Novel Phenotypic and Genotypic Findings in X-LinkedRetinoschisis

Stephen H. Tsang, MD, PhD, Veronika Vaclavik, MD, Alan C. Bird, MD, Anthony G. Robson,PhD, and Graham E. Holder, PhDDepartments of Clinical Ophthalmology (Drs Tsang, Vaclavik, and Bird) and Electrophysiology (DrsRobson and Holder), Moorfields Eye Hospital, and Institute of Ophthalmology (Drs Vaclavik andBird), London, England. Dr Tsang is now with Brown Glaucoma Laboratory, Department ofOphthalmology and Department of Pathology and Cell Biology, College of Physicians andSurgeons, Columbia University, New York, NY

AbstractObjective—To describe atypical phenotypes associated with the retinoschisis (X-linked, juvenile)1 mutation (RS1).

Methods—Seven patients with multiple fine white dots at the macula and reduced visual acuitywere evaluated. Six patients underwent pattern and full-field electroretinography (ERG). On-offERG, optical coherence tomography, and fundus autofluorescence imaging were performed in somepatients. Mutational screening of RS1 was prompted by the ERG findings.

Results—Fine white dots resembling drusenlike deposits and sometimes associated with retinalpigment epithelial abnormalities were present in the maculae. An electronegative bright-flash ERGconfiguration was present in all patients tested, and abnormal pattern ERG findings confirmedmacular dysfunction. A parafoveal ring of high-density autofluorescence was present in 3 eyes; 1patient showed high-density foci concordant with the white dots. Optical coherence tomography didnot show foveal schisis in 3 of 4 eyes. All patients carried mutations in RS1, including 1 with a novel206T→C mutation in exon 4.

Conclusions—Multiple fine white dots at the macula may be the initial fundus feature in RS1mutation. Electrophysiologic findings suggest dysfunction after phototransduction and enablefocused mutational screening. Autofluorescence imaging results suggest early retinal pigmentepithelium involvement; a parafoveal ring of high-density autofluorescence has not previously beendescribed in this disorder.

X-linked retinoschisis (XLRS) is a common cause of macular dysfunction in young men,1,2with an incidence of 1 in 5000 to 1 in 25 000.3 Individuals with XLRS are typically firstidentified as school-aged boys who fail vision screening examinations (60%), have strabismus(30%), or have vitreous hemorrhage.1,2,4 Initially, the characteristic “spoke-wheel” appearancemay be seen at the fovea, caused by cystic changes,3 but this is commonly replaced withnonspecific macular atrophy in middle age.5 There is allelic heterogeneity at the retinoschisis(X-linked, juvenile) 1 locus (RS1), with different mutations causing a wide spectrum ofphenotypes.

Correspondence: Anthony G. Robson, PhD, Electrophysiology, Moorfields Eye Hospital, 162 City Rd, London EC1V 2PD, England(anthony.robson@moorfields.nhs.uk).Financial Disclosure: None reported.

NIH Public AccessAuthor ManuscriptArch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

Published in final edited form as:Arch Ophthalmol. 2007 February ; 125(2): 259–267. doi:10.1001/archopht.125.2.259.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

The gene mutated in XLRS, RS1, has 6 exons that encode the 224–amino acid proteinretinoschisin, which is processed by means of N-terminal cleavage of a 23–amino acidhydrophobic leader sequence into a mature protein of 201 amino acid residues (23 kDa) andis assembled into a disulfide-linked octamer.6 In many cases, this mutant protein cannot foldproperly and is retained intracellularly.4 The predicted protein sequence contains a highlyconserved discoidin domain, which is implicated in cell-cell adhesion and phospholipidbinding. This function is consistent with the observed splitting of the fiber layer of Henle inthe retina of patients with XLRS,7,8 suggesting that retinoschisin is essential during retinaldevelopment.9 The electronegative electroretinographic (ERG) configuration that is typicallyseen in patients with XLRS describes a waveform with a b-wave smaller than the a-wave andsuggests that the primary functional defect occurs after phototransduction or is inner retinal.

This study describes 7 patients with genetically confirmed mutations in RS1 that manifestatypical signs in the form of multiple white spots at the macula. The genotype and functional(ERG) phenotype are described.

