Leung CK, Yu M, Weinreb RN, et al. Glaucoma Imaging Tests The glaucoma imaging tests are a reliable way for your doctor to monitor glaucoma progression. OCT is now very commonly used by both ophthalmologists and optometrists as a means to have additional documentation of the nerve fiber layer status. Invest Ophthalmol Vis Sci 2011;52:3338-3344. Jia Y, Wei E, Wang X, et al. It will provide a brief review of all modalities, but focus primarily on the Cirrus machine. A comprehensive glaucoma screening will involve several tests. Liu L, Jia Y, Takusagawa HL, et al. Structural changes in glaucoma can be detected with different imaging tools, including optical coherence tomography (OCT). A healthy retina is only ¼ of a millimeter thick, but it contains multiple layers of specialized cells. OCT became widely popular in 2002 with the release of Stratus OCT, a time-domain technology (TD-OCT) t… Perimetry is a visual field test that produces a map of your complete field of vision. Optical Coherence Tomography (OCT) is a non-invasive imaging technique that allows eye care professionals to measure the thickness and health of your retina’s multiple layers. One representative study compared the diagnostic capability of SD-OCT to TD-OCT RNFL thickness scans in subjects with early and moderate glaucoma as well as normal age-matched subjects. Leung CK, Yu M, Weinreb RN, et al. Glaucoma progression software incorporates statistical analysis of sequential OCT scans to detect progressive changes. Your pupils will be dilated using eye drops, and then the doctor will photograph your optic nerve with a digital camera, or use other technologies (OCT) to map your optic nerve. However segmenting the ganglion cell layer alone is very difficult based on reflectivity and thus Cirrus chose to measure its Ganglion Cell Analysis (GCA) consisting of the combined ganglion cell layer (GCL) and inner plexiform layer (IPL). EA compares a single follow-up test to baseline test(s). Following are six te… Prog Retin Eye Res 2007;26:688-710. 3. Effect of laser in situ keratomileusis and laser-assisted subepithelial keratectomy on retinal nerve fiber layer thickness. Ganglion cell analysis complicated by the presence of an epiretinal membrane. The calculated ONH parameters, except for disc area, are then compared to a normative database (see figure 2).1, The ganglion cell layer is thickest in the perimacular region and decreased total macular thickness has been observed in glaucomatous eyes likely due to thinning of the ganglion cell layer in this region. Both OCT and GDx are available at Glaucoma Associates of Texas. Progression is detected when the difference between baseline and a subsequent exam exceeds a predetermined threshold, based primarily on test-retest variability. An OCT scan is an important test in diagnosing and monitoring glaucoma. The signal strength, reported on a scale of 0 to 10, is defined as the averaged intensity value of the signal pixels in the OCT image. Am J Ophthalmol. Occasionally, one will find that the segmentation lines are misplaced along the retina leading to errors in the calculation of RNFL thickness (see figure 9). “Using spectral domain OCT is not a sufficient stand-alone test for the detection of glaucoma or for triage use in primary care, but it has value in conjunction with clinical examination and perimetry,” she said. (The AIG Study is recruiting normal, glaucoma suspect and glaucoma subjects in Los Angeles, Pittsburgh, Palm Beach and Cleveland. You child’s eye doctor will diagnose congenital glaucoma. These photographs are useful because they give detailed documentation of the appearance of the optic nerves, and they can be used as a baseline for future comparisons. [15] Similarly, a 9.3% increase in mean average RNFL thickness was seen after cataract surgery in a study of 45 patients. Codes for staging glaucoma include 365.71 (mild glaucoma), 365.72 (moderate-stage glaucoma) and 365.73 (severe glaucoma). 