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D. Cabrera Fernandez, N. Sekhon, S. Ranganathan, H. M. Salinas, A. Bhorade, C. A. Puliafito, S. Yoo, D. Budenz; The Effect of Cataract Extraction and Pseudophakia on the Measurement of Ganglion Cell Layer and Inner Plexiform Layer Thickness in Patients With and Without Primary Open Angle Glaucoma (POAG) Using OCT. Invest. Ophthalmol. Vis. Sci. 2007;48(13):110. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effects of phacoemulsification and pseudophakia on the ganglion cell layer and inner plexiform (GCL+IPL) thickness measurements by Stratus OCT III.
Thirteen patients who underwent phacoemulsification with lens implantation were analyzed. Eight patients were classified as glaucoma suspects. Fourteen normal eyes were used as controls. OCT was examined preoperatively and 4 weeks postoperatively. Macular thickness of the GCL+IPL, RNFL, INL, OPL and ONL was measured on horizontal and vertical OCT scans after automatic segmentation using a custom software program. Relative percentual difference in preoperative and postoperative measurements was calculated. The cataract’s effect on SNR was also evaluated. The results were analyzed using Wilcoxon matched pairs signed rank test (two-sided) and correlation analyses. For all analyses, p≤0.05 was considered to be statistically significant.
Increases in the GCL+IPL thickness after surgery were present in 92.30% of patients. A significant correlation was found between the GCL+IPL thickness before and after surgery (r=0.74, p=0.004 (vertical scans) and r=0.63, p=0.01 (horizontal scans)). No correlation was found for the remaining layers. The mean relative difference of GCL+IPL thickness before and after surgery in the population was 13.55% (vertical scans), and 14.12% (horizontal scans). The mean GCL+IPL thickness was 60.19 ± 9.10 microns before vs. 67.14 ± 12.30 microns after cataract surgery (p=0.013, vertical scans).The mean GCL+IPL thickness was 69.94 ± 11.44 microns before vs. 75.54 ± 11.27 microns after cataract surgery (p=0.026, horizontal scans ). The SNR showed a statistically significant increase after cataract removal (p=0.0002). Before cataract surgery, the GCL+IPL complex was thinner than in control eyes. This thinning effect was more noticeable for POAG suspects (12.23% vs. 2.26% thinning obtained for patients without retinal pathology).
This study shows that significant changes occur in the thickness measurements of the GCL+IPL complex for POAG cases after cataract removal. SNR is enhanced after cataract surgery. Since a cloudy lens creates a distortion in the optical path difference of the light beam, OCT measurements might need some adjustments in order to properly quantify and diagnose glaucoma suspects in the presence of media opacities.
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