Bullous keratopathy (Fuchs' endothelial dystrophy) treated systemically with 4-trans-amino-cyclohexano-carboxylic acid

Aqueous Concentration of Tranexamic Acid after 5% and 10% Eyedrop Administration

Purpose

To determine whether topical tranexamic acid can provide acceptable therapeutic concentration in the aqueous humor.

Methods

A total of 47 patients with cataract as the sole eye disease who have been scheduled for cataract operation received one drop of tranexamic acid 5% solution at various time intervals prior to operation (from 15 minutes to 9 hours). Two patients received 10% solution of the drug. Paracentesis of the anterior chamber was done and the aqueous humor was aspirated in the operation room. The aqueous samples were analyzed using high-performance liquid chromatography method with the limit of quantification around 0.1 μg/mL. Systemic and ocular side effects were evaluated.

Results

Aqueous concentrations of tranexamic acid was higher than 1.5 μg/mL up to 160 minutes after administration of a single drop of 5% solution of the drug and then declined to an average concentration of 1 μg/mL at 300 minutes which persisted up to 9 hours after administration. In two patients for whom a single drop of 10% tranexamic acid solution was used, aqueous concentrations of 2.72 and 2.90 μg/mL were detected 60 minutes after administration. None of the patients experienced ocular or systemic side effects.

Conclusions

Topical administration of tranexamic acid is effective in yielding therapeutic intraocular concentrations of drug without any ocular or systemic toxicity.

Phototherapeutic Keratectomy for Relief of Pain in Patients With Pseudophakic Corneal Edema

PURPOSE

To evaluate the therapeutic effects of phototherapeutic keratectomy in patients with pseudophakic corneal edema

METHODS

Phototherapeutic keratectomy was performed in 12 eyes of 12 patients with pseudophakic corneal edema who were awaiting penetrating keratoplasty. All patients underwent planned corneal ablation of 120 microm. Examinations before and after surgery included uncorrected and corrected visual acuity, slit-lamp biomicroscopy, photography, and ultrasonic pachymetry.

METHODS

A reduction in pain and a slight increase in visual acuity as well as a decrease in corneal thickness were found over an average 18-month follow-up period (range, 6 to 60 months).

CONCLUSIONS

Phototherapeutic keratectomy reduced bullae formation, improved visual acuity slightly, and could be considered a valuable alternative to penetrating keratoplasty if surgery needs to be delayed or is contraindicated.

Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach

We determined the "normal" central corneal thickness (CCT) value in human corneas based on reported literature values for within-study average CCT values, and used this as a reference to assess the reported impact of physiological variables (especially age and diurnal effects), contact lens wear, pharmaceuticals, ocular disease, and ophthalmic surgery on CCT. With the expected CCT and its variance defined, it should be possible to determine the potential impact of differences in CCT in intraocular pressure (IOP) assessments, especially by applanation tonometry, using a meta-analysis approach. Some 600 sets of CCT data were identified from the worldwide literature over the period of 1968 through mid-1999, of which 134 included IOP measures as well. The within-study average CCT values and reported variance (SD) was noted along with the number of eyes and any special characteristics, including probable ethnic origin of the study subjects. Various sets of data were subjected to statistical analyses. From 300 data sets from eyes designated as normal, the group-averaged CCT was 0.534 mm. From 230 data sets where interindividual variance was reported, the group-averaged CCT was 0.536 mm (median 0.536 mm; average SD of 0. 031 mm, average coefficient of variation = 5.8%). Overall, studies using slit-lamp-based pachometry have reported marginally lower CCT values (average 0.530 mm, average SD 0.029 mm) compared to ultrasound-based studies (average 0.544, average SD 0.034 mm), which perhaps reflects the type of individual studied (non-surgical vs. pre-surgical patients) rather than the technique itself. A slight chronological increase in reported average CCT values (approximately 0.006 mm/decade) was evident, but a substantial chronological increase was evident for ultrasound pachometry studies (approximately 0.015 mm/decade). Within the meta-analysis-generated average and variance, age had no obvious impact on CCT measures for *whites, although an age-related decline in CCT is evident for non-whites. Any diurnal effects are likely concealed within the expected variance in CCT. Contact lens wear and pharmaceuticals generally produced changes in CCT that were well within the expected variance in CCT. Of the ocular diseases, only those associated with collagen disorders (including keratoconus) or endothelial-based corneal dystrophies (e.g., Fuchs) were likely to result in decreases or increases, respectively, of CCT beyond the normal variance. Routine contact lens wear and diseases such as diabetes seem unlikely to produce changes in CCT of a magnitude that would justify pachometry as a monitoring method beyond routine slit-lamp evaluation. Increases in CCT beyond the expected variance were reported after a range of intraocular surgeries (cataract operations, penetrating keratoplasty), whereas photorefractive surgery produces a measurable decrease in CCT. A meta-analysis of possible association between CCT and IOP measures of 133 data sets, regardless of the type of eyes assessed, revealed a statistically significant correlation; a 10% difference in CCT would result in a 3. 4 +/- 0.9 mm Hg difference in IOP (P </= 0.001, r = 0.419). The observed phenomenon was much smaller for eyes designated as healthy (1.1 +/- 0.6 mm Hg for a 10% difference in CCT, P = 0.023, r = 0. 331). For eyes with chronic diseases, the change was 2.5 +/- 1.1 mm Hg for a 10% difference in CCT (P = 0.005, r = 0.450), whereas a substantial but highly variable association was seen for eyes with acute onset disease (approximately 10.0 +/- 3.1 mm Hg for a 10% difference in CCT, P = 0.004, r = 0.623). Based on the meta-analysis, normal CCT in white adults would be expected to be within +/-11.6% (+/-2 SD) of 0.535 mm, i.e., 0.473-0.597 mm (95% CI, 0.474-0.596). The impact of CCT on applanation tonometry of healthy eyes is unlikely to achieve clinical significance, but for corneas of eyes with chronic disease, pachometry should be performed if the tonometry reveals IOP readi

Fuchs' endothelial dystrophy of the cornea

Fuchs' endothelial dystrophy of the cornea is a significant cause of corneal blindness in the United States. The disease is characterized by a slow, continuous loss of morphologically and physiologically altered endothelial cells, eventually leading to corneal edema. The endothelial cells synthesize a thickened Descemet's membrane with focal excrescences of altered basement membrane material (guttae). This review details the epidemiological, clinical, and laboratory data that have accumulated on Fuchs' dystrophy. Several hypotheses regarding the pathogenesis of Fuchs' dystrophy are discussed, including the possible influences of aberrant embryogenesis, hormones, and injury on the development of the disease. The current state of medical and surgical management is summarized, along with the future prospects for treatment.

The corneal endothelium

The endothelium is a monolayer of cells on the posterior corneal surface that transports water from the stroma into the anterior chamber. This movement of water counters a natural tendency for the stroma to swell and is necessary to maintain a transparent cornea. Embryologic studies, in particular the demonstration of the derivation of the endothelium from the neural crest, have provided insight into the factors that govern the response of this tissue to disease. In some species the endothelium can regenerate after injury, but in man cellular enlargement is the main mechanism of repair after cell loss. A clinical estimate of endothelial cell density and function is provided by specular microscopy, fluorophotometry and pachymetry. In this paper we review the development, structure and function of the corneal endothelium, and then consider the pathological processes that can affect this tissue.

Characterization of the Descemet's membrane/posterior collagenous layer isolated from Fuchs' endothelial dystrophy corneas

The combined Descemet's membrane (DM) and posterior collagenous layer (PCL) of Fuchs' endothelial dystrophy corneas were isolated and characterized by biochemical and immunofluorescence methods. The amino acid composition of the Fuchs' DM-PCL was similar to age-matched normal Descemet's membranes (DM). As determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and 125I two-dimensional peptide mapping, normal DM and Fuchs' DM-PCL contained the same collagen types [type IV and endothelial cell (EC) collagen], but a slight discrepancy was seen in the electrophoretic mobility of some collagen chains. Immunofluorescence staining localized fibrinogen/fibrin to Fuchs' DM-PCL but not to normal DM. These data suggest that the appearance of 110 nm banded material in sheets and fusiform bundles characteristic of Fuchs' PCL is not due to the presence of a new (abnormal) collagen type but may represent altered assembly of collagen molecules, and that the fibrinolytic system may play a role in the degenerative process of Fuchs' endothelial dystrophy.

