From monocular photograph to angle lambda: A new clinical approach for quantitative assessment

Area of Science:

• Ophthalmology
• Pediatric Ophthalmology
• Strabismus Diagnosis

Background:

• Angle lambda assessment is vital in pediatric and strabismus practice.
• Abnormal angle lambda can alter or mimic strabismus.
• Current assessment methods using corneal topographs have limited clinical accessibility.

Purpose of the Study:

• To introduce an easy, low-cost, and reproducible method for angle lambda quantification.
• To validate the method's repeatability and compare it with existing assessments.

Main Methods:

• Monocular photographs were taken using a ring flash camera centered on a fixation point.
• Digital analysis evaluated the corneal reflex position relative to pupil diameter.
• A trigonometric formula converted the ratio to angle lambda values.

Main Results:

• The method demonstrated high repeatability (Lin's coefficient = 0.99) in healthy eyes.
• Mean angle lambda values were consistent across repeated measurements (+2.61° ± 2.92° and +2.63° ± 2.85°).
• The photographic method showed minimal deviation (-0.071°) compared to Pentacam assessment.

Conclusions:

• This photographic technique provides a viable, accessible tool for angle lambda assessment.
• It is suitable for use in strabismus and pediatric clinics, offering an alternative to specialized devices.