Colobus Monkey Gets a Second Chance at Sight with Cataract Surgery

This post written by Bailey Cheney of the Houston Zoo Primate Department.

We first realized that Caesar, our geriatric Eastern black and white Colobus monkey, was losing his sight around January of 2013. It started off with one of the keepers realizing that his eyes were a little cloudy. Then we noticed that he was slightly hesitant about moving around his bedroom. A sure sign that his sight was in decline was when one of the keepers noticed him bump into a new bench that had been installed. After that, it seemed that his sight was going downhill at an alarming rate. He would sit in the same spot for a long time. Whenever he moved, he would pat the ground where he walked to feel his way around.

Caesar is the oldest eastern black and white colobus monkey in a zoo at 32 years old. He lives with his mate “Bibi” in an off-exhibit special-care facility where geriatric primates are housed with indoor/outdoor access. Instead of going outside once his sight decreased, he would sit right in the doorway to feel the sunshine and enjoy the breeze all from the comfort and safety of his “old man porch.” He moved around less, understandably, and as time passed, the entire primate staff was growing more concerned about him.

Our veterinarians got in contact with Dr. Nicholas Millichamp of Eye Care for Animals. The clinic is about a forty-five minute drive from the Houston Zoo. The day of the surgery, Caesar was moved into a crate with just enough room to relax and be comfortable. Once sedated, Caesar was given a pre-surgery screening to make sure that he still had functional retinas. Thankfully, he passed that test and the surgery began. During the surgery, Dr. Millichamp dyed the cataracts for better contrast to see what he was working on. He used a very small instrument to scrape, and then suck away, the old cataracts. After removing them, Dr. Millichamp put new lenses into both eyes. During the whole surgery, the doctor used a microscope to be able to closely see what he was doing. This microscope was set up to a camera and a screen so that those observing could see everything that Dr. Millichamp saw.


Once he returned home to the zoo and recovered, the entire primate staff was very anxious to see results. The first time that I realized that he could see was when a piece of zucchini (one of Caesar’s favorites) was rolling off of the feeding tray and Caesar caught it quickly.  We observed him walk right up to his food, and he walked with confidence on the props in his bedrooms.

After a few bumps in the road as his eyes were a little slow to heal, he was finally cleared to go outside. When the door was opened, Bibi immediately went out, but Caesar hesitated. Then, he took a few steps forward and stepped onto the high walkway and followed Bibi over to a ray of sunshine, where he basked delightedly. We saw him enjoying the warm sun, watched birds fly by, and contentedly enjoy his surroundings.

Caesar continues to do amazingly well and it seems to us as if he’s lost ten years off of his 32 years. He vocalizes and displays vigorously in the morning to show the keepers who is boss, and interacts more with Bibi. These are all behaviors he had stopped doing when he was blind. He continues going strong, to the delight of the entire primate staff, and we hope to have much more time with him. We are all very thankful to the veterinary ophthalmologists who donated their time to so improve the quality of our old man’s Caesar’s life!

Caesar the colobus monkey
Caesar the colobus monkey

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