Gonioscopy

1. Gonioscopy and methods to
assess anterior segments.IOP
and various methods of IOP
Measurements
BIPIN BISTA
2ND YEAR
RESIDENT-OPHTHALMOLOGY
NATIONAL MEDICAL COLLEGE
& TEACHING HOSPITAL

2. GONIOSCOPY
 HISTORICAL BACKGROUND
• In 1907, Trantas visualised the angle in an eye with keratoglobus by indenting the
limbus. Later termed gonioscopy.
• Salsmann later introduced goniolens in 1914
• 1919, a steeper lens was introduced by Koeppe
• Trancoso contributed by developing gonioscope for magnification and illumination
of the angle.
• Goldmann introduced gonioprism
• Barkan established the use of gonioscopy in the management of glaucoma

3. Principle of Gonioscopy
 In healthy eyes, angle cant be visualised d/t optical principle known as Critical
angle.
 Basically, when a light passes from a medium with greater to lesser refractive
index, (r) is larger (i) but when (R) is equals to 900 (i) is said to attain critical
angle. When (i) exceeds the critical angle, light is reflected back to first medium.
 Cornea-air interface is 460 thus light coming from anterior chamber angle exceeds
critical angle, thus the solution is to eliminate this interface by using a goniolens or
gonioprisms

4. Direct Gonioscopy
 Direct gonioscopy is performed with a
Koeppe Lens , a Dome-shaped 50D lens
requiring an optical coupling solution .
 Kept in patient’s cornea in supine position.
 Now a days its use has been reserved for
the operating room using an operating
microscope to examine children and
perform certain surgical procedures.

5. Indirect gonioscopy
 Use of goniolenses with built-in mirrors to facilitate visualisation of irido-corneal
angle. These lenses reflect light originating from the opposite side of the aqueous
humor.
 Zeiss lens and Goldmann lens .

6. Goldmann lenses
 It has three build-in mirrors each provide
different levels of magnifications.
 Curved surface is filled with coupling
solution and placed in anaesthesized
cornea.
 Ask to look upward and place the inferior rim
of the lens into the lower fornix.
 Then is asked to look forward, and is
evaluated with slit-lamp in narrowed beam
 Lens can be rotated to examine either clock
hours of the angle.

7. Zeiss lens
 Four mirror lens
1. Doesn’t require coupling solution.
2. Allows visualisation of all four quadrant.
3. Indentation gonioscopy can be performed.
 Initially the angle is assessed without indenting
and then by dynamic compression.
 Indentation is possible d/t smaller contact surface
of this lens in compare to corneal surface.
 Be careful in applying pressure : posterior
displacement of peripheral iris and widening of the
anterior chamber angle.

8. Gonioscopic Grading System
 Knowing the gonioscopic anatomy of the
angle :
• Identify the landmarks.
• Estimate the width of the angle between
peripheral iris and the cornea.
• Evaluate the insertion
• Contour of iris
• Degree of posterior TM pigmentation.

9. Shaffer System
 Described in terms of angular width in degrees of the anterior chamber angle.
 Estimated by making two lines , one from the point of insertion to Schwalbe’s line
and another from the iris surface of insertion.

10. SHAFFER ANGLE GRADING SYSTEM
GRADE NUMBER ANGLE WIDTH DESCRIPTION CLOSURE
4 45-35° Wide open Impossible
3 35-20 Wide open Impossible
2 20 Narrow Possible
1 < 10 Extremely narrow Probable
Slit Slit Narrowed to slit Probable
0 0 Closed Closed

11. SPAETH SYSTEM
 Provides more complete description of the anterior chamber angle.
 Level of iris insertion
 Geometric angle formed by the intersection of a line tangential to the trabecular
meshwork with surface of iris at Schwalbe’s line
 Peripheral iris contour
 Degree of depigmentation of TM.

12. SPEATH SYSTEM
Insertion of the iris
A: anterior to trabecular meshwork
B: behind Schwalbe’s line
C: posterior to scleral spur
D: deep into ciliary body face
E: extremely deep
Width of the angle
Ranges between 10° and 40°
Iris configuration
s: steep
r: regular
c: concave
Pigmentation of the posterior pigmented meshwork at the
12 o’clock position
Pigmentation is graded from 0 (no pigmentation) to 4 (heavy
pigmentation)

13. Van Herick’s Method
 Using Slit lamp alone to estimate the anterior chamber angle width.
 Thin beam of light is projected 600 plane to the eye from temporal field.
 Estimate corneal thickness to the peripheral part of the anterior chamber.

14. Van Herick’s Grading
Anterior chamber depth as
a proportion of corneal
thickness
Description Grade Comment
≥ 1
Peripheral anterior chamber
space equal to full corneal
thickness or larger
4 Wide open
¼ -1/2
Space between one-fourth
and one-half corneal
thickness
3 Incapable of closure
1/4
Space equal to one-fourth
corneal thickness
2 Should be gonioscoped
< 1/4
Space less than one-fourth
corneal thickness
1
Gonioscopy will usually
demonstrate a dangerously
narrowed angle

15. Occludable angles
 Based on the Spaeth classification an
iris with an insertion of either A or B or
an angle with a very steep approach
and angle widths measuring between
10° and 20° may benefit from a Yag
laser peripheral iridotomy. The
superior angle is the narrowest of the
four quadrants and the inferior angle is
usually the widest except in patients
with the pseudoexfoliation syndrome
where this rule does not apply due to
the presence of zonular laxity

16. Tonometry

17. What is Normal ?
 It may be defined as that pressure which does not lead to glaucomatous damage
of the optic nerve head.
 Unfortunately, such a definition can’t be expressed in precise numerical terms.

