Confocal microscopy in cornea guttata and Fuchs'' endothelial dystrophy

AIMS: To report the appearances of cornea guttata and Fuchs' endothelial dystrophy from white light confocal microscopy. METHODS: Seven eyes of four consecutive patients with cornea guttata were prospectively examined. Of the seven eyes, three also had corneal oedema (Fuchs' dystrophy). In vivo white light tandem scanning confocal microscopy was performed in all eyes. Results were compared with non-contact specular microscopy. RESULTS: Specular microscopy was precluded by corneal oedema in one eye. In the remaining six eyes, it demonstrated typical changes including pleomorphism, polymegathism, and the presence of guttae appearing as dark bodies, some with a central bright reflex. In all seven eyes, confocal microscopy revealed the presence of round hyporeflective images with an occasional central highlight at the level of the endothelium. Changes in cell morphology and size were readily appreciated. CONCLUSION: By comparison with specular microscopy, the hyporeflective images with an occasional central highlight seen on confocal microscopy are consistent with the presence of guttae. Confocal microscopy may confirm the diagnosis of cornea guttata and Fuchs' endothelial dystrophy by demonstrating the presence of guttae. This technique is especially valuable in cases of corneal oedema, where specular microscopy may fail to visualise the endothelium. However, specular microscopy should remain the method of choice to evaluate the endothelium, principally because it is easier to use.     

Central corneal thickness and intraocular pressure measures in human corneas with endothelial guttata: an observational quality control study

Purpose: The aim of the present study was to assess central corneal thickness (CCT) and intraocular pressure (IOP) in eyes where the corneas were affected by different degrees of severity of endothelial pseudo‐guttata or guttata. Methods: In a prospective, case series observational study, non‐contact tonometry and non‐contact specular microscopy (NCSM) with pachymetry for central corneal thickness measures were undertaken as routine procedures on predominantly older patients without a history of corneal problems or contact lens wear. For those showing any signs of corneal endothelial abnormalities, images of the central cornea endothelium were further processed to measure the area (as a percentage) occupied by the guttata. Results: Abnormal endothelial images were obtained from 43 patients (seven with bilateral changes) with an average age of 67.5 years. Between 1.5 and 54.9 per cent of the endothelial images were affected by guttata, which were assigned grade 1 (20 eyes), grade 2 (18 eyes) or grade 3 (11 eyes). When assessed by grade, the central corneal thickness increased and the measured IOP decreased as the guttata became more numerous and confluent. Regression analyses revealed only a weak association between central corneal thickness (p = 0.044, r = 0.149) or the measured IOP (p = 0.090, r = ‐0.244) and the extent of the guttata (percentage). With the apparently contrasting IOP and central corneal thickness effects, no significant IOP‐CCT relationship was noted (p ≥ 0.268, r ≤ 0.160). Conclusions: Where corneas have mild‐to‐modest non‐dystrophic endothelial guttata, there may be a less predictable effect of corneal thickness on the outcome of tonometry.     

Prevalence of primary cornea guttata and morphology of corneal endothelium in aging Japanese and Singaporean subjects

The purpose of the present study was to examine, in the aging people, racial and gender differences in the morphology of corneal endothelium as well as the incidence of cornea guttata in two Asian subject groups, one in Singapore and the other in Japan. Four hundred and sixty-five Chinese Singaporeans and 299 Japanese subjects (residents of Monzen-machi, Ishikawa Prefecture) aged 50 years and older were recruited for the study. Corneal endothelial abnormalities were diagnosed with slit-lamp biomicroscopy and specular microscopy. Primary cornea guttata appeared as beaten metal appearance in slit-lamp images and dark regions in specular images. In addition to cornea guttata, corneal endothelial morphology was also analysed with specular microscopy. The mean cell density was 2,808/mm(2) in the Japanese subjects which was significantly higher than the 2,718/mm(2) seen in the Singaporeans (p < 0.001). The incidence of cornea guttata was significantly higher in the Singaporeans than in the Japanese individuals and also higher in women than in men of both racial groups. These differences support not only a racial and a gender factor but also a possible environmental influence.     

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.     

