Optical Coherence Tomography (OCT) of the Anterior Eye Segment
Optical coherence tomography (OCT) is a high-resolution method of imaging the ocular structures. Anterior segment (AS) OCT is being evaluated as a non-invasive diagnostic and screening tool for the detection of angle closure glaucoma, to assess corneal thickness and opacity, to evaluate presurgical and postsurgical anterior chamber anatomy, to calculate intraocular lens power, to guide surgery, to assess complications following surgical procedures, and to image intracorneal ring segments. It is also being studied in relation to pathologic processes such as dry eye syndrome, tumors, uveitis, and infections.
OCT is a non-invasive method that creates an image of light reflected from the ocular structures. In this technique, a reflected light beam interacts with a reference light beam. The coherent (positive) interference between the two beams (reflected and reference) is measured by an interferometer, allowing construction of an image of the ocular structures. This method allows cross-sectional imaging at a resolution of 6 to 25 μm. The Stratus OCT, which uses a 0.8-μm wavelength light source, was designed to evaluate the optic nerve head, retinal nerve fiber layer, and retinal thickness. The Zeiss Visante OCT and AC Cornea OCT use a 1.3-μm wavelength light source designed specifically for imaging the anterior eye segment. Light of this wavelength penetrates the sclera, allowing high-resolution cross-sectional imaging of the AC angle and ciliary body. The light is, however, typically blocked by pigment, preventing exploration behind the iris. Ultrahigh resolution OCT can achieve a spatial resolution of 1.3 μm, allowing imaging and measurement of corneal layers.
An early application of OCT technology was the evaluation of the cornea before and after refractive surgery. Since this is a non-invasive procedure that can be conducted by a technician, it has been proposed that this device may provide a rapid diagnostic and screening tool for the detection of angle closure glaucoma. The classification of glaucoma (primary open-angle or angle-closure) relies heavily upon knowledge of the anterior segment anatomy, particularly that of the anterior chamber angle. Angle closure glaucoma is characterized by obstruction of aqueous fluid drainage through the trabecular meshwork (the primary fluid egress site) from the eye's anterior chamber. The width of the angle is one factor affecting the drainage of aqueous humor. A wide unobstructed iridocorneal angle allows sufficient drainage of aqueous humor, whereas a narrow angle may impede the drainage system and leave the patient susceptible to angle closure glaucoma. The treatment for this condition is a peripheral iridotomy (laser) or peripheral iridectomy (surgery).
Slit lamp biomicroscopy is typically used to evaluate the anterior chamber; however, the chamber angle can only be examined with specialized lenses, the most common of these being the gonioscopic mirror. In this procedure, a gonio lens is applied to the surface of the cornea, which may result in distortion of the globe. Ultrasonography may also be used for imaging the anterior eye segment. Ultrasonography uses high frequency mechanical pulses (10 to 20 MHz) to build a picture of the front of the eye. An ultrasound scan along the optical axis assesses corneal thickness, anterior chamber depth, lens thickness and axial length. Ultrasound scanning across the eye creates a two-dimensional image of the ocular structures. It has a resolution of 100 microns, but only moderately high intra-observer and low inter-observer reproducibility. Ultrasound biomicroscopy (about 50 MHz) has a resolution of 30 to 50 microns. As with gonioscopy, this technique requires placement of a probe under topical anesthesia.
Multiple optical coherence tomography (OCT) systems have been cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process. Examples of approved systems are the Visante™ OCT (Carl Zeiss Meditec); the RTVue® (Optovue) (FDA product code: HLI); and the Slit Lamp OCT (SL-OCT; Heidelberg Engineering) (FDA product code: MXK). The microscope-integrated OCT devices for intraoperative use include the ReScan 700 (Zeiss) and the iOCT® system (Haag-Streit). Portable devices for intraoperative use include the Bioptigen Envisu™ (Bioptigen) and the Optovue iVue® (Optovue). Ultrahigh resolution OCT devices include the SOCT Copernicus HR (Optopol Technologies).
Commercially available laser systems such as the LenSx® (Alcon), Catalys® (OptiMedica), and VICTUS® (Technolas Perfect Vision) include OCT to provide image guidance for laser cataract surgery. FDA product code: OOE.
Custom-built devices, which do not require FDA approval, are also used.
The AC Cornea OCT (Ophthalmic Technologies, Toronto, ON) from Canada is not cleared for marketing in the United States.
See the Ophthalmologic Techniques of Evaluating Glaucoma for other ophthalmologic techniques of evaluating glaucoma.
POLICYScanning computerized ophthalmic (e.g., OCT) imaging of the anterior eye segment is considered investigational.
POLICY EXCEPTIONSFederal Employee Program (FEP) may dictate that all FDA-approved devices, drugs or biologics may not be considered investigational and thus these devices may be assessed only on the basis of their medical necessity.
The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.
Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.
POLICY HISTORY1/11/2008: Policy added
3/27/2008: Reviewed and approved by the Medical Policy Advisory Committee (MPAC)
04/22/2010: Policy description updated. Policy statement unchanged. Added FEP verbiage to the Policy Exceptions section.
03/07/2011: Added new CPT code 92132 to the Code Reference section.
05/07/2012: Policy title changed from "Anterior Eye Segment Optical Imaging" to "Optical Coherence Tomography (OCT) of the Anterior Eye Segment" to be consistent with the scope of the policy. Policy statement unchanged. Removed deleted CPT code 0187T from the Code Reference section.
04/17/2013: Policy reviewed; no changes.
03/18/2014: Policy reviewed; no changes.
03/11/2015: Policy description updated regarding devices. Policy statement unchanged.
08/03/2015: Code Reference section updated for ICD-10.
05/27/2016: Policy number A.9.03.18 added. Investigative definition updated in Policy Guidelines section.
09/16/2016: Policy description updated regarding devices. Policy statement unchanged.
SOURCE(S)Blue Cross & Blue Shield Association Policy # 9.03.18
CODE REFERENCEThis may not be a comprehensive list of procedure codes applicable to this policy.