Visual Acuity in Patients with Leber's Congenital Amaurosis and Early Childhood-Onset Retinitis Pigmentosa

Visual Acuity in Patients with Leber’s Congenital Amaurosis and Early Childhood-Onset Retinitis Pigmentosa Saloni Walia, MD,1 Gerald A. Fishman, MD,1 Samuel G. Jacobson, MD, PhD,2 Tomas S. Aleman, MD,2 Robert K. Koenekoop, MD, PhD,3 Elias I. Traboulsi, MD,4 Richard G. Weleber, MD,5 Mark E. Pennesi, MD, PhD,5 Elise Heon, MD,6 Arlene Drack, MD,7 Byron L. Lam, MD,8 Rando Allikmets, PhD,9 Edwin M. Stone, MD, PhD10 Purpose: To correlate visual acuity of patients with Leber’s congenital amaurosis (LCA) and early childhoodonset retinitis pigmentosa (RP) with mutations in underlying LCA genes. Design: Multicentered retrospective observational study. Participants: After exclusion of 28 subjects, 169 patients with the diagnosis of LCA and 27 patients with early childhood-onset RP were included in the study because the underlying mutations in AIPL1, GUCY2D, RDH12, RPE65, CRX, CRB1, RPGRIP1, CEP290, LCA5, and TULP1 genes could be identified in this cohort of patients. Methods: We collected data on best-corrected visual acuity as recorded at the time of the patient’s most recent visit to one of the participating ophthalmology departments. The median and range of visual acuities for each genetic subtype were calculated separately for the LCA and early childhood-onset RP groups. Main Outcome Measures: The range and median best-corrected visual acuities for each genetic subtype and age-related mean visual acuities for each genetic subtype. Results: A wide variation in visual acuity was observed in patients with LCA and RPE65, RDH12, and CRB1 mutations, whereas AIPL1, GUCY2D, CRX, and RPGRIP1 gene mutations were associated with severely decreased visual acuities beginning within the first year of life. It was also noted that patients with either an RPE65 or CRB1 mutation have progressive visual loss with advancing age. Onset of visual symptoms after infancy was associated with a relatively better visual prognosis. Conclusions: The data obtained from this study will help clinicians provide counseling on visual prognosis to patients with known mutations in LCA genes and be of value in future studies aimed at the treatment of LCA and early childhood-onset RP. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Ophthalmology 2010;117:1190 –1198 © 2010 by the American Academy of Ophthalmology.

Leber’s congenital amaurosis (LCA) was first described by Theodore Leber in 1869.1 It is an inherited retinal disorder most often diagnosed in infancy in the first 6 months of life and characterized by the presence of nystagmus, poor visual acuity (VA), and a severely reduced or nondetectable electroretinogram.2– 4 Several previous and small studies have reported on VA measurements in patients with LCA. These studies are from the “pregenomic era,” and therefore preclude valuable genotype–phenotype associations between final VA and LCA mutations. Fulton et al5 measured grating VA in 36 children with LCA and found a median grating of 1.27 cycles/degree (⬃20/500) in 18 patients. In the other half of these patients, grating VA could not be measured with 12 patients having no light perception (NLP). Heher et al6 performed a retrospective study on VA in 35 patients with LCA with an age range from 3 months to 33 years and observed a VA range from 20/100 to NLP. Other studies have also reported a similar range of VA in patients with

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LCA.2,7–11 A few investigations have also reported that VA in the majority of patients with LCA remains stable when they are followed for long periods of time.2,6 However, the number of patients with LCA in these studies was relatively small. Currently, mutations in 14 retinal genes are now known to cause LCA.12 These genes encode proteins with different retinal functions, such as photoreceptor morphogenesis, phototransduction, vitamin A cycling, guanine synthesis, outer segment phagocytosis, and intra-photoreceptor ciliary transport.12 Significant visual loss has been noted in patients with AIPL1,8,13 RPGRIP1,8,14 CEP290,10,15 and GUCY2D7,8 mutations. A wide range of VA is associated with CRB1 and RPE65 mutations.8 The present study is a multicentered retrospective study aimed at analyzing VA data and their correlation with various underlying genetic mutations in a large group of patients with LCA and early childhood-onset retinitis pigmentosa (RP). These data will be of value for counseling ISSN 0161-6420/10/$–see front matter doi:10.1016/j.ophtha.2009.09.056

Walia et al 䡠 VA in LCA and Early Childhood-Onset RP families affected with various genetic subtypes of LCA and for identifying a cohort of subjects who might participate in future treatment trials.

