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Assessing the visual image quality provided by refractive corrections during keratoconus progression.

Jos J Rozema^1,2, Gareth D Hastings^3,4, Marta Jiménez-García^1,2

¹Department of Ophthalmology, Antwerp University Hospital, Edegem, Belgium.

Ophthalmic & Physiological Optics : the Journal of the British College of Ophthalmic Opticians (Optometrists)

|December 11, 2021

Summary

This study expanded the SyntEyes keratoconus model to assess visual image quality (VIQ) with disease progression. Rigid contact lenses offer better, more stable VIQ in keratoconus than spectacles as the condition worsens.

Keywords:

keratoconus keratoconus progression refractive correction rigid lens statistical eye model subjective refraction

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Area of Science:

Ophthalmology
Optometry
Computational modeling

Background:

Keratoconus (KTC) is a progressive eye condition causing irregular astigmatism.
Accurate correction of visual acuity is challenging in advanced KTC.
Existing eye models require enhancement to simulate disease progression's impact on visual correction.

Purpose of the Study:

To expand the SyntEyes keratoconus (KTC) model for assessing visual image quality (VIQ).
To evaluate spectacle and rigid contact lens corrections in KTC as the condition progresses.
To understand how KTC progression affects the efficacy of different visual corrections.

Main Methods:

The previously validated SyntEyes KTC eye model was enhanced to incorporate KTC progression.
The model simulated the visual performance of spectacle and rigid contact lens corrections.
Visual Strehl ratio (VSX) patterns were analyzed in correction space.

Main Results:

Spectacle correction patterns shifted from hourglass to shell patterns with KTC progression, becoming less sensitive to refractive changes.
In some cases, spectacle correction showed two foci with similar, lower VIQ.
Rigid contact lenses provided significantly better visual acuity gains (5.5 lines logMAR) compared to spectacles (3.5 lines logMAR).
Spectacle correction VIQ degraded to near uncorrected levels with KTC progression, while rigid contact lens VIQ remained relatively stable.

Conclusions:

Subjective refraction is difficult in highly aberrated keratoconic eyes.
The visual benefits of spectacle correction are temporary as KTC progresses.
Rigid contact lenses offer superior and more stable visual image quality throughout KTC progression.
Further clinical validation is needed for specific findings like the dual-focus phenomenon.