24 July 2014
Posted in Pearls in Ophthalmology
By Brooke Strickland
In this study, researchers wanted to measure aniseikonia in patients going through vitrectomy for epiretinal membrane (ERM) and to research what the relationship was between aniseikonia and the foveal microstructure by spectral-domain (SD) optical coherence tomography (OCT). The study looked at 44 patients (44 eyes) that underwent vitrectomy for idiopathic ERM.
Researchers gathered information on visual acuity and aniseikonia using the New Aniseikonia Test and SD-OCT prior to surgery, then at 3 and 6 month intervals after surgery. They also used the status of the photoreceptor inner segment/outer segment junction, external limiting membrane, and cone outer segment tips. On the basis of the OCT image that they got, researchers divided the 1.0×1.0-mm area centered on the fovea into 9 sections at 0.25-mm intervals and quantified the following parameters using an image-processing program: central foveal thickness and mean thickness of the ganglion cell layer, inner nuclear layer (INL), and outer retinal layer (outer nuclear layer + outer plexiform layer). The goal was to find the amount of aniseikonia at 6 months post-surgery.
Results showed that 89% of the patients examined had macropsia, 2% had micropsia, and 9% had no aniseikonia pre-operatively. The average preoperative aniseikonia was 6.2%±4.5%. For patients with ERM, vitrectomy helped improve visual accuracy, but it didn’t change the aniseikonia numbers. Multiple regression analysis showed that preoperative aniseikonia at 6 months was related to preoperative INL thickness, whereas postoperative aniseikonia at 6 months was linked with postoperative INL thickness at 6 months. Preoperative INL thickness was found to be of significant prognostic value for postoperative aniseikonia at 6 months. (1)
What to take away from the study: A high percentage of patients with ERM also had macropsia, but aniseikonia did not lessen after surgery. In addition, aniseikonia numbers were also linked to inner nuclear layer thickness.
1. Okamoto, Fumiki, MD, Sugiura, Yoshimi, MD, Okamoto, Yoshifumi, MD, Hiraoka, Takahiro, MD, Oshika, Tetsuro, MD. “Time Course of Changes in Aniseikonia and Foveal Microstructure after Vitrectomy for Epiretinal Membrane.” Ophthalmology: Journal of the AAO. Manuscript no. 2014-409. Published online July 7, 2014. Accessed July 16, 2014. http://www.aaojournal.org/article/S0161-6420%2814%2900452-7/abstract
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