Sensitivity and Specificity of Sheard and Percival’s Criteria for the Diagnosis of Young People with Near-heterophoria

Abstract

BACKGROUND: Sheard and Percival assumed that symptoms from latent strabismus can be avoided if the relevant fusional vergence is adequate to support the heterophoria. AIM: The aim of the study was to determine the sensitivity and specificity of Sheard’s and Percival’s criterion for the diagnosis of heterophoria. METHODS: A cross-sectional hospital-based study was performed at Al-Neelain Eye Hospital Khartoum, Sudan from February to October 2019. Heterophoria was measured using Maddox Wing and fusional vergence using a prism bar. Thereafter, Sheard’s and Percival’s criteria were used for the diagnosis of heterophoria. RESULTS: A total of 230 participants (age = 15–30 years; mean age = 19.34 ± 3.325 years) were recruited for this study. The Sheard’s criteria showed a high sensitivity of 87.2% and a low specificity of 8.0% for the diagnosing of exophoria, with positive and negative predictive values of 65.5% and 26%, respectively. The criteria showed a relatively low sensitivity of 77.8% and a specificity of 9.0% in the diagnosis of esophoria, with a positive and negative predictive values of 56% and 20%, respectively. Percival criteria showed high sensitivity 84.2% and low specificity 9.1% in diagnosing esophoria, with a positive and negative predictive value of 61.5% and 25%, respectively. On the other hand, the criteria showed low sensitivity 67.4% and specificity 13.8% in diagnosing exophoria, with positive and negative predictive value 61.9% and 17%, respectively. CONCLUSION: Sheard’s and Percival’s criteria are useful in diagnosing binocular vision problems. Sheard’s criteria are accurate in diagnosing near exophoria and Percival’s criteria are more accurate in diagnosing near esophoria. Therefore, these criteria provide good clues and predictions for the diagnosis of binocular vision problems.

Binocular vision parameters and visual performance in bilateral keratoconus corrected with spectacles versus rigid gas-permeable contact lenses

“…Sheard's criterion postulates that "for a subject to have comfortable binocular vision, the value of the fusional reserve must be at least twice the demand; in this sense, phoria would be considered compensated with fusional reserves”. 16 Based on the above statement, 82.5 % of patients evaluated presented compensated phoria with spectacles; however, with RGP contact lenses there was only 42.50 % of patients preserving this compensation. ( Table 3 )…”

Heterophoria, fusional vergence, and near point of convergence in Sudanese hospital-based population

“…Our findings largely agreed with earlier studies. 10,12,21 Positive fusional vergence helps to control exophoria, which is a tendency for the eyes to deviate outwards, while NFV helps control esophoria, which is a tendency for the eyes to drift inwards.…”

“…7 Normal binocular vision needs correct alignment of both eyes, in addition to motor and sensory mechanisms of fusion. 9,10 Positive fusional vergence (PFV) and negative fusional vergence (NFV) are stimulated by retinal disparity aimed at maintaining binocular single vision. 9,10 Heterophoria can appear when the PFV or NFV is interrupted because the tendency for eye deviation is kept latent by fusional vergence (FV) amplitude.…”

“…9,10 Positive fusional vergence (PFV) and negative fusional vergence (NFV) are stimulated by retinal disparity aimed at maintaining binocular single vision. 9,10 Heterophoria can appear when the PFV or NFV is interrupted because the tendency for eye deviation is kept latent by fusional vergence (FV) amplitude. 11 Maintaining compensation for heterophoria is attributed to FV, making it crucial for eye care professionals to determine the amount of total vergence amplitude necessary to control a deviation.…”

“…The author supposed that complaints from heterophoria could be avoided if the FV in the opposite direction is at least twice the size of the heterophoria. 1,10,13 Near point of convergence (NPC) has been considered an essential factor in assessing the vergence system at near fixation distances and the previous study showed that NPC tends to recede with increasing age. 14 This study was conducted to investigate the relationships between heterophoria, step fusional vergence (SFV) and NPC among Sudanese participants with near heterophoria.…”