Photorefractive (PRK) vs Phototherapeutic (PTK) Keratectomy

Vision correction surgeries have transformed millions of lives by restoring sight and reducing dependency on glasses or contacts. Two such procedures - Photorefractive Keratectomy (PRK) and Phototherapeutic Keratectomy (PTK) - utilize laser technology to reshape the cornea and address refractive errors or corneal surface conditions. The fundamentals are similar, but the purpose, applications, procedural steps, benefits, and risks differ.

This article provides a comprehensive overview comparing and contrasting PRK and PTK. This will also define the procedures and their intended outcomes, detail the surgical steps involved, summarize each technique's advantages, and outline potential complications.

1. Definition and Purpose

PRK and PTK offer hope to those suffering from vision problems and corneal surface conditions. Here’s how these surgical methods can significantly improve vision quality and overall eye health.

Photorefractive Keratectomy (PRK)

PRK is to correct refractive errors in the eye to improve vision. Refractive errors occur when the eye fails to bend (refract) light correctly, leading to vision problems like:

• Myopia (nearsightedness)
• Hyperopia (farsightedness)
• Astigmatism

This correction aims to enhance vision and, in many cases, significantly reduce or eliminate the patient's dependency on eyeglasses or contact lenses. PRK can help patients with dry eyes or thin corneas and those with an active lifestyle or job where the risk of dislodging a corneal flap (as in LASIK surgery) is a concern​​​​.

Phototherapeutic Keratectomy (PTK)

PTK primarily addresses corneal surface conditions such as:

• Irregularities
• Scars
• Dystrophies

The main goal of PTK is to improve vision affected by these corneal conditions and reduce associated pain or discomfort. PTK is particularly effective for treating superficial corneal disorders and is suitable for patients with thin corneas.

Focusing on the corneal surface, PTK helps restore clearer vision and alleviate symptoms related to various corneal diseases​​​​​​.

2. Procedure

Both outpatient procedures involve steps designed to maximize patient comfort and surgical accuracy. Let's examine the procedural nuances contributing to successfully correcting vision and treating corneal conditions.

Photorefractive Keratectomy (PRK)

The PRK procedure is an outpatient surgery that typically takes 10 to 15 minutes per eye. The steps involved in PRK are as follows:

1. Numbing of the Eyes: The surgeon uses anesthetic eye drops to numb the eyes, ensuring the patient's comfort during the procedure.
2. Stabilizing the Eye: A speculum opens the eyelids and prevents blinking during the surgery.
3. Removal of the Epithelium: The outer layer of the cornea, known as the epithelium, is removed using a brush, blade, laser, or an alcohol solution.
4. Reshaping the Cornea: The surgeon uses an excimer laser to reshape the cornea precisely. This step corrects the refractive error by altering how light is focused onto the retina.
5. Application of Eye Drops: After the laser treatment, the surgeon administers nonsteroidal anti-inflammatory, antibiotic, and steroid eye drops.
6. Protective Contact Lens: A clear, soft contact lens is placed on the eye to act as a bandage, reducing irritation and aiding in healing.

The patient is awake during the procedure, and recovery begins immediately after surgery. Post-operative care includes rest, avoiding physical activity as the surgeon recommends, and wearing sunglasses outdoors to prevent scarring​​.

Phototherapeutic Keratectomy (PTK)

PTK is also an outpatient procedure that takes 10 to 20 minutes for both eyes. The steps involved are as follows:

1. Anesthetic Application: The eyes are numbed using topical anesthesia such as Xylocaine or Proparacaine HCl. In some cases, local or general anesthesia may be necessary.
2. Speculum Placement: A speculum is applied to keep the eyelids open and prevent blinking.
3. Excimer Laser Treatment: The surgeon uses a computer-guided excimer laser for photoablation, where laser energy removes the diseased outer corneal layer and smooths the inner surface. The precision of the laser ensures effective treatment with minimal risk.
4. Smoothing the Surface: A masking agent may make irregular protrusions more visible for laser ablation if the corneal surface is rough.
5. Protective Measures: After the laser procedure, the surgeon applies bandage contact lenses (BCL) or eye patches to facilitate healing.
6. Prescription Eye Drops: Antibiotics and other prescription eye drops are given to ease pain and discomfort during recovery.

After the procedure, proper care is essential for healing. The patient may experience temporary hazy vision and discomfort, gradually improving as the epithelium heals​​.

3. Benefits

The decision to undergo PRK or PTK is driven by the potential benefits these procedures offer individuals facing refractive errors or corneal surface conditions. Let's explore how PRK and PTK can significantly enhance quality of life through improved vision and eye health.

Photorefractive Keratectomy (PRK)

PRK offers several benefits for correcting vision problems caused by refractive errors:

• PRK can accurately correct nearsightedness, with approximately 90% of patients achieving 20/20 vision without glasses or contact lenses one year after the surgery. Over 95% achieve 20/40 or better vision without corrective lenses.
• PRK may be preferable for patients with thinner corneas or corneal surface irregularity, as it disrupts less corneal tissue than LASIK.
• PRK is technically simpler than LASIK and utilizes modern laser treatment systems, making it a preferred choice for some refractive surgeons.
• Unlike LASIK, PRK does not involve cutting a flap in the cornea, making it a safer option for individuals with very active lifestyles or occupations where a dislodged flap could be a concern.

Patients considering PRK should discuss the potential benefits with their healthcare providers to understand how it can meet their vision correction needs​​​​.

Phototherapeutic Keratectomy (PTK)

PTK provides several benefits for treating corneal surface conditions:

• PTK effectively treats conditions like corneal scars, dystrophies, and recurrent corneal erosion syndrome (REES).
• It is suitable for people with thin corneas where more invasive procedures may not be advisable.
• PTK does not create a flap in the cornea, eliminating the risk of flap-related complications like detachment or displacement.
• PTK is less invasive than lamellar or penetrating keratoplasties, which require partial or complete cornea transplantation.
• The procedure has a quick recovery timeline and can be repeated to enhance outcomes, providing effective long-term results.

