THC senkt den Augeninnendruck, reicht aber bei Glaukom nicht aus

Seit Jahrzehnten fasziniert ein ungewöhnlicher Effekt von Cannabis die Forschung: THC kann den Druck im Auge senken. Diese Beobachtung hat Fragen darüber aufgeworfen, ob Cannabinoide künftig eine Rolle bei der Glaukombehandlung spielen könnten.

Now, a 2026 published systematic review and meta-analysis has taken a closer look at the clinical evidence. The findings confirm that THC can reduce intraocular pressure (IOP), but they also reveal an important limitation that helps explain why cannabis has not become a standard glaucoma therapy. The findings suggest that the future of cannabinoid research may not be about smoking or consuming cannabis at all. Instead, scientists may be looking for ways to harness the eye’s cannabinoid receptors while avoiding the systemic and psychoactive effects associated with THC. Let’s dive into the research and what it means for the future of pharmaceutical grade cannabis therapies.

Was ist der Augeninnendruck?

Augeninnendruck bezeichnet den Druck, der durch Flüssigkeit im Auge entsteht. Die Aufrechterhaltung eines gesunden IOP ist wichtig, weil zu hoher Druck zu Schäden am Sehnerv führen kann, dem Strukturelement, das visuelle Informationen vom Auge zum Gehirn überträgt.

Glaukom ist weltweit eine der Hauptursachen für irreversible Erblindung. Im Jahr 2020 waren schätzungsweise 79,6 Millionen Menschen von der Erkrankung betroffen; bis 2040 wird diese Zahl voraussichtlich auf 111,8 Millionen ansteigen. Die Senkung des IOP ist eine der zentralen Strategien zur Behandlung von Glaukom. Je nach Schweregrad kann die Therapie eine IOP‑Reduktion von etwa 20 % bis 30 % anstreben, bei fortgeschrittenem Glaukom manchmal sogar 30 % bis 40 % erfordern.

Das erklärt, warum die Frage zu THC komplexer ist, als nur zu prüfen, ob es den Augeninnendruck senkt. Entscheidend ist, ob es den IOP ausreichend, zuverlässig und langfristig senken kann, um Menschen mit Glaukom zu schützen.

Studie untersucht THC und Augeninnendruck

Veröffentlicht am in the Canadian Journal of Ophthalmology, the research¹ is a systematic review and meta-analysis examining previous studies of THC and intraocular pressure. Rather than relying on the results of one experiment, the researchers pooled available evidence to estimate how much THC affected IOP across studies and delivery methods.

The review included five studies involving 99 patients, 69 of whom received THC exposure or intervention. The researchers examined THC administered through intravenous, oral, and topical routes. This is where the results become especially interesting.

THC kann den Augeninnendruck tatsächlich senken

Across the included studies, THC was associated with a pooled peak IOP reduction of 14.66%. The reduction was statistically significant overall. At first glance, that may sound encouraging. A substance capable of lowering eye pressure by nearly 15% could appear to have genuine therapeutic potential. However, the route of administration made a substantial difference.

Intravenös verabreichtes THC erzielte die größte gepoolte Spitzenreduktion von 33.27 %. Oral verabreichtes THC zeigte eine deutlich geringere geschätzte Reduktion von 10.65 %, während topisch verabreichtes THC eine geschätzte Reduktion von 9.36 % erreichte. Wichtig ist, dass die Konfidenzintervalle für die oralen und topischen Ergebnisse die Null überschritten, was bedeutet, dass die Evidenz für diese Applikationsformen nicht statistisch eindeutig ist.

The researchers also looked at four studies that directly compared THC with a control. In that analysis, THC produced a pooled peak IOP reduction of 6.88%, and the difference from control was not statistically significant. The evidence suggests THC can lower IOP, but its effect compared with control was less convincing.

Warum die Senkung des Augeninnendrucks allein nicht ausreicht

The biggest challenge is not necessarily whether THC can influence eye pressure. It is whether that effect is practical as a glaucoma treatment. Glaukomtherapien sind in der Regel darauf ausgelegt, eine dauerhafte und vorhersehbare IOP‑Kontrolle zu gewährleisten. Konventionelle Behandlungen umfassen Prostaglandin‑Analoga, Betablocker, Alpha‑Adrenerge Agonisten, Carboanhydrase‑Hemmer, Rho‑Kinase‑Inhibitoren und Miotika. Manche Patienten benötigen mehr als ein Medikament, um den Ziel‑IOP zu erreichen.

