A dog with lens subluxation is treated with latanoprost once daily. Two days later, the dog acutely develops severe pain and anterior lens luxation. What was the most likely cause of this progression?

A dog with lens subluxation is treated with latanoprost once daily. Two days later, the dog acutely develops severe pain and anterior lens luxation. What was the most likely cause of this progression?

• A. Rebound mydriasis allowed the lens to move anteriorly
• B. Increased aqueous production
• C. Lens capsule tear
• D. Intraocular infection

Answer: (A)

A partially dislocated lens can move when the pupil changes size, because weak zonules leave the lens more mobile in the eye. Latanoprost, a prostaglandin analog used to lower intraocular pressure, can cause pupil dilation (rebound mydriasis). In an eye with lens subluxation, that dilation removes the anterior-papillary restraint and lets the lens shift forward, leading to anterior luxation. The sudden forward movement irritates the eye and can produce acute severe pain with the lens luxated into the anterior chamber. So, the progression is most likely due to dilation-induced anterior movement of the already weakened lens. Other options don’t fit the mechanism: increased aqueous production wouldn’t push the lens forward, a lens capsule tear isn’t tied to the drug’s effect in this scenario, and intraocular infection wouldn’t specifically explain an acute anterior luxation after starting latanoprost.

A partially dislocated lens can move when the pupil changes size, because weak zonules leave the lens more mobile in the eye. Latanoprost, a prostaglandin analog used to lower intraocular pressure, can cause pupil dilation (rebound mydriasis). In an eye with lens subluxation, that dilation removes the anterior-papillary restraint and lets the lens shift forward, leading to anterior luxation. The sudden forward movement irritates the eye and can produce acute severe pain with the lens luxated into the anterior chamber.

So, the progression is most likely due to dilation-induced anterior movement of the already weakened lens. Other options don’t fit the mechanism: increased aqueous production wouldn’t push the lens forward, a lens capsule tear isn’t tied to the drug’s effect in this scenario, and intraocular infection wouldn’t specifically explain an acute anterior luxation after starting latanoprost.