Nuggets in clinical approach to diagnosis of glaucoma

Abstract

Having a high index of suspicion and comprehensive examination are key to success in early diagnosis of glaucoma. The diagnosis of glaucoma is many a time straight forward in mid or late stages, but becomes elusive in early stages. Once a diagnosis of glaucoma is made then the patient is to be treated ether by medical line of treatment or with surgical intervention or with lasers and the follow-up remains to be life-long. So, one has to be very astute in making a diagnosis of glaucoma. Glaucoma not only affects the quality of vision, but also the quality-of-life. We all know the glaucoma is an irreversible blindness so early diagnosis is of prime importance. Opportunistic screening at our clinics with comprehensive eye examination is very important. This article deals with importance history taking and diagnostics in case of glaucoma. Perfecting our basics makes our life easier for further management.

Full text

Journal of Clinical Ophthalmology and Research - Sep-Dec 2013 - Volume 1 - Issue 3 175
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DOI:
10.4103/2320-3897.116865
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Department of Ophthalmology, Amina Hospital and ESIS Hospital,
Solapur, Maharashtra, India
Address for correspondence: Dr. Sayyed Mazhar, 158-A Railway Lines,
Parijat Complex, Solapur, Maharashtra, India. E-mail: drsmazhar@
gmail.com
Manuscript received: 12.02.2013; Revision accepted: 06.06.2013
Glaucoma is defined as chronic progressive optic neuropathy that
has common characteristic morphological changes at the optic nerve
head (ONH) and retinal nerve fiber layer (RNFL) in the absence of
other ocular disease and congenital anomalies. Progressive retinal
ganglion cell death and visual field (VF) losses are associated with
these changes. Intraocular pressure (IOP) is a definite risk factor.
Among the emerging causes of blindness glaucoma needs a special
attention. Prevalence of glaucoma is 4% in the population aged
above 30 years. In children, it is estimated to be 3%; hence, we should
sharpen our clinical skills for diagnosing and managing glaucoma.
The diagnosis of glaucoma is based on structural and
functional changes in the ONH. History, IOP, gonioscopy, central
corneal thickness (CCT) and newer diagnostic modalities are
complimentary to the diagnosis.
History
In any illness history, taking is a prospective aspect in making a
diagnosis, but in glaucoma it is a retrospective history, which plays
a major role in management of the case. Here is small acronym
for history taking.
A= Asthma, Arthritis, Allergy, Attacks in the past
In asthma non-selective beta blockers are to be avoided and
selective beta blockers are to be given with care.[1,2] Salbutamol can
precipitate an attack of angle closure (AC). Arthritis and allergies
are many times treated with the long-term use of steroids. Steroids
through any root of administration can cause an increase in IOP in
steroid responders. Allergy to sulphate has to be checked before
using carbonic anhydrase inhibitors (CAI). History of attacks in
the past suggesting the increase in IOP is very important when
we are dealing with a case of narrow angles.
B= Blood pressure, Breathlessness, Blood loss, Blow to the eye
In patients using systemic beta blockers, topical administration
of beta blockers may be less effective.[3] So also systemic beta
blockers are to be avoided at night times to prevent further dip of
IOP. Breathlessness may be a sign of cardio pulmonary problems so
care is to be advocated while administering mannitol and topical
beta blockers.[4] Blood loss either due to major surgery or accident
causing severer hypovolemia may show changes in ONH, which
mimic normal tension glaucoma (NTG). Blow to the eye (trauma)
can direct us to see angle recession and other correlated subtle
changes. No matter what the duration of trauma was or how
trivial it was.
C = Cardio vascular system (CVS): Blocks, arrhythmias, cardiac
failure, Central nervous system: Migraine, head injury
,
convulsions, depression, Calculus: Urinary.
Beta blockers adverse effects with CVS have already been
mentioned. Migraine history is important, especially in cases
of NTG. Head injury may cause optic disc pallor and one has to
carefully look for VFs for neurological defects. Convulsions and
depressions are important because of the type of drug being
taken, which is discussed later. Calculus-CAIs when used for a
long-term can precipitate renal calculus because higher urine
calcium levels.
D = Diabetes, Drugs-systemic/topical/local/inhalators.
