If I can’t tolerate it, what are the safe alternatives to IV sedation?

The short version: the evidence here does not test "no IV sedation" against IV sedation for cataract surgery. It tests topical-only anesthesia, and it shows that works well for most people.

The studies you got back are a mixed bag. One large study of 716 patients found that a simple office test predicted who could tolerate surgery under topical anesthesia alone with 98.9% success [6]. Only 7 out of 621 patients who passed the test needed to convert to a block or general anesthesia during surgery [6]. Complication rates were the same between the topical and block groups [6]. That is the strongest piece of evidence here.

For pain, topical drops alone produce very low scores. In a study of 117 patients, the average pain score was 0.3 out of 10 under topical anesthesia, and no patient needed supplemental anesthesia [3]. Another study found that adding a preoperative NSAID drop (nepafenac) to topical anesthesia cut pain scores in half, from about 4 to 2 on a 10-point scale [4]. A third study compared three different topical anesthetics and found that levobupivacaine and ropivacaine worked better than lidocaine [5].

The main risk under topical-only is a blood pressure spike from anxiety. One study of 46 patients found systolic blood pressure rose an average of 22 points during surgery, from about 146 to 168 mmHg [2]. Being on blood pressure medication did not protect against this spike [2]. If you have uncontrolled hypertension or heart disease, this is a real concern worth discussing with your surgeon.

The evidence does not include any long-term safety data comparing patients who had sedation versus those who did not. The studies here follow patients for days to weeks, not years. There is no data on whether avoiding sedation reduces or increases the risk of postoperative cognitive dysfunction, falls, or other complications in elderly patients. One study did find that adding IV ketamine or dexmedetomidine during cataract surgery reduced postoperative cognitive dysfunction from 56% to 16-28% in older adults [1], but that study compared two different sedatives against each other, not against no sedation at all.

My call: for a healthy person without heart disease or severe anxiety, cataract surgery under topical anesthesia alone is safe and well-tolerated, with very low pain scores and complication rates matching those of sedated surgery. If you have hypertension, heart disease, or high anxiety, the blood pressure spike from stress is a real risk worth discussing with your surgeon. Confidence: moderate.