Optical coherence tomography in the diagnosis of juvenile X-linked retinoschisis

Retinoschisis: a retrospective study of an uncommon retinal change in cats and dogs

Retinoschisis is a poorly documented form of retinal degeneration characterized by cyst-like splitting that occurs between the inner nuclear and outer plexiform layers. The pathogenesis of retinoschisis is incompletely understood, but congenital, acquired and secondary aetiologies (glaucoma, inflammation, neoplasia) are described in humans. This retrospective study investigated the prevalence and associated histological and clinical features of retinoschisis in cats and dogs submitted for biopsy over a 10-year period. Of 140 samples with documented 'retinal vacuolation', four out of 120 (3%) canine samples and one out of 20 (5%) feline samples had changes consistent with retinoschisis. In most cases (80%), there was concurrent retinal detachment. In cases with available histories, increased intraocular pressure, proptosis and retinal detachment were reported clinical findings. In cats and dogs, retinoschisis is a retinal change that is generally secondary to other ocular lesions.

X-Linked Retinoschisis: Deep Phenotyping and Genetic Characterization

PURPOSE

To examine the genetic and clinical features in children and adults with X-linked retinoschisis (XLRS).

DESIGN

Single-center consecutive, retrospective, observational study.

PARTICIPANTS

Adults and children with molecularly confirmed XLRS followed up between 1999 and 2020.

METHODS

Analysis of genetic, clinical, and retinal imaging findings, including OCT and fundus autofluorescence (FAF), cross-sectionally and longitudinally, was performed.

MAIN OUTCOMES MEASURES

RS1, variants, type of variants and phenotype correlations, age of onset, complications rates and types, fundoscopy findings, OCT metrics, FAF patterns, correlations including between best corrected visual acuity (BCVA) and age, and OCT characteristics.

RESULTS

One hundred thirty-two male patients were identified harboring 66 retinoschisin 1 variants, with 7 being novel. The mean age at onset was 16.5 years (range, 0-58 years). Seventy-one patients (71/75 [94.7%]) were symptomatic at presentation; all had decreased best-corrected visual acuity (BCVA). Funduscopy findings were symmetric in 104 patients (104/108 [96.3%]), with the most common finding being macular schisis (82.4%), whereas peripheral retinoschisis was present in 38.9% and macular atrophy was present in 11.1%. Twenty patients (18.5%) demonstrated complications (vitreous hemorrhage, retinal detachment, or both). Mean BCVA was 0.65 logarithm of the minimum angle of resolution (logMAR; Snellen equivalent, 20/89) in the right eye and 0.64 logMAR (Snellen equivalent, 20/87) in the left eye. Mean BCVA change over a mean interval of 6.7 years was 0.04 and 0.01 logMAR for right and left eyes, respectively. A normal FAF pattern was identified in 16 of 106 eyes (15.1%); 45 eyes (42.5%) showed a spoke-wheel pattern, 13 eyes (12.3%) showed foveal hyperautofluorescence, and 18 eyes (17.0%) showed a central reduction in signal. In total, 14 patients demonstrated evidence of progression on FAF over time. On OCT, foveoschisis was observed in 172 eyes (172/215 [80%]), parafoveal schisis was observed in 171 eyes (171/215 [79.5%]), and foveal atrophy was observed in 44 eyes (44/215 [20.5%]). Cystoid changes were localized to the inner nuclear layer (172/181 eyes [95%]), the outer nuclear layer (97/181 [53.6%]), and the ganglion cell layer (92/181 [50.8%]). Null variants were associated with worse final BCVA and aforementioned complications.

CONCLUSIONS

X-linked retinoschisis is highly phenotypically variable, but with relative foveal and BCVA preservation until late adulthood, allowing more accurate prognostication. The slowly (often minimally) progressive disease course may pose a challenge in identification of early end points for therapeutic trials aimed at altering the kinetics of degeneration.

HANDHELD SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY FINDINGS OF X-LINKED RETINOSCHISIS IN EARLY CHILDHOOD

BACKGROUND/PURPOSE

Using handheld spectral domain optical coherence tomography (SDOCT) imaging to investigate in vivo microanatomic retinal changes and their progression over time in young children with juvenile X-linked retinoschisis (XLRS).

METHODS

This retrospective analysis was of handheld SD OCT images obtained under a prospective research protocol in children who had established XLRS diagnosis based on genetic testing or clinical history. Three OCT graders performed standardized qualitative and quantitative assessment of retinal volume scans, which were divided into foveal, parafoveal, and extrafoveal regions. Visual acuity data were obtained when possible.

RESULTS

Spectral domain OCT images were available of both eyes in 8 pediatric patients with ages 7 months to 10 years. The schisis cavities involved inner nuclear layer in over 90% (15/16) of eyes in all 3 regions. Retinal nerve fiber and ganglion cell layer involvement was present only in the extrafoveal region in 63% (10/16) eyes and outer nuclear and plexiform layer in few others. In 7 children followed over 2 months to 15 months, the location of schisis remained consistent. Central foveal thickness decreased from the baseline to final available visit in 4/6 eyes. Ellipsoid zone disruption seemed to accompany lower visual acuity in 1/4 eyes.

CONCLUSION

Early in life, the SD OCT findings in XLRS demonstrate differences in schisis location in fovea-parafoveal versus extrafoveal region, possible association between poor visual acuity and degree of ellipsoid zone disruption and decrease in central foveal thickness over time in this group. Furthermore, they illustrates that the pattern of XLRS in adults is already present in very young children, and unlike in older children and adults, those presenting with earlier disease may have a more aggressive course. Further studies in this early age group may provide more insights into treatment and prevention of progressive visual impairment in children with XLRS.

