BlueCross and BlueShield of Montana Medical Policy/Codes
Ophthalmologic Techniques for Evaluating Glaucoma
Chapter: Vision
Current Effective Date: March 22, 2012
Original Effective Date: October 13, 2011
Publish Date: March 22, 2012
Revised Dates: March 22, 2012

Several techniques have been developed to measure the thickness of the optic nerve/retinal nerve fiber layer (RNFL) as a method to diagnose and monitor glaucoma. Measurement of ocular blood flow is also being evaluated as a diagnostic and management tool for glaucoma.


Glaucoma is a disease characterized by degeneration of the optic nerve (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.

A comprehensive ophthalmologic exam is required for the diagnosis of glaucoma, but no single test is adequate for establishing the diagnosis. A comprehensive ophthalmologic examination includes an examination of the optic nerve by fundoscopy, evaluation of visual fields, and measurement of ocular pressure. The presence of characteristic changes in the optic nerve or abnormalities in visual field, together with increased intraocular pressure, is sufficient for a definitive diagnosis. However, some patients will show ophthalmologic evidence of glaucoma with normal intraocular pressures, therefore an elevated intraocular pressure is not essential for diagnosis.

Conventional management of the patient with glaucoma principally involves drug therapy, to control elevated intraocular pressures, and serial evaluation of the optic nerve to follow disease progression. 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. A variety of new techniques have been developed, as described here:

1. Techniques to Evaluate the Optic Nerve/Retinal Nerve Fiber Layer (Note: This policy only addresses uses of these techniques related to glaucoma.)

a. 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 Tomography is probably the most common example of this technology.

b. 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 approximately 10 minutes. Current instruments have added enhanced and variable corneal compensation technology to account for corneal polarization.

c. Optical Coherence Tomography

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.

2. Pulsatile Ocular Blood Flow

The pulsatile variation in ocular pressure results from the flow of blood into the eye during cardiac systole. Pulsatile ocular blood flow can thus be detected by the continuous monitoring of intraocular pressure. The detected pressure pulse can then be converted into a volume measurement using the known relationship between ocular pressure and ocular volume. Pulsatile blood flow is primarily determined by the choroidal vessels, particularly relevant to patients with glaucoma, since the optic nerve is supplied in large part by choroidal circulation.

3. Doppler Ultrasonography

Color Doppler imaging has also been investigated as a technique to measure the blood velocity in the retinal and choroidal arteries.


Prior authorization is recommended. Call Blue Cross and Blue Shield of Montana (BCBSMT) Customer Service at 1-800-447-7828 or fax your request to the Medical Review Department at 406-441-4624. A retrospective review is performed if services are not prior authorized.

Medically Necessary

Blue Cross Blue Shield of Montana (BCBSMT) considers analysis of the optic nerve (retinal nerve fiber layer) in the diagnosis and evaluation of patients with glaucoma or glaucoma suspects 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 investigational in the diagnosis and follow-up of patients with glaucoma.

Federal Mandate

Federal mandate prohibits denial of any drug, device, or biological product fully approved by the FDA as investigational for the Federal Employee Program (FEP). In these instances coverage of these FDA-approved technologies are reviewed on the basis of medical necessity alone. Call the BCBSMT FEP Customer Service Department at 1-800-634-3569 for benefit information.

Policy Guidelines

Effective in January 2011, there is a new code for this testing:

92133: Scanning computerized ophthalmic diagnostic imaging, posterior segment; with interpretation and report, unilateral or bilateral; optic nerve

There is also a category III CPT code for measurement of ocular blood flow by repetitive ocular blood flow measurement:

0198T: Measurement of ocular blood flow by repetitive pressure sampling, with interpretation and report.

During 1999-2010, there was a CPT code 92135 which may have been used to describe scanning computerized ophthalmic diagnostic imaging. Code 92135 may have been used to describe optical coherence tomography (OCT) as well. Code 92135 was discontinued December 31, 2010.

