Refração e seus componentes em anisometropia / Refraction and its components in anisometropia

OBJETIVO: Em anisométropes comparar os valores médios individuais dos componentes oculares de ambos os olhos, correlacionar as diferenças dos componentes com as diferenças de refração; e identificar o menor número de fatores que contenham o mesmo grau de informações expressas no conjunto de variáveis que influenciam a diferença refrativa. MÉTODOS: Realizou-se estudo transversal analítico em população de 77 anisométropes de 2 D ou mais, atendida no ambulatório de Oftalmologia do Hospital Universitário da Faculdade de Medicina Nilton Lins, Manaus. RESULTADOS: Os anisométropes foram submetidos à refração estática objetiva e subjetiva, ceratometria e biometria ultrassônica A-scan. A análise dos dados foi feita por meio dos seguintes modelos estatísticos: análise univariada, multivariada, de regressão múltipla e fatorial. CONCLUSÕES: Não houve diferenças significativas na comparação dos valores médios individuais dos componentes oculares entre os olhos. Houve correlação negativa média entre a diferença refrativa e a diferença de comprimento axial (r= -0,64) (p<0,01) e correlação negativa fraca entre a diferença refrativa e a diferença de poder do cristalino (r= -0,34) (p<0,01). As variáveis analisadas responderam, no seu conjunto, por 78 por cento da variação total para a diferença refrativa. Foram identificados três fatores para a diferença refrativa: fator 1 (refração, comprimento axial); fator 2 (profundidade da câmara anterior, poder da córnea) e fator 3 (poder do cristalino).

PURPOSE: To compare the individual means of ocular components of both eyes in patients with anisometropia; to correlate the differences of the components with refractive differences; and to identify the smallest number of factors that contain the same level of information expressed in the set of variables that influence refractive difference. METHODS: An analytical transversal study was carried out in 77 patients with anisometropia of two or more dioptres seen at the Ophthalmologic Clinic, University Hospital, Nilton Lins Medical School, Manaus. RESULTS: All participants were submitted to ophthalmologic examination which included objective and subjective cycloplegic refractometry, keratometry and ultrasound biometry. Data analysis comprised the following statistical models: univariate, multivariate, multiple and factorial regression analyses. CONCLUSIONS: There were no significant differences in the comparison between the individual means of the ocular components. There was negative correlation between refractive difference and difference of axial length (r= -0.64; p<0.01) and weak negative correlation between refractive difference and crystalline lens power difference (r= -0.34; p<0.01). The analyzed variables reached 78 percent of the total variation of refractive difference. Three factors were identified for refractive differences: a) factor 1 (refraction, axial length); b) factor 2 (anterior chamber depth, cornea power), and c) factor 3 (crystalline lens power).

Pattern Visual Evoked Potential as a Predictor of Occlusion Therapy for Amblyopia

PURPOSE: This study was conducted to investigate the role of the pattern visual evoked potential (pVEP) as a predictor of occlusion therapy for patients with strabismic, anisometropic, and isometropic amblyopia. The secondary aim was to compare the characteristics of pVEP between strabismic and anisometropic amblyopia. METHODS: This retrospective comparative case series included 120 patients who had received occlusion therapy or a glasses prescription for correction of strabismic, anisometropic, and isometropic amblyopia (20 patients had strabismic amblyopia, 41 patients had anisometropic amblyopia, and 59 patients had isometropic amblyopia). For each patient, the value of the P100 latency on pVEP at the time of the initial diagnosis of amblyopia was collected. Subsequently, the P100 latency was compared according to types of amblyopia. Fifty of 120 patients (7 patients with strabismic amblyopia, 21 patients with anisometropic amblyopia, and 22 patients with isometropic amblyopia) who were followed-up for longer than 6 months were divided into two groups based on the value of their P100 latency (Group 1, P100 latency 120 msec or less; Group 2, P100 latency longer than 120 msec.) The amount of visual improvement after occlusion therapy or glasses was compared between two study groups. RESULTS: The mean P100 latency was 119.7+/-25.2 msec in eyes with strabismic amblyopia and 111.9+/-17.8 msec in eyes with non-strabismic (anisometropic or isometropic) amblyopia (p=0.213). In Group 1, the mean visual improvement after occlusion therapy or glasses was 3.69+/-2.14 lines on Dr. Hahn's standard test chart; in Group 2, the mean improvement was 2.27+/-2.21 lines (p=0.023). CONCLUSIONS: The P100 latency on pVEP at the time of initial diagnosis was significantly related to the visual improvement after occlusion therapy or glasses in patients with strabismic, anisometropic, and isometropic amblyopia. Therefore, it was presumed that patients with a delayed P100 latency might have less visual improvement after occlusion therapy or glasses. In addition, there was no apparent difference in P100 latency between patients with strabismic and non-strabismic (anisometropic or isometropic) amblyopia.

