Central corneal thickness plays a major role in the management of many types of glaucoma. Therefore, our aim is to determine the relationship between the severity of glaucoma measured by optical coherence tomography (OCT) and central corneal thickness (CCT) among normal tension and high tension glaucoma patients. This is an observational cross sectional study on 190 patients carried out in Universiti Kebangsaan Malaysia Medical Centre (UKMMC). Three groups of patients were identified; 60 normal tension glaucoma (NTG), 61 primary open angle glaucoma (POAG) and 69 control. Patients were identified based on the glaucomatous visual field changes and previous record of intraocular pressure before treatment. Visual acuity and intraocular pressure measurements were recorded. Specular microscope was used to measure the CCT and the severity of glaucoma was evaluated objectively based on the retinal nerve fibre layer (RNFL) thickness using optical coherence tomography. Results showed NTG patients had significantly thinner cornea, 503.07±32.27µm compared to the control group, 517.45±31.74 µm (p=0.012). However, there was no significant difference between the CCT of POAG and NTG groups (p=0.386).Retinal nerve fibre layer (RNFL) thickness was significantly different between the glaucoma and the control groups (p<0.05 in all quadrant). However, correlation between CCT and severity of RNFL thinning was only found for the POAG group but not for the NTG group. (mean RNFL and superior quadrant RNFL; r=0.251,0.401) . This study demonstrated the correlation between CCT and severity of glaucoma in POAG patients but not for the NTG group. Therefore, CCT is related to the severity of POAG-related visual loss.
Relationship between Central Corneal Thickness and Severity of Open Angle Glaucoma using Optical Coherence Tomography
Abstrak
Ketebalan kornea memainkan peranan penting dalam merawat pesakit glaukoma. Tujuan kajian in adalah untuk mengenalpasti hubungan di antara ketebalan tengah kornea dengan ukuran ketebalan lapisan saraf retina bagi pesakit glaukoma sudut terbuka (glaukoma bertekanan rendah dan glaukoma bertekanan tinggi). Ini adalah kajian pemerhatian dibuat ke atas pesakit di Pusat Perubatan Universiti Kebangsaan Malaysia dan melibatkan seramai 190 mata (190 pesakit). Pesakit adalah terdiri daripada 60 orang pesakit glaukoma bertekanan rendah, 61 pesakit glaukoma bertekanan tinggi dan seramai 69 pesakit normal yang digunakan sebagai kontrol. Pesakit-pesakit ini dikenalpasti berdasarkan kerosakan luas pandangan yang bercirikan glaukoma dan melalui catatan rekod tekanan mata sebelum rawatan dimulakan. Ketajaman penglihatan diuji. Ketebalan pusat kornea diukur menggunakan mikroskop spekular.Ukuran ketebalan lapisan saraf retina dibuat menggunakan ‘optical coherence tomography. ’Keputusan kajian menunjukkan pesakit glaukoma bertekanan rendah didapati memiliki perbezaan ketebalan pusat kornea (503.07um±32.27) yang ketara, berbanding dengan kumpulan control, 517.45±31.74 (p=0.012). Manakala perbezaan ketebalan kornea adalah tidak ketara bagi pesakit glaucoma bertekanan rendah dibandingkan dengan pesakit glaukoma bertekanan tinggi.(p=0.386). Ukuran ketebalan lapisan saraf retina dan pengukuran urat mata menunjukkan perbezaan yang ketara diantara pesakit glaukoma susut terbuka dan kumpulan kontrol. Terdapat korelasi yang ketara di antara ketebalan purata lapisan saraf retina dan ketebalan saraf di bahagian atas dengan ketebalan pusat kornea bagi pesakit glaukoma bertekanan tinggi (r=0.251,0.401) tetapi tidak bagi pesakit glaukoma bertekanan rendah. Kesimpulan kajian ini menunjukkan korelasi ketara bagi ketebalan pusat kornea dengan purata ketebalan lapisan saraf retina dan ketebalan saraf di bahagian atas (‘superior quadrant’) bagi pesakit glaukoma bertekanan tinggi. Korelasi yang serupa tidak ditemui bagi pesakit glaukoma bertekanan rendah.
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Related Images
a.jpg "Figure 1. Correlation between the superior quadrant retinal nerve fibre layer (RNFL) and Central corneal thickness in Primary Open Angle Glaucoma")
b.jpg "Figure 2. Correlation between the average(mean) retinal nerve fiber layer (RNFL) and Central corneal thickness in Primary Open Angle Glaucoma")
table1.jpg "Table 1. Intraocular Pressure and Central Corneal Thickness for the normal tension glaucoma, primary open angle glaucoma and control group.")
table2.jpg "Table 2: Mean retinal nerve fiber layer thickness measurement in all quadrant")
table3.jpg "Table 3: Correlation between central corneal thickness and retinal nerve fibre layer")