Endothelial physiology and intraocular lens implantation

The endothelium is the cellular monolayer which lines the posterior surface of the cornea. This layer is important in clinical ophthalmology because it is vital to maintenance of the transparency of the cornea and vision through its pump and barrier functions which limit the ingress of fluid into the cornea from the aqueous. When the function of the corneal endothelium becomes compromised, the corneal stroma swells as it hydrates. Subsequently, epithelial bullae form with painful recurring epithelial erosions, and finally corneal scarring and blindness result. The relatively vulnerable position of the corneal endothelium renders it susceptible to iatrogenic injury during intraocular procedures, especially IOL implantation: the poor regenerative (mitotic) capacity of the human corneal endothelium limits its ability to recover normal function once it is injured.

Ophthalmological examination of patients in long-term treatment with tranexamic acid

Fourteen patients with hereditary angioneurotic oedema (Quincke' oedema) treated for an average period of 6 years (ranging from 15 months to 8 years) with tranexamic acid was given an ophthalmological examination in order to reveal any possible toxic damages caused by the treatment. As large doses of tranexamic acid given to animals have been shown to result in retinal degeneration, the examination was focused on checking the retinal function. A complete ophthalmic examination revealed no toxic effects in the eyes of any of the patients. No retinal damages were found that could have been caused by the tranexamic acid. The central corneal thickness was normal.

Influence of tranexamic acid and acetylsalicylic acid on the thickness of the normal cornea

In a masked cross-over study ten normal subjects were treated with tranexamic acid and acetylsalicylic acid one g three times daily for seven days. The central corneal thickness. was found to increase in response to acetylsalicylic acid and to decrease in response to tranexamic acid. This finding provides evidence for the involvement of the fibrinolytic system in the regulation of the normal corneal thickness. The endothelial morphology, as seen with the specular microscope, was unchanged during treatment with either drug.

Serum and aqueous humour concentration of tranexamic acid after peroral administration

After a single oral dose of 25 mg/kg tranexamic acid in 37 patients with cataract as the sole eye disease, the concentration of the drug was measured in both the serum and the aqueous at various intervals following intake. The serum concentration was highest after three h (average 15.44 mg/l), but a trace of tranexamic acid (0.7 mg/l) could still be found after 19 h. In the aqueous, the concentration was likewise highest after three h (average 1.62 mg/l), but, following this, the fall in tranexamic acid concentration was very gradual and after 19 h was found to be 1.3 mg/l. In two patients who had received 25 mg/kg three times daily for three days, an aqueous concentration of 2.3 mg/l was found eight h after the final intake.

Fibrinolytic factors in aqueous humour and serum from patients with Fuchs' dystrophy and patients with cataract

The concentration of alpha 2-macroglobulin, alpha 1-antitrypsin, plasminogen, C3-complement, fibrinogen degradation products (FDP) and fibrinolytic activity, were studied in the aqueous humour and serum from nine patients with Fuchs' endothelial dystrophy, 17 patients with uncomplicated senile cataract and in the secondary aqueous from six cataract patients. Finally, the aqueous humour and serum from two patients anterior uveitis were studied. An increased concentration of alpha 2-macroglobulin, alpha 1-antitrypsin, plasminogen and C3-complement was found in both the aqueous and the serum from patients with Fuchs' dystrophy when compared with the primary aqueous and serum from patients with cataract but this was only significant for alpha 1-antitrypsin in aqueous humour. A significant increase in the amount of FDP was found in the serum of the Fuchs' patients compared with the cataract patients. Fibrinolytic activity could not be demonstrated in the serum in any of the patient groups. The concentrations of the various factors found in the secondary aqueous of the cataract patients differed only slightly from the content of the primary aqueous of the Fuchs' patients.