2. It is well known that significant structural RNFL loss occurs prior to the development of functional visual field loss. 2009;116:1960–1970. A complete eye exam includes a check for glaucoma. Alternatively, trend-based analysis defines progression by monitoring the change over time using regression analysis to provide a rate of progression and corresponding significance level.2. The current role of imaging in the diagnosis of glaucoma is unclear but of great clinical importance, said Dr Janulevičienė. OCT testing is like having an optical biopsy of the retina and optic nerve; it provides excellent visualization of these structures, and aids greatly in the diagnosis and treatment of glaucoma. The OCT Angiography (OCTA) is a non-invasive technology, marketed since 2014, that uses OCT with infrared light, with no radiation nor side effects, to evaluate within seconds the vascularization of the fundus, retina and optic nerve head, which may be useful for the glaucoma diagnosis. J Cataract Refract Surg 2006;32:446-450. J Ophthalmol Vis Res 2010;5:151-157. Curr Opin Ophthalmol 2012;23:79-88. All Rights Reserved. The normative database for the Cirrus SD-OCT consisted on 284 healthy individuals with an age range between 18 and 84 years (mean of 46.5 years). However, it is important to exclude any scans that are not of adequate quality. Due to this shift, although the peaks are of normal magnitude, they can be interpreted as thinned due to having a different distribution from the normative database. Beyond 55, people should have a glaucoma screening every year. Use of SD-OCT in Detection of Glaucomatous Progression, Repeatability and Reproducibility of SD-OCT, Aref AA, Budenz DL. Retinal nerve fiber layer split bundles are true anatomic variants. [20] Axial-length induced ocular magnification is not currently accounted for by Cirrus SD-OCT. Glaucoma can cause vision loss, often without any warning signs or symptoms. Kaliner E, Cohen MJ, Miron H, et al. The current machines we use for OCT … OCT has allowed us to intervene in the disease process before any functional loss has occurred and revolutionized the way we think about glaucoma. There are three main parameters relevant to the detection of glaucomatous loss: retinal nerve fiber layer, optic nerve head, and the “ganglion cell complex.” The numeric values for all parameters are shaded as white, green, yellow, or red, with the yellow and red representing, < 5% and < 1%, respectively compared to the normative database. We are an advocate for the vision health of Ontarians. OCT This state-of-the-art instrument is used to analyze the anatomic structure of the optic nerve head, or disc, and the retina. While different instruments analyze and present the data differently, there are two basic types of analysis: event analysis (EA) and trend analysis (TA). Effect of image quality on tissue thickness measurements with spectral-domain optical coherence tomography. This test will help a doctor determine whether your vision has been affected by glaucoma. It’s cutting-edge technology that allows optometrists to detect signs of glaucoma, among other serious eye conditions. Chang RT, Knight OJ, Feuer WJ, Budenz DL. Some doctors are using it to measure macular thickness and assess the status of glaucomatous damage. Additionally, myopic eyes can have unique distributions of RNFL bundles. The parameters found to be most diagnostically useful are minimum, inferotemporal sector, average, superotemporal sector, and inferior sector ganglion cell complex thickness.[6]. However, refractive error independent of axial length has not been found to affect RNFL thickness measurements as long as a well focused fundus image is obtained during scan acquisition by utilizing the Cirrus SD-OCT internal fixation focus adjustment. Cirrus does this by defining the edge of the disc as the termination of Bruch’s membrane and then finds the shortest perpendicular distance to ILM, AKA minimum band distance, to define the inner cup margin in each slice in a spiral around the optic disc cube data until a center is located. However, if damage is done to the optic nerve due to glaucoma, additional areas of blind spots will appear on the visual field test. OCT is newer technology. Optical coherence tomography (OCT) is a retinal scan used to study the anatomy of the retina and optic nerve in fine detail. Additionally, even in normal eyes, split RNFL bundles, both superiorly and inferiorly, have been found on histologic section, thus representing a true normal variant which may appear abnormal on SD-OCT (see figure 7). Chong GT, Lee RK. Agreement among spectral-domain optical coherence tomography instruments for assessing retinal nerve fiber layer thickness. [21] This adjustment can account for refractive errors from -20.0 D to +20.0 D.