Optic nerve head parameters of an indigenous population living within Central Australia

Optical Coherence Tomography-Derived Measurements of the Optic Nerve Head Structure of Aboriginal and Torres Strait Islander Children

PRCIS

This study demonstrated significant differences in optic nerve head characteristics in Aboriginal and Torres Strait Islander children compared with non-Indigenous children, which has implications for glaucoma risk and diagnosis in Aboriginal and Torres Strait Islander populations.

PURPOSE

The purpose of this study was to examine the optic nerve head (ONH) characteristics of visually normal Aboriginal and Torres Strait Islander children and non-Indigenous Australian children.

MATERIALS AND METHODS

Spectral domain optical coherence tomography imaging was performed on the right eye of 95 Aboriginal and Torres Strait Islander children and 149 non-Indigenous Australian children (5-18 years). Horizontal and vertical line scans, centered on the ONH, were analyzed to determine the dimensions of the ONH (Bruch membrane opening diameter), optic cup diameter, Bruch membrane opening minimum rim width, and the peripapillary retinal nerve fiber layer thickness.

RESULTS

The vertical but not horizontal Bruch membrane opening diameter of Aboriginal and Torres Strait Islander children was significantly larger than non-Indigenous children (mean difference: 0.09 mm, P = 0.001). The horizontal (mean difference: 0.12 mm, P = 0.003) and vertical cup diameter (mean difference: 0.16 mm, P < 0.001) were also significantly larger in Aboriginal and Torres Strait Islander children, as were the horizontal and vertical cup-to-disc ratios (both P < 0.01). Aboriginal and Torres Strait Islander children also had a significantly thinner Bruch membrane opening minimum rim width in the superior, nasal, and temporal meridians (all P < 0.001). Peripapillary retinal nerve fiber layer thickness did not differ between groups.

CONCLUSIONS

Differences exist in the ONH structure between Aboriginal and Torres Strait Islander children and non-Indigenous children, which may have implications for the detection and monitoring of ocular disease in this population and highlights the need to extend this research to the adult population.

Presence of diabetic retinopathy is associated with worse 10-year mortality among Indigenous Australians in Central Australia: The Central Australian ocular health study

IMPORTANCE

Diabetes mellitus (DM) is highly prevalent among Indigenous Australians and contributes greatly to premature death. The association of diabetic retinopathy (DR) with early mortality, however, has not previously been reported among Indigenous Australians.

BACKGROUND

To investigate associations between 10-y mortality and the presence of DR among Indigenous Australians living in Central Australia.

DESIGN

Prospective cohort study.

PARTICIPANTS

A total of 1257 individuals aged 40 y or older, living in one of 30 remote communities within Central Australia were recruited through outreach clinics.

METHODS

Fundus examination was performed on all patients at recruitment. The presence of any DR was recorded.

MAIN OUTCOME MEASURES

Mortality rate and cause were obtained at 10 y, and their association with any DR was determined.

RESULTS

Ten-year all-cause mortality was found to be 29.3%. Of those with DM but no DR, 24.0% died during the 10 y after recruitment, compared with 40.1% for those with any DR (P < 0.0001). Those who had any DR were 75% more likely to die (hazard ratio [HR] 1.75; P < 0.0001) and were more likely to die from renal failure (HR 2.71; P = 0.004) or stroke (HR 5.91; P = 0.026).

CONCLUSION AND RELEVANCE

The presence of any DR among those with DM, was associated with a 75% greater 10-y all-cause mortality rate and were more likely to die from renal failure or stroke. We recommend that whenever DR is noted among Indigenous Australians with DM, that they be immediately referred for investigation and management of risk factors, which might predispose to renal failure and stroke.

Prevalence of glaucoma in the Australian National Eye Health Survey

AIM

To estimate the prevalence of glaucoma in Australia.

METHODS

This was a population-based study of 3098 non-Indigenous Australians (50-98 years) and 1738 Indigenous Australians (40-92 years) stratified by remoteness. Each participant underwent a standard examination that included visual field assessment, tonometry and non-mydriatic fundus photography. Two fellowship-trained glaucoma specialists independently assessed relevant case notes (past ocular history, best-corrected visual acuity, frequency doubling technology visual fields, Van Herick grade, intraocular pressure and optic disc-centred photographs) and assigned a diagnosis ranked on a scale of certainty: none, possible, probable or definite glaucoma.

RESULTS

A total of 4792 (99.1%, 3062 non-Indigenous and 1730 Indigenous) participants had retinal photographs in at least one eye that were gradable for glaucoma. The weighted prevalence of glaucoma (definite) in non-Indigenous Australians and Indigenous Australians was 1.5% (95% CI 1.0 to 2.2) and 0.6% (95% CI 0.4 to 1.1), respectively. When definite and probable cases of glaucoma were combined, rates were 3.4% (95% CI 2.7 to 4.3) among non-Indigenous and 1.6% (95% CI 1.1 to 2.3) in Indigenous Australians. Only 52.4% of non-Indigenous Australians and 28.0% of Indigenous Australians with glaucoma self-reported a known history of glaucoma.

