There are no data available regarding the complications associated with using antibiotic ointment at the end of intraocular surgery. Therefore, this study aimed to explore the necessity of using ocular tobramycin-dexamethasone prophylactically at the end of intraocular surgery. The results suggest that prophylactic tobramycin-dexamethasone eye ointment did not decrease the risk of endophthalmitis after intraocular surgery. Preoperative antibiotics and standardized surgical disinfection procedures probably play important roles in the prevention of endophthalmitis.
Topical antibiotics are used at after intraocular surgery to prevent pathogenic microbial invasion and prevent bacterial endophthalmitis, and are considered as routine in almost all eye surgeries. The most common cause of endophthalmitis is Gram-positive bacteria and coagulase-negative cocci, which come from the eyelids, conjunctiva, lacrimal glands, hands of surgeons, nurses and anesthesiologists, surgical instruments, suction pipe perfusion, flushing fluid, vitreous substitutes, eye ointment after surgery, and operating room air [18,19]. Regarding the prophylactic measures based on povidone-iodine 10% solution for lids and lashes, during small-gauge vitrectomy, the conjunctiva is displayed before making a trocar entry, giving rise to patient complaints of pain and blurred vision, but following PPV, endophthalmitis can be reduced . There are no reported data illustrating the correlation between the occurrence of endophthalmitis and the use of topical antibiotics immediately following intraocular surgery.
In the present study, tobramycin-dexamethasone eye ointment use did not decrease the occurrence of endophthalmitis. Furthermore, patient complaints such as eye secretions and a foreign body feeling were increased in the tobramycin-dexamethasone eye ointment group compared with the non-ointment group. Therefore, these results suggest that the use of topical tobramycin-dexamethasone eye ointment at the end of intraocular surgery is unnecessary, but provided that a strict protocol is followed. First, preoperative antibiotics were used for the prevention of acute endophthalmitis. Second, sufficient and entire preoperative disinfection of the eyelid was performed. In addition, povidone iodine was used for conjunctival sac disinfection during surgery. Moreover, the eye ointment routinely used at our center contains tobramycin and dexamethasone, which may have caused an allergic reaction in the eye. Though the conjunctival and corneal incisions were tightly sutured after intraocular surgery, there were still some gaps in the incision, which caused a siphoning action of the ointment accompanied by hypotension in the eye. Of course, there is the possibility of bacterial resistance to antibiotics developing over time . Furthermore, the cost of antibiotics is part of the medical burden in China. In the process of opening the ointment bottle, it is possible to smear some ointment in some cases, which can transport bacteria into the eyeball through the incision. In the operating room, one ointment tube was usually used for several patients in one day, which can also affect the sterility of the eye ointment.
High-quality evidence about preoperative antibiotics for the prevention of acute endophthalmitis after cataract surgery has been reported in the Cochrane Library, offering different suggestions about the use of topical antibiotics . One report showed that an injection of cefuroxime with or without topical levofloxacin can decrease the chance of endophthalmitis after surgery . Another suggested that the use of antibiotic eye drops in addition to an antibiotic injection reduced the chance of endophthalmitis compared with using an injection or eye drops alone . Therefore, it is questionable whether to use topical antibiotics prophylactically. Topical antibiotics used before or after an ocular surgery for avoiding endophthalmitis are controversial, as harmful effects have been highlighted with the use of topical antibiotics, such as increased antibiotics resistance.
Prophylactic antibiotic use in intraocular surgery has rarely been reported, and is usually discussed in injection surgery. The reported rate of endophthalmitis following cataract surgery and intravitreal injections was 0.07%-0.4% and 0.038%-0.065%, respectively . Surgical risk factors associated with endophthalmitis after PPV include inadequate wound closure, a postoperative hypotonic state, vitreous incarceration at a sclerotomy site, and aqueous intraocular tamponade. The related factors for antibiotic regimens are training (60.1%) and personal experience (58.1%), which was reported by a survey study that comprised 782 oculoplastic surgeons in 43 countries . The occurrence of endophthalmitis is often related to the patients’ own condition; patients who are immunocompromised or taking preoperative topical steroids often have an elevated risk of endophthalmitis after PPV .
To date, few clinical studies have focused on bacterial detection by culturing the tobramycin-dexamethasone eye ointment tube after it was opened. The present study provides a chronological report of the pathogens in the eye ointment tube after being opened. All tested samples over 7 days were negative, but it cannot be ruled out that there are bacteria in tobramycin-dexamethasone eye ointment after being opened. A detection rate of positive bacteria in eye ointment of 30%-50% has been reported by several studies [27,28]. Therefore, another implication of the present study is that doctors should be cautious regarding the use of tobramycin-dexamethasone eye ointment at the end of intraocular surgery, as well as the consequence of increasing the risk of endophthalmitis after surgery. In the future, attention should be paid to the cautious use of antibiotic eye drops at the end of intraocular surgery.
Of course, the present study has limitations. The sample size was relatively small and from a single hospital. Only one doctor systematically used the tobramycin-dexamethasone eye ointment at the end of intraocular surgery, while the others did not, probably introducing some bias. Nevertheless, the entire preoperative and intraoperative disinfection protocol is the same for all surgeons. Finally, the occurrence of endophthalmitis events was very low, preventing any analysis of the factors associated with the occurrence of endophthalmitis.
In conclusion, using tobramycin-dexamethasone eye ointment did not decrease the risk of endophthalmitis after intraocular surgery, although there was not sufficient evidence to demonstrate that it is better not to use topical antibiotics (such as other kinds of antibiotic eye drops or ointment) at the end of intraocular surgery. Considering antibiotics resistance, surgical treatment specifications, side effects of the ointment, increased eye secretions, uncomfortable feeling, and cost burden, we suggest that it is not necessary to use tobramycin-dexamethasone eye ointment prophylactically at the end of intraocular surgery, but prospective trials will be necessary to confirm those results. In the future study we plan to perform the large sample randomized controlled trial with a non-inferiority design to confirm our conclusion.