Materials and Methods The diagnostic criteria for LCA included a history of visual impairment within the first year of life, the presence of nystagmus in most cases, and nondetectable or severely reduced rod and cone electroretinogram amplitudes (in most patients; some patients were diagnosed on the basis of clinical examination alone). For the purpose of this study, we defined the age limit for LCA when the onset of visual disturbance was noted by parents before and up to the age of 1 year. Early childhood-onset RP was defined as severe visual symptoms commencing after age 1 year and until age 5 years and the presence of mutations in one of the LCA genes. For members of the same family, the sibling with the earliest age of onset was used to classify the family into LCA or early childhoodonset RP. Patients with known associated non-ocular features suggesting a syndromic disorder were excluded from the study. However, patients with keratoconus or cataract were not excluded. Also excluded were any patients with other ocular diseases that might cause a decrease in VA. Patients for whom reliable VA measurements could not be obtained were also excluded from the study. Any patients with mutations in more than 1 gene that may cause LCA or early childhood-onset RP were also excluded from the current study. The data were pooled from 8 centers: the University of Illinois at Chicago, Casey Eye Institute, University of Pennsylvania, Bascom Palmer Eye Institute, University of Iowa, University of Toronto, Cole Eye Institute, and McGill University Health Center. To prevent any duplication, date of birth or initials were compared across the data that were possible for the majority of entries. One Canadian center was unable to provide dates of birth or patient initials because of an institutional review board’s constraints. Informed consent was obtained from all participating patients or their legal guardians at the centers where they were examined. Approval was obtained from the institutional review boards at the University of Illinois and participating centers, and the study was conducted in accordance with the Health Insurance Portability and Accountability Act and in accordance with the tenets of Declaration of Helsinki. Because of the retrospective nature of the study, VA was recorded using different VA charts depending on the age and extent of vision impairment of individual patients. The various VA charts that were used included the Snellen VA chart, Early Treatment of Diabetic Retinopathy Study VA chart, Feinbloom acuity chart, Allen picture chart, Teller acuity cards, and HOTV acuity chart. The best-corrected visual acuity (BCVA) in the better eye at the most recent visit was used for the present study. Most patients were refracted to obtain BCVA; however, some patients with vision of hand motion or worse did not undergo refraction. All VA data were converted to the logarithm of the minimum angle of resolution by taking the log10 of the inverse of the VA obtained from all charts. VA of counting fingers (CF), hand motion, light perception (LP), or NLP was assigned the values of 2.6, 2.7, 2.8, and 2.9, respectively.16 Findings from individual patients with the following mutations have been published: AIPL1,8 CEP290,17 RPE65,8,18 –25 GUCY2D,8,26 CRX,8,27 RPGRIP1,8,17,28 RDH12,21 and CRB1.8,22 Gene screening occurred in at least 1 of 3 locations following methodology described below. At Columbia University, the LCA mutations were initially identified by the LCA disease microarray (disease chip) from

Asper Ophthalmics (Tartu, Estonia).29 This chip currently contains more than 500 known mutations in 12 LCA genes, version 2009. Array-identified variants were confirmed by direct sequencing with the Taq Dyedeoxy Terminator Cycle Sequencing kit (Applied Biosystems, Foster City, CA), according to the manufacturer’s instructions. Sequencing reactions were resolved on an ABI 3100 automated sequencer. At McGill University, the LCA mutation detection protocol is as follows. After DNA collection, the common CEP290 mutation (p. Cys998X) was excluded by a specifically designed ARMS primer (available on request). In step II, the remaining DNA of patients with LCA or early childhood-onset RP was screened by the LCA micro-array (Asper Ophthalmics), and positive results were confirmed by direct sequencing (ABI 3100). Patients with heterozygous mutations were subjected to further sequencing analysis of the same gene to identify the LCA mutation on the second allele. In step III, patients with negative LCA microarray results were subjected to single nucleotide polymorphism microarray genotyping (10K for consanguineous and 100K for non-consanguineous patients). When homozygous stretches of single nucleotide polymorphisms (⬎38 single nucleotide polymorphisms) overlapped with known LCA genes, this center sequenced these LCA genes, identified new homozygous mutations, and added those to the Asper chip.30 At the University of Iowa, genetic analysis was performed by isolating the DNA from human blood using the Autopure LS (Qiagen, Hilden, Germany). Genetic screening included polymerase chain reaction assay, single-stranded conformational polymorphism analysis, and denatured high-pressure liquid chromatography wave analysis (Transgenomic Inc., Omaha, NE). Single-stranded conformational polymorphism analysis or denatured high-pressure liquid chromatography variants were further analyzed by direct nucleotide sequencing or automated sequencing on an ABI prism 3100 (Perkin Elmer Applied Biosystems, Wellesley, MA).