CONCLUSION

We estimate that 198 923 non-Indigenous Australians aged 50 years and over and 2139 Indigenous Australians aged 40 years and over have glaucoma. Given the high rates of undiagnosed glaucoma coupled with a significant ageing of the Australian population, improvements in case detection and access to low vision rehabilitation services may be required to cope with the growing burden of glaucoma.

Distribution and associations of intraocular pressure in indigenous Australians within central Australia: the Central Australian Ocular Health Study

PURPOSE

To determine the distribution and associations of intraocular pressure (IOP) among the indigenous Australian population living in central Australia.

DESIGN

Clinic-based cross-sectional study.

PARTICIPANTS

1884 individuals living in one of 30 remote communities within the statistical local area of 'Central Australia'. This equated to 36% of those aged ≥20 years and 67% of those aged ≥40 years within this district.

METHODS

Participants aged 20 years or over were recruited as they presented to the eye clinic at each remote community. Of those recruited into the study, 1060 underwent IOP measurement using either a Perkins tonometer (Haag-Streit, Koeniz, Switzerland) or an ICare tonometer (Tiolat Oy, Helsinki, Finland) depending on the availability of equipment. Central corneal thickness (CCT) was also measured using ultrasound pachymetry.

MAIN OUTCOME MEASURES

The distribution and associations of IOP from the right eye of each participant is presented.

RESULTS

Mean IOP was 12.8 mmHg (SD 3.2 mmHg) and CCT was 512 µm (SD 36 µm). IOP was strongly associated with CCT (r(2) = 0.14, t = 3.87; P < 0.0001), showing an increase of 0.4 mmHg with every 10 µm increase in CCT. Furthermore, IOP was strongly associated with age, decreasing by 1.9 mmHg for every decade increase in age, but only for eyes with a CCT above the mean.

CONCLUSION

  IOP of indigenous Australians is lower than any other racial group previously published. This may relate to the low CCT readings found among this population. Clinicians will need to bear this in mind when examining indigenous Australians and make appropriate allowances for the measured IOP.

Prevalence of pseudoexfoliation syndrome in indigenous Australians within central Australia: The Central Australian Ocular Health Study

BACKGROUND

  Pseudoexfoliation syndrome (XFS) has been found to occur more commonly among indigenous Australians. This paper was designed to determine the prevalence of XFS within the indigenous Australian population living in central Australia.

DESIGN

  Clinic-based cross-sectional study.

PARTICIPANTS

  One thousand eight hundred eighty-four individuals living in one of 30 remote communities within the statistical local area of 'Central Australia' were recruited. This equated to 36% of those aged 20 years or older and 67% of those aged 40 years or older within this district.

METHODS

  Participants aged 20 years or over were recruited as they presented to the eye clinic at each remote community. Slit-lamp examination was performed, and the presence of XFS in each eye was recorded and presented.

MAIN OUTCOME MEASURE

  Prevalence and associations of XFS.

RESULTS

  XFS was present in one or both eyes of 4.7% of the individuals recruited into the study. Prevalence increased with age (5.9% of those ≥40 years and 12.7% ≥ 60 years). There was a significant association between the presence of XFS and climatic keratopathy (χ(2)  = 240.13; P < 0.00001). Notably, none of those with XFS had ocular hypertension or glaucoma.

CONCLUSION

  XFS was present in a significantly higher proportion of indigenous Australians compared with previously reported prevalence estimates among non-indigenous Australians. The association found between XFS and climatic keratopathy may represent a common causal link between the two conditions. The lack of association of XFS with ocular hypertension and glaucoma appears to be a unique feature of the indigenous Australian population, and this merits further investigation.

Prevalence and associations of cataract in indigenous Australians within central Australia: the Central Australian Ocular Health Study

PURPOSE

To determine the prevalence and associations of cataract within the indigenous Australian population living in central Australia.

METHODS

1884 individuals aged > or =20 years, living in one of 30 remote communities within the statistical local area of 'central Australia' were recruited for this study. This equated to 36% of those aged > or =20 years and 67% of those aged > or =40 years within this district. Slit-lamp examination was performed. The degree and subtype of cataract was graded using the Lens Opacities Classification System III criteria. A cataract was defined as a nuclear opalescence > or =4.0, a cortical opacity > or =3.0, a posterior subcapsular opacity > or =2.0, a visual acuity worse than 6/12 or a visual acuity worse than 6/60 due to cataract. The prevalence of cataract in one or both eyes was presented for each of the definitions.

RESULTS

Nuclear opalescence cataract was present in 13.5% (18.5% of those > or =40 years); cortical opacity cataract was present in 13.1% (17.7% of those > or =40 years); and posterior subcapsular cataract was present in 15.8% (21.0% of those > or =40 years). 12.6% of patients (17.3% of those > or =40 years) and 4.4% of patients (5.9% of those > or =40 years) had a cataract that resulted in a visual acuity of worse than 6/12 and worse than 6/60, respectively. All cataracts were associated with advancing age. Posterior subcapsular cataract was associated with self-reported diabetes.

CONCLUSION

There is a higher prevalence of cataract among indigenous Australians living within remote central Australia compared with the non-indigenous population. Services for this population need to be designed with this in mind when planning resource allocation.