This document addresses the use of anterior optical coherence tomography (OCT) to obtain high-resolution images and measurements of the anterior segment ocular structures (cornea, anterior chamber, iris and the central portion of the lens) including the angle without the need for ocular anesthesia.

Investigational and Not Medically Necessary:

Optical coherence tomography of the anterior eye segment is considered investigational and not medically necessary for all indications.

The posterior segment of the eye includes the vitreous, retina, and optic nerve. OCT of the posterior segment has been used for screening, diagnosis and management of glaucoma and other retinal diseases. For the anterior segment of the eye, currently, gonioscopy is the gold standard for evaluation. Following gonioscopy, ultrasound biomicroscopy (UBM) has also been used to measure the anterior segment of the eye. UBM requires a water bath which can be uncomfortable. OCT employs non-invasive, non-contact, low-coherence interferometry to obtain high-resolution images and measurements of the anterior segment ocular structures (cornea, anterior chamber, iris and the central portion of the lens). The device is promising, but the data is primarily comparison studies between OCT and established techniques to measure the anterior segment ocular structure (Dada, 2007; Li, 2007; Pavlin 2009, Sakata 2008, Zhao, 2007). In one study by Radhakrishnan (2007), the researchers found that anterior segment optical coherence tomography (AS-OCT) using their prototype device demonstrated good to excellent reproducibility of the anterior chamber depth measurements when taken from the nasal and temporal quadrants but not the inferior quadrant. This led the researchers to conclude that "further assessment of the commercially available AS-OCT is needed to clarify this finding."

In the American Academy of Ophthalmology Preferred Practice Pattern^® Primary Angle Closure (2010), imaging of the anterior segment can be considered. Gonioscopy findings were found to be in general agreement with anterior segment imaging such as UBM and AS-OCT.

Mansouri and colleagues (2010) reported on the comparison of UBM to AS-OCT measurements in suspected primary angle closure, primary angle closure, or primary angle-closure glaucoma. It is essential to be able to visualize and measure the anterior chamber (AC) angle for the assessment of individuals with glaucoma. Thirty-three (33) participants, 55 eyes were examined by AS-OCT followed by UBM. Measurement of the trabecular-iris angle (TIA) was made in all 4 quadrants. In the AS-OCT group, the mean superior TIA was 19.3º and inferior TIA was 17.9º. In the UBM group, the mean superior TIA was 15.7º and inferior TIA was 16.7º. The differences between the two TIA measures were spread out over a range of about ±20º. This indicates poor agreement between the two methods for measurements. The authors stated "AS-OCT measurements were significantly correlated with UBM measurements but showed poor agreement with high differences in quantifying AC angle in individuals with narrow or closed angles."

Qui and colleagues (2011) reported on the use of Fourier-domain anterior segment optical coherence tomography (FD-ASOCT) to screen and diagnose dry eye, specifically human tear meniscus. One-hundred forty six (146) participants with dry eye and 160 control participants were enrolled in the study. Data was gathered using a dry eye questionnaire, measurement of the tear menisci using an AS-OCT system, tear film breakup time, corneal fluorescein staining, and Shirmer I test. Correct diagnosis of dry eye measured using the AS-OCT was 68.95% in tear meniscus height, 70.59% in tear meniscus depth, and 70.92% in tear meniscus area which "suggests limitations in dry eye diagnosis when using only meniscus measurements." The authors concluded that "dry eye is a complex condition" and "further research will be needed to ascertain the type of dry eye that is best diagnosed with FD-OCT." The American Academy of Ophthalmology Preferred Practice Pattern Dry Eye Syndrome (2008) does not address AS-OCT.

Several devices have received 510(k) clearance from the U.S. Food and Drug Administration as OCT devices. They have the potential for use as a rapid screening tool for detection of occludable angles. Ongoing clinical studies should help to evaluate efficacy in this regard (Radhakrishnan, 2005).

The AS-OCT devices employ non-invasive, non-contact, low-coherence interferometry to obtain high-resolution images and measurements of the anterior segment ocular structures (cornea, anterior chamber, iris and the central portion of the lens).