18. Role of IOP in Glaucoma
 Central role
 It is the only known modifiable factor that has been to show delay in progression
in both ocular hypertensive and glaucoma.

19. Setting up a target IOP
 Mild disease : RNFL with Normal Visual Field :20% reduction in IOP , Below 18
mmHg.
 Moderate : VF abnormalities in one hemifeild but not within 50 fixation : 30%
reduction , below 15 mmHg.
 Severe : field loss within 50 of fixation : 50% IOP reduction set IOP below 13
mmHg.

20. Factors affecting IOP
FACTORS ASSOCIATED WITH
ELEVATED IOP
WITH IOP REDUCTION
• Supine Position
• Valsalva maneuver
• Elevated episcleral venous pressure
• Sympathomimetics and anticholinergic
agents in narrow angles
• Ketamine and succinylcholine
• Caffeine
• Hyperthermia
• Blinking (10mm), Eyelid
squeezing(90mm), Upgaze,
Strabismus surgery.
• Prolonged exercise
• Pregnancy
• Metabolic acidosis
• Alcohol intake
• Marijuana
• General anaesthetics.

21. Tonometers and tonometry
 Two basic types of tonometers :
• Indentation
• Applanation

22. Indentation
 Schiötz tonometer was introduced in 1905
 Displaces a relatively large Intraocular
volume

23. Applanation tonometry
 Goldman applanation tonometry works on
Imbert-Fick priniciple. States that an
external force (W) against a sphere
equals the pressure in the sphere (pt )
multiplied by area flattened (applanated)
by the external force (A).
W=Pt × A

24. Technique
 Tip has built in bi-prism which is
transparent. Cornea is anaesthesized and
fluorescein is applied. Tonometer head is
applied to surface of the cornea and a
variable force is applied using a sensitive
spring using a dial.

25. Limitations
 Astigmatism greater than 3 diopters. Can be avoided by taking 2 measurements
900 apart – vertical and horizontal axes at rt. Angle.
 Careful in corneal abrasion and decompensation by anaesthesia.
 Potent source of infection : cleaned with hydrogen peroxide or with 70 % isopropyl
alcohol.
 Calibration of instrument should be done twice in a year.

26. Tono-Pen
 Small strain gauze with annular
applanation.
 Easy to use
 Portable
 Digital readout
 Used over bandaged contact lens, gas
filled eyes after vitrectomy.
 Disposable covers
 Costly

27. Non contact Tonometer (Airpuff)
 Applanation achieved by a column of air
 Sensor detects applanation.
 No anaesthesia or sterilisation is required.
 Not portable
 Requires maintenance

28. pneumotonometer
 Slightly convex tip, resting on a cushion of
air.
 Portable
 Position independent
 Used in irregular corneas and soft contact
lenses.
 Expensive
 Sanitation is difficult.

29. Rebound tonometry
 Measure IOP without anaesthesia.
 Measures IOP by a force produced by a
small plastic probe as it rebounds from
cornea.
 Comfortable among all and highly
reproducible
 Better applied in Paediatric cases.

30. Cycloscopy
 Direct visualisation of ciliary processes under special circumstances, such as
iridectomy, wide iris retraction, aniridia, aphakia.

31. High resolution ultrasound biomicroscopy
 Low frequency allows deeper penetration low resolution
 Echoes are produced from interfaces of fluids and tissues.
 Frequency of 20 to 50 MHz

32. Fluorophotometry
 Standard technique to know the rate of aqueous outflow post status drug
application as well .
 Instilling fluorescein drops in Anterior Chamber and the cornea and evaluating via
emission scans.

33. Tonography
 Means of estimating the outflow facility by raising the IOP with an electronic
indentation and observing the decay curve in the IOP over time, which is
continuously recorded on a paper strip.
 Inferred in Freidenwald Tables.

34. OCT of anterior segment
 AS-OCT uses 1310-nm wavelength , posterior – 820 nm
 Higher resolution

35. Measurement of episcleral venous
pressure
 Uses a thin membrane stretched over the tip of a hollow applanating head, filled
with water or air.
 Normal : 8 and 11 mmHg.
 Measured at a distal junction of aqueous and episcleral veins.

36. Pachymetry
 Assessment of Central corneal thickness
 Easy, portable and widely used.
 Influences types of tonometry to be used
 Shows prognostic value for patients with ocular hypertensives.

37. Reference:
1.Glaucoma – Shield Textbook of Glaucoma 6th edition
2.Curbside Consultation in Glaucoma : Steven J. Gedde
3.Myron yanoff and jay s duker4th edition
THANK YOU