Results The various mutations in the different genetic subtypes of this cohort of patients are listed in Tables 1 and 2.

Leber’s Congenital Amaurosis Group A total of 197 patients from 167 families with a diagnosis of LCA and known mutations on 1 or 2 alleles of a known LCA gene were included in the study. Subsequently, 28 subjects were excluded because of insufficient data or the presence of other factors that may have contributed to a decrease in VA. There were 101 Caucasian patients, 12 patients of African descent, 6 Hispanic patients, 9 Asian patients, and 41 patients with unknown racial background. The group consisted of 100 female patients and 69 male patients. Mutations were found in AIPLI (17 patients), CEP290 (39 patients), RPE65 (54 patients), GUCY2D (11 patients), CRX (6 patients), RPGRIP1 (9 patients), RDH12 (4 patients), CRB1 (28 patients), and LCA5 (1 patient) genes in the LCA group. Genetic Mutations Affecting Photoreceptor Phototransduction: AIPL1, GUCY2D. A total of 17 patients were included with mutations in the AIPL1 gene in 1 (5) or 2 (11) alleles (data on alleles in 1 patient were not available). The range of VA seen in this group was from 20/80 to NLP, and the median VA was 2.8 (equivalent to vision of LP). In this cohort, 12 patients (70.6%) had VA of CF, hand motion, LP, or NLP (VAⱕ2.6) (Fig 1). One patient in this group had NLP, and 16 patients (94.1%) had central vision less than 20/400. Only 1 patient was found to have clinically

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Table 1. Mutations in Genes Involved in Phototransduction (AIPL1, GUCY2D) and Retinoid Cycle (RPE65, RDH12) AIPL1

GUCY2D

Allele 1

Allele 2

Allele 1

Allele 2

IVS2-2 A⬎G T114I Y278X W278X M79T W278X W278X T114I R302L V71F

— — Y278X W278X W278X IVS2-2 A⬎G — P376S — V71F

R660X E692fsX21 R660Q L954P IVS15-1G T312M L782H

— E692fsX21 deletion in complementary allele S981del (G) 1 bp IVS15-1G — L782H

RPE65 Allele 1

Allele 2

N321 1 bp ins R91W 1 bp ins T codon 354-356 1 bp del of G at codon 46 G40S 3= 5 bp G-A intron splice site exon 1 V473D Y238D 20 bp del codon 98-104 G484D N321K R91W A500del5bp R44Q 97del20bp L341S Y368H L408P V287F L341S G40S

R124X T162P A393E E102X H182Y 3= 5 bp G-A intron splice site exon 1 — — 20 bp del codon 98-104 — N321K R91W A500del5bp R44Q 97del20bp IVS2-2A⬎C Y368H L408P V287F L341S R91Q