[22]. Mwanza JC, Bhorade AM, Sekhon N, et al. Opt Express 2009;17:4019-4036. Perimetry is a visual field test which examines the entire field of vision. SD-OCT can directly measure and quantify RNFL thickness by calculating the area between the internal limiting membrane (ILM) and RNFL border (how the edge of the RNFL is determined and how blood vessels are handled are different among the machines, which do not have interchangeable measurement outputs). In the presence of perimetric disease, finding RNFL bundle loss on SD-OCT with a corresponding abnormality in the visual field served by those retinal ganglion cells can help confirm the diagnosis of glaucoma. Hood D, Kardon R. A framework for comparing structural and functional measurements of glaucomatous damage. As mentioned previously, high myopes were not included in the normative database. Ophthalmology 2012;119:1151-1158. Furthermore, a good set of color optic nerve photographs will be forever useful even as technology advances. In one study, artificially defocusing an image scan by +2 diopters resulted in an artifactual 10 µm thinning of the RNFL. 365.74 is for indeterminate stage of glaucoma, which includes unreliable/uninterpretable visual; field testing, patient incapable of visual field testing or visual field not performed yet. The Eye Physicians and Surgeons of Ontario, a section of the Ontario Medical Association, represents more than 450 of Ontario’s ophthalmologists. [7] In such preperimetric disease, SD-OCT RNFL is especially useful in helping to diagnose glaucoma prior to the onset of visual field loss. Assessment of artifacts and reproducibility across spectral- and time-domain optical coherence tomography devices. Event-based analysis defines progressive change when a follow up measurement exceeds a pre-established threshold for change from baseline. This can … Special images (OCT) of the nerve that form the optic nerve can give clues to presence of glaucoma. This allows the 3.4 mm RNFL circle to always be centered in the same spot within the cube, which was not possible with TD-OCT. [13], When assessing the adequacy of a scan, the signal strength should always be noted. Myopic eyes have thinner RNFL measurements, which can confound comparisons to the normative database. Visual Field Testing for Glaucoma. 2. Leung CK, Yu M, Weinreb RN, et al. Glaucoma is an eye disease usually caused by having elevated pressure in the eye. Optical coherence tomography angiography of the peripapillary retina in glaucoma. [11], One common special case is the myopic patient. Ophthalmic Surg Lasers Imaging 2010;41:S15-27. [1] Automated software segmentation algorithms are able to outline the retinal nerve fiber layer with much precision, which is relevant in glaucoma since this layer is thinned as ganglion cells are lost. Effect of media opacity on retinal nerve fiber layer thickness measurements by optical coherence tomography. Not every patient needs an OCT test. Even if your vision and eye health are perfectly fine, we still recommend an OCT scan with every eye test. Balasubramanian M, Bowd C, Vizzeri G, et al. OCT measures the retinal nerve fiber layer thickness in glaucoma and other diseases of the optic nerve. [3] The Cirrus RNFL map represents a 6 x 6 mm cube of A-scan data centered over the optic nerve in which a 3.4 mm diameter circle of RNFL data is extracted to create what is referred to as the TSNIT map (temporal, superior, nasal, inferior, temporal). It is used to measure the retinal nerve fibre layers (RNFL) around the optic nerve which is an important marker of early to moderate glaucoma damage. In Ontario OCT testing is now covered by OHIP. One study of Cirrus found excellent intravisit and intervisit reproducibility of measurements of peripapillary RNFL thickness and ONH parameters. SD-OCT is a powerful objective structural assessment tool that can greatly assist clinicians in diagnosing and managing glaucoma (especially early disease), when used in conjunction with visual field testing and serial clinical exams. Optical coherence tomography (OCT), first described in 1991, is a noncontact, noninvasive imaging technique that can reveal layers of the retina by looking at the interference patterns of reflected laser light.Automated software segmentation algorithms are able to outline the retinal nerve fiber layer with much precision, which is relevant in glaucoma since this layer is thinned as ganglion cells are lost. Thinning of the optic nerve indicates that it is being damaged by elevated intraocular pressure. The influence of axial length on retinal nerve fibre layer thickness and optic-disc size measurements by spectral-domain OCT. Br J Ophthalmol 2012;96:57-61. This is a review of the