Evaluation of endothelial cell function with anterior segment fluorophotometry in pseudophakic patients

Determining fluorescein permeability of the endothelial cell layer provides information on the endothelial cell barrier. Following topical application of fluorescein, the time dependent change of its concentration in the corneal stroma and in the aqueous humor yields the transfer coefficient (Kc) of the corneal endothelium. Measurements with a fluorophotometer resulted in a Kc of 0.002 minute to 0.005 minute for normal eyes. Patients with corneal barrier dysfunction (cornea guttata, Fuch's dystrophy) showed an increased Kc of 0.006 minute to 0.013 minute. Up to five years postoperatively, none of the patients investigated after phacoemulsification and posterior chamber lens implantation showed a disturbance in the endothelial cell barrier function.     

Movement of fluorescein monoglucuronide in the rabbit cornea. Diffusion in the stroma and endothelial permeability

The movement of fluorescein monoglucuronide, a fluorescent metabolite of fluorescein, was studied in the rabbit cornea in vitro and in vivo. A stromal strip was exposed to fluorescein monoglucuronide, and the diffusion rate and the distribution in the stroma were measured every hr for 24 hr. The diffusion coefficient was 0.94 +/- 0.11 (+/- S.D.) X 10(-6) cm2/sec, and the saline/stroma distribution ratio was in a range of 0.67 to 0.69. The concentration of fluorescein monoglucuronide in the anterior chamber and the cornea was measured every hr for 8 hr following intravenous administration. The endothelial permeability was 4.7 +/- 1.0 X 10(-4) cm/min, and the aqueous/cornea distribution ratio was 0.56 +/- 0.05. It appears that the corneal endothelial permeability in the living eye determined hitherto from systemic administration of fluorescein is most likely the permeability to fluorescein monoglucuronide.     

Estimation of corneal endothelial pump function in long-term contact lens wearers

PURPOSE: To study the effects of long-term contact lens wear on morphologic and physiologic properties of corneal endothelial cells. METHODS: The endothelial permeability to fluorescein and the rate of corneal deswelling from hypoxia-induced edema were measured in 20 long-term (mean, 17+/-9 years; range, 5-33 years) contact lens wearers and 20 age-matched control subjects. From these data, the relative endothelial pump rate in each subject was estimated, based on the pump-leak hypothesis of corneal hydration control. Corneal autofluorescence and the aqueous humor flow rate were determined by fluorescein fluorophotometry. Images of corneal endothelial cells were recorded by using specular microscopy, and morphologic indices (cell density, coefficient of variation of cell area, percentage of hexagonal cells, and skewness) were determined. RESULTS: No statistically significant differences were found between the contact lens and control groups in endothelial permeability, corneal deswelling, relative endothelial pump rate ([mean +/- SD] 1.07+/-0.33 relative pump units versus 1.01+/-0.25 relative pump units; contact lens versus control; P = 0.57), and endothelial cell density. Contact lens wearers had a significantly higher aqueous humor flow rate (3.57+/-1.03 microl/min versus 2.77+/-0.51 microl/min; P = 0.005), coefficient of variation of cell area (0.35+/-0.09 versus 0.28+/-0.04; P = 0.006), and corneal autofluorescence (3.1+/-0.6 ng/ml versus 2.3+/-0.3 ng/ml fluorescein equivalents; P < 0.001) than did non-contact lens wearers. CONCLUSIONS: Despite the known effects of long-term contact lens wear on corneal endothelial morphometry, no effect on endothelial function was found.     

Human corneal endothelial permeability to fluorescein and fluorescein glucuronide

The corneal endothelial permeability coefficient (Pac) for fluorescein and fluorescein glucuronide was determined in ten normal young volunteers. After oral administration of fluorescein, the apparent concentrations of both dyes in the corneal stroma and the anterior chamber were measured by differential fluorometry. The apparent dye levels calculated directly from the in vivo fluorometric measurements were converted to the true ones, based on the result of a normalization experiment performed in rabbit eyes. The value of Pac averaged 5.44 +/- 1.77 X 10(-4) cm/min for fluorescein and 3.77 +/- 1.10 X 10(-4) cm/min for fluorescein glucuronide (mean +/- SD, N = 20); the former was significantly greater than the latter (paired t-test, P less than 0.001). The aqueous-cornea distribution ratio was 0.50 +/- 0.14 for fluorescein and 0.66 +/- 0.16 for fluorescein glucuronide; the latter was significantly greater than the former (paired t-test, P less than 0.001). It was suggested that the previously reported values of Pac for fluorescein in the human eye were underestimates.     

