JOIN NOW

Is A Single Measurement Enough? – Why Spatial Considerations are Important in Diagnostic Tool in Age Related Macular Degeneration

by | May 1, 2024 | Guest Column | 0 comments

Meenakshi Kumar, M.Sc Clinical Ophthalmology and Vision Research (COVR)

Doctoral Candidate, University of New South Wales, Sydney, Australia

 

Age related macular degeneration (AMD) is a progressive multifactorial senile ocular disease that remains an enigma with unknown causality. It is the major cause of vision loss worldwide. (1) Its pathogenesis involves loss of integrity of RPE-choroid complex (2,3) with ageing and accelerated by several other risk factors, oxidative stress, systemic vascular disorders, genetic factors, environmental factors, lifestyle, nutrition, history of cataract surgery to name a few. (4-6) Degeneration of the choroid is thought to be an early and possibly leading event in AMD pathogenesis with early changes noted in choriocapillaris are suggestive of this declaration. (2,7)

Figure 1: Image showing subretinal deposits in AMD – Basal laminal deposits (BLinD) and Basal linear deposits(BLamD) – occur in the basal layer of the Bruch’s membrane in the choroid.

AMD is also shown to be topographically selective in the early stage indicating a parafoveal susceptibility.(8) But the choroidal basis for this remains elusive. Recent retinal studies have indicated a difference in specific topographical arrangement of retinal thickness in normal vs AMD population. (9) It is therefore reasonable to expect these changes in the choroidal layer.

Current tools of choroidal assessment

The current tool in the clinic to assess choroidal vasculature include Indocyanine green, which is the gold standard but is invasive and considered risky in the presence of systemic vascular disease (not uncommon in AMD), second test is OCT-A which is an excellent tool for non-invasive retinal vasculature quantification but has limited use in choroidal vasculature due to quantification limitation and poor penetration till choroid, and thirdly, routine OCT, where choroidal thickness can be extracted but it has poor sensitivity to early changes in AMD, it doesn’t directly provide information about the choroidal vasculature.(10)

My current research in choroidal angioarchitecture with the use choroidal vascularity index (CVI) in healthy population has displayed the existence of specific pattern of topography (unpublished data) which is interested and in conjunction with a disease group might provide deeper understanding of vascular basis to AMD.

Future direction

With the knowledge that both retinal thickness and choroidal angioarchitecture changes with different eccentricities, it is important to consider this before planning future research in this field. The current treatment for AMD is only in its  advanced stages and with anti-vascular endothelial growth factor (VEGF). In the medicine field there is a saying “prevention is better than cure”.  Since there is no absolute cure to AMD yet, we must look at any possibilities to prevent this. Studies in choroidal vascularity might provide the biomarkers we need to do so.

Conclusion

In conclusion, studies planning to assess retina or choroid for any posterior eye disease, particularly AMD, must bear in mind that these factors change in spatial topography with different eccentricities which must be accounted for.

 

Reference :

  1. Fleckenstein M, Keenan TD, Guymer RH, Chakravarthy U, Schmitz-Valckenberg S, Klaver CC, Wong WT, Chew EY. Age-related macular degeneration. Nature reviews Disease primers. 2021 May 6;7(1):1-25.
  2. Farazdaghi MK, Ebrahimi KB. Role of the choroid in age-related macular degeneration: a current review. Journal of ophthalmic & vision research. 2019 Jan;14(1):78.
  3. Nivison-Smith L, Milston R, Madigan M, Kalloniatis M. Age-related macular degeneration: linking clinical presentation to pathology. Optometry and vision science. 2014 Aug 1;91(8):832-48.
  4. Chakravarthy U, Wong TY, Fletcher A, Piault E, Evans C, Zlateva G, Buggage R, Pleil A, Mitchell P. Clinical risk factors for age-related macular degeneration: a systematic review and meta-analysis. BMC ophthalmology. 2010 Dec;10(1):1-3.
  5. Armstrong RA, Mousavi M. Overview of risk factors for age-related macular degeneration (AMD). Journal of Stem Cells. 2015 Jul 1;10(3):171.
  6. Evans JR. Risk factors for age-related macular degeneration. Progress in retinal and eye research. 2001 Mar 1;20(2):227-53.
  7. Mullins RF, Johnson MN, Faidley EA, Skeie JM, Huang J. Choriocapillaris vascular dropout related to density of drusen in human eyes with early age-related macular degeneration. Investigative ophthalmology & visual science. 2011 Mar 1;52(3):1606-12.
  8. Clinical Practice Guide for the diagnosis, treatment, and management of Age-Related Macular Degeneration. Optometry Australia. 2019.
  9. Trinh M, Khou V, Kalloniatis M, Nivison-Smith L. Location-specific thickness patterns in intermediate age-related macular degeneration reveals anatomical differences in multiple retinal layers. Investigative Ophthalmology & Visual Science. 2021 Oct 4;62(13):13-.
  10. Koh LH, Agrawal R, Khandelwal N, Sai Charan L, Chhablani J. Choroidal vascular changes in age‐related macular degeneration. Acta Ophthalmologica. 2017 Nov;95(7):e597-601.

 

 

 

 

Author:-

Meenakshi is a doctoral candidate working at the University of New South Wales. She is currently working on exploring the vascular basis or the hemodynamic behind the multifactorial disease Age Related Macular Degeneration(AMD) at the Centre of Eye Health. She also supervises 5th optometry in their research projects as a co-supervisor. She studied her B.S optometry at the prestigious Elite School of Optometry, Chennai and did her master’s at the Glasgow Caledonian University in Scotland. She has worked extensively on posterior segment diseases such as Diabetic retinopathy, Pachychoroid vasculopathy , Central serous chorioretinopathy. She has also explored the role of Virtual reality in clinical assessment of low vision participants and role of gait analysis in Diabetic neuropathy and retinopathy. She has contributed to the scientific community with numerous journal articles and presented her work at national and international scientific platforms.

 

 

Submit a Comment