The effect of liquid silicone on the corneal endothelium in rabbits

Specular microscopic and histopathologic findings in the corneal endothelium were compared after the injection of liquid silicone into the anterior chamber of both eyes in 15 rabbits. The findings demonstrated serious damage to the endothelium in the area of contact of liquid silicone with the posterior surface of the cornea and disclosed some problems in the interpretation of specular microscopic findings. An abnormal endothelial mosaic can be probably found even in a zone of preserved intercellular borders or in a zone with a relief of the bases of extinct endothelial cells.     

Twenty-three cases of primary cornea guttata

PURPOSE: To evaluate the clinical aspects of patients with primary cornea guttata and the specular microscopical findings/morphology in their corneal endothelial cells. METHODS: Twenty-three patients consulting Kanazawa Medical University Hospital or related hospitals in Ishikawa or Fukui prefectures and diagnosed with primary cornea guttata by slit-lamp examination underwent an analysis of their clinical features and corneal endothelial cells. RESULTS: Most cases were middle-aged to elderly women. None of them complained of visual impairment due to cornea guttata. The 46 eyes of these cases were included in this study. Specular microscopical findings revealed that the size and density of dark areas varied, with asymmetry noted in some cases. The parameters of the endothelial cells comprising mean cell area, the proportion of hexagonal cells, and the coefficient of variation, were almost within normal limits except for 1 eye of a 79-year-old man who was speculated to be at an early stage of Fuchs endothelial corneal dystrophy. Three cases had undergone cataract surgery, but did not show significant changes in endothelial morphology before and after surgery. In a statistical study on endothelial cell morphology, cell parameters except for minimal cell area correlated significantly with age. Although the density and size of dark areas correlated with each other, neither correlated with any of the cell parameters. CONCLUSION: Cornea guttata does not lead to visual impairment or abnormalities in corneal endothelial cell parameters except for a small number of cases that must be considered to be at an early stage of Fuchs dystrophy.     

A comparison of corneal endothelial morphology in cornea guttata, Fuchs' dystrophy and bullous keratopathy

Changes on corneal endothelial specular microscopy were compared in 14 patients with cornea guttata, 4 patients with Fuchs' corneal dystrophy and 19 patients with various forms of bullous keratopathy. The patients with cornea guttata showed well marked guttae 1 to 6 endothelial cells in diameter in the endothelial mosaic and in the relief mode while the endothelial mosaic was usually otherwise within normal limits. In 2 patients with Fuchs' dystrophy the endothelium could be examined, showing gross guttae but a few areas of relatively normal endothelial cells. The unaffected eye of 3 other patients showed findings similar to cornea guttata, but with some reduction in endothelial cell count in 2 patients. The patients with bullous keratopathy fell into 2 groups, one with gross reduction in cell count in a markedly abnormal endothelial cell mosaic, the other a mixed group with moderate reduction in cell count and numerous guttae. Some miscellaneous cases included one of aphakic peripheral bullous keratopathy, one associated with cyclitis and aphakia and 2 with idiopathic non-surgical bullous keratopathy. We believe the corneal endothelium is not grossly abnormal away from the guttae in Fuchs' dystrophy, but the gross guttata formation determines the endothelial dysfunction.     

Mathematical projection model of visual loss due to fuchs corneal dystrophy

PURPOSE. To devise a mathematical disease classification model for eyes with primary guttata cornea, on the bases of endothelial loss trajectory and probability of advanced disease. METHODS. A series of 1971 patients (3281 eyes), some with and some without guttata corneas, undergoing specular microscopy were retrospectively reviewed. The eyes were classified into four stages; stage 0, without guttae; 1, guttata cornea without edema; 2, mild Fuchs' corneal dystrophy (FCD); and 3, severe FCD, according to clinical records, and patient age and corneal endothelial cell density (ECD) were plotted. Nonparametric density smoothing was used to create a contour map, and a best-fit curve for ECD loss was calculated. The relation between ECD decrease rate and the stages were evaluated. RESULTS. Endothelial decrease rate in stage 0 was 0.44%/year, which was compatible with that of normal eyes reported in previous studies. Decrease rates of stages 1, 2, and 3 were 0.81%, 2.65%, and 3.08%/ year, respectively. The age-ECD loss curves of 1.40%/year (ECO(1.4)) and 2.00%/year (ECO(2.0)) further divided stage 1 into three subgroups; stage 1a, asymptomatic guttata cornea; 1b, borderline guttata cornea; and 1c, pre-FCD. The ECO(2.0) cutoff line differentiated eyes with FCD from those without edema with a sensitivity and specificity of >90%. Stage 1c eyes were below ECO(2.0) and had a decrease rate as high as FCD. CONCLUSIONS. This mathematical model can be used to predict the prognosis of patients with primary guttata cornea.     

