Stereoacuity and depth perception decrease with increased instrument magnification: comparing a non-magnified system with lens loupes and a surgical microscope.

PURPOSE: To evaluate the effect of instrument magnification used in eye surgery on stereoacuity and depth perception. METHODS: Twenty-one subjects (10 clinical ophthalmologists familiar with loupes and operating microscopes and 11 non-ophthalmologists) with normal near vision and stereoacuity were tested with the Randot Stereotest viewed unmagnified, with a 4x loupes (450 mm focal length), and with a 16x operating microscope. RESULTS: Total scores: 8 errors in 210 test steps with the unmagnified observations, 25/210 with loupes, and 30/210 with the microscope. The statistical differences in these scores were "statistically highly significant" for all three tests (p = 0.002); and "significant" for the unmagnified versus loupe (p = 0.007) and unmagnified versus microscope (p = 0.002). Test viewing through the microscope, the greatest errors occurred (total errors = 1840 seconds of arc), less with the loupes (total 1150") and least without magnification (total 220"). Errors and scores for 10 experienced ophthalmologists were no different (p > or = 0.55, p = 1.00) from the 11 non-ophthalmologist subjects. CONCLUSIONS: Stereoacuity and depth perception decrease when viewing a test target with loupes or with a microscope, with the effect worsening as magnification increases. Familiarity with the magnifying equipment did not improve stereoacuity.

Scanning slit confocal microscopy of fungal keratitis.

In vivo scanning slit confocal microscopy was performed in a patient with Fusarium solani keratitis. Morphologically distinctive abundant filamentous structures were observed intrastromally. Confocal microscopy of the culture plate growing F solani from the patient's corneal scraping revealed filaments morphologically similar to the filaments observed in vivo. After 1 week of medical therapy, subsequent confocal microscopy showed an increased load of filaments, supporting the decision to perform a penetrating keratoplasty. Confocal microscopy confirmed that all of the fungus was eradicated. This aided in the decision to administer corticosteroids and quickly discontinue antifungal agents.

The barrier function in neodymium-YAG laser capsulotomy.

BACKGROUND: Complications following neodymium (Nd)-YAG laser capsulotomy have been attributed to damage to the capsule and vitreous face. OBJECTIVES: To measure the disruption of the anterior-posterior extracapsular barrier complex induced by Nd-YAG laser capsulotomy and to determine how it might be minimized, using a fluorophotometer. DESIGN: Prospective study of 21 eyes undergoing Nd-YAG laser capsulotomy and cross-sectional comparison with 15 pseudophakic eyes with clear capsules. SETTING: University-based clinical practice. INTERVENTION: Neodymium-YAG laser posterior capsulotomy per study protocol. MAIN OUTCOME MEASURE: Change in extracapsular barrier efficiency as measured by fluorophotometry. RESULTS: Multivariate regression demonstrated that both anterior vitreous disruption and absence of a posterior chamber intraocular lens (aphakia) were significantly correlated with loss of barrier efficiency, whereas capsulotomy size was not. The anterior vitreous was judged to be undamaged in 67% of eyes treated by the study protocol. However, all myopic eyes sustained damage. Opacification of the posterior capsule itself was also associated with mild loss of barrier function even before capsulotomy, compared with the clear-capsule group. Glaucoma occurred more frequently when barrier efficiency was lost postoperatively. CONCLUSION: Damage to the extracapsular barrier complex by Nd-YAG laser capsulotomy is minimized when the anterior vitreous is preserved. The study treatment protocol may be useful in limiting this damage and in reducing complications.

Interferon treatment of Mooren's ulcers associated with hepatitis C.

PURPOSE/METHODS: The cause of Mooren's ulcer is unknown. We examined a patient with chronic hepatitis C who had a corneal ulceration that resembled Mooren's corneal ulcer. RESULTS/CONCLUSION: The corneal ulceration progressed despite appropriate medical and surgical interventions. Recombinant interferon alpha 2b finally led to resolution of the process. The resolution correlated with normalization of the patient's liver function tests. Corneal ulcerations that resemble Mooren's ulcer may be associated with hepatitis C. Recombinant interferon alpha 2b seems to induce remission in the corneal as well as the systemic condition.

Scanning slit confocal microscopic observation of cell morphology and movement within the normal human anterior cornea.