Prior to the creation of 0198T, there was no specific CPT code describing measurement of ocular blood flow. CPT code 92120 (tomography with interpretation and report), 93875 (noninvasive physiologic studies of the extracranial arteries), or 92499 (unlisted ophthalmologic service) may have been used.

CPT code 93875 (noninvasive physiologic studies of extracranial arteries, complete bilateral study including Doppler ultrasound spectral analysis) may also be used to describe Doppler ultrasonography of the choroidal arteries.


The use of various techniques of retinal nerve fiber layer (RNFL) analysis (confocal scanning laser ophthalmoscopy [CSLO], scanning laser polarimetry [SLP], and optical coherence tomography [OCT]) for the diagnosis and management of glaucoma was addressed by TEC Assessments in 2001 (1) and 2003. (2) The 2003 Assessment offered the following observations (2):

  • A variety of techniques to evaluate the RNFL were considered, including CSLO, SLP, and OCT. All 3 devices use different principles to directly evaluate the RNFL. All 3 devices give multiple specific measurement of the RNFL that can be followed up over time to evaluate a rate of change in the RNFL. In theory, they are highly sensitive and can detect subtle changes to the RNFL earlier than standard qualitative evaluations. The major potential benefit of these technologies is that they can provide a quantitative objective evaluation in contrast with the subjective evaluation provided by other methods of diagnosing and monitoring primary open angle glaucoma (POAG).
  • The Assessment evaluated whether adding RNFL analysis to other tests improves health outcomes. It is assumed that RNFL analysis would not influence decisions to begin treatment for suspected POAG when intraocular pressure is elevated or results of 2 of 3 conventional tests are positive. Conventional tests include ophthalmoscopic detection of atrophy of the optic nerve, visual field defect on perimetric testing, and increased intraocular pressure on tonometry. In patients without clear indications for topical medication, signs of optic nerve atrophy on RNFL analysis seen in advance of meeting other current diagnostic criteria for POAG may be used to begin early treatment. Using RNFL analysis to initiate early topical medication requires knowing how well RNFL results predict the development of visual loss. If the RNFL analysis is a poor predictor of future visual loss, its use could lead to errors in management, leading, for example, to overtreatment.
  • RNFL analysis may also play a role in monitoring patients who have already begun treatment for POAG. Patients showing a failed response to treatment on RNFL analysis may be referred to take a different class of topical medication or to undergo laser trabeculoplasty.
  • The best evidence would be direct evidence comparing outcomes of management guided by conventional tests with and without RNFL analysis.

The 2003 TEC Assessment (2) provided the following conclusions:

  • No randomized trials compare the health outcomes of management guided by conventional tests alone to outcomes of management guided by conventional tests plus RNFL analysis in the detection or monitoring of POAG.
  • The best available evidence on using RNFL analysis to predict visual loss comes from a study of scanning laser ophthalmoscopy (i.e., Heidelberg retinal tomography, HRT), in which 21 patients progressed from ocular hypertension to glaucoma (converters) and 164 patients did not progress (nonconverters). Of the 21 converters, 13 had abnormal HRT results, and in 11 of these the tests were positive before development of visual field defects (average lead time was 5.4 months). Of the 164 nonconverters, 47 had abnormal results. (3)
  • The positive predictive value (PPV) of HRT, given the available data, was 22%. The frequency of true-positives and false-positives in the Kamal et al. study (3) may depend on the duration of follow-up completed in this study, which was a mean of at least 33 months. If the frequency of true- and false-positives stays the same with more adequate follow-up, the consequence would be overtreatment in 78% of patients with a positive HRT finding. Additional follow-up is needed to show whether some false-positives are late converters who become true-positives.
  • Cross-sectional studies do not inform the prediction of future visual loss. These studies can reveal whether RNFL analysis can detect prevalent cases of glaucoma. RNFL analysis does not detect all prevalent cases; it is falsely negative in 14–36% of cases among recent cross-sectional studies using predetermined diagnostic criteria or blinded test interpretation.

