Abstract
Purpose :
Standardized short duration transient visual evoked potentials (SDT-VEP) are a clinically validated objective means of identifying early stage optic nerve dysfunction. In glaucomatous optic neuropathy, functional changes detected by VEP likely precede structural changes in retinal nerve fiber layer (RNFL), optic nerve head (ONH) cupping, and field loss, providing an early treatment window. Previously, we reported that only 40% of glaucoma patients with prolonged VEP latency had normalization following selective laser trabeculoplasty (SLT). Here, we ask whether capacity to normalize was influenced by ONH cupping, RNFL thickness, or systemic hypertension. Furthermore, we assessed whether normalization of VEP correlated with improvement in microperimetry, dependence on medications and reduction of IOP.
Methods :
We performed a retrospective review of 159 patient charts (229 eyes) treated with 360-degree SLT. We compared clinical parameters before and four to seven months after SLT to determine whether normalization of VEP was affected by history of hypertension, degree of optic nerve head cupping, or RNFL density. We analyzed microperimetry, IOP, and medication use in treated patients to see if they were influenced by those risk factors. South Bay Retina, Inc. Ophthalmology Clinic permitted use of anonymous clinical data.
Results :
Of the 229 eyes treated, 56% of eyes had normalization of VEP. Degree of cupping, RNFL thickness, and history of hypertension did not appear to affect capacity to normalize. Treatment with SLT resulted in an average IOP reduction from 13.3 to 12.2, reduction in number of medications in 21% of patients, and improvement in central visual field in 30% of patients.
Conclusions :
Normalization of VEP may only be possible in earlier stages of glaucoma. Use of VEP to identify early stage glaucoma provides an opportunity for earlier intervention enabling normalization of nerve function with SLT. Ocular hypotensive agents can lower IOP but have not been shown to improve optic nerve function. The improvement observed in patients via microperimetry is consistent with restored nerve function. The durability of these changes to nerve function over longer periods of time requires further study. A larger study would help to better understand limits for reversibility of nerve function via SLT.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.