Componentes oculares em anisometropia / The ocular components in anisometropia

OBJETIVO: Comparar as correlações dos componentes oculares (comprimento axial, comprimento do segmento anterior, poder médio da córnea, profundidade da câmara vítrea e poder refrativo equivalente) com o erro refrativo total do olho portador da menor e da maior ametropia em anisométropes. MÉTODOS: Foi realizado um "survey" analítico conduzido em população de 68 anisométropes de duas ou mais dioptrias atendida no Ambulatório da Clinica Oftalmológica do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo Os anisométropes foram submetidos à refração estática objetiva e subjetiva, ceratometria e biometria ultra-sônica. RESULTADOS: Não houve diferença significativa entre os valores dos componentes oculares medidos dos olhos portadores da menor e da maior ametropia. Os olhos portadores da menor ametropia apresentaram as mesmas correlações significantes observadas em olhos emétropes, ou seja, correlação da refração com comprimento do segmento anterior e comprimento axial, e correlação do comprimento axial com poder corneano e profundidade da câmara vítrea. Os olhos portadores da maior ametropia apresentaram correlação significante da refração com o comprimento axial e do comprimento axial com a profundidade da câmara vítrea. Ainda em ambos os olhos observou-se correlação significante do poder do cristalino com a profundidade da câmara anterior. CONCLUSÃO: Os olhos portadores da menor ametropia desenvolveram as correlações mais freqüentemente observadas nos olhos emétropes. Os olhos portadores da maior ametropia não desenvolveram as mesmas correlações dos emétropes.

PURPOSE: To asses the correlation between ocular components (axial length, anterior segment length, corneal power, vitreous length and equivalent power of the eye) and refractive error in eyes with higher and lower ametropia of subjects with anisometropia. METHODS: An analytical survey was carried out in 68 patients with anisometropia of two or more diopters, assisted at the Ophthalmological Clinic from "Hospital das Clínicas da Faculdade de Medicina" of São Paulo University. All participants were submitted to ophthalmologic examination which included objective and subjective cycloplegic refratometry, keratometry and ultrasonic biometry. RESULTS: No significant difference between measures of ocular components of the eyes with higher and lower ametropias was observed. The eyes with lower ametropia presented the same significant correlations observed in emmetropic eyes: of refraction with anterior segment length and axial length, and of the axial length with corneal power and vitreous length. The eyes with higher ametropia presented significant correlation of refraction with the axial length and of the axial length with vitreous length. Furthermore, we observed in both eyes, significant correlation of the power of the crystalline lens with the anterior chamber depth. CONCLUSION: The eyes with lower ametropia presented correlations more frequently observed in emmetropia. The eyes with higher ametropia did not present the same correlations observed in emmetropic eyes.

Seqüência de Möbius: resultados a longo prazo, da correção cirúrgica do estrabismo / Mõbius sequence: long-term strabismus surgical outcome

OBJETIVOS: Analisar os resultados cirúrgicos, a longo prazo, em uma série consecutiva de pacientes com a seqüência de Mõbius, submetidos à correção cirúrgica do estrabismo. MÉTODOS: Dez portadores da seqüência de Mõbius atenderam aos critérios de inclusão. Todos apresentaram esotropia no exame pré-operatório maior ou igual a 15 dioptrias prismáticas (DP), variando de 15 a 85. Todos os pacientes demonstraram hipofunção dos músculos retos laterais, seis, apresentaram hipertropia associada maior ou igual que 10 DP e, cinco, anisotropia em A ou em V. Os pacientes foram submetidos de forma consecutiva à cirurgia para a correção do estrabismo em julho de 2002, de acordo com protocolo previamente elaborado. Todos os casos foram reavaliados periodicamente, analisando-se o resultado visual final no segundo ano pós-operatório, quanto a: acuidade visual, desvio ocular, rotações oculares, estética e socialização. RESULTADOS: Os pacientes apresentaram resultado cirúrgico satisfatório final em oito casos, considerando-se um eso ou exo desvio de até 15 DP e uma hipertropia menor que 10 DP. Quatro (40 por cento) pacientes apresentaram correção da anisotropia pré-operatória. Observou-se variação do desvio ocular em posição primária do olhar (entre o 90° dia e o 2° ano pós-operatório) em 9 pacientes (90 por cento), demonstrando que a estabilização da correção cirúrgica do estrabismo requer tempo. CONCLUSÕES: O resultado cirúrgico final mostrou-se bastante satisfatório, elevando a auto-estima dos pacientes e a de seus genitores, facilitando a sua inclusão social.

