[Landolt C and snellen e acuity: differences in strabismus amblyopia?]

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Visual acuity assessment relies on optotypes, but recognition varies despite similar visual angles.
• Differences in optotype recognition may be more pronounced in lower visual acuity ranges.
• This study compares visual acuity measured by Snellen E and Landolt C optotypes.

Purpose of the Study:

• To compare visual acuity measurements obtained using Snellen E and Landolt C optotypes.
• To evaluate potential differences in visual acuity assessment between these two common optotypes.
• To determine if Snellen E overestimates visual acuity compared to Landolt C, particularly in individuals with amblyopia.

Main Methods:

• 100 patients with various eye disorders (including strabismus amblyopia) and 13 healthy volunteers were tested.
• Visual acuity was assessed using Snellen E and Landolt C charts mimicking ETDRS charts.
• Participants identified 3 out of 5 optotypes per line; wrong answers were monitored.

Main Results:

• Differences between Landolt C acuity (LR) and Snellen E acuity (SE) were minimal.
• The Snellen E consistently showed slightly higher visual acuity values than the Landolt C in both the overall group and those with strabismus amblyopia.
• Mean differences were approximately 0.55 lines, indicating a slight overestimation by the Snellen E.

Conclusions:

• The Snellen E optotype leads to a slight overestimation of visual acuity compared to the Landolt C, even in cases of strabismus amblyopia.
• These minor discrepancies in visual acuity measurements should be acknowledged, especially when assessing individuals with lower visual acuity.
• The findings suggest that while differences are small, the choice of optotype can influence visual acuity outcomes.