Create a new document, 1000x1000 pixels, no background.
Create a new layer. Using the elliptical marquee tool, make a perfect round selection and fill it with white. Position it like in my example:
With the selection still active, go to Select>Modify>Contract. I contracted with 10 pixels then I deleted it.
Now using the Linear gradient tool, I applied a Black-to-white gradient. You can see the example:
Now make a new layer. On it, make a circular selection just inside the gradient circle and repeat the procedure above, but this time change gradient to reverse. Your object should be like this:
Now let's make the handle. On a new layer using the rectangular marquee tool, make it and position it like in the example:
Double click on the handle layer to bring up the Layer style dialogue. Mark the Gradient overlay and choose a gradient like in the example. Your image should look like this:
Hit CTRL+T (Command+T on Mac) to enter free transform mode and choose "Perspective". From the upper right corner, drag it a little to make that portion bigger. Your handle should look like this: Position the handle layer under the loupe layer.
Select all three layers, right click and choose Group into new smart object. We finished the loupe. Now let's get to the second part.
Open the image where you want to apply the loupe effect. Here is mine:
Drag the loupe in your image (now it is a smart object). Stretch it and rotate it until you are satisfied and the loupe covers the area you want.
Make a circular selection just inside the loupe, right click on the selection and choose Layer via copy.
Now CTRL+click on the newly created layer to bring back the selection. Go to Filter>Distort> Spherize and choose 100. Now Go again to spherize and reapply the filter but only with a 50 value.
Put the layer with the loupe in Hard Light mode. This is the final image:
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