MethodsThe tenets of the Declaration of Helsinki were followed. Seven individuals with reduced visualacuity and macular white dots were ascertained. Electroretinography, performed in 6 patients,suggested the possibility of XLRS and the need for genetic screening. In the remaining patient,screening was prompted by the presence of typical foveal lesions in an affected nephew.Findings from fundus photographs, fundus autofluorescence, and optical coherencetomography (OCT) were reviewed. Autofluorescence images were obtained by illuminatingthe fundus with argon laser light (488 nm) and viewing the resultant fluorescence through abandpass filter with a short wavelength cut off at 495 nm.10,11

Full-field ERGs were performed using extended testing protocols incorporating theInternational Society for Clinical Electrophysiology of Vision (ISCEV) standard12 to assessgeneralized retinal function. A stimulus 0.6 log unit greater than the ISCEV standard flash wasalso used, better to demonstrate the a-wave, as suggested in the recent revision of the ISCEVstandard for ERG.12 Long-duration on-off ERGs, performed in 4 patients, were used to assesspostreceptoral cone on and off pathways, predominantly arising in relation to depolarizing andhyperpolarizing bipolar cell function.13,14 The duration of the amber stimulus (620 nm) was150 or 200 milliseconds. Stimulus luminance was 560 candela (cd)/m2 with a green background(530 nm) of 160 cd/m2, suitable to suppress rod function.15 Pupils were dilated before full-field ERG testing using tropicamide (1%) and phenylephrine hydrochloride (2.5%). TheISCEV standard pattern ERGs were performed16 before mydriasis, and the P50 componentwas used to assess macular function.17

All 7 patients were screened for RS1 mutations. DNA was extracted from blood. Extractedgenomic DNA was amplified for sequencing in 50 μL of polymerase chain reaction solutionusing standard methods.18

ResultsClinical and genetic features of all 7 patients are summarized in Table 1; fundus photographsare shown in Figures 1, 2, 3, and 4. Six of 7 patients initially sought care in early childhoodfor reduced visual acuity. Three patients retained a visual acuity of 20/80 or better in at least1 eye, including 2 older patients, aged 49 years (patient 3) and 46 years (patient 5). One patienthad a 20-year history of floaters in the right eye after blunt trauma but recently sought care forworsening night vision (patient 3). All 7 patients had an abnormal fundus appearance at themacula characterized by multiple fine white spots that resembled drusenlike deposits at the

Tsang et al. Page 2

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

level of the retinal pigment epithelium (RPE), and these were bilateral in all patients (Figures1, 2, 3, and 4). Pigmentation abnormalities in the RPE were seen bilaterally in 7 patients.Autofluorescence imaging confirmed atrophic changes in patients 2 (Figure 2C and D) and 3(Figure 3C and D). No patient showed typical foveal schisis, although this had beendocumented in 1 patient 7 years previously (patient 5). Schitic lesions were present inferiorlyin both eyes of patient 7 and in the left eye of patient 1 (Figure 1H). Mutations in intron 1 (1patient) and exons 1 (1 patient), 4 (4 patients), and 6 (1 patient) of the RS1 gene (Xp22.2-Xp22.1) established the diagnosis.

Pattern and full-field ERG findings in all 6 patients tested are summarized in Table 2. PatternERG P50 components were abnormal in all 6 patients. Two patients showed bilaterallyundetectable pattern ERGs, with a further 2 having an undetectable pattern ERG in 1 eye. Full-field ERGs indicated generalized retinal dysfunction affecting rod and cone systems, and inall cases maximal ERG configurations were electronegative, consistent with a locus ofdysfunction after phototransduction at the level of the inner retina. Three illustrative cases aredescribed in detail.

Patient 1A white boy was found to have decreased vision on a routine examination by his pediatricianat 3½ years of age. Shortly afterward he was noted to have “speckling at the back of both eyes.”There was no other relevant medical history.

Visual acuity at age 12 years was 20/40 OD and 20/60 OS. Fundus examination revealed finewhite drusenlike deposits around the foveae (Figure 1A-D). No peripheral cystic changes werefound at initial examination and up to 18 years of age. The white dots were more apparent onred-free photographs (Figure 1C and D). The diagnosis of Stargardt disease was initiallyentertained until the results of full-field ERG studies suggested otherwise.

Pattern ERG P50 components were subnormal bilaterally, in keeping with bilateral maculardysfunction (Figure 1I). Full-field ERGs showed borderline reduction in the rod-specific ERG;maximal ERG a-waves were normal but waveforms were mildly electronegative. Photopic 30-Hz flicker ERGs were mildly delayed, without significant amplitude reduction; transientphotopic ERGs showed a low b/a ratio. Overall, the findings were consistent with generalizedretinal dysfunction affecting rod and cone systems, with a locus of dysfunction afterphototransduction.

