Helen A. Mintz-Hittner

A Range of Clinical Phenotypes Associated with Mutations in CRX, a Photoreceptor Transcription-Factor Gene

Mutations in the retinal-expressed gene CRX (cone-rod homeobox gene) have been associated with dominant cone-rod dystrophy and with de novo Leber congenital amaurosis. However, CRX is a transcription factor for several retinal genes, including the opsins and the gene for interphotoreceptor retinoid binding protein. Because loss of CRX function could alter the expression of a number of other retinal proteins, we screened for mutations in the CRX gene in probands with a range of degenerative retinal diseases. Of the 294 unrelated individuals screened, we identified four CRX mutations in families with clinical diagnoses of autosomal dominant cone-rod dystrophy, late-onset dominant retinitis pigmentosa, or dominant congenital Leber amaurosis (early-onset retinitis pigmentosa), and we identified four additional benign sequence variants. These findings imply that CRX mutations may be associated with a wide range of clinical phenotypes, including congenital retinal dystrophy (Leber) and progressive diseases such as cone-rod dystrophy or retinitis pigmentosa, with a wide range of onset.

Prevalence of mutations causing retinitis pigmentosa and other inherited retinopathies

Inherited retinopathies are a genetically and phenotypically heterogeneous group of diseases affecting approximately one in 2000 individuals worldwide. For the past 10 years, the Laboratory for Molecular Diagnosis of Inherited Eye Diseases (LMDIED) at the University of Texas‐Houston Health Science Center has screened subjects ascertained in the United States and Canada for mutations in genes causing dominant and recessive autosomal retinopathies. A combination of single strand conformational analysis (SSCA) and direct sequencing of five genes (rhodopsin, peripherin/RDS, RP1, CRX, and AIPL1) identified the disease‐causing mutation in approximately one‐third of subjects with autosomal dominant retinitis pigmentosa (adRP) or with autosomal dominant cone‐rod dystrophy (adCORD). In addition, the causative mutation was identified in 15% of subjects with Leber congenital amaurosis (LCA). Overall, we report identification of the causative mutation in 105 of 506 (21%) of unrelated subjects (probands) tested; we report five previously unreported mutations in rhodopsin, two in peripherin/RDS, and one previously unreported mutation in the cone‐rod homeobox gene, CRX. Based on this large survey, the prevalence of disease‐causing mutations in each of these genes within specific disease categories is estimated. These data are useful in estimating the frequency of specific mutations and in selecting individuals and families for mutation‐specific studies. Hum Mutat 17:42–51, 2001.

Intravitreous Bevacizumab as Anti–Vascular Endothelial Growth Factor Therapy for Retinopathy of Prematurity: A Morphologic Study

O verexpression of vascular endothelial growth factor (VEGF) appears important in the pathogenesis of retinopathy of prematurity (ROP). Bevacizumab (Avastin; Genentech, Inc, South San Francisco, California) is a recombinant humanized monoclonal IgG1 antibody. It binds to and inhibits the biological activity of human VEGF. It has been estimated that more than 10 000 patients worldwide have been treated with intravitreous bevacizumab. We report results of a study in postmortem eyes with intravitreous bevacizumab treatment for zone 1, stage 2 ROP in an extremely low-birth-weight infant.

Refractive Outcomes Following Bevacizumab Monotherapy Compared With Conventional Laser Treatment A Randomized Clinical Trial