Regarding pulsatile ocular blood flow or blood flow velocity (techniques not addressed by the TEC Assessment), there are similar deficiencies reported in the published literature. Specifically, no data from published clinical trials document how these devices should be incorporated into clinical practice and whether treatment decisions based on the use of these devices result in improved patient outcomes compared with the conventional methods of evaluation. Additional information is also needed to 1) document the association between blood flow and glaucoma; 2) determine the relevant vessels for study considering the complex blood supply to the optic nerve; and 3) establish the range of normal values, particularly in relation to other factors such as blood pressure, heart rate, and compliance of the blood vessels. (4-8)

Evidence Subsequent to the 2003 TEC Assessment

Periodic literature updates using the MEDLINE database, and focusing on longitudinal results, have been performed since the 2003 TEC Assessment. The most recent literature search was performed through November 2011. Following is a summary of the key literature to date.

1. Techniques to Evaluate the Optic Nerve/Retinal Nerve Fiber Layer

The Confocal Scanning Laser Ophthalmoscopy (CSLO) Ancillary Study, a subset of the Ocular Hypertension Treatment Study (OHTS), was designed to determine whether annual optic disc topographic measurements can accurately predict visual field loss. (9) The OHTS randomly assigned patients with elevated intraocular pressure to either topical hypotensive medication or observation. Baseline data reported from the CSLO Ancillary Study did not allow reaching conclusions about how well RNFL analysis measurements predict visual loss over time.

Follow-up of the CSLO Ancillary Study was reported in 2005. (10) Of 438 participants, 34% had abnormal CSLO values according to HRT criteria. The average interval between CSLO exams to POAG was 48.4 months (standard deviation [SD]: 25.2). Eyes not developing POAG were followed up a mean of 79.5 months (SD: 20.8). Sensitivity of CSLO for development of POAG using HRT criteria was 55.6% (95% confidence interval [CI]: 39.6 to 70.5%), specificity 68.2% (95% CI: 63.5 to 72.5%), and positive predictive value (PPV) 13.5% (95% CI: 8.9 to 20.0%). The investigators concluded that "[t]he current analysis did not directly determine whether the prediction model that includes baseline CSLO measurements is improved over the OHTS prediction model that includes baseline stereophotographic cup-disc ratio measurements…. Longer follow-up is required to evaluate the true predictive accuracy of CSLO measures."

At Manchester Royal Eye Hospital (UK), HRT and GDx systems were evaluated in cross-sectional (98 normal controls and 152 patients with POAG) and longitudinal studies (240 at risk of developing glaucoma due to high intraocular pressure or fellow eye with POAG and 75 with POAG). (11) With specificity set at 95%, sensitivities of the HRT and GDx in detecting POAG were 59% and 45%, respectively, in the cross-sectional study. In the longitudinal study, patients were evaluated biannually over an average 3.5-year follow-up. Evidence of visual field defects developed in 72 of the at-risk group. Poor agreement was found between the HRT and GDx for development of visual field abnormalities. Although sensitivities might vary according to definitions for conversion to a visual field defect, among patients with baseline HRT and GDx abnormalities, sensitivities could be as low as 13% to 39%. The authors concluded that “on account of the fact that the HRT and GDx fail to detect a significant number of cases of conversion, they cannot provide a replacement for visual field examination.”

Longitudinal results have also been reported from the University of California, San Diego (UCSD) Diagnostic Innovations in Glaucoma Study (DIGS). (12, 13) In the first publication, eyes from 160 glaucoma suspects evaluated with SLP were followed up for 1.7 to 4.1 years. Visual field damage developed in 16 (10%) participants. Only relative risks (RRs) for visual field damage were reported as opposed to sensitivities, specificities, and predictive values. (12) From 12 SLP parameters and a 13th calculated from those parameters, 3 were significantly associated with the visual field outcome in multivariate analyses (models were incorrectly specified owing to the small number of outcomes). In a subsequent report, 114 glaucoma suspects were examined with OCT (one eye per patient). (13) Over a 4.2-year average follow-up, 23 (20%) developed changes consistent with glaucoma. While the RR of developing glaucomatous changes was increased with thinner RNFL results (1.5-fold per 10 micrometers), sensitivities and specificities demonstrating clinical utility were not reported.

