Federer's quest for a ninth Wimbledon crown gained momentum with a flawless 6-4 6-4 6-1 win over Slovakian world No 73 Lacko in 89 minutes.
The 36-year-old is now on his joint second longest streak of sets won at Wimbledon - his best was 34 between the third round in 2005 to the 2006 final.
The men's top seed has now won 26 successive sets at SW19, the BBC reports, and in the third round he will face Ivo Karlovic or Jan Lennard Struff.
"Yeah, I'm very happy on both ends, absolutely", Federer said.
"I felt it's an opportunity missed", he said.
"I was really able to enjoy the match out there because I got off to a good start". The elder sibling is looking more fallible these days, dropping the first set in each of her opening two matches, but crucially she is finding ways to win. Murray won the mixed doubles with Martina Hingis previous year and will be looking to defend his title.
Kyle Edmund, Roger Federer, Gael Monfils, even American Madison Keys weighed in on the World Cup debate enveloping Wimbledon at the minute.
Meanwhile, five-time champion Venus Williams battled into the third round with a 4-6, 6-0, 6-1 win over Romanian qualifier Alexandra Dulgheru. She's had a really good year last year.
She now faces French world number 62 Mladenovic, whom she defeated in their only meeting at the French Open in 2016.
"I´m getting there. I expect to get there, not only for Wimbledon but for the tournaments in the future".
Winning 6-4, 6-4, 6-1 in 90 minutes, Federer showcased the best of his talents as he kept Lacko at arm's length with his impressive range of shots.
After her loss Swan said on Twitter: "Tough one today but overall a great experience". If that's working for me I'm all for it. "I just hope every match is better".
Croatian world number 55 Donna Vekic followed up her shock success against fourth seed Sloane Stephens with a 7-5, 6-4 victory against Sweden's Rebecca Peterson.
The 23-time major victor will next face France's Kristina Mladenovic or Germany's Tatjana Maria for a place in the last 16.
Wozniacki is still waiting to get past the round of 16 for the first time, despite fighting back from 5-1 down in the third set and saving four match points at 5-3.
Five-time victor Venus Williams opens on Court One against Kiki Bertens.
At one point, Federer had won 35 consecutive points on his serve as Lacko simply struggled to contend with the reigning and defending Wimbledon champion. Venus is attempting to win her 50th career title, while Federer is after his 21st Grand Slam.
The former beat Viktoriya Tomova, while the latter overcame Lukas Lacko, but second seed Caroline Wozniacki crashed out at the hands of Ekaterina Makarova.