utility of spectral-domain optical coherence tomography in the diagnosis and management of glaucoma. This test helps your doctor detect and monitor glaucoma. Mwanza JC, Durbin MK, Budenz DL, et al. Savini G, Barboni P, Parisis V, et al. [16], It is important to look at the segmentation lines produced by any SD-OCT machine’s software algorithm to ensure that they are appropriately placed. Although OCT analyses of macular and optic nerve neuroretinal rim thickness have become increasingly popular in recent years, RNFL analysis has been the benchmark of OCT imaging in glaucoma since its inception.2 RNFL analysis provides an alternative to the visual inspection of the optic nerve neuroretinal rim as well as a quantitative estimation of retinal ganglion cell axonal loss. Ophthalmology. As previously stated, SD-OCT measurements are compared against an age-matched normative database. Studies have evaluated the reproducibility and repeatability of SD-OCT measures relevant to assessing change over time. It can also detect if glaucoma is worsening over time. Glaucoma diagnostic accuracy of ganglion cell-inner plexiform layer thickness: comparison with nerve fiber layer and optic nerve head. The Academy uses cookies to analyze performance and provide relevant personalized content to users of our website. Am J Ophthalmlol 2011;151:85-92. 1989;107(5):453–64. Retinal nerve fiber layer imaging with spectral-domain optical coherence tomography: patterns of retinal nerve fiber layer progression. With increasing myopia, the superotemporal and inferotemporal RNFL bundles tend to converge temporally. The Cirrus macular scan map (see figure 3) is displayed using a similar color scale and divided into various pie sectors around the fovea. OCT is similar to ultrasound testing, except that imaging is performed by measuring light rather than sound. Spectral-domain optical coherence tomography (SD-OCT) represents arguably the most significant clinically validated advancement in diagnostic technology that the eye care community has seen for … © The Eye Physicians and Surgeons of Ontario - 2018. [5], Similarly, GCA parameters have been found to be comparable to ONH and RNFL parameters. Only four years later, several companies started to release the next generation technology, spectral-domain OCT (SD-OCT), AKA fourier-domain OCT, which improved upon TD-OCT by capturing more data in less time at a higher axial image resolution, around 5 µm. A few diagnostic instruments are used routinely in clinical practice to diagnose glaucoma. [8] A more cautious cutoff would be a 10 µm change, roughly twice the maximum standard deviation found in that study. OCT may detect glaucoma earlier than any other test. The tests are non-invasive and involve no radiation. Optical coherence tomography angiography of optic disc perfusion in glaucoma. When used as an ancillary diagnostic test in patients suspected of having glaucoma, OCT imaging aims to provide information that can assist clinicians in deciding whether an eye has glaucomatous damage, which can then be used for management decisions. Invest Ophthalmol Vis Sci 2010;51:5724-5730. One layer converts light into nerve signals, another processes the nerve impulses, while another transmits these processed impulses to the brain where they are interpreted. Ophthalmoscopy is a dilated eye exam which examines the shape and the color of the optic nerve. Glaucoma progression algorithms can be divided into event-based and trend-based approaches, similar to visual field progression detection methods. OCT testing is like having an optical biopsy of the retina and optic nerve; it provides excellent visualization of these structures, and aids greatly in the diagnosis and treatment of glaucoma and of retinal disorders like AMD. The intervisit tolerance limit for average RNFL thickness was 3.89 µm suggesting that a reproducible decrease of 4 µm or more may be a statistically significant change. For glaucoma OCT assesses the nerve fibre layer around the optic nerve and ganglion cell density in the macula. The main sign is a cloudy cornea. Applanation Tonometry : It measures the eye pressure which is currently the only modifiable risk factor in glaucoma. Not every patient needs an OCT test. It is displayed as a false color scale with the thickness values referenced to a normative database. The TECNIS ® Toric II 1-Piece posterior chamber lens is indicated for the visual correction of aphakia and pre-existing corneal astigmatism of one diopter