Refractive error assessment: influence of different optical elements and current limits of biometric techniques.

PURPOSE: To identify and quantify sources of error on refractive assessment using exact ray tracing. METHODS: The Liou-Brennan eye model was used as a starting point and its parameters were varied individually within a physiological range. The contribution of each parameter to refractive error was assessed using linear regression curve fits and Gaussian error propagation analysis. A MonteCarlo analysis quantified the limits of refractive assessment given by current biometric measurements. RESULTS: Vitreous and aqueous refractive indices are the elements that influence refractive error the most, with a 1% change of each parameter contributing to a refractive error variation of +1.60 and -1.30 diopters (D), respectively. In the phakic eye, axial length measurements taken by ultrasound (vitreous chamber depth, lens thickness, and anterior chamber depth [ACD]) were the most sensitive to biometric errors, with a contribution to the refractive error of 62.7%, 14.2%, and 10.7%, respectively. In the pseudophakic eye, vitreous chamber depth showed the highest contribution at 53.7%, followed by postoperative ACD at 35.7%. When optic measurements were considered, postoperative ACD was the most important contributor, followed by anterior corneal surface and its asphericity. A MonteCarlo simulation showed that current limits of refractive assessment are 0.26 and 0.28 D for the phakic and pseudophakic eye, respectively. CONCLUSIONS: The most relevant optical elements either do not have available measurement instruments or the existing instruments still need to improve their accuracy. Ray tracing can be used as an optical assessment technique, and may be the correct path for future personalized refractive assessment.

Avaliação genética e oftalmológica de pacientes com síndrome de Stickler tipo II / Genetic and ophthalmological assessment of patients with type II Stickler syndrome

OBJETIVOS: Diagnosticar, avaliar e descrever os achados clínico-genéticos e oftalmológicos de pacientes com síndrome de Stickler tipo II de uma mesma família. MÉTODOS: Todos os pacientes com alterações oftalmológicas foram submetidos à radiografia de mãos e punhos para idade óssea e posteriormente analisados pelo exame clínico-genético. O diagnóstico de síndrome de Stickler foi dado mediante análise clínica e correlação com o perfil metacarpofalangeano visualizado na radiografia. RESULTADOS: Síndrome de Stickler tipo II foi comprovada em 11 pacientes. Os achados oculares mais importantes foram: alta miopia (80 por cento), subluxação do cristalino (70 por cento), exotropia (50 por cento) e anomalias vítreo-retinianas (80 por cento) incluindo vazio vítreo (50 por cento). O exame clínico-genético revelou que 30 por cento dos pacientes apresentavam micrognatia, 50 por cento hipoacusia, 40 por cento depressão nasal e 60 por cento palato alto. Hipermotilidade articular e dedos longos foram demonstrados em 7 casos (70 por cento) e artropatia esteve presente em 3 pacientes (30 por cento dos casos). CONCLUSÕES: O diagnóstico da síndrome de Stickler é difícil devido à variabilidade fenotípica e a existência de outras síndromes genéticas com características semelhantes. As radiografias de mão e punho são de particular importância no diagnóstico desta síndrome.

PURPOSE: To diagnose, evaluate and describe the clinical, genetic and ophthalmic characteristics of a family with type II Stickler syndrome. METHODS: X-rays for bone age, clinical and genetic evaluation were performed in all patients with ocular alterations. The Stickler syndrome diagnosis was established after correlating these examinations. RESULTS: Type II Stickler syndrome was found in 11 patients. The most important ocular findings were: high myopia (80 percent), lens subluxation (70 percent), exotropia (50 percent) and vitreoretinal abnormalities (80 percent) including vitreous cavity (50 percent). The clinical genetic examination disclosed that 30 percent of the patients had micrognathia, 50 percent hearing loss, 40 percent nasal depression and 60 percent high palate. Seven cases had articular hypermotility and long fingers and arthropathy was present in 3 cases. CONCLUSION: Diagnosis of the Stickler syndrome is difficult due to its phenotypic variability and the existence of other genetic syndromes with similar characteristics. Hand and wrist radiographs are of particular importance in the diagnosis of this syndrome.

[Genetic and ophthalmological assessment of patients with type II Stickler syndrome]. / Avaliação genética e oftalmológica de pacientes com síndrome de Stickler tipo II.

PURPOSE: To diagnose, evaluate and describe the clinical, genetic and ophthalmic characteristics of a family with type II Stickler syndrome. METHODS: X-rays for bone age, clinical and genetic evaluation were performed in all patients with ocular alterations. The Stickler syndrome diagnosis was established after correlating these examinations. RESULTS: Type II Stickler syndrome was found in 11 patients. The most important ocular findings were: high myopia (80%), lens subluxation (70%), exotropia (50%) and vitreoretinal abnormalities (80%) including vitreous cavity (50%). The clinical genetic examination disclosed that 30% of the patients had micrognathia, 50% hearing loss, 40% nasal depression and 60% high palate. Seven cases had articular hypermotility and long fingers and arthropathy was present in 3 cases. CONCLUSION: Diagnosis of the Stickler syndrome is difficult due to its phenotypic variability and the existence of other genetic syndromes with similar characteristics. Hand and wrist radiographs are of particular importance in the diagnosis of this syndrome.