RDH12 Allele 1

Allele 2

Allele1

Allele 2

R91Q R91W E417Q R91W G104D Y368H

IVS7⫹4A⬎G R44Q E417Q 1059_1060ins1bp G40S 297del1bp

V238ins1gtC S165del5bp L99I V233D C285Y A47T

V238ins1gtC A62stop L99I del 4 bp TCCA codon 19 C285Y L99I

IVS1⫹5G⬎A IVS1⫹5G⬎A Y144D K303X K303X Y239D R124X V287F N321K H182R FS R55W G⬎A IVS1 ⫹5 R118S A132T

W460X IVS1⫹5G⬎A Y144D Y431C Y431C Y368H — V287F — H182R — IVS1⫹5G⬎A L341S V443A A132T

T55M

R295X

apparent keratoconus. More than half of the patients in this group had a hyperopic spherical equivalence of ⱖ 1 diopter (D) (52.9%). Mutations on 1 (2) or 2 (7) alleles in GUCY2D group were found in 11 patients (data on alleles in 2 patients were not provided). The VA ranged from 20/200 to NLP in these patients with a median VA of 2.8 (LP vision). Ten patients in this group had vision less than 20/400 (90.9%), and vision of CF or worse was seen in 7 patients (63.6%) (Fig 1). Vision of NLP was found in 1 patient. Keratoconus was seen in 1 patient, and data on the corneal status were not available for 1 patient. Of all the patients in this group, 8 had a hyperopic spherical equivalence of ⱖ 1 D (72.7%). Genetic Mutations Affecting the Retinoid Cycle: RDH12, RPE65. Mutations in the RDH12 gene were found in 2 alleles in 4 patients with LCA. All patients had VA of 20/200 or better. Visual acuity ranged from 20/63 to 20/200 with a median VA of 0.82 (approximately ⫽ 20/125). Half of the patients in the RDH12 group were hyperopic with a spherical equivalence of ⱖ 1 D, and refraction was not performed on 1 patient. There were 54 patients with RPE65 mutations. Both allelic mutations were known in 46 patients, and only 1 allelic mutation was known in 8 patients. Visual acuity in these patients ranged between 20/32 and NLP with a median of 1.05 (⫽20/225). Only 1 patient (1.9%) had a VA of NLP. Visual acuity of 20/400 or better was present in 50% of patients (n⫽27) (Fig 1). Keratoconus was

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detected in 2 patients, and records on the corneal status were not available on 2 patients. A spherical equivalence myopia of ⱖ 1 D was found in 50% of patients within this group, whereas 24.1% had a hypermetropic spherical equivalent of ⱖ 1 D. Three patients in this group were not refracted. Genetic Mutations Affecting Photoreceptor Development and Structure: CRX, CRB1. Mutations in the CRX gene were seen in 6 patients with LCA. All 6 patients had heterozygous mutations, suggesting dominant inheritance. All patients had VA worse than 20/200. Visual acuity of CF or worse was present in 3 patients (50%). The median VA for patients with a CRX mutation was 2.1 (5/600), and VA ranged from 10/300 to LP. No patient had NLP in this group. Two patients had keratoconus, and data on the condition of the cornea were not available for 1 patient. One patient had a spherical degree of myopia ⬎ 1 D, and 1 patient had a hypermetropic spherical correction of 3.5 D. Twenty-eight patients had mutations in the CRB1 gene. Mutations in both alleles of the CRB1 gene were known in 17 patients and in 1 allele in 10 patients. Information on the involved alleles was not available in 1 patient. Ten patients (37.1%) in this group with CRB1 had BCVA of 20/200 or better. Visual acuity of CF to NLP was seen in 13 patients (46.4%), including 1 patient with NLP vision (Fig 1). The VA ranged from 20/40⫺2 to NLP. The median VA for this group was 1.6 (⫽10/400). Keratoconus was

Walia et al 䡠 VA in LCA and Early Childhood-Onset RP Table 2. Mutations in Genes Involved in Photoreceptor Development (CRX, CRB1) and Transport Across Cilium (RPGRIP, CEP290, LCA5, RPGRIP1, TULP1) CRB1 CRX Y208X 1 bp del 263 P263 1bp del C G217 1bp del E168 2bp del S249del1tC A158T

RPGRIP1

Allele 1

Allele 2

4bp del at codons 850-851 G1103R C681Y C948Y I205T

—

D1114G

—

R890X Q483X R768X 1107del A

— —

V1211E E1033Q P882S

T745M C948Y 5bp del 143-144 codons Ex 2B C1084T 1360 G⬎A 2843 G⬎A 2816 G⬎A 3394 T⬎C 7bpdelCo612619 (204-207) exon 2C 749del3bp C948Y K801X C1332X Q120X C948Y C948Y C948Y Q362X C948Y R764C V578E 86-87ins2bp

