Purpose:
To explore SD OCT images in a series of patients with achromatopsia (rod monochromatism) and reveal an OCT sign that is pathognomonic of this disorder.
Methods:
7 patients (age 16-62) with a documented clinical diagnosis of achromatopsia (including flat photopic but normal scotopic flash ERG’s) were evaluated. All had complete achromatopsia except one who was an incomplete achromat. All had long standing vision reduction and nystagmus since early childhood and none reported any progression of vision loss.The 6 complete achromats had 20/200 to 20/400 best corrected VA and no color vision. The incomplete achromats had 20/70 vision and limited color vision. SD OCTs were obtained in all 7 patients (using the Cirrus , the 3D Mark II or the Spectralis). Fundus auto-fluorescence (FAF) was also obtained.
Results:
6 of 7 achromats (including the incomplete achromat) exhibited a virtually identical SD OCT macula finding of a sharply delineated rectangular hyporeflective space in cross sectional imaging. This appears to be due to the complete absence of the IS/OS junction (photoreceptor integrity line or PIL). This space was about 800u by 600u and all adjoining structures appeared intact adjacent to it. On SD OCT "en face" images and FAF, the abnormal zone appeared oval with an FAF hypoautofluorescent oval zone. 1 of the 7 without this OCT finding was a sister of a male achromat included in this study. The siblings, ages 23 and 22, were identical clinically except, the sister had a foveal reflex OU, the brother did not. FAF revealed the characteristic dark oval in the brother only.
Conclusions:
Although not all achromats have the "pathognomonic" signs(absent PIL), its presence strongly supports the diagnosis of achromatopsia.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • photoreceptors • color vision