The results showed no significant differences between the artificial tear and BSS groups in terms of the mean scores of ST and TBUT after eliminating the effect of the demographic and clinical variables. The researchers’ review of literature showed no studies comparing the effects of BSS and artificial tear drops on dry eyes in comatose patients admitted to ICUs. Vasavada et al. (2009) showed that using BSS had more advantages than Ringer’s lactate in terms of corneal thickness and post-operative inflammation in the first day after operation [9]. In agreement with these findings, in another study on intraocular and extraocular tissues, conjunctival and iris tissue samples from patients undergoing cataract surgery and samples from laboratory rabbits, Merrill et al. (1960) found that using BSS for both human and laboratory samples causes no damage to the intraocular tissues compared to sodium chloride [11]. In a clinical trial on patients with dry eyes, Qui et al. (2012) found that the patients’ symptoms were relieved after using each of the two care protocols (using punctual plugs vs. artificial tears) and no significant difference was observed between the two groups. In ST, no significant change was observed in the artificial tear group, but the punctual plug group showed significant changes [12]. It can be inferred from the results of the cited studies that other treatment methods are preferable over artificial tears in preventing dry eyes in patients admitted to ICUs. On the one hand, artificial tears normally contain chemical preservatives for preventing bacterial infections and buffers (such as bicarbonate and phosphate) for maintaining the pH within the normal range (7.4) [13]. On the other hand, the frequent use of eye drops containing preservatives, especially benzalkonium chloride (such as gel tears), is associated with ocular allergies and toxicity [14]. Therefore, BSS can be used as an alternative to artificial tears in patients with dry eyes or those exposed to its risk.
The results of the paired t-test based on ST and TBUT showed no significant differences between first days and sixth day in the BSS and artificial tear groups; however, five days after admission, the severity of dry eyes did not worsen compared to first day of admission and it remained within the moderate range.
BSS contains electrolytes needed for the long-term maintenance of endothelial cells, including Sodium Chloride, Potassium Chloride, Calcium Chloride Dihydrate, Magnesium Chloride Hexahydrate, Sodium Acetate Trihydrate, Sodium Citrate Dihydrate, and Sodium Hydroxide [9, 15]. BSS also appears to act as a nutritional supplement. Compared to other solutions, BSS has isotonic osmolality and is neutral (Osm = 302 mMol, pH = 7.4), which is similar to the osmolality of the eye (Osm = 302 mMol, pH = 7.4). Moreover, BSS contains a citrate acetate and magnesium buffer system that is essential for Mg-ATPase endothelial pump [9].
As a result, despite the high effectiveness of the noted treatment options, since one of the items determining the ease of use of a drug is its cost-effectiveness, BSS appears to be superior. The results of many studies have shown that using artificial tear improves visual acuity [7, 8], and wavefront aberrations [16] in patients with dry eyes. Wei et al. (2020) found that the standard deviation of the objective scatter index (SD-OSI) and the objective scatter index decreased significantly five minutes after the administration of artificial tears in the intervention group of patients with severe dry eyes, while a significant increase was observed in the control group. Nonetheless, 30 minutes after the intervention, no significant difference was observed between two groups in the visual quality parameters. Overall, artificial tears were found to have different effects on the visual quality of patients with dry eyes depending on the severity of their condition [17]. In another systematic study, Ribeiro et al. (2019) found that artificial tears are more effective than ocular lubricants [18]. However, Ishioka et al. (2009) found no significant change in visual acuity in patients with mild dry eyes five minutes after the administration of different concentrations of artificial tears [19].
Based on our findings, BSS can prevent the progression of dry eyes as well as artificial tears. Thus, given the high prevalence of dry eyes among ICU patients and considering the lower costs and good effectiveness of the BSS and its simple formulation, which enables its easier manufacturing, and also the fairly high costs of artificial tear drops, BSS is recommended to be administered by nurses as a useful and effective method for preventing dry eyes in ICU patients.