CAPILLARY NETWORK ALTERATIONS IN X-LINKED RETINOSCHISIS IMAGED ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To assess foveal and parafoveal vasculature at the superficial capillary plexus, deep capillary plexus, and choriocapillaris of patients with X-linked retinoschisis by means of optical coherence tomography angiography.

METHODS

Six patients with X-linked retinoschisis (12 eyes) and seven healthy controls (14 eyes) were recruited and underwent complete ophthalmologic examination, including best-corrected visual acuity, dilated fundoscopy, and 3 × 3-mm optical coherence tomography angiography macular scans (DRI OCT Triton; Topcon Corp). After segmentation and quality review, optical coherence tomography angiography slabs were imported into ImageJ 1.50 (NIH; Bethesda) and digitally binarized. Quantification of vessel density was performed after foveal avascular zone area measurement and exclusion. Patients were additionally divided into "responders" and "nonresponders" to dorzolamide therapy.

RESULTS

Foveal avascular zone area resulted markedly enlarged at the deep capillary plexus (P < 0.001), particularly in nonresponders. Moreover, patients disclosed a significant deep capillary plexus rarefaction, when compared with controls (P: 0.04); however, a subanalysis revealed that this damage was limited to the fovea (P: 0.006). Finally, the enlargement of foveal avascular zone area positively correlated with a decline in best-corrected visual acuity (P: 0.01).

CONCLUSION

Prominent foveal vascular impairment is detectable in the deep capillary plexus of patients with X-linked retinoschisis. Our results correlate with functional outcomes, suggesting a possible vascular role in X-linked retinoschisis clinical manifestations.

Analysis of Anatomic and Functional Measures in X-Linked Retinoschisis

Purpose

To examine the symmetry of structural and functional parameters between eyes in patients with X-linked retinoschisis (XLRS), as well as changes in visual acuity and electrophysiology over time.

Methods

This is a single-center observational study of 120 males with XLRS who were evaluated at the National Eye Institute. Examinations included best-corrected visual acuity for all participants, as well as ERG recording and optical coherence tomography (OCT) on a subset of participants. Statistical analyses were performed using nonparametric Spearman correlations and linear regression.

Results

Our analyses demonstrated a statistically significant correlation of structural and functional measures between the two eyes of XLRS patients for all parameters. OCT central macular thickness (n = 78; Spearman r = 0.83, P < 0.0001) and ERG b/a ratio (n = 78; Spearman r = 0.82, P < 0.0001) were the most strongly correlated between a participant's eyes, whereas visual acuity was less strongly correlated (n = 120; Spearman r = 0.47, P < 0.0001). Stability of visual acuity was observed with an average change of less than one letter (n = 74; OD −0.66 and OS −0.70 letters) in a mean follow-up time of 6.8 years. There was no statistically significant change in the ERG b/a ratio within eyes over time.

Conclusions

Although a broad spectrum of clinical phenotypes is observed across individuals with XLRS, our study demonstrates a significant correlation of structural and functional findings between the two eyes and stability of measures of acuity and ERG parameters over time. These results highlight the utility of the fellow eye as a useful reference for monocular interventional trials.

Repeatability, reproducibility and interocular difference in the assessments of optic nerve OCT in children- a Swedish population-based study

Background

The aim was, first, to collect normative data of the optic nerve head and the peripapillary retinal nerve fibre layer (RNFL) thickness assessed with Cirrus SD-OCT, in healthy children in a population-based study; second, using these data, to examine repeatability, reproducibility and the interocular difference.

Methods

One-hundred and ten eyes from 57 children aged 6–15 born at term, were examined. Best-corrected visual acuity and refraction were assessed. Both eyes were examined and the interocular difference was calculated. Repeatability was calculated by one examiner performing three assessments. Thereafter, a second examiner repeated the assessments to calculate reproducibility.

Results

Mean RNFL thickness was 99.2 (SD 8.8) μm, mean disc area 1.89 (SD 0.37) mm² and mean rim area 1.52 (SD 0.26) mm². No significant correlations with age, gender or refraction were found. Repeatability and reproducibility were good overall. There was interocular symmetry between the eyes.

Conclusions

Normal values for optic nerve head and RNFL thickness assessed with Cirrus SD-OCT were gathered to obtain a normal material in children. High repeatability and reproducibility indicated reliability of assessments performed by different examiners on different occasions. Overall, good correlation between right and left eyes was found.

Treatment of cystic cavities in X-linked juvenile retinoschisis: The first sequential cross-over treatment regimen with dorzolamide

Purpose

To report the first sequential cross-over treatment with the longest ophthalmic follow-up in a case of X-linked juvenile retinoschisis (XLRS) successfully treated with topical dorzolamide.

Observations

A healthy 34 year-old man presented with one month history of decreased visual acuity in his left eye. Funduscopy was significant for a blunted and cystoid-like foveal reflex in both eyes. The macular OCT showed cystic foveal changes OU. The patient was diagnosed with XLRS and was observed. On two subsequent follow-ups, a significant decrease in the patient's visual acuity warranted the use of topical dorzolamide for treating the cystic foveal changes, which completely resolved two months post-treatment initiation.

