Download Essential List Glaucoma Addendum

Addendum
IAPB ESSENTIAL LIST: GLAUCOMA—key
terms and meanings
Version: First Edition (March 2017)
What is Glaucoma?
Glaucoma is a group of eye diseases that lead to progressive, irreversible damage to the optic
nerve. It usually happens when fluid builds up in the front part of the eye. That extra fluid
increases the pressure in the eye (intra-ocular pressure – IOP) damaging the optic nerve.
The ability to detect, accurately diagnose, assess (extent or severity and stability), provide
medical, surgical or laser treatment and follow-up of people who have glaucoma or are at risk
of glaucoma, or had glaucoma treatment, are essential components of glaucoma care strategies
and vision preservation. Lowering IOP is the only intervention proven to prevent the loss of
sight from glaucoma: medications, laser, or microsurgery interventions can be used to halt the
loss of vision and preserve quality of life.
People with Chronic or Primary Open Angle Glaucoma (POAG), however, are usually not aware
of any signs or symptoms, especially in the early stages of the disease. By the time they present
to eye health providers, many have lost significant vision. Large-scale systematic screening of
older people is, however, not yet feasible because current screening strategies are not
practical, nor as effective at detecting glaucoma compared with the "gold standard" of a full
eye examination performed by an ophthalmologist.
The diagnosis and treatment of glaucoma is not simple. For example, Chronic or Primary Open
Angle Glaucoma (POAG) is:
Diagnosis is
based on a
number of
criteria:
POAG is associated with a number of characteristic structural and
functional changes to the eyes
✔Open Angle
Gonioscopy can provide confirmation of an open angle
✔Glaucomatous
Optic Nerve
Structural changes to the optic nerve head that can be seen clinically as a
large optic cup and thinning of the optic disc rim (with increased vertical
cup:disc ratio (VCDR) and/or asymmetry of the disc between the two eyes)
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Damage
± Elevated IOP ± Visual Field
Characteristic structural damage to the retinal nerve fibre layer may also be
identified clinically but is more easily recognised with Optical Coherence
Tomography (OCT1) (in vivo cross-sectional imaging)
Although glaucoma may occur with eye pressure in the normal range (≤21
mmHg), Increased intraocular pressure (IOP) is the major risk factor for
developing glaucoma. Thus when VCDRs and VFs are not possible, IOP is
used as an important clinical measure for the diagnosis of glaucoma
associated visual dysfunction (seen clinically as characteristic defects in the
visual fields (VF) / loss of field of vision.
Damage Other clinical parameters that are used include medical history (e.g., previous glaucoma
surgery) and visual acuity of less than 3/60 , or episodic pain in the case of angle closure
Neither is population based screening for glaucoma simple:
 Tests shown to be effective include pinhole visual acuity (cut off point of 6/18 in one or
both eyes) or optic disk examination (using a direct ophthalmoscope; cut off point of 0.7
for the vertical cup:disk ratio) ± combined with afferent pupil defect.
 Mass population screening is not currently recommended. However, all people
presenting for eye care should be reviewed for glaucoma risk factors and undergo
clinical examination to rule out glaucoma. Facilities with appropriate equipment and
personnel could provide screening and follow-up of high risk cases e.g. first-degree
relatives (FDR), early diagnosis and treatment of complex cases.
Low resource settings present additional challenges to people receiving the care they need.
Barriers to care include:
A – Awareness (lack of knowledge of the risk factors and symptoms associated with glaucoma
and the need for early detection, also compliance with management of the condition.
B – Beliefs (wrong beliefs and treatment rejection)
C – Compliance (poor compliance)
D – Distance from eye care services
E – Escort (lack of someone to accompany to the health visit)
F – Fear factor
G – Gender bias
Visual Fields
Visual fields were not used in the diagnosis and management in most patients in a specialist
glaucoma clinic, Cape Town. Patients present with advanced disease, which is easily diagnosed
without the use of visual fields. Progression of fields seldom contributes to monitoring and
1
in vivo cross-sectional imaging of the ONH and retina structure for diagnosis and
detection of progression. Anterior segment allows for direct visualization of the anterior
chamber angle.
