What exactly are the eye drops used in ptosis assessment pre-op please? (photos)

To simply state it, the drops help assess wether or not muellers muscle resection alone can treat your ptosis or if levator advancement is required. These are the two muscles that help elevate the lid. Your ptosis is likely caused by these muscles not working properly in some form or fashion.  

The stimulate drops make the muscle contract.  We can then assess wether shortening of the muscle will give similar results. It is a quite effective way to assess this issue.

Best of luck.

DrC

It is hard to definitively diagnose a problem from a picture and I would recommend seeing an oculo-plastic surgeon which is an ophthalmologist with a concentration in plastic surgery specifically around the eyelids. That being said, it looks to me that you have what is called ectropion. That being said, it does seem to me that you have ptosis and should be evaluated by an oculo-plastic surgeon as having a blepharoplasty performed when a ptosis repair is needed, will yield poor results.
The eyes drops used are called Phenylephrine. This essentially simulates the muscle that holds your eyelid up, which usually isnt working properly when you have ptosis. If these drop successfully lift your eyelid, the surgeon knows what he should do in order to correct your ptosis.

You most likely have ptosis of the left upper lid, but could have pseudoptosis related to extraocular motility disorder or thyroid dysfunction. An oculoplastic surgeon would be able to assess with eyelid and pupil measurements and make an accurate diagnosis for you. Drops are used to determine the level of a neurological defect if you have Horner's syndrome (cocaine drops) or for myasthenia gravis (edrophonium chloride). Some surgeons use an adrenergic drop to observe a response pre-op (lid elevation) to determine which surgical approach to use - posterior/ conjunctiva-Mueller's if the lid elevates. I recommend an anterior/ skin approach for all ptosis repairs, and therefore, do not perform this test. The anterior approach allows correction of the lid level, lid contour, lid crease, lid fold, and symmetry. For most patients, it is unnecessary to use drops in the assessment of ptosis. Best wishes with your repair.