Ophthalmologic Techniques for Evaluating Glaucoma
© Blue Cross and Blue Shield of Montana
Current Effective Date:
July 18, 2013
Original Effective Date:
October 13, 2011
July 18, 2013
March 22, 2012; April 10, 2013
Glaucoma is a disease characterized by degeneration of the optic disc. Elevated intraocular pressure has long been thought to be the primary etiology, but the relationship between intraocular pressure and optic nerve damage varies among patients, suggesting a multifactorial origin. For example, some patients with clearly elevated intraocular pressure will show no optic nerve damage, while other patients with marginal or no pressure elevation will, nonetheless, show optic nerve damage. The association between glaucoma and other vascular disorders such as diabetes or hypertension suggests vascular factors may play a role in glaucoma. Specifically, it has been hypothesized that reductions in blood flow to the optic nerve may contribute to the visual field defects associated with glaucoma.
Conventional management of the patient with glaucoma principally involves drug therapy to control elevated intraocular pressures and serial evaluation of the optic nerve. Standard methods of evaluation include careful direct examination of the optic nerve using ophthalmoscopy or stereophotography, or evaluation of visual fields. There has been interest in developing more objective, reproducible techniques both to document optic nerve damage and to detect early changes in the optic nerve and retinal nerve fiber layer (RNFL) before the development of permanent visual field deficits. Specifically, evaluating changes in the thickness of the RNFL has been investigated as a technique to diagnose and monitor glaucoma. In addition, there has been interest in measuring ocular blood flow as a diagnostic and management tool for glaucoma. Several new techniques have been developed, and are described below:
Techniques to Evaluate the Optic Nerve/Retinal Nerve Fiber Layer
- Confocal Scanning Laser Ophthalmoscopy: Confocal scanning laser ophthalmoscopy (CSLO) is a laser-based image acquisition technique, which is intended to improve the quality of the examination compared to standard ophthalmologic examination. A laser is scanned across the retina along with a detector system. Only a single spot on the retina is illuminated at any time, resulting in a high-contrast image of great reproducibility that can be used to estimate the thickness of the RNFL. In addition, this technique does not require maximal mydriasis, which may be a problem in patients with glaucoma. The Heidelberg Retinal Tomograph is probably the most common example of this technology.
- Scanning Laser Polarimetry: The RNFL is birefringent, causing a change in the state of polarization of a laser beam as it passes. A 780-nm diode laser is used to illuminate the optic nerve. The polarization state of the light emerging from the eye is then evaluated and correlated with RNFL thickness. Unlike CSLO, scanning laser polarimetry (SLP) can directly measure the thickness of the RNFL. GDx® is a common example of a scanning laser polarimeter. GDx® contains a normative database and statistical software package to allow comparison to age-matched normal subjects of the same ethnic origin. The advantages of this system are that images can be obtained without pupil dilation, and evaluation can be done in about 10 minutes. Current instruments have added enhanced and variable corneal compensation technology to account for corneal polarization.
- Optical coherence tomography (OCT) uses near-infrared light to provide direct cross-sectional measurement of the RNFL. The principles employed are similar to those used in B-mode ultrasound except light, not sound, is used to produce the 2-dimensional images. The light source can be directed into the eye through a conventional slit-lamp biomicroscope and focused onto the retina through a typical 78-diopter lens. This system requires dilation of the patient’s pupil. OCT® is an example of this technology.
- Doppler Ultrasonography: Color Doppler imaging has also been investigated as a technique to measure the blood velocity in the retinal and choroidal arteries.
(Note: This policy only addresses uses of these techniques related to glaucoma.)
BCBSMT may consider analysis of the optic nerve (retinal nerve fiber layer) in the diagnosis and evaluation of patients with known or suspected glaucoma medically necessary when using scanning laser ophthalmoscopy, scanning laser polarimetry, and optical coherence tomography.
BCBSMT considers the measurement of ocular blood flow, pulsatile ocular blood flow or blood flow velocity with Doppler ultrasonography experimental, investigational and unproven in the diagnosis and follow-up of patients with glaucoma.
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- Rankin, S.J., Walman, B.E., et al. Color Doppler imaging and spectral analysis of the optic nerve vasculature in glaucoma. American Journal of Ophthalmology (1995) 119(6):685-93.
- Kaiser, H.J., Schoetzau, A., et al. Blood-flow velocities of the extraocular vessels in patients with high-tension and normal-tension primary open-angle glaucoma. American Journal of Ophthalmology (1997) 123(3):320-7.
- Cioffi, G.A. Three assumptions: ocular blood flow and glaucoma. Journal of Glaucoma (1998) 7(5):299-300.