Although Baltimore I study did not find any association of
diabetes with open angle glaucoma (OAG), but recent population
studies support an association with diabetes.[5] Drugs-use of
any current medications needs to be considered along with
certain specific past medications, including. Steroids-any route
of administration is associated with ocular hypertension (OHT)
and OAG, sometimes found in traditional medicines. Glaucoma
eye drops (prolonged use may increase the likelihood of
trabeculectomy failure) Anticholinergics/tricyclic antidepressants
can cause AC Anticonvulsants: Topiramate can cause acute
AC. Vigabatrin linked to nasal peripheral VF loss without disc
changes. Systemic beta-blockers/calcium channel blockers-
may interact with topical beta blockers. Alpha agonists are
contraindicated for patients taking monoamine oxidase inhibitors
Commissioned Article
Nuggets in clinical approach to diagnosis of glaucoma
Sayyed Mazhar
Having a high index of suspicion and comprehensive examination are key to success in early diagnosis of glaucoma.
The diagnosis of glaucoma is many a time straight forward in mid or late stages, but becomes elusive in early stages.
Once a diagnosis of glaucoma is made then the patient is to be treated ether by medical line of treatment or with
surgical intervention or with lasers and the follow-up remains to be life-long. So, one has to be very astute in making
a diagnosis of glaucoma. Glaucoma not only affects the quality of vision, but also the quality-of-life. We all know
the glaucoma is an irreversible blindness so early diagnosis is of prime importance. Opportunistic screening at our
clinics with comprehensive eye examination is very important. This article deals with importance history taking and
diagnostics in case of glaucoma. Perfecting our basics makes our life easier for further management.
Key words: Gonioscopy, history, perimetry
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Mazhar: Nuggets in glaucoma
(prescribed for depression, migraine prophylaxis, or Parkinson’s
disease) and in infants and children check for sulphur allergy
prior to using CIAs.
E = Endocrine (thyroid), Error of refraction, Economic status.
A more recent study confirmed the association of graves
diseases with primary open angle glaucoma (POAG) and NTG.[6]
Patient can be hypothyroid, euthyroid or hyperthyroid when the
eye problem begins. Other pituitary problems can be associated
with anomalies of angle or the lens. Refractory errors around
± 6D are not much significant, but high myopes are thought as
a risk factor for POAG and high hypermetropes are risk factors
for primary angle closure glaucoma (PACG). Economic status of
patients helps us to prescribe a drug according to the patient
life-style and needs and hence increasing compliance in glaucoma
management.
F = Family history of glaucoma, Family status.
Risk of developing POAG in the first degree relatives is 4-16%.
Rotterdam found the risk to be as high as 10 times.[7] Family status
regarding female patient a history of amenorrhea and lactation are
of prime importance as drugs can act on the fetus or the new born.
Slit Lamp Examination
Before we put our hands on to specific diagnostic tools of glaucoma,
a basic slit lamp examination is a must. Attention must be paid
to the following areas. Cornea and anterior chamber for central
and peripheral anterior chamber depth (Von-Herick test) presence
of keratic precipitates, haab’s striae and corneal dimensions. Iris
should be seen for reactions, which is slowly reacted after and
acute, attack. Other abnormalities in the iris to be look for are
rubeosis iridis, patchy atrophy, synechiae, ectropion of uveal
pigment, pseudoexfoliative material, transillumination defects,
iris nodules and displaced pupil with iris atrophy. Examination of
lens also reveals certain diagnostic clues such as pseudoexfoliation,
glaucoma fleckens, phacodonesis or abnormal lens shape.
Tonometry
Type-tonometers can be classified as:
a. Direct or indirect
b. Low displacement tonometer or high displacement tonometer
c. Contact and non-contact tonometer
d. Indentation tonometer or applanation tonometer
e. Dynamic contour matching tonometer.
Goldmann applanation tonometry (1954) until today is
considered as the gold standard.
Whom: Every OPD patient above the age of 40 years.
When: Every visit. If diurnal variation is required then at 8
am, 11 am, 2 pm, 6 pm.
Astigmatism: When above 3D turn the prism head to 90° and
take the average of horizontal and vertical meridians OR rotate
prism head at 45° corresponding to least curved meridian.[8]
Procedure: Performed under topical anesthesia, fluorescein
staining, blue light, set knob at 1 g, turn the knob until inner
borders of Fl rings touch each other at the midpoint of their
pulsations. Take the average of three readings. Calibration of
tonometer should be checked frequently [Figure 1].