During the next 6 years, his vision remained stable at 20/40 OD and 20/80 OS. Fundusexamination showed no gross changes. Autofluorescence imaging revealed localized high-density pinpoint lesions that corresponded to the white dots (Figure 1E and F). No foveal schisiswas detectable in either eye using OCT (Figure 1G and H), but the left eye showed cysticjuxtafoveal changes (Figure 1H). Genetic analysis showed a 305G→A mutation in exon 4 ofthe RS1 gene. This mutation introduces an altered amino acid (R102Q) into the retinoschisin.

Patient 2A 47-year-old Chinese man complained of slowly progressive worsening of vision in both eyessince age 8 years. Stargardt disease had been suspected. There was no known family historyof ophthalmic problems. Visual acuity was 20/200 OU. Fundus examination revealed multiplefine white spots around the foveae, with some RPE pigmentation changes (Figure 2A and B).No peripheral schisis was detected. Optic nerve heads and retinal vessels were normal.Autofluorescence revealed low-density macular lesions consistent with atrophy surrounded bya ring of high density bilaterally (Figure 2C and D). Electroretinographic findings are shownin Figure 2E. The on-off ERGs were consistent with involvement of cone on and off bipolar

Tsang et al. Page 3

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

pathways. Pattern ERGs were undetectable, indicating severe macular dysfunction bilaterally.Genetic analysis revealed a novel 206T→C mutation in exon 4 of the RS1 gene.

Patient 3A 49-year-old hyperopic white man complained of progressive night blindness. He had a 20-year history of floaters in the right eye after blunt trauma. He had hyperopic correction. Changesin the right vitreous gel and a preretinal inferior vitreous band were reported. Both eyes showedinferior shallow schisis, and there was a hole in the left retinal periphery that was subsequentlytreated with photocoagulation. He had no family history of any ophthalmic condition. Fouryears later the patient reported intermittent distortion of vision in the right eye. Visual acuitywas 20/40 OD and 20/30 OS. The right macula showed stippling with multiple white spots;the left retina showed a subtle granularity. There was no evidence of foveal schisis.

Six years after initial examination, the visual acuity had deteriorated to 20/200 OD and 20/40OS. There was bilateral granularity of the macula (Figure 3A), worse in the right eye than theleft (Figure 3B). Inferior leaf breaks were present and were more noticeable in the left fundus.In the right eye, low-density autofluorescence over the central macula was surrounded by aparafoveal ring of high density. There was also a low-density patch in the arcades, superiorand slightly temporal to the optic disc. In the left eye, there were patches of low density overareas superior to and nasal to the fovea (Figure 3C and D).

Mildly electronegative maximal ERG findings were consistent with generalized inner retinaldysfunction. Photopic ERG findings were abnormal, and on-off ERG findings were consistentwith involvement of cone on and off bipolar pathways. There was pattern ERG evidence ofsevere macular dysfunction (Table 2 and Figure 3E). Genetic analysis revealed a C579dupCmutation in exon 6 of the RS1 gene.

CommentAll 7 patients had an abnormal fundus appearance at the macula characterized by multiple finewhite dots at the level of the RPE that resembled drusenlike deposits (Figures 1, 2, 3, and 4).The findings were bilateral in all patients and were often associated with pigmentationabnormalities of the RPE. No patient showed typical foveal schisis, although this had beenreported in patient 5 seven years previously. Most patients were first seen by us at 45 years orolder, and it is possible that macular schisis may have been present before the white dotsappeared. The absence of foveal schisis was not always associated with confluent atrophy, andvisual acuity was relatively preserved in some of the older patients (Table 1). Two patients hadschitic lesions away from the central macula. Findings from ERG were consistent withgeneralized inner retinal dysfunction of both rod and cone systems (Table 2 and Figures 1, 2,and 3) and suggested the unsuspected diagnosis of XLRS in most patients.

