## 3 Results
### Side Effects of HIFU
#### 3.2.2 Ocular Complications  
Micro-focused ultrasound (MFU) technology allows precise targeting at specific depths, making it ideal for delicate areas such as the eye contour [6]. However, the HIFU/MFU treatment for eyelid rejuvenation has been associated with serious ocular complications [6]. This technology delivers focused high-energy ultrasound at 65-75 \({}^{\circ}\)C to TCPs, making the focused dots produce high temperatures as a result. It can achieve the tension and pulling effect of the deep dermis and fascia [1; 6; 9].  
A recent published study reported that a 40-year-old female had mild pain and blurred vision in the left eye, accompanied by redness and discomfort. It was reported that she was followed up for one year. The treatment device was a high-intensity bundled ultrasound skin surgery instrument (SHURINK-A 50/60 Hz (A35100.02 (3)). After HIFU treatment, the vision in her left eye was blurred for the duration of half a day. The device settings were as follows: 0.9 J/cm\({}^{2}\), at a depth of 2.0 mm, double-line emission, with a line length of 20 mm and a distance of 1.5 mm between each TCP, and a distance of 3 mm between each row of lines. The woman reported a history of bilateral refractive surgery with laser in situ keratomileusis (FS-LASIK) performed one year prior. She reported that six months after HIFU application, she still had blurred vision in the left eye [6].  
In another study, a 47-year-old woman (without any ophthalmological history) was reported to have symptoms of discomfort during HIFU around the right upper eyelid area. Thus, the left eyelid was not treated. HIFU was applied by a trained dermatologist and no eyelid protection was used. The patient immediately visited the hospital, where ophthalmologists reported that she had mild ocular hyperemia, three spots on her cornea, and three punctiform epithelium defects with stromal infiltrate and local stromal edema, alongside an adjacent clear cornea.  
The intraocular pressure (IOP) was 16 mmHg, and the funduscopy showed no abnormalities. The patient was treated with eye drops in the first week and then tapered off until the completion of 30 days of treatment [6; 18].  
The ultrasonic energy generated by HIFU can denature proteins, leading to conditions such as the following:  
* Severe traumatic cataracts leading to lens-related surgery;
* Visual impairment;
* Injuries to the iris (blurred vision and iris pigment detachment);
* Heat damage to the conjunctiva;
* Increased intraocular pressure (IOP);
* Rare cases of myopia.  
Although there are studies that suggest that topical application of HIFU to the eyelids can denature the protein inside the lens, HIFU therapy is approved for use in the periocular area [6]. HIFU can denature proteins, leading to side effects such as the following:  
* Severe traumatic cataracts leading to lens-related surgery;
* Visual impairment;
* Injuries to the iris (blurred vision and iris pigment detachment);
* Heat damage to the conjunctiva;
* Increased intraocular pressure (IOP);
* Rare cases of myopia.  
Also, the HIFU probe should not be placed in the eyebrow arch and eyelid to avoid eye injury [6].