IMPORTANCE Children born prematurely who develop retinopathy of prematurity (ROP) often develop myopia, and those who require laser treatment may develop very high myopia, which has considerable clinical consequences. OBJECTIVE To report refractive outcomes in preterm infants who developed ROP in zone I or zone II posterior as stage 3+ ROP or aggressive posterior ROP (APROP). DESIGN, SETTING, AND PARTICIPANTS All infants received intravitreal bevacizumab or laser therapy in a prospective, stratified, randomized, controlled, masked, multicenter clinical trial, Bevacizumab Eliminates the Angiogenic Threat for ROP (BEAT-ROP). Children who received intravitreal bevacizumab or laser in the BEAT-ROP clinical trial, with treatment randomized by infant, underwent cycloplegic retinoscopic refraction at a mean age of 2½ years. Fifteen centers with both pediatric and vitreoretinal ophthalmologists participating in level 3 neonatal intensive care units in academic centers with institutional review board approval were included in the trial. Of the originally enrolled 150 infants (300 eyes) in the BEAT-ROP clinical trial, 13 infants (26 eyes) died (6 received intravitreal bevacizumab; 7 received laser) and 19 eyes had intraocular surgery (6 infants bilaterally). Thus, 45 eyes (19 infants bilaterally) were excluded, leaving 131 infants (255 eyes, including 21 eyes that received a successful second treatment for recurrence). INTERVENTIONS Follow-up of the BEAT-ROP cohort. MAIN OUTCOMES AND MEASURES Spherical equivalent refractive outcomes and their distribution by ROP zone and treatment. RESULTS Refractions were available for 109 of 131 eligible infants (83.2%) and 211 of 255 eyes (82.7%). Mean (SD) spherical equivalent refractions were as follows: zone I, -1.51 (3.42) diopters (D) in 52 eyes that received intravitreal bevacizumab and -8.44 (7.57) D in 35 eyes that received laser treatment (P < .001); and zone II posterior, -0.58 (2.53) D in 58 eyes that received intravitreal bevacizumab and -5.83 (5.87) D in 66 eyes that received laser treatment (P < .001). Very high myopia (≥-8.00 D) occurred in zone I in 2 of 52 (3.8%) eyes that received intravitreal bevacizumab and in 18 of 35 (51.4%) eyes that received laser treatment (P < .001). Very high myopia occurred in zone II posterior in 1 of 58 (1.7%) eyes that received intravitreal bevacizumab and in 24 of 66 (36.4%) eyes that received laser treatment (P < .001). CONCLUSIONS AND RELEVANCE More very high myopia was found in eyes that received laser treatment than in eyes that received intravitreal bevacizumab. This difference is possibly related to anterior segment development that is present with intravitreal bevacizumab but minimal or absent following laser treatment. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00622726.

Recessive mutations in TSPAN12 cause retinal dysplasia and severe familial exudative vitreoretinopathy (FEVR).

PURPOSE Familial exudative vitreoretinopathy (FEVR) is an inherited disorder that disrupts the development of the retinal vasculature and can result in blindness. FEVR is genetically heterogeneous and mutations in four genes, NDP, FZD4, LRP5, and TSPAN12, encoding components of a novel ligand-receptor complex that activates the Norrin-β-catenin signaling pathway, account for approximately 50% of cases. We recently identified mutations in TSPAN12 as a cause of dominant FEVR. The purpose of this study was to identify recessive TSPAN12 mutations in FEVR patients. METHODS Mutation screening was performed by directly sequencing PCR products generated from genomic DNA with primers designed to amplify the coding sequence of TSPAN12. Splicing defects were verified by reverse transcriptase PCR of leukocyte cDNA. RESULTS TSPAN12 screening in a large dominant FEVR family unexpectedly led to the identification of homozygous mutations in severely affected family members, whereas mildly affected family members were heterozygous. Further screening in a cohort of 10 retinal dysplasia/severe FEVR patients identified an additional three cases with recessive TSPAN12 mutations. In all examined cases, single mutation carriers were mildly affected compared to patients harboring two TSPAN12 mutations. CONCLUSIONS We report for the first time recessive mutations in TSPAN12 and describe the first genetic cause for the clinical variation seen in FEVR families. Our data raise the possibility that patients with severe FEVR actually may harbor two mutant alleles, derived either from the same gene or potentially from other genes encoding components of the Norrin-β-catenin signaling pathway.

Laser in situ keratomileusis for treated anisometropic amblyopia in awake, autofixating pediatric and adolescent patients.

Purpose: To establish the safety and efficacy of laser in situ keratomileusis (LASIK) in pediatric and adolescent patients with anisometropic amblyopia who completed amblyopia therapy and had a visual acuity of 20/30 or better bilaterally. Setting: Department of Ophthalmology and Visual Science, University of Texas‐Houston Medical School, Houston, Texas, USA. Methods: From August 2000 to March 2002, LASIK was performed in 21 eyes of 19 consecutive patients meeting eligibility requirements. The procedure was performed with the Summit Autonomous LADARVision® 4000 excimer laser (Alcon Laboratories, Inc.) in the amblyopic eye for the correction of anisometropia or in both eyes. All patients were awake and autofixating during the procedure. Results: The mean patient age was 13.14 years (range 8 to 19 years). Seventeen patients were treated in the amblyopic eye only to correct anisometropia; treatment was performed in both eyes of 2 patients who were older than 18 years. Patients were followed for a mean of 18.0 months (range 8.6 to 26.5 months). Anisometropia was greater than 2.00 diopters (D) in all cases (mean 4.43 D, range 13.25 to 2.25 D). The percentage deviation from the attempted correction in the myopic group was 4.0% ± 4.0% (SD) (range 2.0% to 10.0%) and 38.0% ± 13.0% (range 5.0% to 58.0%) in the hyperopic group. Anisometropia decreased uniformly to less than 2.00 D in all patients (mean 1.52 D). The percentage of patients with stereo acuity increased from 63.0% preoperatively to 84.0% postoperatively. Conclusions: Laser in situ keratomileusis safely and effectively reduced anisometropia in these patients. If stereo acuity is not possible preoperatively, it may be obtained postoperatively.

