My first idea was the same as in Izhaki's answer, but later I thought of this, that seems to fulfill your goal and to reduce (at least a bit) the need of user interaction without drawbacks.

^{download bmml source – Wireframes created with Balsamiq Mockups}

I think in this case it will be better to set the first radio button as default, because the "explicit" action needed is the 2nd, and setting the first one as default will save 1 click and probably avoid the most of the chances of the "what if the users decides to just click the first radio button?" situation. Btw, IMO that situation would be the same as the user leaving all checkboxes empty (in a design without radio buttons), a later validation will be needed anyway. I think several answers are mainly concentrating in user behavior (based in the presented UI) and losing some attention on questioning the visual design which plays a huge role in the UX changing/inducing users' perception and behavior when using the application.

The key point

For me the most important thing here is making the dichotomy between "None of the above" and any other option as visually explicit as possible.
One way of doing that, is with radio buttons as in the first mockup.

KISS

This is a simpler approach, that also makes that differentiation clear:

^{download bmml source}

Alright, but then why not using this last approach?

Recently I saw this question about accessibility which made me aware of things like contrast levels in inputs. The "simpler" approach will not support that necessity unless you start placing info messages everywhere or assuming that the users understand/is comfortable with the app behavior.

So, particularly in this case, if the form contains an option like "Eyesight conditions", wouldn't it be appropriate (and consistent) to take in account the contrast issue?

I recommend trying these designs with real users, they are the ones that will have the last word on what is better.

The key point

The most important thing to tackle here is making the dichotomy between "None of the above" and any other option as visually explicit as possible.

Option 1

^{download bmml source – Wireframes created with Balsamiq Mockups}

I think in this case it will be better to set the first radio button as default, because the "explicit" action needed is the 2nd, and setting the first one as default will save 1 click and probably avoid the most of the chances of the "what if the users decides to just click the first radio button?" situation. Btw, IMO that situation would be the same as the user leaving all checkboxes empty (in a design without radio buttons), a later validation will be needed anyway. I think several answers are mainly concentrating in user behavior (based in the presented UI) and losing some attention on questioning the visual design which plays a huge role in the UX changing/inducing users' perception and behavior when using the application.

Option 2 (KISS)

This is a simpler approach, that also makes that differentiation clear:

^{download bmml source}

Alright, but then why not using this last approach?

Recently I saw this question about accessibility which made me aware of things like contrast levels in inputs. The "simpler" approach will not support that necessity unless you start placing info messages everywhere or assuming that the users understand/is comfortable with the app behavior.

When legal/health stuff is involved, I'd prefer to play defensive, making users select options that precisely states their input, even if it envoles a bit of extra complexity.

As always, I recommend trying these designs with real users, they are the ones that will have the last word on what emerges as the better solution.

My first idea was the same as in Izhaki's answer, but later I thought of this, that seems to fulfill your goal and to reduce (at least a bit) the need of user interaction without drawbacks.

(EDIT: thanks to @dennislees for improving the color design for contrast. If it goes well with the rest of your UI, IMO this will improve the consistency of this approach)

^{download bmml source – Wireframes created with Balsamiq Mockups}

Edit

I think in this case it will be better to set the first radio button as default, because the "explicit" action needed is the 2nd, and setting the first one as default will save 1 click and probably avoid the most of the chances of the "what if the users decides to just click the first radio button?" situation. Btw, IMO that situation would be the same as the user leaving all checkboxes empty (in a design without radio buttons), a later validation will be needed anyway. I think several answers are mainly concentrating in user behavior (based in the presented UI) and losing some attention on questioning the visual design which plays a huge role in the UX changing/inducing users' perception and behavior when using the application.

The key point

For me the most important thing here is making the dichotomy between "None of the above" and any other option as visually explicit as possible.
One way of doing that, is with radio buttons as in the first mockup.

KISS

This is a simpler approach, that also makes that differentiation clear:

^{download bmml source}

Alright, but then why not using this last approach?

Recently I saw this question about accessibility which made me aware of things like contrast levels in inputs. The "simpler" approach will not support that necessity unless you start placing info messages everywhere or assuming that the users understand/is comfortable with the app behavior.

So, particularly in this case, if the form contains an option like "Eyesight conditions", wouldn't it be appropriate (and consistent) to take in account the contrast issue?

I recommend trying these designs with real users, they are the ones that will have the last word on what is better.

My first idea was the same as in Izhaki's answer, but later I thought of this, that seems to fulfill your goal and to reduce (at least a bit) the need of user interaction without drawbacks.

