This dog has an anterior lens luxation. Clinically this can be hard to see if there is severe edema but in this case the edema is more axial or central. Here is the eye up close and you can see the edge of the clear crystalline lens peripherally.

Let’s talk about lens luxations. The lens is held in position by small thread like ligaments called zonules that go all the way around like the springs of a trampoline. They arise from the ciliary body processes and attach at the lens equator. If the zonules come undone, the lens starts to be unstable and can wobble or shake inside the eye. This is called phacodonesis. This is the earliest sign of lens instability and is often not obvious on routine exam. When then lens becomes unstable you may also notice some vitreous leaking into the anterior chamber. It is supposed to stay put behind the lens but if some zonules are missing, it can start to work it’s way up to the anterior chamber. This may look like little grey wispy smoke-like projections coming from the pupil margin and floating in the anterior chamber.

When enough zonules are lost, the lens can float around freely and may end up falling back into the posterior segment if the vitreous is degenerated or liquified or it may shift anterior which is what happened in this case.

If the lens luxates posterior, it may damage the retina or cause chronic inflammation resulting in secondary glaucoma. It may also shift forward again at some point. When the lens is posterior, it is less of an urgently vision threatening issue and often we will use a miotic (such as latanoprost) to constrict the pupil and “close the door” so the lens is less likely to wander up into the anterior chamber.

So…what do you do when your patient has a lens luxations?

If the owner is willing and able, I highly recommend referral ASAP for these guys for the best possible vision outcome. The goals are twofold: First, get the pressure down. Second, get the lens out of the anterior chamber. Sometimes you can’t get the pressure down until the lens is moved.

In your office you can immediately start trying to lower the pressure by using glaucoma medication. I recommend using Dorzolamide repeatedly initially (every 15 minutes for an hour then hourly for a few hours) to try to get the pressure to decrease.

You can also use IV mannitol. Mannitol is an osmotic diuretic and therefore will dehydrate the aqueous and the vitreous and may be effective at lowering the pressure but is not a long-term treatment option.

Do not use latanoprost if you suspect the lens is anterior! Latanoprost causes profound miosis and causing the pupil to constrict with only further shove the lens into the anterior chamber and exacerbate the glaucoma.

If the dog has the potential to see, surgery to remove the lens is recommended ASAP. This surgery is called an Intracapsular Lens Extraction (ICLE) and it involves making a large incision and remove the lens in its entirety. This surgery is not without risk of blinding complications such as glaucoma and retinal detachment but is a good option if the dog has a potential to see.

A non-surgical procedure using external surface manipulation to reposition the lens behind the pupil has been reported* and is replacing the need for urgent surgery in many situations. I tend to recommend this procedure often if the eye is non-visual at the time of presentation and we are trying to see if we can restore vision before deciding on surgery or in geriatric animals where the primary goal is lowering the pressure for comfort. This is often referred to as “couching”.

What causes lens luxation?

Primary lens luxation (PLL) is genetic in many breeds including terriers, poodles, Australian shepherds, and many more. In many of these dogs there is also a genetic mutation that is linked to development of primary glaucoma.

Lens luxation can also occur secondary to chronic inflammation. Anterior uveitis can lead to breakdown of the zonules and secondary lens instability. This is the most common cause in feline patients.

Montgomery KW, Labelle AL, Gemensky-Metzler AJ. Trans-corneal reduction of anterior lens luxation in dogs with lens instability: a retrospective study of 19 dogs (2010-2013). Vet Ophthalmol. 2014 Jul;17(4):275-9. doi: 10.1111/vop.12142. Epub 2014 Jan 10. PMID: 24405506.