Impact of Change in Retinal Thickness on Refractive Error in the Comparison of Age-related Macular Degeneration Treatments Trials (CATT)

Abstract

 

Purpose

 

To assess the impact of change in retinal thickness on refractive error in patients treated with ranibizumab or bevacizumab for neovascular age-related macular degeneration (AMD).

 

Methods

 

CATT participants (N=1185) with neovascular AMD were randomly assigned to ranibizumab or bevacizumab. At baseline and selected follow-up visits after treatment, certified refractionists measured refractive error using subjective refraction; and certified OCT Readers measured foveal center retinal thickness, subretinal fluid thickness, and subretinal tissue complex thickness (i.e. material above the retinal pigment epithelium (RPE), the RPE, and material under the RPE).The association between thickness change and refractive error change was evaluated for each of 3 thickness measurements, total thickness, thickness of subretinal fluid and subretinal tissue complex using Spearman correlation coefficients (r) and comparisons of means.

 

Results

 

The mean spherical equivalent (SphE) in Diopters (D) shifted towards myopia in the study eye from 0.62±1.63D at baseline to 0.50±1.62D at the end of two years (p<0.001), but shifted towards hyperopia in the fellow eye from 0.40±1.66D at baseline to 0.50±1.63D at the end of two years (p=0.03). The changes in SphE of the study eye were similar by drug (-0.14±0.99D for ranibizumab, -0.09±0.87D for bevacizumab, p=0.35). Among all follow-up visits (n=9374) with both OCT thickness and SphE available in the study eye, changes in SphE were modestly correlated with changes in total thickness (r=0.22, p<0.001), thickness of subretinal fluid or subretinal tissue complex separately (r=0.14 to 0.15, p<0.001) or added together (r=0.24, p<0.001), but were not correlated with retinal thickness (r=0.02, p>0.05). While decreases in the thickness of sub-retinal fluid and sub-retinal tissue complex by less than 100 microns had little impact on SphE, decreases by 300 microns or more were associated with a myopic shift of 0.25 D (Table 1).

 

Conclusions

 

Among CATT participants, the refractive error of the study eye shifted towards myopia and was associated with decreases in thickness of subretinal fluid or subretinal tissue complex in response to treatment, but was not associated with decreases in retinal thickness.

 

 

Table 1 Mean change in spherical equivalent from baseline for each level of thickness change of subretinal fluid and subretinal tissue complex

 

Keywords: 412 age-related macular degeneration • 677 refractive error development