## 4 Discussion  
The current study is a cadaveric proof of concept study of SER for better endoscopic visualization in EES. The newly developed SER has several advantages over the conventional ear speculum. First, it is safe and easy to place and remove with the use of forceps. After completing the whole procedure, endoscopic examination revealed no damage to the skin or soft tissue of the EAC. Second, the use of an SER may allow a significant reduction in the procedure time during various EES due to less frequent endoscopic lens cleansing to remove hair and earwax. As EES is performed by a single surgeon, endoscope contamination can compromise the surgeon's vision and negatively affect the surgery [12]. In a survey asking otologists who routinely perform EES about the need for better instrumentation, more than 60% of respondents felt the need for improvements in order to 'keep the endoscope lens clean' [13]. The skin which lines the cartilaginous section of the canal is thicker, more mobile, and contains sebaceous and ceruminous glands and hair follicles [14] that can contaminate the lens while inserting the endoscope, requiring the surgeons to intermittently discontinue surgery to remove and clean the endoscope and reinsert it [15; 16]. This can be time-consuming and taxes the surgeon's patience. Often the canal hair is trimmed before the start of the surgery to reduce fogging and smearing. Figure 4: Endoscopic images obtained immediately after tympanoetal flap (TMF) elevation in the self-expandable retainer (SER) group. **(a)** Endoscopic image showing the bare type of SER and hairs and earwax (arrowheads) in the external auditory canal visible through the wire mesh of the SER. **(b)** Endoscopic image showing the fully covered SER. **(c)** TMF elevation was performed using a canal knife (arrowheads). **(d)** A successfully elevated tympanic membrane (arrows). Endoscope contamination can also be due to bleeding. In traditional microscopic surgery, the non-dominant hand holds the suction instrument to maintain retraction and removal of blood from the operative field while the dominant hand holds the instruments [17]. Bleeding in EES is a major concern for the operating surgeon because the non-dominant hand also must hold the endoscope. Techniques utilized to achieve hemostasis include diathermy probes (monopolar and bipolar) [11], diluted epinephrine injection, epinephrine-soaked cotton balls that can also be used as adjuncts for soft tissue dissection [18], and preoperative injection of tranexamic acid [12] which is an anti-fibrinolytic used in a variety of surgical procedures [19; 20; 21]. Because our study used cadavers, we could not assess the advantage of the SER with regard to bleeding. The most common site of bleeding is in the posterior and superior portion of the EAC [11], where the main vascular supply comes from the anterior tympanic and deep auricular branches of the internal maxillary artery, the superficial temporal artery, and the posterior auricular artery [22]. We hypothesize that the SER might reduce bleeding by protecting the EAC skin from trauma from sharp surgical instruments and also by pressing against the vascular structures and reducing blood flow by the outward expanding force of the SER putting pressure on the soft tissues of the EAC. This idea needs further verification in preclinical and clinical studies. Thermal injuries can be caused by the light source of endoscopes [23; 24; 25; 26; 27; 28], therefore frequent removal of the endoscope from the field may be beneficial in preventing this [26]. Using an SER will reduce the frequency of endoscope removal from the surgical field; therefore other cooling methods should be implemented to ensure safety. These include the use of suction, turning off the light source at regular intervals, and the use of endoscope sheaths and saline irrigation [26; 29]. SER not only allows for a straightened and slightly widened ear canal but also protects the soft tissue around the ear canal from the surgical instruments used in EES.