Functional evaluation of the macular area in early glaucoma using microperimetry

Area of Science:

• Ophthalmology
• Neuroscience

Background:

• Glaucoma is a progressive optic neuropathy characterized by visual field loss.
• Early detection of glaucomatous damage is crucial for timely intervention and vision preservation.
• Standard automated perimetry (SAP) is a common tool, but may miss subtle central visual field defects.

Purpose of the Study:

• To evaluate the utility of microperimetry (MP) in assessing the central visual field in patients with early glaucoma.
• To compare the sensitivity of MP with SAP in detecting glaucomatous visual field defects.

Main Methods:

• Consecutive patients with early glaucoma (single nasal step or arcuate scotoma on SAP) and healthy controls underwent MP.
• Retinal sensitivity was mapped within the central 10° of fixation.
• MP data was analyzed for frequency and depth of sensitivity loss.

Main Results:

• Microperimetry detected significant loss of retinal sensitivity in early glaucomatous eyes compared to controls (mean sensitivity 11.8 dB vs 16.6 dB, P=0.0004).
• Absolute scotomas were observed in 14-28% of eyes with nasal step defects and 95% of eyes with arcuate defects, often located 6-10° from fixation.
• Even areas appearing normal on SAP showed mild defects on MP in 43% of glaucomatous eyes.

Conclusions:

• Microperimetry is a sensitive tool for detecting central visual field loss in early glaucoma, often revealing defects missed by SAP.
• Paramacular absolute defects, occurring 6-10° from fixation, are significant findings in early glaucomatous neuropathy detected by MP.