We know that the lens in our eyes forms an inverted image on retina and brain reverses it to give the correct image. But when one wears specs the image would get reversed twice so we should see things inverted. Specs forms inverted image on lens -- lens again inverts it on retina -- brain again inverts it. Please explain.
closed as unclear what you're asking by user191954, Aaron Stevens, Jon Custer, Bill N, glS Dec 4 '18 at 9:42
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
When you have two lenses that are close to each other, to an approximation they function as a single lens whose diopter value is the sum of the individual lenses' diopters. Here, "close" means "at a distance small relative to the lenses' focal lengths". Only when lenses are "far apart" will they introduce new behavior (such as image inversion).
Typical (convex) eyeglass lenses have diopter values of 3 or less, which corresponds to a focal length of 1/3 meter or more, which is far longer than the distance between the glasses' lens and the lens in your eye. So, the lens doesn't add an inversion.
You can try this yourself with a (convex) eyeglass lens. Hold it close to your eye and you'll see the world slightly magnified, with the focus closer than usual. Now move the lens slowly away from your eye, and you'll see the image magnify further and further, until there will be a point where it's all a blur. Moving it further still, and you'll see the image come back, inverted. The distance where you only see a blur for distant objects is the focal length of the lens.