Single vision lenses are designed to aid one focal distance. The majority of single vision lenses are designed to make objects in the distance appear clearer. However, eye doctors will often write a prescription for single vision lenses that are used only as reading glasses. In such cases, the glasses prescription will indicate the Rx is for near tasks only.

Typically, if distance single vision lenses are worn by patients less than 40 years old, vision will be clear at all distances. If single vision glasses contain a distance prescription and are worn by patients over 40 years old, the wearer may experience blur when viewing objects inside of arm’s length.

New single vision prescriptions often create a feeling of peripheral distortion and an unusual feeling when quickly looking off center. Typically, this phenomenon goes away after about 3 days of full-time wear.

Adjustment times can be longer for patients with large amounts of astigmatism, patients that have waited longer than 2.5 years to update their Rx, and patients that have large increases in farsighted power. A good rule of thumb is to give yourself at least 3 days to adjust to a new pair of glasses for every year in which you haven’t updated your Rx. This means if you haven’t gotten a new pair of glasses in 8 years, it may take your brain up to 24 days before your new prescription feels 100% normal and not disorienting. This adjustment occurs due to a higher order neurological adaptation. Updating your Rx at least every 2.5 years can lessen this adjustment period.

Lined bifocal lenses have a visible reading portion in the lower nasal corner of the lens. Lined bifocals are designed to aid two focal distances. Most commonly, the prescription is written to have the top portion of the glasses sharpen the distance (everything from arm’s length and beyond) and the lower bifocal segment is set to sharpen the focus on objects 16-18 inches away.

Lined bifocals do not provide crisp vision at arm’s length, thus resulting in a blur zone that exists about 20-34 inches from the wearer’s eyes. This blurry intermediate zone becomes more noticeable as you age. Usually this intermediate blur is not overly noticeable in a patient’s early 40’s, but becomes more problematic after mid to late 40’s. When this occurs, patients often benefit from no-line progressive lenses or custom lined bifocal lenses specifically designed as computer glasses. (If your doctor writes you a prescription for lined bifocal computer glasses the top portion of the lens will be for viewing the computer at 24-36 inches and the lower lined bifocal portion will be used for viewing objects at 16-18 inches).

It is common for lined bifocal wearers to experience an adjustment period with their new Rx. Stepping over stairs or curbs can be disorienting. When going from distance to near viewing, a jump phenomenon may also be noticed. Most wearers adjust to this after 3-4 days of full time wear.

Patients who wait too long to update their bifocal prescriptions often develop the habit of holding near objects further away to help them see small print. When such patients receive their new bifocal glasses, they will need to re-adjust to the proper and more appropriate focal length of 16-18 inches. This adjustment may take several days.

Adjustment times can be longer for patients with large amounts of astigmatism, patients that have waited longer than 2.5 years to update their Rx, and patients that have large increases in their bifocal power. A good rule of thumb is to give yourself at least 3 days to adjust to a new pair of glasses for every year in which you haven’t updated your Rx. This means if you haven’t gotten a new pair of glasses in 8 years, it may take your brain up to 24 days before your new prescription feels 100% normal and not disorienting. This adjustment occurs due to a higher order neurological adaptation. Updating your Rx at least every 2.5 years can lessen this adjustment period.

No-line progressive lenses have a gradual and seamless focal distance change as you progress down the lens. The top portion of the lens is for distance viewing (arm’s length and beyond). Slightly below center, a no-line progressive lens has a small intermediate zone designed to aid intermediate viewing at 24-36 inches away. In the above picture, this is designated by the red zone. This zone is helpful for computer and car dashboard viewing. As you continue down the lens, you encounter the near zone. This is represented by the blue zone in the above picture. Most doctors set the near reading zone to focus on objects that are 16-18 inches away.

All no-line progressive lenses have a blur circle inherent in the optics of the lens. In higher quality lenses (like Essilor’s Varilux lenses), this zone is forced to the lower outside corner of each lens. This blur circle becomes slightly larger as bifocal strength is increased.

It takes new no-line progressive lens wearers about 7 days of full time wear to adjust to their first lens. Every time a progressive no-line bifocal wearer updates their prescription there will also be an additional adjustment period lasting about 3 to 4 days. New progressive no-line lens wearers may notice stepping over stairs or curbs can be initially disorienting. Most wearers adapt to this phenomenon (7 days for new wearers and 3 days for established wearers).

Patients who wait too long to update their no-line progressive prescriptions often develop the habit of holding near objects further away to help them see small print. When such patients receive their new no-line progressive glasses they will need to re-adjust to the proper and more appropriate focal length of a 24-36 inches for the intermediate zone and 16-18 inches for the lower near zone. This adjustment may also take several days.

Adjustment times can be longer for patients with large amounts of astigmatism, patients that have waited longer than 2.5 years to update their Rx, and patients that have large increases in their bifocal power. A good rule of thumb is to give yourself at least 3 days to adjust to every new pair of glasses for every year in which you haven’t updated your Rx. This means if you haven’t gotten a new pair of glasses in 8 years, it may take your brain up to 24 days before your new prescription feels 100% normal and not disorienting. This adjustment occurs due to a higher order neurological adaptation. Updating your Rx at least every 2.5 years can lessen this adjustment period.

Be Aware: Cheaper, lower quality lenses cannot copy the better copyright owned designs of more effective lenses. This is why cheaper progressive lenses have larger blur circles and greater areas of distortion. Choosing a lower quality no-line progressive lens often means a sacrifice in quality that results in more peripheral distortion, a smaller reading zone, and a very difficult adjustment period.