Ординатура / Офтальмология / Английские материалы / Essentials in Ophthalmology Cornea and External Eye Disease_Reinhard_Larkin_2007

tance for the in vivo diagnosis of conjunctivalization associated with corneal stem cell deficiency.

In the basal epithelial layer hyper-reflective dendritic cells are to be seen.

Subepithelially, the basement membrane appears as a prominent hyper-reflective band with multiple inserting fibers. In contrast to in vivo confocal microscopy of the cornea, where stromal collagen fibers are not visible under normal conditions, the dense irregular collagen network of the conjunctival stroma appears hyper-reflec- tive and clearly visible in healthy and diseased tissue [17]. Single fibroblasts may not, however, be detected in healthy conjunctival stroma, but are visible on scans of filtering blebs after glaucoma surgery [19]. The stroma contains perfused vessels, cystic spaces often in close association with vessels –probably lymphatic channels – and single inflammatory cells. The episclera and sclera are too deep to be visualized with in vivo confocal microscopy.

At the corneal limbus the conjunctival epithelium and stroma form the well-known palisades of Vogt with associated vessels and presumed lymphatics in vivo microscopically (Fig. 12.2) [11, 17]. Small pigmented granules and delicate dendritic cells are often visible in the basal epithelial cells.

12.2.2.2 Normal Tarsal Conjunctiva

The normal tarsal conjunctiva shows a thin epithelium composed of 2–3 layers of small, cuboidal epithelial cells under in vivo confocal microscopy. The epithelium is moderately infiltrated by inflammatory cells with a round hyper-reflective nucleus, probably lymphocytes. In contrast, the normal tarsal conjunctival stroma is heavily infiltrated by a round cell infiltrate (Fig. 12.3). Tiny subepithelial microcysts, often containing inflammatory cells, are a frequent finding [17].

12.2.2.3 Normal Lid Margin

At the lid margin, meibomian gland orifices, lashes, and adjacent glands of Zeis are visible by in vivo confocal microscopy (Fig. 12.4). Adenoid structures including meibomian gland ducts lined with a multilayered epithelium as well as gland acini appear at approximately 30 µm in depth in the upper and at about 80 µm depth in the lower tarsus. Sometimes hair follicles may be observed at a depth of 150–200 µm [17].

Fig. 12.2  In vivo confocal images of a normal limbus. Rete pegs of the limbus (palisades of Vogt)

Fig. 12.3  In vivo confocal microscopy of the tarsal conjunctiva with subepithelial round cell infiltrate

Fig. 12.4  Lid margin with skin , (asteriks), meibomian gland orifice (arrows) and tarsal conjunctiva (hash)

Fig. 12.5  In vivo confocal microscopy in acute conjunctivitis. Mixed cell infiltrate composed of round cells (arrowheads) and cells with multi-lobate nucleus compatible with neutrophils (arrows)

Fig. 12.6  Confocal images of papillary conjunctivitis demonstrating a fibrotic core with a central vessel surrounded by inflammatory cells

12.2.3.4 Cicatrizing Conjunctivitis

In cicatrizing conjunctivitis, including trachoma, Stevens-Johnson syndrome, conjunctival lichen planus or severe atopic keratoconjunctivitis, a hyper-reflective fibrotic network is observed subepithelially (Fig. 12.8). In active

Fig. 12.7  In vivo confocal microscopy in follicular conjunctivitis. Follicle-containing hyporeflective round cells surrounded by a hyper-reflective capsule and vessels

inflammation fibrosis is associated with infiltration of rather monomorph, hyper-reflective round cells, whereas in atopic keratoconjunctivitis tarsal papillae are observed in addition to subepithelial scarring by in vivo confocal microscopy.

Fig. 12.8  In vivo confocal microscopy in cicatrizing conjunctivitis exhibiting subepithelial hyper-reflective nets of fibrosis

12.2.3.5 Conjunctival Granuloma

A conjunctival granuloma following pars plana vitrectomy exhibited surprisingly few inflammatory cells and moderate vascularization by in vivo confocal microscopy. A vermiform structure, most probably a Vicryl suture, was embedded in hyper-reflective, fibrotic tissue [17].