PURPOSE: Noninvasive in vivo observations of the anterior human cornea were performed to study cell structure and dynamics. Cellular elements were identified by their location, morphology, and pattern of movement. The hypothesis that cells in the epithelial layer of the normal cornea migrate centripetally was tested. METHODS: Using a scanning slit confocal microscope with a new 0.75-numeric aperture contact objective, individual cells of normal human corneas were observed over time, quantifying the velocity and direction of cellular movement within the basal epithelial layer. RESULTS: Basal epithelial cells, wing cells, the basal epithelial nerve plexus, and the subepithelial nerve plexus were identified readily. Centripetal motion was observed for three corneal cell types: basal epithelial cells, basal epithelial nerves, and unidentified cellular elements (possibly Langerhans cells). The unidentified cellular elements moved along the length of the basal epithelial nerves. The basal epithelial nerve plexus maintained a roughly stable topology as it slid centripetally. New nerve material appeared at the site of entry of the nerve into the epithelium. No growth cones were present at the distal termini of the growing epithelial nerves. CONCLUSION: In the midperiphery of the normal human cornea, basal epithelial cells and nerves slide centripetally, probably in concert. Unidentified cellular elements used the basal epithelial nerve plexus as a pathway for intraepithelial movement. Observations in this study suggest that neurite growth occurred by the addition of new membrane material along the length of the axon rather than at a distal growth cone.

Wide field scanning slit in vivo confocal microscopy of flattening-induced corneal bands and ridges.

We used a wide field scanning slit confocal microscope to examine the response of the in vivo human cornea to flattening. Flattening-induced effects consisted of (1) anterior corneal mosaic, which appeared as a meshwork of intersecting stromal and Bowman's layer bands with overlying epithelial ridges; (2) deep and middle stromal bands, which were narrower than and unrelated in position to the anterior corneal mosaic; and (3) posterior surface ridges. The posterior surface ridges projected posteriorly into the anterior chamber consisted of endothelium, Descemet's membrane, and posterior stroma, and were unrelated in position to posterior stromal bands. Confocal microscopy is a promising modality in the examination of the cornea and its response to mechanical stress.

In vivo scanning slit confocal microscopy of Acanthamoeba keratitis. A case report.

A 29-year-old woman presented with clinical signs and symptoms of Acanthamoeba keratitis. Scanning slit confocal microscopy revealed a 26-mu-diameter object, resembling an Acanthamoeba cyst, in the anterior stroma. Numerous ovoid objects (possibly inflammatory cells, trophozoites, or altered keratocytes) were present. Normal keratocyte nuclei and the anterior corneal mosaic, readily imaged by scanning slit confocal microscopy of the normal cornea, were noticeably absent. Subsequent corneal biopsy confirmed the diagnosis of Acanthamoeba keratitis.

Clinical microscopy of the cornea utilizing optical sectioning and a high-numerical-aperture objective.

A doublet contact element was added to a long-working-distance objective to increase the numerical aperture to 0.75 and to maintain the focus during in vivo examination of the eye. Optical sectioning by use of confocal slits permits visualization of weakly scattering structures within the cornea. With photographic film and a 1/60-s exposure time to limit the effect of eye movement, an effective optical section half-thickness of approximately 20 microns was realized. Structures observed in the cornea include epithelial cells (surface, wing, and basal cells), nerve-fiber bundles in the subepithelial region, keratocytes and inflammatory cells in the stroma, and endothelial cells.

Multiple myeloma presenting as vortex crystalline keratopathy and complicated by endocapsular hematoma.

The crystalline keratopathy of multiple myeloma may involve the corneal epithelium, but has not previously been described in a vortex epithelial distribution. Endocapsular hematomas have been described in the period immediately after extracapsular cataract extraction, but not later on or in association with systemic disease. We report a pseudophakic patient who developed a vortex epithelial crystalline keratopathy as a presenting sign of multiple myeloma, and who subsequently developed a spontaneous endocapsular hematoma.

In vivo measurement of posterior chamber intraocular lens decentration and tilt.

We report what to our knowledge is the first extensive in vivo clinical study of intraocular lens decentration and tilt. Measurements of posterior chamber intraocular lenses, all implanted by the same surgeon in 89 eyes, showed that decentration and tilt consistently differed between right and left eyes. Lenses tended to decenter superotemporally and tilt with their superonasal edges tipped forward. Decentration magnitude relative to the cornea light reflex axis and line of sight averaged 0.64 mm, with decentration increasing slightly with increased axial length. Average tilt was 6.75 degrees, and the average tilt-induced astigmatism was 0.27 diopter. Tilt magnitude decreased with increased axial length, as did tilt-induced astigmatism and plus sphere.

Stevens-Johnson syndrome with associated nasolacrimal duct obstruction treated with dacryocystorhinostomy and Crawford silicone tube insertion.

Although Stevens-Johnson syndrome (SJS) has long been recognized as a cause of punctal and canalicular obstruction, nasolacrimal duct obstruction secondary to SJS is rare and has not been reported in the ophthalmologic literature. Keratoconjunctivitis sicca, entropion, and trichiasis are well-known complications of SJS that may require measures to supplement or preserve tears. Lacrimal drainage system obstruction may occasionally occur in the face of relatively normal tearing, resulting in clinically significant epiphora. We report two cases of SJS, one associated with epidemic keratoconjunctivitis, that led to nasolacrimal duct obstruction and canalicular obstruction or stenosis. Epiphora and, in one case, dacryocystitis, necessitated dacryocystorhinostomy and Crawford tube insertion.

