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Ocular Cryotherapy

The Chilling Effectiveness of Ocular Cryotherapy

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The use of cold temperatures to treat conditions affecting the eyes or eyelids is known as ocular cryotherapy. Cryotherapy has been utilized in the ophthalmology field since the mid-1960s, and Keeler Ophthalmic Instruments has been a leader within the space since 19670.

Outside of cataract extractions, and retinal conditions, ocular cryotherapy is typically used for surface procedures — where the actual cryoprobe is applied to the eye or eye lid without making any type of incision. Since ocular cryotherapy doesn’t require tissue incision, it’s considered to be a safer and less invasive type of procedure. The application of cryotherapy is primarily based on the changes of the tissue caused by subfreezing temperatures.

At Keeler, we take an infinite amount of pride in our continued ability to provide ophthalmic surgeons with reliable Cryo Systems, such as the Cryomatic Console MKII. Let’s take a closer look at how ocular cryotherapy works and some of the most common applications.

How Does Ocular Cryotherapy Work?

Cryotherapy requires a cryogen or an extremely cold substance as well as a system of delivery to transfer the cold to the target tissue. Some of the most common cryogens used today include:

  • Freon or liquid argon that has a boiling temperature of –35°C
  • Liquid nitrogen that has a boiling temperature of –196°C
  • Carbon dioxide snow that has a boiling temperature of –79°C

These substances are typically applied to the tissue through a cryoprobe. The cryoprobe is a closed system that circulates the cryogen inside of a metal probe, and the freezing probe is effectively applied to the tissue.  The basic physical principle is the Joule-Thomson effect is that when a gas such as compressed carbon dioxide or nitrous oxide gas is expanded suddenly to pressure of the atmosphere, a quick drop in temperature results.

As living tissue is exposed to freezing temperatures, it responds with the formation of ice within the cells and within the additional fluid surrounding the cells. It also results in the formation of ice within the small blood vessels, which interrupts the supply of blood to nearby cells. These factors work to destroy living tissue through necrosis and ischemia. Also, inflammation is induced as a direct response to the death of cells.

Cryoextraction of Cataracts

The first well-accepted ocular cryotherapy use was the cryoextraction of cataracts. Prior to cryotherapy, cataract surgery was conducted through the complete removal of the cataractous lens via a 10-12 mm incision. Because the lens was physically grasped with either a suction device or capsule forceps, lens breakage was very common. However, when the cryoprobe was used for extracting lenses in the mid-1960s, it quickly became the standard and the most widely used method of extraction in the 1970s.

Retinal Cryopexy

Retinal cryopexy continues to be a viable method of correcting retinal breaks, which includes retinal tears or holes. Retinal breaks have long been considered the most common cause of retinal detachments. By applying extreme cold to the retinal pigment epithelium and to the choroid, subsequent scarring and cell death is achieved, which results in the edges of the retinal break being sealed.

In addition to repairing retinal breaks, retinal cryopexy is commonly used during scleral buckling procedures for retinal detachment as well as pneumatic retinopexy for retinal detachments. This procedure is intermittently performed simultaneously with pars plana vitrectomy to promote chorioretinal adhesions. However, this procedural application has largely been replaced by the use of endolaser techniques.

Cryosurgery for Types of Glaucoma

In instances of severe intractable glaucoma, cyclocryopexy for advanced glaucoma can be used. Once the glaucoma has failed to respond to traditional glaucoma surgery or medication, ocular cryopexy can be applied to the ciliary body through a transscleral application, which can help reduce aqueous production to significantly reduce intraocular pressure. In addition, peripheral retinal cryoablation can be used for neovascular glaucoma.

Cryosurgery for Treating Neoplastic Lesions

Ocular surface neoplasia: conjunctival and corneal intraepithelial neoplasia and squamous cell carcinoma; melanocytic tumors; and conjunctival lymphoma has a higher cure rate when surgical excision is followed by cryotherapy.

What Are the Contraindications of Cryotherapy?

While cryotherapy is a highly effective solution for a range of conditions, it’s important to understand a few significant conditions that may make cryotherapy less effective or even harmful, such as:

  • Bacterial infection
  • Fungal infection
  • Viral infection.

These infections can occur on the eyelids or ocular surface. However, Keeler’s Cryomatic MKII features a range of innovative advancements designed to help reduce the likelihood of problems during surgery. For example, the Cryomatic MKII includes a built-in back-flush facility. During purging and approximately 20 seconds following the release of the footswitch, the flow of the gas in the system is reversed at a lower pressure.

The altered direction of gas after a freeze works to flush out any moisture or debris that may be accumulating, which works to eliminate many surgical risks.  In addition to the previously mentioned factors, the lack of cooperation by the patient is a potential contraindication.

Contact Keeler Ophthalmic Instruments for Ocular Cryo Systems

As the first name in Cryo Ophthalmic Surgery, Keeler has been delivering high-quality, reliable Cry Systems since 1966. Over the years, we’ve continued to re-engineer and evolve our technology to meet the needs of today’s ophthalmic surgeon.

About the Author Eugene VanArsdale

Eugene is the Director of Marketing Communications at Keeler Instruments. He has been with Keeler since 1982 and is co-holder of two patents for the company. Eugene has a true passion for the eye care industry and has dedicated himself to understanding the ins and outs of the optometric and ophthalmic equipment market.