The objective of the study is to determine the relationship between quality of care and the loyalty of external users in a private ophthalmic center in Lima, Peru. The method used was a descriptive, cross-correlational, quantitative approach with non-experimental design. The population consisted of 210 external users who received therapies for at least 1 month in an ophthalmologic center located in Lima, Peru; the sample (statistically calculated) consisted of 137 users randomly selected, who responded to a series of reagents through a survey. A questionnaire was used to measure quality of care through SERVPERF model, while loyalty was measured through reagents developed by the authors, based on the scientific theory of Alcaide. Spearman's Rho determined that there is a moderate positive relationship between the quality of care and loyalty (sig. < 0.05; r = 0.594). Likewise, it is determined that there is a positive correlation between the dimensions of tangibility, empathy, responsiveness, security and reliability with the loyalty variable, since the sig. were < 0.05 and the values of r = 0.497, 0.381, 0.342, 0.109 and 0.452, respectively were obtained. Not enough statistical evidence was obtained to find a relationship between the loyalty variable and the security dimension, since a sig. value > 0.05 was obtained. The results found are related to those found by previous authors in other contexts. Finally, we recommend other researchers to carry out similar research internationally, in order to increase the literature on the variables of loyalty and quality of service and generate discusion.