Analysis of Retinal Nerve Fiber Layer Thickness in Patients With Superior Segmental Optic Hypoplasia

PURPOSE: To analyze the thickness of the peripapillary retinal nerve fiber layer (RNFL) in patients with superior segmental optic hypoplasia (SSOH) using optical coherence tomography (OCT). METHODS: Ten eyes of 10 patients with SSOH and 20 eyes of 20 subjects as normal control were evaluated. The peripapillary RNFL thickness measured by Stratus OCT was compared between the two groups. RESULTS: The mean RNFL thickness was significantly different between SSOH patients (72.35+/-14.77 micrometer) and normal subjects (111.61+/-6.62 micrometer) (p<0.001). The extent to which the RNFL thickness was below 5 percentile of normal subjects on the TSNIT graph was from the 41.7+/-15.53 to 110.1+/-7.47 scan number, which corresponded mainly with the superior nasal region. Moreover, in a clock-hour analysis, the peripapillary RNFL thic kness of the SSOH patients decreased significantly from 10 o'clock to 6 o'clock compared to normal subjects (p<0.01). CONCLUSIONS: Peripapillary RNFL thickness in patients with SSOH was reduced in the superior, nasal, and inferior regions. Further studies involving larger populations of patients should be performed to verify these findings.

Two Cases of Topless Optic Disc Syndrome

Topless optic disc syndrome is considered as congenital optic nerve hypoplasia.The risk factors of this syndrome are female sex, prematurity and history of maternal diabetes.Normal central visual acuity, thinning of superior peripapillary nerve fiber layer and corresponding inferior visual field defects are the characteristic features of this syndrome.Relative superior entrance of central retinal vessels and superior scleral halo can be found in patients with this syndrome. We experienced two cases of topless optic disc syndrome :one was unilateral and the other, bilateral. They had no history of maternal diabetes. Diffuse superior retinal nerve fiber layer atrophy and inferior visual field defects were observed.Pallor of superior optic neural rim, relative superior entrance of central retinal vessels and superior scleral halo were also observed. It will be necessary to differentiate these findings from glaucomatous optic disc damage and visual field defects.