Dr. Shabnam Tanwar, S20170, Dr. Prakash Chipade, Dr. Abhishek Hoshing, Dr. Vijay Shetty, Dr. Suhas Haldipurkar

 

Introduction: Aberrations

Introduction

Corneal pathologies lead to astigmatism and increases higher order aberration (HOA)

Corneal astigmatism leads to substantial impairment of visual acuity and contrast sensitivity

Previous studies reported that HOAs had significant negative correlations with visual performance

Applegate RA, Hilmantel G, Howland HC et al. Corneal first surface optical aberrations and visual performance. J Refract Surg 2000;16:507–514.

Introduction

Rigid Gas Permeable Contact lens are expected to mask the anterior corneal irregularities

The refractive index similarity between the tear film and the anterior corneal surface reduces the impact of corneal aberrations

• Phillips AJ, Speedwell L. Contact Lenses, 4th ed. Oxford: Butterworth- Heinemann, 1997.
• Griffiths M, Zahner K, Collins M, Carney L. Masking of irregular corneal topography with contact lenses. CLAO J 1998;24:76–81.

Need for study

An objective assessment of optical changes produced by RGP

CL’s on the anterior surface of the cornea and total aberrations has not previously been reported

Aim

To study the changes in ocular higher order aberration with conventional RGP contact lenses (RGP)

Inclusion criteria

Corneal astigmatism of 1.00D or more in subjects with or without corneal pathologies

Exclusion criteria

Patients with Cataract &Pseudophakia

Patients with Posterior segment pathologies

Patient who refused to give consent

Material & Methods

 Study Type: A Cross sectional analysis

 Study Site: Laxmi Eye Institute, Panvel, Maharashtra

 Sample size: 24 eyes of 16 patients

Material & Methods

Ø All patients underwent comprehensive ophthalmic examination

Best corrected visual acuity by LogMAR chart

Corneal Higher order aberrations

Modulation transfer function (MTF)

Strehl’s ratio by HOYA I Trace Aberrometer

Mean visual acuity

 

Corneal Higher order Aberrations

Modulation Transfer Function (MTF)

Discussion

Rigid Gas Permeable Contact lens not only correct the corneal astigmatism but also corneal higher order aberrations

The principle of correction of corneal aberration by RGP CL’s is by acting as a  substitute for anterior surface of the cornea with a polished regular surface

Conclusion

RGP contact lens shows significant improvement in both qualitative (corneal HOAs, MTF and Strehl’s ratio and contrast sensitivity) and quantitative (mean BCVA) visual acuity in subjects with corneal astigmatism.Thank you