or greater in adult patients with or without presbyopia in whom a cataractous lens has been removed by phacoemulsification and who desire improved uncorrected distance vision, reduction in residual refractive cylinder, and increased spectacle … Ethnically, 43% were Caucasian, 24% were Asians, 18% were African American, 12% were Hispanic, 1% were Indian, and 6% were of mixed ethnicity. A very important type of optic nerve imaging involves optic nerve photographs, or stereo disc photography. The only sure way to diagnose glaucoma is with a complete eye exam.A glaucoma screening that only checks eye pressure is not enough to find glaucoma.. During a glaucoma exam, your ophthalmologist will: measure your eye pressure; inspect your eye's drainage angle; examine your optic nerve for damage; test your peripheral (side) vision; take a picture or computer measurement of … Spectral domain optical coherence tomography in the diagnosis and management of glaucoma. Ultrahigh speed swept source OCT, ultrahigh resolution OCT, polarization sensitive OCT, and adaptive optics OCT are all on the horizon. These segmentation errors are more common in the presence of poor signal strength, tilted discs, staphylomas, large peripapillary atrophy, epiretinal membranes, and posterior vitreous detachments. Glaucoma versus red disease: imaging and glaucoma diagnosis. Perhaps the most important tool used to assess optic nerve function, determine whether glaucoma is present, and the status of glaucoma is the visual field test. OCT gives optometrists a better ability to detect and monitor minute changes in the retina and optic nerve than is possible through a standard eye test alone. OCT scans are recommended for people aged 25 or over, who want to know more about their eye health, or those who have diabetes, glaucoma, or have family history of eye disease. Carl Zeiss Meditec “Cirrus HD-OCT 5000 and 500: Technical Specifications” (, International Ophthalmologists contest rules, http://applications.zeiss.com/C1257A290053AE30/0/4BEACDCC7BCD1769C1257B6000392EB0/$FILE/CIRRUS_5000_Tech_Spec_CIR.4769.pdf, https://eyewiki.org/w/index.php?title=Spectral_Domain_Optical_Coherence_Tomography_in_Glaucoma&oldid=54495. The best quality scans have signal strength greater than 8 (minimum acceptable scan > 6). These ONH parameters were found to be as good as RNFL thickness parameters in diagnosing glaucoma. covers glaucoma tests once every 12 months if you’re at high risk for glaucoma. Tonometry tests the pressure of the inner eye. Sensitivity and specificity of time-domain vs spectral-domain optical coherence tomography in diagnosing early to moderate glaucoma. Studies have found a decreased incidence of such segmentation errors in SD-OCT compared to TD-OCT.[18], Axial length has been shown to influence SD-OCT measurements of both RNFL thickness and ONH parameters due to axial-length induced ocular magnification. Optical coherence tomography (OCT) is a noninvasive imaging technology used to obtain high-resolution cross-sectional images of the retina. Ophthalmology 2009; 116:1257-1263. Invest Ophthalmol Vis Sci 2012;53:7194-7200. Scans with a signal strength less than 6, with eye movement or blinking artifacts within the 1.73-mm radius around the optic nerve head, or with segmentation errors should be repeated. During this test, you will be asked to look straight ahead as a light spot is repeatedly presented in different areas of your peripheral vision. [12] This may result in the temporal shift of the superior and inferior RNFL bundle peaks of normal magnitude. The TSNIT map displays RNFL thickness values by quadrants and clock hours, and the RNFL peaks give a sense of the anatomic distribution of nerve fiber axons represented by the superior and inferior bundles that emanate from the optic nerve (see figure 1).1, SD-OCT also automatically outlines the optic nerve head, optic cup, and disc borders similar to mental estimations by clinicians, but then also calculates more objective measurements such as optic disc area and neuroretinal rim area in addition to the classic clinician-subjective average and vertical cup-to-disc ratios. To avoid overtreating “red disease” in these situations of all modalities, but it contains layers... Suspect and glaucoma diagnosis only modifiable risk factor in glaucoma a subsequent exam exceeds a predetermined,. Of glaucomatous damage Similarly, GCA parameters have been found to be as good RNFL. 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