I have 6/18 in both eyes (uncorrected vision) and in the notification uncorrected vision allowance is 6/12 and my corrected vision is -1.0D spherical in both with falls right into limits of myopia. Am I eligible for NDA even though i didn't meet the requirements of uncorrected vision?

Being 6/18 in both eyes, you may be able to take the job based on the recruitment medical standards of the recruiting authority particularly, the jobs in the defence services or the government sector.

Most medical standards have certain amounts of uncorrected deficiencies in vision when vision corrected (glasses, contacts) is of the expected standard. The specific allowance depends upon a service and a post.

When the notification explains uncorrected vision allowance, then it probably means that everyone whose vision is worse than normal, but can be corrected to meet the specified requirement, can be afforded.

In order to be sure:

Ensure to read the accuracy of vision standards and allowance as stated in the official notification.

Upon permission, make sure that you attain a legal eye prescription displaying corrected eyesight within a limit.

In case of doubts, a certified medical officer or ophthalmologist is to be consulted to provide a report on eye examination.

You can really meet the bulk of the government job requirements because of the standard allowance in many of the requirements because you have 6/18 and 6/18, which is the uncorrected vision in both eyes. The majority of the notifications specify that the uncorrected vision might be 6/18 or even more, provided that the corrected vision (with glasses) is no less than 6/6.

Next steps:

Obtain a recent vision certificate (with proofs of your visions of uncorrected and corrected) by an optometrist.

include that certificate with your  application

By the time of the medical examination, you will have your glasses on to allow examiners confirm that corrected vision is okay.