Kalaboukhova et al. enrolled 55 patients with ocular hypertension (OHT) and POAG (34 and 25, respectively) who were followed up for a median of 47 months (range, 22–86 months). (14) HRT was performed at entry (1998–2002) and re-examined between 2001 and 2005. Based on optic disc photographs, eyes were classified as progressive or stable; 22 showed progression. From 25 parameters evaluated, 5 were accompanied by statistically significant areas under the receiver operating characteristic (ROC) curve. However, no adjustments were made for multiple comparisons; the sample was small and one of convenience.

A technology assessment issued by the AAO in 2007 reviewed 159 studies published between January 2003 and February 2006, evaluating optic nerve head and RNFL devices used to diagnose or detect glaucoma progression. (15) The assessment concluded, “The information obtained from imaging devices is useful in clinical practice when analyzed in conjunction with other relevant parameters that define glaucoma diagnosis and progression.”

Studies continue to report on use of these techniques in patients with glaucoma/glaucoma suspects. In addition, studies report correlation of changes in RNFL analysis and changes in visual fields. (16)

2. Pulsatile Ocular Blood Flow

Measurement of ocular blood flow has been studied as a technique for evaluating patients with glaucoma. While reports of use have been longstanding, the report by Bafa et al. from 2001 (17) is one example, the clinical impact of this technique is not known. Reports have commented on the complexity of these parameters (18) and have also noted that these technologies are not commonly used in clinical settings. (19)

3. Blood Velocity Measured with Doppler Ultrasonography

A 2011 publication reported on color Doppler imaging (CDI) in normal and glaucomatous eyes. (20) Using data from reported studies, a weighted mean was derived for the peak systolic velocity, end diastolic velocity and Pourcelot's resistive index in the ophthalmic, central retinal and posterior ciliary arteries. Data from 3,061 glaucoma patients and 1,072 controls were included. The mean values for glaucomatous eyes were within 1 SD of the values for controls for most CDI parameters. Methodologic differences created inter-study variance in CDI values, complicating the construction of a normative database and limiting its utility. The authors noted that because the mean values for glaucomatous and normal eyes have overlapping ranges, caution should be used when classifying glaucoma status based on a single CDI measurement.

Resch and colleagues reported a cross-sectional study of optic disc morphology and ocular perfusion parameters in 103 patients with primary open angle glaucoma (POAG) in 2011. (21) Choroidal and optic nerve head blood flow was assessed using laser Doppler flowmetry, retinal blood velocity was measured with laser Doppler velocimetry, and retinal vessel diameters were measured with a Retinal Vessel Analyzer. Choroidal blood flow was not significantly associated with measures of glaucomatous damage or with morphologic parameters of the optic nerve head. Reduced retinal vessel diameters were slightly correlated with the degree of glaucomatous damage. Multiregression analysis showed optic nerve head blood flow to be most strongly associated with most measures of structural nerve head damage (e.g., r=0.28 for RNFL) and visual field loss. As indicated in the TEC Assessment, cross-sectional studies cannot determine whether changes in blood flow precede or are secondary to changes in the optic nerve head. Longitudinal studies are needed to evaluate if changes in blood flow are predictive of future visual loss.

Clinical Input Received through Physician Specialty Societies and Academic Medical Centers

While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process, through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.

In response to requests, input was received from 1 physician specialty society and 3 academic medical centers while this policy was under review in 2009. Three of the 4 reviewers providing input supported use of these techniques (CSLO, SLP, OCT) in the care of patients with glaucoma and those who are glaucoma suspects. Reviewers provided data to demonstrate that this testing is equivalent to expert assessment of optic disc photography for both detecting glaucoma and showing disease progression. Reviewers also commented on favorable aspects of this testing. For example, in contrast to other glaucoma testing, these tests can be done more easily, e.g., this testing does not always need to be done with dilated pupils, and ambient light level may be (is) less critical. In addition, while serial stereophotographs of the optic nerves are considered by many as the gold standard, these are not always practical, especially for general ophthalmologists. This testing also requires less cooperation from the patient, which can be helpful in some older patients.