PURPOSE: To analyze the long-term results in a consecutive series of Mõbius sequence patients, who underwent surgical correction of strabismus. METHODS: Ten patients with Mõbius sequence fulfilled the inclusion criteria of this study. All patients presented esotropia at the preoperative examination, above or equal to 15 prismatic diopters (DP) varying from 15 to 85. All patients presented lateral rectus muscles severe underaction, six presented hipertropia above or equal 10 DP associated with esodeviation, and five presented anisotropia in A or in V. The patients were operated upon protocol, in a consecutive way, in July 2002. Patients were reexamined periodically, and at 2nd postoperative year as for: the visual acuity; deviation measurements; ocular rotations; cosmetic aspect and socialization. RESULTS: The patients presented satisfactory surgical results in eight cases, considering an eso or exodeviation up to 15 DP and a hipertropia lower than 10 DP. Four (40 percent) patients presented correction of the preoperative anisotropia. Variation of ocular deviation in the primary position (from the 90th day to the 2nd postoperative year was observed) in 9 patients (90 percent), demonstrating that strabismus surgical stabilization needs time. CONCLUSIONS: The surgical results were considered satisfactory, improving patient self-esteem and the parent satisfaction, making the social inclusion easier.

Evaluation of relationship of ocular parameters and depth of anisometropic amblyopia with the degree of anisometropia.

PURPOSE: (1) To find out the relationship of the depth of amblyopia with the degree of anisometropia, in untreated cases of anisometropic amblyopia without strabismus, for both myopic and hypermetropic individuals. (2) To find out the relationship between various ocular parameters, such as axial length and corneal curvature, with the degree of anisometropia between the two eyes. MATERIALS AND METHODS: This prospective study was conducted between January 2001 and March 2003, in 85 cases of untreated anisometropic amblyopia, who attended the author's out patient department. All these patients were subjected to a meticulous ocular examination, with special emphasis on (1) refraction under cycloplegia (2) best corrected visual acuity (3) measurement of axial length by A Scan (4) keratometry . The depth of amblyopia was calculated in two ways: (1) By finding out decimal visual acuity for each eye and subsequently calculating their difference. (2) By converting the Snellen acuity into Log MAR units, which was calculated by finding the Logarithm of the reciprocal of the decimal visual acuity for the two eyes, followed by calculating the difference between the two. The difference in refraction between the two eyes as a measure of anisometropia, was determined by the difference in spherical equivalent between the refraction for each eye. RESULTS: On comparing hypermetropic and myopic cases, a significant correlation was found between depth of amblyopia and the degree of anisometropia, in both myopic and hypermetropic patients. The correlation coefficients were however, found to be greater for hypermetropic than myopic individuals. It was observed that the difference between the axial length of the two eyes contributed to a major part of anisometropia, more so in myopic cases. CONCLUSIONS: The depth of amblyopia correlates with the degree of anisometropia in previously untreated anisometropic amblyopia patients.

Prevalence of amblyopia among schoolboys in Abha city, Asir region, Saudi Arabia

The aim of this study is to estimate the prevalence of amblyopia among schoolboys in Abha City and to examine its relations with anisometropia and strabismus. A total of 971 male school children were selected randomly from the elementary schools for male in the city. Using the criterion of a visual acuity of 6/9 or worse, with no obvious structural disease of the eye, to define amblyopia, 18 cases have been found to have the condition, with a prevalence of 1.85%. Those cases consisted of 7[47%] with anisometropic amblyopia and strabismus, and 2[13%] with deprivation amblyopia. Amblyopia showed a prevalence equal to 27% and 31% among children with anisometropia and those with strabisimus respectively. An effective screening program for early detection of amblyopia through the well baby clinics is recommended

"A retrospective cohort study for prognostic significance of visual acuity for near over that for distance in anisometropic amblyopia.".

A cohort of 50 anisometropic amblyopes, between the ages of 2.5 to 10 years, was studied retrospectively to assess the prognostic significance of visual acuity for near over that for distance. There is ample evidence in the literature for a significantly lower accommodative response in the anisometropic amblyopic eye. It has been proposed that the efferent accommodative dysfunction may be a fundamental and causative factor in anisometropic amblyopia. A reduced visual acuity for near over that for distance was found in 17 [34%] patients and in 11 out of these the near vision improved after an addition of +3.0D sph. When a reduced visual acuity for near, was obtained it was difficult to determine whether the visual afferent system (due to insufficient visual input), or the accommodation efferent mechanism was responsible. However an improvement in corrected near vision by addition of +3.0D sph. suggested an accommodative dysfunction. In patients with reduced visual acuity for near over that for distance, not only was the final visual outcome poor but also the onset of visual improvement in response to amblyopia therapy was delayed.