Carboxyfluorescein. A dye for evaluating the corneal endothelial barrier function in vivo

The relationship of the cornea-aqueous distribution ratio (r ca) and concentration in vitro was established for fluorescein and carboxyfluorescein. The value of rca for fluorescein was found to fall from 3.20 +/- 0.25 (mean +/- S.D., n V 6) to 1.78 as the concentration of the free fluorescein in the bathing medium rose from 5.8 X 10(-8) to 5.9 X 10(-5) g ml-1. For carboxyfluorescein, it remained unchanged over the same concentration range, and the average for total determinations was 1.29 +/- 0.16 (n = 20). The value of rca for carboxyfluorescein determined in vivo was 1.62 +/- 0.23 (mean +/- S.D., n = 6) and the corneal endothelial permeability to carboxyfluorescein in normal rabbits was 3.31 +/- 0.66 X 10(-4) cm min-1 (n = 11), which was 35% lower than that for fluorescein. Because of its lower endothelial permeability and a value of rca which is unchanged over a wide range of concentration, carboxyfluorescein may be better suited for the in vivo evaluation of the barrier function of the corneal endothelium than fluorescein.     

Effect of long-term contact lens wear on corneal endothelial cell morphology and function

Anterior segment fluorophotometry (topical) and central endothelial cell photography were performed on 40 long-term (2-23 years) contact lens wearers (four groups of ten each: hard, soft, gas permeable, and gas permeable plus prior lens usage) and 40 non-contact lens wearers of similar ages. Morphologically, the endothelial cells of contact lens wearers showed greater variability in size and shape compared to controls. The mean endothelial cell size in contact lens wearers (307 +/- 35 micron2) was smaller than that of controls (329 +/- 38 micron2, P less than 0.01). There was an increase in the coefficient of variation of cell size of the contact lens group (0.35 +/- 0.06 versus 0.25 +/- 0.04 for controls, P less than 0.0001). The endothelial cell mosaic contained a smaller percentage of hexagonal cells in contact lens wearers (66 +/- 8) compared to controls (71 +/- 7, P less than 0.01). There was a compensatory increase in five-sided cells. Functionally, there was no difference in corneal clarity, central corneal thickness or endothelial permeability to fluorescein (3.78 +/- 0.57 X 10(-4) cm/min versus 3.85 +/- 0.55 X 10(-4) cm/min for controls) between the two groups. Aqueous humor flow was increased 7% in contact lens wearers. We found no correlation between oxygen transmissibility, estimated underlying oxygen tension, or duration of wear of the contact lenses and any morphologic or functional variable. We also found no differences between the four groups of contact lens wearers except that the gas permeable lens wearers had more hexagonal and less pentagonal cells. Long-term contact lens wear induces morphologic changes in the corneal endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Decreased endothelial permeability in transplanted corneas

We measured the endothelial permeability to fluorescein of 30 clear corneal transplants from one to six years after keratoplasty. The mean permeability of 1.51 +/- 0.82 X 10(-4) cm/min was significantly lower than that of normal corneas (P less than .00001). We detected a statistically significant negative correlation between permeability and mean endothelial cell size (P less than .03), indicating that corneas with larger endothelial cells tended to be less permeable to fluorescein. We calculated a relative endothelial pump rate for each cornea; the pump rate was also decreased and negatively correlated with mean endothelial cell size (P less than .0004).     

Effect of beta-blocker eyedrops on corneal epithelial barrier function

To investigate the long-term effect of a topically applied beta-blocker on human corneal epithelium, the corneal epithelial barrier function and the superficial cell area of the corneal epithelium were evaluated. Seventeen normal healthy volunteers (without medication), 7 cataract patients (treated with pyrenoxine eyedrops) and 7 glaucoma or ocular hypertension patients (treated with 0.5% timolol maleate) were assigned to this study. The eyedrops had been used on a daily basis for at least 3 months. In the evaluation of corneal epithelial barrier function, fluorescein uptake was measured using a slitlamp fluorophotometer after application of 3 microl of 0.5% fluorescein for 10 min. In the evaluation of the superficial cell area, the central corneal epithelium was measured by tandem scanning confocal microscopy (TSCM). The healthy control and timolol groups were compared. Corneal fluorescein uptake in the healthy control, pyrenoxine and timolol groups was 20.3 +/- 3.2, 21.5 +/- 4.0 and 76.2 +/- 30.0 ng/ml (mean +/- standard error), respectively. There was a significantly higher fluorescein uptake in the timolol group compared to the pyrenoxine group (p = 0.0088) and the healthy control group (p = 0.0055). TSCM showed no significant difference in the superficial cell areas of the corneal epithelium between the healthy control and timolol groups. beta-Blocker eyedrops decreased the corneal epithelial barrier function. Their application was not accompanied by any biomicroscopic change in the superficial cell area.     