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intraocular pressure is mainly used to monitor the adequacy of treatment.
Visual fields are not necessary in patients with reduced vision, extensive cupping and/or very
high IOP. Many patients have advanced disease at initial presentation. However, this is not
always the case and some patients may present earlier or with equivocal findings on
examination. Visual fields are then often quite useful. Progression of fields seldom contributes
to monitoring and intraocular pressure is mainly used to monitor the adequacy of treatment.
Types of Glaucoma surgery
Trabeculectomy is used in open angle and primary angle closure glaucoma: the eye's drainage
system is partially removed to create new channels for more normal flow of fluid. A
"controlled" leak of fluid (aqueous humor) from the eye, which percolates under the
conjunctiva. A small conjunctival "bleb" (bubble) appears at the junction of the cornea and the
sclera where this surgically produced valve is made.
Aqueous shunts are composed of a silicone tube and plate (valved or non-valved) used to direct
aqueous fluid from the anterior chamber to the subtenon’s space in the posterior fornix.
Trabeculotomy is an ab externo (from the outside) procedure for the management of
developmental glaucoma. It is performed by cannulating Schlemm’s canal from an external
approach followed by rupture through the trabecular meshwork into the anterior chamber.
Trabeculotomy is similar to a trabeculectomy, except that incisions are made without removal
of tissue.
Goniotomy typically is used for infants and small children, when a special lens is needed for
viewing the inner eye structures to create openings in the trabecular meshwork to allow
drainage of fluids.
Iridectomy is used in narrow-angle glaucoma, a small piece of the iris is surgically removed to
allow a better flow of fluid.
What should training to primary or community health care workers include?
Awareness programmes, case detection and referral
i) Programmes to raise awareness of risk factors
ii) Case finding and referral of anyone with risk
factors for a full eye examination
iii) Follow-up in the community, after secondary care
Risk Factors
 People with a relative who has
glaucoma – a parent, sister or
brother or older child
 People who are 40 years of age
or older (in some populations age
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iv) If the full eye examination is normal, patients can
then be followed up by primary and community care
workers every 1-2 years, bearing in mind that the risk
for developing glaucoma is life-long.
v) Follow up of people treated for glaucoma e.g. postoperative monitoring for complications; keep a
glaucoma register to identify and trace defaulters.ii
vi) Refer people for low vision assessment,
rehabilitation and social services if needed
30 or older may be more
appropriatei)
 People who wear strong
spectacles (i.e. very near -sighted
or far-sighted people), those who
have had an eye injury before, a
history of ocular inflammation, or
who use steroid eye drops
People who complain of vision or
field loss in one or both eyes
RESOURCES
Resources for screening Glaucoma
There are few effective (sensitive / specific) basic screening tests for general population
screening for glaucoma e.g. at primary level:
Cataract and glaucoma case detection for Vision 2020 programs in Africa: an evaluation of 6
possible screening tests.
Cook C1, Cockburn N, van der Merwe J, Ehrlich R.
J Glaucoma. 2009 Sep;18(7):557-62
Testing the pinhole visual acuity using a cut point of 6/18 in 1 or both eyes has a sensitivity and
specificity greater than 90%, a positive likelihood ratio greater than 10.0, a negative likelihood
ratio less than 0.1, and an accuracy greater than 90% for case detection of cataract or
glaucoma. Examination of the optic disk with a lens free direct ophthalmoscope using a cut
point of 0.7 for the vertical cup: disk ratio combined with testing for an afferent pupil defect
has similar values for case detection of glaucoma. These tests may be suitable for use in Vision
2020 programs in Africa.
Ophthalmology. 2001 May;108(5):968-75.
Sensitivity and specificity of tests to detect eye disease in an older population.
Ivers RQ1, Optom B, Macaskill P, Cumming RG, Mitchell P.
To compare the ability of tests of visual function to detect the presence of eye disease: retinal
and lens photography and subsequent grading of eye disease, tests of presenting and corrected
visual acuity, contrast sensitivity, screening visual field and intraocular pressure.
