For the past 3 months, a 53-year-old woman has had decreasing vision in her right eye. Today she has experienced sudden loss of vision on the right, as though a window-shade had been pulled down. Funduscopic examination reveals a 13 mm choroidal mass on the right. The left eye appears normal.
The cross section of the enucleated eye reveals a uveal (choroidal) mass that is darkly pigmented. Microscopically, there are polygonal cells with enlarged nuclei, prominent nucleoli, and cytoplasm with brown granules. The Fontana-Masson stain is positive, indicating that the granules are melanin pigment.
She is enrolled in a study to determine outcomes of therapy. The study shows that, over the past year, there were 25 persons in a population of 2,000,000 people for whom medical records were available for review, who had this disease. During that time (one year) 5 of the affected persons died of their disease, while 7,000 persons died in the entire study population.
What is the diagnosis?
What sudden complication did she have?
A retinal detachment occurred. The choroidal mass can lift off the overlying retina, leading to sudden loss of vision in part or all of a visual field.
What is the case fatality rate for her disease? What is the mortality rate for the population as a whole in the study?
A rate is the number of events per unit of population over a particular time span. The case fatality rate is the number of persons in a study with a particular disease who died during a specified time period divided by the number of persons with the disease in the study. Thus, the case fatality rate for ocular melanoma in this study is 5/25, or 0.20, or 200 per 1000.
The mortality rate is the number of persons dying during a specified time period divided by the number of individuals in the population during the specified time period. Thus, the mortality rate for the whole population in this study is 7,000/2,000,000, or 0.0035, or 3.5 per 1000.