Conclusion and importance

Previous reports showed the benefit of dorzolamide in treating foveal cystic cavities in XLRS. To our knowledge, this is the first case of XLRS demonstrating the benefits of topical dorzolamide based on a sequential cross-over treatment regimen. It may also represent a case with the longest ophthalmic follow-up providing, in consequence, long-term understanding of the natural history and complications of this rare disease After ruling out major causes of cystoid macular edema, XLRS patients presenting with worsening of their visual acuities due to larger cystic macular changes may benefit from an alternating ON/OFF regimen of topical dorzolamide, which offers a significant treatment advantage outweighing its well-known side effects. Our study consolidates the importance of “medication vacation” by showing its efficacy in providing anatomical and visual functional improvements in patients with chronic cystic macular changes.

Structure/Psychophysical Relationships in X-Linked Retinoschisis

PURPOSE

To compare structural properties from spectral-domain optical coherence tomography (SDOCT) and psychophysical measures from a subset of patients enrolled in a larger multicenter natural history study of X-linked retinoschisis (XLRS).

METHODS

A subset of males (n = 24) participating in a larger natural history study of XLRS underwent high-resolution SDOCT. Total retina (TR) thickness and outer segment (OS) thickness were measured manually. Shape discrimination hyperacuity (SDH) and contour integration perimetry (CIP) were performed on an iPad with the myVisionTrack application. Sensitivity was measured with fundus-guided perimetry (4-2 threshold testing strategy; 10-2 grid, spot size 3, 68 points). Correlation was determined with Pearson's r correlation. Values are presented as the mean ± SD.

RESULTS

Mean macular OS thickness was less in XLRS patients (17.2 ± 8.1 μm) than in controls (37.1 ± 5.7 μm; P < 0.0001) but mean TR thickness was comparable (P = 0.5884). For patients, total sensitivity was lower (13.2 ± 6.6 dB) than for controls (24.2 ± 2.4 dB; P = 0.0008) and had a strong correlation with photoreceptor OS (R(2) = 0.55, P = 0.0001) and a weak correlation with TR thickness (R(2) = 0.22, P = 0.0158). The XLRS subjects had a logMAR best corrected visual acuity (BCVA) of 0.5 ± 0.3 that was associated with OS (R(2) = 0.79, P < 0.0001) but not TR thickness (R(2) = 0.01, P = 0.6166). Shape DH and CIP inner ring correlated with OS (R(2) = 0.33, P = 0.0085 and R(2) = 0.47, P = 0.0001, respectively) but not TR thickness (R(2) = 0.0004, P = 0.93; R(2) = 0.0043, P = 0.75, respectively).

CONCLUSIONS

When considered from a single visit, OS thickness within the macula is more closely associated with macular function than TR thickness within the macula in patients with XLRS.

Macular thickness assessed with spectral domain OCT in a population-based study of children: normative data, repeatability and reproducibility and comparison with time domain OCT

PURPOSE

To collect data on macular thickness assessed with Cirrus OCT in healthy children in a population-based study, to examine the repeatability and reproducibility, and to compare the values with Stratus OCT.

METHODS

Fifty-eight 6- to 15-year-old children, born at term, were examined. Best-corrected visual acuity and refraction were assessed. One examiner performed three OCT assessments, and the repeatability was calculated. Thereafter, a second examiner repeated the examinations to calculate the reproducibility. One eye was randomized to be included in the normal material. Finally, the second examiner assessed the macular thickness with the Stratus OCT.

RESULTS

The mean value (±SD) of central macular thickness was 255 ± 17 μm, and the total macular volume was 10.3 ± 0.5 mm(3) . No correlations were found between macular thickness and age, gender or refraction. The coefficients of variance (CoVs) for both repeatability and reproducibility were <1.21%, and the intraclass correlations (ICCs) were over 0.86. The Cirrus OCT showed a 29% thicker central macular thickness than the Stratus OCT.

CONCLUSION

Normal values for macular thickness assessed with Cirrus OCT in healthy full-term children in a population-based study were reported. The assessments showed high repeatability and reproducibility. The values of Cirrus and Stratus OCT differed and the techniques were not interchangeable.

The gene mutation in a Taiwanese family with X-linked retinoschisis

X-linked retinoschisis (XLRS) is one of the leading causes of macular degeneration in male children. The purpose of this study is to describe the clinical characteristics of a Taiwanese family with X-linked retinoschisis (XLRS) and to investigate the genetic mutation in the retinoschisin 1 (RS1) gene. A total of four participants in this XLRS family were analyzed. Complete ophthalmic examinations were performed, including best corrected visual acuity, optical coherence tomography (OCT), and electroretinogram (ERG). Direct DNA sequence of the RS1 gene identified one affected male and one female carrier. The affected male, had a cartwheel-like macular appearance and abnormal retinal pigment epithelium pigmentation in his bilateral eyes. The mixed scotopic ERG b-wave was more reduced than a-wave. OCT revealed typical macular microcystic schisis cavities. Direct DNA sequence analysis revealed a single base pair substitution in Exon 4, 304C > T, resulting in Arg102Trp. Our results show a RS1 (304C > T) mutation in a Taiwanese family with XLRS. This finding expands the clinical profiles of RS1 mutation and may help to further understand its pathogenesis.

Peripapillary retinoschisis in glaucomatous eyes

Purpose

To investigate the structural and clinical characteristics of peripapillary retinoschisis observed in glaucomatous eyes using spectral-domain optical coherence tomography (SD-OCT).

Methods

Circumpapillary retinal nerve fiber layer (cpRNFL) and macular cross-hair SD-OCT scans and infrared fundus images of the glaucoma patients from the Investigating Glaucoma Progression Study (IGPS) and healthy volunteers were reviewed. Optic disc images obtained using enhanced depth imaging (EDI) SD-OCT were also evaluated. The structural characteristics and clinical course of the retinoschisis associated with glaucoma were investigated.