12.2.3.6 Blepharitis

Dysfunction of the meibomian glands with inflammation and obstruction has been suggested to be an important factor in the pathogenesis of chronic blepharitis. However, few objective tests are available to examine meibomian glands directly. Patients with anterior blepharitis, meibomitis, meibomian gland dysfunction or severe keratoconjunctivitis sicca associated with blepharitis were examined with near-infrared laser in

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Fig. 12.10  In vivo confocal microscopy of conjunctival papilloma. Fibrovascular stromal core surrounded by a thickened epithelium and round cells

cur in older individuals and are more common in men than in women. CIN most often arises in the interpalpebral fissure and appears as an elevated plaque or a gelatinous mass with fronds of blood vessels near its surface. Keratinization may be present. When the dysplastic cells break through the basement membrane of the basal epithelial layer and invade the substantia propria, the lesion is classified as a squamous cell carcinoma [8, 24]. The clinical diagnosis of squamous cell carcinoma may be difficult, as it has a spectrum of presentations, from subtle white dots corresponding to parakeratosis to a process that may mimic chronic conjunctivitis.

In CIN, in vivo confocal microscopy may demonstrate a keratinized hyper-reflective surface and an acanthotic epithelium with abnormally large, dysplastic epithelial cells featuring a prominent nucleus and nucleolus (Fig. 12.11). CIN is especially easy to evaluate in the area of the limbus and on the corneal surface. As the penetration of in vivo confocal microscopy in the conjunctiva is limited to about 200 µm, and keratinization may further restrict scanning, the demonstration of invasive growth in squamous cell carcinoma is difficult.

Fig. 12.11  In vivo confocal microscopy of conjunctival intraepithelial neoplasia demonstrating large dysplastic epithelial cells

12.2.5In Vivo Confocal Microscopy in Melanocytic Tumors

of the Ocular Surface

Pigmented lesions of the conjunctiva such as nevi, primary and secondary acquired melanoses, and malignant melanomas present a challenge to both the ophthalmologist and the pathologist. The difficulty in clinical diagnosis is overwhelming. Whereas nevi were clinically diagnosed correctly only 49% of the time, melanoma was clinically suspected in 56% of the cases [8]. In addition, diagnosis is hampered by the fact that almost 30% of conjunctival nevi are clinically almost entirely non-pigmented [7]. Other pigmented conjunctival lesions such as primary acquired melanosis with and without atypia as well as secondary acquired melanosis of the conjunctiva may be clinically indiscernible as well. This may be deleterious given the fact that progression from PAM with atypia to malignant melanoma occurs in 75% of patients with epithelioid cells and in 90% of patients whose predominant growth pattern is not basilar hyperplasia [5–7, 23]. Laser confocal microscopy is able to differentiate between distinct melanocytic conjunctival lesions in vivo. Although in comparison to histology the magnification and the window of imaging of in vivo

confocal microscopy are limited, the examination of several different areas of interest provides a satisfying overall picture.

12.2.5.1.2Primary Acquired Melanosis with/without Atypia

Hyper-reflective cells, granules and patches confined to the basal epithelium are a typical sign of PAM without atypia or secondary acquired melanosis (complexion-associated melanosis) as seen on in vivo confocal microscopy. This is especially evident in oblique images. Small hyperreflective dendritic cells are often observed in the basal epithelium (Fig. 12.13). In contrast, in PAM with atypia hyper-reflective cells, granules and patches are typically observed throughout the entire epithelium. Most of these lesions extend into the corneal epithelium with highly reflective granules visible in basal corneal epithelial cells. However, the hallmark of PAM with atypia is networks of giant, hyper-reflective, dendritic cells (Fig. 12.14). These large dendrites were not observed in any benign melanocytic lesion of the conjunctiva, but were associated with melanomas arising from PAM with atypia [18].