Sterilizations: I wipe it with sterlium and then with normal
saline swab. Calibration-should be done monthly. The calibration
rod should be tested at (0, 20, 60) mm of Hg potential errors-
thin cornea, thick cornea, astigmatism more (>) three diopters,
inadequate fluorescein, too much fluorescein, irregular cornea,
tonometer out of calibration, elevating the eyes >15°, repeated
tonometry, pressing on the eyelids or globe, squeezing of the
eyelids, observer bias (expectations and even numbers).
Tips: After taking IOP turn over to normal light to examine if
prism head had made any damage to the cornea.
Gonioscopy should not be followed by tonometry, but it should
be vice versa.
CCT [9,10]
Goldmann tonometer is calibrated for average corneal thickness of
520 microns. Excessive thick or thin corneas either over estimate
or under estimate IOPs Normal CCT is 520 microns (Indians)
Correction factor is 2.5 mm of Hg for every 50 microns. Increase
or decrease target IOP by one standard deviation (SD) for every 1
SD of CCT. 1 SD of IOP = 3 mm of Hg 1 SD of CCT = 30 microns.
Whom: Ideally for all glaucoma patients on making a diagnosis
more important for OHT/NTG and resetting of target IOP when -
ideally ½ h after awakening.
Frequency: Once in 5 years.
Why: It is risk factor for progression. Thin corneas are a risk
factor for progression especially in case of raised IOP.
How: Ultrasonic pachymetry is gold standard.
Expression: Thin - <500 microns/average - 500-600 microns/
thick - >600 microns.[11]
Gonioscopy
It is biomicroscopic examination of the anterior chamber
angle of the eye.
Principal: The gonio lens eliminates the total internal reflection
Figure 1: Caliberation of applanation tonometer. Current glaucoma
practice from glaucoma society of india year 2002
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Mazhar: Nuggets in glaucoma
of the cornea by exceeding the critical angle of 46°.
When: Initially for all patients. Repeat more frequently for
patient with AC.
Which lens: To start learning single mirror after learning curve
shift to four mirrors [Table 1].
Indications [12]
Diagnostics
1. To study topography of the anterior chamber angle [Figure 2]
2. To assess degree of opening of anterior chamber angle recess
3. To assess risk of closure on dilatation of pupil
4. Visualization of congenital anomalies
5. Classification of glaucoma (primary/secondary)
6. To note the presence and extent of angle neovascularization
7. Assessment of abnormal angle pigmentation
8. Visualization of pseudoexfoliative material in the angle
9. To look for post-traumatic angle recession, cyclodialysis
10. Rule out foreign body in the angle after open globe injury
11. Neoplastic invasion into angle structures (ciliary body tumor)
12. Diagnosis of epithelial down-growth
13. To look for vitreous strands incarcerated in the surgical wound
14. To view copper deposition on Descemet’s membrane
15. To study patency of trabeculectomy fistula
16. To view a peripheral laser iridotomy
17. To visualize the internal ostium of glaucoma drainage device
18. To see orientation of haptics of an anterior chamber intraocular
lenses.
Therapeutic
1. Laser trabeculoplasty
2. Excimer laser trabeculotomy
3. Goniotomy/gonioplasty
4. Laser goniophotocoagulation
5. Reopening of a blocked trabeculectomy opening
6. Neodymium-doped yttrium aluminum garnet laser after deep
sclerectomy
7. Laser of suture tied around tube of a glaucoma drainage device
8. Indentation gonioscopy to break an acute attack of PACG.
How: Gonioscopy should be performed to look for iridotrabecular
contact. Gonioscopy needs to be performed in a dark room with a
small slit-lamp beam.