^{download bmml source – Wireframes created with Balsamiq Mockups}

I think in this case it will be better to set the first radio button as default, because the "explicit" action needed is the 2nd, and setting the first one as default will save 1 click and probably avoid the most of the chances of the "what if the users decides to just click the first radio button?" situation. Btw, IMO that situation would be the same as the user leaving all checkboxes empty (in a design without radio buttons), a later validation will be needed anyway. I think several answers are mainly concentrating in user behavior (based in the presented UI) and losing some attention on questioning the visual design which plays a huge role in the UX changing/inducing users' perception and behavior when using the application.

The key point

For me the most important thing here is making the dichotomy between "None of the above" and any other option as visually explicit as possible.
One way of doing that, is with radio buttons as in the first mockup.

KISS

This is a simpler approach, that also makes that differentiation clear:

^{download bmml source}

Alright, but then why not using this last approach?

Recently I saw this question about accessibility which made me aware of things like contrast levels in inputs. The "simpler" approach will not support that necessity unless you start placing info messages everywhere or assuming that the users understand/is comfortable with the app behavior.

So, particularly in this case, if the form contains an option like "Eyesight conditions", wouldn't it be appropriate (and consistent) to take in account the contrast issue?

I recommend trying these designs with real users, they are the ones that will have the last word on what is better.

My first idea was the same as in Izhaki's answer, but later I thought of this, that seems to fulfill your goal and to reduce (at least a bit) the need of user interaction without drawbacks.

(EDIT: thanks to @dennislees for improving the color design for constrast. If it goes well with the rest of your UI, IMO this will improve the consistency of this approach  )

^{download bmml source – Wireframes created with Balsamiq Mockups}

Edit

I think in this case it will be better to set the first radio button as default, because the "explicit" action needed is the 2nd, and setting the first one as default will save 1 click and probably avoid the most of the chances of the "what if the users decides to just click the first radio button?" situation. Btw, IMO that situation would be the same as the user leaving all checkboxes empty (in a design without radio buttons), a later validation will be needed anyway. I think several answers are mainly concentrating in user behavior (based in the presented UI) and losing some attention on questioning the visual design which plays a huge role in the UX changing/inducing users' perception and behavior when using the application.

The key point

For me the most important thing here is making the dichotomy between "None of the above" and any other option as visually explicit as possible.
One way of doing that, is with radio buttons as in the first mockup.

KISS

This is a simpler approach, that also makes that differentiation clear:
(btw, Keavon posted a very similar design with the same idea while I was starting to edit my answer)

^{download bmml source}

Alright, but then why not using this last approach?

Recently I saw this question about accessibility which made me aware of things like contrast levels in inputs. The "simpler" approach will not support that necessity unless you start placing info messages everywhere or assuming that the users understand/is confortable with the app behaviour.

So, particularly in this case, if the form contains an option like "Eyesight conditions", wouldn't it be appropriate (and consistent) to take in account the constrast issue?

My first idea was the same as in Izhaki's answer, but later I thought of this, that seems to fulfill your goal and to reduce (at least a bit) the need of user interaction without drawbacks.

(EDIT: thanks to @dennislees for improving the color design for contrast. If it goes well with the rest of your UI, IMO this will improve the consistency of this approach)

^{download bmml source – Wireframes created with Balsamiq Mockups}

Edit

I think in this case it will be better to set the first radio button as default, because the "explicit" action needed is the 2nd, and setting the first one as default will save 1 click and probably avoid the most of the chances of the "what if the users decides to just click the first radio button?" situation. Btw, IMO that situation would be the same as the user leaving all checkboxes empty (in a design without radio buttons), a later validation will be needed anyway. I think several answers are mainly concentrating in user behavior (based in the presented UI) and losing some attention on questioning the visual design which plays a huge role in the UX changing/inducing users' perception and behavior when using the application.

The key point

For me the most important thing here is making the dichotomy between "None of the above" and any other option as visually explicit as possible.
One way of doing that, is with radio buttons as in the first mockup.

KISS

This is a simpler approach, that also makes that differentiation clear:

^{download bmml source}

Alright, but then why not using this last approach?

Recently I saw this question about accessibility which made me aware of things like contrast levels in inputs. The "simpler" approach will not support that necessity unless you start placing info messages everywhere or assuming that the users understand/is comfortable with the app behavior.

So, particularly in this case, if the form contains an option like "Eyesight conditions", wouldn't it be appropriate (and consistent) to take in account the contrast issue?

I recommend trying these designs with real users, they are the ones that will have the last word on what is better.