Sains Malaysiana 43(5)(2014): 733–737

Changes in Refraction and Contrast Sensitivity Following Short Term Orthokeratology Treatment in High Myopic School Children: A Pilot Study

(Perubahan Refraksi dan Sensitiviti Kontras selepas Rawatan Ortokeratologi Jangka Pendek

dalam Kalangan Kanak-kanak Sekolah Miop Tinggi: Suatu Kajian Awal)

BARIAH MOHD-ALI*¹, TAN BAY WAH² & NORHANI MOHIDIN¹

¹Optometry and Vision Science Program, School of Health Care Sciences,

Faculty of Health Sciences, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz

50300 Kuala Lumpur, Malaysia

²Loyal Eye Clinic, 26, Jalan SJ17, Taman Selayang Jaya

68100 Batu Caves, Selangor, D.E. Malaysia

Diserahkan: 27 Januari 2012/Diterima: 23 Ogos 2013

ABSTRACT

It is well established the efficacy of orthokeratology (OK) treatment in improving refraction and visual acuity (VA) of low myopic subjects. However, limited data is available on high myopes. The purpose of this study was to investigate the changes of refraction, VA and contrast sensitivity (CS) over time in high myopic school children after 1 week of overnight OK treatment. A total of 19 high myopic school children were fitted with OK lenses. Mean refraction at baseline was -6.29±1.25 DS. Refraction was conducted using cross cylinder method and LogMAR chart. CS was evaluated using Pelli-Robson and FACT charts. All measurements were taken at baseline, 1, 2, 3 and 7 days after overnight OK. Data was analyzed using repeated measures of ANOVA. The results showed that refraction and CS were significantly improved throughout the study period (p<0.05). Significant changes in all parameters were noted after the first overnight treatment. Mean refraction and unaided VA after 7 nights of treatment was -0.64±1.17DS and 0.08±0.29, respectively. The results from Pelli-Robson and FACT charts showed improvement comparable to aided baseline values (p>0.05). This study concludes that overnight OK reduces refraction but does not compromise VA and CS in high myopic children within the study period. Further studies are needed to determine the long term impact of OK treatment on visual functions in a larger sample of high myopic children.

Keywords: Contrast sensitivity; orthokeratology; refraction; visual acuity

ABSTRAK

Keberkesanan rawatan ortokeratologi (OK) dalam menurunkan nilai refraksi dan meningkatkan akuiti visual (VA) dalam kalangan subjek miop telah diketahui umum. Walau bagaimanapun data tentang keberkesanan teknik ini dalam kalangan subjek miop tinggi agak terhad. Penyelidikan ini bertujuan untuk mengkaji perubahan nilai refraksi, VA dan sensitiviti kontras dalam kalangan kanak-kanak sekolah miop tinggi selepas 1 minggu rawatan OK. Seramai 19 orang kanak-kanak sekolah miop tinggi telah dipasangkan dengan kanta OK. Purata nilai refraksi sebelum rawatan adalah -6.29±1.25DS. Nilai refraksi diukur menggunakan teknik silinder silang dan carta LogMAR. Sensitiviti kontras (CS) diukur menggunakan carta Pelli-Robson dan FACT. Semua bacaan diambil sewaktu sebelum pemakaian kanta, 1, 2, 3 dan 7 hari selepas rawatan OK. Analisis data dilakukan menggunakan ANOVA. Keputusan kajian menunjukkan penurunan nilai refraksi dan peningkatan nilai CS yang signifikan di sepanjang waktu kajian (p<0.05). Perubahan signifikan pada semua parameter yang diukur dikesan selepas malam pertama rawatan. Purata refraksi dan VA tanpa pembetulan selepas 7 malam adalah -0.64±1.17DS dan 0.08±0.29. Keputusan daripada carta Pelli-Robson dan FACT menunjukkan peningkatan setanding dengan nilai sewaktu pemakaian kaca mata (p>0.05). Kajian ini menyimpulkan bahawa rawatan jangka pendek OK menurunkan nilai refraksi tanpa menjejaskan nilai VA dan CS dalam kalangan subjek miop tinggi. Kajian jangka masa panjang diperlukan untuk memastikan kesan pemakaian kanta OK ke atas fungsi penglihatan kanak-kanak miop tinggi dengan saiz sampel yang lebih besar.

Kata kunci: Akuiti visual; ortokeratologi; refraksi; sensitiviti kontras

RUJUKAN

Berntsen, D.A., Barr, J.T. & Mitchell, G.L. 2005. The effect of overnight contact lens corneal reshaping on higher-order aberrations and best-corrected visual acuity. Optom. Vis. Sci. 82: 490-497.

Chung, K.M., Mohidin, N., Yeow, P.T., Tan, L.L. & O’Leary, D.J. 1996. Prevalence in visual disorders of Chinese school children. Optom. Vis. Sci. 73(11): 695-700.

Goh, P.P., Abqariyah, Y., Pokharel, G.P. & Ellwein, L.B. 2005. Refractive error and visual impairment of school age children in Gombak district Malaysia. Ophthalmology 112(4): 678- 685.

Hiraoka, T., Okamoto, C. & Ishii, Y. 2007. Contrast sensitivity function and ocular higher-order aberrations following overnight orthokeratology. Invest. Ophthalmol. Vis. Sci. 48: 550-556.

Hiraoka, T., Furuya, A., Matsumoto, Y., Okamoto, F., Sakata, N., Hiratsuka, K., Kakita, T. & Oshika, T. 2004. Quantitative evaluation of regular and irregular corneal astigmatism in patients having overnight orthokeratology. J. Cataract Refract. Surg. 30: 1425-1429.

Johnson, K.L., Carney, L.G., Mountford, J.A., Collins, M.J., Cluff, S. & Collins, P.K. 2007. Visual performance after overnight orthokeratology. Contact Lens & Anterior Eye 30: 29-36.

Lum, E. & Swarbrick, H.A. 2011. Lens Dk/t influences the clinical response in overnight orthokeratology. Optom. Vis. Sci. 88(4): 469-475.

Nichols, J.J., Marsich, M.M., Nguyen, M., Barr, J.T. & Bullimore, M.A. 2000. Overnight orthokeratology. Optom. Vis. Sci. 77: 252-259.

Soni, P.S., Nguyen, T.T. & Bonanno, J.A. 2003. Overnight orthokeratology: Visual and corneal changes. Eye & Contact Lens 29: 137-145.

Sorbara, L., Fonn, D., Simpson, T., Lu, F. & Kort, R. 2005. Reduction of myopia from corneal refractive therapy. Optom. Vis. Sci. 82: 512-518.

Stevens, J., Giubilei, M., Ficker, L. & Rosen, P. 2002. Prospective study of photorefractive keratectomy for myopia using the VISX StarS2 Excimer laser system. J. Refract. Surg. 18: 502-508.

Stillitano, I., Schor, P., Lipener, C. & Hofling-Lima, A. 2008. Long term follow up of orthokeratology reshaping using wavefront abberometry and contrast sensitivity. Eye & Contact Lens 34(3): 140-145.

Swarbrick, H.A.2006. Orthokeratology review and update. Clin. Exp. Optom. 89: 124-143.

Tahhan, N., Du Toit, R., Papas, E., Chung, H., La Hood, D. & Holden, A.B. 2003. Comparison of reverse-geometry lens designs for overnight orthokeratology. Optom. Vis. Sci. 80: 796-804.

*Pengarang untuk surat-menyurat; email: bariah@medic.ukm.my