Trends in impact factors of ophthalmology journals

PURPOSE: To test whether there is an association between the growth in the number of ophthalmic journals in the past years and their mean and maximum impact factor (IF) as a common sign of scientific proliferation. METHODS: Using data from the 2013 Journal Citation Report database a study of the major clinical medical fields was conducted to assess the correlation between the number of journals and maximum IF in a given field in the year 2013. In the field of ophthalmology, we examined the correlation between year, number of journals, mean IF and maximum IF in the field of ophthalmology throughout the years 2000–2013. RESULTS: In the major medical fields, a positive correlation was found between the number of journals and the maximum IF (quadratic R(2) = 0.71, P < 0.001). When studying the field of ophthalmology a positive correlation between the number of journals and mean IF (R(2) = 0.84, P < 0.001) and between number of journals and maximum IF (R(2) = 0.71, P < 0.001) was detected. CONCLUSIONS: Our findings suggest that the variation in the IF can be explained by the number of journals in the field of ophthalmology. In the future, the formation of additional ophthalmology journals is likely to further increase the IFs of existing journals.