Maturation of rod function in preterm infants with and without retinopathy of prematurity.

OBJECTIVES: To establish normal development of rod electroretinograms in preterm infants and to assess the effects of retinopathy of prematurity (ROP). STUDY DESIGN: We measured 88 Naka-Rushton functions from 41 preterm infants at maturities from 30 to 72 weeks postmenstrual age (PMA). Outcomes (log sigma, retinal sensitivity and V(max), retinal responsivity) were compared between control (no ROP), untreated ROP, and treated ROP. RESULTS: In control infants, sensitivity increased by 1.5 log units from 30 to 40 weeks PMA and by a further 0.5 log units by 50 weeks PMA but was 0.5 log units less than in similarly-mature, healthy, term-born infants. Average retinal responsivity increased from 23 microV to 90 microV between 30 and 40 weeks PMA and was 35 muV greater at 40 weeks PMA than in similarly-mature term-born infants. At around 36 weeks PMA, (when onset of ROP peaks), infants with untreated ROP had average retinal sensitivity 0.2 log units lower than control infants; sensitivity was reduced further in infants treated for ROP. Retinal responsiveness did not differ between control subjects and untreated infants with ROP but was greatly reduced in infants treated for ROP. CONCLUSIONS: Maturation of rod sensitivity appears to be slowed by preterm birth whereas maturation of rod responsivity is accelerated. ROP reduces retinal sensitivity, and treated ROP reduces both sensitivity and responsivity.

Retinal dysfunction in patients with chronic Chagas' disease is associated to anti-Trypanosoma cruzi antibodies that cross-react with rhodopsin.

To investigate retinal involvement in chronic Chagas' disease, we performed electroretinography and retinal fluorescein angiography studies in chagasic patients. Our results demonstrated a dissociated electrophysiological response characterized by both an abnormal reduction of the electroretinographic b-wave amplitude and a delayed latency, under the dark-adaptated condition. These alterations are compatible with a selective dysfunction of the rods. Antibodies raised against Trypanosoma cruzi that also interact with beta1-adrenergic receptor blocked light stimulation of cGMP-phosphodiesterase in bovine rod membranes. The specificity from the antibody-rhodopsin interaction was confirmed by Western blot analysis and antigenic competition experiments. Our results suggest an immunomediated rhodopsin blockade. T. cruzi infection probably induces an autoimmune response against rhodopsin in the chronic phase of Chagas' disease through a molecular mimicry mechanism similar to that described previously on cardiac human beta1-adrenergic and M2-cholinergic receptors, all related to the same subfamily of G-protein-coupled receptors.

Avaliaçäo da funçäo macular e da funçäo dos cones em pacientes com retinose pigmentar por meio de: potencial visual evocado por padräo reverso, potencial visual evocado focal, flicker perimetria / Valuation of the remaining macular and cone function in retinitis pigmentosa patients. The electrophysiologycal tests of pattern visual evoked potencial, focal visual evoked potencial, flicker perimetry

Objetivo: Avaliar a funçäo da mácula e a funçäo dos cones em pacientes com retinose pigmentar (RP) por meio dos exames de potencial visual evocado (PVE) por padräo reverso (PVE-P) potencial visual evocado focal (PVE-F) e da flicker perimetria (FP). Método: O PVE-P realizado foi do tipo steady-state, com uma frequência de reversäo dos quadrados de 6 Hz. Foram testados cinco padröes diferentes: 160, 80, 40, 20 e 10 minutos de arco. Para a realizaçäo do PVE-F foi utilizada uma iluminaçäo homogênea que compreendia 4,5§ de ângulo visual do paciente. A intensidade de luz era controlada através de filtros de densidade neutra. A intensidade do estímulo sem nenhum filtro era de 14.290 mL. A FP era realizada em ambiente fotópico, com um estímulo de 2§, cuja frequência de piscamento era reduzida até que o paciente percebesse. Estimulava-se o centro (0§), e os pontos periféricos (5§, 10§, 20§, 30§, 40§, 50§ e 60§, no meridiano horizontal, tanto no sentido nasal como no temporal). Conclusöes: Em pacientes com RP e AV relativamente preservada, a funçäo da mácula e dos cones pôde ser mensurada pelos exames de PVE-P, PVE-F e FP. Houve uma boa correlaçäo positiva entre a AV e os testes de PVE-P, PVE-F e FP. Houve uma boa correlaçäo positiva entre o CV e o PVE-P. A correlaçäo entre o CV e o resultado do PVE-F e da FP foi fraca. A CAFP do PVE-P teve uma conformaçäo achatada. O gráfico da FP teve uma configuraçäo em montanha. Os cones da retina de pacientes com RP e AV relativamente preservada estavam acometidos em toda a extensäo testada, incluindo a mácula, porém o acometimento foi mais marcante nos cones da periferia do que nos cones da retina central. A funçäo visual remanescente na retina de pacientes com RP e AV relativamente preservada pode ser quantificada pelos exames de PVE-P, PVE-F e FP, permitindo que estes exames sejam incorporados à rotina de avaliaçäo e acompanhamento da progressäo da retinose pigmentar...