Effects of contact lenses on corneal endothelium - a morphological and functional study

PURPOSE: To study the corneal endothelial morphological changes and endothelial barrier function in contact lens wearers. METHODS: Specular microscopy and anterior segment fluorophotometry were performed on 116 controls (group 1) and 76 daily wear soft contact lens wearers. Group 2 patients (n = 34) had been wearing contact lenses for less than 5 years and group 3 (n = 42) for more than 5 years. The relationship of corneal thickness, endothelial cell density, hexagonal cell percentage, coefficient of variation in cell area, corneal autofluorescence and corneal endothelial permeability to the contact lens wear duration was studied. RESULTS: The average corneal thickness of contact lens wearers did not differ significantly from controls (0.533 +/- 0.031, 0.538 +/- 0.044, 0.532 +/- 0.031 mm for groups 1, 2 and 3, respectively; p = 0.89). However, there was a significant tendency toward corneal thinning with a longer history of contact lens wear (r = -0.31, p = 0.002 in groups 2 and 3). The percentage of hexagonal cells decreased with both increasing hours of contact lens wear per day (r = -0.36, p < 0.001) and the duration of contact lens wear in years (r = -0.33, p < 0.001), but there was no significant change in endothelial cell density in contact lens wearers. The coefficient of variation in cell size correlated more closely with increased hours of contact lens wear per day (r = 0.35, p = 0.002) than with the duration of contact lens wear in years (r = 0.12; p = 0.31). In the functional study, corneal autofluorescence increased in contact lens wearers (5.13 +/- 0.71 ng/ml in group 1, 6.45 +/- 2.03 ng/ml in group 2 and 7.21 +/- 1.51 ng/ml in group 3, respectively, p < 0.001) and the mean endothelial permeability decreased in contact lens wearers (3.89 +/- 0.95 x10(-4)/cm in group 1, 2.71 +/- 0.73 x 10(-4)/cm in group 2 and 2.95 +/- 0.91 x 10(-4)/cm in group 3, respectively, p = 0.003). CONCLUSIONS: Daily wear soft contact lenses caused morphological changes in the corneal endothelium. With an increasing span of contact lens wear, there was a significantly increased variation in cell size, a decreased hexagonal cell percentage, an evident intercellular dark area and rosette formation. The corneal autofluorescence increased and the overall endothelial permeability decreased as a consequence of contact lens wear. Contact lens wear also caused corneal thinning, and the cornea became thinner with increasing duration of contact lens wear.     

Variations in human corneal endothelial cell morphology and permeability to fluorescein with age

Fluorophotometry with topically applied fluorescein and endothelial cell photography were performed on 80 normal subjects (age 5-79 yr). Variations in endothelial cell morphology and function, flow of aqueous humor, and intraocular pressure were recorded. The mean endothelial cell size was 332.3 +/- 46.3 micron 2. A 28% increase in endothelial cell size was measured over the eight decades (r = 0.53, P less than 0.001). The coefficient of variation of cell size also increased with age (r = 0.41, P less than 0.001). The percentage of hexagonal endothelial cells decreased by 14% (r = -0.48, P less than 0.001), while the percentage of pentagonal and heptagonal cells increased by 50% (r = 0.44, P less than 0.001) and 40% (r = 0.33, P less than 0.002), respectively, with age. The mean endothelial permeability to fluorescein was 4.03 +/- 0.63 x 10(-4) cm min-1. A 23% increase in endothelial permeability with age was observed (r = 0.44, P less than 0.001). No change in central corneal thickness or endothelial pump rate was found. Flow of aqueous humor remained stable with age, despite a 25% increase in intraocular pressure (r = 0.50, P less than 0.001). Polarization of fluorescence of fluorescein in the corneal stroma decreased with age (r = -0.46, P less than 0.001). We conclude that with age the human corneal endothelium becomes morphologically less regular and may become more permeable to fluorescein.     

