In Vivo Confocal Microscopy in the Diagnosis and Management of Dry Eye: A Focus on Imaging Protocols and Interpretation

This research demonstrates how to use IVCM to observe the microscopic ocular surface structure of patients with dry eye disease. The main experimental challenges are the absence of a marker-based positioning and a limited field of view. To begin, prepare all required materials for the procedure.

Examine and understand the key components of the in vivo confocal microscopy device, and wear a protective face mask and disposable gloves. Wipe the forehead and chin rests of the device thoroughly with alcohol swabs to disinfect them. On the connected computer, open the accompanying IVCM software.

Verify existing patient information and create a new patient record if required. Administer two drops of ophthalmic topical anesthetic in the lower fornix of the patient's eye, maintaining a three-minute interval between each drop. Then prepare the Rostock cornea module by coating its laser-emitting area with coupling gel, ensuring that no air bubbles are present.

And attach a disposable corneal contact cap securely onto the Rostock cornea module. Next, retract the Rostock cornea module completely. Secure the forehead rest in a horizontal position and adjust the monitoring camera toward the temporal side of the subject.

Identify the camera's stop point that aligns perpendicular to the optical axis of the module. Rotate the focus knob until the software displays a maximized white facula with the image quality value reading exactly 100. Then reset the depth value to zero to complete calibration.

Now select Section mode as the default scan mode, unless another mode is specifically indicated. Ask the patient to rest their chin firmly on the chin rest. Press their forehead gently against the forehead rest, and adjust the examination table and chin rest to match the patient's height.

Insert the eyelid speculum carefully to keep the patient's eyelids open for the procedure. Begin macroscopic alignment by visually adjusting the Rostock cornea module to approximate the corneal apex. Switch to the monitoring camera to fine-tune alignment as the module approaches the cornea.

Instruct the patient to rotate their gaze when examining lesional corneas, centering the lesion under the module. Maintain gentle contact between the cap and cornea to avoid damage. Now, depress the foot pedal to perform prolonged scanning, capturing sequential depth images to ensure no critical data are missed.

Then perform layered corneal assessment by scanning progressively from the superficial to the deep layers, from the corneal epithelial cells to the sub-basal nerve fibers and subepithelial inflammatory cells. Focus on the inferior whorl region, the recommended anatomical landmark, and examine the adjacent superior and inferior areas. Next, reset the focal plane to a depth value of zero and apply coupling gel evenly onto the corneal contact cap.

Instruct the patient to direct their gaze temporally or inferotemporally, and gently advance the RCM toward the conjunctival surface. With the right hand, adjust the RCM position for an optimal field of view. With the left hand, rotate the focus knob to locate goblet cells in the outermost conjunctival layer.

Remove the eyelid speculum carefully after the imaging procedure is complete. Reset the device by releasing and elevating the forehead rest, zeroing the focus knob, and reapplying coupling gel to the RCM surface. For meibomian gland and eyelash follicles evaluation, instruct the patient to look downward.

Using one hand, gently elevate and press the upper eyelid skin inward to align the lid margin parallel to the corneal cap plane. Move the RCM horizontally to capture multiple images of similar structural features and vertically from bottom to top to transition from meibomian gland orifices to gland acini and eyelash roots. Perform post-procedure hand hygiene by disinfecting hands thoroughly.

Gently wipe away residual coupling gel, tears or debris from the ocular surface with a medical cotton swab. Instill antibiotic eye drops to the patient to prevent infection. Finally, document and report findings by including at least one image per examined tissue structure.

Arrange all selected images in the order of examination sequence and depth value, followed by detailed descriptions and quantitative measurements. When the central optical zone achieved perfect contact with the target tissue, clear and complete images of ocular structures were obtained. Corneal epithelial cell pathology in dry eye disease exhibited hyper-reflective borders and altered cell morphology.

Sub-basal nerve fiber degeneration in dry eye disease showed terminal swellings and beading and axonal tortuosity with reduced density. Conjunctival goblet cell density was markedly reduced to around 25 cells per square millimeter, showing only four goblet cells per field. In other dry eye cases, goblet cells were absent and conjunctival epithelium showed enhanced reflectivity.

Meibomian gland orifices in dry eye disease were dilated and completely obstructed. Some orifices were occluded by multiple Demodex brevis mites, visible with characteristic tail projections. Meibomian acini in dry eye disease were dilated, fused and structurally disrupted, with signs of asinar atrophy and periasinar fibrosis.

Eyelash follicles infected with mites contained visible Demodex organisms and secretory debris. Intact mites on the eyelid skin showed distinct mouth parts and legs. Inflammatory and immune cells were abnormally distributed in ocular tissues in dry eye disease.

This protocol achieves an integrated multimodal assessment of dry eye through a single procedure at the cellular level. Future research may focus on AI-assisted distinction between different cells of IVCM images, and expanding the observation field of view.