G1103R K801X R764C

DelG618

Allele 1

CEP290

Allele 2 — R890X — splice 1107 del A V1211E E1033Q —

C1084T 1360G⬎A — 2816 G⬎A — C480R 749del3bp C948Y — C1332X Q120X E204 del7aatGAAATAG T745M G850S — C1218F V1336I V578E —

LCA5 Allele 1 P493TfsX1

seen in 7 patients with a CRB1 mutation. Hyperopic spherical equivalence of ⱖ1 D was seen in 67.9% of the patients with a CRB1 mutation. Genetic Mutations Affecting Transport across the Photoreceptor Connecting Cilium: RPGRIP1, CEP290, LCA5. Nine patients had mutations in the RPGRIP1 gene. Seven (77.8%) of the 9 patients had BCVA of worse than 20/400. One patient could not perceive light (Fig 1). The VA ranged from 20/100 to NLP, with a median of 2.6 (equivalent to vision of CF). None of the patients in this group had keratoconus. Six of the 9 patients (66.7%) in this group had a hyperopic spherical equivalence of ⱖ1 D. Mutations in the CEP290 gene were found in 39 patients. The median VA in this group was 2.8 (LP vision), and the VA ranged from 20/50 to NLP. Nine patients in this cohort had keratoconus. Best-corrected visual acuity of CF or worse was seen in 32 patients (82.1%), of whom 8 had NLP (20.5%) (Fig 1). Fifty-nine percent of patients in this group were found to be hypermetropic with a spherical equivalent of ⱖ1 D. There was 1 patient with an LCA5 mutation. Vision in the better eye for this patient was 9/400 at the age of 8 years. This patient had a hyperopic spherical refractive correction of 8.5 D. Table 3 shows the mean VA of patients with LCA in different decades with different gene mutations. A trend for worsening of central vision in progressive decades was seen in patients with RPE65 and CRB1 mutations. This trend was not observed in patients with AIPL1 and CEP290 mutations. The number of patients in each decade in the remaining genetic subtypes was not sufficient to make a meaningful deduction.

Allele 2 P493TfsX1

Allele 1 C998X

Allele 2 C998X

C998X IVS26⫹1655A⬎G C998X C998X

— — L517fsX10 T1938NfsX15

C998X C998X C998X

E1656X G1628X G1890X

C998X 3bpdelIVS34-3 del1bpC IVS26⫹1655A⬎G C998X C998X S570X

T420del — Q1654del2 E1656X Q1628X IVS26⫹1655A⬎G

IVS26⫹1655A⬎G Q1656Term IVS34-3 del1 gC IVS26⫹1655A⬎G

K1575X IVS26⫹1655A⬎G — Thr420 del5acTAAAG

TULP1 Allele1 splice

Allele 2 splice

Early Childhood-Onset Retinitis Pigmentosa Group A total of 27 patients with age of onset of visual symptoms or signs between the ages of 1 and 5 years were included in this category. The distribution according to their genetic mutations is as follows: Genetic Mutations Affecting Phototransduction: AIPL1. One patient was found to have a mutation in the AIPL1 gene. This patient had a vision of 20/200 at the age of 6 years. Keratoconus was not evident in this patient. Genetic Mutations Affecting the Retinoid Cycle: RDH12, RPE65. A total of 8 patients had mutations in the RDH12 gene on both alleles with early childhood-onset RP. The BCVA ranged from 20/30 to CF and the median VA was 0.61 (equivalent to 20/80). In this group, 7 patients (87.5%) had BCVA of 20/200 or better. The mean age of patients with an RDH12 mutation was 18 years. None of the 8 patients had keratoconus on clinical examination. Three patients in this group were hyperopic, with 2 having a spherical equivalence of ⱖ1 D. Mutations in the RPE65 gene were found in 5 patients (mutations in both alleles were known in 4 patients, and information on the involved alleles was not available for 1 patient). The range of BCVA was 20/50 to LP, with a median VA of 0.6 (20/80). The BCVA in 3 patients (60%) was 20/200 or better. None of the patients had NLP or keratoconus. The mean age of patients in this group was 19.6 years. Two patients in this group were myopic, and 1 patient was hypermetropic ⬎1 D, whereas refractive data were not available for 1 patient.

