SLT laser or eye drops first? What the LiGHT trial found

A large trial compared starting glaucoma treatment with a quick office laser versus daily drops. The results changed guidelines.

Written by Dr. M. Ali Tawfik Alyouzbaki, MD, OphthalmologistLast updated Sources citedEditorial policy

Treatment, 6 min read. Published .

Key points

  • SLT controlled pressure as well as drops over three years.
  • About 74% of people who started with SLT needed no drops at three years.
  • No one in the SLT group needed glaucoma surgery.
  • The 2026 AAO guideline endorses SLT as a first-line option.

Two ways to start

For open-angle glaucoma and high eye pressure, the first treatment has long been a daily eye drop. Selective laser trabeculoplasty, or SLT, is a quick office laser treatment of the eye's drainage tissue that also lowers pressure. The question many people ask is which should come first.

What the LiGHT trial tested

The LiGHT trial, run at hospitals across the United Kingdom, randomly assigned people with newly diagnosed open-angle glaucoma or ocular hypertension to start with either SLT or drops, and followed them for three years.[1]

What it found

  • Pressure control was similar. About 93% of visits in the SLT group were at target pressure, compared with about 91% in the drops group.[1]
  • Most SLT patients stayed drop-free. At three years, about 74% of people who started with SLT needed no drops to stay at target.[1]
  • No glaucoma surgery in the SLT group. Eleven eyes in the drops group needed a trabeculectomy.[1]
  • Few safety problems. There were no sight-threatening complications from SLT. About a third had short-lived discomfort, blur or redness after treatment.[1]

Quality-of-life scores were similar in both groups, and starting with SLT was likely to cost the eye service less.[1]

What guidelines say now

The American Academy of Ophthalmology's 2026 guideline for open-angle glaucoma endorses SLT as a first-line therapy, alongside medicines.[2]

Which is right for you

Drops remain an excellent choice for many people. SLT may suit you better if drops are hard to put in, cause side effects, are expensive, or if you'd rather not depend on a daily routine. The effect of SLT can fade over years, and it can be repeated. SLT is not used to open a closed angle; that needs a different laser.[3]

When to see a doctor

Talk to your eye doctor if drops are hard to use, cause side effects, or cost too much. Don't stop drops on your own.

Emergency: If you have sudden eye pain with redness, blurred vision, halos around lights, headache, nausea or vomiting, or sudden vision loss or a curtain over your vision, go to an emergency department now or call 911.

Sources and references

  1. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al; LiGHT Trial Study Group. Selective laser trabeculoplasty versus eye drops for first-line treatment of ocular hypertension and glaucoma (LiGHT): a multicentre randomised controlled trial. Lancet. 2019;393(10180):1505-1516. View source
  2. Gedde SJ, Bowden EC, Challa P, et al; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Committee. Primary Open-Angle Glaucoma Preferred Practice Pattern. Ophthalmology. 2026;133(4):P1-P103. doi:10.1016/j.ophtha.2025.12.029 View source
  3. Gedde SJ, Chopra V, Vinod K, et al; American Academy of Ophthalmology Preferred Practice Pattern Glaucoma Committee. Primary Angle-Closure Disease Preferred Practice Pattern. Ophthalmology. 2026;133(4):P153-P201. doi:10.1016/j.ophtha.2025.12.030 View source

Dr. M. Ali Tawfik Alyouzbaki, MD, Ophthalmologist. Ophthalmologist with a focus on glaucoma, seeing patients in St. Cloud, Florida.

About the author, editorial policy

This article is general education for adults and is not a substitute for personal medical advice.

More articles