Results

Twenty-five retinoschisis areas were found in 22 of the 372 patients (5.9%) included in the IGPS, and in 1 area in 1 of 187 healthy control subjects (0.5%). In the 22 glaucomatous eyes with retinoschisis, the schisis was attached to the optic disc and overlapped with the retinal nerve fiber layer (RNFL) defect. The RNFL was the layer most commonly affected by the retinoschisis, either alone or together with other deeper layers. Acquired optic disc pit was identified in 8 eyes on disc photography and/or B-scan images obtained by EDI SD-OCT. Spontaneous resolution of this condition was observed in nine eyes. No retinal detachment or macular involvement of the retinoschisis was observed in any of the eyes. Multivariate analysis showed a significant influence of a higher intraocular pressure at SD-OCT scanning on the presence of retinoschisis (Odds ratio  = 1.418, P = 0.001).

Conclusions

The present study investigated 22 cases of peripapillary retinoschisis in glaucomatous eyes. The retinoschisis was attached to the optic nerve and topographically correlated with RNFL defect. It often resolved spontaneously without causing severe visual disturbance. Care should be taken not to overestimate the RNFL thickness in eyes with retinoschisis, and also not to misinterpret the resolution of retinoschisis as a rapid glaucomatous RNFL deterioration.

Interocular symmetry in retinal and optic nerve parameters in children as measured by spectral domain optical coherence tomography

BACKGROUND/AIMS

To report interocular differences in retinal nerve fibre layer (RNFL), optic nerve head and macular parameters in children using spectral domain optical coherence tomography (SD-OCT).

METHODS

This was an observational cross-sectional study including 108 healthy children aged 6-17 years with no ocular abnormality except refractive error. After a comprehensive eye exam and axial length measurement, RNFL, optic nerve and macular thickness measurements were performed using the Cirrus OCT machine. Right and left eyes were compared and interocular differences were computed. Subjects were also divided into two groups based on age (under or over 10 years of age). Main outcome measures were interocular differences and their correlations with age and gender.

RESULTS

The study included 108 children, mean age 10.7 ± 3.1 years; significant interocular differences were observed in both macular and RNFL parameters. The macular thickness analysis revealed interocular differences in the outer nasal and outer inferior quadrants, with left eyes displaying larger values. With respect to RNFL parameters, right eyes displayed thicker nasal and temporal quadrants, and inferior clock hours; left eyes had a thicker superior quadrant. The older age group (>10 years) had more pronounced variation in interocular differences compared with the younger group with less mature visual systems.

CONCLUSIONS

Normal variation in interocular symmetry exists. Our results can contribute to establishing a standard reference for interocular differences in OCT parameters in children aged 6-17 years using the Cirrus device.

Is quantitative spectral-domain superior to time-domain optical coherence tomography (OCT) in eyes with age-related macular degeneration?

PURPOSE

The aim of this study was to determine the variability of macular map measurements, for two generations of optical coherence tomography (OCT) instruments, in eyes with wet age related macular degeneration (AMD) and low visual acuity.

METHODS

Patients were examined with Stratus OCT and Cirrus HD-OCT. The macular thickness was assessed with the 'macular thickness map scan' and 'fast protocol' in Stratus and with the 512 × 128 and 200 × 200 cube protocols in Cirrus OCT. Two measurements were taken one directly after the other, at the first visit to analyse repeatability. Approximately 1 week later, a third measurement was taken to analyse reproducibility. In Cirrus OCT, a manual correction of foveal location was also performed. Repeatability and reproducibility were calculated as a coefficient of variance (CoV) and a coefficient of repeatability/reproducibility.

RESULTS

 Repeatability for central macular thickness (expressed as CoV) was about three per cent for all protocols, and the coefficient of repeatability between 34 and 54 μm. Reproducibility (also expressed as CoV) was between four to seven per cent and coefficient of repeatability between 64 and 89 μm. After manual adjustment of foveal location in Cirrus OCT, the coefficient of repeatability improved to 12-18 μm, and the coefficient of reproducibility to 44-47 μm.

CONCLUSIONS

  In eyes affected by wet AMD, there were small differences in repeatability and reproducibility when comparing quantitative maps in Stratus and Cirrus OCT. However, when the software for manual correction of foveal position in Cirrus OCT was used, the variability decreased markedly, and the repeatability was close to what had been reported in normal eyes, demonstrating a significant, potential advantage of spectral-domain over time-domain OCT.

Two cases of X-linked retinoschisis with different spectral domain optical coherence tomography findings

Spectral domain optical coherence tomography was used to image the maculae of two brothers who had the diagnosis of X-linked retinoschisis maculopathy. One patient demonstrated a large foveal cyst in one eye and a lamellar macular hole in the fellow eye. The second patient demonstrated small retinal cysts in multiple layers of the retina. Spectral domain optical coherence tomography allowed high-resolution imaging and characterization of the features in X-linked retinoschisis in these patients, and it highlighted the variability of the same genetic disease, even in one family.

Wide-field spectral-domain optical coherence tomography in patients and carriers of X-linked retinoschisis

PURPOSE

To evaluate macular and extramacular retinal anatomy in patients and carriers of X-linked retinoschisis (XLRS) using a wide-field spectral-domain optical coherence tomography (SD-OCT) imaging technique.

DESIGN

Case series.

PARTICIPANTS

Six XLRS-affected male subjects and 3 XLRS female carriers.

METHODS

The subjects prospectively underwent XLRS DNA genotyping and comprehensive ophthalmic examination, including visual acuity, 30-2 Humphrey visual field, fundus photography, and wide-field SD-OCT, a montage technique to generate SD-OCT images spanning approximately 50 degrees horizontally and 35 degrees vertically of the posterior pole.

