Fundus imaging with a nasal endoscope.

Wide field fundus imaging is needed to diagnose, treat, and follow-up patients with retinal pathology. This is more applicable for pediatric patients as repeated evaluation is a challenge. The presently available imaging machines though provide high definition images, but carry the obvious disadvantages of either being costly or bulky or sometimes both, which limits its usage only to large centers. We hereby report a technique of fundus imaging using a nasal endoscope coupled with viscoelastic. A regular nasal endoscope with viscoelastic coupling was placed on the cornea to image the fundus of infants under general anesthesia. Wide angle fundus images of various fundus pathologies in infants could be obtained easily with readily available instruments and without the much financial investment for the institutes.

Fundus photography in infants and children is essential when dealing with diseases such as retinoblastoma and retinopathy of prematurity (ROP). Posterior fundus images can be obtained in co-operative children with a regular fundus camera or the slit lamp mounted digital camera, albeit with some difficulty.[1] Infants under general anesthesia may be held up to the fundus camera to obtain fundus images, but this technique is fraught with risks.

Techniques such as custom mounting the fundus camera vertically, handheld fundus camera, video indirect ophthalmoscope, and the Retcam™ have been employed to image the fundi of children under general anesthesia.[2] We had recently described a technique of using a regular hand-held video camera for photographic and video documentation of posterior fundus lesions, particularly for use in infants under anesthesia.[3] We herein describe a technique of imaging the infant's fundus using a rigid nasal endoscope.

Materials and Methods

Instrumentation

A regular nasal endoscope (Leone Nasal Endoscope, China, Costs 400 USD) can be used with a coupling agent like a viscoelastic gel.

Technique

The infant to be examined is administered general anesthesia after pupillary dilation. Adult fundus can also be imaged either in sitting/lying comfortably on the examination chair/couch. The nasal endoscope is applied to the cornea over a drop of viscoelastic gel. Care should be taken to avoid pressing on the cornea with the tip of the endoscope but to glide over the gel.

The endoscope light source illuminates the fundus allowing the video and still images to be displayed on the monitor and captured. Moving the endoscope to the periphery of the cornea and tilting it, allows visualization of the peripheral fundus and extreme periphery.

Discussion

Fundus imaging of retinoblastoma is particularly essential to assess response to treatment and in serial follow-up. Wide field fundus imaging using a contact camera is being employed in lieu of fundus examination to screen for ROP in developing countries. The choice of fundus imaging system infants remains the RetCam™. It offers wide field fundus imaging, facility to perform fluorescein angiography and portability but with the limitation of being costly.

A nasal endoscope is constructed with a cylindrical viewing system in the center and a fiber-optic light source encased around the viewing system. When applied on to the cornea, the light illuminates the fundus allowing image capture [Figs. 1–3]. Being a contact viewing system, it allows wide-angle fundus imaging, and the narrow caliber of the endoscope allows using it to view the anterior chamber angle as well [Fig. 4].

Figure 1

Posterior pole fundus photo obtained using the nasal endoscope

Figure 3

Peripheral nasal endoscope fundus image showing multiple inactive vitreous seeds and partly regressed retinoblastoma

Figure 4

Nasal endoscope image of the angle

Nasal endoscope image of a partially regressed retinoblastoma along the superotemporal quadrant

Limitations of the technique

Comparatively, the endoscope allows a narrower field (just short the equator in a single field) of fundus imaging in contrast to the RetCam™. This is because of the narrow caliber of the endoscope. The long, thin, and cylindrical endoscope with a heavy camera mounted on the top and a fiber-optic light source [Fig. 5a–b]. Attached to it can be a bit difficult to handle when in contact with the cornea. This can be mitigated with one person handling the tip of the endoscope in contact with the cornea while another supports the heavy camera part of it. If not properly placed reflexes from the corneal and lenticular surfaces may at times be troublesome.

Figure 5

(a) Picture of the endoscope, (b) Picture of the assembled endoscope with the light pipe attached and connected to the light source

Nasal endoscopes are used by oculoplastic surgeons in an eye hospital for the purpose of performing endonasal dacryocystorhinostomy. They are much less expensive than the current camera systems used for fundus imaging in infants. The technique of using it to image the fundus is simple and can be easily mastered. It offers an inexpensive technique to image an infant's fundus with reasonable quality.