A 65-year-old woman with a previous history of acute angle-closure glaucoma received femtosecond laser-assisted cataract surgery (FLACS) at our hospital. The patient’s pupil diameter was about 4mm and could not be dilated preceding the operation. We performed corneal microincision following pupil dilation with OVDs (Viscoat, Alcon Laboratories, Inc.). Lens fragmentation and capsulotomy were not able to be performed by FEMTO LDV Z8. We replaced the dispersive OVD--Viscoat, with an alternative cohesive OVD--Protectalon. After replacement, lens fragmentation and capsulotomy were performed smoothly under the same femtosecond laser settings. We propose the componential difference of the two OVDs, as well as lower laser pulse energy of FEMTO LDV Z8, might contribute to our reported complication. Our hypotheses require further studies with better study designs to validate. We hope this experience might reveal effects of different OVDs on FLACS and also help solve possible difficulties during FLACS on a very smaller pupil and shallow ACD cataract.