Iris Anatomy and Uveitis Overview

Study Notes

Iris Coloboma

Iris colobomas are caused by incomplete closure of the choroidal fissure
This results in a keyhole-shaped defect in the inferonasal region of the iris
The rest of the iris is typically normal
Atypical colobomas can occur in other areas, though less common
The collarette is the thickest part of the iris

Uveitis and Legal Blindness

Uveitis is a significant cause of blindness in the US
Approximately 30,000 new cases of legal blindness from uveitis occur annually in the US
This accounts for roughly 10-20% of all blindness cases in the US
Uveitis can affect people of any age, but is most frequent in people in their 40s
There is a higher prevalence of uveitis in women

Anatomy of Iris and Ciliary Body

The non-pigmented epithelium of the ciliary body is continuous anteriorly with the posterior pigmented epithelium of the iris
It is continuous posteriorly with the neurosensory retina
The non-pigmented epithelium is the innermost layer of the ciliary body and contacts the aqueous humor
The apexes of the non-pigmented epithelium cells in the ciliary body face outwards, while the apexes of the pigmented epithelium cells face inwards; thus the cells of these two layers are adjacent

Slit-lamp Examination Findings in Patients with Down Syndrome

Brushfield Spots are whitish or greyish lesions found circumferentially around the peripheral iris
They represent focal areas of stromal hyperplasia, surrounded by areas of relative hypoplasia
More common in patients with lightly pigmented irides
Strongly associated with Down syndrome, but can be present in some normal individuals

Keratic Precipitates (KPs)

KPs are aggregates of inflammatory cells found in the aqueous humor, typically on the inferior half of the cornea
Their appearance varies based on the severity, duration, and type of uveitis
Non-granulomatous KPs appear as small, discrete, fleck-like, linear, or stellate corneal opacities
Granulomatous KPs ("mutton-fat" KPs) have a fluffy, greasy, or waxy appearance and are composed of macrophages and epithelioid cells

Pupil Size

Patients who are nearsighted, young, or have lighter-colored irises typically have larger pupils than patients who are hyperopic, older, or have darker-colored irises.

Ciliary Muscle Muscle Groups

All three muscle groups (longitudinal, radial, and circular) originate from the ciliary tendon.
Only the longitudinal muscle terminates at the suprachoroid
Radial muscles attach to the ciliary processes
Circular muscles attach to the ciliary processes, but their termination point is at the anterior end of the processes

Panuveitis

Panuveitis involves inflammation of all anterior and posterior structures of the eye
According to the International Uveitis Study Group, the anatomical classification of uveitis is:
- Anterior uveitis
- Intermediate uveitis
- Posterior uveitis
- Panuveitis

Anterior Chamber Cells Grading with SUN Scheme

The SUN grading scheme for anterior chamber cells is:
- Grade 4+: 50+ cells in a 1mm slit beam field

Description

This quiz covers the anatomy of the iris and ciliary body, focusing on iris coloboma and its implications. Additionally, it discusses uveitis as a significant cause of legal blindness in the US, including its prevalence and impact. Test your knowledge on these important topics in ophthalmology.