Reducing Pain From Retinal Laser With Vibrational Stimulation

Background:

Panretinal photocoagulation (PRP) is a widely used laser treatment for proliferative diabetic retinopathy (PDR). However, the associated ocular pain can make the procedure uncomfortable, leading to increased treatment visits or missed appointments. This pain is multifactorial and can be exacerbated by factors such as anxiety and hypervigilance. Traditional pain management techniques, such as regional anesthesia, are effective but invasive and carry potential complications. Oral medications have largely proven ineffective in alleviating PRP-related pain.

The Gate-Control Theory of pain posits that non-noxious stimuli can inhibit pain signals by activating A-β fibers, effectively "closing the gate" to pain transmission through A-δ and C fibers. The most relatable example is the mother rubbing a child's knee after an impact injury in the affected region. Transcutaneous electrical nerve stimulation (TENS) which utilizes the Gate-Control Theory of pain, has been shown to reduce ocular pain during PRP. However, its use raises practical concerns, including the need to carefully adjust pulse width, intensity, and frequency for effective pain relief. Additionally, some patients may find the muscular contractions or paresthesia uncomfortable. TENS is also contraindicated in individuals who are pregnant, have epilepsy, or have pacemakers. Vibratory stimulation activates cutaneous mechanoreceptors to reduce pain during intramuscular and subcutaneous injections. This technique is safer and less invasive than TENS and is therefore an ideal candidate for evaluating its effect in pain reduction during PRP. This study has the potential for an innovative concept by utilizing a vibratory device integrated within the PRP machine headrest.

Hypothesis:

Vibratory stimulation is expected to reduce ocular pain during PRP by activating cutaneous mechanoreceptors and inhibiting pain transmission, as suggested by the Gate-Control Theory. Its non-invasive nature makes it a practical alternative to traditional pain management methods, potentially enhancing patient comfort during the procedure.

Objective:

To evaluate the effectiveness of vibratory stimulation in reducing ocular pain during PRP treatments

Method:

Subjects will be recruited at a single tertiary referral center (Alberta Retina Consultants, Edmonton, Alberta). Matriculation will be established upon obtainment of consent, and patients will have the autonomy to withdraw from the study at any stage. The enrollment period will be from October 2024 to March 2025, with a total of 50 patients.

Laser settings will be tailored to each patient based on individual differences in pigmentation and tissue uptake. The threshold for treatment will be determined by observing an opacified photothermic response. For each patient, one eye will be treated without vibratory stimulation, while the contralateral eye will receive stimulation using the Blaine Labs Vibration Anesthesia Device. The assignment of which eye receives which treatment will be randomized using Python programming, ensuring a balanced allocation. To minimize variability, the time taken to perform PRP on both eyes will be kept as equal as possible. A no-treatment zone of 1 clock hour from the horizontal meridian will be maintained to avoid the long ciliary nerves. After treatment, patients will complete a validated survey based on the numeric rating scale (NRS) to assess pain levels for each eye treated.