Foveal or parafoveal white dots or flecks are commonly associated with a variety of disorders,including Stargardt-fundus flavimaculatus (initially considered in 2 of the patients describedin the present study), retinitis punctata albescens, Goldmann-Favre syndrome, Wagnervitreoretinal dystrophy, yellow dot dystrophy, and other forms of macular dystrophy.19

However, none of those disorders typically manifest an electronegative ERG configuration.Fundus albipunctatus often shows a myriad of symmetrical round white flecks, with the greatestconcentration in the midperiphery, but those patients always have night blindness, not a featureof the present cohort. The drusenlike multiple white spots described in the present patientswere sometimes associated with atrophic changes at the macula, a common finding in olderpatients with XLRS, but could be the only fundus abnormality. The spots were not typical ofthose associated with age-related maculopathy. A similar matrix of extensive white flecks hasbeen described in 2 individuals with juvenile retinoschisis20 and more recently in 2 additional

Tsang et al. Page 4

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

patients with confirmed RS1 defects, including a 214G→A defect.21 Those flecks wereassociated with typical star-shaped macular lesions (foveal schisis) and did not resemble thedrusenlike white dots described in the present study, even in a patient carrying an identicalmutation (patient 5). Macular white dots have not previously been described in individualscarrying the previously reported RS1 alleles: 305G→A, 214G→A, 579dupC, 325G→T, IVS1+ 2T→C, and exon 1 deletion.4 The 206T→C mutation in patient 2 is a novel mutation.

It is difficult to assess the incidence of this phenotype. The primary aims of this retrospectivestudy were to report a previously unsuspected phenotype of XLRS and to highlight the role ofelectrophysiologic assessment in identifying these patients. Patients with characteristic fundusfeatures and a positive family history may have been diagnosed without using moleculargenetic screening, and not all patients were referred for electrodiagnostic testing. For diagnosticpurposes, equivocal or unusual cases were more likely to be screened genetically, giving askewed impression of phenotype in this genetically confirmed cohort. All but 1 of the mutationsin the present study have been reported by the Retinoschisis Consortium.18 The presence ofwhite dots is unlikely to be age or genotype specific because patients with identical mutationshave not manifest the same fundus appearance.

Autofluorescence imaging revealed abnormal foci of high density that corresponded with thewhite dots (Figure 1). The autofluorescence emission spectrum closely resembles that oflipofuscin, a byproduct of outer segment shedding. High-density autofluorescence lesionssuggest localized accumulation of lipofuscin and disruption of RPE metabolism that mayeventually be associated with photoreceptor death. Atrophy of the RPE manifests as absentautofluorescence. In 2 other patients (Figures 2 and 3), low-density central areas correspondedwith macular atrophy in 3 of 4 eyes that were surrounded by a ring of high density not previouslydescribed in XLRS. These annuli of high density resemble those present in some patients withretinitis pigmentosa and normal visual acuity22-24 that have been shown to surround areas ofnormal autofluorescence and preserved photopic function. They may constrict with time.25

Rings surrounding areas of central atrophy have also been described in some cases of cone-rod dystrophy26,27 that show a gradient of sensitivity loss across the arc of hyperfluorescence.28 The autofluorescence rings in XLRS may represent an intermediate stage of increasedphotoreceptor-RPE metabolic load before cell loss and atrophy seen in many older individuals(>45 years) with XLRS.

The 6 patients tested electrophysiologically had findings in keeping with inner retinaldysfunction, typical of XLRS.5,29,30 Rod-specific ERGs of inner retinal origin are usuallyundetectable or markedly reduced.31 Scotopic bright-flash ERGs are typically electronegative,although in rare cases maximal b-wave amplitudes have been reported as normal.30,32 Photopicand 30-Hz flicker ERGs are usually subnormal and delayed. Pattern ERGs showed variabledegrees of reduction in all 6 patients, in keeping with previous studies31,33 of maculardysfunction in this disorder. Full-field ERG abnormalities indicate generalized retinaldysfunction that is consistent with widespread expression of retinoschisin in the retina. In a19-year-old normal human eye, retinoschisin was found abundantly in the inner segments ofthe photoreceptors and the outer nuclear layer; moderate levels were also detected in the innernuclear and plexiform layers.34 Reduced retinoschisin immunoactivity was observed in theperipheral retina of a patient of the same age with XLRS.34

Retinoschisin may be essential in on-bipolar and associated cell-cell interactions. Loss ofretinoschisin in the mouse results in disrupted synaptic interactions between photoreceptorsand bipolar neurons in the outer plexiform layer.35,36 Abnormal centrifugal displacement ofdendrites and synapses during foveal development may explain the radial macular lesions oftenseen in humans.37 The on-off ERG recordings of some patients with XLRS have shown areduced b-wave–d-wave ratio, suggesting that cone on-bipolar signaling may be the primary

Tsang et al. Page 5

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

defect.13 In other patients, the on and off responses are affected,31,38 consistent with abnormalsignaling by the on and off pathways.31,38 It has been our experience that some patients withXLRS have relative off-pathway sparing and others have clear off-pathway involvement.31

In summary, multiple fine white macular dots may be a manifestation of XLRS unaccompaniedby the typical foveal spoke-wheel lesions. Findings from autofluorescence studies suggest thatthe RPE is involved in the early stages of the disease. Electrophysiologic assessment plays animportant role in the documentation of postreceptoral dysfunction and may enable focusedDNA screening.