Comparison of confocal biomicroscopy and noncontact specular microscopy for evaluation of the corneal endothelium

PURPOSE: To compare the clinical efficacy of confocal biomicroscopy with that of noncontact specular microscopy for the evaluation of the corneal endothelium. METHODS: The corneal endothelium was examined in 14 normal subjects (28 eyes) and in 6 patients (11 eyes) with Fuchs corneal endothelial dystrophy using a noncontact specular microscope (SP-2000P, Topcon, Japan) and a confocal biomicroscope (ConfoScan, Tomey, Japan). The images and the calculated densities of corneal endothelial cells obtained by the 2 techniques were compared. RESULTS: For normal subjects, the images of corneal endothelial cells obtained by the 2 techniques were almost identical, although the density of these cells determined by confocal biomicroscopy (2916 +/- 334 cells/mm2) was slightly higher than that determined by noncontact specular microscopy (2765 +/- 323 cells/mm2). In contrast, whereas clear images of corneal endothelial cells, allowing the determination of cell density, were obtained for all 11 eyes of the patient group by confocal biomicroscopy, clear images were obtained for only 4 of these 11 eyes (36.4%) by noncontact specular microscopy. CONCLUSION: Both noncontact specular microscopy and confocal biomicroscopy revealed the shapes and number of endothelial cells in the normal cornea. However, for corneas with Fuchs dystrophy, clear images were obtained only by confocal biomicroscopy. Confocal biomicroscopy is thus an effective tool for evaluation of the diseased corneal endothelium.     

The preoperative assessment of the corneal endothelium

The ability of the cornea to maintain its transparency after surgery depends primarily upon the integrity of the corneal endothelium and in corneal grafting this is important for both donor and recipient eyes. The corneal endothelium may be significantly affected in various conditions of the anterior segment, especially if these exist over a considerable period of time. These conditions include superficial keratopathy, long-term contact lens wear, cornea guttata and low-grade anterior uveitis, especially chronic cyclitis which may be almost imperceptible clinically. The suitability of such corneas for use as donor material as well as the response of the eyes to anterior segment surgery can be assessed by specular microscopy and this may become even more important in the future as long-term contact lens wearers become more numerous in the community.     

Corneal endothelial damage after trabeculectomy with mitomycin C in two patients with glaucoma with cornea guttata

PURPOSE: To report two patients with glaucoma who exhibited severe damage to the corneal endothelium after a trabeculectomy with mitomycin C (MMC). METHODS: This study includes clinical histories and specular microscopic pictures of the cases. RESULTS: Both patients were middle-aged women, underwent trabeculectomy with MMC, had moderate to severe cornea guttata preoperatively, and developed a shallow to flat anterior chamber, classified as grade 2 according to Spaeth early in the postoperative period. Stromal opacity caused by corneal edema associated with severe Descemet's membrane folds appeared within 2 to 5 days in both cases. The density of the corneal endothelium was decreased on specular microscopic examination. The severe corneal endothelial damage seen after the trabeculectomy with MMC was likely owing to a combination of the preexisting cornea guttata, the flat anterior chamber, and possibly the administration of MMC. CONCLUSION: Severe endothelial damage after trabeculectomy with MMC may occur in patients with glaucoma and associated cornea guttata. The use of tight sutures on the scleral flap or a modified operative method, nonpenetrating trabeculectomy, may be effective in preventing a shallow to flat anterior chamber postoperatively.     

Differentiation and assessment of corneal endothelial changes associated with diseases of the anterior segment of the eye

