Structure-Function Analysis of Tilted Disc Syndrome Reveals the Optimal Negative Addition Lens for Eliminating Refractive Scotomas

Abstract

Purpose: Patients with tilted disc syndrome (TDS) may present with visual field defects (VFDs) resembling pathological patterns of loss due to the location of the posterior retinal bowing. We determined the optimum negative addition lens (NAL) by examining the retinal structure to eliminate refractive VFDs, and hence to help differentiate TDS from potentially sinister pathologies.

Methods: 10 patients with TDS and 3 patients with neurological VFDs due to retrograde degeneration underwent testing on the Humphrey Field Analyzer 30-2 test pattern using the SITA-Standard paradigm. Four refractive corrections were used: normal correction as recommended by the instrument, or a -1D, -2D and -3D NAL on top of their refractive error. Peripheral retinoscopy was performed to ascertain refractive errors at different horizontal eccentricities. B-scan ultrasound was performed to visualize the posterior retinal bowing, and to estimate the amount of refractive correction required to eliminate the VFD. VFDs were assessed qualitatively and quantitatively using thresholds and probability scores.

Results: Qualitatively, NALs reduced the extent and depth of the VFDs in patients with TDS, but not in those with retrograde degeneration. There was a correlation between residual refractive error (following the use of NALs) and the improvement in VFD in terms of threshold values (p=0.0145) and probability scores (p=0.0003) in patients with TDS. A greater proportion of points showed improvement in both threshold and probability score when the residual refraction was within 0.75D (55.4%) compared to residuals of ≥1D (27.9%, p

Conclusion(s): Examining peripheral refraction and ocular structure can guide NAL selection to optimally reduce the refractive VFDs in patients with TDS. This offers a potential method for differentiating between refractive and true pathological VFDs.