Factors influencing pupil behaviour during femtosecond laser assisted cataract surgery

Femtosecond laser assisted cataract surgery is associated with pupillary constriction. This study aims to look at patient and surgical factors predisposing to abnormal pupil behaviour during FLACS.

This prospective observational study included all patients undergoing FLACS in the Princess of Wales Hospital, Bridgend, UK between February and June 2017. Pupils were measured at three time points; immediately before and after laser pre-treatment, and at the start of surgery. Pupil behaviour during surgery was noted in descriptive terms, patient demographic, co-morbidities, eye measurements, suction on time, shifting time and laser energy levels were recorded.

Seventy-three eyes were included. Average patient age was 74.84 ± 9.1 years. Mean horizontal pupil sizes immediately before and after femto pre-treatment were 7.87 ± 0.87 mm and 7.7 ± 0.89 mm respectively (P < 0.0005). Mean horizontal pupil size at the start of surgery was 6.83 ± 1.43 mm (P < 0.0005). Short capsulotomy-pupil distance (P = 0.01), shallower anterior chamber (P = 0.0012), smaller pre-operative pupil size (P = 0.045) and longer suction on time (P = 0.0019) were significantly associated with intra-operative miosis during FLACS. Sustained mydriasis was observed in eyes in whom topical diclofenac was used within 2 h of surgery.

FLACS can result in significant pupil miosis. Eyes particularly at risk are ones with smaller pre-operative pupils and shallower anterior chambers and those subjected to longer suction on time. Well-timed NSAIDs application could be protective against this phenomenon.