MAIN OUTCOME MEASURES

Distribution and location of schisis cavities.

RESULTS

Among male subjects affected by XLRS, asymmetric bilateral schisis was seen in all eyes imaged with montage SD-OCT (11 eyes). Wide-field OCT images demonstrated schisis cavities only in the central macula in 6 eyes (55%), throughout the macula extending to the outside of the temporal arcades in 3 eyes (27%), and throughout the macula extending nasal to the optic nerve in 2 eyes (18%). Cystoid spaces accounting for macular splitting were present in the inner nuclear layer (INL) in all 11 eyes and in the outer nuclear layer (ONL) in 4 eyes. A few small cysts were seen parafoveally in the ganglion cell layer (GCL) or nerve fiber layer (NFL) in 4 eyes. Subclinical extramacular schisis spaces were seen (n=5 eyes) within the INL in 1 eye, the ONL in 1 eye, the INL/GCL/NFL in 1 eye, the ONL/GCL/NFL in 1 eye, and the INL/ONL/GCL/NFL in 1 eye. Schisis was rarely seen nasal to the optic nerve (2 eyes). Central/paracentral visual field defects were seen in 9 eyes. Female carriers did not show schisis on examination or OCT.

CONCLUSIONS

Wide-field SD-OCT is a useful tool for evaluating complex retinal anatomy. In patients with XLRS, the foveomacular schisis was seen most frequently in the INL. Subclinical extramacular schisis was seen in 45% of eyes and was equally prevalent in the INL, ONL, and GCL/FNL. The GCL/FNL cystoid spaces were small and seen near the fovea and the arcades only. Carriers were schisis-free.

FINANCIAL DISCLOSURE(S)

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

X-linked juvenile retinoschisis: clinical diagnosis, genetic analysis, and molecular mechanisms

X-linked juvenile retinoschisis (XLRS, MIM 312700) is a common early onset macular degeneration in males characterized by mild to severe loss in visual acuity, splitting of retinal layers, and a reduction in the b-wave of the electroretinogram (ERG). The RS1 gene (MIM 300839) associated with the disease encodes retinoschisin, a 224 amino acid protein containing a discoidin domain as the major structural unit, an N-terminal cleavable signal sequence, and regions responsible for subunit oligomerization. Retinoschisin is secreted from retinal cells as a disulphide-linked homo-octameric complex which binds to the surface of photoreceptors and bipolar cells to help maintain the integrity of the retina. Over 190 disease-causing mutations in the RS1 gene are known with most mutations occurring as non-synonymous changes in the discoidin domain. Cell expression studies have shown that disease-associated missense mutations in the discoidin domain cause severe protein misfolding and retention in the endoplasmic reticulum, mutations in the signal sequence result in aberrant protein synthesis, and mutations in regions flanking the discoidin domain cause defective disulphide-linked subunit assembly, all of which produce a non-functional protein. Knockout mice deficient in retinoschisin have been generated and shown to display most of the characteristic features found in XLRS patients. Recombinant adeno-associated virus (rAAV) mediated delivery of the normal RS1 gene to the retina of young knockout mice result in long-term retinoschisin expression and rescue of retinal structure and function providing a 'proof of concept' that gene therapy may be an effective treatment for XLRS.

Abnormal cone structure in foveal schisis cavities in X-linked retinoschisis from mutations in exon 6 of the RS1 gene

PURPOSE

To evaluate macular cone structure in patients with X-linked retinoschisis (XLRS) caused by mutations in exon 6 of the RS1 gene.

METHODS

High-resolution macular images were obtained with adaptive optics scanning laser ophthalmoscopy (AOSLO) and spectral domain optical coherence tomography (SD-OCT) in two patients with XLRS and 27 age-similar healthy subjects. Retinal structure was correlated with best-corrected visual acuity, kinetic and static perimetry, fundus-guided microperimetry, full-field electroretinography (ERG), and multifocal ERG. The six coding exons and the flanking intronic regions of the RS1 gene were sequenced in each patient.

RESULTS

Two unrelated males, ages 14 and 29, with visual acuity ranging from 20/32 to 20/63, had macular schisis with small relative central scotomas in each eye. The mixed scotopic ERG b-wave was reduced more than the a-wave. SD-OCT showed schisis cavities in the outer and inner nuclear and plexiform layers. Cone spacing was increased within the largest foveal schisis cavities but was normal elsewhere. In each patient, a mutation in exon 6 of the RS1 gene was identified and was predicted to change the amino acid sequence in the discoidin domain of the retinoschisin protein.

CONCLUSIONS

AOSLO images of two patients with molecularly characterized XLRS revealed increased cone spacing and abnormal packing in the macula of each patient, but cone coverage and function were near normal outside the central foveal schisis cavities. Although cone density is reduced, the preservation of wave-guiding cones at the fovea and eccentric macular regions has prognostic and therapeutic implications for XLRS patients with foveal schisis. (Clinical Trials.gov number, NCT00254605.).

Retinal nerve fibre layer thickness in full-term children assessed with Heidelberg retinal tomography and optical coherence tomography: normal values and interocular asymmetry

PURPOSE

This study aimed to investigate normal values and interocular differences in retinal nerve fibre layer (RNFL) thickness, using optical coherence tomography (OCT) and Heidelberg retinal tomography (HRT), in 5-16-year-old children born at full-term with normal birthweights.

