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Related Experiment Video

Updated: May 17, 2026

$Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter$

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Corneal refractive index-hydration relationship by objective refractometry.

Sudi Patel¹, Jorge L Alió

¹Development and Innovation Department, VISSUM, Instituto Oftalmologico de Alicante, Alicante, Spain.

Optometry and Vision Science : Official Publication of the American Academy of Optometry

|October 17, 2012

Summary

The objective VCH-1 refractometer shows good agreement with the manual subjective Abbé refractometer for measuring corneal refractive index (RI). Refractive index (RI) and hydration (H) have a significant relationship, but current models may not accurately predict anterior corneal stroma RI.

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Area of Science:

Ophthalmology
Biomedical Optics
Corneal Physiology

Background:

Accurate measurement of corneal refractive index (RI) is crucial for understanding corneal hydration and optical properties.
The relationship between refractive index and hydration in the corneal stroma requires precise quantification.

Purpose of the Study:

To compare the VCH-1 objective refractometer with the manual subjective Abbé refractometer (MSAR) for corneal stroma RI measurements.
To evaluate the refractive index (RI)-hydration (H) relationship in the corneal stroma.

Main Methods:

Ovine corneal buttons were used, with epithelial and endothelial layers removed.
Refractive index (RI) was measured using both MSAR and VCH-1.
Samples were dehydrated under controlled conditions, with RI and hydration (H) measured at multiple stages.

Main Results:

The VCH-1 showed good agreement with MSAR, with a small average difference in RI measurements (0.00071).
A significant linear regression relationship was found between RI and the reciprocal of hydration (H) for both anterior and posterior corneal stroma.
Anterior stroma RI was consistently higher than posterior stroma RI, indicating lower hydration.

Conclusions:

The VCH-1 is a reliable instrument for measuring corneal RI, comparable to MSAR.
The study established a quantitative RI-H relationship for corneal stroma, with differences noted between anterior and posterior regions.
Existing predictive models for RI from H are more applicable to the posterior stroma than the anterior stroma.