Benign mixed tumor of the palpebral lobe of the lacrimal gland. Clinical diagnosis and appropriate surgical management.

The treatment of suspected benign mixed tumor (pleomorphic adenoma) of the lacrimal gland consists of wide local surgical excision of the tumor and its capsule in their entirety. The tumor should be approached routinely via a lateral orbitotomy to provide maximal exposure and allow complete removal of the lesion. However, if clinical and radiographic evidence indicates a far anterior location implying an origin in the more superficial palpebral lobe, an anterior transcutaneous approach is advantageous and preferred. The authors report an adult case of an anteriorly located benign mixed tumor of the palpebral lobe of the lacrimal gland. The authors reviewed the characteristic clinical, echographic, and computed tomographic (CT) features, offered a differential diagnosis, and described surgical removal using a cryoprobe via an anterior lid approach. An awareness of the distinctive clinical and diagnostic features of benign mixed tumor of the palpebral lobe should help to avoid the complications that ensue from an incisional biopsy or piecemeal resection through the lid, and also to avoid the need for more extensive surgery for removal of residual or recurrent tumor.

Acanthamoeba keratitis. A review of the literature.

Acanthamoeba is a free-living ubiquitous ameba that is responsible for a small but increasing number of cases of keratitis. The infection is associated with minimal corneal trauma and soft contact lens wear. It typically presents as a unilateral central or paracentral corneal infiltrate, often with a ring-shaped peripheral infiltrate. The lesion is often confused with fungal, bacterial, or herpetic keratitis. Successful therapy hinges on early recognition and aggressive therapy with appropriate topical antiamebic medication often in conjunction with penetrating keratoplasty. Thirty-five cases from the world literature are reviewed.

The macular pigment. I. Absorbance spectra, localization, and discrimination from other yellow pigments in primate retinas.

The nonbleaching yellow pigments of the primate fovea were studied by microspectrophotometry (MSP). Retinas fixed with glutaraldehyde/paraformaldehyde mixtures retained yellow pigments with absorbance spectra very similar to those recorded by MSP in fresh retinas. This allowed the authors to prepare retinal sections for localization of the pigments. The spectrum of the macular pigment in fixed tissue is shifted slightly (about 6 nm) toward longer wavelengths, with maximum absorbance at 460 nm. Two short-wavelength yellow pigments also have been identified, with absorbance maxima at 410 nm ( P410 ) and 435 nm ( P435 ), respectively. All three yellow pigments are present in the fovea. The short-wavelength pigments are detected more easily outside the central foveal region because the macular pigment does not obscure them there. They are especially apparent when the MSP beam is confined to the outer nuclear layer or the inner segment layer of retinal sections. The macular pigment is most dense in the fiber layers (receptor axon layer and inner plexiform layer); its density declines markedly with retinal eccentricity. The maximal absorbance of P410 and P435 is usually lower than that of the macular pigment in the central fovea, but their densities and relative proportions change more gradually with eccentricity. Consequently, their maximal absorbance is higher than that of the macular pigment outside the foveal center. The P410 and P435 pigments may be two different oxidation states of one or more respiratory hemoproteins. Commonly used procedures for estimating the absorbance spectrum of the macular pigment by comparing the foveal center with a parafoveal region may be influenced by the amounts and the oxidation states of the short-wavelength pigments in the living eye.

The macular pigment. II. Spatial distribution in primate retinas.

The spatial density distribution of macular pigment in primate retinas was described by two-wavelength microdensitometry of retinal sections. The macular pigment is most dense along the path of the receptor axons in the center of the fovea. Another band of high density is present in the inner plexiform layer in many retinas. The density in both fiber layers declines to low, relatively constant levels within 1 mm eccentricity. Both the total retinal density of macular pigment and the contributions of subsets of the retinal layers were estimated by integrating along the path of light traversing the retina from the vitreal surface to the outer segments. The integrated densities were measured at several eccentricities to establish the profile of macular pigment density along a diameter through the fovea. The macular pigment profile was unimodal in some cases and trimodal in others. The main central peak always occurred in the center of the fovea. The total retinal density of the central peak ranged from 0.42-1.0 absorbance. Most of the pigment is interposed between the outer segments and the stimulating light and is effective as a visual filter. The macular pigment is dichroic, with the major axis of absorption oriented tangential to a circle centered on the fovea. This is consistent with commonly accepted explanations of Haidinger 's brushes.