Analysis of alphabet patterns of deviations found in patients without strabismus in primary position

Abstract

Aim: To detect alphabet patterns in a group of patients without strabismus and to determine whether they induced any convergence insufficiency type symptoms. Methods: Data on subjective refraction, distance and near heterophoria, distance and near positive fusional vergence (BO), near point of convergence (NPC), measurements of upgaze and downgaze made 45° above and below the primary position with alternate cover test and a prism bar at a distance of 37.5 cm, were collected from participants of two clinics. Symptoms were assessed using the 15-item Convergence Insufficiency Symptoms Survey (CISS) to determine a symptom score. Association between alphabet patterns and the other variables was analyzed using parametric and non-parametric tests. Results: Out of 122 patients, 14 were found to present an alphabet pattern. Defining a V pattern exophoria ≥15–prism dioptre or ≥10–prism dioptre deviation, three patients (2.5%) and 12 patients (9.8%) were identified, respectively. In addition, one case resembled an X pattern and another a diamond pattern. The refraction, distance and near heterophoria, positive fusional vergence and CISS scores were not significantly different in the participants with V pattern compared to those without V pattern. Conclusion: Alphabet patterns, especially V type, were demonstrated in approximately 11.5% of a sample of 122 non-strabismus patients. These alphabet patterns were found not to be associated with convergence insufficiency-like symptoms.