The Glaucoma Clinical Evaluation
The state-of-the-art diagnostic workup for a patient suspected
of developing, or having, glaucoma is straightforward. We recommend
conducting this systematic approach for near-perfect sensitivity
(true positives) and specificity (true normals).
- History. Not so much regarding their parents (or aunts and
uncles), but rather their siblings. If you see a 50- to 60-year-old
patient, his or her parents would have most likely been diagnosed
in the 1970s or 1980s—a time when most patients were treated
for “glaucoma” if their IOP went into the low to mid-twenties.
As is now well known, most of these folks said to have “glaucoma”
did not, in fact, have glaucomatous optic neuropathy; rather
merely had ocular hypertension. A history of vision loss known
to be attributable to glaucoma is important. Also keep in mind
that an older patient with glaucoma has children (most likely
in the 40- to 50-year-old age range) that merit a glaucoma
evaluation, as well.
- Best Visual Acuity (BVA). Knowing a patient’s best corrected
visual acuity is vital.
- Intraocular Pressure (IOP) by Goldmann
Applanation tonometry. A “screening” or one-time IOP is partial, incomplete data.
It is important to measure IOP at two to four different times
of the day to truly gain an understanding of the patient’s
diurnal curve. Only then can peak IOP be determined within
the confines of office hours. The ProView Home Tonometer (by
Bausch & Lomb) can help profile IOP behavior over a greater
range of time and can be especially helpful in obtaining a
more real-life IOP behavior. This is not necessary for all
patients, but can be very helpful in those patients whom you
suspect have peak IOPs outside of office hours—for example,
a patient with large cups and repeatable field loss who always
demonstrates “normal” IOP during office visits.
- Central Corneal Thickness (CCT) (Corneal
Pachymetry). In the
Ocular Hypertension Treatment Study (OHTS), it was shown that
thinner corneas result in falsely lower applanation tonometric
readings than the true IOP, leading the doctor to believe all
is well, when in fact the true IOP in many cases may remain
sufficiently high to perpetuate pressure-dependent ganglion
cell death, and ultimately advanced glaucoma. The thinner the
patient’s corneas, the greater the risk for this scenario.
Measuring the CCT has become standard-of-care and must be obtained
on all glaucoma suspects. By the way, there are two fundamental
glaucoma suspect categories: patients with large cups and “normal”
applanation pressures, and patients with ocular hypertension
and “normal” appearing optic nerve heads. All doctors caring
for glaucoma patients and glaucoma suspects must obtain a pachymeter
to meet the new standard-of-care. Our instrument of choice
is the Sonogage unit (www.sonogage.com).
- Slit Lamp Biomicroscopy. Anterior chamber depth, corneal guttata,
pigment dispersion, pseudoexfoliation, iridotomy, filtration
bleb, pigment clumping on the lens face from prior iritis,
anterior chamber clarity—these are why expert slit lamp examination
is critically important.
- Gonioscopy. We highly recommend the four-mirror design. Not
only does this enable excellent quantification of the iridocorneal
angle, but it allows for detection of peripheral anterior synechiae,
angle recession from prior trauma, angle pigmentation, and
angle debris from pigment, blood, or pseudoexfoliation. Perform
gonioscopy at baseline and about every five years thereafter,
as the angle can shallow as a result of lenticular thickening
with cataract development.
- Dilated Ophthalmoscopy. The stereoscopic evaluation of the
optic nerve head via slit lamp ophthalmoscopy is arguably the
single most important aspect of the clinical examination because
preserving anatomic integrity of this tissue is the centerpiece
of our efforts. Note the status of the neuroretinal rim tissues.
Are they pink and well-perfused? Are they thinned or eroded
(particularly at the inferotemporal and/or supratemporal pole)?
Is the cup deep? Is the nerve obliquely inserted? Is there
disc hemorrhage? Is there significant peripapillary atrophy?
Is the nerve pink, yellow, or pale? The answers to these questions
should be recorded in the patient’s chart.
- Zeiss-Humphrey Visual Fields. Testing using the Swedish Interactive
Thresholding Algorithm (SITA) software program is the gold
standard of perimetry. We almost always use the 24-2 program,
except in cases of very advanced field loss where we use the
10-2 program. This is not to say that other perimeters are
inferior, but virtually all studies and virtually all experts
utilize this technology, and we feel strongly that all doctors
should do their best to emulate the gold standard in every
aspect of patient care. This is what you desire when you seek
care. Frequency Doubling Perimetry is wonderful for screening
and detecting glaucoma, but not for use in actively managing
glaucoma. A major upgrade of the FDT is a new perimeter known
as the Matrix which is an almost exact replica of the Humphrey
Visual Field Analyzer except that it uses frequency doubling
targets. Also, Carl Zeiss Meditec (formerly Humphrey) now has
SITA-SWAP, a high-speed blue-on-yellow software program that
greatly improves SWAP testing.
- Glaucoma Imaging/Scanning Instruments
- These technologies
have finally reached "primetime" and can be helpful
in building a consensus opinion regarding the presence or
absence of glaucoma. They can also be helpful in staging
or quantifying glaucomatous optic neuropathy. They should
never be given undue weight in the decision-making process,
but always viewed as a component of the comprehensive glaucoma
work-up. While all these devices have strengths and weaknesses,
we use the GDx-VCC in our practices and are pleased with
its performance. Be sure to examine these technologies in
greater detail by clicking
here.
It is only when all this data is collected, interpreted and
assimilated by an astute, compassionate physician that patient
care is delivered at its highest level. Every doctor reading
this can achieve this level of expertise. For some, it will
be easy. For others, it will be more of a challenge. But
for all, it is a goal very much worthy of pursuit.
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