Wide-field Specular Microscopy Research Articles

A Comparison of the Efficacy and Toxicity of and Intraocular Pressure Response to Viscous Solutions in the Anterior Chamber

An intraocular-lens abrasion test, vital dye staining, and scanning electron microscopy were used for an in vitro comparison of endothelial protection offered by four viscous solutions of 1% sodium hyaluronate (Healon), 3% sodium hyaluronate (AmVisc), 4% chondroitin sulfate (Viscoat), and 2% methylcellulose. Wide-field specular microscopy with analysis of endothelial cell density and morphologic evaluation, pachymetry, and intraocular pressure measurements were also used to study the toxicity of the viscous solutions in an in vivo cat model with and without anterior chamber washout. All four solutions provided complete endothelial protection from mechanical trauma. Endothelial cell density and morphologic nature were unaffected during the in vivo toxicity study. A mild increase in intraocular inflammation occurred at one and two days after intraocular injection with all four viscous solutions. Intraocular pressure elevations peaked within four hours after instillation of the viscous solutions and were significantly reduced by anterior chamber washout.

Ultrastructural Correlation of Specular Microscopy in Retinoblastoma

A patient with monocular retinoblastoma was examined with the wide-field specular microscope before undergoing enucleation. An unusual image on the corneal endothelium consisted of irregular oval dark structures within which bright reflections formed a lacy network. Light and electron microscopy confirmed these structures to be clusters of retinoblastoma cells adherent to the endothelium. These findings suggest that the specular microscope may aid in the diagnosis of intraocular tumors.

Clinical use of the wide field specular microscope.

The Pocklington (Keeler-Konan) wide field specular microscope has been in use for 18 months at the Corneal Diseases Unit, The Royal Victorian Eye and Ear Hospital, Melbourne. In this study, the microscope has been applied clinically to assess the state of the corneal endothelium and to evaluate comparative endothelial cell density and morphology in certain anterior segment microsurgical procedures. The clinical conditions studied are primary posterior chamber intraocular lens implantation, secondary intraocular lens implantation, intraocular lens exchange, and penetrating keratoplasty.

Relocation of posterior corneal rings in clinical wide field specular microscopy.

A clinical study of posterior corneal rings in human eyes was undertaken using the Pocklington (Keeler-Konan) contact wide field specular microscope designed by Sherrard. The method used to reproduce identical posterior corneal rings in the same human cornea, in vivo, using the contact wide field specular microscope camera, without the aid of a contact lens, is described. The technique enables the clinician to relocate and evaluate a selected area of human endothelial cells in the same eye.

Corneal endothelial morphology after anterior chamber lens implantation.

The morphologic features of the corneal endothelium were investigated by means of regional wide-field specular microscopy and computer-assisted morphometry in 13 eyes of nine patients who had undergone intracapsular cataract extraction with anterior chamber lens implantation more than one year previously. The endothelial cells in these patients demonstrated a significant increase in cellular elongation and the coefficient of variation in mean cell area and a significant decrease in the percentage of hexagonal endothelial cells when compared with age-matched controls (ten eyes of ten patients). The clinical implications of these long-term morphologic changes are unknown, but the changes may be indicative of an unstable endothelium or may be an early sign of continuing cell loss.

Corneal endothelium after photocoagulation in diabetic patients.

The corneal endothelium was photographed through a wide-field specular microscope in 38 eyes, in 20 successive diabetic outpatients receiving laser therapy because of underlying proliferative or background retinopathy. Areas of 100 individual endothelial cells from each central cornea were analysed using a digitizer. No statistically significant correlations were observed between mean cell areas or standard deviations of mean and total amount of previous laser energy received. Laser therapy or the type of diabetes did not seem to cause statistically significant changes in the endothelial cell areas examined.

Pump Function of the Human Corneal Endothelium: Effects of Age and Cornea Guttata

The specific binding of tritiated ouabain to endothelial Na/K ATPase was used to quantitate the density of pump sites in the human corneal endothelium. Donor eyes, unsuitable for use in keratoplasty, were obtained from the Wisconsin Lions Eye Bank. The endothelium of each donor eye was examined using wide-field specular microscopy, and the specular micrographs were traced and digitized for the determination of cell density. Ouabain binding was measured in matched pairs of isolated endothelial sheets. A total of 26 pairs of donor eyes, ranging in age from 11 through 91 years, were studied. Twenty pairs, determined to have normal endothelia, were found to have a constant pump site density which was independent of donor age. Six donor pairs had moderate guttata; in this group pump site density was significantly increased. These results indicate that, although pump site density is normally constant in the human corneal endothelium, conditions which increase endothelial permeability, such as guttata, can cause a compensatory increase in pump site density and presumably pump function.

