Miho Sato

Magnetic resonance imaging and tendon anomaly associated with congenital superior oblique palsy

PURPOSE To assess the relationship between tendon anomalies and the volume of the superior oblique muscle in patients with congenital unilateral superior oblique palsy. METHODS Thirty-three patients with unilateral congenital superior oblique palsy were enrolled. Coronal, cross-sectional magnetic resonance imaging scans of the superior oblique muscle were obtained, and the volume of the paretic superior oblique muscle belly was calculated as a percentage of the superior oblique muscle belly on the normal side. The percentage volume of the affected superior oblique muscle was compared retrospectively with the angle of the vertical deviation in the primary position, the tendon looseness determined by a traction test, and other intraoperative findings. RESULTS When a tendon was loose, the volume of its muscle belly was significantly smaller than the belly of muscles with a normal taut tendon (Mann-Whitney U test, P = .0005). The average vertical deviation of patients assessed to have loose tendons was 4.80 prism diopters, and the deviation in patients with normal tendons was 9.90 prism diopters. The mean vertical deviation of patients with atrophic muscle belly on magnetic resonance imaging was 18.1 prism diopters, and that with normal muscle structure was 10.1 prism diopters. The cases with loose tendon as determined by the traction test after administration of general anesthesia and the cases with atrophic muscle belly had significantly larger vertical deviation in the primary position than the cases with normal tendons and muscles. (Mann-Whitney U test, P = .01 and .0196, respectively). CONCLUSIONS The traction test is sensitive enough to detect anomalies of the superior oblique tendons. Anomalous superior oblique tendons are nearly always associated with attenuated superior oblique muscle and this information provides us with an explanation for the phenomenon of laxity of the superior oblique tendon.

Two novel mutations in the EYS gene are possible major causes of autosomal recessive retinitis pigmentosa in the Japanese population.

Retinitis pigmentosa (RP) is a highly heterogeneous genetic disease including autosomal recessive (ar), autosomal dominant (ad), and X-linked inheritance. Recently, arRP has been associated with mutations in EYS (Eyes shut homolog), which is a major causative gene for this disease. This study was conducted to determine the spectrum and frequency of EYS mutations in 100 Japanese arRP patients. To determine the prevalence of EYS mutations, all EYS exons were screened for mutations by polymerase chain reaction amplification, and sequence analysis was performed. We detected 67 sequence alterations in EYS, of which 21 were novel. Of these, 7 were very likely pathogenic mutations, 6 were possible pathogenic mutations, and 54 were predicted non-pathogenic sequence alterations. The minimum observed prevalence of distinct EYS mutations in our study was 18% (18/100, comprising 9 patients with 2 very likely pathogenic mutations and the remaining 9 with only one such mutation). Among these mutations, 2 novel truncating mutations, c.4957_4958insA (p.S1653KfsX2) and c.8868C>A (p.Y2956X), were identified in 16 patients and accounted for 57.1% (20/35 alleles) of the mutated alleles. Although these 2 truncating mutations were not detected in Japanese patients with adRP or Lebers congenital amaurosis, we detected them in Korean arRP patients. Similar to Japanese arRP results, the c.4957_4958insA mutation was more frequently detected than the c.8868C>A mutation. The 18% estimated prevalence of very likely pathogenic mutations in our study suggests a major involvement of EYS in the pathogenesis of arRP in the Japanese population. Mutation spectrum of EYS in 100 Japanese patients, including 13 distinct very likely and possible pathogenic mutations, was largely different from the previously reported spectrum in patients from non-Asian populations. Screening for c.4957_4958insA and c.8868C>A mutations in the EYS gene may therefore be very effective for the genetic testing and counseling of RP patients in Japan.

Comparison of Muscle Volume Between Congenital and Acquired Superior Oblique Palsies by Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) studies of superior oblique (SO) muscles have revealed a high incidence of SO muscle atrophy/hypoplasia in congenital SO palsy patients. It has also been reported that long-standing acquired SO palsy patients show atrophic SO muscles in the affected eye. The purpose of this study was to compare the incidence of SO muscle atrophy/hypoplasia in congenital and acquired SO palsy by utilizing MRI. Coronal MRI image planes were taken from 29 cases of unilateral congenital SO palsy and 9 cases of acquired unilateral SO palsy patients. The SO muscle bellies were traced and their sizes were measured from each image plane. The total volume of the affected superior oblique muscle was compared with that of the normal fellow eye. The mean volume of the affected superior oblique muscle to that of the normal muscle was 45.3% (SD = 30.1) in the congenital group and 65.8% (SD = 22.7) in the acquired group. The volume reduction of the SO muscle in congenital SO palsy patients appears to be mainly a congenital abnormality rather than a secondary change, as seen in acquired SO palsy patients.

