**Background:**  
  
Scanning computerized ophthalmic diagnostic imaging (SCODI) is a noninvasive,
noncontact imaging technique that produces high resolution images of ocular
structures. These high resolution images are used to provide qualitative and
quantitative data about the structural or physiologic properties of structures
in the anterior and posterior segment that have been validated as clinically
useful in monitoring progression, resolution, or response to treatment of
various ocular conditions involving the retina and optic nerve over time.  
  
Scanning computerized ophthalmic diagnostic imaging makes use of 3 distinct
technologies to generate quantitative data:  
  
 confocal laser scanning ophthalmoscopy (CSLO)  
 scanning laser polarimetry (SLO)  
 optical coherence tomography (OCT)  
  
Examples of CSLO and SLO devices currently in use in clinical practice include
the Heidelberg Laser Tomographic Scanner, Heidelberg Retinal Tomography (HRT),
the GDx Nerve Fiber Analysis System, and the Retinal Thickness Analyzer (RTA).
OCT is available from a number of manufacturers using 1 of 2 basic platforms,
time domain (TD-OCT), such as the Visante anterior segment OCT, and the more
widely used spectral, or Fourier, domain (SD/FD-OCT), such as the Spectralis,
RTVue, Cirrus, and iVue.  
  
Although these techniques are different, their objective is the same. Medicare
will consider SCODI medically reasonable and necessary in evaluating disorders
of the anterior and posterior segment as documented in this local coverage
determination (LCD).  
  
 **Posterior Segment**  
  
Glaucoma is the second leading cause of blindness worldwide, and a disease for
which effective treatment to slow or prevent progressive vision loss is
available. However, glaucoma is diagnostically challenging and the majority of
patients are asymptomatic early in the course of disease when the disease is
most amenable to treatment. At the time of diagnosis, approximately 10-39% of
patients have irrecoverable vision loss from advanced glaucoma. Elevated
intraocular pressure is a clear risk factor for glaucoma, but over 40% of
cases have pressures in the normal range, while many other patients with
abnormally high pressures do not suffer glaucomatous damage. Structural
changes in the optic disc may not appear until a significant functional
deficit (visual field loss) has occurred.  
  
There is no single diagnostic test that can be used exclusively to diagnose
and monitor glaucoma. Diagnosis of glaucoma is made using an assemblage of
data from tests that provide complementary assessments of the functional and
structural status of the optic nerve. This often includes a comprehensive
history and eye exam including visual acuity measurement, pupillary
examination, intraocular pressure measurement, gonioscopy, anterior segment
exam, fundoscopy, optic disc and retinal nerve fiber layer examination; and
often confirmatory diagnostic tests including central corneal thickness
measurement, visual field evaluation (preferably using automated perimetry),
and quantitative imaging of the optic nerve head and retinal nerve fiber layer
with stereoscopic disc photographs and SCODI.  
  
SCODI allows for early detection of glaucomatous damage to the retinal nerve
fiber layer or optic disc, and has demonstrated clinical utility in
facilitating earlier diagnosis and treatment, as well as monitoring for
progression and response to treatment.  
  
SCODI also allows for differentiation and diagnosis of other disorders of the
optic nerve, as well as monitoring for progressive optic neuropathy and
response to treatment in a number of neuro-ophthalmologic conditions.  
  
Retinal disorders are among the most common causes of severe and permanent
vision loss. SCODI is an invaluable tool for the evaluation and treatment of
patients with retinal disease, particularly when there is macular involvement.
SCODI is able to detail the microscopic anatomy of the retina, subretina, and
vitreoretinal interface and provide information that has demonstrated evidence
of superiority to other available techniques in a number of clinical studies.  
  
SCODI has demonstrated clinical utility in monitoring patients with retinal
diseases for progression, which is critical for judging a response to or need
for treatment of a number of retinal conditions.  
  
SCODI has been validated for use in ongoing screening for drug-related ocular
toxicity, due to its ability to detect early photoreceptor damage in patients
taking certain high-risk drugs. The use of SCODI should be performed according
to the most current recommended guidelines. The current recommendations for
monitoring patients taking chloroquine or hydroxychloroquine include 1) a
baseline exam within the 1st year of commencement which should include a SD-
OCT if any macular abnormalities are present, and, 2) annual screening
beginning at the 5th year of exposure in patients who are on a dose <5 mg/kg
real weight and who lack other major risk factors. The presence of major risk
factors or a dosage exceeding 5 mg/kg real weight may necessitate earlier and
more frequent screening intervals.

  
**Anterior Segment**  
  
There are numerous reports in the literature detailing the potential
applications of anterior segment optical coherence tomography (AS-OCT and SD-
OCT with anterior segment imaging capabilities) to image and provide
measurements of anterior segment structures in a number of clinical
situations. The current literature consists primarily of qualitative and
quantitative imaging and detection capabilities, though there remains a lack
of consensus on the sensitivity, specificity, and predictive value of AS-OCT
in the vast majority of anterior segment applications and no endorsement of
its use over gonioscopy or ultrasound biomicroscopy.  
  
