SYDNEY, Australia — His eyesight is fading, but at 88, Joern Utzon's mind remains sharp, and he still makes sketches to improve his masterwork, the Sydney Opera House.

The building's custodians and Utzon's family have denied recent charges that a degenerative eye condition has left the Danish architect unable to contribute fully to renovations under way on the landmark building, and that his name is being used to push through substandard work.

The dispute is the latest episode in the bittersweet saga of Utzon and his most celebrated creation that for 45 years has played out like one of the operas staged beneath the building's unmistakable gleaming white roof shells.

Architectural critic and Utzon biographer Philip Drew said the architect's son, Jan Utzon, had told him recently that the elder Utzon could no longer see television and cannot read without a magnifying glass because of advancing age-related macular degeneration.

Likening the loss to a tragedy worse than Beethoven going deaf, Drew said the revelation raised serious doubts that Utzon can effectively communicate his ideas for work being done on the building or to understand how the changes look.

"Architecture depends on making fine judgments of space and form, scale, color and texture," Drew wrote in The Australian. "Even with assistance, Utzon's ability to make such fine judgments inevitably will be impaired, along with his capacity to convey his thoughts in drawings."

Jan Utzon, an architect himself who is working as a liaison between his father and leading Sydney architect Richard Johnson on the current work, dismissed suggestions that his father was incapable.

"My father's eyesight is somewhat impaired, true," Jan Utzon told The Associated Press in an e-mail response to questions. "But he can still see drawings and is often sketching new ideas for the opera house. He is very active concerning all issues that have relations to the opera house."

Utzon said he "may have exaggerated my father's disability" to Drew to try to protect the elderly architect from Drew's requests for interviews.

"My father turns 89 in April, and I am grateful to still have him around and to have the opportunity to work with him and his keen mind," he said.