Factors influencing pupil behaviour during femtosecond laser assisted cataract surgery.

AIM: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.