AcknowledgmentsFunding/Support: This study is supported by a fellowship from the Burroughs-Wellcome Program in BiomedicalSciences, the Dennis Jahnigen Award from the American Geriatrics Society, the Hirschl Charitable Trust, the JoelHoffmann Foundation, the Schneeweiss Stem Cell Fund, and the Association of University Professors inOphthalmology–Research to Prevent Blindness and Eye Surgery Fund (Dr Tsang); by the Foundation FightingBlindness (Drs Tsang, Bird, and Robson); and by grant EY004081 from the National Institutes of Health (Dr Tsang).

We thank Andrew R. Webster, MD, Sharon Jenkins, MSc, and the members of their laboratories for sharing ideas andresources and for critical reading of the manuscript and Stanley Chang, MD, for guidance and advice.

References1. Deutman AF, Pickers AJL, Aan de Kerk AL. Dominantly inherited cystoid macular edema. Am J

Ophthalmol 1976;82:540–548. [PubMed: 970419]2. Traboulsi, E., editor. Genetic Disease of the Eye. Oxford, England: Oxford University Press; 1998.

Oxford Monographs on Medical Genetics; No. 363. George ND, Yates JR, Moore AT. X linked retinoschisis. Br J Ophthalmol 1995;79:697–702. [PubMed:

7662639]4. Pimenides D, George ND, Yates JR, et al. X-linked retinoschisis: clinical phenotype and RS1 genotype

in 86 UK patients. J Med Genet 2005;42:e35. [PubMed: 15937075]5. Kellner U, Brummer S, Foerster MH, Wessing A. X-linked congenital retinoschisis. Graefes Arch Clin

Exp Ophthalmol 1990;228:432–437. [PubMed: 2227486]6. Wu WW, Wong JP, Kast J, Molday RS. RS1, a discoidin domain-containing retinal cell adhesion

protein associated with X-linked retinoschisis, exists as a novel disulfide-linked octamer. J Biol Chem2005;280:10721–10730. [PubMed: 15644328]

7. Hayashi T, Omoto S, Takeuchi T, Kozaki K, Ueoka Y, Kitahara K. Four Japanese male patients withjuvenile retinoschisis: only three have mutations in the RS1 gene. Am J Ophthalmol 2004;138:788–798. [PubMed: 15531314]

8. Yanoff M, Kertesz Rahn E, Zimmerman LE. Histopathology of juvenile retinoschisis. ArchOphthalmol 1968;79:49–53. [PubMed: 5635090]

9. Arden GB, Gorin MB, Polkinghorne PJ, Jay M, Bird AC. Detection of the carrier state of X-linkedretinoschisis. Am J Ophthalmol 1988;105:590–595. [PubMed: 3377039]

10. Robson AG, Moreland JD, Pauleikhoff D, et al. Macular pigment density and distribution: comparisonof fundus autofluorescence with minimum motion photometry. Vision Res 2003;43:1765–1775.[PubMed: 12818346]

11. von Ruckmann A, Fitzke FW, Bird AC. Distribution of fundus autofluorescence with a scanning laserophthalmoscope. Br J Ophthalmol 1995;79:407–412. [PubMed: 7612549]

12. Marmor MF, Holder G, Seeliger M, Yamamoto S. International Society for ClinicalElectrophysiology of Vision. Standard for clinical electroretinography (2004 update). DocOphthalmol 2004;108:107–114. [PubMed: 15455793]

13. Alexander KR, Barnes CS, Fishman GA. High-frequency attenuation of the cone ERG and ON-response deficits in X-linked retinoschisis. Invest Ophthalmol Vis Sci 2001;42:2094–2101.[PubMed: 11481277]

Tsang et al. Page 6

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

14. Sieving PA. Photopic ON- and OFF-pathway abnormalities in retinal dystrophies. Trans AmOphthalmol Soc 1993;91:701–773. [PubMed: 8140708]

15. Robson AG, Richardson EC, Koh AH, et al. Unilateral electronegative ERG of non-vascularaetiology. Br J Ophthalmol 2005;89:1620–1626. [PubMed: 16299143]

