Patients undergoing prolonged non-ocular surgery during general anaesthesia may develop severe ocular complications. The factors contributing to these complications are abolition of protective corneal reflex, decreased basal tear production and absence of pain perception . It is common practice for anaesthesiologists to tape the eyelids closed or to instill topical ophthalmic preparations into the eye, or both, during anaesthesia. To the authors' knowledge based on the MEDLINE database there are no studies comparing the efficacy of eye protection strategies under similar conditions with regard to severity of corneal lesions.
We designed a study to compare four eye protection methods: simple taping, viscous or fluid artificial tears and paraffin-based eye ointment with regard to the severity of possible ocular surface injury with scoring systems. Two hundred ASA I-II adult patients scheduled for elective non-ophthalmic surgery were enrolled. The cornea and conjunctiva were assessed by the ophthalmologist staining tears with fluorescein 1 day before operation and 12 and 24 h after operation.
In all patients anaesthesia was induced with propofol 2 mg kg−1 and maintained with isoflurane 1.5% and 70% N2O-40% O2; the trachea was intubated with the aid of mivacurium 0.2 mg kg−1. The patients were divided into four groups of 50 patients and one of the following methods was applied to the eyes. Group 1: hypoallergenic tape (Hypafix®; Smith and Nephew, France); Group 2: paraffin-based ointment including terramycine (Terramycine®; Pfizer, Turkey); Group 3: polyacrylic acid liquid gel (Viscotears®; Novartis, Turkey); Group 4: artificial tears including hydroxypropyl methylcellulose (Tears Naturale II®; Alcon, Turkey).
The ophthalmologist conducting the pre- and postoperative examinations was blinded to the protection methods. The severity of corneal damage was evaluated by intensity of staining with fluorescein (0, none; 1, mild; 2, moderate; 3, dense) and lesion size (0, none; 1, if the lesion was <1 mm; 2, if the lesion was >1 and <3 mm; 3, if the lesion was >3 mm). Hyperaemia of conjunctiva was assessed using a scoring system (1, hyperaemia located only in the temporal or nasal areas of bulbar conjunctiva; 2, hyperaemia located in the nasal or temporal areas plus hyperaemia and extension to the bulbar conjunctiva near to the upper or the lower fornixes; 3, hyperaemia including all of the areas of bulbar conjunctiva). In the postanaesthetic care unit (PACU) and the day after operation, the patients were asked if they had any eye symptoms such as itching, burning, stings, pain, photophobia, blurred vision or dryness. These symptoms were assessed by 'yes' or 'no'. Statistical analyses were performed with a Kruskal-Wallis test followed by a U-test.
Patients' characteristics and duration of anaesthesia were not different between the groups. There were no significant differences with regard to size or intensity of the corneal staining (Table 1); mean conjunctival hyperaemia scores were similar among all groups. However, in Group 3, the number of patients who had conjunctival hyperaemia was significantly higher at 12 and 24 h after operation than those of the other groups (Table 2). In the PACU, blurred vision was observed in 6 (12%), 15 (30%), 17 (34%) and 21 (42%) patients of Groups 1, 2, 3 and 4, respectively. The highest rate of blurred vision was in Group 4 (P < 0.05). The overall incidence of corneal epithelial defects and conjunctival reactions was 9% (Tables 1 and 2). The highest scores of corneal lesion and hyperaemia were observed in Group 3. Photophobia in Group 2 was more frequent than in the other groups (P < 0.01) and was observed in 6 (12%), 13 (26%), 2 (4%) and 4 (8%) patients of Groups 1, 2, 3 and 4, respectively. Besides, 24 h after operation, the other complaints such as burning, stings, pain and dryness were similar among the four groups.
In the present study, all protection methods were equally effective and had similar rates of corneal abrasion and the same severity of the lesions. In a MEDLINE search conducted from May 1966 to May 2003, there were no studies comparing the severity of the lesions in cornea and conjunctiva by a scoring system with different protection methods. The routine instillation of aqueous solutions, viscous gels or ointments has not been recommended, because they did not offer sufficient additional protection against the development of corneal abrasions, and ointments in particular contributed to significant ocular morbidity . On the other hand, Batra and Bali  reported that taping and applying vaseline gauze to eyes could offer effective eye protection. Schmidt and Boggild-Madsen  did not observe a difference between methylcellulose and paraffin-based ointment regarding protection in eyes of the same patients.
In our investigation, methylcellulose was associated with more blurred vision and polyacrylic acid liquid gel with more conjunctival hyperaemia. However, the use of either methylcellulose or polyacrylic acid liquid gel may not be the cause of these symptoms and signs. They are likely not to be the sole causal factor, as other agents such as vehicles in the drug containers might have been involved in blurred vision and conjunctival hyperaemia. Boggild-Madsen and colleagues  reported that during general anaesthesia methylcellulose 4% provides better eye protection than paraffin-based ointment.
A study that compared a paraffin (lipid-based) eye lubricant with a methylcellulose solution (water-based) during surgery showed a high incidence of eyelid edema, conjunctival hyperaemia and blurred vision in the paraffin group. The authors postulated that the inhalational anaesthetic (halothane) was concentrated in the lipid-based paraffin and irritating to the eye . Although this theory has not been confirmed, the photophobia seen in the patients of Group 2 may be explained by this mechanism. We speculate that photophobia or eye lesions may be prevented by less soluble agents such as sevoflurane and desflurane. In conclusion, with regard to severity of corneal lesion, there was no superiority among commonly used protective eye strategies under general anaesthesia.
Department of Anesthesiology and Reanimation; Harran University Medical School; Sanliurfa, Turkey
Department of Ophthalmology; Harran University Medical School; Sanliurfa, Turkey
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