reading and above 8mmHg is diagnostic of glaucoma.

According to the Chennai glaucoma study an 100µm increase in central corneal thickness is associated with 1.96mmHg increase in IOP in rural population and 2.45mmHg increase in IOP in urban population. Thus it is important to measure corneal thickness before instituting therapy in a patient with ocular hypertension.

Target pressure of 12mmHg is to be achieved after treatment in patients with glaucoma (According to advanced glaucoma intervention trial)

Relationship between prevalence of POAG and IOP

IOP (mmHg) POAG (%)

16-21 1.5

22-29 8.0

30 or more 25.0