No single vision test predicted the presence of eye disease with any consistency. For glaucoma
and diabetic retinopathy there was no difference in area under the curve for any of the tests
examined, and no test had a good balance of sensitivity and specificity. Screening tests
(performed with presenting correction) did not perform as well as nonscreening tests (those
carried out after refraction with best correction).
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Current vision tests are not particularly good at detecting eye disease compared with the "gold
standard" of a full eye examination performed by an ophthalmologist. Further work in this area
should be carried out before vision-screening programs can be recommended for
implementation among older people.
Clin Experiment Ophthalmol. 2007 Apr;35(3):237-43.
Glaucoma screening: analysis of conventional and telemedicine-friendly devices.
Kumar S1, Giubilato A, Morgan W, Jitskaia L, Barry C, Bulsara M, Constable IJ, Yogesan K.
Combination of age and family history of glaucoma alone has a sensitivity of 35.6% (specificity
94.2%, area under the curve 0.81, correctly classified 81.1%) and an addition of telemedicinefriendly or conventional visual field tests optimized the sensitivity to 91.1% (specificity 93.6%,
area under the curve 0.95, correctly classified 93%). Analysis indicates good agreement
between vertical cup-to-disc ratio by ophthalmoscopy and digital image reading. An addition of
intraocular pressure test does not change sensitivity (35.6%) and specificity (94.2%).
This study indicates that evaluations of cup-to-disc ratio and visual field, using telemedicinefriendly devices, are most useful tools in screening for glaucoma. When used together these
devices may be an alternative for conventional glaucoma screenings.
Resources on Medical vs Surgical intervention for open angle glaucoma
Primary surgery lowers IOP more than primary medication but is associated with more eye
discomfort. One trial suggests that visual field restriction at five years is not significantly
different whether initial treatment is medication or trabeculectomy. There is some evidence
from two small trials in more severe OAG, that initial medication (pilocarpine, now rarely used
as first line medication) is associated with more glaucoma progression than surgery. Beyond
five years, there is no evidence of a difference in the need for cataract surgery according to
initial treatment.The clinical and cost-effectiveness of contemporary medication (prostaglandin
analogues, alpha2-agonists and topical carbonic anhydrase inhibitors) compared with primary
surgery is not known.Further RCTs of current medical treatments compared with surgery are
required, particularly for people with severe glaucoma and in black ethnic groups. Outcomes
should include those reported by patients. Economic evaluations are required to inform
treatment policy.
Cochrane Database Syst Rev. 2012 Sep 12;9:CD004399. doi:
10.1002/14651858.CD004399.pub3.
Medical versus surgical interventions for open angle glaucoma.
Burr J1, Azuara-Blanco A, Avenell A, Tuulonen A.
Resources for Laser treatment of Glaucoma
Laser treatment:
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

Open angle glaucoma: 1) laser trabeculoplasty can reduce the IOP by increasing outflow
of aqueous fluid from the eye (Selective Laser2 (SLT) and Argon laser3 Trabeculoplasty
(ALT) are equally good at lowering eye pressure) or 2) cyclophotocoagulation (laser to
the ciliary body processes to decrease the formation of aqueous fluid).
Narrow angle glaucoma: aqueous outflow is improved via 1) laser iridotomy4 where a
small hole is made in the peripheral iris, or 2) iridoplasty where the iris is tightened and
the drainage angle opened.
Cochrane Database Syst Rev. 2014 Feb 15;2:CD007059. doi:
10.1002/14651858.CD007059.pub2.
Non-penetrating filtration surgery versus trabeculectomy for open-angle glaucoma.
Eldaly MA1, Bunce C, Elsheikha OZ, Wormald R.
This review provides some limited evidence that control of IOP is better with trabeculectomy
than viscocanalostomy. For deep sclerectomy, we cannot draw any useful conclusions. This may
reflect surgical difficulties in performing non-penetrating procedures and the need for surgical
experience. This review has highlighted the lack of use of quality of life outcomes and the need
for higher methodological quality RCTs to address these issues. Since it is unlikely that better
IOP control will be offered by NPFS, but that these techniques offer potential gains for patients
in terms of quality of life, we feel that such a trial is likely to be of a non-inferiority design with
quality of life measures.
Can J Ophthalmol. 2013 Jun;48(3):186-92. doi: 10.1016/j.jcjo.2013.01.001.