Numerous articles describe findings from patients with known and suspected glaucoma using scanning laser ophthalmoscopy, scanning laser polarimetry, and optical coherence tomography. These studies report that abnormalities may be detected on these examinations before functional changes are noted. (22) The literature, specialty society guidelines, and clinical input indicate that optic nerve analysis using CSLO, SLP, and OCT has become an additional test that may be used in the diagnosis and management of patients with glaucoma and those who are glaucoma suspects. These results are often considered along with other findings to make diagnostic and therapeutic decisions about glaucoma care. Thus, this testing may be considered medically necessary.

Techniques to measures ocular blood flow or ocular blood velocity are used in evaluating various glaucoma treatments. The data for these techniques remain limited. Literature reviews have not identified studies that demonstrate the clinical utility for use of pulsatile ocular blood flow or blood flow velocity in patients with glaucoma. Some publications have described their use in studies comparing medication regimens in glaucoma. Others have suggested that these parameters may be helpful in understanding the variability in visual field changes in patients with glaucoma, i.e., this may help explain why patients with similar levels of intraocular pressure may develop markedly different visual impairments. However, data on use of ocular blood flow, pulsatile ocular blood flow, and/or blood flow velocity are currently lacking, and their relationship to clinical outcomes is not known. Therefore, their use remains investigational.

Practice Guidelines and Position Statements

The American Academy of Ophthalmology (AAO) 2010 POAG Suspect and POAG Preferred Practice Patterns recommend evaluating the optic nerve and retinal nerve fiber layer. (23) The documents state that “Stereoscopic disc photographs and computerized images of the nerve are distinctly different methods for optic nerve documentation and analysis. Each is complementary with regard to the information they provide the clinician who must manage the patient.” The guidelines describe 3 types of computer-based imaging devices that are currently available for glaucoma and are similar in their ability to distinguish glaucoma from controls: confocal scanning laser ophthalmoscopy, optical coherence tomography, and scanning laser polarimetry. “When examined for the ability of these devices to detect glaucoma progression, studies have shown a relative lack of concordance between the structural (the imaging devices) and functional (visual field) tests. Taken together, computer-based imaging devices for glaucoma provide useful, quantitative information for the clinician when analyzed in conjunction with other relevant clinical parameters.”

Medicare National Coverage

No national coverage decisions were identified.

Rationale for Benefit Administration

This medical policy was developed through consideration of peer reviewed medical literature, FDA approval status, accepted standards of medical practice in Montana, Technology Evaluation Center evaluations, and the concept of medical necessity. BCBSMT reserves the right to make exceptions to policy that benefit the member when advances in technology or new medical information become available.

The purpose of medical policy is to guide coverage decisions and is not intended to influence treatment decisions. Providers are expected to make treatment decisions based on their medical judgment. Blue Cross and Blue Shield of Montana recognizes the rapidly changing nature of technological development and welcomes provider feedback on all medical policies.

When using this policy to determine whether a service, supply or device will be covered please note that member contract language will take precedence over medical policy when there is a conflict.