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Figure 1. Comparison of VA data of patients with CEP290, AIPL1, CRB1, RPE65, GUCY2D, and RPGRIP mutations. CF ⫽ counting fingers; HM ⫽ hand motion; LP ⫽ light perception; NLP ⫽ no light perception.

Genetic Mutations Affecting Photoreceptor Development and Structure: CRX, CRB1. The early childhood-onset RP group had 1 patient with a heterozygous CRX mutation. This patient had a BCVA of CF at the age of 18 years. Keratoconus was not evident in this patient. The CRB1 group had 9 patients with a mean age of 26 years. The VA ranged from 20/30 to LP, and median VA was 1.3 (equivalent to 20/400). Visual acuity of 20/200 or better was found in 4 patients (44.4%). Keratoconus was seen in 1 patient. Hyperopic spherical equivalence of ⱖ1 D was found in 8 patients in this group, and data on the refractive status of 1 patient were not available. Genetic Mutations Affecting Transport across the Photoreceptor Connecting Cilium: CEP290, RPGRIP1, TULP1. One patient had a mutation in the CEP290 gene, with a BCVA of 20/40⫹1 at the age of 14 years. The RPGRIP1 mutation was seen in 1 patient. The BCVA for this patient was 20/150 at the age of 30 years. One patient was included in the TULP1 group with a

BCVA of 20/100 at the age of 5 years. None of the 3 patients had keratoconus.

Discussion In the current study, we analyzed the variations in BCVA and the possible correlations with 10 different LCA genotypes. Overall, median VA was better in patients with RDH12, RPE65, and CRB1 mutations in the LCA group.

RDH12 RDH12 encodes a protein that belongs to the subfamily of retinol dehydrogenases and is involved in the conversion of all-trans retinal and 11-cis retinal to the corresponding reti-

Table 3. Comparison of Mean Visual Acuity of Patients with Leber’s Congenital Amaurosis with Different Gene Mutations in Different Decades* Age (yrs)

AIPL1

CEP290

RPE65

GUCY2D

CRX

RPGRIP1

RDH12

CRB1

0–10 11–20 21–30 31–40 41–50 51–60 61–70 71–80

2.27 (6) 2.58 (5) 2.25 (3) 2.44 (2) 2.8 (3) None None None

2.83 (10) 2.2 (13) 2.54 (5) 2.75 (4) 2.47 (4) 0.8 (1) None None

0.78 (17) 0.89 (9) 1.29 (11) 1.91 (9) 2.78 (4) 2.8 (2) 2.8 (1) 2.48 (1)

2.29 (7) 2.8 (1) 2.7 (1) 2.8 (1) None 1.3 (1) None None

1.95 (2) 1.48 (1) 1.6 (1) 2.8 (1) None None 2.8 (1) None

1.53 (4) 2.13 (3) None 2.6 (2) None None None None

0.9 (2) 0.50 (1) 1 (1) None None None None None

1.56 (9) 0.83 (4) 1.15 (5) 2.55 (6) 2.8 (1) 2.8 (1) 2.9 (1) 2.7 (1)

( ) ⫽ number of patients in each group within each decade; LCA ⫽ Leber’s congenital amaurosis; logMAR ⫽ logarithm of the minimal angle of resolution. A logMAR of 1 corresponds to 20/200, whereas 20/20 would correspond to a logMAR value of zero. *Vision is noted in logMAR units.

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Walia et al 䡠 VA in LCA and Early Childhood-Onset RP nols.31 It causes a severe rod-cone dystrophy with agerelated progressive loss of acuity.9,32,33 However, presence of some useful vision9 along with transient improvement in VA in early life33 has been reported. All patients with LCA in the current study with an RDH12 mutation had BCVA ⱖ 20/200, perhaps because, in our cohort, none of the patients were aged more than 30 years and thus may still have had some preserved useful VA. In the early childhood-onset RP group, a median VA of 20/80 was observed. Most patients had a BCVA of ⱖ20/200, except 1 patient with a VA of CF. Similar to the RDH12 LCA group, all patients with early childhood-onset RP were in the first 3 decades of life, except 1 patient with CF vision who was 47 years old at the time of examination.

