Fusion maldevelopment (latent/manifest latent) nystagmus syndrome: effects of four-muscle tenotomy and reattachment

Inter-Ocular Fixation Instability of Amblyopia: Relationship to Visual Acuity, Strabismus, Nystagmus, Stereopsis, Vergence, and Age

PURPOSE

Amblyopia damages visual sensory and ocular motor functions. One manifestation of the damage is abnormal fixational eye movements. Tiny fixation movements are normal; however, when these exceed a normal range, the behavior is labeled "fixation instability" (FI). Here we compare FI between normal and amblyopic subjects, and evaluate the relationship between FI and severity of amblyopia, strabismus angle, nystagmus, stereopsis, vergence, and subject age.

METHODS

Fixation eye movements were recorded using infrared video-oculography from 47 controls (15.3 ± 12.2 years of age) and 104 amblyopic subjects (13.3 ± 11.2 years of age) during binocular and monocular viewing. FI and vergence instability were quantified as the bivariate contour ellipse area (BCEA). We also calculated the ratio of FI between the 2 eyes: right eye/left eye for controls, amblyopic eye/fellow eye for amblyopes. Multiple regression analysis evaluated how FI related to a range of visuo-motor measures.

RESULTS

During binocular viewing, the FI of fellow and amblyopic eye, vergence instability, and inter-ocular FI ratios were least in anisometropic and most in mixed amblyopia (P < .05). Each correlated positively with the strabismus angle (P < .01). During monocular viewing, subjects with deeper amblyopia (P < .01) and larger strabismus angles (P < .05) had higher inter-ocular FI ratios. In all, 27% of anisometropic and >65% of strabismic/mixed amblyopes had nystagmus. Younger age and nystagmus increased FI and vergence instability (P < .05) but did not affect the inter-ocular FI ratios (P > .05).

CONCLUSIONS

Quantitative recording of perturbed eye movements in children reveal a major functional deficit linked to amblyopia. Imprecise fixation, measured as inter-ocular FI ratios, may be used as a robust marker for amblyopia and strabismus severity. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Effects of augmented tenotomy and reattachment in the infantile nystagmus syndrome

PURPOSE

To test the hypothesis that augmented tenotomy and reattachment surgery (AT-R), which involves placing an additional suture in each distal tendon during the 4-muscle tenotomy and reattachment (T-R) or other infantile nystagmus syndrome (INS) procedures, could increase the beneficial effects of many types of extraocular muscle (EOM) surgery to treat INS.

METHODS

Both infrared reflection and high-speed digital video systems were used to record the eye movements in 4 patients with INS before and after AT-R surgery. Data were analyzed using the eXpanded Nystagmus Acuity Function (NAFX) that is part of the OMtools software.

RESULTS

Placement of the augmentation suture did not interfere with Kestenbaum, Anderson, bilateral medial rectus muscle recession, or T-R surgeries. The therapeutic effects of AT-R were similar to but not equal to those from the traditional single-suture surgeries (ie, broadening longest foveation domain [LFD] but no improvement of NAFX peak). The average of the NAFX percent improvements after AT-R was within 31% of those estimated from NAFX values before T-R; the average of the percent broadenings of the LFD values after AT-R was within 16%.

CONCLUSIONS

The AT-R does not improve the foveation quality in INS above the traditional T-R surgery. It is not improved by an additional suture; indeed, some improvements may be diminished by the added suture. The hypothesized augmented-tendon suture technique (sans tenotomy) has been modified and remains to be tested.

Myectomy of the Extraocular Muscles Without Reattachment as a Surgical Treatment for Horizontal Nystagmus

PURPOSE

To report the comparative clinical findings for two nystagmus procedures in two consecutive case series: the Sinskey anterior extirpation procedure (SAEP) and a modification, myectomy without reattachment (MWR).

METHODS

Twenty consecutive patients underwent the SAEP and 19 underwent MWR. The SAEP is a snare-assisted unmeasured deep myectomy, whereas MWR is a measured myectomy at posterior Tenon's fascia. All patients underwent comprehensive ophthalmologic and orthoptic examination with infrared videonystagmography. Binocular best corrected visual acuity, nystagmus amplitude, alignment, and versions outcomes were measured.

RESULTS

The highest percentage of patients experiencing two or more lines of improvement in distance and near acuity was in the SAEP group, who were younger than 10 years and had no ocular comorbidity (100%). Distance and near acuity improved at least one line in 71% and 86% of patients in the SAEP group and 72% and 61% in the MWR group, respectively. In both groups, patients younger than 10 years had the best acuity gains. Average nystagmus amplitude was reduced 76.3% (SAEP) and 68% (MWR). Horizontal versions were more compromised in the SAEP group and one patient experienced intraoperative orbital bleeding. Patients requiring reoperation for strabismus numbered 5 of 20 (20%) in the SAEP and 3 of 19 (16%) in the MWR groups.

CONCLUSIONS

Similar to SAEP, the MWR procedure reduces nystagmus amplitudes and improves visual acuity but with less limitation of versions, risk of intraoperative bleeding, and risk of postoperative strabismus. Data suggest that early surgery (for patients younger than 10 years) can have a greater beneficial effect on postoperative visual acuity. [J Pediatr Ophthalmol Strabismus. 2016;53(3):156-166.].