MyVisionTest News Archive
Jul 28, 2010
Tracking the progression of geographic atrophy
A new study finds that combined confocal scanning laser ophthalmoscopy (cSLO) and spectral-domain optical coherence tomography (SD-OCT) imaging provides unprecedented insight into dynamic microstructural changes of geographic atrophy (GA) enlargement that may help to better understand the pathogenesis of the disease.
The factors predisposing to the eventual development of geographic atrophy (GA) are still poorly understood. Natural history studies of GA revealed high-risk characteristics for disease progression, including the presence of soft drusen and hyperpigmentations as well as increased fundus autofluorescence (FAF) and specific abnormal patterns. In contrast to neovascular AMD, there is yet no therapy available for patients with GA.
Methods and Results
Forty-six eyes of 26 patients (median age, 77.9 years) with GA without evidence of active or previous neovascular disease at baseline were examined by simultaneous confocal scanning laser ophthalmoscopy (cSLO) and SD-OCT. Serial examinations with alignment of follow-up to baseline scans were performed over a median period of 12.2 months. Longitudinal SD-OCT variations were evaluated, including quantification of retinal thickness (RT) change and lateral spread of GA (LSGA) at a temporal, nasal, inferior, and superior GA border-section in each eye.
GA-enlargement was characterized by progressive loss of the outer hyperreflective SD-OCT bands and by thinning of the outer nuclear layer with subsequent approach of the outer plexiform layer toward Bruch's membrane. In the perilesional zone, various dynamic changes were recorded, including migration of hyperreflective material and changes in drusen height. At the borders, there was a median RT change of –14.09 µm/y. The median LSGA was 106.90 µm/y. Both parameters showed only moderate intraocular agreement and no statistical significant difference for one location.
Discussion and Conclusions
While previous studies using high-resolution imaging in GA were limited to cross-sectional analysis, this is, to the best of our knowledge, the first study to analyze the progression of GA secondary to AMD by high-resolution SD-OCT imaging. The identification of microstructural changes over time, including the advancing loss of the RPE and photoreceptor bands at the GA border or the subsequent apposition of the OPL with BM within the atrophic lesion, underscores the relevant information obtained by this imaging method. Previous nondetectable dynamic changes can be now monitored in the same person over time. Of note, these observations are made within a relatively short period (i.e., a few months).
In addition, this study demonstrates the advantages of simultaneous cSLO and SD-OCT imaging. This imaging technology allows accurate serial imaging of the same retinal location at different time points with the use of two independent mirrors and eye tracking software. Therefore, in addition to the description of relative changes, we were able to quantifiably determine the spread of GA and the change in retinal thickness. This was achieved by evaluating changes in the SD-OCT signal exactly at, and in relation to, the location of the GA border as defined at the baseline visit.
A reduction in retinal thickness is a hallmark of disease progression at the GA border that was both quantifiable and confined to loss of photoreceptor cell morphology. However, an increase in retinal thickness in 17 eyes that was related to confounders such as epiretinal membrane formation or marked collateral changes such as development of RPE elevations or sub-RPE deposits. Therefore, tracking of GA progression by changes in retinal thickness measurements alone should be interpreted with caution.
In conclusion, this longitudinal study provides insight into dynamic microstructural retinal changes in progressive GA by high-resolution in vivo imaging. The simultaneous application of SD-OCT and cSLO imaging in one instrument also allows for quantitative tracking of GA progression at specific retinal locations. This approach may be helpful for monitoring the natural course of the disease and for elucidating pathogenetic mechanisms. In particular, the identification of structural risk factors reflecting disease activity and future lateral spread of GA may be important for prognosis and visual function. Finally, the effects of new therapeutic agents aimed at slowing down GA progression may be evaluated at high resolution and in a three-dimensional fashion.
Read more...
Invest Ophthalmol Vis Sci. 2010 Aug;51(8):3846-52
Tags: dry AMD, OCT
A new study finds that combined confocal scanning laser ophthalmoscopy (cSLO) and spectral-domain optical coherence tomography (SD-OCT) imaging provides unprecedented insight into dynamic microstructural changes of geographic atrophy (GA) enlargement that may help to better understand the pathogenesis of the disease.The factors predisposing to the eventual development of geographic atrophy (GA) are still poorly understood. Natural history studies of GA revealed high-risk characteristics for disease progression, including the presence of soft drusen and hyperpigmentations as well as increased fundus autofluorescence (FAF) and specific abnormal patterns. In contrast to neovascular AMD, there is yet no therapy available for patients with GA.
Forty-six eyes of 26 patients (median age, 77.9 years) with GA without evidence of active or previous neovascular disease at baseline were examined by simultaneous confocal scanning laser ophthalmoscopy (cSLO) and SD-OCT. Serial examinations with alignment of follow-up to baseline scans were performed over a median period of 12.2 months. Longitudinal SD-OCT variations were evaluated, including quantification of retinal thickness (RT) change and lateral spread of GA (LSGA) at a temporal, nasal, inferior, and superior GA border-section in each eye.
GA-enlargement was characterized by progressive loss of the outer hyperreflective SD-OCT bands and by thinning of the outer nuclear layer with subsequent approach of the outer plexiform layer toward Bruch's membrane. In the perilesional zone, various dynamic changes were recorded, including migration of hyperreflective material and changes in drusen height. At the borders, there was a median RT change of –14.09 µm/y. The median LSGA was 106.90 µm/y. Both parameters showed only moderate intraocular agreement and no statistical significant difference for one location.
Discussion and Conclusions
While previous studies using high-resolution imaging in GA were limited to cross-sectional analysis, this is, to the best of our knowledge, the first study to analyze the progression of GA secondary to AMD by high-resolution SD-OCT imaging. The identification of microstructural changes over time, including the advancing loss of the RPE and photoreceptor bands at the GA border or the subsequent apposition of the OPL with BM within the atrophic lesion, underscores the relevant information obtained by this imaging method. Previous nondetectable dynamic changes can be now monitored in the same person over time. Of note, these observations are made within a relatively short period (i.e., a few months). In addition, this study demonstrates the advantages of simultaneous cSLO and SD-OCT imaging. This imaging technology allows accurate serial imaging of the same retinal location at different time points with the use of two independent mirrors and eye tracking software. Therefore, in addition to the description of relative changes, we were able to quantifiably determine the spread of GA and the change in retinal thickness. This was achieved by evaluating changes in the SD-OCT signal exactly at, and in relation to, the location of the GA border as defined at the baseline visit.
A reduction in retinal thickness is a hallmark of disease progression at the GA border that was both quantifiable and confined to loss of photoreceptor cell morphology. However, an increase in retinal thickness in 17 eyes that was related to confounders such as epiretinal membrane formation or marked collateral changes such as development of RPE elevations or sub-RPE deposits. Therefore, tracking of GA progression by changes in retinal thickness measurements alone should be interpreted with caution.In conclusion, this longitudinal study provides insight into dynamic microstructural retinal changes in progressive GA by high-resolution in vivo imaging. The simultaneous application of SD-OCT and cSLO imaging in one instrument also allows for quantitative tracking of GA progression at specific retinal locations. This approach may be helpful for monitoring the natural course of the disease and for elucidating pathogenetic mechanisms. In particular, the identification of structural risk factors reflecting disease activity and future lateral spread of GA may be important for prognosis and visual function. Finally, the effects of new therapeutic agents aimed at slowing down GA progression may be evaluated at high resolution and in a three-dimensional fashion.
Read more...
Invest Ophthalmol Vis Sci. 2010 Aug;51(8):3846-52
