The management of primary open-angle glaucoma and ocular hypertension has undergone a tectonic shift over the last decade. Historically, topical hypotensive medications were the undisputed first-line intervention. However, the emergence of long-term data from landmark trials has positioned Selective Laser Trabeculoplasty as a viable, and often superior, primary alternative. This review discusses the comparative effectiveness of these two modalities, focusing on intraocular pressure control, disease progression, and safety profiles.

Glaucoma is a progressive optic neuropathy characterized by the loss of retinal ganglion cells and corresponding visual field defects. As the global prevalence is projected to reach 111.8 million by 2040, identifying cost-effective and patient-centered treatment strategies is paramount [1,2]. While medical therapy has been the gold standard, issues such as poor adherence, ocular surface disease (OSD), and systemic side effects have prompted a re-evaluation of SLT as an initial treatment [3,4]. In this review, we will discuss the comparative effectiveness of these two modalities, focusing on intraocular pressure control, disease progression, and safety profiles.

The primary objective of any glaucoma therapy is the reduction of IOP to a level that prevents further axonal damage.

1.1. Efficacy of Medical Therapy

Topical prostaglandin analogs (PGAs) remain the most potent medical class, typically achieving an IOP reduction of 25-33% [5]. However, the efficacy of drops is often undermined by the "washout effect" and improper administration, leading to suboptimal 24-hour pressure control [6,7].

1.2. Efficacy of SLT

SLT utilizes a 532-nm Q-switched Nd:YAG laser to target pigmented trabecular meshwork cells without causing thermal damage to the underlying collagenous structure [8]. Meta-analyses of randomized controlled trials (RCTs) indicate that SLT provides an IOP reduction of 20-30%, which is statistically non-inferior to PGA monotherapy in treatment-naive eyes [9,10,11]. Recent longitudinal data suggests that the "success" of SLT is highly reproducible upon retreatments, though the duration of effect varies between 18 and 48 months [12,13].

Reaching a predetermined target IOP is essential for halting progression. Target Attainment; The LiGHT trial demonstrated that at 36 and 72 months, eyes treated with SLT as a primary intervention were more likely to be at target IOP without the need for additional medications compared to those starting on drops [14,15]. IOP Fluctuations; Medical therapy is susceptible to diurnal fluctuations and "troughs" when doses are missed [16]. Conversely, SLT provides a "biological" reduction that remains constant regardless of patient behavior, leading to a more stable pressure profile over time [17,18].

The long-term burden of glaucoma management is often measured by the escalation of therapy. Surgical Avoidance; Evidence suggests that primary SLT significantly reduces the long-term requirement for invasive glaucoma surgeries, such as trabeculectomy or glaucoma drainage devices [14,19]. Polypharmacy; Patients on medical therapy frequently require two or more medications to maintain target IOP within five years of diagnosis [20]. This escalation increases the risk of ocular surface toxicity and further complicates adherence [21,22].

The side-effect profiles of these two modalities represent a choice between chronic local irritation and transient procedural inflammation. Medical Therapy; Chronic use of preserved eye drops is a leading cause of Ocular Surface Disease (OSD), characterized by dry eye, hyperemia, and follicular conjunctivitis [23,24]. Systemic absorption of beta-blockers can lead to bradycardia and bronchospasm, while PGAs are associated with prostaglandin-associated periorbitopathy (PAP) [25,26]. SLT; The procedure is generally well-tolerated. The most common adverse events include transient IOP spikes (usually <5>

The ultimate clinical metric is the preservation of the visual apparatus.

5.1. Visual Field (VF) Changes

Long-term observational studies have found that the rate of VF mean deviation (MD) progression is slower in patients who receive SLT early in their disease course [29]. This is likely due to the elimination of the "adherence gap" inherent in medical therapy [30].

5.2 Optic Nerve Head (ONH) and OCT Parameters

Optical Coherence Tomography (OCT) allows for precise monitoring of the Retinal Nerve Fiber Layer (RNFL) and the Ganglion Cell Complex (GCC). RNFL Thinning; Research indicates that eyes managed with SLT exhibit a more stable RNFL profile over 5-year periods compared to those managed with multi-drug medical therapy [31,32]. Vascular Parameters; Recent OCT-Angiography (OCT-A) studies suggest that the reduction in IOP following SLT may improve peripapillary vessel density, potentially offering a neuroprotective benefit beyond simple pressure lowering [33,34].

The paradigm for glaucoma management is shifting toward early laser intervention. SLT offers a "medication-free" window that preserves the ocular surface, ensures 24-hour IOP stability, and slows the rate of structural and functional progression. While medical therapy remains a vital component of the armamentarium, its limitations regarding adherence and toxicity make SLT a compelling first-line choice in the modern era.