THC stellt ein anderes Problem dar. Frühere Humanstudien haben gezeigt, dass inhaliertes THC den IOP senken kann, jedoch ist dieser Effekt nur von kurzer Dauer. Eine Studie mit gesunden Erwachsenen ergab, dass inhaliertes THC den IOP um bis zu 16 % senkte, wobei die Reduktion mehrere Stunden anhielt, bevor sie allmählich nachließ. Das mag für den Nachweis einer biologischen Aktivität nützlich sein, doch Glaukom ist eine chronische Erkrankung, die eine langfristige Druckkontrolle erfordert. Eine Behandlung, die nur eine kurzzeitige Reduktion bewirkt und zudem systemische Effekte auslöst, ist schwer als Ersatz für speziell für Glaukom entwickelte Medikamente zu nutzen.

Das psychoaktive Problem von THC

There is another obvious obstacle: THC does not act only on the eye. When THC is inhaled or consumed, it enters the systemic circulation and interacts with cannabinoid receptors throughout the body and brain. Its psychoactive effects can include changes in perception, cognition, and alertness.

That creates an important mismatch. Researchers want the pressure-lowering effect in the eye, but patients do not necessarily want the rest of THC’s effects every time they need to manage their IOP. This is one reason researchers have increasingly explored cannabinoid compounds that can target ocular pathways without producing significant systemic or psychoactive effects.

Wie Cannabinoide den Augeninnendruck beeinflussen können

The eye contains components of the endocannabinoid system, including cannabinoid receptors in structures involved in controlling aqueous humor dynamics. Researchers have proposed several mechanisms through which cannabinoids may influence IOP, including changes in aqueous humor production and drainage. Cannabinoid signaling may affect structures such as the trabecular meshwork and Schlemm’s canal, which play important roles in fluid outflow from the eye.

This is where the research becomes particularly promising. If scientists can identify which cannabinoid receptors and signaling pathways are responsible for reducing IOP, they may be able to design drugs that target those pathways more precisely. In other words, the valuable discovery may not be that cannabis can lower eye pressure. It may be that the eye’s cannabinoid system contains therapeutic targets worth developing.

Zielgerichtete Cannabinoid‑Medikamente könnten der nächste Schritt sein

Researchers have already investigated synthetic cannabinoid receptor agonists and other cannabinoid-based compounds as potential ocular treatments. There has also been research exploring formulations designed to improve delivery of cannabinoid compounds directly to ocular tissues while reducing systemic exposure. This approach could potentially address several problems at once, including improving how much of a compound reaches the eye, extending its duration of action, and minimizing unwanted effects elsewhere in the body.

Non-psychoactive cannabinoids and compounds designed to selectively interact with cannabinoid receptors are therefore an important area for future investigation.

THC ist kein Heilmittel gegen Glaukom

The meta-analysis should not be interpreted as evidence that people with glaucoma should replace prescribed treatment with cannabis. The study found that THC significantly reduced IOP overall, but the effect was comparatively less compelling against control. The evidence base was also small, consisting of only five studies and 99 total participants.

That matters when interpreting the findings, as a statistically measurable biological effect is not automatically the same thing as an effective clinical treatment. For glaucoma, researchers ultimately need evidence showing that an intervention can provide reliable, sustained pressure control and help preserve vision over time.

There is also an important distinction between lowering IOP and protecting the optic nerve. Although cannabinoid related neuroprotective effects have been proposed, there is not yet clear clinical evidence establishing that THC or cannabis prevents glaucoma-related vision loss through neuroprotection.

Was die Forschung für Cannabis bedeutet

The latest evidence adds an important piece to a decades-old scientific puzzle. THC appears capable of lowering intraocular pressure, confirming that the effect observed in earlier research is not simply a myth surrounding medical cannabis. However, the magnitude, consistency, route-dependent differences, and practical limitations make THC itself an unlikely replacement for established glaucoma medications currently.

The more compelling opportunity may be sitting inside the eye rather than inside the cannabis plant. By studying cannabinoid receptors and the signaling pathways that regulate ocular fluid dynamics, researchers may eventually develop targeted cannabinoid medicines that lower IOP without producing the psychoactive effects associated with THC. That could transform the conversation from, Can cannabis treat glaucoma? to a much more scientifically useful question, Can cannabinoid biology help scientists create better glaucoma medicines?

For now, the evidence points toward possibility rather than proof. THC can lower eye pressure, but the latest research suggests that turning that biological effect into a practical glaucoma treatment will require much more precise and much more targeted medicine.

References:

^{1. Dhivagaran T, Butt F, Mathew D Intraocular pressure-lowering effects of tetrahydrocannabinol drugs: a systematic review and meta-analysis Canadian Journal of Ophthalmology, 2026; 0 https://www.canadianjournalofophthalmology.ca/article/S0008-4182(26)00150-X/fulltext}