As millions of Brits face rising living costs and energy bills, it's understandable why many might delay visiting the opticians. Although necessary, sight tests often cost anywherebetween £20 and £77, depending on the provider.

However, you might be surprised to learn that some people can access free eye tests and optical vouchers through the NHS. This is particularly true for people of certain ages and those receiving variousbenefitsfrom the Department for Work and Pensions (DWP).

Below, the Mirror has explored who exactly is eligible for this and what action you can take. If you've paid for an eye test but later find you're eligible for free appointments, you might also be entitled to a refund.

According tothe NHS, there are 10 groups of people who automatically qualify for free NHS sight tests. This specifically includes the following:

• People under 16
• People aged 16, 17 or 18 and in full-time education (this includes being taught full-time at a school, college, university or at home)
• People aged 60 or over
• People who are registered as partially sighted or blind
• People who have been diagnosed with diabetes or glaucoma
• People who are 40 or over and your mother, father, sibling or child has been diagnosed with glaucoma
• People who have been advised by an eye doctor (ophthalmologist) that you're at risk of glaucoma
• Prisoners on leave from prison
• People who are eligible for an NHS complex lens voucher – your optician can advise you about your entitlement
• People entitled to or named on a valid NHS certificate for full help with health costs (HC2)

Additionally, you might qualify if you or your partner is receiving certain government benefits. Dependants under 20 years old may benefit from this, too, provided you are claiming:

• Income Support
• Income-based Employment and Support Allowance
• Income-based Jobseeker's Allowance
• Pension Credit Guarantee Credit

• Universal Credit (provided you meet the criteria)

Further advice from the NHS adds: "People named on an NHS certificate for partial help with health costs (HC3) may also get help with the cost of a private sight test."

Optical vouchers are documents issued by an optician following an eye exam. They offer a specified amount of money to assist eligible people with the cost of glasses or contact lenses.

Generally, you are entitled to an optical voucher if one of the following applies:

• You are a prisoner on leave from prison
• You are eligible for an NHS complex lens voucher – an optician can advise you about your entitlement
• You are under 16
• You are entitled to or named on a valid NHS certificate for full help with health costs (HC2)
• You are 16, 17 or 18 and in full-time education (this includes being taught full-time at a school, college, university or at home)

Similarly, if you or a partner receives specific benefits, you may also be entitled to an NHS optical voucher. The benefits encompassed within this are:

• Income Support
• Income-based Employment and Support Allowance
• Income-based Jobseeker's Allowance
• Pension Credit Guarantee Credit
• Universal Credit (provided you meet the criteria)

READ MORE: NHS dental appointments are free for specific people - full list explained

If you believe you qualify for free NHS sight tests, glasses or contact lenses, visit the NHS Business Services Authority (NHSBSA) website to check. The site offers a free eligibility test that typically takes about three minutes to complete. If eligible, it will guide you through the next steps to claim assistance.

Anyone who thinks they have paid wrongly for sight tests might be eligible for a refund. Guidance from the NHS adds: "If you paid for a sight test but think you may qualify for an NHS-funded sight test, or you're about to have a test and you're not sure if you qualify, ask the optometrist for a receipt that shows you paid for the test and the date of payment.

"You'll need to download, print and return an HC5(O) refund form along with your original receipt. The form tells you where to send it."

For more information, head to the NHS website.