Spasm of Near Reflex: Objective Assessment of the Near-Triad

Abstract

To characterize binocular steady-state accommodation, pupil and convergence responses (near triad) in spasm of near reflex (SNR) before and after optical and pharmacological intervention. To identify the putative source of SNR in the neural control schema of accommodation-vergence interaction using controls-engineering modeling. METHODS. Near-triad of 15 patients with SNR (9 to 23 years) was recorded using an infrared photorefractor at 2m viewing distance for 120s during clinical presentation, after optical fogging intended to relieve spasm, with cycloplegia, post-cycloplegia and longterm follow-up visits. Data were also collected without cycloplegia in 15 age-matched controls. Schor (1999) model was used to computationally simulate accommodation and vergence responses of controls and SNR. RESULTS. Both eyes of SNR exhibited significant myopia and refraction fluctuations (<1.0Hz) during clinical presentation [median (25 th to 75 th IQR) refraction: −1.7D (−3.2 to −0.8D); root mean squared (RMS) deviation: 1.1D (0.5 to 1.5D)], relative to controls [0.8D (−0.03 to 1.4D); 0.2D (0.1 to 0.3D)] (p < 0.001). These decreased after optical fogging, largely eliminated with cycloplegia and partially reappeared in the postcycloplegia and follow-up visits. SNR responses could be modeled by increasing the gain and decay time of tonic accommodation, vis-à-vis, controls. Pupil and convergence responses in SNR were similar to controls at all visits (p > 0.1). CONCLUSIONS. Exaggerated fluctuations of steady-state accommodation may be a signature feature of SNR, even while their pupil and convergence responses may remain unaffected. These fluctuations may arise from the tonic accommodation controller, the properties of which could be potentially altered after optical fogging to relieve the disorder.

Accommodative spasm and its different treatment approaches: A systematic review

“…If a post-cycloplegic spasm develops, the author suggests using a modified fogging technique to improve accommodation stability and visual acuity. 8 Roy et al suggested using the modified optical fogging method or one-time cycloplegic drops to evaluate actual refractive error and alleviate the near reflex spasm. In a cohort study, the author treated 66% of patients with mild spasm of the near reflex, 22% of patients with moderate spasm of the near reflex, and 13% of patients with severe spasm of the near reflex.…”

“…3,32 Three studies compared the modified optical fogging technique with cycloplegic refraction and applied it as a method to stop the accommodative spasm when it was noticed after post-cycloplegic refraction. 8,36,38 The method involves requiring the patient to perform a close task while stabilising the patient's visual acuity and retinoscopy reflex. Satgunam reports that the two patients diagnosed with accommodative spasm after cycloplegic refraction used the modified optical fogging method to immediately relieve the spasm.…”

“…The symptoms of accommodative spasm include variations in visual acuity, inconsistent retinoscopy findings, unpredictable refractive error, lead of accommodation in dynamic retinoscopy, and asthenopic symptoms. 8…”

“…6 The symptoms of accommodative spasm include variations in visual acuity, inconsistent retinoscopy findings, unpredictable refractive error, lead of accommodation in dynamic retinoscopy, and asthenopic symptoms. 8 The mechanism that causes accommodative spasms is still unknown. It manifests as pseudo myopia due to ciliary muscle spasm, convergent strabismus, or miosis caused by parasympathetic eye stimulation of the eye.…”

Is Ocular Accommodation Influenced by Dynamic Ambient Illumination and Pupil Size?

“…When fixation switches from a distant object to a near object, the near-reflex response, including ocular accommodation, convergence and pupil contraction, is elicited to achieve and maintain clear single-binocular vision [ 8 ]. When changing our focus from a near target to a distant target, the reverse response occurs, including ocular disaccommodation, divergence and pupil mydriasis.…”