ICD-9 Codes
365.41-365.44, 365.51-365.65, 365.81-365.90
ICD-10 Codes
H40.141-H40.149, H40.30-H40.33, H40.40-H40.43, H40.89, H40.9, H4, Z01.00-Z01.01 
Procedural Codes: 92120, 92133, 93875, 0198T
  1. Blue Cross and Blue Shield Technology Evaluation Center (TEC). Retinal nerve fiber analysis for the diagnosis and management of glaucoma. TEC Assessments 2001; Volume 16, Tab 13.
  2. Blue Cross and Blue Shield Technology Evaluation Center (TEC). Retinal nerve fiber layer analysis for the diagnosis and management of glaucoma. TEC Assessments 2003; Volume 18, Tab 7.
  3. Kamal DS, Garway-Heath DF, Hitchings RA 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. Br J Ophthalmol 2000; 84(9):993-8.
  4. Cioffi GA. Three assumptions: ocular blood flow and glaucoma. J Glaucoma 1998; 7(5):299-300.
  5. Fontana L, Poinoosawmy D, Bunce CV et al. Pulsatile ocular blood flow investigation in asymmetric normal tension glaucoma and normal subjects. Br J Ophthalmol 1998; 82(7):731-6.
  6. James CB. Pulsatile ocular blood flow. Br J Ophthalmol 1998; 82(7):720-1.
  7. Kaiser HJ, Schoetzau A, Stumpfig D et al. Blood-flow velocities of the extraocular vessels in patients with high-tension and normal-tension primary open-angle glaucoma. Am J Ophthalmol 1997; 123(3):320-7.
  8. Rankin SJ, Walman BE, Buckley AR et al. Color Doppler imaging and spectral analysis of the optic nerve vasculature in glaucoma. Am J Ophthalmol 1995; 119(6):685-93.
  9. Zangwill LM, Weinreb RN, Berry CC et al. The confocal scanning laser ophthalmoscopy ancillary study to the ocular hypertension treatment study: study design and baseline factors. Am J Ophthalmol 2004; 137(2):219-27.
  10. Zangwill LM, Weinreb RN, Beiser JA 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. Arch Ophthalmol 2005; 123(9):1188-97.
  11. Kwartz AJ, Henson DB, Harper RA et al. The effectiveness of the Heidelberg Retina Tomograph and laser diagnostic glaucoma scanning system (GDx) in detecting and monitoring glaucoma. Health Technol Assess 2005; 9(46):1-132, iii.
  12. Mohammadi K, Bowd C, Weinreb RN et al. Retinal nerve fiber layer thickness measurements with scanning laser polarimetry predict glaucomatous visual field loss. Am J Ophthalmol 2004; 138(4):592-601.
  13. Lalezary M, Medeiros FA, Weinreb RN et al. Baseline optical coherence tomography predicts the development of glaucomatous change in glaucoma suspects. Am J Ophthalmol 2006; 142(4):576-82.
  14. Kalaboukhova L, Fridhammar V, Lindblom B. Glaucoma follow-up by the Heidelberg retina tomograph--new graphical analysis of optic disc topography changes. Graefes Arch Clin Exp Ophthalmol 2006; 244(6):654-62.
  15. Lin SC, Singh K, Jampel HD 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.
  16. Grewal DS, Sehi M, Greenfield DS. Comparing rates of retinal nerve fibre layer loss with GDxECC using different methods of visual-field progression. Br J Ophthalmol 2011; 95(8):1122-7.
  17. Bafa M, Lambrinakis I, Dayan M 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.
  18. Schmidl D, Garhofer G, Schmetterer L. The complex interaction between ocular perfusion pressure and ocular blood flow - relevance for glaucoma. Exp Eye Res 2011; 93(2):141-55.
  19. Harris A, Kagemann L, Ehrlich R et al. Measuring and interpreting ocular blood flow and metabolism in glaucoma. Can J Ophthalmol 2008; 43(3):328-36.
  20. Rusia D, Harris A, Pernic A et al. Feasibility of creating a normative database of colour Doppler imaging parameters in glaucomatous eyes and controls. Br J Ophthalmol 2011; 95(9):1193-8.
  21. Resch H, Schmidl D, Hommer A et al. Correlation of optic disc morphology and ocular perfusion parameters in patients with primary open angle glaucoma. Acta Ophthalmol 2011; 89(7):e544-9.
  22. Chauhan BC, Nicolela MT, Artes PH. Incidence and rates of visual field progression after longitudinally measured optic disc change in glaucoma. Ophthalmology 2009; 116(11):2110-8.
  23. American Academy of Ophthalmology. Primary open-angle glaucoma suspect. Preferred practice pattern. San Francisco: American Academy of Ophthalmology. 2010. Available online at:  Last accessed December 2011.
October 2011 New Policy:
March 2012 Policy updated with literature review through November 2011, Rationale revised; references added and reordered; policy statements unchanged
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Ophthalmologic Techniques for Evaluating Glaucoma