Abstract
Purpose: :
To find a reliable parameter on Optical Coherence Tomography (OCT) to predict (recurrent) activity of Choroidal Neovascular membranes (CNV) in myopes during their photodynamic therapy (PDT) course.
Methods: :
In a retrospective case series from 1 center, we included 18 eyes of 18 myopes with an small classic juxta– or subfoveal CNV, which were all treated with PDT. At 3–monthly follow–up sessions, fluorescein angiography (FA) and OCT features were compared to assess the need for retreatment. FA’s were graded as obviously active, minimally active, and inactive/staining. The presence of subretinal fluid (SRF), intraretinal fluid and retinal thickness on OCT were correlated with the presence of leak on FA. The ratio of the retinal thickness of retina overlying the CNV versus normal retina was calculated , using the most representative of 6 radial scans centered on the best possible fixation the patient could manage.
Results: :
Our 18 patients completed a follow–up time between 6 and 24 months (mean = 12 months). Their myopia ranged from –1.5 up to –11 dioptres (D) (mean = –7.5D). Their mean age was 63 years of age (range 32 – 85). Overall, the CNV’s were quoted as leaking on FA with reliable OCT measurements on 46 visits. Subretinal fluid was seen only at 7 visits (15%), cystoid macular edema at 2 visits (4%), intraretinal cysts at 4 visits (8.7%), and a pigment epithelial detachment at 1 visit on OCT imaging. On 21 visits, the CNV’s were quoted as not leaking on FA, with reliable OCT images all showing a flat retina without fluid. The mean retinal thickness ± standard error of the mean (SEM) on OCT in the obviously active group, the minimally active group and the inactive group on FA was 336.8µ ± 16.5, 310.1µ ± 19.1 and 249.3µ ± 8.1 respectively. (p–value<0.0001 and p = 0.012 for the obviously active group/ inactive group and for the minimally active group/ inactive group respectively)
The mean ratio of retinal thickness ± SEM on OCT in the obviously active group, the minimally active group and the inactive group was 1.64 ±0.08, 1.52 ±0.09, and 1.21±0.05 respectively. (p–value <0.0001 and p=0.0038 for the obviously active group/ inactive group and for the minimally active group/ inactive group respectively)
Conclusions: :
Where interpretation of FA for small CNV’s in myopes can be difficult, and where OCT features are not as obvious for activity of CNV in myopes as in non – myopic patients, calculation of the ratio of the retinal thickness of retina overlying the CNV versus normal retina can reveal the true nature of the CNV in myopes.
Keywords: photodynamic therapy • imaging/image analysis: clinical • myopia