Early postoperative changes in graft thickness after penetrating keratoplasty. Influence of host corneal disorder on time course

In 172 patients the thickness of the corneal graft was followed with frequent measurements during the first 14 days after operation. Three different graft thickness time courses were observed. Patients with keratitis, stromal dystrophy and corrosion or mechanical lesion showed a secondary rise in graft thickness on the 6th postoperative day, while patients with keratoconus and those treated with tranexamic acid showed no rise on the 6th day. Patients with Fuchs' dystrophy differed from the other groups in not reaching the maximal thickness until the 3rd postoperative day. The possible correlation of these three time courses with changes in the fibrinolytic system is discussed.

Tranexamic acid and corneal deturgescence

Recent work has demonstrated decreased corneal thickness in patients with Fuch's dystrophy and in patients following cataract extraction who were given systemic acid. Although tranexamic acid is a known antifibrinolytic drug its mechanism in reducing corneal thickness is not known. This experiment demonstrated no increase in the rate of corneal deturgescence of swollen rabbit corneas in the specular microscope when they were perfused for three h with 1 mM or 10 mM tranexamic acid. Pre-treatment of rabbits with intravenous tranexamic acid for three days and subsequent perfusion of corneas with tranexamic acid 10 mM also did not increase the rate of corneal deturgescence when compared with controls.

The effect of urokinase on central corneal thickness and vitreous haemorrhage

Thirteen patients with vitreous opacities were treated by intravitreal injection of urokinase. The central corneal thickness was measured daily on both eyes. Determination of visual acuity and ophthalmoscopy were done before treatment and at each following attendance (longest period of follow-up was seven months). The central corneal thickness increased after urokinase injection and the maximum thickness was reached on the second day. On the 6th day a secondary rise in corneal thickness occurred. The possible relation to the fibrinolytic system is discussed. There was an effect on the vitreous opacities in 8 out of 13 eyes. Only in 3 of the 13 eyes did visual acuity increase. This relative poor result as regards visual acuity in most cases was due to membranes in the vitreous.

Management of late corneal graft problems

Immediately after an operation the corneal graft is taken care of by the surgeon, but after a certain period of time the control lies in the hands of the general ophthalmologist. Examples of the management of different kinds of postoperative complications are presented. Early correct treatment of any graft problem is of decisive importance. Careful slit-lamp examination and measurement of graft thickness is stressed and the prompt use of systemic and subconjunctival steroids is recommended for incipient graft failure. Systemic tranexamic acid may also be useful.

Central thickness in corneal disorders

In the single individual the central corneal thickness (CCT) shows only small variations. Therefore CCT has been studied in a number of corneal diseases in order to investigate if this dimension might contribute to the diagnosis or to the understanding of the pathogenesis. Normal CCT was found in hereditary dystrophies with the exception of the macular dystrophy of Groenouw (type II), which showed a significantly reduced thickness. Reduced CCT was found in chronic degenerations of leutic, tuberculous or indefinite nature. Marginal degenerations of Fuchs-Terrien type also showed reduced CCT. The possible role of abiotrophic processes in this corneal thinning is dicussed. Endothelial dysfunction is indicated by increased CCT. This occurs in bullous keratopathy and in many acute disorders. Vascularisation of the cornea does not preclude the occurrence of normal or even reduced thickness.

A double-blind study of the influence of tranexamic acid on the central corneal thickness after cataract extraction

A double-blind study of the influence of systemic tranexamic acid on the central corneal thickness after cataract extraction was performed in 17 pairs of patients. Apart from the cataract, no were present. A sequential statistics was used to show that the increase in central corneal thickness after operation was significantly less in the tranexamic acid treated group than in the placebo group. There was no significant difference in intraocular pressure between the tranexamic acid and the placebo treated group. The possible influence of tranexamic acid on the thickness controlling mechanism of the cornea is discussed, and studies concerning the fibrinolytic system, the complement system and the aqueous humour amino acid treated patients are mentioned.