Identification and description of controlled clinical trials published in Spanish Ophthalmology Journals

Properly conducted controlled clinical trials (CCTs) provide the highest level of evidence for optimising decision-making in healthcare. Electronic search strategies do not exhaustively retrieve them, because of issues related to indexing, exclusion of journals in languages other than English, among others. A handsearch approach is therefore warranted. We aimed to identify all CCTs published in Ophthalmology journals in Spain, to describe their main features, and to submit them to the Cochrane Register of CCTs (CENTRAL).

After identifying all Spanish Ophthalmology Journals, we conducted a systematic handsearch following Cochrane guidelines. When appropriate, results were compared against electronic searches. A descriptive analysis was completed, including risk of bias assessment.

We identified 18 eligible journals; 10 074 original articles, editorials, letters to the editor, abstracts and conference proceedings were assessed via handsearching for inclusion. Of these, 136 were subject to title and abstract screening, after which 102 were classified as CCTs. We identified three articles via electronic searches that had not been detected via handsearch, for a total of 105 CCTs. Among these, the most investigated pathologies were cataracts (32/105; 30.5%) and glaucoma (23/105 21.9%). Regarding risk of bias, 104/105 (99.0%) were deemed as "high risk of bias", mainly due to flaws in sequence generation and allocation concealment. 15/105 (14.3%) mentioned conflicts of interest, half of which had something to declare. No CCT reported adherence to CONSORT.

Spanish Ophthalmology journals publish a low number of CCTs, with limited methodological quality. Handsearching was more sensitive than the electronic searching. Abbreviations CCT: Controlled clinical trial.