Retinitis Pigmentosa and Allied Disorders

Caracterización fenotípica de la retinitis pigmentaria asociada a sordera

Introducción.

El síndrome de Usher es una alteración genética caracterizada por la asociación de retinitis pigmentaria y sordera. Sin embargo, hay casos con familias en las cuales, a pesar de presentarse dicha asociación, no se puede diagnosticar un síndrome de Usher ni ninguno otro.

Objetivo.

Reevaluar fenotípicamente a 103 familias con diagnóstico previo de posible síndrome de Usher o retinitis pigmentaria asociada con sordera.

Materiales y métodos.

Se revisaron las historias clínicas de 103 familias con un posible diagnóstico clínico de síndrome de Usher o retinitis pigmentaria asociada con sordera. Se seleccionaron las familias cuyo diagnóstico clínico no correspondía a un síndrome de Usher típico. Los afectados fueron valorados oftalmológica y audiológicamente. Se analizaron variables demográficas y clínicas.

Resultados.

Se reevaluaron 14 familias cuyo diagnóstico clínico no correspondía al de síndrome de Usher. De las familias con diagnóstico inicial de síndrome de Usher típico, el 13,6 % recibieron uno posterior de “retinitis pigmentaria asociada con sordera” de “otro síntoma ocular asociado con hipoacusia’,’ o en forma aislada en una misma familia, de “retinitis pigmentaria” o “hipoacusia’.’

Conclusiones.

Es fundamental el estudio familiar en los casos en que la clínica no concuerda con el diagnóstico de síndrome de Usher típico. En los pacientes con retinitis pigmentaria asociada con sordera, el diagnóstico clínico acertado permite enfocar los análisis moleculares y, así, establecer un diagnóstico diferencial. Es necesario elaborar guías de nomenclatura en los casos con estos hallazgos atípicos para orientar a médicos e investigadores en cuanto a su correcto manejo.

Cone photoreceptor dysfunction in retinitis pigmentosa revealed by optoretinography

Many blinding diseases afflict photoreceptors, specialized cells in the retina that capture and transduce light to initiate vision. Biomarkers that are sensitive to photoreceptor health are crucial for early detection and effective treatment monitoring of these diseases yet remain elusive. Here, we develop an optical biomarker, based on optoretinographic photoreceptor responses to light stimulation, that reflects the degree of dysfunction of individual cone photoreceptors in patients with retinitis pigmentosa (RP), the most common inherited retinal degenerative disease. Our results show that this biomarker may be beneficial for assessing the functionality of remaining retinal cells in RP patients and for assessing efficacy of treatments such as gene therapy and stem cell transplantation for RP and other diseases afflicting photoreceptors.

Retinitis pigmentosa (RP) is the most common group of inherited retinal degenerative diseases, whose most debilitating phase is cone photoreceptor death. Perimetric and electroretinographic methods are the gold standards for diagnosing and monitoring RP and assessing cone function. However, these methods lack the spatial resolution and sensitivity to assess disease progression at the level of individual photoreceptor cells, where the disease originates and whose degradation causes vision loss. High-resolution retinal imaging methods permit visualization of human cone cells in vivo but have only recently achieved sufficient sensitivity to observe their function as manifested in the cone optoretinogram. By imaging with phase-sensitive adaptive optics optical coherence tomography, we identify a biomarker in the cone optoretinogram that characterizes individual cone dysfunction by stimulating cone cells with flashes of light and measuring nanometer-scale changes in their outer segments. We find that cone optoretinographic responses decrease with increasing RP severity and that even in areas where cone density appears normal, cones can respond differently than those in controls. Unexpectedly, in the most severely diseased patches examined, we find isolated cones that respond normally. Short-wavelength–sensitive cones are found to be more vulnerable to RP than medium- and long-wavelength–sensitive cones. We find that decreases in cone response and cone outer-segment length arise earlier in RP than changes in cone density but that decreases in response and length are not necessarily correlated within single cones.

Retinitis pigmentosa in Onitsha, Nigeria

Background:

Retinitis pigmentosa describes a heterogenous group of progressive hereditary degeneration of the photoreceptor-retinal pigment epithelium complex with varying clinical manifestations. Although studies on the epidemiology of blindness and visual impairment in Nigeria have documented the contribution of retinitis pigmentosa, detailed study of the prevalence, incidence, and pattern of retinitis pigmentosa in Nigeria are few.

Objectives:

The aim of this study was to describe the relative frequency rate and pattern of retinitis pigmentosa among new patients at the Guinness Eye Center Onitsha Nigeria.

Materials and Methods:

Case files of new patients with clinical features of retinitis pigmentosa seen over a 6-year period were reviewed. Information on age, sex, and associated clinical features were extracted into a standard proforma and analyzed.

Results:

Thirty-seven (0.6%) of 5876 new patients had retinitis pigmentosa. There were 25 (67.6%) males and 12 (32.4%) females with an age range of 4–76 years; the median age was 33 years. Family history suggested autosomal dominant inheritance in 15 (40.6%) patients, autosomal recessive inheritance 4 (10.8%), X-linked inheritance 9 (24.3%), and 9 (24.3%) sporadic. Six (16.2%) patients were blind (acuity <3/60) and 22 (59.5%) patients had visual impairment (acuity <6/18). Eight (21.6%) patients had coexistent deafness (syndromic retinitis pigmentosa) including two (5.4%) cases of Usher syndrome.

Conclusions:

The relative frequency rate of retinitis pigmentosa among new patients in our hospital is low but the associated visual and otologic incapacitation are enormous. A prospective study incorporating molecular genetics would more exactly determine the inheritance pattern and the common genes of retinitis pigmentosa in Nigerians.

Leber's Congenital Amaurosis and Gene Therapy

Retinal blindness is an important cause of pediatric visual loss. Leber's congenital amaurosis (LCA) is one of these causes, often wrongly included in the spectrum of retinitis pigmentosa. The disease has become the center of research after initial reports of success in management with gene therapy. This review discusses in brief the clinical presentation and investigative modalities used in LCA. Further, the road to gene discovery and details of currently applied gene therapy are presented. LCA is one of the first successfully managed human diseases and offers an entirely new dimension in ocular therapeutics.