Extended Slow Phase in Latent/Manifest Latent Nystagmus

PURPOSE. To investigate the slow phase in latent/manifest latent nystagmus (LMLN) by producing long eye-drift intervals devoid of fast phases (extended slow phases [ESPs]) and to relate ESP metrics to clinical findings. METHODS. Ten patients with LMLN had eye movements recorded while attending to paired visual and auditory cues presented to their left or right. Patients compared location of the visual target with that of the subsequently heard tone. The auditory cue and the comparison task directed attention away from vision and delayed the fast-phase onset to obtain ESPs. ESP metrics were analyzed with regard to patients' clinical characteristics. Five patients' data were further explored by isolating slow-phase components. RESULTS. All patients exhibited ESPs that resembled the usual slow phase but lasted two to three times longer. Five patients maintained alignment, whereas the other five made vergence movements. Greater eye velocity, excursion, and convergence during an ESP were associated with poor vision and large uncorrected esotropia. These metrics decreased when the viewing eye was in adduction, compared with primary position or abduction. Slow-phase components found in five patients consisted of a dominant decreasing-velocity or linear drift and a low-amplitude periodic oscillation. 1,3 It was suggested therefore that these two nystagmus types be combined into one entity, latent/manifest latent nystagmus (LMLN). CONCLUSIONS. Shifting attention away from vision reliably delays 6 Therefore, characterization of the slow phase is essential for understanding the ocular motor instability in nystagmus. Slow-phase duration is usually short because of its interruption by the fast phase. We searched for a way to modify nystagmus to obtain longer intervals of slow phase that could facilitate its investigation. It has been noticed that after the abolishment of the visual target in the dark the nystagmus cycle becomes less regular, and if a distracting mental task (such as performing mental arithmetic) is added to that, the onset of the fast phase can be delayed (Goldstein HP, et al. IOVS 1992;33: ARVO Abstract 2298-84; Gradstein L, et al. IOVS 1996;37:ARVO Abstract 1030)

Ocular manifestations of congenital insensitivity to pain: a long-term follow-up

AimTo describe ocular manifestations in children with congenital insensitivity to pain with and without anhidrosis (CIPA and CIP).MethodsWe reviewed records of eye examinations of 39 children diagnosed with CIPA or CIP. We collected clinical data, with particular attention to ocular surface findings. Corneal sensitivity was tested by presence of a blink reflex upon touching the cornea. Statistical analysis assessed differences in manifestations between the two conditions, and relationships among corneal sensitivity, presence of corneal opacities and visual acuity (VA).ResultsCIPA was diagnosed in 32 children and CIP in 7. The median follow-up periods were 50 months (CIPA group) and 94 months (CIP group). Corneal opacities were present in 23% of CIPA eyes and in 57% of CIP eyes. A blink reflex was positive in 52% of CIPA eyes and in 33% of CIP eyes. We recorded VA ≥20/25 in 36% of CIPA eyes, whereas all patients with CIP had VA ≤20/30. For the whole cohort, we found a negative correlation between a preserved blink reflex and the presence of corneal opacities, and a positive correlation between a preserved blink reflex and VA ≥20/25.ConclusionChildren with congenital insensitivity to pain are prone to develop corneal scarring. Patients with CIP tend to have more severe ocular surface disease than those with CIPA, probably due to more prevalent loss of corneal sensation. In both groups, a preserved blink reflex correlated with good vision. Affected children should have close follow-up to promptly treat ocular surface disease and prevent vision loss.</jats:sec