METHODS

Fifty-six children with normal visual acuity and refraction were examined with Stratus OCT and HRT. Three examinations were performed in each eye. One eye in each child was randomized for analyses of normal values. Findings in 54 eyes were evaluated. Mean values of RNFL thickness were calculated. Coefficients of variance and intraclass correlations were calculated. The correlation between right and left eyes and the limits of difference were determined for both methods.

RESULTS

Mean RNFL thickness was 98.4 μm (standard deviation [SD] 7.88 μm) assessed with OCT and 213.0 μm (SD 54.0 μm) assessed with HRT. No correlations between age or gender and RNFL thickness were found. The coefficients of variance were 2.9% and 5.6% for OCT and HRT, respectively, and intraclass correlations were 0.85 and 0.88, respectively. The limits of difference between the two eyes ranged from -9 μm to 9 μm with OCT and from -109 μm to 87 μm with HRT.

CONCLUSIONS

Both OCT and HRT can be used in children aged 5-16 years, but OCT provides less variability in determinations of RNFL thickness, both in repeated examinations of the same eye and in comparisons between the two eyes. The present study provides values for normal RNFL thickness in healthy children which can be used to make comparisons with values in children with optic nerve diseases.

Molecular mechanisms leading to null-protein product from retinoschisin (RS1) signal-sequence mutants in X-linked retinoschisis (XLRS) disease

Retinoschisin (RS1) is a cell-surface adhesion molecule expressed by photoreceptor and bipolar cells of the retina. The 24-kDa protein encodes two conserved sequence motifs: the initial signal sequence targets the protein for secretion while the larger discoidin domain is implicated in cell adhesion. RS1 helps to maintain the structural organization of the retinal cell layers and promotes visual signal transduction. RS1 gene mutations cause X-linked retinoschisis disease (XLRS) in males, characterized by early-onset central vision loss. We analyzed the biochemical consequences of several RS1 signal-sequence mutants (c.1A>T, c.35T>A, c.38T>C, and c.52G>A) found in our subjects. Expression analysis in COS-7 cells demonstrates that these mutations affect RS1 biosynthesis and result in an RS1 null phenotype by several different mechanisms. By comparison, discoidin-domain mutations generally lead to nonfunctional conformational variants that remain trapped inside the cell. XLRS disease has a broad heterogeneity in general, but subjects with the RS1 null-protein signal-sequence mutations are on the more severe end of the clinical phenotype. Results from the signal-sequence mutants are discussed in the context of the discoidin-domain mutations, clinical phenotypes, genotype-phenotype correlations, and implications for RS1 gene replacement therapy.

Optical coherence tomography is helpful in the diagnosis of foveal hypoplasia

PURPOSE

To investigate whether optical coherence tomography (OCT) is helpful in the diagnosis of foveal hypoplasia in children.

METHODS

Children with albinism and aniridia were examined with Stratus OCT 3 software 4.0.1 (Carl Zeiss Meditec, Dublin, California, USA). A qualitative examination of the macular area was performed with a 128 A-scans/second-single-scan. Macular thickness was measured quantitatively with an automatic fast macular map protocol. The average thickness/volume of the macula was presented as numerical values and as a false colour code in nine modified early treatment of diabetic retinopathy study (ETDRS) areas (A1-A9). A previously collected control group of children was used for comparison.

RESULTS

Macular thickness in 13 children with albinism and three children with aniridia was measured with OCT. Comparison with healthy children in the same population was performed. Patients with albinism and aniridia had significantly thicker central macula (A1) and foveola than children in the control group.

CONCLUSION

OCT was found to be useful in the diagnosis of foveal hypoplasia in children.

Foveomacular schisis in juvenile X-linked retinoschisis: an optical coherence tomography study

PURPOSE

To explore the structural features of juvenile X-linked retinoschisis using spectral-domain optical coherence tomography (OCT).

DESIGN

Retrospective, observational cross-sectional study.

METHODS

Eighteen male patients (34 eyes) who were diagnosed with juvenile X-linked retinoschisis at the Eye & ENT Hospital of Fudan University over an 18-month period were included. Their OCT images, which were obtained using spectral-domain OCT (Cirrus HD-OCT; Carl Zeiss Meditec), were analyzed. The anatomic location of the schisis cavity in juvenile X-linked retinoschisis was characterized by direct inspection of OCT images.

RESULTS

On OCT, the schisis cavity was visible at the fovea in all 34 eyes, and it was associated with increased retinal thickness. Schisis was present at the retinal nerve fiber layer in 4 eyes, at the inner nuclear layer in 29 eyes, and at the outer nuclear layer/outer plexiform layer in 22 eyes. In most cases, widespread foveomacular schisis was detected using OCT; however, in 9 eyes (6 patients), the schisis was confined to the fovea. Schisis of the inner nuclear layer and outer nuclear layer/outer plexiform layer almost always involved the foveal center, but retinal nerve fiber layer schisis was seen only in the parafoveal area.

CONCLUSIONS

Despite conventional wisdom, in patients with X-linked retinoschisis, the schisis cavity can occur in a number of different layers of the neurosensory retina (retinal nerve fiber layer, inner nuclear layer, and outer nuclear layer/outer plexiform layer). In addition, different forms of schisis may affect different locations in the macula (foveal vs parafoveal), and, in most eyes, the schisis involves the entire foveomacular region.

Diagnosis and pathogenesis of congenital X-linked retinoschisis with optical coherence tomography

This study shows how optical coherence tomography has been valuable in the diagnosis of congenital X-linked retinoschisis. An infant with convergent strabismus underwent serial optical coherence tomography examinations that helped to make the diagnosis of congenital X-linked retinoschisis. Optical coherence tomography is useful in the diagnosis of congenital X-linked retinoschisis and adds new information about pathogenesis. The authors recommend the use of optical coherence tomography in pediatric retinal disease, even if the macula appears normal on indirect ophthalmoscopy.