Multifocal pupillary light response fields in normal subjects and patients with visual field defects

The optimal conditions for recording focal pupillary light responses with a multifocal stimulation technique were determined, and the technique was applied to normal subjects and patients with visual field defects. Thirty-seven hexagonal stimuli were presented on a TV monitor with a visual field of 40 degrees diameter under a constant background illumination. Using a slow (4.7 Hz) m-sequence, reliable focal responses were obtained in both normal subjects and patients. The pupillary field and visual field were well correlated in patients with retinal diseases, but the correlation was not strong in patients with optic-nerve diseases. Pupillary light responses were reduced in the blind hemifield in patients with post-geniculate lesions. These results indicate that the multifocal stimulation technique can be used clinically to obtain a pupillary field for objective visual field testing.

Myectomy of Lateral Rectus Muscle for Third Nerve Palsy

PURPOSE To introduce myectomy of the lateral rectus muscle for correcting exotropia in patients with third nerve palsy. METHODS The lateral rectus muscle of the paretic eye was myectomized without suturing it to the globe. This was combined with a medial rectus muscle resection and a contralateral lateral rectus muscle recession. Magnetic resonance imaging was performed to observe the re-attachment of the lateral rectus muscle to the globe. RESULTS The patient was able to fuse in the primary position without any noticeable limitation in abduction. Magnetic resonance imaging showed that the lateral rectus muscle was attached to the globe through fibrous tissue. CONCLUSION Myectomy of the lateral rectus muscle is an effective and simple procedure to accomplish a super-maximal weakening effect of abduction in patients with complete third nerve palsy.

Loss of stereopsis with optic chiasmal lesions and stereoscopic tests as a differential test.

OBJECTIVE To identify and characterize the loss of stereopsis observed in patients with lesions of the optic chiasm. STUDY DESIGN Cross-sectional study. PARTICIPANTS Forty-three patients who had good visual acuity with orthophoria and without strabismologic histories were divided into two groups. Group 1 consisted of 13 patients with lesions involving the optic chiasm (regardless of their visual field loss) diagnosed by magnetic resonance imaging findings. Group 2 (control group) consisted of 30 patients who had large absolute visual field defects as a result of other causes, including 11 intracranial disorders other than optic chiasmal lesions, 11 cases of open-angle glaucoma, and 8 patients with lesions of the retina. METHODS The stereoacuity and visual field in each case in group 1 (before and after surgery) and group 2 were assessed, and the results were compared. MAIN OUTCOME MEASURES Stereoacuity was assessed by the Titmus stereo test (normal value for circle, 6/9; 80 seconds of arc) and by Lang-stereotest (normal value for circle, 3/3; 350 seconds of arc). Visual field was evaluated by Goldmann and Humphrey perimetry (conventional perimetry), the starlight test (binocular visual field test), and scanning laser ophthalmoscopic microperimetry (microperimetry). RESULTS Before surgery, 11 of 13 cases (85%) in group 1 failed stereo tests, and after surgery, 5 of 13 cases (38%) in group 1 failed stereo tests. Before surgery, four patients who failed stereo tests showed no absolute scotoma by Humphrey or Goldmann analysis; after surgery, one patient who failed stereo tests showed no absolute scotoma by Humphrey or Goldmann analysis. However, starlight testing showed complete bitemporal hemianopsia only under binocular conditions, and microperimetry demonstrated a relative bitemporal hemianopsia at the fixating point. No patient failed in the Titmus circle test, but one patient in group 2 failed the Lang test (3%). The patients with chiasmal lesions significantly lost the ability of stereopsis compared with other diseases (group 1 [before or after surgery] vs. group 2, P < 0.001, Fishers exact test). Conventional perimetry was unable to measure scotomas within 3 degrees of the fixation point, which is the key area for acute foveal stereopsis, because of an attached observational mirror. CONCLUSIONS The difficulty with stereopsis in patients with lesions of the optic chiasm is most likely caused by the compression of the decussating optic nerve fibers resulting in the loss of an overlapping visual field at the fixation point. Stereo tests were demonstrated to be simple and effective adjunctive tests for suspected chiasmal compression.