1. Minimal room illumination
2. Good anesthesia
3. Shortest slit practicable
4. High magnification
5. Dim slit illumination
6. Set slit lamp or upper cornea, beam off-center 30°-45° nasally
7. If necessary, elevate upper lid
8. Place lens gently on eye while looking through slit lamp (as if
you are doing tonometry) no gel needed with Zeiss-type lenses
9. Look through the upper mirror (inferior angle) as you place
lens on eye, stop pushing when you can see the iris
10. Move slit-lamp beam inferiorly (avoid pupil) to examine
superior angle
11. Turn beam 90° and move on axis
12. Move to Nasal side (temporal angle) then to temporal side
(nasal angle)
13. Record findings on goniogram
14. In the presence of appositional closure, indentation should
be performed to look for Peripheral Anterior ynechiae
15. It may be necessary to alter the position of the mirror or the
position of the gaze to look over a convex iris to visualize the
angle
16. In steep iris profile do manipulative gonioscopy (over the hill view)
17. Indentation gonioscopy is used to open up the angle and
differentiate between oppositional or synechial closure.
What can happen on indentation
a. Concave iris opening (oppositional)
b. Angle widens but synechial closure seen
c. Iris moved backwards peripherally, but role of iris bulges out
and doesn’t assume concave configuration (plateau iris)
d. Iris moves slightly backwards, but maintains its convex profile
(large/displaced lens).
What to see
1. Level of iris insertion
2. Shape of peripheral iris profile
3. Width of the angle recess
4. Degree of trabecular pigmentation
5. Areas of iridotrabecular apposition
6. Areas of iridocorneal synechiae.
Normal adult angle
1. Ciliary body band
2. Scleral spur
3. Schlemm’s canal
4. Pigmented trabecular meshwork
5. Non-pigmented trabecular meshwork
6. Schwalbe’s line.
Tips
1. Start form top mirror
2. Identify corneal wedge to locate Schwalbe’s line
3. Avoid folds in descemet’s membrane, which is a sign excessive
pressure
4. Avoid excess illumination
5. Avoid direct light on pupil.
Documentation
There are four angle grading systems:[13,14]
1. Shaffer
2. Spaeth
3. Scheie
Table 1: Comparison of Goldmann single mirror and zeiss
four mirror
Type of lens Goldmann single
mirror
Zeiss four
mirror
Diameter of corneal contact 12 mm 9 mm
Angle of mirror height 62° 64°
Radius of curvature 17 mm 12 mm
Coupling fl uid Required Nor required
Indentation gonioscopy Not possible Possible
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4. RPC classification (Dr. Rajendra Prasad Centre for ophthalmic
sciences.
Tip
Practically document what you see [Figure 3]:
Pigmentation ± (Trabecular Meshwork 1-4)
Iris shape - S/R/Q
S - Straight; R - Regular; Q - Queer.
ONH
ONH evaluation is gateway to diagnosis of glaucoma [Figure 4].
Structural damage of ONH and RNFL are first to occur in glaucoma.
30-50% of ganglion cells are lost before a change is observed on
w/w perimetry.
Why: It defines glaucoma.
When: At every visit.
What: Qualitative:
• Neuroretinal rim (NRR)
• Optic disk hemorrhage
• Para papillary choroidal atrophy
• Barred circum linear vessels (CLV)
• Nerve fiber layer (NFL) defect.
Quantitative:
• Vertical disk diameter
• Vertical cup to disk ratio (C:D)
• Rim to disk ratio (R:D) at thinnest portion of rim
• NFL height optical coherence tomography (OCT).
Size-average: 1.5-2 mm. Classify discs as small/average/large.
Stereoscopic views with the slit lamp using indirect condensing
lens and considering magnification factor.
60 D × 0.88
78 D × 1.1
90 D × 1.3.
Welch Allyn ophthalmoscope smallest aperture casts an
illumination of 1.75 Sq. mm.
Does refractive status play a role. Up to −5 D to +5D - no
change seen. Hyperopes more than +5D - small discs. Myopes
more than −5D - large discs note-small discs need more attention.
Cup disc ratio
1. Vertical cup disc ratio is important
2. Stereoscopic view is required
3. Small discs have small C:D
4. Larger discs have large C:D
5. Change in C:D ratio indicates progression over period of time
6. Difference of 0.2 in C:D of two eyes is very significant
7. C:D changes super seed the perimetric changes
8. C:D of 0.7 is taken as cut off from healthy eye and glaucomatous
eye.
Rim discs ratio
It is designed by Spaeth. Takes into consideration the vertical
long axis where the rim is thinned. It makes more sense than C:D.