RPE65 RPE65 encodes the isomerase enzyme involved in conversion of all-trans retinyl ester to 11-cis retinol in the visual cycle.34,35 Variable degrees of VA loss ranging from 20/50 to LP have been noted in patients with mutations in this gene in an earlier study.8 Similar results were obtained in the current study with BCVA ranging from 20/32 to NLP. Other authors have reported that mutations in RPE65 cause profound visual impairment at birth, transient improvement with useful vision persisting up to the second decade, and then further progressive loss of central vision as patients became older.36,37 Some authors were not able to find improvement in VA with RPE65 mutations, but their findings also showed the presence of useful vision in these patients during early age and progressive decline after the second decade.7,38 In the current study, mean BCVA ranging from 20/120 to 20/400 was noted in patients in the first 3 decades. Mean BCVA declined to less than 5/400 in patients more than 40 years of age. Better VA was observed in the early childhood-onset RP group, with a median VA of 20/80.

current study. Similar results have been noted in patients with AIPL1 mutations by other authors in smaller cohorts of patients.8,13,41 Best-corrected visual acuity of 20/200 was noted in the patient with early childhood-onset RP.

GUCY2D GUCY2D is the photoreceptor guanylate cyclase gene required for cGMP synthesis, which is a secondary messenger of the phototransduction cascade that maintains the cGMP gated channels in the open position.44 Mutations in GUCY2D have been shown to cause congenital cone-rod dystrophy with markedly decreased VA in addition to causing LCA.41 Other authors have reported a stable visual course and profound visual loss in patients having a mutation in this gene.8,41,45 Dharmaraj et al7 found VA ranging from 20/200 to LP in their cohort of patients with a GUCY2D mutation. A milder phenotype with a GUCY2D mutation with a juvenile-onset rod-cone phenotype has also been reported.46 The current study also found profound visual loss in patients with LCA with GUCY2D mutations, with more than 90% of patients showing a BCVA of less than 20/200. The median VA for this cohort equaled LP.

CRX The cone-rod homeobox gene is essential for differentiation and maintenance of photoreceptor cells. Mutations in this gene may cause a dominantly inherited form of LCA.47,48 All patients with a CRX mutation in the current cohort had BCVA of worse than 20/200 and a median VA of 5/400. Other authors have also reported notably low levels of BCVA in this patient group.8,41 Stable clinical course with a low VA has been reported by Dharmaraj et al.7 The patient with early childhood-onset RP with a CRX mutation also had profoundly decreased VA of CF.

CRB1

CEP290

Crumbs homolog 1 has been found to be important in maintaining cellular polarity in drosophila.39 A wide variety of VA was noted in patients with mutations in this gene, ranging from 20/40 to NLP. Prior studies have also noted similar variations of VA in patients with LCA with this mutation.8,40 Hanein et al41 reported VA ranging from 1/10 to 2/10 in these patients. A similar variation of VA ranging from 20/30 to LP was observed in the early childhood-onset RP group with CRB1 mutations.

Mutations in CEP290 are currently the most frequently identified cause of LCA.10,15 CEP290 has been shown to localize to the centromeres of diving cells and connecting cilium of the photoreceptors.15 A mutation in this gene leads to rapid reduction in outer segment length and outer nuclear layer thickness.49 The resulting phenotype is characterized by a cone-rod type of visual loss with severe reduction in VA.10 In the current study, BCVA of 39 patients with LCA and a CEP290 mutation was included. Severely reduced VA was observed beginning in the first decade. Best-corrected visual acuity of CF or worse was observed in 82.1% of our patients with LCA and a CEP290 mutation. Similar results were observed by Perrault et al,10 who examined 47 patients with CEP290 mutations and found that most patients had a rigorous and early reduction in VA (⬍1/20). den Hollander et al,15 however, found a variable VA in 4 affected siblings, ranging from LP to 20/80. In comparison with the LCA group, 1 patient in the early childhood-onset RP group had a BCVA of 20/40⫹1.

