The study protocol adhered to the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board of L V Prasad Eye Institute, Hyderabad. All subjects participated in the study after signing a written informed consent form. For participants <18 years old, assent was obtained while the consent form was signed by a parent or local guardian. The study cohort comprised of 20 cases (9–23 years old) with clinical diagnosis of SNR-A who visited the binocular vision and orthoptics clinic of the institute between 2016 and 2021 (
Table); 91 controls with emmetropic (
n = 29; 19–32 years old), myopic (
n = 41; 20–38 years old), or hyperopic (
n = 21; 20–30 years old) spherical equivalent refraction. Emmetropia was defined here as the spherical equivalent of refraction between ±0.5D of zero refractive error. The diagnosis and management of SNR of these patients are reported in detail in Roy et al.
3 and Bharadwaj et al.
17 Briefly, diagnosis of SNR-A was confirmed by a >2.00D hyperopic shift in cycloplegic retinoscopy compared to noncycloplegic retinoscopy, with or without the disappearance of esodeviation with cycloplegia.
3,17 Additional signs of vacillating retinoscopy reflex, reduction/fluctuations in visual acuity that were not proportionate to the refractive error, were also considered.
3,17 SNR-A was managed through a combination of the modified optical fogging technique and pharmacological cycloplegia with weak and strong cycloplegics (depending on disease severity) along with vision therapy, all primarily aimed at relieving the spasm.
1,3,18 All controls underwent a comprehensive eye examination and their refractive errors, if any, were corrected with spectacles or contact lenses. These controls had high-contrast distance visual acuity better than or equal to 20/20, stereoacuity better than or equal to 40 arc sec, and binocular vision parameters within the age-matched norms described in the literature.
19 Subjects with associated ocular or systemic pathologies were excluded from the study. Presenting spherical equivalent refraction (SER) was obtained as an average of three readings from a closed-field autorefractor (Unique-RK, URK-800F, Daejeon, Republic of Korea) or from an approximate correction that resulted in a reversal of retinoscopy reflex.
3 Presenting precycloplegic visual acuity of all participants was obtained using an electronic projection chart (Complog, Ver. 1.3.25.0, London, UK).
20