The devices are designed to image the shape, size and position of anterior components and make precise measurements of the distances between them, including angle-to-angle, angle size in degrees, pupil diameter, anterior chamber depth, and thickness and radii of curvature of the crystalline lens. The anterior segment is measured pre and post operatively for laser surgery in refractive surgeries.

Dry eye syndrome: A condition in which there are not enough tears to lubricate and nourish the eye.

Glaucoma: A group of diseases that can damage the eye's optic nerve and result in vision loss and blindness.

Gonioscopy: An examination using a lens-like device to evaluate the structure of the front part of the eye.

Optical refractive surgery: Surgery to the surface of the eye (cornea) to correct vision problems such as far- or near-sightedness.

Primary angle closure: The closure of the anterior chamber angle caused by multiple mechanisms.

Primary angle-closure glaucoma: A type of glaucoma that is caused by closure of the drainage structure of the eye.

The following codes for treatments and procedures applicable to this document are included below for informational purposes.  Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy.  Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Investigational and Not Medically Necessary:

Peer Reviewed Publications:

1. Dada T, Sihota R, Gadia R, et al. Comparison of anterior segment optical coherence tomography and ultrasound biomicroscopy for assessment of the anterior segment. J Cataract Refract Surg. 2007; 33(5): 837-840.
2. Konstantopoulos A, Hossain P, Anderson DF. Recent advances in ophthalmic anterior segment imaging: a new era for ophthalmic diagnosis? Br J Ophthalmol. 2007; 91(4): 551-577.
3. Li EY, Mohamed S, Leung CK, et al. Agreement among 3 methods to measure corneal thickness: ultrasound pachymetry, Orbscan II, and Visante anterior segment optical coherence tomography. Ophthalmology. 2007; 114(10): 1842-1847.
4. Mansouri K, Sommerhalder J, Shaarawy T. Prospective comparison of ultrasound biomicroscopy and anterior segment optical coherence tomography for evaluation of anterior chamber dimensions in European eyes with primary angle closure. Eye (Lond). 2010; 24(2):233-239.
5. Pavlin CJ, Vásquez LM, Lee R, et al. Anterior segment optical coherence tomography and ultrasound biomicroscopy in the imaging of anterior segment tumors. Am J Ophthalmol. 2009; 147(2):214-219.
6. Qiu X, Gong L, Sun X, Jin H. Age-related variations of human tear meniscus and diagnosis of dry eye with Fourier-domain anterior segment optical coherence tomography. Cornea. 2011; 30(5):543-549.
7. Radhakrishnan S, Huang D, Smith SD. Optical coherence tomography imaging of the anterior chamber angle. Ophthalmol Clin N Am. 2005; 18(3): 375-381.
8. Radhakrishnan S, See J, Smith SD, et al. Reproducibility of anterior chamber angle measurements obtained with anterior segment optical coherence tomography. Invest Ophthalmol Vis Sci. 2007; 48(8): 3683-3688.
9. Sakata LM, Lavanya R, Friedman DS, et al. Comparison of gonioscopy and anterior segment ocular coherence tomography in detecting angle closure in different quadrants of the anterior chamber angle. Ophthalmology. 2008; 115(5):769-774.
10. Zhao PS, Wong TY, Wong WL, et al. Comparison of central corneal thickness measurements by visante anterior segment optical coherence tomography with ultrasound pachymetry. Am J Ophthalmol. 2007; 143(6): 1047-1049.

Government Agency, Medical Society, and Other Authoritative Publications:

1. American Academy of Ophthalmology (AAO). For additional information visit the AAO website: http://www.aao.org/ppp. Accessed on August 2, 2011.
   • Preferred Practice Pattern Cataract in the Adult Eye. 2006.
   • Preferred Practice Pattern Dry Eye Syndrome. 2008.
   • Preferred Practice Pattern Primary Angle Closure. 2010.
   • Preferred Practice Pattern Refractive Errors & Refractive Surgery. 2007.

1. National Institute for Health; National Eye Institutes. http://www.nei.nih.gov/. Accessed on August 15, 2011.

iVue
Optical coherence tomography
RTVue/CA
Visante^®

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