17
Eye
Indirect approaches through the eyewall opposite the tumor
have been used successfully, some in concert with pars plana
vitrectomy.70-73 To reduce the chance of hemorrhage and
needle-tract seeding, smaller gauge needles (as thin as 30 gauge)
have been used.74 Intraocular washings during vitrectomy are
addressed subsequently.
The most common intraocular fungal infections reported
are
Candida
spp. (about 85%), followed by
Aspergillus
spp.
(about 1%). Other fungal pathogens (e.g.,
Malassezia, Tricho-
sporon, Fusarium,
and
Acremonium)
represent about 11% of the
nosocomial fungal pathogens.
Endophthalm itis
Gram-positive organisms have been estimated to cause 56-
90% of all cases of endophthalmitis.
Staphylococcus aureus
is
the most commonly implicated organism, often associated
with skin infections or chronic systemic disease, such as dia-
betes mellitus or renal failure. Streptococcal species including
Streptococcus pneumoniae, Streptococcus viridans,
and group A
streptococci also are common. Gram-negative organisms like
Pseudomonas, Escherichia coli,
and
Enterococcus
are observed
in penetrating injuries.
Candida albicans
is by far the most
frequent cause (75-80% ) of fungal cases. Aspergillosis is
the second most common cause of fungal endophthalmitis,
especially in IV drug users.
Endophthalmitis is characterized by acute and chronic
inflammatory cells, including histiocytes, multinucleated his-
tiocytes, and lymphocytes. Clinically, it is important to identify
postoperative bacterial endophthalmitis because endophthalmi-
tis requires immediate antibiotic therapy. PCR-based techniques
may have the greatest value in the confirmation of the diagno-
sis of bacterial endophthalmitis especially in culture-negative
eyes.75
Key features of endophthalmitis
Bacterial:
abundant acute inflammatory cells and
necrotic debris;
Candidiasis:
budding yeast with pseudohyphae associ-
ated with acute and chronic inflammation; and
Aspergillosis:
septated hyphae, which branch at 45°
angles.
Noninfectious Inflammatory and Post-traum atic
Conditions
Cellular material obtained during vitrectomy or anterior cham-
ber aspiration assumes definite patterns reflecting the disease
processes.23,76-79 Proliferative diabetic retinopathy is the most
common condition requiring vitreous surgery.23,77 Extraretinal
fibrovascular tissue proliferates along the posterior vitreous
surface. When portions of the posterior vitreous separate from
the retina, the fibrovascular tissue may continue to proliferate,
covering parts of the retina or causing such secondary complica-
tions as vitreous hemorrhage and tractional retinal detachment.
Cytologic examination of vitrectomy fluid from patients with
proliferative diabetic retinopathy often reveals fibrovascular
membranes (Fig. 17.10).
Retinal pigment epithelial (RPE) cells are frequently seen
in cytologic preparations (Fig. 17.11). They appear as cuboidal
cells containing numerous elliptical melanin granules in the
cytoplasm.14,80 These RPE cells are believed to enter the vitreous
Fig. 17.10 Fibrovascular membrane in vitrectomy washing. Cytospin
preparation (Papanicolaou x MP).
Fig. 17.11 Retinal pigment epithelium in vitrectomy washing. Cytospin
preparation (Papanicolaou x HP).
cavity through retinal tears or holes, by migration or sometimes
dispersion after retinal cryotherapy. RPE cells have been found
in intravitreal fibrous strands.
Fragments of retinal cells may be present in vitrectomy
specimens (Figs 17.12 and 17.13). Cytologically, these cells are
found singly and in groups or tissue-like fragments. They are
slender, elongated cells, often arranged in parallel rows. At the
opposite end from the nucleus, the cytoplasm is ill defined and
attenuated. Often seen is an area of perinuclear clearing, which
is characteristic of retinal cells. They may be confused with
lymphocytes if poorly preserved.
Melanin pigment can be intracytoplasmic and free-floating
(Fig. 17.14) and should not be confused with bacteria or blood
pigment. The histiocytes seen in vitreous washing specimens can
have their cytoplasm packed with melanin granules, but their
usually eccentric, bean-shaped nuclei separate them from RPE
cells, in which the nuclei are round and centrally placed.
Chronic intraocular hemorrhage can be confirmed by cyto-
logic evaluation of vitreous fluid. In this condition, red blood
463
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