Glaucoma screening during regular optician visits, the specificity of screening in real life.

The aim of Vision 2020 (Netherlands), a project of the World Health
Organization (WHO), is to exterminate preventable blindness throughout the
world (The Netherlands) in 2020. Glaucoma is a chronic-progressive disease
which eventually can lead to blindness. Throughout the world glaucoma is the
second cause of avoidable blindness (Kingman S, 2004). Early stages of glaucoma
often remain unnoticed. Treatment can slow down or even stop the process.
Screening for glaucoma could therefore be useful. At this moment there is no
systematically screening programme for glaucoma in The Netherlands. It appears
that approximately half of the patients with glaucoma are undetected at a
certain moment (Hollows and Graham 1966; Wolfs et al. 2000). This can be a
reason to perform screening but on the other hand recent investigation showed
that about 1000 glaucoma screening tests would have to be performed in order to
prevent one case from becoming blind during live (many glaucoma patients pass
away before they become totally blind, even when they remain untreated). To
prevent unilateral loss of vision, about 200 tests should be done (Stoutenbeek
et al. 2008). A nationwide population based screening for glaucoma is not
automatically cost-effective, therefore we are also investigating other options
including screening during regular optician visits. Another study from our
research group showed that 80% of the population who are at risk for glaucoma,
visit an optician at least once in 5 years, and 84% is going to an optician or
ophthalmologist at least once in 5 years (Stoutenbeek and Jansonius 2006). The
same study showed that of the opticians who answered a questionnaire about
participation in a glaucoma screening programme, 91% were willing to
participate. At this time, most opticians perform glaucoma screening by
measuring the intraocular pressure (the main risk factor for glaucoma).
However, additional tests are necessary because previous investigation showed
that only half of the patients with glaucoma showed an increased intraocular
pressure at a single measurement (Katz et al. 1993), and it appeared that a lot
of newly-diagnosed glaucoma patients recently visited an optician where the
diagnosis glaucoma was not made. A study of GrØdum et al. showed that also many
glaucoma patients are overlooked in routine clinical ophthalmological practice
(GrØdum et al. 2002).
To further explore the feasibility of glaucoma screening in the Netherlands,
two studies will be performed. In the first study, the severity of glaucoma, at
the time patients are detected nowadays, will be investigated. In the second
study, a protocol for glaucoma screening by opticians will be introduced and
the specificity in *real life* will be calculated. The first study serves as a
baseline measurement that should enable the evaluation of the introduction of
screening in the future. This protocol describes the second study.

Primary Objective:
The aim of this study is to determine the specificity in *real life*, when
screening is performed during regular optician visits. This specificity will
depend on the specificity of the screening test, the frequency of other eye
diseases detected by this protocol and the skills of the optician. The subjects
with an abnormal screening test result will be divided in patients with
glaucoma (true positives) and patients without glaucoma (lfalse positives) The
latter group can be divided in subjects without any eye disease and subjects
with another eye disease (for example, cataract).

Secondary Objective(s):
Do these patients have risk factors for developing glaucoma?
Is (more) training/education needed for opticians?
How is the cooperation between opticians and ophthalmologists, are improvements
possible?

Study: Intervention study.

Duration: 1 year.

Setting of the study: Opticians will receive a protocol to screen patients for
glaucoma. All regular visitors >= 45 years will be screened. When a person is
referred to the hospital because of suspected glaucoma, additional tests will
be performed:
- Refraction (best corrected visual acuity): measured with a letter chart.

- GDx test: to measure the thickness of the retinal nerve fibre layer, patients
have to look into the lens of the camera and will see during a few seconds a
weak red background. A few images of each eye will be made and these will be
analysed against a database on the machine to see if the results are in the
normal range.

- Fundusphotography: the pupils of the eyes will be dilated with tropicamide
0,5 % and phenylerfrine 2,5% to allow us to get a good view of the back surface
of the eye. Once these drops are working, the patient places the chin on a
chin-rest and the camera is brought into place in front of the eye. The patient
will see a bright flash each time we take an image, which can dazzle the eyes
for a few minutes afterwards. Several images will be captured.

- Non-contact tonometry: or air-puff tonometry uses a rapid air pulse to
applanate the cornea. Corneal applanation is detected via an electro-optical
system. IOP is estimated by detecting the force of the air jet at the instance
of applanation. The patient places their chin on a chin-rest and needs to stair
straight ahead for the measurement. The IOP will also be measured by
applanation tonometry where a special desinfected prism is mounted on the
tonometer head and then placed against the cornea.

- The central corneal thickness will be measured using pachymetry. Measurements
are taken by placing an anesthetic drop (oxybuprocaïne 0.4%) on the eye and
gently touching the probe to the surface of the cornea. Three measurements will
be done of which the mean will be calculated.

- Standard automated perimetry (suprathreshold Humphrey Field Analyzer [HFA]):
after the patient has placed the chin on a chin-rest, a serie light stimuli on
a bowl-shaped screen is presented. The lights vary in brightness and will
appear in different positions in the field of view. There will be asked to
press a button each time a point of light is seen which the machine records.
The machine checks each point several times. The test will be performed for
each eye separately and the fixation will be tested previously. A print- out
will show the retinal sensitivity for different locations of each eye.

A questionnaire will be completed by the optician, about whether the visitor
has undergone glaucoma screening and if referral to the ophthalmologist is
necessary.

When a person arrives at the hospital a few questions will be asked concerning
the reason for visiting the optician, eye symptoms and risk factors for
developing glaucoma, before the additional investigation will take place.

Look at box: "study design".

It is possible that another disease will be discovered during the course of
this study. The, consequently, psychological distress for the patient can be a
disadvantage. The advantage will be, because of this (early) detection that
treatment can start immediately.

The eye drops that provide pupil dilation ensures that the patient sees several
hours less sharp. In the informationletter it is recommanded not to drive or
cycle the first hours. The advice is given to go home under supervision.