Assessment of Macular Retinal Thickness and Volume in Normal

1,2 1 1 1 Assessment of P-C Wu , Y-J Chen , C-H Chen , Y-H Chen , STUDY CLINICAL S-J Shin2, H-J Yang3 and H-K Kuo1 macular retinal thickness and volume in normal eyes and highly myopic eyes with third-generation optical coherence tomography 1Department of Ophthalmology, Chang Gung Memorial Hospital- Kaohsiung Medical Center; Abstract thinner in the inner and the outer macular Chang Gung University College of Medicine, region. The retina of individuals with high Purpose To compare the macular retinal Kaohsiung, Taiwan myopia had smaller macular volume than thickness and macular volume between those with non-myopia. 2 subjects with high myopia and non-myopia. Graduate Institute of Eye (2008) 22, 551–555; doi:10.1038/sj.eye.6702789; Medicine, Kaohsiung Methods This prospective nonrandomized, published online 27 April 2007 Medical University, comparative study recruited healthy subjects Kaohsiung, Taiwan with high myopia subjects, defined as a Keywords: myopia; fovea; macula; retinal spherical equivalence (SE) over À6 dioptres 3Tzu-Hui Junior College of thickness; optic coherence tomography (D) or AXLX26.5 mm and the best corrected Health Care and visual acuity better than 20/25, and subjects Management, Ping Tung, Taiwan with non-myopia, defined as an with SE between 1.5D and À1.5 D and the BCVA better Introduction Correspondence: H-K Kuo, than 20/25. Optical coherence tomography was Department of performed in each eye. Optical coherence tomography (OCT) is an Ophthalmology, Results Eighty high myopic eyes and 40 objective method that provides useful Chang Gung Memorial non-myopic eyes were included. The mean age information regarding macular characteristics Hospital-Kaohsiung Medical 1–4 Center, 123, Ta-Pei Road, of the high myopic group and non-myopia and relative morphological changes. Niao-Sung Hsiang, group was 29.6 and 27.5 years old, respectively. Third-generation OCT (OCT-3) is a recent Kaohsiung Hsien, 883, The mean refraction was –9.27 D in the high modification of this method, which provides a Taiwan myopia group and –0.22 D in the non-myopia better resolution than first-generation OCT. Tel: 886 7 7317123 ext. group. The high myopia group had Myopia is a highly prevalent condition with 2801; Fax: 886 7 7318762. significantly greater mean retinal thickness in reported rates as high 80% in South-East Asia E-mail: d2767@ 5–7 the foveola and fovea 1 mm area than the and 25% in the West. High myopia is typically adm.cgmh.org.tw non-myopia group (166 vs 149 lm, Po0.0001, defined as in excess of 6 dioptres (D). High 199 vs 188 lm, P ¼ 0.0063, respectively). myopia is invariably attributable to increased Received: 7 November 2006 However, the mean retinal thickness in the eye size. Excessively large eyes are also at great Accepted in revised form: inner and outer macular area (superior, nasal, risk of developing sight-threatening pathology 16 February 2007 8,9 Published online: inferior, or temporal) of the high myopia group of the retina and choroids. Recent studies 27 April 2007 was significantly less than in the non-myopia using OCT demonstrated asymptomatic group. In addition, the high myopia group had macular holes and myopic traction Authors have no financial significantly smaller macular volume than the maculopathy in highly myopic eyes.10,11 The interests in the study non-myopia group (Po0.0001). purpose of this study was to use OCT to This work has previously Conclusion This study demonstrated that the evaluate the variations in macular retinal been presented at the 21st retinal thickness in individuals with high thickness in normal eyes and otherwise healthy Congress of the Asia-Pacific myopia is thicker in the foveola and fovea, but highly myopic eyes. Academy of Ophthalmology Macular retinal thickness and volume in highly myopic eyes with OCT-3 P-C Wu et al 552

Materials and methods S

Subjects for this study were recruited from among young 249 adults aged from 18 to 40 who visited the ophthalmology clinic of Chang Gung Memorial Hospital, Kaohsiung 262 Medical Center between December 2004 and December T 221 255 165 260 258 N 2005. Subjects with the diagnosis of high myopia as well 1.0 mm as healthy controls meeting eligibility requirements were 267 3.00 mm eligible for participation. This study was approved by the 6.00 mm 225 hospital’s institutional review board and was carried out Microns Map Diameters in accordance with the World Medical Association’s I Declaration of Helsinki. Informed consents were Foveal thickness 143+/-5 microns obtained for each subject before enrolment. Patients OD Total macular volume 6.84 mm3 enrolled in this study underwent a complete ophthalmologic examination, which included the Scans used 1, 2, 3, 4, 5, 6 following: best-corrected visual acuity testing; Figure 1 Schematic diagrams of ocular coherence tomography intraocular pressure measurement; slit-lamp scans of the right eye showing foveal thickness in a 1 mm examination; dilated slit-lamp examination with stereo concentric diameter and inner and outer macular thickness in biomicroscopy; and indirect ophthalmoscopy. A-scan test the superior, temporal, and inferior positions. S: superior. were obtained. OCT-3 was performed on one or both N: nasal. I: inferior. T: temporal. The inferior column shows eyes of each subject after pupil dilation. the foveolar thickness and total macular volume. Foveolar thickness was calculated from the central point of foveal A normal eye was defined as having spherical thickness. Total macular volume is also shown in the column. equivalence refraction (SE) between þ 1.5 and À1.5 D. Otherwise healthy highly myopic eyes were defined as entire scan area were recorded. Ophthalmic having an SE less than À6D. In addition, the best photographers who were trained in the use of the OCT-3 corrected visual acuity in each eye of both groups was system performed all OCT scans through a dilated pupil. better than 16/20. Exclusion criteria were as follows: Statistical analysis was performed using the Statistical visual acuity worse than 16/20; previous intraocular Package for Social Sciences (version 11.0, SPSS Inc., surgery; coexisting retinal diseases and uveitis; corneal Chicago, IL, USA). Because of the non-normal abnormalities; media opacities; and glaucoma. distribution of these data, Mann–Whitney U test was The OCT-3 system used in this study (model 3000, used to generate P-values between the two groups. The software version B 3.0) (Carl Zeiss Meditec, Dublin, CA, association with categorical variables was assessed using USA) permits cross sectional imaging by acquiring a a w2 test. Po0.05 was defined as statistically significant. sequence of 128 interferometric axial reflectance profiles (A-scans) of the retina. The OCT-3 fast scan protocol Results completed total data acquisition in 1.92 s. To obtain a map of retinal thickness at the macula, six equally spaced One hundred twenty eyes of 73 patients were included in intersecting radial scans through the centre of the fovea this cross-sectional study. Eighty of the eyes of these were performed. Each radial scan had a diameter of patients met criteria for high myopia and 40 eyes met the 6.0 mm and comprised a circular area centred on the criteria for normal (Table 1). The mean age7SD was fovea. Again, the OCT-3 fast scan protocol was used, 29.5876.26 years (range, 18–40 years) in the non-myopia with each radial line consisting of 128 A-scans (768 total group and 27.5076.72 years (range, 18–40 years) in the A-scans). Foveola thickness and fovea thickness within high myopia group. There was no significant difference 1 mm concentric diameter were determined using the in the mean age of patients in the two groups (P ¼ 0.102). commercial OCT-3 B 3.0 software. Foveola thicknes