Treatment of retinopathy of prematurity with vascular endothelial growth factor inhibitors

ROP remains a major cause of childhood blindness worldwide. The smallest, sickest infants develop the most severe forms of zone 1 ROP. Such eyes may not be successfully treated by near confluent laser to the avascular retina (current standard of care). With an understanding of ROP pathogenesis, vascular endothelial growth factor inhibitors (anti-VEGF) are being given only when VEGF is elevated in retina and vitreous. Careful screening allows proper timing of administration. Ideal dose (perhaps different for mild and severe cases) and drug (interrupting only pathologic neovascularization and not normal angiogenesis) remain unproven. The author discusses controversial use of anti-VEGF with documented efficacy, observed local complications, and potential systemic toxicities (none observed in six years) to allow retention of vision for severe zone 1 ROP. The benefits have been demonstrated, however, local and systemic risks in these developing premature infants must be carefully studied (both short and long term).

Laser in situ keratomileusis for high hyperopia in awake, autofixating pediatric and adolescent patients with fully or partially accommodative esotropia.

Purpose: To establish the safety and efficacy of laser in situ keratomileusis (LASIK) in pediatric and adolescent patients with bilateral visual acuity of 20/30 or better and accommodative or partially accommodative esotropia. Setting: Department of Ophthalmology and Visual Science, University of Texas‐Houston Medical School, Houston, Texas, USA. Methods: The study comprised 30 eyes of 15 consecutive patients with accommodative or partially accommodative esotropia who met eligibility requirements and had bilateral LASIK using the Alcon Summit Autonomous LADARVision® excimer laser to correct a refractive error after January 2001. All patients were awake and autofixating during the procedure. Results: The mean age of the patients was 13.9 years (range 9.1 to 18.8 years) and the mean refractive error, +5.35 diopters (D) (range +3.75 to +8.50 D) with anisometropia of 2.0 D or less. The mean follow‐up was 15.7 months (range 9.5 to 22.5 months). No intraoperative complications were encountered. The percentage of undercorrection {100% − [(treatment achieved/treatment attempted) × 100%]} [mean 34% ± 17% (SD), coefficient of variation (SD/mean) 0.50, range 5% to 58%] was higher than expected. Seven patients (47%) required enhancement due to undercorrection of hyperopia with diplopia (6 patients) or astigmatism with decreased visual acuity (1 patient). In this small series, no patient lost best corrected visual acuity or stereo acuity. Conclusion: Laser in situ keratomileusis can safely and effectively reduce refractive error in this group of patients; however, patient selection is extremely critical and enhancement was required in almost half the patients.

Intravitreal pegaptanib as adjunctive treatment for stage 3+ ROP shown to be effective in a prospective, randomized, controlled multicenter clinical trial

Purpose Both intravitreal pegaptanib with laser therapy and intravitreal bevacizumab monotherapy have been found to be more efficacious than laser therapy alone in prospective, randomized, controlled clinical trials. Results The use of pegaptanib with laser therapy was efficacious in 91.2% compared with 69.0% in controls. The use of bevacizumab monotherapy was efficacious in 95.7% compared with 78.1% in controls. Conclusions The use of anti–vascular endothelial growth factor therapy for retinopathy of prematurity has been shown to be efficacious, without toxicity reported to date; however, the best drug and dose which allows greatest efficacy with fewest recurrences and without toxicity must be determined.

Five Novel RPGR Mutations in Families with X- Linked Retinitis Pigmentosa

X‐linked forms of retinitis pigmentosa (XLRP) are among the most severe because of their early onset, often leading to significant visual impairment before the fourth decade. RP3, genetically localized at Xp21.1, accounts for 70% of XLRP in different populations. The RPGR (Retinitis Pigmentosa GTPase Regulator) gene that was isolated from the RP3 region is mutated in 20% of North American families with XLRP. From mutation analysis of 27 independent XLRP families, we have identified five novel RPGR mutations in 5 of the families (160delA, 789 A>T, IVS8+1 G>C, 1147insT and 1366 G>A). One of these mutations was detected in a family from Chile. Hum Mutat 17:151, 2001.