Update on Optical Coherence Tomography (OCT)
OCT is currently the most exciting and high-profile technology
available. Every journal we have seen over the past year has
had at least one article on the OCT. While the HRT and GDx-VCC
devices can be helpful adjunctive technologies in the comprehensive
glaucoma evaluation, the OCT (originally developed to assess
macular disease) also has an excellent software program that
enables state-of-the-art glaucoma assessment. Note that we
did not use the term, “glaucoma diagnosis” here as it is the
physician - not an instrument - that diagnoses. The OCT can
properly be viewed as a “glaucoma-PLUS” technology. While
more expensive than the HRT or GDx-VCC, the OCT has much broader
clinical utility. If cost-feasible for your individual practice,
we urge you to investigate acquisition of the OCT. Should the
cost of the OCT be cost-prohibitive at this time, then by all
means acquire the GDx-VCC to enhance your abilities to assess
glaucoma risk. Remember that misdiagnosis of glaucoma is a
common cause of lawsuits.
Optical Coherence Tomography is a non-invasive technology
which provides high-resolution (10-15 micron) cross-sectional
and topographic images of the retinal and optic nerve tissues.
These images are truly incredible in their detail, and reveal
even the most subtle tissue alterations. The OCT reigns supreme
in the evaluation of macular edema and macular holes as well,
and can be extremely helpful in the diagnosis of a wide variety
of retinomacular diseases. Anecdotally, the OCT reportedly
has roughly halved the number of intravenous fluorescein angiographies
in clinical settings where both options are available. The
OCT can enhance patient care by decreasing referrals for angiograms
and thereby allows state-of-the-art disease management in the
primary eyecare office.
For those of you currently using the OCT for glaucoma quantification,
there are two journal articles in the January, 2005 Ophthalmology
which show the following:
“The OCT optic nerve head parameters (rim area, horizontal
integrated rim width - HIRW, and vertical integrated rim area
- VIRA) and peripapillary nerve fiber layer thickness provided
the best discrimination between normal and glaucomatous eyes.
Macular parameters were considerably less useful. “ 1
“The analysis of stratus OCT software-provided parameters
showed that parapapillary retinal nerve fiber layer (RNFL)
measures and optic nerve head (ONH) topographic parameters
had the highest power to discriminate glaucomatous from healthy
eyes.” Of the ONH parameters, “xthe cup/disk area ratio had
the highest sensitivity with specificity set at 95%x” “xthe
combination of an ONH parameter (cup/disk area ratio) with
RNFL thickness parameters resulted in the highest discriminant
function for glaucoma detection in our study.” 2 As in the
first referenced study above, these researchers also found
that “xmacular thickness parametersxhad at most a weak influence
on the discrimination between glaucomatous and healthy eyes.”2
M & T Commentary:
It is nice to see such close agreement between two similar
studies, and to have keener guidance as to which data best
helps us in our clinical assessments. If you have not yet
acquired a GDx-VCC or Stratus OCT-3, we strongly encourage
you to investigate these amazing technologies. Both are
available from Carl Zeiss Meditec (www.meditec.zeiss.com).
1. Wollstein, G., et al. “Comparison of Three Optical Coherence
Tomography Scanning Areas for Detection of Glaucomatous Damage.”
Ophthalmology, January 2005.
2. Medeiros, F.A. “Evaluation of Retinal Nerve Fiber Layer,
Optic Nerve Head, and Macular Thickness Measurements for Glaucoma
Detection Using Optical Coherence Tomography.” Ophthalmology,
January 2005.
FOR OCT OWNERS: There is also an excellent article entitled,
“Evaluation of Image Artifact Produced by Optical Coherence
Technology,“ by Ray, R., et al. that appears in the January,
2005 issue of Ophthalmology. This article gives a nice overview
on ways to distinguish disease processes from image artifact. |
