Mounting media RI

Hello everyone. I have one question about one particular mounting media, Immuno Mount Epredia Immu-Mount:Histology and Cytology:Slide Mounting Media | Fisher Scientific, our user used to mount the sample. In the description, it mentioned "Refractive index: 1.495 ±0.002 (liquid); 1.586 ± 0.002 (dry)
". The RI after dry is higher than common mounting media we use such as Prolong Gold, 1.46. We are using 20x/0.75 objective to image a brain section of 15um thickness on a point scanner confocal. We see blurry nuclear stained with DAPI (also other channels as well) compared to previous sample mounted in 70% glycerol (RI of ~1.44). I suspect the higher RI contributed to the blurry image. Unfortunately, the air objective doesn’t have a correction collar for me to test. I’m wondering if this makes sense and if I miss something else that also contributes to the blurry image in this scenario. Thanks for your suggestion.

This sounds reasonable to me, but “blurry” is pretty subjective. Could you provide some numbers, such as the resolution in Z is “X” lower? I could see this difference in RI reducing the resolution by some percentage, like 20%, but if it is 2x or 3x worse than the issue may be somewhere else. I also think that the RI would make the largest difference in Z due to increased spherical aberration and X/Y should not be as affected.

Thanks @Hazen_Babcock for your help. I measured the ratio of standard deviation over mean intensity on those two images. The one with ImmunoMount (RI 1.59) has 0.787 while the image with 70% glycerol has 1.101. The imaged region are slightly different but both on hippocampus. Can I say it has a ~25% decrease in lateral focus? Thanks.