Fig. 12.12  In vivo confocal microscopy of conjunctival nevus demonstrating epithelial pseudocysts and nests of hyper-reflective and hyporeflective mediumsized, monomorph cells compatible with nevus cells

Fig. 12.13  In vivo confocal microscopy of primary acquired melanosis without atypia. Hyperreflective granules in basal limbal epithelium associated with small dendritic cells (arrow)

Fig. 12.14  In vivo confocal microscopy of primary acquired melanosis with atypia showing arborizing networks of giant dendritic cells

12.2.5.2Malignant Melanocytic Tumors – Malignant Melanoma

Malignant melanomas of the conjunctiva are typically covered by a thin epithelial layer as seen by in vivo confocal microscopy. In pigmented lesions, highly reflective cells are visible directly subepithelially. The visibility of detailed cellular structures, however, is improved in deeper, less reflective scans. In amelanotic lesions the identification of tumor cells is facilitated by overall lower reflective images. The lesions contain accumulations of cells with large and atypical hyper-reflective nuclei and prominent hyporeflective nucleoli (Fig. 12.15). However, typical spindle or epithelioid cells, and/or a fascicular tumor formation, cannot be discriminated by in vivo confocal microscopy. Tumor cells are often surrounded by small, highly reflective round cells, most probably inflammatory cells. Multiple large vessels are evident in the lesion. In vivo confocal microscopy showed a sensitivity of 89% and a specificity of 100% to diagnose malignant melanoma of the conjunctiva correctly. The positive and negative predictive values for diagnosing conjunctival melanoma were 100%

Fig. 12.15  In vivo confocal microscopy of malignant conjunctival melanoma demonstrating cells with large and atypical hyper-reflective nuclei and prominent hyporeflective nucleoli (arrows)

and 5% respectively. The area under the receiver operating characteristic (ROC) curve was 96% [18].

Typical features of malignant melanoma could also be observed in patients with extrascleral growth of uveal melanoma by in vivo confocal microscopy [18].

12.2.6In Vivo Confocal Microscopy in Other Lesions of

the Conjunctiva

12.2.6.1 Conjunctival Amyloidosis

Conjunctival amyloidosis most often occurs sporadically as a primary localized deposition in the absence of antecedent or coexisting adnexal disease [24]. In vivo confocal microscopy of a patient with conjunctival amyloidosis disclosed large hyper-reflective areas and bands with net-like appearance as well as hyporeflective amorphous substance in the conjunctival stroma (Fig. 12.16). These observations are compatible with the diffusely distributed, eosinophilic, homogeneous, birefringent material seen in the conjunctival stroma on histology.

Fig. 12.16  In vivo confocal microscopy of conjunctival amyloidosis with hyper-reflective band-shaped and hypo-reflective amorphous (asterisks) stromal substance

Fig. 12.17  In vivo confocal microscopy of a limbal dermoid demonstrating tightly packed collagenous tissue and adenoid structures

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12.2.6.2 Limbal Dermoid

Epibulbar dermoids arising within the limbal and canthal portions of the conjunctiva are classified as choristomas because they contain displaced epithelial and dermis-like elements normally not found in these areas. On histology, these lesions may be either solid, well-defined limbal dermoids, more diffuse dermolipomas or complex choristomas with variable contents. Limbal dermoids typically demonstrate a dense collagenous stroma with hair follicles, sweat, and sebaceous glands [24]. In vivo confocal scans may show tightly packed collagenous tissue with vascularization, and adenoid structures (Fig. 12.17). In dermolipoma, hyporeflective spaces, most probably adipose tissue, are a prominent feature seen by in vivo confocal microscopy.

Summary for the Clinician

■In vivo confocal microscopy is a valuable new tool in the differential diagnosis and follow-up of conjunctival tumors

■Benign and malignant epithelial and melanocytic lesions of the conjunctiva show typical in vivo confocal microscopic features similar to histopathology, and can

be clearly differentiated

■ In vivo confocal microscopy exhibits a high sensitivity and specificity to diagnose melanocytic tumors of the conjunctiva compared with the gold standard histology

■The use of the in vivo confocal microscope is encouraged as an important diagnostic advice; yet, clinically and/or in vivo microscopically suspect lesions require biopsy. However, biopsy may be guided by the added information gained by in vivo confocal microscopy

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