How to find prescription lead glasses that work for you

Supplier: Deutsch Medical Pty Ltd
26 October, 2020

This article is guiding healthcare professionals on how to select prescription lead glasses that provide comfortable radiation protection and clear vision during diagnostic imaging procedures.

1. Understand your script

Your script is usually measured and prepared by an Optometrist or Ophthalmologist. It includes information (numbers, symbols and letters) to make lenses to correct vision problems that you may have.

Spectacle prescription for prescription lead glasses

Sphere (SPH)

  • The symbols + or – in front of the numbers indicate whether you are farsighted (+) or nearsighted (-).
  • The numbers (called dioptres), usually displayed with two decimal places, specify how strong your prescription leaded lenses require to be. The greater the number, e.g. 5.00, the stronger the prescription leaded lenses have to be and the higher the curve of the lens is required. A higher prescription can limit your option of available frames that can be fitted with prescription leaded lenses.

Cylinder (CYL)

  • The correction of astigmatism, which is basically a distortion of your vision, is represented by cylinder. The visual distortion is caused by a cornea that is irregularly shaped.
  • The numbers, generally noted with two decimal places as well, specifies by how much the power of the eye must be increased or decreased in one axis only.
  • A small value, e.g. 0.50, indicates that your eyes are not quite round and a higher number like 3.00 means your eyes are quite oval.

Axis

  • The axis specifies the direction of the astigmatism or the angle of the CYL power, which is always quoted in degrees from 0 to 180 degrees.
  • This is important for the optical lab to know. It specifies how to position your prescription leaded lenses if you do have a Cylinder value (astigmatism) listed in your script.
  • If the Cylinder section is empty, there will also be no information in the Axis field.

Prism

  • This prescription section is telling you that your eyes do not work well together. Prism lenses offer the correction required to help prevent double vision or headaches.

Pupillary Distance (PD)

  • The Pupillary Distance (PD) is the distance between both your pupils and is measured in millimetres. This will typically be 55mm to 68 mm.
  • All prescriptions require a PD. However, this information is not always included within your script which is lacking key information.

Addition (Add)

  • Add measures a correction that you may require for reading. It is used in bifocal glasses and/ or reading glasses. It represents the additional power over the distance prescription.

 

2. Determine your required prescription (vision) type

Most manufacturers of radiation protection eyewear offer frames that can be fitted with prescription leaded lenses allowing for following three prescription types.

Single Vision (SV)

single vision lenses

SV leaded lenses only offer one type of vision correction, either for being farsighted (+) or nearsighted (-). This is the most common prescription type.

When you are farsighted, you may need reading prescription lead glasses because you cannot see things that are close to your eyes. These glasses are used to see close things, e.g. reading the information in front of a computer screen. 

When you are nearsighted, you may require distance prescription lead glasses because you cannot view things that are further away. These glasses are used to see distances clearer.

Bifocal Vision (BF)

bifocal vision lenses

BF leaded lenses provide both near and distance vision. These lenses are split into two sections to correct near (e.g. reading) and far visual needs (e.g. driving a car).

Bifocals help you get far and near vision only, and will generate image jumps when you look near after you see distance.

Progressive Vision (PG)

progressive vision lenses

PG leaded lenses provide three levels of vision in one: distance, intermediate and near, allowing to do close-up work, middle-distance work or distance viewing without needing to change your glasses.

With a PG lens you will get continuous vision at distance, intermediated, and near focal ranges with no image jumps or lines. This prescription type is more expensive than bifocals but it may be worth the investment.

3. Research lead glasses frames that suit your prescription

Now you have all the information available to move on to the next step in the process: selecting the most suitable lead glasses frame for your prescription lead glasses.

Your prescription determines which frame will be most appropriate for you as there are some limitations to the script which can be made with leaded glass. For instance, wraparound (curved) frames only allow for a light prescription (sphere limit +/-3). Frames that can be equipped with the majority of prescription leaded lenses are the ones that have a flat front.

(a) Find out about prescription limits for lead glasses

Companies generally display the prescription limits for the lead glasses on their website or in other marketing materials such as catalogues, leaflets etc. Some offer comparison charts to get a quick overview of options. However, the provided information usually only specifies the prescription limits in relation to spheres and not necessarily cylinders. So, if you have an astigmatism (usually a value listed in the cylinder section of your script), you may want to double-check with the company directly if the prescription lead glasses will accommodate for this.

 

(b) Choose a pair of lead glasses with the lowest possible weight

When choosing a lead glasses frame, it is important to know that prescription lead glasses can often be slightly or significantly heavier than non-prescription lead glasses. This is the case especially for bifocal and progressive lead glasses as the lenses are laminated and thicker as a consequence. The higher your prescription is, the thicker the leaded lenses will be. As every script is unique, usually only an estimated weight range can be given which is usually between an additional weight of 5 to 20grams. For instance, a pair of non-prescription lead glasses (leaded lenses and frame) weighs 65grams, the final approximate weight of your prescription lead glasses (prescription leaded lenses and frame) can weigh approximately 70 to 85grams. The weight information of non-prescription lead glasses should be displayed on the company’s product pages online as this can impact the wearer’s comfort.

If your script has a sphere of higher than +/-8, usually “Fitover” lead glasses, which fit over your standard prescription eyewear, are the better choice for two reasons:

1) Prescription leaded lenses usually cannot be manufactured past this limit. 
2) The weight of the prescription leaded lenses becomes so significant that the lead glasses will be uncomfortable to wear.

As a guide, fitover lead glasses weigh approximately 75 to 100 grams.

