Asymmetry Analysis of Retinal Thickness 2011.11.30 초독회 Novel Software Strategy for Glaucoma Diagnosis Asymmetry Analysis of Retinal Thickness Ap. 박명희 / R2 김수아 Asrani S et al. Arch Ophthalmol 2011;129(9)

Introduction : constitute 40% of the retinal thickness of the macula Multilayered ganglion cells : constitute 40% of the retinal thickness of the macula : cell numbers are relatively constant with healthy eyes → Valuable structural measurement to be used for the diagnosis of glaucoma Glaucoma preferentially affects the three innermost retinal layers : the nerve fiber, ganglion cell, and inner plexiform layers, which contain, the axons, cell bodies, and dendrites of the ganglion cells. Asrani S et al. Arch Ophthalmol 2011;129(9)

Introduction Recent studies of RNFL measures in patients with early glaucoma found no differences in diagnostic accuracy, sensitivity and specificity between SD-OCT and TD–OCT. SD-OCT measurements over TD-OCT may be the relatively small area of the macula used for analysis. Segmentation of the retinal thickness to measure the GCC using the RT-Vue was no better at detecting glaucoma compared with TD-OCT. Asrani S et al. Arch Ophthalmol 2011;129(9)

Purpose The SD-OCT has been used to measure macular thickness in retinal diseases but it has not been commonly used for glaucoma. The authors report on the use of new, modified software to analyze macular thickness measurements for use in patients with glaucoma. Asrani S et al. Arch Ophthalmol 2011;129(9)

Method Retinal thickness measurements Using the Spectralis SD-OCT 61-lines in the central 20° area Eye-tracking capability ; reduction of artifact produced by microsaccades Displayed as a color-coded thickness map for an 8 x 8 grid centered on the foveal pit The grid is positioned symmetrically to the fovea-to-disc axis for each eye The area is then divided into small 3°x 3° square areas Mean retinal thickness of each small square is displayed The color scale has been modified to reveal retinal thickness differences of 10 to15 μm, permitting improved detection of small tissue Asrani S et al. Arch Ophthalmol 2011;129(9)

Method Asymmetry analysis OD vs OS asymmetry : 3°x 3° square area of one eye, the mean retinal thickness was compared with the value in the corresponding area of the other eye Hemisphere asymmetry : comparing each cell in the inf. hemisphere with the corresponding cell in the sup. hemisphere and displayed as an asymmetry map The asymmetry map : displayed as a gray scale depiction of difference in thickness from 0 to 30 μm. Asrani S et al. Arch Ophthalmol 2011;129(9)

CASE 1 : Preperimetric glaucoma F/46 VA : OD/OS 1.0/1.0 IOP : OD/OS 15/15 Pachymetry : OD/OS 579/579 μm Gonioscopy : nl. open angle CDR : OD/OS 0.75/0.6

CASE 1: PREPERIMETRIC GLAUCOMA

CASE 2 : Moderate glaucoma F/44 VA : OD/OS 1.0/1.0 IOP : OD/OS 24/31 Pachymetry : normal Gonioscopy : nl. open angle CDR : OD/OS 0.6/0.75

CASE 3 : Moderate glaucoma with a paracentral scotoma F/44 VA : OD/OS 1.0/1.0 IOP : OD/OS 32/24 Pachymetry : OD/OS 585/585 μm Gonioscopy : nl. open angle CDR : significant for asymmetric cupping OD larger, sloping cup

CASE 4 : Advanced glaucoma F/56 VA : OD/OS 1.0/0.4 IOP : OD/OS 19/21 (with medical therapy) Optic disc : OD sloping of the inferior rim OS significant inferior thinning

Comment The Stratus TD-OCT protocol uses 6 radial linear scans with 6 mm scan length, limiting the number of sampling lines. SD-OCT offers more flexible software for measurement and display. It is highly reproducible and provides high resolution of both the RNFL and retinal thickness. Detection of glaucoma can be easier by combining the diagnostic potential of RNFL thickness with the modified macular thickness map. Authors have demonstrated the ability of the macular thickness map and asymmetry map in 4 cases. These measurements may also be useful in patients with end-stage glaucoma in whom visual fields are almost completely extinguished. (In these cases, it may be impossible to monitor by using visual fields) Asrani S et al. Arch Ophthalmol 2011;129(9)

Limitation In cases of symmetrical loss between the eyes, as well as in cases in which there is symmetrical loss in both hemispheres of the same eye, the asymmetry plots will have minimal value. A normative database that incorporates age, sex, refractive status, and ethnicity will be required to use this technology fully ; such a database is being assembled. This strategy may be limited in patients with glaucoma who have coexisting retinal conditions, such as ERM, DME, AMD Asrani S et al. Arch Ophthalmol 2011;129(9)

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