AIPL1 This gene encodes for aryl hydrocarbon receptor proteinlike 1 and is found exclusively in rod photoreceptors in human adult retina.42 It has a potential role in nuclear transport or chaperone activity, because it appears to function in the farnesylation reaction of ␤ PDE, a critical enzyme in the photoreceptor phototransduction reaction.43 Patients with LCA with this mutation had severely decreased vision at a younger age with a median VA of LP noted in the

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RPGRIP1 Retinitis pigmentosa GTPase regulating protein 1 localizes to the connecting cilium50 and the inner segments of the photoreceptors.51 It binds to RP GTPase regulator to anchor RPGR to the connecting cilium.50 In the current study, patients with LCA with an RPGRIP1 mutation were found to have a median VA of CF, with 77.8% of patients having VA worse than 20/200. Other authors have made similar observations and noted profound visual impairment beginning from early childhood in these patients.8,14 One patient in the early childhood-onset RP group had comparably better VA of 20/150 in the betterseeing eye. A trend toward age-related loss of central vision was observed in patients with either an RPE65 or CRB1 mutation, whereas those with AIPL1 and CEP290 mutations were observed to have stable VA in patients across different decades (Table 1). Other authors have also noted an agerelated decline of VA in patients with RPE65 mutations52,53 and stable severe loss of vision in patients with AIPL1 mutations.13 We recognize that it is conceivable that in isolated instances, those patients with a mutation identified on only 1 allele may have been misclassified. However, the single identified mutation was thought to be disease causing. Cohorts with different ethnic representation may vary in the prevalence of different LCA mutations; thus, the prevalence of LCA gene mutations in our cohort may be different from those cited in other studies.10,12,15 The sample of 196 patients assembled in this multiinstitutional work constitutes a sizeable proportion of molecularly characterized patients with LCA from large retinal degeneration practices within the United States. Phenotypic features shared by each molecular subgroup extend previous observations in smaller groups of patients and helps us overcome the limitations to generalizability posed by rare disorders. In conclusion, this study describes the variations of visual acuities that may be observed in patients with LCA or early childhood-onset RP with varying defined gene mutations. Mutations in RPE65 and CRB1 may be associated with a relatively better VA in early life compared with other gene mutations. It is of considerable scientific and clinical interest that differences exist between the final VA in patients with the various genetic subtypes of LCA. This implies that the pathways to photoreceptor dysfunction and photoreceptor death are not identical among the different types of LCA mutations. We showed that the final VA may be correlated with the LCA genotypes, which is useful for both the clinical prognoses given by the ophthalmologists in case of preparation for schooling and professions, but also may be useful as baseline measures for the upcoming treatment trials. Finally, onset of symptoms after the age of 1 year is also associated with an overall better visual prognosis. Acknowledgment. The authors thank Youjia Shen and Susan Crowe for contributions in preparing clinical and genetic data on patients from their centers.

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Ophthalmology

Volume 117, Number 6, June 2010

Footnotes and Financial Disclosures Originally received: May 14, 2009. Final revision: September 25, 2009. Accepted: September 28, 2009. Available online: January 15, 2010.

9

Departments of Ophthalmology, Pathology and Cell Biology, Columbia University, New York, New York. 10

Manuscript no. 2009-645.

1

Department of Ophthalmology, University of Illinois at Chicago, Chicago, Illinois. 2

Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania. 3

McGill Ocular Genetics Center, Division of Pediatric Ophthalmology, Montreal Children’s Hospital, McGill University Health Centre, Montreal, Quebec, Canada. 4

Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio.

5

Casey Eye Institute, Oregon Health and Science University, Portland, Oregon. 6

Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children and University of Toronto, Ontario, Canada. 7

Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa. 8

Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida.

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Howard Hughes Medical Institute, Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa. This study was not presented as a paper or poster at the Academy meeting. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Supported by funds from the Foundation Fighting Blindness, Owings Mills, Maryland; the Grousbeck Family Foundation, Boston, Massachusetts; the Grant Healthcare Foundation, Lake Forest, Illinois; National Institutes of Health core grant YO 1792; Foundation Fighting Blindness Canada; Fonds de la recherche en santé due Québec, Canadian Institutes of Health Research; and an unrestricted departmental grant from Research to Prevent Blindness. Correspondence: Gerald A. Fishman, MD, Department of Ophthalmology and Visual Sciences (MC 648), Room 3.85, Eye and Ear Infirmary, 1855 West Taylor Street, Chicago, IL 60612-7234. E-mail: [email protected].