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| NEW INSTRUMENT |
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| Year : 2020 | Volume
: 7
| Issue : 2 | Page : 50-51 |
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Mirante: Adding new dimensions to ultra-wide-field imaging system
Prashant K Bawankule1, Shilpi H Narnaware2
1 Vitreo-Retinal Surgeon, Sarakshi Netralaya, Nagpur, Maharashtra, India
2 Vitreo-Retinal Surgeon and ROP Specialist, Sarakshi Netralaya, Nagpur, Maharashtra, India
| Date of Submission | 05-Oct-2020 |
| Date of Acceptance | 22-Oct-2020 |
| Date of Web Publication | 1-Feb-2021 |
Correspondence Address:
Dr. Shilpi H Narnaware
Sarakshi Netralaya, 19, Rajiv Nagar, Wardha Road, Nagpur - 440 025, Maharashtra
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/erj.erj_14_20
How to cite this article:
Bawankule PK, Narnaware SH. Mirante: Adding new dimensions to ultra-wide-field imaging system. Egypt Retina J 2020;7:50-1 |
Retina is affected by various degenerations, inflammatory conditions, vascular retinopathies, tumors, and genetic and systemic disorders in varied forms. The anatomic location of these diseases can be from the most central part of the retina, i.e., disc, and macula to the most extreme periphery.
Before the era of ultra-wide-field imaging (UWFI) and wide-field (WF) imaging, the understanding and treatment of most of these disorders were based on the information we got from the imaging of just 90°–100° of the posterior retina. With the advent of UWFI and WF imaging, we are not just able to image the retinal periphery and the pathologies, but newer insight into the extent of these diseases and understanding of pathophysiology are being challenged, thereby changing the concepts in the management of these diseases. The documentation of these peripheral pathologies/involvement helps in easier follow-up. Not only is it more informative compared to optical cameras but also patient-friendly.
| Evolution | |  |
Initial/standard fundus camera could capture only 30°–50° of the central retina in a single click. With seven standard ETDRS photographs collage, one could reach out maximum up to 70°–90° of the retina. As standard camera is limited to the posterior pole only, peripheral degenerations and pathologies beyond equator, tumors, and peripheral involvement of the retina in vascular retinopathies were easily missed out.
WF imaging and UWFI, which can image 100°–200° in a single click, are the important tools to capture areas beyond the equator and therefore the pathologies.[1] These terms were defined by the International Widefield Imaging Study Group in 2019.[2] WF imaging means when retinal anatomic features are captured beyond the posterior pole but up to posterior to the vortex vein ampulla in all four quadrants, while UWFI shows retinal anatomic features anterior to the vortex vein ampulla in all four quadrants. Further, where dilated fundus examination is limited by pupil size, these systems can photograph the peripheral retina with small pupils.[3],[4] Both WF imaging and UWFI systems are not only limited to fundus photography, fluorescein angiography (FA), indocyanine green angiography (ICGA) of the central and peripheral retina but also utilize other technologies such as fundus auto-fluorescence (FAF), optical coherence tomography (OCT), and OCT angiography (OCT-A).
The new introduction in this group of UWFI is of Mirante by Nidek. It is an UWF multimodal imaging system which captures 163° in a single shot with a detachable WF adaptor [Figure 1]d. After montaging, the retina can be viewed up to ora serrata. The system is based on the confocal scanning laser ophthalmoscope (CSLO) principle. Three color channel monochromatic lasers in red–green–blue spectrum are used. These color channels image the retina and produce pseudo-colors which are near normal to the true retinal colors. CSLO system uses laser light to illuminate the retina, instead of bright flash photography, thereby reduces scatter of light in images acquired and avoids photophobia. | Figure 1: (a) Optical coherence tomography image. (b) Montage of fundus fluorescein angiography image. (c) Retro-mode image. (d) Color photograph
Click here to view |
In addition to fundus photographs, other facilities such as OCT [Figure 1]a, FFA [Figure 1]b, FAF ( green/blue) [Figure 1]c, ICGA and OCT-A are also incorporated in the system.[3] Retro-mode [Figure 2], a new feature is incorporated for the first time.
Other properties
- Ultra 4K HD averaging function: Provides a pixel resolution of 4096 × 4096, which is one of the highest in this category of instruments
- FlexTrack algorithm: Minimizes distortion and enhances quality
- Refine mode: To reduce reflections, captures two images with slightly different fixation.
Distinct features
- System includes four different LASERS with different levels of penetration:
- Blue (480 nm): Reflected by nerve fiber layer
- Green (532 nm): Reflected by ganglion cell layer
- Red (670 nm): Penetrated through retina
- Infrared (IR, 790 nm): Penetrated through choroidal layer.
The only imaging system with four LASERS, while all other systems have two LASERS. Each laser scans the retina through confocal optical setup. Multiple lasers produce pseudo-color images almost mimicking the natural colors.
- Fundus FA and ICG: The system allows simple, simultaneous acquisition of FA and ICG images by auto gain control, which simultaneously adjusts contrast of FA and ICG image. This evaluates even peripheral retinal ischemia (beyond equator) in patients with macular involvement such as diabetic macular edema, Retinal Vein Occlusions (RVO's), and other vascular retinopathies
Live IR monitoring reduces the risk of missing early phases of angiography as it enables alignment before fluorescence emission. It has advantages for alignment and focuses issues in prolonged and difficult scans
- Retro-mode: Unique noninvasive technique visualizes pathologies deeper than retinal pigment epithelium and helps in detecting pathologic changes in the choroid. Pseudo-three-dimensional images allow better appreciation of the extent of the pathology. It uses scattered IR light to detect abnormal reflection in the choroid
- Spectral-domain-OCT and OCTA: It captures 85,000 A-scans/s. 16.5 mm × 12 mm area scan allows macula and optic disc to be scanned in a single shot. Whole field from vitreous to choroid can be obtained in a single shot using this system. Options for AngioScan OCT-A and anterior-segment OCT are also available with this system
- FAF: Both blue and green FAFs are available with the maximum quality provided which is given by SLO technology.
Limitations
- Measured retinal lesion size and dimensions are not accurate
- Image artifacts.
| Conclusion | | |
Mirante is a new entrant in UWFI segment with additional benefits of multimodal imaging. Visualization of the peripheral retina has changed our basic understanding, thereby challenging the standard treatment formats. Multimodal imaging on a single platform adds further knowledge of the disease.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
| 1. | Staurenghi G, Sadda SR, Cozzi M, Corradetti G. Multimodal imaging: Implications for clinical practice. Retina Today 20191:1-4.  |
| 2. | Choudhry N, Duker JS, Freund KB, Kiss S, Querques G, Rosen R, et al. Classification and guidelines for widefield imaging: Recommendations from the international widefield imaging study group. Ophthalmol Retina 2019;3:843-9. |
| 3. | Tripathy K, Chawla R, Venkatesh P, Sharma YR, Vohra R. ultrawide field imaging in uveitic non-dilating pupils. J Ophthalmic Vis Res 2017;12:232-3. [ PUBMED] [Full text] |
| 4. | Tripathy K, Chawla R, Vohra R. Evaluation of the fundus in poorly dilating diabetic pupils using ultrawide field imaging. Clin Exp Optom 2017;100:735-6. |
[Figure 1], [Figure 2]
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