Abstract
Purpose::
To evaluate paravascular retinal nerve fiber cleavage in highly myopic eyes by optical coherent tomography (OTC).
Methods::
We took fundus photographs (CR-DGi, Non-Mydriatic Retinal Camera, Canon, Tokyo, Japan) in 2210 ocular hypertension or primary open angle glaucoma patients who had been regularly followed up at National Taiwan University Hospital. Ophthalmic examinations included ocular biometry (A-scan ultrasonography, A-1500, Sonomed, Lake Success, NY, USA) and extended fundus examination after cycloplegics applications. Refraction status was determined by autorefractometer (RK-3000, Topcon, Tokyo, Japan) and expressed as spherical equivalent (sphere + 1/2 cylinder) in diopters (D). Visual field examination (30-2, Allergan Humphrey, San Leandro, CA, USA) and OCT (STRATUS, Model 3000, Carl Zeiss Meditec, Dublin, CA, USA) were performed on a 6- month basis for these patients.
Results::
There were 22 (8 male, 14 female) patients, with the mean age of 40.1±13.2 (range: 19-65) year-old, had paravascular retinal nerve fiber cleavage in the fundus photographs. It occurred bilaterally in 9 cases. Their mean refraction status was -9.33±3.32 (-5.83 to -13.0) D, and axial length was 26.69±1.31 (24.80 to 28.65) mm. The locations of cleavage were 65.2% in the superior (11, 12, and 1 o’clock), 30.4% in the inferior (5, 6, and 7 o’clock), 2.2% in temporal, and 2.2% in nasal. OCT revealed inner retinal interruption and cyst formation with some preserved retinal nerve fiber layer in these locations. More advanced lesions showed cavities without any nerve fiber layer. Vitreous condensation or traction was associated with some locations of cleavage and opercula were found near these sites. The thickness of cleavage areas was much thinner as compared to the adjacent healthy retina. No corresponding visual field defect was noted by Humphrey 30-2 program.
Conclusions::
The paravascular retinal nerve fiber cleavage may be associated with the vitreous degeneration in highly myopic eyes. This mechanism of retinal nerve fiber damage is different from that happens in glaucoma.
Keywords: myopia • nerve fiber layer • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)