A devastating and difficult to treat eye infection. Contact lens users are believed to be more susceptible to AK than other people, particularly when they do not follow proper lens hygiene protocols. Most contact lens solutions do not eradicate acanthamoeba even during overnight soaking.

The process of putting a saline-filled scleral lens on the eye.

Scleral lens users commonly call this lens “insertion”, but the term “application” has been formally adopted as it is more technically accurate.

Ingredients that are added to a solution, typically to balance the pH.

The most common buffers for preservative free saline solutions are borate buffers (boric acid and sodium borate). These are used in Purilens Plus and Scleralfil brands.

There are also phosphate buffers (used in Nutrifill) and citrate buffers.

Learn more about buffers.

Clear front part of the eye.

While most contact lenses (soft, hard or hybrid) rest on the cornea, scleral lenses vault over the cornea and hold fluid against the top of the cornea.

Scleral lenses are used to treat many corneal diseases and conditions, and to improve vision for people with optical irregularities in the cornea.

A lens whose purpose is to be used during the scleral lens fitting process.

These lenses used to be called “trial lenses”, but that wasn’t really accurate. You are not trying them out in practice. Your provider is using them to assess your scleral lens fitting needs and determine the specifications of a customized set they will order for you. It is normal for this process to be repeated, even several times.

The use of diagnostic lenses in the scleral lens fitting process is skill-driven and is not inferior to technology-driven fitting processes.

See “Getting Fitted” (Scleral Lens Roadmap) for more information.

The shape of the outer edges of a scleral lens. This is one of the parameters that can be adjusted which will affect tear exchange under the lens and potentially comfort.

Thickness at the extreme edge of the lens. This is a parameter that can have implications for patient comfort.

One or more holes added to a lens to reduce pressure under the lens or increase oxygenation.

The fluid-filled space between the surface of the eye and the back surface of the scleral lens.

A hybrid lens is a combination of hard and soft.

Its center is made of a rigid gas permeable material while the outer portion (“skirt”) is made of a soft lens material.

Like “piggybacking”, hybrid lenses are a way to try to get the best of both worlds - the better vision quality that only a rigid material can offer, with the comfort that a soft lens can offer (compared to a conventional gas permeable lens resting on the cornea).

Lens designed and fitted from an imprint (mold) of the eye.

Lens diameter determines how much of your eye is covered by the scleral lens. Scleral lenses may be as small as 15mm or less or as large as 25mm. The typical ranges are 16-18mm.

People with ocular surface disease indications are often fitted with larger diameter sclerals both for comfort and to ensure more of the ocular surface is protected.

PRACTICAL TIP: It is important to know the diameter of your lens in order to ensure compatibility with lens cases that you may use.

Junction of the cornea and the sclera. Scleral lenses vault the limbus as well as the cornea.

An improperly fitted scleral may result in bearing or compression of the limbus.

This is one of the reasons that it is important to report any new symptoms of pain, discomfort or redness occurring on lens removal. It is a good idea to be have an appointment at the end of the day so your provider can see how your lens is fitting at the end of the day, not just soon after the lenses are put in.

Fogging or clouding of vision with sclerals due to particles accumulating in the fluid reservoir between the eyey and the lens or deposits on the front surface of the lens.

This is a persistent challenge for many people with ocular surface diseases and is one of the most common complaints amongst long term users.

This is an out-dated term for smaller diameter scleral lenses.

Large and small are relative terms, since we don’t all have the same sized corneas. Nowadays we simply specify the diameter of the lens to indicate its size.

A contact lens solution labeled for rinsing and disinfection of contact lenses.

The label will always state whether it is suitable for soft, hard and/or rigid gas permeable lenses. If it says it is suitable for rigid gas permeable lenses, then it is suitable for scleral lenses (which are made of RGP materials). However, if your sclerals are coated with Tangible HydraPEG, make sure your multi-purpose solution is compatible with the coating as well.

A lens design modification where the lens edge is re-shaped to work around something, such as a pingueculum or a bleb.

Wearing a gas permeable lens on top of a soft lens, as a way to get the superior vision of an RGP but the comfort of a soft lens.

Piggybacking is cheaper and easier than scleral lenses and can be a solution for some people with corneal irregularities or keratoconus.

Common term for the rubber implements used for scleral lens application and/or removal.

The most widely used “plungers” for scleral lenses are:

• DMV Ultra Remover (for removal only)

• DMV Scleral Cup (for application and removal)

• DMV Vented Scleral Cup (for application)

See Product Guides for more information.

GENERAL: A saline solution is salt water, with or without additives to balance the pH and/or preservatives to keep it sterile after opening.

FOR CONTACTS: In the conventional contact lens world, saline solutions are normally preserved and they are used to rinse lenses. They are not used to clean, disinfect or store lenses because they don’t contain any ingredients for those purposes.

FOR SCLERALS: In the scleral lens world, we normally use the word “saline” to refer to the preservative-free saline solutions that we use to fill our lenses.

Buffered saline is simply saline (salt water) to which ingredients are added exclusively to maintain a particular pH.

In a scleral lens context, pH buffering of salines can be important to vision and/or comfort. Unbuffered salines are acidic. Buffered salines match the pH of the eye.

Saline solution (see above) that does not contain any additives to balance the pH. Unbuffered preservative free saline has just two ingredients - purified water, and sodium chloride in a concentration of 0.9%.

Unbuffered saline solutions are acidic - that is, they have a pH lower than 7, typically as low as 5.5. This can be confusing for consumers, because one imagines that the product with the least additives is more natural, therefore more balanced.

“Natural” saline (0.9% sodium chloride solution) is naturally acidic. Ingredients described as buffering agents can be added to raise the pH.

Learn more about buffers in DrB’s Glossary of Eye Drop Ingredients.

White of the eye.

The edges of scleral lenses rest on the sclera (specifically, the scleral conjunctiva).

Scleral lenses look like contact lenses but they are really medical prosthetic devices designed to (a) cover and lubricate the ocular surface and/or (b) provide vision rehabilitation or other functions.

Sclerals are characterized by the following features:

First, they are rigid gas permeable lenses that are fitted to vault over the entire cornea (including the limbus). Their edges land on the on conjunctiva overlying the sclera (thick white of the eye).

Second, scleral lenses are typically medically necessary devices for specific ocular conditions, as opposed to simply an alternative means of vision correction (replacing glasses or conventional soft or RGP lenses).

See also: The Official Guide to Scleral Lens Technology, Page 2.

Tangible® Hydra-PEG® is a lens coating that can be applied to a contact lens. It is a polyethylene glycol (PEG)-based polymer mixture.

The purpose of Hydra-PEG is to provide a “wettable” lens surface that can help to maintain increase comfort and wear time and, critically, to repel deposits of proteins or oils on the lenses.

Hydra-PEG is applied by the laboratory that makes the lenses. It can wear off during the life of the lens, depending on factors such as eye disease state and how the lenses are cleaned.

If a lens is Hydra-PEG coated, this limits the cleaning and disinfection solutions that may be used with the lens, because some solutions contribute to prematurely stripping the coating from the lens.

A design modification available for some scleral lenses which can be necessary in some circumstances when the lens is sealing too tightly. Venting channels promote tear exchange under the lens.