NRR
1. The rim is more important than the cup
2. Cardinal feature of G ON is a loss of tissue from inner edge of
rim
Figure 2: Peripheral Anterior Synechiae Gonioscopy a text and atlas
(Tanuja Dada)
Figure 3: Diagraming gonioscopy with concentric circles. Dianosis and
therapy of the glucomas (Becker-Shaffer’s)
Figure 4: Neuroretinal rim Diagnosis and management of glaucoma
(Jaypee Highlights) (Arvind Eye Care System) Auther – R.
Ramakrishnan, SR Krishnadas, Mona Khurana, Alan L Robin
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3. Check inferior superior nasal temporal (ISNT) rule-in majority
of eyes the rim is broadest in the inferior disc region followed
by the superior disc region, the nasal disc region and finally
a temporal disc region
4. ISNT rule is followed in 50-60% of cases
5. Early rim loss is manifested at superior temporal and inferior
temporal region[15]
6. Bared of circum linear vessel (CLV) is an early sign of NRR
thinning
7. Color - pallor more than cupping is suggestive of neurological
disc
8. Cataractous eye gives a hyperemic hue
9. Localized pallor of NRR may be seen after an acute attack.
RNFL[16]
Where: To be seen in superior and inferior are arcuate zone within
two disc diameter of the disc.
Appearance: RNFL are thickest in upper and lower poles hence
double hump seen in imaging.
Loss is of two types wedge shaped and diffuses loss. Apex of
wedge is on a disc margin and fans out in arcuate zone. Vessels
appear darker.
How to see: On slit lamp with green filter or fundus photograph
or on imaging technologies.
Difficult is to be seen in older persons and lens opacities.
Parapapillary atrophy (PPA) changes [17-20]
Beta zone-marked atrophy of retinal pigment epithelium (RPE)
leading to good visibility of large choroidal vessel and sclera.
It is seen besides or next to disc margin. Alpha zone-hyper or
hypo pigmentation of RPE. It is next to alpha zone. PPA has
high prevalence in glaucomatous eyes. PPA is a risk factor for
progression.[21] PPA is a useful in detection of glaucoma progression
in myopia.
Vascular signs of glaucoma
Disc hemorrhage
1. They are splinter shaped or flame shaped at the border of optic
disc
2. Important risk factor for glaucoma progression
3. Suggestive of ongoing damage to the ONH
4. Independent risk factor for development of glaucoma
5. In OHT disc hemorrhage presence increases conversion risk
by 6 times[22]
6. Recurrent hemorrhages increases risk by 3-4 times[23]
7. 70% hemorrhages are not glaucomatous.
Bayone ing of vessel
Bayonetting is rarely seen in normal discs even in presence of
large physiological cups.
Retinal arteriolar narrowing
The diameter of arteriole is narrower at the immediate region
around the optic disc compared with its diameter in more
peripheral region of retina. It is not specific of glaucomatous
change.
BCLV: A small branch of central retinal artery or vein recedes
from the inner disc margin as the cup enlarges. Barring of CLV
should prompt us to look for other signs of glaucoma.
Nasalization of vessel: Progressive nasalization may occur as
a result of progressive NRR loss.
Acquired pit of optic nerve (APON)[24]
The difference between notch and pit is that an APON is localized
loss of optic nerve tissue extending deep into lamina and disc
margin. Notch doesn’t extend deep into lamina.
Steps in clinical examination of ONH
• Determine disc size
• Check for unusual disc shape
• Determine the vertical C:D
• Determine cup and rim size in relation to disc size
• Evaluate rim shape (which is the narrowest rim) and apply
the ISNT rule
• Check RNFL (red free illumination)
• Look for disc hemorrhages
• Look for vascular changes: Bending of vessels, BCLV, collaterals,
anterior constriction
• PPA (beta zone)
• High myopia: Rule out glaucoma
• Rule out non-glaucomatous causes of cupping
• Correlate VFs with optic disc changes.
Documentation
• Disc drawings using colored pencils
• Disc photographs monoscopy
• Disc photographs stereoscopy
• Newer imaging technologies like Heidelberg Retinal
Tomogram /Optical Coherence Tomography/Glaucoma
Diagnostics -Variable Corneal Compensator.