A reevaluation of corneal endothelial permeability to fluorescein

The permeability of the corneal endothelium and its aqueous-cornea distribution ratio were reevaluated in the rabbit eye. Both parameters were determined in an individual eye by applying the dye first by iontophoresis and then by intravitreal injection, which allows the influence of fluorescein glucuronide on the fluorophotometric measurements to be excluded. The corneal endothelial permeability coefficient was 5.13 +/- 1.64 X 10(-4) cm min-1, and the aqueous-cornea distribution ratio was 0.25 +/- 0.06 (mean +/- S.D., n = 11) on the average, and the former was considerably greater than the previous results, while the latter was considerably smaller.     

Cold-induced corneal edema in patients with trigeminal nerve dysfunction

Two previous cases of cold-induced corneal edema have been reported in patients with corneal anesthesia secondary to a trigeminal nerve disorder. We studied six patients with complete unilateral corneal anesthesia after trigeminal ablation. Subjects' eyes were exposed to 4 C air from a fan for one hour. We measured corneal thickness, corneal surface temperature, and endothelial permeability to fluorescein. During cold exposure, two of the six study eyes exhibited reversible corneal swelling (11% and 26% over baseline value). All anesthetic corneas were consistently colder (13.8 +/- 0.7 C) than the contralateral corneas (21.0 +/- 1.7 C, P = .001). Baseline endothelial permeability and aqueous humor flow rates were similar in both the study and control groups. After cold exposure, the study eyes had a significant transient increase in permeability compared to the controls (7.5 +/- 2.4 x 10(-4) cm/min vs 2.9 +/- 1.4 x 10(-4) cm/min, P = .007). Baseline endothelial photomicrographs also showed increased pleomorphism (fewer hexagonal cells) in the anesthetic corneas. These data suggest that sensory denervation of the eye influences ocular temperature regulation and corneal endothelial cell morphologic characteristics. Some anesthetic corneas are prone to cold-induced edema, which may result from excessive cooling.     

The function of corneal endothelium after penetrating keratoplasty as measured with fluorophotometry]

The aim of the study was to calculate the corneal endothelial permeability (Pac) 12 and 18 months after penetrating keratoplasty in patients (aged 42-60 years) with very good prognosis for graft clarity (10 eyes with pseudophakic and 4 eyes with aphakic bullous keratopathy; 6 eyes with keratoconus; 2 eyes with granular dystrophy; 6 eyes with central inactive scars; 1 eye with early central Fuchs' dystrophy). The normal eyes (10 eyes) served as control group in persons aged 40-65 years. Each operated eye was submitted to fluorophotometry of the anterior segment with measurement of corneal endothelial permeability (Fluorotron Master, Coherent) 12 and 18 months after the surgery. The cornea thickness measurement and endothelial cell counting were performed by specular microscopy with pachymeter 12 and 18 months after penetrating keratoplasty in cases with very good prognosis for graft clarity. The mean values of Pac: 4.48 x 10(-4) +/- 1.24 cm/min after 12 months were significantly higher (p < 0.05) than in the control group (3.61 x 10(-4) + 0.51 cm/min). Neither significant changes in corneal thickness nor endothelial cell density were noted as a result of surgery. The calculation of Pac in a late period after penetrating keratoplasty revealed a stable partial exhaustion of the corneal endothelium function in cases with good prognosis for graft clarity.     

Permeability of the corneal endothelium to fluorescein--a follow-up of keratoplasty cases

The permeability of the corneal graft endothelium to fluorescein was determined, by the oral administration method, in 47 eyes with penetrating keratoplasty. The endothelial permeability was expressed as the transfer coefficient of the dye between the anterior chamber and the cornea. In the early postoperative period, an increase in the aqueous protein was noted and a correction was made for fluorescein binding to aqueous protein. The measurements of the graft thickness and morphometry of the endothelial cells by specular microscopy were also carried out concurrently. The transfer coefficient was high in the early postoperative period, and was reduced by time. Similarly the graft was thick in the early postoperative period but it thinned to a normal level over a period of several months. A significant correlation was found between the transfer coefficient and the corneal thickness. The mean cell size of the graft endothelium was significantly greater than that of the normal cornea. The mean cell size and the postoperative period were correlated using the present data and those reported by Sato previously. A significant positive correlation was found, indicating progressive enlargement of the graft endothelial cells over a long period of time. The mean cell size was not significantly correlated with the transfer coefficient nor with the graft thickness.     

