The College of Optometrists

What is the significance (if any) of the near point of convergence if the objective NPC is greater than the subjective, or subjective is greater than objective?

(By objective I mean when the practioner sees an eye drift out)

Also..

I saw a Coloboma of the retina today, and only knew what it was from the previous notes, it got me wondering what is the differential diagnosis of coloboma, anything I should rule out first before assuming it is a Coloboma. Any instances which would warrant a referral?

Thanks in advance..

Hi entropY

a) if you see the convergence break before the patient reports it. It would mean to me that the patient has some degree of suppression and you could use this fact as a basis of exercise if you wanted too.

However, if the patient reports increasing diplopia as you push up and YOU see good convergence.

Then, to me, it may well mean fixation disparity or in-attention. A vertical phoria can also cause this, as can anisometropia or ammetropia.

The snag with a simple push up test for convergence is that it is not very sensitive to minor miss targeting of the object. It is also so simple - most people can do it although they may well have a problem with their convergence, which shows up after a few push ups.

Coloboma (choroidal)

-- after you have seen one - then its pretty obvious, as to what it is. As it is congenital and benign - there would be no referal. If the vision was very affected as if the macula was implicated and split, or the disk was very small (hypoplastic or hypoplasia of the disk) and the preson was a small child then, perhaps routine referal for second opinion may be in order.

- hope it helps - steve

-just a further point - you know coloboma is benign and not something else 'cos there is an absence of cells in the vitreous, there are no retinal holes or degeneration, and there is no sign of ret. splitting.

You know its a coloboma by its position and appearance, and lack of any signs of activity. Well done to spot it - interesting thing to look at. Isn't the human eye amazing!

You will get field loss in the area of coloboma, of course; and probably see an afferent pupil defect.