16. Bach M, Hawlina M, Holder GE, et al. International Society for Clinical Electrophysiology of Vision.Standard for pattern electroretinography. Doc Ophthalmol 2000;101:11–18. [PubMed: 11128964]

17. Holder GE. Pattern electroretinography (PERG) and an integrated approach to visual pathwaydiagnosis. Prog Retin Eye Res 2001;20:531–561. [PubMed: 11390258]

18. Retinoschisis Consortium. Functional implications of the spectrum of mutations found in 234 caseswith X-linked juvenile retinoschisis. Hum Mol Genet 1998;7:1185–1192. [PubMed: 9618178]

19. Ho, A.; Brown, G.; McNamara, J.; Recchia, F.; Regillo, C.; Vander, J. Retina. Barcelona, Spain:McGraw-Hill; 2003.

20. van Schooneveld MJ, Miyake Y. Fundus albipunctatus-like lesions in juvenile retinoschisis. Br JOphthalmol 1994;78:659–661. [PubMed: 7918299]

21. Hotta Y, Nakamura M, Okamoto Y, Nomura R, Terasaki H, Miyake Y. Different mutation of theXLRS1 gene causes juvenile retinoschisis with retinal white flecks. Br J Ophthalmol 2001;85:238–239. [PubMed: 11225572]

22. Robson AG, El-Amir A, Bailey C, et al. Pattern ERG correlates of abnormal fundus autofluorescencein patients with retinitis pigmentosa and normal visual acuity. Invest Ophthalmol Vis Sci2003;44:3544–3550. [PubMed: 12882805]

23. Robson AG, Egan CA, Luong VA, Bird AC, Holder GE, Fitzke FW. Comparison of fundusautofluorescence with photopic and scotopic fine-matrix mapping in patients with retinitispigmentosa and normal visual acuity. Invest Ophthalmol Vis Sci 2004;45:4119–4125. [PubMed:15505064]

24. Wabbels B, Demmler A, Paunescu K, Wegscheider E, Preising MN, Lorenz B. Fundusautofluorescence in children and teenagers with hereditary retinal diseases. Graefes Arch Clin ExpOphthalmol 2006;244:36–45. [PubMed: 16034607]

25. Robson AG, Saihan Z, Jenkins SA, et al. Functional characterisation and serial imaging of abnormalfundus autofluorescence in patients with retinitis pigmentosa and normal visual acuity. Br JOphthalmol 2006;90:472–479. [PubMed: 16547330]

26. Michaelides M, Holder GE, Hunt DM, Fitzke FW, Bird AC, Moore AT. A detailed study of thephenotype of an autosomal dominant cone-rod dystrophy (CORD7) associated with mutation in thegene for RIM1. Br J Ophthalmol 2005;89:198–206. [PubMed: 15665353]

27. Ebenezer ND, Michaelides M, Jenkins SA, et al. Identification of novel RPGR ORF15 mutations inX-linked progressive cone-rod dystrophy (XLCORD) families. Invest Ophthalmol Vis Sci2005;46:1891–1898. [PubMed: 15914600]

28. Robson A, Michaelides M, Webster A, et al. Comparison of pattern ERG, multifocal ERG andpsychophysical correlates of fundus autofluorescence abnormalities in patients with cone-rod(RPGR, RIM1) or rod-cone dystrophy [ARVO abstract]. Invest Ophthalmol Vis Sci 2005;43:552.

29. Peachey NS, Fishman GA, Derlacki DJ, Brigell MG. Psychophysical and electroretinographicfindings in X-linked juvenile retinoschisis. Arch Ophthalmol 1987;105:513–516. [PubMed:3566604]

30. Bradshaw K, George N, Moore A, Trump D. Mutations of the XLRS1 gene cause abnormalities ofphotoreceptor as well as inner retinal responses of the ERG. Doc Ophthalmol 1999;98:153–173.[PubMed: 10947001]

31. Stanga PE, Chong NH, Reck AC, Hardcastle AJ, Holder GE. Optical coherence tomography andelectrophysiology in X-linked juvenile retinoschisis associated with a novel mutation in the XLRS1gene. Retina 2001;21:78–80. [PubMed: 11217940]

32. Sieving PA, Bingham EL, Kemp J, Richards J, Hiriyanna K. Juvenile X-linked retinoschisis fromXLRS1 Arg213Trp mutation with preservation of the electroretinogram scotopic b-wave. Am JOphthalmol 1999;128:179–184. [PubMed: 10458173]