Aqueous humor dynamics in the owl monkey with comparison to cynomolgus

The owl monkey is used in experimental ocular studies, but little data are available regarding its aqueous humor dynamics. We determined aqueous humor flow rate (AHF), anterior chamber elimination coefficient (Ke), and corneal endothelial transfer coefficient (Ka) fluorophotometrically; total outflow facility (C) by 2-level constant pressure perfusion; and the facility response to intravenous and intracameral pilocarpine in pentobarbital anesthetized owl monkeys. Baseline values (mean +/- S.E.M., n eyes) were: AHF = 1.52 +/- 0.14 microliter X min-1, n = 24; Ke = 6.54 +/- 0.65 min-1 X 10(-3), n = 24; Ka = 3.84 +/- 0.40 min-1 X 10(-3), n = 24; C = 0.35 +/- 0.03 microliter X min-1 X mm Hg-1, n = 26. Intracameral pilocarpine caused a dose-dependent facility increase, with the maximum response (a tripling of resting facility) occurring between 20 and 100 micrograms; intravenous pilocarpine, 2 mg/kg, also doubled to tripled facility. With certain qualifications, these findings are comparable to those in other primate species and confirm the usefulness of the owl monkey in carefully chosen experimental studies of aqueous dynamics.     

Acute effects of topical phenylephrine on aqueous humor dynamics and corneal endothelial permeability in man

Acute effects of topical phenylephrine, an alpha-1 adrenergic agonist, on the aqueous humor dynamics and corneal endothelial permeability were studied by means of the oral fluorescein method in 11 normal young volunteers. Twenty microliters of phenylephrine HCL (10%) was instilled in one eye and the placebo in the other eye in a double masked manner. The instillations were carried out 0.5 hour before, and 2, 4 and 6 hours after the fluorescein ingestion. Fluorophotometric measurements were carried out in the central cornea, anterior chamber and plasma ultrafiltrate, and the aqueous-cornea transfer coefficient in reference to the corneal volume (kc.ac), the transfer coefficient in the anterior chamber by diffusion (kd.pa) and by flow (kfa) were calculated in each eye. The thickness of the cornea (CT), intraocular pressure (IOP) and anterior chamber volume (Va) were also measured. No significant difference was found in the CT, kc.ac, corneal endothelial permeability (kc.ac x the thickness of the stroma), Va, IOP and kfa between the experimental and control eyes, while the kd.pa was significantly smaller in the experimental eyes (paired t-test, P less than 0.01). The iris permeability factor (kd.pa x Va) decreased significantly to 0.74 +/- 0.26 (Mean +/- SD) of the control (P less than 0.01). The aqueous flow rate (kfa x Va) averaged 0.95 +/- 0.21 of the control, and the difference from unity was not significant (P greater than 0.1).     

Measurement of blood-retinal barrier permeability: a reproducibility study in normal eyes

Fluorescein penetration into the posterior vitreous depends on plasma-free fluorescein concentration and blood-retinal barrier (BRB) permeability. The reproducibility of two methods of deriving BRB permeability was studied in 19 normal eyes of 14 subjects using vitreous fluorophotometry on two separate occasions. Plasma-free fluorescence was measured at intervals over 1 hr and posterior vitreous fluorescence was measured before (background scan), within 6 min (bolus) and at 60 min (measurement) after intravenous fluorescein (14 mg X kg-1). A computer algorithm subtracted background fluorescence from the measurement scan which was then corrected for signal spread by using a "spread" function derived from the bolus scan. BRB permeability coefficient and vitreous diffusion coefficients were derived by fitting a mathematical model to the plasma and corrected vitreous fluorescence data. A permeability index was also calculated by dividing the area under the vitreous fluorescence by the area under the plasma fluorescence curve. There were no significant differences in the results between right and left eyes. Mean +/- SD values on first and second occasions for all eyes were permeability coefficient: (1.91 +/- 0.94) and (2.08 +/- 0.95) X 10(-7) cm X s-1; diffusion coefficient: (1.33 +/- 0.68) and (1.19 +/- 0.54) X 10(-5) cm2 X s-1; and permeability index: (2.05 +/- 1.03) and (2.11 +/- 1.02) X 10(-7) cm X s-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Corneal endothelial function after phacoemulsification using the fluid-based system compared to conventional ultrasound technique

