Eye Saved After Unusual Neurogenic dry eye Diagnosis
Clinical Connections – Spring 2025
Serena Maini, Lecturer in Ophthalmology
Lily, a 10-year-old Parson Russell terrier, was scheduled to undergo enucleation surgery but her eye was saved due to the interventions of the Ophthalmology Service and efforts of her owners in administering medication.
Her owners noticed that Lily was squinting in the left eye, and her primary care vet identified a very low tear production in both eyes and a superficial corneal ulcer in her left eye. She was started on lubrication in both eyes and chloramphenicol in the left eye.
Lily returned a few days later and was started on cyclosporine ointment in both eyes. When she returned to the primary care vet, there was a concern that the ulcer had become much deeper. Cyclosporine was discontinued in the left eye and Lily was referred to the RVC team.
At the RVC
Lily was found to have a dry appearance to the surface of both eyes, with the left eye more affected than the right. The tear production in the right eye had improved but was still very low. Cyclosporine ointment was restarted in the left eye to support ulcer healing. Topical lubrication was increased, and Lily was sent home, to be re-examined in a few days’ time.
When returning to the RVC a week later, the tear production from Lily’s right eye had further improved and was nearly normal. However, Lily’s left eye remained very painful and there was minimal (if any) tear production. An ipsilateral dry nostril (xeromycteria) developing, in addition to near absent tear production and lack of response to cyclosporine ointment, was strongly suggestive of neurogenic keratoconjunctivitis sicca (KCS) affecting the left eye.
There are various causes of neurogenic KCS, including otitis media and interna, but many incidences are idiopathic and often enter spontaneous remission. In the presence of denervation hypersensitivity, which takes at least two weeks to develop, treatment with oral pilocarpine (parasympathomimetic) can be beneficial while the parasympathetic nerve heals.
In addition to neurogenic KCS, Lily's left eye exhibited two stromal abscesses within the cornea. This development worsened the prognosis for her left eye, and her owners were warned about possible corneal melting (keratomalacia) or even corneal perforation (rupture).
Decisions
After discussion with the clients about the guarded prognosis for the left eye, and their options for management (continuation of the medical treatment versus enucleation), they made the difficult decision to remove Lily's left eye. This was booked for the following day, following a CT scan of Lily’s head to investigate for an underlying cause of neurogenic KCS.
The following day, the clients reported that Lily's left eye seemed more comfortable since commencing oral paracetamol. Lily reluctantly accepted her eye medication through her owners’ firm but gentle approach. The stromal abscesses had deteriorated, however, and a third one was now present – three regions (approximately 2-3 mm) of yellow stromal infiltrate were visible on slit lamp examination and a presumptive diagnosis of idiopathic neurogenic dry eye was made. Most such cases resolve within 4-6 months. Her owners at this point decided to attempt medical treatment rather than enucleation.
During the 4-6 month period, while the nerve would heal and regenerate, use of pilocarpine eye drops (given orally) were used to increase Lily's tear production, thereby improving her comfort and helping her cornea to heal.
By the following week, Lily's left cornea had shown significant signs of improvement – the stromal abscesses and the ulcer had virtually healed. The tear production in the left eye had not yet responded to pilocarpine, so we began to gradually increase the dose. The right eye had continued to respond well to cyclosporine ointment and had normal tear production.
On a return visit a fortnight later, Lily showed significant progress. The stromal abscesses and corneal ulcer had resolved. Lily seemed to be experiencing some nausea, a likely side effect of the pilocarpine, so we split the dose between morning and evening to alleviate that.
A return visit to the RVC Ophthalmology Service the next month and subsequent visits have showed an ongoing good response to treatment thanks to the diligent efforts of owners to administer her medication. Within two months her tear production had returned to normal and by three months both eyes were wide open, bright and shiny.