A population-based study of macular thickness in full-term children assessed with Stratus OCT: normative data and repeatability

PURPOSE

 We aimed to determine normal macular thickness values, assessed with optical coherence tomography (OCT), in a population of full-term children of normal birthweight.

METHODS

 A total of 56 children, aged 5-16 years, randomly chosen from the population register, were examined with Stratus OCT. Only children with visual acuity < 0.2 logMAR, spherical equivalent of - 3 to + 3 D and astigmatism < 2 D were included. The fast macular map protocol was used and three examinations were performed in each eye. One eye was then randomized for further analyses. Mean values for the nine ETDRS areas, foveal minimum thickness and macular volume were calculated for 55 eyes. Coefficients of variance and intraclass correlations were calculated for each area.

RESULTS

All children co-operated well and no child was excluded for lack of concentration. Mean ± standard deviation central macular thickness was 204 ± 19 μm. Mean total macular volume was 7.11 ± 0.35 mm(3). No correlations were found between age, gender and macular thickness. Coefficients of variance were < 2% and intraclass correlations were > 0.9 in all areas, except the foveal minimum.

CONCLUSIONS

Normal values for macular thickness in healthy full-term children were reported. As the Stratus OCT provides normal values only for adults, these data are a better alternative for comparison with children with retinal abnormalities. We concluded that OCT is suitable for examining the retina in children aged 5-16 years and has the same high level of repeatability as in adults.

[Macular edema without fluorescein leakeage]

PURPOSE

To study the OCT (optical coherence tomography) features of cases of unexplained macular edema, which were not combined with fluorescein leakage on angiography.

PATIENTS AND METHOD

We report a retrospective series of three patients who presented with visual acuity impairment due to unilateral macular thickening visible on OCT examination. All eyes studied underwent OCT and angiography and electrophysiological examinations. None of the patients had a medical record and none of the eyes studied was highly myopic.

RESULTS

OCT profiles shared characteristics of myopic foveoschisis or X-linked retinoschisis. No fluorescein leakage was detected on angiography. The electrooculogram was impaired in one eye while other electrophysiological investigations were normal in all eyes.

DISCUSSION

Most frequently, macular edemas are associated with a fluorescein leakage on angiography. Macular edemas without angiographic leakage may correspond to unilateral idiopathic retinoschisis or macular edemas, with an atypical mechanism of intraretinal fluid accumulation.

Genetic and clinical evaluation of juvenile retinoschisis

Juvenile retinoschisis is a rare retinal dystrophy caused by RS1 gene mutations.(1) Clinical examinations and molecular testing definitively diagnosed juvenile retinoschisis in 2 male infants, one of whom had a novel mutation not previously reported in the United States. Genetic testing may be the simplest way to confirm this diagnosis in infants.

Spectral-domain OCT and microperimeter characterization of morphological and functional changes in X-linked retinoschisis

A case of X-linked retinoschisis with anatomic and functional issues correlated by a constellation of methods, including spectral-domain optical coherence tomography, microperimeter, electroretinography, and multifocal electroretinography, is described. This case highlights the importance of microperimetry in the presence of normal or subtle abnormalities in full-field electroretinography. The ability of spectral-domain optical coherence tomography in diagnosis and follow-up in cases with X-linked retinoschisis is demonstrated.

Retinal morphological changes of patients with X-linked retinoschisis evaluated by Fourier-domain optical coherence tomography

OBJECTIVE

To investigate the retinal microstructure and lamination of patients affected with X-linked retinoschisis (XLRS) using high-resolution imaging modalities.

METHODS

Patients diagnosed as having XLRS underwent assessment. Visual function testing included visual acuity, color vision, and full-field electroretinography. We used a high-resolution Fourier-domain optical coherence tomography (FD-OCT) system (4.5-mum axial resolution; 9 frames/s; 1000 A-scans per frame) combined with a handheld scanner. Macular image evaluation included schisis localization and retinal layer integrity.

RESULTS

Six patients with XLRS and identified mutations in the XLRS1 gene underwent testing. Visual acuity ranged from 0.2 to 1.6 logMAR (logarithm of the minimum angle of resolution). Results of FD-OCT revealed foveal schisis extending from the outer to the inner plexiform layer in 4 of 6 patients. Bullous foveal schisis was associated with younger age. All patients showed extrafoveal schisis within the outer and inner nuclear and ganglion cell layer, alone or in combination. Photoreceptor outer and inner segment layers were disrupted and irregular in all patients.

CONCLUSIONS

Retinal dystrophy in XLRS is reflected by morphological changes within the inner and outer retinal layers. Disturbed foveal photoreceptor integrity was identified in all patients. Retinal layer abnormalities correlated with age but did not appear to correlate with visual acuity or genotypic variation.

Macular and extramacular optical coherence tomography findings in X-linked retinoschisis

Two brothers with X-linked retinoschisis were evaluated using optical coherence tomography. Macular cleavage was observed at the inner nuclear layer. Retinal nerve fiber layer loss or detachment was observed outside the macular area, even in areas of clinically normal retina. Macular thickening and cavitation with multiple septa was characteristic, decreasing rapidly from the center toward the macular periphery and being more pronounced in the younger patient. No abnormal vitreomacular relationship or traction over the macular and extramacular schisis areas was observed. Optical coherence tomography showed a characteristic pattern of macular schisis in X-linked retinoschisis and confirmed a widespread retinal splitting despite mild clinical findings. Middle and outer neurosensory retina was principally compromised in the macular area and the retinal nerve fiber layer in extramacular areas. No vitreous traction was apparently involved in the foveal and extramacular splitting and elevation.