AIM: To quantitatively assess corneal endothelial changes after phacoemulsification with the fluid-based system compared to conventional ultrasound technique. METHODS: This prospective, randomized clinical study included patients with cataract who were randomly assigned either to have phacoemulsification with the fluid-based system (30 eyes of 30 patients--Group 1) or with traditional ultrasound (30 eyes of 30 patients--Group 2). Patients who were available at each follow-up visit (25 eyes in both groups) were enrolled in the statistical analysis. Endothelial function was evaluated by measuring central corneal thickness, central endothelial cell density (ECD), mean cell size, and coefficient of variation in cell size preoperatively, 10 days, 1 and 3 months, and 1 year after surgery. Statistical analyses were performed using two-way repeated measure ANOVA. RESULTS: An acute, reversible increase of central corneal thickness (CCT) was found 10 days after surgery, which was similar in both groups (P=0.35). ECD decreased, whereas mean cell size increased significantly immediately after surgery. However, the impairments were finished after 1 month. The alterations were similar in both groups (ECD: P=0.99; mean cell size: P=0.85). The coefficient of variation in cell size remained stable after surgery (P=0.08), and significant difference was not found between groups (P=0.99). The endothelial cell loss (ECL) was 6.5+/-8.4% in Group 1 and 6.5+/-11.7% in Group 2 (P=0.69). CONCLUSIONS: Corneal endothelial changes were similar using the fluid-based system compared to the traditional ultrasound technique. The fluid-based method proved to be as safe as conventional ultrasound in cataract surgery.     

Aqueous humor dynamics in glaucomato-cyclitic crisis.

The transfer coefficients of fluorescein in the anterior chamber by flow, kfa, and by diffusion, kdpa, can be calculated for an individual human eye, through an analysis of fluorescein concentrations in the anterior chamber, pupillary aqueous, and serum ultrafiltrates following intravenous injection. Using this technique, aqueous humor dynamics was studied in eight patients with glaucomato-cyclitic crisis. In seven patients, the coefficients determined during the attacks averaged 1.23 +/- 0.08 (S.E.M.) X 10(-2) min.-1 for kfa and 3.51 +/- 0.81 X 10(-3) min.-1 for kdpa in the involved eye, and 0.91 +/- 0.12 X 10(-2) min.-1 for kfa and 1.36 +/- 0.39 X 10(-3) min.-1 for kdpa in the fellow eye. The differences in the coefficients between the two eyes were statistically significant (P less than 0.05). In six patients, the coefficients were measured during the remission, giving average values of 0.81 +/- 0.08 X 10(-2) min.-1 for kfa and 1.36 +/- 0.16 X 10(-3) min.-1 for kdpa in the involved eye, and 0.78 +/- 0.07 X 10(-2) min.-1 for kfa and 1.20 +/- 0.10 X 10(-3) min.-1 for kdpa in the fellow eye. The differences in the coeficients between the two eyes were not significant. In five patients, the determinations were repeated during the attack and remission, and the differences in the coefficients between both phases were statistically significant (P less than 0.05) in the involved eye.     

Long term changes in human corneal endothelium following toxic endothelial cell destruction: a specular microscopic and fluorophotometric study.

AIMS: To investigate the long term relation between corneal thickness, endothelial morphometric variables, and endothelial permeability in patients with endothelial cell counts under 900 cells/mm2 as a result of endothelial cell destruction after cataract surgery. METHODS: Eighteen patients developed the so called toxic endothelial cell destruction (TECD) syndrome following routine cataract surgery because of the intracameral injection of a toxic detergent residue. Ten patients with a mean (SEM) initial cell loss of 72% (2%) were followed for 4 years. Data were obtained at 6 months and 4 years postoperatively and compared between TECD eyes and contralateral control eyes. RESULTS: Mean (SEM) endothelial cell density of the TECD eyes increased from 642 (41) cells/mm2 to 849 (50) cells/mm2 at 4 years postoperatively (p = 0.005). There was no difference in coefficient of variation or percentage hexagonals between 6 months and 4 years postoperatively. Mean (SD) corneal thickness of the TECD eyes and control eyes was similar, 0.51 (0.02) mm and 0.49 (0.01) mm, respectively (p = 0.65). Mean (SD) endothelial permeability was also similar for TECD eyes and control eyes (4.3 (0.9) x 10(-4) cm/min and 4.4 (0.6) x 10(-4) cm/min, respectively (p = 0.57). There was no correlation between endothelial cell density, coefficient of variation, or percentage of hexagonal cells and endothelial permeability in the TECD eyes. In three patients a permanent corneal decompensation occurred. CONCLUSIONS: Four years after TECD corneal endothelial wound healing is stable and the barrier function has been restored.