## Point Prevalence over 5 years when only given data for 1 year

Hi all,

I'm abit confused about a tricky sort of Prevalence calculation.

So here's my problem-

Sample of 500 people. In 1 year 5 participants will develop incurable blindness.
Assumptions - No blind people in population to begin with and perfectly even occurence of blindness throughout the study year.

Calculate - Incidence? Prevalence after 1 year? Point Prevalence after 5 years?

5/500 -> incidence & prevalence both= 1% in this population in this year

So Now - If i need to calculate the point prevalence @ the end of 5 years (without any further info) of this 'exact' cohorts blindness is it simply 25/500 = 5% prevalence
OR
a bit more complicated & using "incidence" rate of 1% to predict future numbers

New Cases- @ 1% incidence per year
5/500 1st year
4.95/495 2nd year
4.9/490.05 3rd yr
4.85/485.15 4th yr
4.8/480.3 5th year

5+4.95+4.9+4.85+4.8
Therefore is the Prevalence 24.5/500 or 4.9% at the end of the 5years?

Apologies if this seems a tad simple it's just doing my head in.

Cheers in advance for any guidance