Development of Stereoscopic Acuity: Longitudinal Study Using a Computer-based Random-dot Stereo Test

PurposeTo investigate the development of stereoscopic acuity (stereoacuity) in children longitudinally.MethodsSeven full-term normal infants whose age at the beginning of the study was between 12 and 23 weeks were studied. A computer-based random-dot test of stereoscopic vision (TV-Random Dot Stereo Test) was used to measure stereoacuity. The test was repeated at 2- to 3-month intervals until the children reached 2 years of age, and then every 6 to 12 months until they reached 5 years of age.ResultsAll of the infants were found to have a stereoacuity of 2480 seconds of arc (2480″) with this test by 26 weeks of age. The first reliable measurement of stereoacuity was obtained from a 16-week-old infant. Stereoacuity did not improve significantly between 6 and 12 months, but it improved rapidly after 12 months. All children had a stereoacuity of 100″ with the Titmus Stereo Tests at 5 years of age, but the best stereoacuity with the TV-Random Dot Stereo Test was 229″ at 28.9 months.ConclusionsThe development of stereoacuity studied longitudinally was similar to that obtained by cross-sectional studies. The TV-Random Dot Stereo Test is a useful program for measuring stereopsis in preverbal children. Jpn J Ophthalmol 2005;49:1–5

Central Corneal Thickness in Japanese Children

PurposeTo determine the central corneal thickness (CCT) in Japanese children and to investigate the changes in CCT with increasing age.MethodsPachymetry was performed on 338 eyes of 169 patients undergoing eye muscle surgery under general anesthesia, and the intraocular pressure (IOP) was measured on 312 eyes of 156 of those same patients. Patients with abnormalities other than refractive errors and strabismus were excluded. Patients were divided into four groups: group 1, ≤1 year of age; group 2, 2–4; group 3, 5–9; and group 4, 10–18 years of age. Analysis of variance (ANOVA) was performed to determine the significance of the changes in CCT.ResultsThe average CCT of the right eye was 544.3 ± 36.9 μm. The CCT was thinner in group 1 than in groups 3 and 4 (ANOVA, P = 0.02). There was a positive but weak correlation between IOP and CCT (IOP = 6.253 + 0.014 × CCT; r2 = 0.047, P = 0.007).ConclusionsCCT reaches the adult thickness in Japanese children by age 5 years. The average CCT is thinner in Japanese children than in Caucasians but thicker than in African American children.

Magnetic Resonance Imaging of the Medial Rectus Muscle of Patients with Consecutive Exotropia after Medial Rectus Muscle Recession

PURPOSE To investigate the morphologic characteristics of the medial rectus muscle in patients with consecutive exotropia. DESIGN Retrospective, nonrandomized, interventional study. PARTICIPANTS AND CONTROLS Eleven eyes of 10 patients with consecutive exotropia were studied. Thirteen eyes of 13 age-matched normal subjects were studied as controls. METHODS All of the patients underwent an advancement of a previously operated medial rectus muscle. Patients were divided into 3 groups based on the insertion of the medial rectus muscle: Normally recessed stretched scar, and slipped muscle. MAIN OUTCOME MEASURES A comparison was made of the clinical findings, intraoperative findings, and distance from the limbus to the medial rectus muscle measured on magnetic resonance images among the groups. RESULTS The medial rectus of 4 eyes of 3 patients had normally recessed insertions and 7 eyes had abnormal insertions (3 stretched scars, 4 slipped muscles). The clinical findings were not different among the 3 groups. The magnetic resonance images showed that the medial rectus muscle was located closest to the limbus in the control subjects and most distant in the patients with a slipped muscle (P<0.005). The clinical findings in the patients with a stretched scar and with normally recessed were indistinguishable. CONCLUSIONS Magnetic resonance images of the medial rectus muscles of the control subjects and operated groups are significantly different morphologically. A slipped medial rectus muscle has characteristic magnetic resonance findings that are distinguishable from the muscle with normally recessed and stretched scar.

Novel RDH5 Mutation in Family with Mother Having Fundus Albipunctatus and Three Children with Retinitis Pigmentosa

Purpose: To identify mutations in the RDH5 gene in a family with a mother having fundus albipunctatus (FA) and 3 children with retinitis pigmentosa (RP). Methods: Ophthalmological examinations were performed to diagnose FA and RP. Mutational analysis of RDH5 was performed. Results/Conclusions: The mother was diagnosed with FA, and 3 children were diagnosed with RP. The probands mother, brother, and sister had a novel mutation c.689_690CT > GG in RDH5. The proband and mother had a previously reported mutation c.928delCinsGAAG. Consequently, the mothers FA was caused by compound heterozygous mutations. Further studies will be needed to determine the gene responsible for childrens RP.