Recent work has shown changes in the corneal endothelium accompanying corneal epithelial disease and anterior uveitis. It is important to differentiate these acute changes from other changes such as guttatae or corneal pigment deposition and to assess the magnitude of their effect upon the corneal endothelium. We have used specular microscopy to study changes in the corneal endothelium and Descemet's membrane and to study deposits on the back of the corneal endothelium and correlate them with changes in the endothelium by the use of conventional specular microscopy and by relief images which give a three dimensional view of the area concerned. This has particularly been applied to the conditions of superficial punctate keratopathy, keratoconjunctivitis sicca, corneal abrasions and exposure keratopathy, iritis and cyclitis, pseudoexfoliation of the lens capsule, anterior segment pigment dispersal syndrome, bullous keratopathy as well as corneal guttatae and pigment granules on the posterior cornea. Preendothelial lesions have been distinguished from endothelial and retrocorneal lesions by this technique aiding elucidation of the state of the endothelium. The changes which we noted occurred either at the level of Descemet's membrane (including formation of small rounded dark blebs less than one cell in diameter, larger blebs one to three cells in diameter, and guttatae, usually larger than the foregoing and sometimes very numerous), or at the level of the posterior endothelial surface (including small shiny nodular deposits, often numerous, due to pigment granules, and keratitic precipitates and inflammatory debris, the former usually large and the latter smaller, more irregular and sometimes very numerous). The differentiation and assessment of these various changes are discussed.     

Non-invasive assessment of the donor corneal endothelium using ocular redox fluorometry.

AIMS: To investigate the usefulness of ocular redox fluorometry for evaluating donor corneal endothelial viability. METHODS: Corneas from 42 recipients of penetrating keratoplasty and four donor corneas were examined by ocular redox fluorometry. Autofluorescence from reduced pyridine nucleotides (PN) and oxidised flavoproteins (Fp) of the human corneal endothelium were measured non-invasively, and the PN/Fp ratio was used as a tissue metabolic indicator. Specular microscopy and electron microscopy were also performed. RESULTS: Both the quality of specular microscopic image and the PN/Fp ratio were significantly correlated with the degree of corneal endothelial damage determined by histological examination. Corneas with poor specular microscopic image showed significantly decreased PN/Fp ratio compared with corneas with good or fair specular images (p = 0.041 and 0.027, respectively). The PN/Fp ratio increased in corneas with mildly damaged endothelium but decreased in corneas with severely damaged endothelium determined by histological examination. Evaluation of corneal endothelium by combination of specular microscopy and ocular redox fluorometry showed excellent association with that of histopathological examination (p < 0.0001). CONCLUSION: Ocular redox fluorometry is useful for assessing donor corneal endothelial viability. Combination of ocular redox fluorometry and specular microscopy may increase the ability of donor cornea selection.     

Corneal guttata associated with the corneal dystrophy resulting from a betaig-h3 R124H mutation

AIMS: To investigate the frequency of corneal guttata in patients with a corneal dystrophy resulting from an Arg124His (R124H) mutation of betaig-h3 gene. METHODS: Slit lamp examination was performed on 30 eyes with corneal dystrophy from a genetically confirmed betaig-h3 R124H mutation and on 50 age matched control eyes. The stage of the corneal dystrophy was classified as stage 0, I, or II and the degree of guttata was classified as none, mild, or severe. Specular microscopic examinations were performed to evaluate the morphology of the corneal endothelium. RESULTS: Slit lamp examination disclosed the presence of corneal guttata in 21 eyes (70%) of the 30 eyes with the corneal dystrophy, but in only one (2%) of the 50 eyes in the age matched control group (p<0.001, chi(2) with Yates's correction). Of the 12 eyes with stage I betaig-h3 R124H corneal dystrophy, seven had no corneal guttata and five had a mild degree of guttata. Of the 18 eyes with stage II, the degree of guttata was none in two, mild in nine, and severe in seven. The degree of corneal guttata was significantly related to the stage of the corneal dystrophy (p<0.0001, Kruskul-Wallis test ANOVA on ranks). There was no significant differences between eyes with betaig-h3 R124H corneal dystrophy and normal eyes in cell density, coefficient of variation, and cell hexagonality of corneal endothelium. CONCLUSION: Corneal guttata are one of the characteristics of the corneal dystrophy resulting from betaig-h3 R124H mutation.     

Non-contact specular microscopy of human corneal endothelium

The non-contact specular microscope enables a large area of the corneal endothelium to be examined and photographed without any risk of traumatizing the anterior surface of cornea. This non-contact technique is described in detail. Standard deviation of the relative difference between two independent estimates of central endothelial density from 24 eyes was 3.7%. Standard deviation of the relative difference between counts from left and right eyes from 57 subjects was 4.7%. A significant negative correlation between age and endothelial cell density was found (r = -0.59, P less than 0.001, n = 76). The interindividual variation in cell densities was found to be larger in the old age group, indicating that cell loss during aging varies among different individuals.     