PTK is considered a bridge between surgical and medical management of corneal disorders, offering both therapeutic and refractive benefits​​​​​

4. Risks and Complications

While the benefits of PRK and PTK are significant, patients must know the potential risks and complications associated with these procedures. Let's look at what patients might expect regarding possible side effects and how these can be managed or minimized.

Photorefractive Keratectomy (PRK)

PRK carries certain risks and possible side effects, as with any surgical procedure. These include:

• Scarring on the cornea can occur due to the surgery.
• A cloudiness on the cornea, known as corneal haze, may develop after PRK.
• There is a risk of infection following the procedure.
• Patients may experience glare and halo effects around lights, particularly at night.
• Discomfort, such as pain, irritation, and excessive tearing, can occur after PRK.
• Patients may develop increased sensitivity to light.
• Some patients may experience hazy vision temporarily after PRK. Mitomycin C is sometimes used during surgery to minimize this risk.
• The treatment may become less effective over time, known as regression.
• Healing of the cornea may take longer than expected in some cases.

It's important to note that severe complications such as worse vision or blindness are very rare. The outcome of PRK can vary due to individual differences in wound healing, and some patients may still require glasses or additional surgery for optimal vision​​​​.

Phototherapeutic Keratectomy (PTK)

PTK also involves certain risks and potential complications, including:

• Corneal shape and thickness changes during PTK can lead to refractive errors like hyperopia or astigmatism.
• Deeper stromal ablations during PTK can result in corneal haze, characterized by a reticular pattern localized to the ablation zone. This may cause a slight decrease in low-contrast visual acuity. Adjunctive treatments like mitomycin C can help reduce this risk.
• Systemic diseases or corneal dystrophies can impede the healing process after PTK.
• There is a risk of the cornea becoming too thin post-surgery.
• Reactivation of herpes simplex virus
• Scarring can occur as a result of the surgery.
• There is a risk of eye infection following PTK.

These risks can be minimized with careful preoperative planning and appropriate post-operative care. Patients need to discuss these risks with their ophthalmologist and understand the potential for complications​.

5. Cost

The financial aspect of undergoing PRK or PTK is crucial for many patients. While investing in one's vision can be significant, weighing the potential benefits against the financial implications is essential. Let's explore the typical costs of these eye surgeries and what factors might influence the overall expense.

Photorefractive Keratectomy (PRK)

PRK typically ranges between $1,000 and $3,000 per eye, with an average cost of around $2,300. These figures can vary significantly based on geographical location, the surgeon's experience, technology, and the patient's specific needs.

While some clinics offer seemingly low prices, these may not always include all necessary exams, treatments, or follow-up care, potentially increasing the overall cost. Additionally, some prices might be for patients with minimal degrees of refractive errors, and using advanced technology like Wavefront in the procedure could add to the cost.​

Phototherapeutic Keratectomy (PTK)

The cost of PTK is closely aligned with the cost of LASIK surgery, as mentioned by Whitsett Vision Group. Since PTK is considered an elective surgery, most insurance companies do not cover its cost. However, Health Savings Accounts or Flex Spending accounts may be utilized to cover some of the expenses. Financing options, like those provided through Care Credit, are also available to help manage the cost of the procedure.

To find out the precise cost of PTK, you need to contact the hospital or visit their website and log in for detailed pricing.

Wrap Up

PRK and PTK are outpatient procedures that utilize excimer lasers to reshape the cornea and improve vision. PRK aims to correct common refractive errors by altering the cornea's focusing power, while PTK smooths the corneal surface to restore sight in diseases limited to superficial corneal layers.

PRK offers accurate, long-term vision correction without flap complications, making it suitable for active individuals and those with thin or irregular corneas. PTK provides targeted treatment for corneal conditions through tissue-saving ablation of diseased outer layers. Though both surgeries carry risks like haze, scarring, and infection, serious complications are uncommon.

When considering laser eye treatment, the intended outcome, individual corneal health, lifestyle factors, and surgical risks should guide the selection between PRK and PTK. By understanding the differences between these procedures, patients can seek specialized care to address their specific visual impairment through precision corneal reshaping or surface renewal. With thoughtful evaluation and planning, those suffering from refractive errors or corneal diseases may regain lost vision.

Can PRK and PTK be performed on both eyes at the same time?

Depending on the patient's condition and the surgeon's assessment, PRK and PTK can be performed on both eyes in a single session. However, some patients may opt to have surgery on one eye at a time to minimize the recovery impact.

What type of anesthesia is used for PRK and PTK surgeries?

Both PRK and PTK surgeries are typically performed under local anesthesia with the use of anesthetic eye drops to numb the eye. This prevents any discomfort during the procedure​.

What preoperative preparations are required for PRK and PTK?

Preoperative preparations for PRK and PTK include a comprehensive eye examination to assess suitability and detailed eye measurements. Patients are advised to stop wearing contact lenses for a period before the surgery and may be prescribed antibiotic eye drops to minimize the risk of infection​.

Are there any lifestyle restrictions during the recovery period for PRK and PTK?

During the recovery period for both PRK and PTK, patients are advised to avoid rubbing their eyes, swimming, using makeup around the eyes, and engaging in contact sports. Exposure to bright light and screen time may also need to be minimized.

Can PTK be used to treat dry eye syndrome?

PTK is not typically used to treat dry eye syndrome directly. However, it can address corneal surface conditions that may contribute to dry eye symptoms. Patients with dry eye may need to manage this condition separately.