Sains Malaysiana 49(6)(2020): 1431-1437

http://dx.doi.org/10.17576/jsm-2020-4906-21

 

Accuracy of Contact Lens Method by Spherical and Aspheric Rigid Gas Permeable Lenses on Corneal Power Determination in Normal Eyes

(Ketepatan Kaedah Kanta Sentuh dengan Kanta Sfera dan Asferik Gas Tegar Boleh Telap ke atas Penentuan Daya Kornea pada Mata Normal)

 

MD MUZIMAN SYAH MD MUSTAFA1*, HALIZA ABDUL MUTALIB2, NOORHAZAYTI AB. HALIM3 & MOHD RADZI HILMI1

 

1Department of Optometry and Visual Science, Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang Darul Makmur, Malaysia

 

2Optometry and Visual Science Programme, School of Healthcare Sciences, Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 UKM Kuala Lumpur, Federal Territory, Malaysia

 

3Department of Paediatric Dentistry and Dental Public Health, Kulliyyah of Dentistry, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang Darul Makmur, Malaysia

 

Diserahkan: 8 Oktober 2019/Diterima: 2 Februari 2020

 

ABSTRACT

Contact lens method (CLM) is an alternative option to measure corneal power by evaluating the difference of patient’s over-refraction with rigid gas permeable (RGP) lens to manifest refraction. The purpose of this study was to evaluate the accuracy of CLM using spherical (CLMspherical) and aspheric (CLMaspheric) RGP lenses in measuring corneal refractive power of normal corneas. This prospective study recruited 45 normal eyes of 45 healthy subjects. The corneal power measurements were determined by CLMspherical using Boston ES RGP and CLMaspheric using Boston Envision RGP based on alignment fitting strategy. Manifest refraction and over-refraction were determined using a standard procedure of objective and subjective refraction methods. IOLMaster was set as the reference method for comparison. The mean arithmetic difference, mean absolute difference and 95% limits of agreement (LOA) of corneal powers obtained from CLMspherical and CLMaspheric to IOLMaster value were evaluated for the accuracy assessment. The mean arithmetic difference and mean absolute difference of corneal power s obtained from CLMspherical and CLMaspheric to IOLMaster values were 0.10 ± 0.21 D and 0.20 ± 0.11 D, and 0.04 ± 0.09 D and 0.08 ± 0.05 D, respectively. The 95% LOA between CLMspherical and IOLMaster ranged from -0.30 to 0.51 D, whereas between CLMaspheric and IOLMaster was ranging from -0.14 to 0.21 D. CLM in estimating corneal power is more accurate with application of aspheric RGP compared to spherical RGP. Hence, aspheric RGP is suggested for CLM when determining corneal power in normal eyes. 

 

Keywords: Aspheric RGP; contact lens design; contact lens method; corneal power; rigid gas permeable

 

ABSTRAK

Kaedah kantah sentuh (CLM) merupakan satu pilihan alternatif untuk menentukan kuasa kornea dengan menilai perbezaan atas-pembiasan dengan kanta sentuh separa keras (RGP) kepada refraksi nyata. Tujuan kajian ini adalah untuk menilai ketepatan CLM menggunakan kanta sentuh sfera (CLMspherical) dan asferik (CLMaspheric) dalam pengukuran kuasa refraksi kornea normal. Kajian prospektif ini merekrut 45 mata normal daripada 45 subjek sihat. Pengukuran kuasa kornea ditentukan oleh CLMspherical menggunakan RGP Boston ES dan CLMaspheric menggunakan RGP Boston Envision berdasarkan strategi pemasangan optimum. Refraksi nyata dan atas-pembiasan ditentukan menggunakan keadah refraksi objektif dan subjektif yang piawai. IOLMaster ditetapkan sebagai kaedah rujukan untuk perbandingan. Min perbezaan aritmetik, min perbezaan mutlak dan 95% had-had persetujuan (LOA) kuasa kornea yang diperoleh daripada CLMspherical dan CLMaspheric kepada nilai IOLMaster dinilai untuk perbandingan ketepatan. Min perbezaan aritmetik dan min perbezaan mutlak kuasa kornea yang diperoleh CLMspherical dan CLMaspheric kepada nilai IOLMaster adalah masing-masing 0.10 ± 0.21 D dan 0.20 ± 0.11 D dan 0.04 ± 0.09 D dan 0.08 ± 0.05 D. Julat 95% LOA antara CLMspherical dan IOLMaster adalah -0.30 ke 0.51 D, manakala antara CLMaspheric dan IOLMaster adalah -0.14 ke 0.21 D. CLM dalam menganggar kuasa kornea adalah lebih tepat dengan menggunakan RGP asferik berbanding RGP sfera. Oleh demikian, penggunaan RGP asferik dicadangkan untuk CLM bagi menentukan kuasa kornea pada mata normal. 

 

Kata kunci: Kaedah kanta sentuh; kanta sentuh separa keras; kuasa kornea; reka bentuk kanta sentuh; RGP asferik

 

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*Pengarang untuk surat-menyurat; email: syah@iium.edu.my

     

 

 

 

 

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