June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Rod Intercept Time in expanded classification of Non-neovascular Age related Macular Degeneration (AMD)
Author Affiliations & Notes
  • Shruti Chandra
    Moorfields Eye Hospital NHS Foundation Trust, London, London, United Kingdom
    University College London, London, London, United Kingdom
  • Sarega Gurudas
    Moorfields Eye Hospital NHS Foundation Trust, London, London, United Kingdom
    University College London, London, London, United Kingdom
  • Manjot Grewal
    Moorfields Eye Hospital NHS Foundation Trust, London, London, United Kingdom
  • Syed Ahmer Raza
    Moorfields Eye Hospital NHS Foundation Trust, London, London, United Kingdom
  • Sobha Sivaprasad
    Moorfields Eye Hospital NHS Foundation Trust, London, London, United Kingdom
    University College London, London, London, United Kingdom
  • Footnotes
    Commercial Relationships   Shruti Chandra None; Sarega Gurudas None; Manjot Grewal None; Syed Ahmer Raza None; Sobha Sivaprasad Bayer, Novartis, Allergan, Roche, Boehringer Ingelheim, Optos, EyeBiotech, Biogen, Apellis., Code F (Financial Support)
  • Footnotes
    Support  Fight For Sight UK, Grant 1905
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 3357. doi:
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      Shruti Chandra, Sarega Gurudas, Manjot Grewal, Syed Ahmer Raza, Sobha Sivaprasad; Rod Intercept Time in expanded classification of Non-neovascular Age related Macular Degeneration (AMD). Invest. Ophthalmol. Vis. Sci. 2023;64(8):3357.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Rod intercept time (RIT) is a measure of dark adaptation (DA) and has been shown to discriminate between AMD severity groups based on colour fundus photographs. We studied RIT in AMD severity groups sub-classified on optical coherence tomography (OCT) by comparing to a control group with healthy maculae (normal).

Methods : In this prospective, cross-sectional study we sub-classified AMD into early AMD with and without subretinal drusenoid deposits (SDD), intermediate AMD (iAMD) with or without SDD, incomplete and complete retinal pigment epithelium and outer retinal atrophy (iRORA and cRORA) groups. RIT in one eligible eye of each participant was measured using AdaptDx ( Maculogix, Hummelstown, PA, USA Ltd). After dark adaptation for 30 minutes, participants were exposed to a bleach of 83% with 505nm photoflash centred at 5o in the inferior vertical meridian. RIT was measured as time to reach a threshold of 5x10-3 cd/m2 or to a maximum test duration of 20 minutes. Delayed RIT was defined using 2 thresholds of RIT >6.5 and >12.5 minutes. Descriptive and inferential statistics were done for comparison. Spearman coefficient was used for correlation.

Results : Total 209 eyes of 209 participants were analyzed (Normal, 50; Early AMD without SDD, 22; Early AMD with SDD, 15; iAMD without SDD, 56; iAMD with SDD, 49; cRORA, 17). Table 1 shows RIT>6.5 minutes could discriminate early AMD without SDD from normal (p=0.03) but not RIT>12.5 minutes (p=0.12). Only 8% and 4% of the normal eyes had RIT>6.5 and >12.5 minutes respectively. SDD was a risk factor for delayed DA, irrespective of AMD stage. Thinner subfoveal choroidal thickness (SFCT) and higher retinal pigment epithelium-Bruchs membrane (RPE-BM) volume were significantly correlated with increasing AMD severity across both RIT thresholds (p<0.01) (Figure 1).

Conclusions : RIT>6.5 mins is effective in discriminating between normal and early AMD but not RIT>12.5 minutes. Ocular features such as SDD, iRORA, SFCT and RPE-BM volume are risk factors for prolonged RIT across the expanded AMD classification compared to a normal group.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Table shows comparison of ocular features across normal and AMD severity groups

Table shows comparison of ocular features across normal and AMD severity groups

 

Figure shows correlation plots for SFCT, ONL vol and RPE-BM with RIT across normal and AMD groups

Figure shows correlation plots for SFCT, ONL vol and RPE-BM with RIT across normal and AMD groups

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