 

c) Determine the size of lead glasses frame that will fit your face shape

Companies usually recommend on their websites what pair of lead glasses suits what type of face shape; small, medium, large, or extra large. However, this can sometimes be hard to gauge by simply looking at the product photos using a size description.

Check if the product pages include measurements about the lead glasses frames, such as frame width, bridge size, length of temple arms, lens width and height. If that’s the case, you are most likely able to compare the provided frame measurements with your standard prescription lead glasses to gauge whether or not the lead glasses frame will fit your face shape.

Frame measurements for lead glasses
Copyright: Deutsch Medical Pty Ltd

 

d) Find out about possible add-on’s to increase your comfort

Let’s be honest, lead glasses are not the most comfortable pair of glasses to wear. But they are a necessity to protect your eyes from the harmful effects of radiation during diagnostic procedures. Different manufacturers may offer all or a selection of the following lens coatings as well as add-on’s for your prescription lead glasses:

  • Side Shields (if not already included) to provide lateral radiation protection for your eyes.
  • Custom-engraving of name or phone numbers on temple arms
  • Anti-fog coating (usually a permanent lens coating) to minimise fogging.
  • Anti-reflective coating (usually a permanent lens coating) to reduce glare and lens reflections.

 

4. Trial the selected lead glasses to experience actual fit and weight

Once you have determined which lead glasses will suit your script best based on your research (prescription limits, weight indication, face shapes, frame measurements, possible add-on’s) it’s time to confirm that the lead glasses of your choice are comfortable to wear and fit your properly.

Ask companies who sell radiation protection eyewear if they offer lead glasses trials that let you test them for a period of time for the following three reasons:

The lead glasses provide maximum radiation protection for your eyes: lead glasses that fit you properly, provide higher radiation protection.

  • Ensure the nose piece of the lead glasses fits securely and comfortably on your nose.
  • The frame of the lead glasses should fit closely to the side of your head which will also allow the glasses to stay on during medical procedures.

The lead glasses are comfortable to wear

  • Manage your expectations and experience the weight of the non-prescription trial leaded glasses as scripted lead glasses can add a little bit more weight, depending on your individual script.
  • If they already feel too heavy and too uncomfortable to wear, you won’t feel happy with final prescription leaded lenses (refer to section 3 b)

Ensure you are happy with your choice & investment

  • Prescription lead glasses are not off-the-shelf glasses. They are manufactured according to your individual script, meaning you will have less options to return them unless they are faulty.
  • Some prescription lead glasses can be pricy, so you want to make sure you have invested in the right pair of prescription lead glasses that you will actually wear to protect your eyes from radiation.

If companies do not offer product trials, research as much information about the lead glasses as possible. You may find the information online and/or request further details especially about:

      • The weight of the non-scripted lead glasses.
      • What face shapes the lead glasses fit best, e.g. small, medium, large, x-large
      • Detailed measurements of the lead glasses frames; such as frame width,  lens width and height, bridge size, and length of temple arms.

However, nothing beats a trial to get the real experience of the radiation protection eyewear.

 

5. Double-check that your script includes all details required for your prescription order

Many scripts do not always include all the necessary information that is needed to manufacture your prescription lead glasses. It is quite common that the measurement of your pupillary distance is missing on your script. However, the PD is an essential measurement to make any prescription lead glasses. You may have to go back to your optometrist or call them to get your PD. You are the owner of your script and the optometrist is obliged to supply further details on request.

An overview of the minimum required information for each prescription type is listed below:

For Single Vision

      • Pupillary Distance
      • Sphere (either + or -)
      • Cylinder (only if a correction of astigmatism is required)
      • Axis (only if cylinder is listed)

For Bifocal Vision

      • Pupillary Distance
      • Sphere (+ and -)
      • Cylinder (only if a correction of astigmatism is required)
      • Axis (only if cylinder is listed)
      • Segment height (from the bottom of the lens in your frame to the top line of the lined bifocal). This is specific to the frame you choose and your eyes.
      • Add (if required)

Progressive vision

      • Pupillary Distance
      • Sphere
      • Cylinder (only if a correction of astigmatism is required)
      • Axis (only if cylinder is listed)
      • Segment height (from the bottom of the lens in your frame to the beginning of the progressive addition on a progressive lens). This is specific to the frame you choose and your eyes.
      • Add (if required)

The difference between bifocal and progressive lenses

Difference between bifocal and progressive prescription lenses
Source: https://eyewearinsight.com/links/How_to_Measure_Segment_Height, on 26/10/2020

 

What can you do if the segment height is not provided in your script?

  • The best option is to go back to your optometrist with the actual lead glasses frame (that you hopefully have been able to get as part of the product trial) of your choice and get the segment height measured either for bifocal or progressive vision. This is the safest procedure as an optometrist is less likely to make any errors as they are equipped with the tools to take the correct measurements. Also bear in mind that taking measurements on your own, may not be covered by the manufacturer's warranty.
  • Alternatively, if you do not have the lead glasses frame on hand, you may take your standard prescription glasses that you currently own to the optometrist as you may have chosen a pair of lead glasses that is very similar to current prescription frame
  • If you do not supply your segment height with your order of prescription lead glasses, the manufacturer may apply the standard segment height which may compromise your vision.

 

6. Finally - place your order attaching your script provided by your optometrist

Now having done your due diligence, you can submit your prescription lead glasses order along with your script. All the information that is required for your order should be written on your script. This is important for warranty purposes and in case your prescription order comes back with incorrect prescription leaded lenses. Following these recommended steps will assist you in receiving comfortable prescription lead glasses that provide a clear vision and protect your eyes from radiation.