Sains Malaysiana 46(10)(2017): 1913–1921

http://dx.doi.org/10.17576/jsm-2017-4610-30

 

Perbandingan Zon Interaksi Ruang Dua Dimensi Subjek Normal dan Ambliopia Anisometropik

(Comparison of Two Dimension Spatial Interaction Zones between Normal Vision and Anisometropic Amblyopia)

 

MOHD IZZUDDIN HAIROL*, NORAZIZAH ABD LATIF, WOI PUI JUAN, NURUL HAFIZAH AHMAD RASHAIDI & SHARANJEET-KAUR

 

Program Optometri & Sains Penglihatan, Fakulti Sains Kesihatan, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur

 

Diserahkan: 29 Mei 2017/Diterima: 11 Ogos 2017

 

ABSTRAK

Akuiti visual subjek ambliopia anisometropik sering disimulasi pada individu normal dengan mengkaburkan penglihatan fovea mereka. Walau bagaimanapun, prestasi akuiti visual periferi subjek ini tidak diketahui dan kaedah pengkaburan ini tidak semestinya dapat mensimulasi penglihatan periferi mereka. Untuk mendalami ketepatan kaedah ini, kami mengkaji akuiti dan bentuk zon interaksi ruang di fovea dan periferi retina subjek normal dan ambliopia anisometropik serta kesan pengkaburan pada akuiti subjek normal pada esentrisiti retina yang berbeza untuk dibandingkan dengan periferi subjek ambliopia. Akuiti diukur menggunakan Kaedah Rangsangan Malar untuk huruf Sheridan-Gardiner pada 6 orang subjek normal dan 6 orang subjek ambliopia anisometropik. Kesan kesesakan diukur dengan membandingkan respons pengesanan huruf sasaran yang diapit oleh huruf lain yang diletakkan pada orientasi mendatar, menegak dan pepenjuru. Rangsangan dipaparkan pada fovea dan 2.5, 5 dan 10 darjah di medan penglihatan inferior. Selain itu, akuiti fovea 4 orang subjek normal dikaburkan supaya sepadan dengan akuiti fovea subjek ambliopia menggunakan kaedah pengkaburan optik dan penuras digital Gaussian. Subjek normal menunjukkan kemerosotan akuiti yang lebih besar dengan peningkatan esentrisiti retina (E2: 2.25±0.21) berbanding subjek ambliopia anisometropik (E2: 6.02±1.45). Kesemua subjek menunjukkan zon interaksi ruang yang tidak simetri di kesemua esentrisiti retina yang diuji. Interaksi antara jenis kabur dan esentrisiti retina adalah signifikan F(2.13,6.38)=4.93, p=0.049) tetapi akuitisubjek normal yang dikaburkan dengan kedua-dua kaedah pengkaburan tidak berbeza secara signifikan dengan akuiti subjek ambliopia. Zon interaksi ruang subjek ambliopia anisometropik adalah sama dengan subjek normal. Akuiti fovea subjek ambliopia anisometropik lebih teruk berbanding subjek normal kerana peningkatan pengkaburan intrinsik. Walau bagaimanapun, periferi subjek ambliopia adalah normal secara fungsian.

 

Kata kunci: Ambliopia anisometropik; kesan kesesakan; pengkaburan; penglihatan fovea; penglihatan periferi

 

ABSTRACT

 

Visual acuity of anisometropic amblyopes is often simulated in visually normal individuals by imposing blur on their foveal vision. However, their peripheral visual acuity and whether the same method can simulate their peripheral vision are unknown. We examined acuity and shape of spatial interaction zones at the fovea and in the periphery, in normal participants and anisometropic amblyopes; and the effect of imposed blur on acuity at different eccentricities in normal participants to compare with the amblyopic periphery. Acuity was measured with Method of Constant Stimuli using Sheridan-Gardiner letters in 6 normal and 6 amblyopic participants. Crowding was assessed by comparing performance for a letter flanked by other letters placed at horizontal, vertical and oblique orientations. Stimuli were presented foveally and at 2.5, 5 and 10 degrees in the lower visual field. In addition, foveal acuity of 4 normal participants was blurred to match the mean amblyopic acuity using Gaussian and optical defocus. Acuity was then re-measured across the lower visual field. Normal participants showed larger acuity deterioration with increasing eccentricity (E2 of 2.25±0.21) than did anisometropic amblyopes (E2 of 6.02±1.45). Both groups exhibited asymmetric crowding regions at all locations. Acuity was worse with optical blur compared to with Gaussian blur (significant blur type and eccentricity interaction, F(2.13,6.38)=4.93, p=0.049) but neither was significantly different from the acuity of amblyopes. Anisometropic amblyopia demonstrated similar asymmetric crowding regions to those found in normal vision, i.e. generally larger crowding for arrangements radial to the fixation point. Foveal acuity in anisometropic amblyopia was worse due to increased intrinsic blur relative to normal vision; however, their periphery appeared to be functionally normal.

 

Keywords: Anisometropic amblyopia; blur; crowding effect; foveal vision; peripheral vision

 

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*Pengarang untuk surat-menyurat; email: izzuddin.hairol@ukm.edu.my