Prism under cover test in alternate fixation horizontal strabismus

Area of Science:

• Ophthalmology
• Pediatric Ophthalmology
• Strabismus Management

Background:

• Assessing manifest deviation in pediatric horizontal strabismus is crucial for diagnosis and management.
• The simultaneous prism and cover test (SPCT) is a standard method, but its feasibility can be limited in certain pediatric cases.
• The prism under cover test (PUCT) offers a potential alternative for quantifying deviations.

Purpose of the Study:

• To evaluate the clinical applicability of the prism under cover test (PUCT) for measuring manifest horizontal strabismus in children.
• To determine if PUCT can be reliably used when the simultaneous prism and cover test (SPCT) is not feasible.
• To assess the correlation of PUCT with other measures like stereoacuity and compare it with SPCT and alternate prism and cover test (APCT).

Main Methods:

• A study involving children aged 4-11 years with alternate fixation horizontal strabismus.
• Participants were divided into two groups: SPCT not feasible (n=18) and SPCT feasible (n=24).
• Measurements included refraction, PUCT, APCT, fusion, stereoacuity, and analysis of PUCT repeatability and agreement with SPCT.

Main Results:

• In the group where SPCT was not feasible, PUCT showed good repeatability (coefficient of repeatability: 3.4 PD) and a strong intraclass correlation (ICC: 0.90) with APCT.
• In the group where SPCT was feasible, PUCT demonstrated high agreement with SPCT (concordance correlation coefficient: 0.91).
• PUCT showed a better correlation with stereoacuity (0.78) compared to APCT (0.58) in the second group.

Conclusions:

• The prism under cover test (PUCT) is a repeatable procedure suitable for estimating manifest deviation in children with horizontal strabismus.
• PUCT is particularly valuable when the simultaneous prism and cover test (SPCT) cannot be performed.
• The findings support the use of PUCT in diagnosing conditions like monofixation syndrome.