Glaucoma is the most common cause of irreversible blindness worldwide, with management options targeted at reducing IOP.1 Reduction is achievable through myriad treatments—including topical and oral medications, incisional surgeries, and laser-based modalities—but the surge of minimally invasive glaucoma surgeries (MIGS) raises new questions regarding the reliance of the traditional gold standards.
With so many options at their disposal, ophthalmologists must continually evaluate the role of each procedure to determine the safest and most effective path forward for patients.
Pinpointing the obstruction
One of the most important challenges that glaucoma surgeons face is determining the best procedure for each patient. The outflow system is multifaceted, with potential blockages occurring in the trabecular meshwork, Schlemm’s canal, or the collecting ducts.
With so many customized treatment options, one thought is whether ophthalmologists could better deduce the location of outflow blockage through selective laser trabeculoplasty (SLT). SLT works through selective photothermolysis of the pigmented trabecular meshwork cells.
A study analyzing the microarchitecture of Schlemm’s canal before and after SLT showed that the degree of canal expansion positively correlates to the degree of IOP reduction in glaucoma patients. The authors postulated this correlation provided direct evidence for the structural effect of SLT on the trabecular meshwork, in addition to the ability of SLT to increase trabecular aqueous outflow.2
Since SLT effectively and selectively treats blockages localized to the trabecular meshwork, its outcome provides invaluable information regarding the patient’s pathology.
A successful SLT can determine that the primary obstruction is most likely within the targeted trabecular meshwork. Alternatively, a minimally effective SLT procedure would find that the main obstruction most likely lies outside the meshwork.
The benefits of this diagnostic information are manifold. However, the greatest benefit tailors to individualized treatment. The information provided by SLT may help select future procedures based on the ability to selectively target the problem areas.
A patient with a fairly unsuccessful SLT most likely has a predominant blockage outside of the trabecular meshwork, and should therefore undergo a MIGS procedure that can effectively treat Schlemm’s canal and the collecting ducts. Ab-interno canaloplasty (ABiC) may be the next best step in such a patient.
The comprehensive approach of ABiC removes a lot of the guesswork from the planning of a customized treatment plan for each patient, with the potential to decrease the number of procedures and increase the effectiveness of their management overall.