The Effect of Horizontal Rectus Muscle Surgery on Clinical and Eye Movement Recording Indices in Infantile Nystagmus Syndrome

Clinical and Electrophysiological Outcomes After Eye Muscle Surgery in 81 Adults With Infantile Nystagmus Syndrome

PURPOSE

To characterize the effects of eye muscle surgery on patients older than 18 years with infantile nystagmus syndrome (INS) who have had only optical treatment.

METHODS

This was a prospective, single-center, interventional case series analysis of clinical and electro-phyisological data before and after surgery. Outcome measures included: clinical characteristics, surgical procedure, and preoperative and postoperative binocular best corrected visual acuity (BCVA) in the null position, anomalous head posture (AHP), contrast sensitivity, strabismic deviation, and nystagmus acuity function (NAFX). Postoperative data used were collected for a minimum of 12 months after surgery. Parametric and non-parametric statistical analysis of the outcome measures was performed.

RESULTS

Ages ranged from 18 to 72 years (average: 36 years) and follow-up from 12 to 74 months (average: 26 months). A surgical algorithm of nine separate procedures involving at least two recti muscles on each eye was used for each patient. Most patients had associated systemic and/or ocular diagnoses, including albinism (35%), amblyopia (23%), optic nerve or retinal disorders (48%), refractive error (80%), AHP (44%), aperiodicity (27%), and strabismus (69%). There were no serious surgical complications, with a reoperation rate of 12%. There were significant group mean increases in BVCA, AHP, contrast sensitivity, strabismic deviation, and NAFX after surgery. Sixty percent of patients who were legally ineligible for driving prior to surgery became eligible after eye muscle surgery.

CONCLUSIONS

Adult patients with INS showed sustained improvement in many afferent and efferent measures of visual function after eye muscle surgery. [J Pediatr Ophthalmol Strabismus. 2021;58(2):93-104.].

Infantile nystagmus syndrome: clinical characteristics, current theories of pathogenesis, diagnosis, and management

Infantile nystagmus syndrome (INS) is an important clinical diagnosis because it is a common presenting sign of many ocular, neurologic, and systemic diseases. Although INS has been studied for more than a century, its diagnosis and treatment remains a challenge to clinicians because of its varied manifestations and multiple associations, and its pathogenesis continues to rouse considerable scientific debate. Fueled by these challenges, recent basic research and clinical investigations have provided new insights into INS. New genetic discoveries and technological advances in ocular imaging have refined our understanding of INS subtypes and offer new diagnostic possibilities. Unexpected surgical outcomes have led to new understanding of its pathogenesis based on novel hypothesized pathways of ocular motor control. Comparative studies on nonhuman visual systems have also informed models of the neural substrate of INS in humans. This review brings together the classic profile of this disorder with recent research to provide an update on the clinical features of INS, an overview of the current theories on how and why INS develops, and a practical approach to the diagnosis and management of INS.

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.].

Effect of Photorefractive Keratectomy on Nystagmus and Visual Functions in Myopic Patients With Infantile Nystagmus Syndrome

PURPOSE

To determine the effect of photorefractive keratectomy (PRK) on involuntary eye movements, visual acuity, and contrast sensitivity in myopic patients with infantile nystagmus syndrome.

DESIGN

Prospective interventional case series.

METHODS

This study was conducted on patients with infantile nystagmus syndrome and myopia equal to or more than -1 diopter (D), who were referred to our clinic over a 2-year period. Patients older than 18 years of age with a stable refraction for at least 1 year who were good candidates for PRK were included. Complete ophthalmologic examinations including assessment of best-corrected visual acuity (BCVA), contrast sensitivity, and videonystagmography were performed for all patients before and 3 months after surgery.

RESULTS

Twenty-four eyes of 12 patients with mean age of 23 ± 2 years were enrolled in this study. Spherical equivalent refractive error was -2.82 ± 1.65 D and -0.26 ± 0.25 D before and after PRK, respectively (P < .001). Monocular BCVA improved from 0.36 ± 0.21 logMAR to 0.27 ± 0.25 logMAR and binocular BCVA improved from 0.33 ± 0.2 logMAR to 0.17 ± 0.16 logMAR (P < .001). Contrast sensitivity significantly improved at low (P < .001), intermediate (P < .001), and high frequencies (P = .01). The frequency, amplitude, and intensity of nystagmus were significantly decreased after PRK (P < .001). There was no correlation between the degree of myopia correction and improvement in sensory and motor indices of nystagmus (P > .1, Spearman correlation coefficient).

CONCLUSION

PRK in patients with infantile nystagmus syndrome and myopia improved monocular and binocular BCVA and contrast sensitivity. Furthermore, motor indices of nystagmus (frequency, amplitude, and intensity) were significantly improved after surgery in these patients.

Nystagmus in pediatric patients: interventions and patient-focused perspectives

Nystagmus refers to involuntary, typically conjugate, often rhythmic oscillations of the eyes. The most common cause of nystagmus in children is infantile nystagmus syndrome (INS). INS presents within the first few months of life and is sometimes accompanied by an ocular condition associated with sensory impairment. Because this condition affects a person throughout life, it is important to understand the options available to manage it. This review focuses on the underlying nystagmus etiology, psychosocial and functional effects of nystagmus, as well as current principles of management, including optical, pharmacological, surgical, and rehabilitative options. Currently, the neural mechanisms underlying INS are not fully understood. Treatment options are designed to increase foveation duration or correct anomalous head postures; however, evidence is limited to mainly pre- and post-study designs with few objective comparisons of treatment strategies. Management of INS should be individualized. The decision on which treatment is best suited for a particular patient lies with the patient and his/her physician.