Biomicroscopy of Surface Deposits Resembling Foreign-Body Giant Cells on Implanted Intraocular Lenses

Deposits resembling foreign-body giant cells, which can be seen on specular reflex slit-lamp examination, were studied in vivo with a wide-field specular microscope using a low-power dipping cone lens in three cases of posterior chamber lens implantation. The deposits seen as iris pigment on routine examination showed two types of cell-like figures: round, bipolar or ameboid small figures with long branching processes and round, oval, or bizarre large figures. The large cell type had the pigment particles at the central or paracentral area and vacuole-like structures adjacent to the pigment particles. The specular photomicrographic characteristics were similar to those of fibroblast-like cells and foreign-body giant cells, which had been shown on the surfaces of extracted implanted intraocular lenses by the lens implant cytology technique.

Effects of Intraocular Irrigating Solutions on the Corneal Endothelium After in Vivo Anterior Chamber Irrigation

We used wide-field specular microscopy and corneal pachymetry to evaluate the effect of anterior chamber irrigation with BSS and BSS Plus on the corneal endothelium of cats. Endothelial changes were quantitated by computerized morphometric analysis of individual cells. After short-term (15 and 30 minutes) and long-term (one and two hours) irrigation, endothelial cell density remained unchanged. Corneal thickness increased significantly in the BSS group after one hour of irrigation. BSS Plus caused minimal changes in endothelial morphologic characteristics regardless of the irrigation time. By comparison, BSS caused a significant increase in the coefficient of variation of cell area (polymegethism) and a decrease in the percentage of hexagonal cells (pleomorphism). These changes were more prominent after prolonged irrigation. The morphologic changes caused by BSS irrigation are indicative of a stressed endothelial monolayer that may be more susceptible to additional surgical trauma.

Identification of Intraocular Tumors by Specular Microscopy

Five patients with confirmed diagnoses of intraocular tumors and anterior chamber extension were examined with a wide-field specular microscope. Uniquely shaped dark areas seen on the endothelial surface could be readily distinguished from inflammatory cells by their size and shape. These structures were often associated with a surrounding bright reflection similar to that produced by pigment. The cellular morphology provided by specular microscopy offers the potential for differentiating neoplastic from inflammatory processes in the anterior chamber.

BOOK REVIEWS

Book reviewed in this article:Mayer D J: Clinical Wide‐Field Specular MicroscopyLuntz M, Harrison R & Schenker H I: Glaucoma SurgeryBreinin G M & Siegel I M: Advances in Diagnostic Visual OpticsHelveston E M & Ellis F D: Pediatric Ophthalmology PracticeStone, Jonathan, Dreher, Bogan & Rapaport David H.: Development of visual pathways in mammalsHilfer S R & Sheffield J B (eds): Molecular and Cellular Basis of Visual Acuity

In vivo Corneal and Conjunctival Epithelial Nuclear Stain

Epithelium plays a very important structural and functional role in the cornea and conjunctiva. Evaluation of the epithelium is the first step in diagnosing many pathologic states. We have developed a new technique for the in vivo staining of nuclei of corneal and conjunctival epithelium in rabbits and guinea pigs. Several drops of 0.01%, 0.1%, 0.25%, 0.5%, or 1.0% toluidine blue or 1.0% methylene blue were applied to the conjunctival sac to stain epithelial cells. The cells picked up the vital dye within 5 minutes and could be photographed at 30X with the Keeler-Konan wide-field specular microscope. Cells and nuclei were clearly observable. Photographs could be further enlarged to enhance details. Wash out time was rapid and no toxic effects were observed. This technique adds a new dimension to the study of epithelium in normal and pathologic states in experimental animals. This technique may also be applicable to human eyes for discerning such diseases as carcinoma, herpes simplex, or superior limbic keratoconjunctivitis.

The Effect of Silicone Oil on the Cornea

Intraocular silicone oil tamponade is being used with increasing frequency as an adjunct to conventional vitrectomy techniques in the treatment of proliferative vitreoretinopathy. When used in patients with aphakia, corneal decompensation is a common long-term complication. In this study, we evaluated the clinical and morphologic changes that occurred in the corneas of 14 rabbits and seven cats when the anterior chamber was filled with silicone oil. Within six days, wide-field specular microscopy showed a 40% reduction in endothelial density in the area of the silicone oil bubble in both groups. Progressive stromal thinning occurred in the rabbit cornea, with gradual development of a retrocorneal membrane at the junction of silicone-endothelial cell contact. In contrast, persistent stromal edema, peripheral vascularization, irregular plaques on the endothelium, and eventual epithelial ulceration and corneal thinning occurred in cat eyes.

Clinical specular microscopy: the Australian experience.

