Normative Data of Optic Nerve Head in Thai Population by Laser Scanning Tomography: Siriraj Study
Ngamkae Ruangvaravate MD*, Chareenun Neungton MD*
Affiliation : * Department of Ophthalmology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok
Objective : To study the normative values of topographic optic disc parameters in a Thai population.
Material and Method: Two hundred and six eyes of 103 normal subjects aging from 30-80 years were studied.
Thirteen topographic disc parameters were analyzed by confocal scanning laser ophthalmoscope using
Heidelburg retina tomography (HRT II). The average value of two eyes in the same subject was used as the unit
of statistical analysis, and then the normal values and means were statistically calculated at 95% reference
interval (95% RI). Ethnic differences of the calculated optic nerve topography were compared with previous
studies. The relationship of age, intraocular pressure (IOP), central corneal thickness (CCT), and optic disc
parameters were assessed by Pearson correlation.
Results : Mean values with 95% RI of all 13 parameters were analyzed. Whole parameters except cup volume
demonstrated normal distribution. Mean value (95% RI) of disc area in normal Thai people was 2.67 mm2
(1.96, 3.71) which was larger than Caucasian people. Ethnic differences in topographic optic disc parameters
were found among Thai and other races including Asians, Caucasians, African-Americans, and Hispanics.
The results also revealed that age, IOP, and CCT had no significant relation to all optic disc parameters.
Conclusion : Thai people had a larger optic disc area than Caucasians. There are marked differences of
topographic optic nerve parameters among different ethnic groups. These differences need to be taken into
account when evaluating glaucomatous optic neuropathy and when comparing results of studies completed
among population of different ethnic and racial origins.
Keywords : Laser scanning tomography, HRT, Optic nerve head, Disc area, Disc size
