In vivo confocal microscopy of corneal insect foreign body

Management of Secondary Keratouveitis in a Wasp Sting Patient in a Jungle Region of Peru

Wasp stings are considered an ophthalmological emergency as they can be complicated when they occur near the eyelids or especially on the cornea. Due to type I hypersensitivity response, such as epithelial defect, corneal edema, loss of endothelial cells, anterior uveitis, optic neuritis and, therefore, permanent loss of vision due to anterior segment ischemia. It warns that the wasp stinger has a saw-shaped texture, contains toxins that inflame the area where it stings. Due to the immunological and toxic effects of the stinger and its venom infiltrates the cornea. We present the case of a 32-year-old man who presented keratouveitis secondary to a wasp sting in a region of the jungle of Peru. He was treated emergency with intensive steroid therapy to reduce the toxic effects. His follow-up up to 2 months was successful, leaving only a 1 mm central leukoma where the bite occurred, which did not impair his vision.

The role of in vivo confocal microscopy in the diagnosis of hidden corneal foreign bodies

OBJECTIVE

To investigate in vivo confocal microscopy (IVCM) to diagnose hidden corneal foreign bodies.

METHODS

Male Kunming mice (n = 25; 12 weeks old) were anaesthetized prior to the insertion of five different materials (spiny wood, rusty iron, sharp stone, sharp glass fragment and human hair fragment) into the cornea by different traumatic processes. A separate mouse was used for each corneal foreign body. The corneas of the mice were scanned 24 h later by a laser scanning IVCM to establish the characteristics (shape, reflectivity and depth in the cornea) of each foreign body. These findings were used to help screen and identify corneal foreign bodies in patients. Corneal smears and scraping cultures were performed in cases of probable corneal infection.

RESULTS

Animal models for the five different foreign particles were established successfully, with each showing distinctive characteristics. These animal results were used to diagnose 41 patients with suspected corneal foreign bodies who were negative by slit lamp examination, but positive by IVCM (observational case series). The most prevalent type of hidden foreign body was plant material (51.2%), followed by metal (29.3%). Ten patients with corneal foreign bodies developed fungal keratitis, found using IVCM.

CONCLUSIONS

Laser IVCM is an effective and reliable tool for the diagnosis of hidden corneal foreign bodies.

Clinical corneal confocal microscopy

Confocal microscopy allows non-invasive in vivo imaging of the ocular surface. Its unique physical properties enable microscopic examination of all layers of the cornea and have been used to investigate numerous corneal diseases: epithelial changes, numerous stromal degenerative or dystrophic diseases, endothelial pathologies, corneal deposits, infections, and traumatic lesions. It offers a new approach to study the physiological reactions of the cornea to different stimuli and the pathophysiologic events leading to corneal dysfunction in certain diseases. Confocal microscopy proves to be a powerful diagnostic tool and is especially of value in certain corneal diseases by allowing straightforward and non-invasive recognition of the pathologic conditions.