Yasser M. Tariq

Impact of Ethnicity on the Correlation of Retinal Parameters with Axial Length

PURPOSE To examine whether the relationship of axial length (AL) to retinal nerve fiber layer (RNFL) and macular parameters measured by optical coherence tomography (OCT) differs according to ethnicity. METHODS As part of the Sydney Myopia Study, 2353 children from grade 7 (age range, 11.1-14.4 years) completed detailed ocular examinations in the 2004-2005 school year. AL was measured with noncontact interferometry and Stratus OCT was performed (Carl Zeiss Meditec, Jena, Germany). RESULTS East Asian children displayed larger AL correlations with average RNFL, inferior RNFL, nasal RNFL, outer macula, and macular volume (r = -0.25, -0.36, -0.31, -0.35, and -0.31 respectively; P < 0.001) than did Caucasian children (r = -0.14, -0.20, -0.12, -0.17, and -0.13 respectively; P < 0.001). Positive correlations between the temporal RNFL and AL were found only among East Asian and South Asian children (r = 0.28, P < 0.001; and r = 0.27, P = 0.03, respectively). In Caucasian children, the foveal minimum and central macula correlated significantly with AL (r = 0.11 and r = 0.13, respectively, P ≤ 0.001). CONCLUSIONS Retinal parameters measured by OCT correlated with AL, and the extent of this correlation varied by ethnicity. It may therefore be that ethnicity should be considered when interpreting OCT scans on individuals with AL outside the usual range.

Symmetry of retinal parameters measured by spectral-domain OCT in normal young adults.

Purpose:To determine interocular differences in retinal parameters in a population of young adults using spectral-domain optical coherence tomography. Methods:In the Sydney Adolescent Vascular Eye Study, young adults aged 16 to 19 years received a standardized eye examination encompassing retinal photography, spectral-domain optical coherence tomography (Cirrus HD-OCT; Carl Zeiss Meditec, Dublin, CA) and best-corrected visual acuity. Interocular differences in retinal nerve fiber layer (RNFL) and macular parameters together with sex and ethnic variations for these differences were determined. Results:In the 1500 subjects tested, right eyes had thicker average RNFL than left eyes (0.3 &mgr;m, P=0.0074). There were no significant interocular differences in central macular or macular cube average thickness. After adjusting for interocular difference in axial length, right eyes had slightly smaller total macular volume than left eyes (−0.0082 mm3, P=0.008). The 2.5% to 97.5% limits of asymmetry were 9.3 &mgr;m for average RNFL, 8 &mgr;m for average macular thickness, and 0.20 mm3 for total macular volume. In the outer inferior quadrant, there was a greater macular thickness asymmetry in females than males (−0.7 &mgr;m, P=0.037). In the inferior RNFL quadrant (−2.6 &mgr;m, P=0.0013) and in the outer inferior macular quadrant (1.6 &mgr;m, P=0.0018), white individuals had greater symmetry than East Asians. Conclusions:In this study, we report the degree of interocular symmetry of RNFL and macular parameters measured by Cirrus HD-OCT in healthy young adults.

Retinal nerve fiber layer and optic disc measurements by spectral domain OCT: normative values and associations in young adults

PurposeTo determine normative values and associations of retinal nerve fiber layer (RNFL) and optic disc parameters in normal eyes measured by spectral domain optical coherence tomography (OCT).MethodsIn a population-based setting, 1521 young adults were examined as part of the Sydney Adolescent Vascular and Eye Study (SAVES). Their mean age was 17.3±0.6 years. RNFL and optic disc parameter measurements were made using Cirrus HD-OCT 4000.ResultsThe average RNFL was found to be 99.4±9.6 μm. RNFL thickness was least for the temporal quadrant (69.9±11.2 μm), followed by the nasal (74.3±12.8 μm), superior (124.7±15.7 μm) and inferior (128.8±17.1 μm) quadrants. The mean disc area in this population was 1.98±0.38 mm2 with a mean rim area of 1.50±0.30 mm2 and a mean cup/disc ratio of 0.44±0.18. Multivariate-adjusted RNFL thickness was marginally greater in East Asian than in white participants (100.1 μm vs 99.5 μm; P=0.0005). The RNFL was thinner with greater axial length (P<0.0001), less positive spherical equivalent refractions (P<0.0001), smaller disc area and rim area (P<0.0001).ConclusionThis study documents normative values for the RNFL and optic disc measured using Cirrus HD-OCT in young adults. The values and associations reported in this study can inform clinicians on the normal variation in RNFL and optic disc parameters.

Symmetry of Optic Nerve Head Parameters Measured by the Heidelberg Retina Tomograph 3 in Healthy Eyes: The Blue Mountains Eye Study

PURPOSE To assess the symmetry of optic nerve head parameters measured by the Heidelberg Retina Tomograph 3 (HRT 3) between fellow eyes in a normal elderly population. DESIGN Cross-sectional population-based study. METHODS Participants of the Blue Mountains Eye Study 10-year follow-up who did not have optic disc disease, including glaucoma, were included. Optic nerve head parameters measured by HRT 3 were compared between fellow eyes. The normal range of interocular asymmetry (larger disc minus smaller disc) was determined by the 2.5th and 97.5th percentiles. RESULTS A total of 1276 eligible participants had HRT scans of both eyes. HRT measurements in right eyes differed slightly in rim steepness and rim volume from those in left eyes (P < .05). The 2.5th and 97.5th percentile of interocular asymmetry limits were -0.41 and 0.45 for cup-to-disc ratio and -0.19 and 0.22 for cup-to-disc area ratio, respectively. The highest interocular correlation was found in disc area and cup area (r ranged from 0.74-0.76), whereas mean cup depth, cup volume, and retinal nerve fiber layer thickness had the poorest correlation (r ≤ 0.07). Greater optic disc area asymmetry was associated with a larger interocular difference in the other optic nerve head parameters. CONCLUSIONS There was minimal interocular difference and substantial interocular correlation in optic nerve head parameters measured by HRT 3. Interocular asymmetry greater than 0.2 for cup-to-disc area ratio was considered outside the normal range.