The corneal endothelium of diabetic patients. A study using specular microscopy

As the endothelial cells of the human cornea cannot perform mitosis, any metabolic alteration that destroys the cells should result into a decrease in cell density. This study was designed to demonstrate this phenomenon in diabetics as we know that diabetes alters endothelial cells, capillaries at least. On the assumption that capillary endothelium has the same mesodermal origin and almost the same metabolic function as the corneal endothelium, we tried to verify whether the corneal endothelium from diabetic subjects differs from non diabetic controls. As corneal endothelium can be studied in vivo by specular microscopy, it was interesting to verify whether this method could provide evidence of the conditions of the endothelial cells in the diabetic subject. Our study in specular microscopy involved 101 cases. We found slightly inferior values of the corneal endothelial cells density in diabetic subjects compared to the control subjects but no correlation between the values of endothelial cell density and the various parameters in diabetic patients: age, duration of diabetes, corneal thickness. This is correlated to other studies in which the morphology of endothelial cells differed between diabetic and non-diabetic subjects. We concluded that diabetes alters but does not significantly destroy the corneal endothelial cell. This result must be taken into account in corneal surgery as the diabetic cornea is a high risk cornea.     

Endothelial cell density determined by specular microscopy and scanning electron microscopy.

Human eyes were photographed with a specular microscope and later examined wit a scanning electron microscope. Corneas from patients undergoing corneal transplantation in whom we were able to obtain preoperative specular micrographs were similarly analyzed. An attempt was made to correlate the counts obtained with both microscopic techniques by determining the amount of shrinkage the cornea undergoes while being processed for SEM. All specimens were counted with a planimeter. We found that the specular microscope adequately analyzes the endothelial cell density in the central and paracentral cornea of a normal eye, but because of its small sampling area specular microscopic counts are subject to significant error when dealing with nonhomogeneous populations such as postoperative cases. We found the peripheral corneal endothelial density to be less than the central endothelial density. Furthermore, we found that we could maximize the accuracy of counting by using a variable frame in a nonhomogeneous population, counting a minimum of four photographs per specimen, analyzing different areas, and analyzing larger areas.     

The relation between corneal autofluorescence,endothelial cell count and severity of the diabetic retinopathy

We measured the corneal autofluorescence in groups with different levels of diabetic retinopathy severity (72 eyes of 46 patients) and in age-matched non-diabetic controls (34 eyes of 24 controls). We also estimated the corneal endothelium cell count and pachymetry with a contact specular microscope. For the controls, mean corneal autofluorescence was 8.8 ng equivalents fluorescein/ml (SD 0.3). Results showed increased autofluorescence of the cornea in diabetic patients (mean 17.9 ng equivalents fluorescein/ml, SD 4.2), related to the duration of diabetes (P < 0.05) and to the severity of diabetic retinopathy (P < 0.0001). Corneal endothelial cell count results showed no statistically significant relation to corneal autofluorescence (P < 0.6), indicating that the increased autofluorescence cannot be attributed to a change in corneal cell density.     

Specular microscopy of the corneal endothelium.

The endothelium of the normal corneas of 67 human subjects was studied in vivo with the specular microscope in order to quantify the method as a means of sampling the cell density of the tissue. It was found that (1) axial cell counts of the endothelium are reproducible in the same cornea after an interval of time; (2) the cell counts of the centre and periphery of the same cornea are similar; (3) the axial cell counts of pairs of eyes are similar; and (4) there is a gradual reduction of cell number with increasing age. The significance of these data is discussed.     

Quantitative control of the function of the corneal endothelium by fluorophotometry in the anterior eye segment

Whereas specular microscopy yields mostly qualitative information, fluorophotometry furnishes quantitative data of endothelial cell function. Determination of fluorescein permeability of the endothelial cell layer reflects the function of the endothelial barrier. Following topical application of fluorescein, the time-dependent change in the fluorescein concentration in corneal stroma and aqueous yields the transfer coefficient (Kc) of the corneal endothelium. With the Fluorotron Master, Kc was 3.77 +/- 0.57 X 10(-3)/min. for normal eyes; patients with cornea guttata or Fuchs's dystrophy had a significantly higher transfer coefficient (Kc = 7.9 +/- 2.88 X 10(-3)/min.). Normal Kc values were found 6-63 months (average 33.5 months) after phacoemulsification with implantation of a posterior chamber lens.