33. Clarke MP, Mitchell KW, McDonnell S. Electroretinographic findings in macular dystrophy. DocOphthalmol 1996;92:325–339. [PubMed: 9476599]

Tsang et al. Page 7

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

34. Mooy CM, Van Den Born LI, Baarsma S, et al. Hereditary X-linked juvenile retinoschisis: a reviewof the role of Muller cells. Arch Ophthalmol 2002;120:979–984. [PubMed: 12096974]

35. Zeng Y, Takada Y, Kjellstrom S, et al. RS-1 gene delivery to an adult Rs1h knockout mouse modelrestores ERG b-wave with reversal of the electronegative waveform of X-linked retinoschisis. InvestOphthalmol Vis Sci 2004;45:3279–3285. [PubMed: 15326152]

36. Weber BH, Schrewe H, Molday LL, et al. Inactivation of the murine X-linked juvenile retinoschisisgene, Rs1h, suggests a role of retinoschisin in retinal cell layer organization and synaptic structure.Proc Natl Acad Sci U S A 2002;99:6222–6227. [PubMed: 11983912]

37. Takada Y, Fariss RN, Tanikawa A, et al. A retinal neuronal developmental wave of retinoschisinexpression begins in ganglion cells during layer formation. Invest Ophthalmol Vis Sci 2004;45:3302–3312. [PubMed: 15326155]

38. Khan NW, Jamison JA, Kemp JA, Sieving PA. Analysis of photoreceptor function and inner retinalactivity in juvenile X-linked retinoschisis. Vision Res 2001;41:3931–3942. [PubMed: 11738458]

Tsang et al. Page 8

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

Figure 1.Various imaging findings in patient 1. A, and B, Fundus photographs showed fine intraretinalwhite lesions along the venules and arterioles of the perifoveolar vascular network. Retinalpigment epithelium disturbance associated with mildly thickened retina is seen over thesuperior part of the macula of the left eye. C, Red-free photograph of the right eye. D, Red-free photograph of the left eye. E and F, Confocal scanning laser ophthalmoscopic imagesrevealed increased autofluorescence signal associated with the white dots. G, Foveal schisiswas not detected by means of optical coherence tomography in the right macula. H, Parafovealand peripheral microcystic changes were seen via optical coherence tomography in the lefteye. I, Full-field and pattern electroretinograms (ERGs). Rows 1 and 2 show recordings from

Tsang et al. Page 9

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

the right and left eyes, respectively, of the patient; row 3, normal recordings. LU indicates logunits. Ordinal axes are shown in microvolts, allowing measurement of ERG amplitudes.

Tsang et al. Page 10

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

Figure 2.Fundus photographs (A and B) and fundus autofluorescence (C and D) in patient 2. Fineintraretinal white dots were seen in and adjacent to the central atrophic retinal pigmentepithelium. Autofluorescence showed low-density signal over macular atrophy surrounded bya ring of high density. The observed ring of hyperfluorescence was consistent with retinalpigment epithelium disturbance outside of atrophic areas. E, Full-field and patternelectroretinograms (ERGs). Rows 1 and 2 show recordings from the right and left eyes,respectively, of the patient; row 3, normal recordings. LU indicates log units. Ordinal axes areshown in microvolts, allowing measurement of ERG amplitudes.

Tsang et al. Page 11

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

Figure 3.Fundus photographs (A and B) and autofluorescence (C and D) in patient 3 showing multifocalfine intraretinal white dots in the foveal regions. Low-density autofluorescence at the maculae,larger in the right eye (C), was surrounded by a ring of high density, suggesting a retinal pigmentepithelium disturbance outside of atrophic areas. E, Full-field and pattern electroretinograms(ERGs). Rows 1 and 2 show recordings from the right and left eyes, respectively, of the patient;row 3, normal recordings. LU indicates log units. Ordinal axes are shown in microvolts,allowing measurement of ERG amplitudes.

Tsang et al. Page 12

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

Figure 4.Fundus photographs in patients 4 (A and B), 5 (C and D), 6 (E and F), and 7 (G and H) showingnumerous white dots at the macula in all cases.

Tsang et al. Page 13

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

Tsang et al. Page 14

Table 1Phenotypic Manifestations of RS1 Mutations

Patient No./Age, y VA, OD/OS RS1 Mutation Macular Appearance Clinical History

1/12 20/40 20/60 305G→A in exon 4 Fine white parafoveal dots in both eyes Previously diagnosed as having Stargardtdisease. Normal vessels and discs. Whitedots correspond with high-density AF.OCT showed normal foveae andperipheral schisis in the left eye.

