The aim of this study is to compare the severity of expressed pain scores in patients with PDR who underwent either PASCAL or conventional laser and to assess the association between patient characteristics and severity of pain.

Proliferative diabetic retinopathy (PDR) is a severe complication of diabetes mellitus characterized by new vessel formation in the retina and optic disc. Tight glycemic control and laser treatment in the early phases of the disease may slow the progression of PDR. Panretinal photocoagulation (PRP) is a laser-based treatment modality that destroys the outer retina layers and thereby improves the oxygen supply of the inner retina. During the following years, sequential improvements took place, including introduction of yellow, green, and diode lasers with various advantages of each wavelength.

In 2006, a novel semi-automatic and multi-shot photocoagulator called as PASCAL (Pattern scan laser, Opti-Medica Corp., Santa Clara, California, USA) was introduced with a reduction in pulse duration of each laser spot from typical 100 ms down to 10-30 millisecond. Compared with the conventional laser, shorter pulses have been shown to significantly reduce the risk of damage to the adjacent retinal tissues.

Almost all patients experience pain during PRP. While some patients may tolerate the pain, the majority does not. One study reported that 64.1% of patients did not complete treatment due to pain and therefore had an increased risk of vision loss. To improve patient compliance, several anesthetic and analgesic techniques such as peribulbar anesthesia, oral anesthesia and topical eye drops have been used. The patient comfort, and thus compliance, may be improved by using the shorter exposure burns, avoiding red or infrared wavelengths with deeper penetration, and by decreasing overall treatment time.

The aim of the current study was to compare the severity of expressed pain scores in patients with PDR who underwent either PASCAL or conventional laser.

As a method of this study, both eyes were treated within the same session and while one eye was treated with PASCAL laser, the other was treated with conventional laser (ELLEX Integre, Adailade, Australia) with 30 minutes resting intervals. To avoid a bias about orientation or becoming accustomed to laser procedure, PASCAL laser was performed in the first eyes in half of the patients (14 patients) and conventional laser was performed in the first eyes in the other half of the patients randomly. While the spot size used to obtain a white-grayish spot on the retina was 200-400 µm in both PASCAL and conventional laser, the pulse duration was 100 ms with conventional laser and 30ms with PASCAL laser. In order to accurately and reliable compare the grade of pain between each procedures, the retinal areas and total number of spots were standardized. Similar numbers of laser spots were created by two laser systems in same retinal quadrants in both eyes. Ten minutes after the procedure ended the severity of pain was assessed using a verbal rating scale and a visual analog scale (VAS). In the verbal scale the patient rates the pain on a Likert scale verbally, e.g. "none", "mild pain", "moderate pain", "severe pain" or "very severe pain" in five grading system (0-4) and in the VAS they specify the severity of pain by indicating a position along a continuous line from 0 to 10. Using these scores, relationship between severity of pain and patient characteristics including history of prior PRP treatment (experience), gender and duration of diabetes mellitus were assessed. Patients were assigned either in the experienced or non-experienced groups depending on history of prior PRP.

Inclusion Criteria:

• Patients (>18 years) with type 1 or 2 diabetes and bilateral high-risk proliferative diabetic retinopathy (PDR)

Exclusion Criteria:

• Patients with a history of focal/grid photocoagulation, a history of orbital trauma, orbital infection or surgery, those with corneal or lens opacities, those with vitreous hemorrhage and non-compliant patients