Features of non-glaucomatous optic atrophy
• Pallor more than cupping
• Marked asymmetry between fellow eyes
• VF defects respect vertical meridian an are out of proportion
to degree of cupping
• Visual acuity out of proportion to degree of cupping
• Relative Afferent Pupillary Defect in presence of C:D <0.3
• Younger age
• Unilateral progression.
Perimetery
Why: Defines state of optic nerve function. Define visual
impairment.
When: When Glaucoma in suspected on examination.
Machine: Humphrey/octopus/medmont.
Which test: Central fields 30.2 threshold, 24.2 threshold.
Defects approaching fixation use macular program.
How to read: GRADES.
Foveal threshold: V/A should correspond.
Patient’s reliability decreases with age health and fatigue.
Take care of: Pupil size at least 3 mm.
Refractive correction ± 3 D.
G - General information
R - Reliability
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Mazhar: Nuggets in glaucoma
A - Abnormal/normal
D - Defect
E - Evaluate clinically
S - Subsequent evaluation.
• Interpretation-1. Global indices
• Mean deviation (MD) = generalized depression.
• Pattern standard deviation (PSD) = localized loss
• Glaucoma hemi field test (GHT) = early affected and most
sensitive in early disease process.
2. Anderson criteria to be satisfied.
Approach of interpretation of VF defects according to the stage
of glaucoma is given in Table 2.
Tips[25]
1. When we use decibels (dB) to express light sensitivity a high
dB value indicates dim light and low dB value indicates bright
light.
2. In the point pattern the bare area around the fixation spot is
a circle of 3° radius because the distance between the points
to the axis is 3°.
3. Raw data is strategy specific. Different strategies will have
different raw data hence for comparison same test strategy
should be used in the same patient.
4. Statistical Packagecalculates the P value for the points where
there is loss of sensitivity.
5. The pattern deviation plot is nothing but the total deviation
minus a generalized field defect worth of the dB value that
converts the 7th best sensitivity points of Total Deviation
Numerical Plot to 0 deviations.
6. During follow-up tests, the most important index to assess
field progression is MD index.
7. The increase in MD >0.08 dB/year should be considered
abnormal.
8. Never come to a conclusion of foveal split unless you see 0 dB
sensitivity in any four points on 1° circle around fixation point
of 10-2 raw data.
9. GHT is useful only in early cases.
Andersons criteria
At least two consecutive occasions GHTs outside normal limits.
Cluster of three or more non-edge points in location typical for
glaucoma, all of which are depressed on PSD at a P < 5% and one
of which is depressed P < 1% (P = Probability) PSD that occur in
<5% of normal individuals.
How many times fi elds should be done
1. At least twice/ideally thrice to establish base line field.
2. Two consecutive reproducible fields to establish progress.
3. Mild glaucoma-yearly.
4. Moderate glaucoma-6 monthly.
5. Severe Glaucoma with macular area threatened-quarterly.
Field progression
• Event based-shows changes
• Trend based-shows rate of change.
Programs
1. Overview printout
2. Glaucoma change analysis
3. Glaucoma change probability
4. VF index.
Conclusion
Glaucoma being an important cause of irreversible blindness, its
early detection and appropriate management goes a long way
in reducing the socio economic burden of the individual’s family
and this country
. Currently the optimal method for detection
of glaucoma at our clinic is comprehensive eye examination of
individuals attending our clinic for any reasons.
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Table 2: Approach of interpretation of visual fi elds based
on the stage of glaucoma
The point pattern - 30-2
or 24-2
Testing strategy-SITA
standard
Reliability indices-100%
perfect
Reproducibility-t he field
defect should be
reproduce d a minimum
of two times
Anderson’s criteria
should be fulfilled
Established glaucoma
Aim-to know the depth
and extent of the field
loss and its relation to
fovea
24-2 point pattern
Raw data
Total deviation
numerical plot
Total deviation
probability plot
MD index should be
looked at
Advanced glaucoma
Aim-to know the exact
residual retinal
sensitivity and foveal
status
10-2 point pattern and
raw data sho uld be
concentrated upon
Glaucoma Suspect
Aim-to know w hether
glaucoma is p resent or
not
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Cite this article as: Mazhar S. Nuggets in clinical approach to diagnosis of
glaucoma. J Clin Ophthalmol Res 2013;1:175-81.
Source of Support: Nil. Confl ict of Interest: None declared.
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