Normal values for photopic and mesopic letter contrast sensitivity

Area of Science:

• Ophthalmology
• Vision Science

Background:

• Refractive surgery is increasing, leading to more patients experiencing night vision disturbances like reduced contrast sensitivity.
• Standard contrast sensitivity scales for normal individuals in the mesopic range are lacking.

Purpose of the Study:

• To establish normal Pelli-Robson contrast sensitivity values under photopic and mesopic conditions in a large Spanish population across various age groups.
• To evaluate the influence of photopic visual acuity on both photopic and mesopic contrast sensitivity.

Main Methods:

• A cross-sectional study involving 292 participants, stratified into six age groups.
• Binocular contrast sensitivity was measured using the Pelli-Robson letter chart at 1 meter under photopic (85 cd/m2) and mesopic (0.15 cd/m2) luminance conditions with best spectacle correction.

Main Results:

• Contrast sensitivity began decreasing earlier in mesopic (51-60 years) than photopic (61-70 years) conditions.
• Mean contrast sensitivity reduction between the oldest and youngest groups was 0.20 log units (photopic) and 0.33 log units (mesopic).
• Higher photopic visual acuity correlated with significantly improved both photopic and mesopic contrast sensitivity.

Conclusions:

• Mesopic contrast sensitivity declines approximately one decade earlier than photopic sensitivity and is influenced by visual acuity.
• Establishing normal mesopic contrast sensitivity values is crucial for differentiating normal function from pathological decreases.