The strongest evidence in support of the clinical utility of AS-OCT lies in
its ability to image the structures of the anterior chamber angle,
particularly in narrow angles. Current recommended practice patterns by the
American Academy of Ophthalmology endorse gonioscopy as the preferred means of
performing evaluation of the anterior chamber angle. Although there remains
insufficient evidence to endorse AS-OCT as a substitute for gonioscopy, AS-OCT
is a recommended option in cases where angle closure is suspected, and the
angle anatomy is not conducive to gonioscopic assessment.  
  
 **Indications and Limitations:  
  
SCODI - Anterior Segment**  
  
SCODI, anterior segment, with interpretation and report.  
  
AS-OCT is considered reasonable and necessary when ordered for the evaluation
of narrow angle, suspected narrow angle, and mixed mechanism glaucoma:  
  
 In patients who are unable to undergo gonioscopy due to cognitive or
physical limitations  
  
 When anatomic features, corneal opacity, or corneal edema preclude
gonioscopic visualization  
  
Indications other than those stipulated in this LCD are considered
investigational and are not covered.  
  
SCODI is not covered for screening.  
  
SCODI is not covered in the absence of an indication.  
  
It is expected that no more than 2 AS-OCT tests per year would be indicated in
evaluating patients with a diagnosis of angle closure suspect, narrow angles,
angle closure, and mixed mechanism glaucoma without a significant change in
clinical status.  
  
It is expected that no more than 1  AS-OCT test per 3 years would be indicated
in evaluating patients with all forms of open angle glaucoma including
glaucoma suspect, ocular hypertension, secondary glaucoma, and congenital
glaucoma.  
  
 **SCODI - Optic Nerve**  
  
 SCODI, posterior segment, with interpretation and report, unilateral or
bilateral nerve.  
  
SCODI of the optic disc is considered reasonable and necessary when ordered
to:  
  
 Aid in the early diagnosis of glaucoma and monitor for progression and
response to treatment  
  
 Monitor glaucoma suspect patients for evidence of glaucomatous change  
  
 Detect further loss of optic nerve or retinal nerve fiber layer tissue to
aid in monitoring for progression in advanced optic nerve damage and advanced
visual field loss  
  
 Differentiate when there is a discrepancy between the clinical appearance of
the optic nerve and the visual field  
  
 Provide additional information to facilitate diagnosis and management when
visual field results are insufficient or cannot be performed due to visual,
mental, physical, or age limitations of the patient  
  
 Differentiate causes of other optic nerve disorders when a diagnosis is in
doubt  
  
 Aid in the diagnosis and management of other optic nerve disorders and
neuro-ophthalmologic diseases involving changes in the optic nerve head and
retinal nerve fiber layer  
  
SCODI is not covered when used for screening.  
  
SCODI is not covered in the absence of an indication.  
  
It is expected that no more than 1 SCODI test per year would be indicated in
monitoring patients with glaucoma suspect without a significant change in
clinical status.  
  
It is expected that no more than 2 SCODI tests per year would be indicated in
monitoring patients with progressive optic neuropathies, including glaucoma
(mild, moderate, severe, and indeterminate) without a significant change in
clinical status.  
  
Advancements in SCODI technologies have increased the utility of these devices
in both the diagnosis of glaucoma and detection of glaucomatous progression.
Hardware and software limitations can impact the reliability of these tests in
more advanced cases of glaucoma, particularly once the floor effect is
reached, whereby the ability to discern and measure thickness of the remaining
neural tissue limits the ability to detect progression. The use of SCODI in
advanced glaucoma is covered, provided the hardware and software utilized
continues to provide clinically meaningful measurements that allow for the
detection of progression.  
  
 **SCODI - Retina**  
  
SCODI, posterior segment, with interpretation and report, unilateral or
bilateral.  
  
SCODI of the retina is considered reasonable and necessary when ordered to:  
  
 Aid in the diagnosis and management of retinal conditions which involve
changes in the subretinal, intraretinal, and vitreoretinal relationships  
  
 Monitor for progression or resolution of conditions in order to determine
the need for or response to treatment  
  
 Monitor for evidence of ocular toxicity in patients taking high risk drugs
with a known potential for causing toxic retinopathy  
  
SCODI is not covered when used for screening.  
  
SCODI is not covered in the absence of an indication.  
  
SCODI should only be performed at clinically reasonable intervals (i.e.,
consistent with a noted change in clinical status or after sufficient time has
elapsed to assess for progression or response to treatment). It is generally
expected that conditions requiring more aggressive treatment and monitoring
due to changing clinical status or treatment interventions will generally not
require SCODI testing more than 1 per month.  
  
Current recommendations for monitoring patients taking chloroquine or
hydroxychloroquine, who are on a dose <5 mg/kg real weight, who lack other
major risk factors are recommended to undergo screening beginning at the 5th
year of exposure and annually thereafter. The presence of major risk factors
or a dosage exceeding 5 mg/kg real weight may necessitate earlier and more
frequent screening intervals.