- Fontana, L., Poinoosawmy, D., et al. Pulsatile ocular blood flow investigation in asymmetric normal tension glaucoma and normal subjects. British Journal of Ophthalmology (1998) 82(7):731-6.
- James, C.B. Pulsatile ocular blood flow. British Journal Ophthalmology (1998) 82(7):720-1.
- Kamal, D.S., Garway-Heath, D.F., et al. Use of sequential Heidelberg retina tomograph images to identify changes at the optic disc in ocular hypertensive patients at risk of developing glaucoma. British Journal of Ophthalmology (2000) 84(9):993-8.
- Retinal nerve fiber analysis for the diagnosis and management of glaucoma. Blue Cross Blue Shield Association Technology Evaluation Center Assessment. Chicago, Illinois: (2001 November) Volume 16, Tab 13.
- Bafa, M., Lambrinakis, I., et al. Clinical comparison of the measurement of the IOP with the ocular blood flow tonometer, the Tonopen XL and the Goldmann applanation tonometer. Acta Ophthalmol Scand (2001) 79(1):15-8.
- Evidence Based Guideline for Ophthalmologic Techniques to Evaluate Glaucoma. Blue Cross Blue Shield Association Technology Evaluation Center Assessment. Chicago, Illinois. (2003 August) Volume 18, Tab 7.
- Mohammadi, K., Bowd, C., et al. Retinal nerve fiber layer thickness measurements with scanning laser polarimetry predict glaucomatous visual field loss. American Journal of Ophthalmology (2004) 138(4):592-601.
- Zangwill, L.M., Weinreb, R.N., et al. The confocal scanning laser ophthalmoscopy ancillary study to the ocular hypertension treatment study: study design and baseline factors. American Journal of Ophthalmology (2004) 137(2):219-27.
- Zangwill, L.M., Weinreb, R.N., et al. Baseline topographic optic disc measurements are associated with the development of primary open-angle glaucoma: the Confocal Scanning Laser Ophthalmoscopy Ancillary Study to the Ocular Hypertension Treatment Study. Archives of Ophthalmology (2005) 123(9):1188-97.
- American Academy of Ophthalmology. Primary open-angle glaucoma suspect. Preferred practice pattern. San Francisco: American Academy of Ophthalmology; (2005). Available at: http://one.aao.org . (accessed 2007 December).
- Lalezary, M., Medeiros, F.A., et al. Baseline optical coherence tomography predicts the development of glaucomatous change in glaucoma suspects. American Journal of Ophthalmology (2006) 142(4):576-82.
- Kalaboukhova, L., Fridhammar, V., et al. Glaucoma follow-up by the Heidelberg Retina Tomograph. Graefes Arch Clin Exp Ophthalmology (2006 June) 244(6):654-62.
- Medeiros, F.A., Ng, D., et al. The effects of study design and spectrum bias on the evaluation of diagnostic accuracy of confocal scanning laser ophthalmoscopy in glaucoma. Invest Ophthalmology Visual Science (2007) 48(1):214-22.
- Lin, S.C., Singh, K., et al. Optic nerve head and retinal nerve fiber layer analysis: a report by the American Academy of Ophthalmology. Ophthalmology (2007) 114(10):1937-49.
- Harris, A., Kagermann, L., et al. Measuring and interpreting ocular blood flow and metabolism in glaucoma. Can J Ophthalmol (2008) 43(3):328-36.
- Chauhan, B.C., Hicolela, M.T., et al. Incidence and rates of visual field progression after longitudinally measured optic disc change in glaucoma. Ophthalmology (2009) 116(11):2110-8.
- Ophthalmologic Techniques of Evaluating Glaucoma. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Manual (2009 November) Vision 9.03.06.
Grewal, D.S., Sehi, M., et al. Comparing rates of retinal nerve fibre layer loss with GDxECC using different methods of visual-field progression. Br J Ophthalmol (2010 September 9) ((Epub ahead of print).
- Rusia, D., Harris, A., et al. Feasibility of creating a normative database of colour Doppler imaging parameters in glaucomatous eyes and controls. Br J Ophthalmol (2010 November 24) (Epub ahead of print).
- Ophthalmologic Techniques of Evaluating Glaucoma. Chicago, Illinois: Blue Cross Blue Shield Association Medical Policy Manual (2011 January) Vision 9.03.06.
||New Policy: |
||Policy updated with literature review through November 2011, Rationale revised; references added and reordered; policy statements unchanged|
||Policy formatting and language revised. Policy statement unchanged.|