Topical brinzolamide (Azopt) versus placebo in the treatment of infantile nystagmus syndrome (INS)

PURPOSE

To test the hypothesis that the topical carbonic anhydrase inhibitor brinzolamide (Azopt) has beneficial effects versus placebo on measures of nystagmus and visual acuity in adult subjects with infantile nystagmus syndrome (INS).

DESIGN

Prospective, cross-over, double masked clinical trial.

METHODS

SETTING

Single centre.

STUDY POPULATION

Five subjects ≥18 years old with typical INS and best-binocular visual acuity in their primary position null zone ETDRS 55 letters to 85 letters (20/200 to 20/50) and had no previous treatment for nystagmus.

INTERVENTION

In a randomised order, each subject received one drop of Azopt or placebo in both eyes three times a day separated by a washout period of at least a week followed by Azopt or placebo in both eyes three times a day; thus each subject got the drug and placebo, each acting as his or her own control.

OUTCOME MEASURES

The nystagmus acuity function and INS waveforms obtained from eye movement recordings, binocular optotype visual acuity, using the ETDRS protocol analysed individually and as a group before and after Azopt and placebo.

RESULTS

Versus placebo and baseline measures, topical Azopt significantly improved; INS waveform characteristics in the primary position null zone, group mean values of the nystagmus acuity function across gaze (p<0.01) and group mean ETDRS binocular letter visual acuity (p<0.05). There was a predictable decrease in intraocular pressure (IOP) without any systemic or ocular adverse events.

CONCLUSIONS

Although a prospective large-scale clinical trial is needed to prove effectiveness, an eye-drop-based therapy for INS may emerge as a viable addition to optical, surgical, behavioural and systemic drug therapies for INS.

TRIAL REGISTRATION NUMBER

NCT01312402.

Improved visual acuity and recognition time in nystagmus patients following four-muscle recession or Kestenbaum-Anderson procedures

PURPOSE

Many patients describe more rapid recognition of objects after surgical procedures for nystagmus; however, this "recognition time" is not reflected in the parameters typically studied in these patients. The purpose of this study is to assess the effect of nystagmus surgery on visual acuity and recognition time.

METHODS

In this prospective, interventional, comparative case series, patients with nystagmus were divided into two groups. group A (n = 13) underwent four-muscle retroequatorial recession; group B (n = 8) underwent the Kestenbaum-Anderson procedure. Visual acuity, binocularity, and recognition time were assessed before and after surgery. Recognition time was measured in a routine examination setting using specially designed software that controlled the time of appearance of optotypes in 0.1 second increments.

RESULTS

A total of 21 patients were enrolled. The entire group experienced significant postoperative improvement in visual acuity (P = 0.002) and recognition time (P = 0.005). The mean improvement in recognition time was 0.3 seconds at maximum preoperative visual acuity level. A trend toward more improvement in group A than in group B was not statistically significant.

CONCLUSIONS

Both the four-muscle recession and the Kestenbaum-Anderson procedures resulted in a 1- to 2-line improvement in visual acuity and a 0.3 second improvement in optotype recognition time.

The functional significance of foveal abnormalities in albinism measured using spectral-domain optical coherence tomography

PURPOSE

The relationship between foveal abnormalities in albinism and best-corrected visual acuity (BCVA) is unclear. High-resolution spectral-domain optical coherence tomography (SD OCT) was used to quantify foveal retinal layer thicknesses and to assess the functional significance of foveal morphologic features in patients with albinism.

DESIGN

Cross-sectional study.

PARTICIPANTS

Forty-seven patients with albinism and 20 healthy control volunteers were recruited to the study.

METHODS

Using high-resolution SD OCT, 7×7×2-mm volumetric scans of the fovea were acquired (3-μm axial resolution). The B scan nearest the center of the fovea was identified using signs of foveal development. The thickness of each retinal layer at the fovea and foveal pit depth were quantified manually using ImageJ software and were compared with BCVA.

MAIN OUTCOME MEASURES

Total retinal thickness, foveal pit depth, photoreceptor layer thickness, and processing layer thickness in relation to BCVA.

RESULTS

Total photoreceptor layer thickness at the fovea was correlated highly to BCVA (P = 0.0008; r = -0.501). Of the photoreceptor layers, the outer segment length was correlated most strongly to BCVA (P<0.0001; r = -0.641). In contrast, there was no significant correlation between either total retinal thickness or pit depth and BCVA (P>0.05). This was because of an inverse correlation between total photoreceptor layer thickness and total processing layer thickness (P<0.0001; r = -0.696).

CONCLUSIONS

Neither the total retinal thickness nor the pit depth are reliable indicators of visual deficit, because patients with similar overall retinal thickness had widely varying foveal morphologic features. In albinism, the size of the photoreceptor outer segment was found to be the strongest predictor of BCVA. These results suggest that detailed SD OCT images of photoreceptor anatomic features provide a useful tool in assessing the visual potential in patients with albinism.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.