2/47 20/200 20/200 206T→C in exon 4 (novel) Fine white parafoveal dots and RPE atrophy inboth eyes

Previously diagnosed as having Stargardtdisease. No visible peripheral schisis.Normal vessels and discs. AF showedlow-density AF over macular atrophysurrounded by a ring of high density.

3/49 20/40 20/30 C579dupC in exon 6 Granular appearance and fine white dots in botheyes

Low-density area of AF at maculae,larger in the right eye, surrounded by aring of high density in the right eye. Righteye trauma 20 y ago. Inferior leaf breaksbilaterally, worse in the left eye. Inferiorshallow schisis in both eyes.

4/46 20/100 20/200 IVS1 + 2T→C in intron 1 Fine white parafoveal dots in both eyes;atrophic scar in the left eye

No visible foveal schisis but a temporalschitic lesion extending beyond thesuperior arcade in the left eye.

5/46 20/80 20/200 214G→A in exon 4 Fine white dots and RPE granularity in bothmaculae

Initially diagnosed as having Goldmann-Favre syndrome on the basis of macularschisis. White dots and pigment clumpingseen 7 y ago; VA: 20/100 OD and 20/100OS.

6/54 20/120 20/200 325G→T in exon 4 Fine white dots and RPE pigmentationabnormalities in both maculae

Initially diagnosed as having “maculardegeneration.” Normal vessels and discs.VA: 20/200 OU 3 y after initialexamination.

7/50 20/200 20/200 Deletion of the entire exon 1 White dots and RPE pigmentationabnormalities in both eyes

Previously diagnosed as having “maculardegeneration.” Inferior schitic lesions inboth eyes. Normal vessels and discs.Nephew (aged 32 y) has typical fovealschisis.

Abbreviations: AF, autofluorescence; OCT, optical coherence tomography; RPE, retinal pigment epithelium; RS1, retinoschisis (X-linked, juvenile) 1;VA, visual acuity.

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

NIH

-PA Author Manuscript

Tsang et al. Page 15Ta

ble

2Su

mm

ary

of E

lect

roph

ysio

logi

c Fi

ndin

gs*

Patie

nt N

o.R

od E

RG

Am

plitu

deM

axim

um a

-Wav

e A

mpl

itude

Max

imal

ER

G b

/aR

atio

30-H

z T

imin

g30

-Hz

Am

plitu

de

Phot

opic

ER

Ga-

Wav

eA

mpl

itude

Phot

opic

ER

G b

-W

ave

Am

plitu

de

Phot

opic

ER

G b

/aR

atio

Patte

rnE

RG

P50

Am

plitu

deO

n-O

ff E

RG

s

1N

N0.

98A

NN

(hig

h am

p)N

1.7

AN

P

AN

0.96

AN

N (h

igh

amp)

N1.

7A

NP

2A

N0.

89A

NN

A2.

0U

Red

uced

b-w

ave,

dela

yed

d-w

ave,

both

eye

sA

N0.

90A

A (m

ild)

NA

1.8

U

3A

N0.

90A

NN

A1.

7U

Red

uced

b-w

ave,

dela

yed

d-w

ave,

both

eye

sA

N0.

82A

NN

A2.

3U

4A

N0.

55A

A (m

ild)

NA

2.0

UR

educ

ed b

- and

d-w

aves

, bot

hey

esA

N0.

60A

A (m

ild)

NA

2.0

A+

5A

N0.

95A

NN

(hig

h am

p)N

2.3

At

AN

0.98

AN

N (h

igh

amp)

N2.

2A

t

6t

N0.

79A

A (m

ild)

NA

3.0

UR

educ

ed b

- and

d-w

aves

, rig

htey

e. N

P, le

ft ey

e.t

N0.

71A

A (m

ild)

NA

1.8

A+

Abb

revi

atio

ns: A

, abn

orm

al; A

+, v

ery

abno

rmal

; ER

G, e

lect

rore

tinog

raph

y; N

, nor

mal

; NP,

not

per

form

ed; t

, tec

hnic

ally

uns

atis

fact

ory

(eye

mov

emen

t) U

, und

etec

tabl

e.

* Rig

ht e

ye fi

ndin

gs a

re sh

own

abov

e le

ft ey

e fin

ding

s exc

ept w

here

stat

ed.

Arch Ophthalmol. Author manuscript; available in PMC 2009 October 6.