Damage to Disposable Lens During Selective Laser Trabeculoplasty: Factors and Associated Clinical Outcomes

Abstract

Purpose : Disposable selective laser trabeculoplasty (SLT) lenses have become a mainstay in clinical practice due to concerns about appropriate sterilization of reusable lenses. While the optical quality of disposable lenses can be lower than reusable lenses, their effect on treatment outcomes has not been studied. In particular, disposable SLT lenses can be damaged during use by the laser, potentially affecting therapy. The purpose of this study was to identify factors associated with the magnitude of lens damage and its effect on treatment outcomes.

Methods : We analyzed 113 eyes from 82 patients who underwent SLT between 2020-2021. For each procedure, we recorded baseline patient characteristics, procedure settings (energy, number of applications, slit lamp used), and area of lens damage (laser-induced etching of the lens mirror coating; calculated using digital photos and MATLAB; Fig 1). Treatment response was calculated as the difference between pre- and post-op intraocular pressure (IOP). Physician age (n=8, range 29-53 yrs) was assessed as a possible factor causing laser defocus due to accommodation. Statistical significance of correlations was assessed using generalized estimating equations since both eyes of 31 patients were included.

Results : Area of lens damage was associated with greater total laser energy (r = 0.34, p < 0.001; Fig 2A) and greater mean energy per application (r = 0.37, p < 0.001; Fig 2B). IOP reduction decreased with increasing lens damage (r = -0.19, p < 0.022; Fig 2C). Lens damage was not associated with patient characteristics indicative of glaucoma severity or user settings (physician age, slit lamp used).

Greater IOP reduction was associated with higher pre-op IOP (r = 0.46, p < 0.001) and a smaller cup-to-disc ratio (r = 0.22, p < 0.036). IOP reduction was not associated with glaucoma severity, patient age, or the number of glaucoma medications.

Conclusions : Increased laser damage to disposable SLT lenses was associated with diminished treatment effect. The amount of damage was correlated with total and average laser energy, but not patient or physician factors.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Figure 1: Percent lens damage. The treatment lens was manually isolated (red) and regionally binarized so that damaged pixels were 1 and undamaged pixels were 0. Percent area damage = damaged pixels/ total pixels in treatment lens.

 

Figure 2: Results of analysis.