Unusual manifestations of x-linked retinoschisis: clinical profile and diagnostic evaluation

PURPOSE

To describe the unusual clinical manifestations and diagnostic evaluation of X-linked retinoschisis (XLR).

DESIGN

Prospective, observational case series.

METHODS

Eight patients with subnormal vision seeking treatment at a tertiary eye care center were evaluated clinically by optical coherence tomography (OCT) and electroretinography (ERG) in this prospective, noncomparative case series. Mutational screening was performed for the retinoschisin gene (RS1) by direct deoxyribonucleic acid (DNA) sequencing. The primary outcome measures were the clinical fundus findings and genetic results.

RESULTS

The mean patient age was 16.4 years (range, two to 33 years). Family history was positive in seven patients. Four demonstrated atypical fundus findings of XLR bilaterally. Atypical features included macular dragging and distortion (seven eyes, five patients), macular pigmentary changes or scarring (five eyes; three patients), and bilateral exudative detachments (one patient). One patient had macular dragging and pigmentary changes bilaterally. ERG aided diagnosis in five patients: selective B-wave suppression was observed in all. OCT demonstrated typical retinal schitic cavities universally, including the eyes with macular dragging and scarring. Genetic studies confirmed the clinical diagnosis in all patients; two revealed novel mutations.

CONCLUSIONS

We identified unusual presentations of XLR with the help of ERG, OCT, family screening, and genetic analysis; OCT seems to be a consistent diagnostic aid across the clinical spectrum of XLR.

X-linked retinoschisis: an update

X-linked retinoschisis is the leading cause of macular degeneration in males and leads to splitting within the inner retinal layers leading to visual deterioration. Many missense and protein truncating mutations have now been identified in the causative retinoschisis gene (RS1) which encodes a 224 amino acid secretory retinal protein, retinoschisin. Retinoschisin octamerisation is implicated in cell-cell interactions and cell adhesion perhaps by interacting with beta2 laminin. Mutations cause loss of retinoschisin function by one of the three mechanisms: by interfering with protein secretion, by preventing its octamerisation or by reducing function in the secreted octamerised protein. The development of retinoschisis mouse models have provided a model system that closely resembles the human disease. Recent reports of RS1 gene transfer to these models and the sustained restoration of some retinal function and morphology suggest gene replacement may be a possible future therapy for patients.

Juvenile X-linked retinoschisis with normal scotopic b-wave in the electroretinogram at an early stage of the disease

PURPOSE

To report four cases of genetically verified juvenile X-linked retinoschisis (XLRS) with normal scotopic b-waves in full-field ERG, including one patient with a novel mutation (W50X) in the RS1 gene.

METHODS

Four XLRS patients from different families were examined with regard to visual acuity, kinetic perimetry, fundus photography, full-field ERG, and OCT. Two of these patients were also examined with multifocal-ERG (mfERG). Mutations in the RS1 gene were identified by sequence analysis.

RESULTS

The full-field ERG presented normal b-wave amplitudes on scotopic white-light stimulation. OCT and mfERG presented macular schisis and macular dysfunction. Genetic analysis revealed a deletion of exon 1 and the promotor region in one patient and mutations giving rise to the amino acid substitutions R209C and W96R in two others. The fourth patient carried a novel mutation in exon 3 of the RS1 gene (nt 149 G-->A), causing the introduction of a stop codon after amino acid 49 in the RS protein.

CONCLUSION

Four young males with XLRS did not present with reduction in the scotopic b-wave amplitude on full-field ERG, which is otherwise often considered to be characteristic of the disease. Full-field ERG and molecular genetic analysis of the RS1 gene still remain the most important diagnostic tools for this retinal disorder, although the OCT can be a valuable complement in order to make the diagnosis at an early stage.

Fundus autofluorescence in children and teenagers with hereditary retinal diseases

INTRODUCTION

In adults, evaluation of fundus autofluorescence (AF) plays an important role in the differential diagnosis of retinal diseases. The aim of this study was to evaluate the feasibility of recording AF in children and teenagers and to define typical AF findings of various hereditary retinal diseases during childhood.

METHODS

Fifty patients aged 2 to 16 years with hereditary retinal diseases were analysed using the HRA (Heidelberg Retina Angiograph). To enhance the AF signal, a mean of up to 16 single images was calculated. Twenty healthy children (aged 4-16 years) served as controls.

RESULTS

In many children as young as 5 years of age and even in one 2-year-old child good AF images could be obtained. To achieve high quality images, larger image series (about 50 single images) were taken and appropriate single images were chosen manually to calculate the mean. Characteristically, Stargardt disease shows a central oval area of reduced AF, often surrounded by more irregular AF. In patients with Best disease, a central round structure with regular or irregular intense AF is visualised. Some patients with X-linked retinoschisis show central radial structures. In many patients with rod-cone dystrophies, a central oval ring-shaped area of increased AF is present. In early-onset severe retinal dystrophy (EOSRD) with RPE65 mutations AF is completely absent, whereas in other forms of Leber congenital amaurosis, AF is normal.

DISCUSSION

Fundus autofluorescence may visualise disease-specific distributions of lipofuscin in the retinal pigment epithelium, often not (yet) visible on ophthalmoscopy. AF images can be used in children to differentiate hereditary retinal diseases and to facilitate follow-up controls. In many cases, four single images are sufficient to analyse the AF pattern.