Abstract
Purpose: :
To describe the SD-OCT findings in five patients with unilateral high myopia and myelinated retinal nerve fibers, previously diagnosed with anisometropic amblyopia.
Methods: :
Five patients were identified who had unilateral high myopia associated with myelinated retinal nerve fibers, who were previously diagnosed with anisometropic amblyopia. Refraction, dilated fundus examination and SD-OCT using either the Topcon Mark 1000, the Heidelberg Spectralis or the Zeiss Cirrus was performed on all five patients. Best corrected visual acuity in the "amblyopic" eyes ranged from 20/200 to 20/400. The amount of myopia in the "amblyopic" eyes ranged from -7.50 to -11.50 D. All had normal visual acuity in the fellow eye. The "amblyopic" eye in all five patients was characterized by high myopic correction and heavily myelinated retinal nerve fibers extending 360 degrees around the disc and to a greater extent along the superior arcade than the inferior arcade. The myelination extended from the optic disc in all cases and did not involve the macula. All maculas were normal on ophthalmoscopy. Retinas of all fellow eyes were normal and did not exhibit any myelination.
Results: :
The IS/OS junction line, or interface between the inner segments and outer segments of the photoreceptors (also known as the photoreceptor integrity line, or PIL), was present in the normal eyes with good visual acuity. The IS/OS junction line through the fovea was significantly attenuated or absent in the "amblyopic" eyes of all five patients. In one patient, the IS/OS line was absent on a lower resolution SD-OCT system but present and extremely attenuated using updated software with a higher resolution.
Conclusions: :
The SD-OCT demonstrates either extreme attenuation or absence of the IS/OS junction line in the maculas of five patients having unilateral high myopia and myelinated retinal nerve fibers and a normal IS/OS junction line in the fellow eye. The lack of photoreceptor integrity appears to predict a poor prognosis for treatment to improve visual acuity in such patients and belies a diagnosis of "amblyopia", since there is demonstrable structural abnormality. SD-OCT findings may contribute to the prognostic factors associated with treatment for visual improvement in "amblyopia" associated with unilateral high myopia and myelinated retinal nerve fibers. The role of the photoreceptors in this form of "amblyopia" has never been addressed in the literature to the best of our knowledge, and with recently introduced SD-OCT, photoreceptor integrity can now be easily assessed.
Keywords: imaging/image analysis: clinical • myopia • photoreceptors: visual performance