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$Subjective Refraction Test Using a Smartphone for Vision Screening$

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The association between residual astigmatism and refractive errors in a population-based study.

Hassan Hashemi¹, Mehdi Khabazkhoob, Alireza Peyman

¹Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.

Journal of Refractive Surgery (Thorofare, N.J. : 1995)

|June 27, 2013

Summary

Spherical equivalent (SE) increases correlate with higher refractive and residual astigmatism in myopia and hyperopia. With-the-rule residual astigmatism is more common in emmetropes, unlike refractive astigmatism.

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Area of Science:

Ophthalmology
Optometry
Vision Science

Background:

Astigmatism is a common refractive error that affects visual acuity.
Spherical equivalent (SE) is a measure of overall refractive error.
Understanding the relationship between SE and different types of astigmatism is crucial for accurate diagnosis and management.

Purpose of the Study:

To investigate the association between spherical equivalent (SE) and refractive, corneal, and residual astigmatism.
To analyze how SE changes with varying levels and types of astigmatism in a large population.

Main Methods:

A large-scale study involving 6,311 participants using stratified cluster sampling.
Comprehensive eye examinations including visual acuity, refraction, and keratometry.
Calculation of refractive astigmatism, corneal astigmatism, and residual astigmatism from collected data.

Main Results:

Refractive astigmatism demonstrated a U-shaped relationship with SE, with higher SE in myopes and hyperopes.
Increased residual astigmatism was linked to myopic shifts in myopes and hyperopic shifts in hyperopes.
With-the-rule (WTR) astigmatism was most prevalent in cases with higher SE, while against-the-rule (ATR) and oblique astigmatism increased with higher SE errors.

Conclusions:

Higher SE is associated with increased refractive and residual astigmatism in both myopic and hyperopic individuals.
Residual astigmatism, particularly WTR, is more frequently observed in individuals with near-emmetropic SE.
These findings contribute to a better understanding of astigmatism's impact on overall refractive error.