Check if your Mac OS is recognizing the device: Plug in your device and check if the device is detecting it or not. If your Mac does not assign it a drive letter. It indicates that the hardware is corrupted. This is a alarm that you need an MAC Photo Recovery Software. If the device is recognized then you will be prompted to format the device please say no to it.
Stop using the corrupt device with immediate effect. If not done so then you may loose your older photos as the data may get overwritten and you will loose data forever.
Never try to format the device as on reformatting the device the data will get overwritten. I will add few more don't s to the list like
Don'ts
a) Don't try and open the device
b) Don't expose it to extreme temperature
c) Don't expose the device to strong magnetic fields
All these precautions will increase your chances of recovering the data.
A lot of photo recovery software are available nowadays. But make sure that the digital photo recovery software that you choose is compatible with your photo storage device. Make sure that the application you choose supports the operating system which you are using. Another important thing to notice is the file format, which file format does the photo recovery software support.
The most important decision after corruption of the photo storage device is the picture recovery software selection. Most of the freeware software will recover the photo but it may happen that the data gets corrupt by the time it gets recovered. I won't recommend you to go for such services.