Lanthony's new color test--part III. The neutral zone

Area of Science:

• Ophthalmology
• Neuro-ophthalmology
• Genetics

Background:

• Dyschromatopsias, or color vision defects, can be hereditary or acquired, impacting daily life and diagnosis.
• The neutral zone, a region where colors are indistinguishable, is a key indicator in color vision testing.
• Understanding the neutral zone's characteristics in different dyschromatopsias aids in diagnosing and managing visual impairments.

Purpose of the Study:

• To investigate the presence and characteristics of the neutral zone in hereditary and acquired dyschromatopsias using the New Color Test (NCT).
• To determine the occurrence of acquired type III blue-yellow defects with a neutral zone in specific ocular pathologies.
• To analyze the progression of the neutral zone in retinitis pigmentosa, particularly its relationship with declining visual acuity.

Main Methods:

• Utilized the New Color Test (NCT) to assess the neutral zone in patients with various forms of dyschromatopsia.
• Documented the presence of acquired type III blue-yellow defects with a neutral zone in conditions including optic nerve atrophy, macular edema, choroidal atrophy, myopia, glaucoma, and retinitis pigmentosa.
• Correlated the neutral zone findings with visual acuity measurements in retinitis pigmentosa patients, excluding autosomal dominant inherited cases.

Main Results:

• Acquired type III blue-yellow defects with a neutral zone were observed in a range of conditions affecting the optic nerve and retina.
• These conditions included optic nerve atrophy, edematous maculopathies, choroidal atrophy, myopia, glaucoma, and retinitis pigmentosa.
• In retinitis pigmentosa (excluding autosomal dominant forms), a type III neutral zone was found to be complicated by a type I neutral zone as visual acuity decreased to 0.2.

Conclusions:

• The New Color Test (NCT) is effective in identifying and characterizing neutral zones in diverse dyschromatopsias.
• The presence of acquired type III blue-yellow defects with a neutral zone is indicative of significant retinal or optic nerve compromise.
• The evolution of neutral zone patterns in retinitis pigmentosa correlates with disease progression and visual acuity loss.