Characteristics and appearance of the normal optic nerve head in 6-year-old children

Aim To document planimetric measures of normal optic nerve head parameters in 6-year-old children and to report prevalence and associations of common optic nerve signs. Methods The Sydney Childhood Eye Study examined 1765 children aged 6 years. Complete retinal photographs were available for 1225 participants, captured using a digital camera. Optical coherence tomography optic-disc measurements were acquired using the ‘fast’ optic-disc protocol. Statistical analyses were conducted using SAS version 9.1.3. Results The mean (95% CIs) planimetric optic-disc area was 2.29 mm2 (2.27 to 2.32), mean cup area 0.48 mm2 (0.47 to 0.50), mean vertical disc diameter 1.81 mm (1.80 to 1.82) and mean vertical cup diameter 0.72 mm (0.71 to 0.73), resulting in a mean vertical cup/disc ratio of 0.40 (0.39 to 0.40). Similarities existed between vertical, horizontal and area cup/disc ratios (p>0.05) measured by planimetry and optical coherence tomography, but only for vertical disc diameters between 1.75 and 1.96 mm. Visible lamina cribrosa pores were present in 4.9%. This sign was associated with larger optic nerve parameters. The prevalence of optic disc tilt and cyclotorsion was 1.6% and 8.7%, respectively, and the prevalence of α- and β-peripapillary atrophy was 43.3% and 20.2%, respectively. Neither sign was associated with myopia, after adjusting for age, sex and ethnicity, although eyes with β-peripapillary atrophy had a longer mean axial length (p=0.04). Cilioretinal arteries were present in 27% and tended to be located temporally. Conclusions The mean vertical cup/disc ratio was 0.4 in this 6-year-old sample. Planimetric optic nerve head measures and population prevalence findings for optic disc signs in this population could be regarded as normative data for ophthalmologists in clinical settings.

Ethnic differences in macular thickness.

Background:  To determine ethnic differences in time‐domain (Stratus) optical coherence tomography‐measured macular thickness in 12‐year‐old children.

Retinal Thickness in the Offspring of Diabetic Pregnancies

PURPOSE To compare macular and peripapillary retinal nerve fiber layer (RNFL) thickness in children from diabetic compared with nondiabetic pregnancy. DESIGN Cross-sectional study. METHODS As part of the Sydney Myopia Study, 2367 children from grade 7 (age range 11.1 to 14.4 years) completed detailed ocular examinations during 2004-2005. Examination included determination of best-corrected visual acuity (logarithm of minimal angle of resolution) and autorefraction after cycloplegia. Axial length was measured using noncontact interferometry. Optical coherence tomography (OCT) was performed using Stratus OCT through dilated pupils. Participants and parents completed comprehensive questionnaires including questions on birth parameters and medical history. RESULTS There were 1741 and 1687 children with adequate-quality RNFL and macular scans respectively, who had complete examination and questionnaire data. There were 57 children from diabetic pregnancies who had both RNFL and macular scans. Children from diabetic pregnancies had significantly thinner inner (264.9 μm vs 270.2 μm, P = .007) and outer (231.9 μm vs 238.6 μm, P = .0001) macular thickness and macular volume (6.75 mm(3) vs 6.92 mm(3), P = .0003) compared with children from nondiabetic pregnancies. However, central macular thickness, foveal minimum thickness, and RNFL parameters were not significantly different between the 2 groups. CONCLUSION Diabetes during pregnancy is associated with changes in retinal morphology in the offspring. Thinning of the pericentral macular parameters was evident in Stratus OCT scans of children from diabetic pregnancies. These findings suggest the possibility that maternal diabetes impacts on the development of the retina.

Stratus OCT signal strength and reliability of retinal nerve fiber layer measurements.

5 Although the 2 studies have different outcome measures as escribed above, the conclusions that may be drawn from heir findings share a common point, which is the potential of reater susceptibility of the optic nerve to high IOP in ubjects with PEX. However, we need to note that in the tudy by Teus and associates only subjects with IOP 21 mm g were included. Our study included unbiased randomly elected cases from the general population, providing the hole spectrum of IOP. In addition, the cutoff value of 20 m Hg was determined based on a statistical analysis estiating the threshold IOP level above which the proportion ith glaucoma increased statistically significantly among both EX and non-PEX subjects. As reported in our manuscript, he results were different for IOP 20 mm Hg compared to OP 20 mm Hg. Interestingly, for IOP 20 mm Hg, the roportion with glaucoma did not differ between PEX and on-PEX subjects.

Low Vision Among Preschool Children in the Beijing Study of Visual Impairment

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