Dr. Neil Friedman documents a case of irregular iris transillumination and looks into the possible cause and clinical impact.
A 62-year-old man presents for a cataract consultation. He reports more difficulty with his vision OS, especially from headlights when driving at night. His past ocular history is unremarkable. His BSCVA is 20/20 OD and 20/30+2 OS that reduces to 20/50-2 with glare testing. During anterior segment examination, retroillumination reveals the following finding:
The slit lamp photos demonstrate an unusual pattern of focal iris transillumination.
What is the differential diagnosis of iris transillumination?
Iris transillumination can be caused by stromal or iris pigment epithelial loss or a defect/hole in the iris tissue. The differential diagnosis includes: albinism, trauma (surgical or penetrating), previous iridocyclitis (herpetic, Fuchs’ heterochromic), previous angle closure attack, pigment dispersion syndrome, UGH syndrome, iridoschisis, ICE syndrome, mesodermal dysgenesis syndromes, medication (systemic moxifloxacin).
What other history and findings would you look for?
There is no history of eye surgery, trauma, inflammation, albinism, photophobia or systemic fluoroquinolone use. The intraocular pressure, pupillary response, and extraocular motility are normal. There is no nystagmus. Slit lamp exam shows normal conjunctiva and the corneas are clear. No posterior embryotoxon or corneal endothelial abnormality is noted. The anterior chambers are deep and quiet, and the iris appears normal on direct illumination OU. Gonioscopy reveals grade 4 open angles with normal pigmentation of the trabecular meshwork and no iris processes. Mild nuclear sclerotic cataracts are present in both eyes and there is moderate cortical spoking involving the visual axis OS. There is no phacodonesis evident. Posterior segment exam shows no abnormality and the fundus pigmentation is normal OU.
What is the etiology?
The etiology is uncertain; however, this unusual, symmetric, discrete pattern of iris transillumination is an isolated finding that appears to be a congenital anomaly. This is an unknown case, so I welcome any other suggestions.
What possible signs would you watch for at the time of cataract surgery?
Because this patient has a presumed congenital anomaly of the iris that could possibly include other anterior segment structures, there may be suboptimal pupillary dilation, intraoperative floppy iris syndrome, and weakness of the zonules or capsule.
The patient did undergo cataract surgery without complication. Although his pupil dilated to 6.5 mm, the dilation was asymmetric with less dilation of the nasal iris. The iris was floppy and billowed at times with irrigation during phacoemulsification and cortex removal. The lens capsule behaved normally and zonular weakness was not noted. These intraoperative findings of a segmental atonic iris further support an isolated congenital etiology for the patient’s iris abnormality.