It is almost one year since the Corneal Diseases Unit of The Royal Victorian Eye and Ear Hospital began preliminary evaluation of the Pocklington Keeler-Konan Wide-Field Specular Microscope. With this instrument, approximately one square millimetre of living human corneal endothelial cells can be observed and photographed. This relatively large area gives a far more valid assessment of endothelial cell morphology and numbers than was possible with narrow field instruments. Reproducible lines enable the relocalization of the same area of endothelium. Observations of endothelial cells have been made in health and disease, including eyes with corneal dystrophy, following cataract surgery with and without intraocular lens implantation, corneal grafting, and after the use of Healon in the anterior chamber.

Specular Microscopy of Hard Contact Lens Wearers

Wide-field specular microscopy, slit-lamp examination, and pachometry were performed on 22 successful hard contact lens wearers and 22 controls matched for age, race, sex, and refractive error. A minimum of 600 cells per control and 1200 per contact lens wearer were manually digitized from the specular photomicrographs. Frequency distributions of cell areas were compared between the two groups using the parameters of mean, median, standard deviation, coefficient of variation, skewness and kurtosis. Slit-lamp examination was normal and there was no significant difference in corneal thickness between the patient group and the control group. Comparison of mean, median, and standard deviation also revealed no significant difference, but skewness (P < .001), kurtosis (P < .001) and coefficient of variation (P < .004) were greater in the hard contact lens wear group. Hard contact lens wearing time correlated with increasing pleomorphism (P < .05). Specular microscopy also revealed morphologic changes including deep stromal striae, intra- and extracellular “blackout” areas, and clustering of extremely small and large cells. The possible relationship between endothelial hypoxia and structural stromal changes are discussed.

Diurnal Variation in Corneal Endothelial Morphologyp

Transient changes in the corneal endothelium were the earliest detectable response to low atmospheric oxygen in experimental animals. Similar changes have been reported after hard and soft contact lens wear. We describe widespread transient cell changes by wide-field specular microscopy in the normal corneal endothelium after 12 hours of a light eye patch. The relative anoxia of lid closure during normal sleep appears to be the cause of observable changes. This observation questions the safety of extended wear contact lens over a prolonged period of time, and its significance to age-related endothelial cell density reduction and cornea guttata remains to be seen.

Corneal endothelial cell losses following implantation of Simcoe posterior chamber lenses

Using the Roberts and Koester wide field specular microscope 42 eyes with cataract were examined before and after implantation of Simcoe posterior chamber lenses. A 9.7% loss of endothelial cells was found postoperatively.

Corneal Endothelial Cell Loss, Cystoid Macular Edema, and Iris-supported intraocular Lenses

Endothelial cell loss, persistent cystoid macular edema and a chronic low-grade uveitis may complicate intracapsular cataract extraction combined with iris supported intraocular lenses. Clinical examination of 19 eyes of 17 patients, at 1.1 to 5 years after cataract surgery, and correlation with wide field specular microscopy and fluorescein angiography, documents this problem. The mean central corneal endothelial cell count was 497 cells/mm2 (standard deviation, 119). In ten cases, focal edema was localized to the corneal periphery. Cystoid macular edema was present in all but one case. Intermittent cornea/ implant touch or low-grade intraocular inflammation, possibly from iris/implant contact, may explain the natural history of the endothelial cell loss and cystoid macular edema. Monitoring endothelial cell counts and macular function in patients with iris-supported implants may afford the early recognition of this problem. In such cases, early implant removal may alter the natural history and preserve corneal and macular function.

The Fellow Eye of Patients with Aphakic Bullous Keratopathy

The fellow normal-appearing eyes of 23 patients with unilateral aphakic bullous keratopathy were examined by wide-field specular microscopy and pachymetry. All patients had: pseudophakic or aphakic bullous keratopathy in one eye; unoperated fellow eye on no medication; no other ocular disease; and no endothelial guttata seen by slitlamp biomicroscopy or specular microscopy. Three of 23 patients had endothelial cell counts less than 1,000 cells/mm2. There was no correlation between cell density and corneal thickness, but a negative correlation existed between age and endothelial cell density. Preoperative specular microscopy is indicated in patients who have developed bullous keratopathy in the fellow eye after cataract surgery.

Endothelial Guttata and Facility of Aqueous Outflow

Thirty-eight eyes of 22 patients with corneal endothelial guttata were examined by slit lamp, tonometry, tonography, and wide-field specular microscopy. The mean value for facility of outflow (C55) was 0.23, and it was not statistically different from reported values for a normal population. Also, there was no correlation between extent of guttata as seen with wide-field specular microscopy and facility of outflow. Thus, contrary to a previous report, endothelial guttata does not seem to predispose to impaired facility of outflow.