FRANKFURT, Sept 8 (Reuters) - Bayer said on Thursday its anti-blindness treatment Eylea, jointly developed with Regeneron, has been shown to work as well when given at a higher dose at a longer interval between injections.

Two late-stage trials showed that Eylea, which is normally given in doses of 2 milligrams every eight weeks, was as effective when given at 8 mg at longer intervals, without any additional safety issues, the German company said in a statement.

The results will help Bayer compete with Roche, whose rival drug Vabysmo was launched this year. The Swiss drugmaker is seeking to win over patients with longer intervals between injections.

The two trials covered wet age-related macular degeneration (AMD), which is the leading cause of blindness among the elderly, and diabetic macular oedema, respectively.

The results are a fillip for Bayer while it is burdened with billions in U.S. legal settlement costs over claims that its weedkiller Roundup causes cancer, though the company has recently won a string of court cases.

Eylea and stroke-prevention pill Xarelto are Bayer's most lucrative pharmaceutical products.

Eylea sales have held up well despite competition from newly launched Vabysmo, and Beovu by Novartis, which has been linked to certain inflammatory conditions in some patients.

Bayer generated sales from Eylea in the first half of 1.58 billion euros ($1.58 billion), up 14%, but the active ingredient's patent will expire in Bayer's key European markets in 2025.

Roche's Vabysmo had sales of 109 million Swiss francs ($112 million) during the first half of the year.

(Reporting by Ludwig Burger; editing by Matthias Williams)