Predicting ocular residual astigmatism using corneal and refractive parameters: a myopic eye study

Area of Science:

• Ophthalmology
• Optometry
• Vision Science

Background:

• Ocular residual astigmatism (ORA) represents the difference between total ocular astigmatism and corneal astigmatism.
• Understanding ORA is crucial for accurate refractive error correction in myopic patients.

Purpose of the Study:

• To investigate the characteristics of ocular residual astigmatism (ORA) in myopic individuals.
• To identify predictive indicators for ORA using corneal and ocular refractive data.

Main Methods:

• 356 myopic eyes from 178 patients were analyzed.
• Scheimpflug keratometry (Pentacam) and wavefront analysis (WaveScan) were employed.
• Astigmatism was analyzed using a power vector system (J0, J45), calculating ORA from vertex distance-adjusted total ocular and corneal astigmatism (anterior corneal power [ACP] and true net power [TNP]).

Main Results:

• True net power (TNP) was a more accurate measure of total ocular astigmatism compared to anterior corneal power (ACP).
• Both J0 and J45 components of ORA demonstrated significant negative correlations with corneal astigmatism (ACP and TNP).
• ORA showed negative correlation with total ocular spherical equivalent and positive correlation with total ocular astigmatism.

Conclusions:

• The study confirmed a compensatory effect of corneal astigmatism by internal optics in myopic eyes.
• True net power (TNP) provided a more accurate representation of refractive astigmatism than anterior corneal power (ACP).
• Total ocular spherical equivalent and total ocular astigmatism emerged as significant predictors for ORA.