Meta-analysis of selective laser trabeculoplasty with argon laser trabeculoplasty in the
treatment of open-angle glaucoma.
Wang H1, Cheng JW, Wei RL, Cai JP, Li Y, Ma XY.
To evaluate the efficacy and tolerability of selective laser trabeculoplasty (SLT) and argon laser
trabeculoplasty (ALT) in the treatment of open-angle glaucoma. SLT was associated with
relatively higher efficacy of IOP lowering compared with ALT. SLT results in a larger reduction of
number of glaucoma medications versus ALT, and it appeared to be more effective for patients
2
SLT uses a newer, lower-energy laser which only treats specific cells in the drainage
angle. SLT is considered technically easier to do and thus to teach than ALT: precise
placement of the laser beam is less critical, as is focus because of a larger spot with a
greater depth of focus. During ALT surgery, a laser makes tiny, evenly spaced burns in
the trabecular meshwork. The laser does not create new drainage holes, but rather
stimulates the drain to work better.
3
Can be used for peripheral iridotomy (PI), iridoplasty (ALPI) and argon laser
trabeculoplasty (ALT). May be part of retinal equipment)
4
A YAG laser can be used for faster peripheral iridotomy (acute or narrow angle
glaucoma). May be part of cataract equipment
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who did not respond adequately to previous laser treatment. The difference in tolerability of
the 2 lasers was not significant
http://eyewiki.aao.org/Laser_Trabeculoplasty%3A_ALT_vs_SLT#Efficacy_of_ALT_and_SLT
Disinfection of Tonometer heads
1. AAO cites: The CDC suggests that tonometer tips be wiped clean and then disinfected by
immersing for 5-10 minutes in either 5000 ppm chlorine or 70% ethyl alcohol. Then, after
disinfection, the tonometer should be thoroughly rinsed in tap water and air dried before use.
2. RCO(UK) suggests tonometer heads should ideally be rinsed in water, washed with
soap/detergent and rinsed again, then immersed in 1% sodium hypochlorite solution for at least
10 minutes; after which they should be rinsed (using sterile water) and dried
3. A recent study reported that cleaning with detergent and water seemed to effectively eliminate
bacteria and viruses from the surface of contaminated ophthalmic lenses Abbey AM, Gregori NZ,
Surapaneni K, Miller D. Efficacy of detergent and water versus bleach for disinfection of direct
contact ophthalmic lenses. Cornea. 2014 Jun;33(6):610-3.
Bandage contact lens
(N.B. may increase the risk of bleb infection and endophthalmitis)
Contact Lenses After Trabeculectomy. Gregory W. DeNaeyer, OD, FAAO
DeNaeyer GW. Contact Lenses After Trabeculectomy-With proper patient selection and
education, these patients can be successful lens wearers. Contact Lens Spectrum. 2010:36.
“There are three contact lens characteristics to consider when fitting a bandage soft lens to
treat a bleb leak. The first is lens diameter, which is dependent on the location of the bleb, leak
location, and bleb size. If the bleb and the location of the leak are proximal to the limbus, then
a standard bandage soft contact lens with approximately 14.00mm diameter may work (Figure
5). A larger-diameter contact lens with a diameter of approximately 20.00mm may be needed
for larger blebs or if the wound is 2.00mm or greater from the limbus (Figure 6). Secondly, the
soft bandage contact lens should have a low modulus, which will help it more easily drape up
and over the bleb, especially if the bleb is significantly elevated. Finally, choose a lens that has a
high Dk to reduce the risk of hypoxic-related complications, as the lenses will be worn on an
extended wear basis.”
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i
The prevalence of glaucoma has been reported as 6% in the 30-34 years age group and as 6.7% in the 35-39 years
age group. (Ntim-Amponsah C, Amoaku W, Ofosu-Amaah S, Ewusi R, Idirisuriya-Khair R, Nyatepe-Coo E, et al.
Prevalence of glaucoma in an African population. Eye. 2004;18(5):491-7).
ii Cook C Glaucoma in Africa: size of the problem and possible solutions. J Glaucoma. 2009 Feb;18(2):124-8.
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