Short-term impact of corticosteroids on hyaluronan and epithelial hyperplasia in the rabbit cornea after photorefractive keratectomy.

PURPOSE: To investigate the impact of corticosteroids on subepithelial hyaluronan deposition and corneal epithelium thickness in the first 10 days after photorefractive keratectomy (PRK) and to analyze a possible contralateral effect of corticosteroids. METHODS: Thirty-two New Zealand white rabbits were assigned into two groups and had a transepithelial 5.0-mm diameter, 8.00-diopter myopic PRK performed on one eye. The corticosteroid treatment group (16 animals) received 0.1 mL of methylprednisolone 4% subconjunctivally on the operation table, followed by 0.1% dexamethasone eye drops six times a day during the postoperative period. The sodium chloride (NaCl) treatment group received topical isotonic NaCl eye drops six times a day. In each treatment group, eight animals were killed after 3 and 9 days, respectively. The harvested specimens were stained for hyaluronan and the epithelial thickness was measured. RESULTS: In contrast to the epithelial thickness, the subepithelial hyaluronan did not show a significant increase during the observation period. The corticosteroid treated group showed at both time-points significantly less subepithelial hyaluronan formation as well as a significantly thinner epithelium, when compared with the NaCl-treated group. At 9 days, the corticosteroid-treated group showed a mild epithelial hyperplasia in only one of eight eyes, whereas this was a common finding in the NaCl-treated group. We detected no hyaluronan deposits in any contralateral-untreated eye, and the epithelial thickness did not differ significantly between any of the four contralateral-untreated eye groups. CONCLUSIONS: Corticosteroid medication during the first 10 days after operation reduces the amount of subepithelial hyaluronan production and inhibits the epithelial proliferation, and epithelial hyperplasia is prevented. Neither a contralateral hyaluronan deposition nor a contralateral corticosteroid effect could be detected.

Plano and refractive keratectomy. Comparison of the wound healing response.

PURPOSE: To compare the extension of the subepithelial low dry mass layer after plano and refractive keratectomy, in order to know more about the factors that influence the corneal wound healing response. METHODS: Thirty rabbits assigned into two groups were treated on one eye each with plano and refractive keratectomy, respectively. In each group five rabbits were sacrificed after 10 days, 4 weeks and 21 weeks, respectively. The corneal buttons were excised, freeze-sectioned and freeze-dried. On the freeze-dried sections microradiography was performed. In the treated eyes the superficial stroma showed qualitatively underneath the epithelium areas with low dry mass, whose extension was measured by a modified planimetry. RESULTS: The difference between the extension of subepithelial low dry mass areas in the plano and the refractive keratectomy group was small but statistically significant at 4 weeks. Within the refractive group the extension of low dry mass was significantly higher at 4 weeks compared to 21 weeks. CONCLUSION: A flat surface ablation may cause a less pronounced healing response when compared to a steep curve refractive treatment.

Phototherapeutic keratectomy for map-dot-fingerprint corneal dystrophy.

PURPOSE: To evaluate the excimer laser as a surgical instrument to treat map-dot-fingerprint (MDF) dystrophies. METHODS: Thirty eyes (24 patients) with MDF dystrophy were treated with phototherapeutic keratectomy (PTK). The treatment goal was either to improve vision (24 eyes) or to heal recurrent corneal erosions or both (10 eyes). Besides long-standing reduction in visual acuity (17 eyes), associated symptoms were fluctuating visual acuity and clinical refraction (12 eyes) and monocular diplopia (eight eyes). In 14 eyes, two or three symptoms were present, whereas 16 eyes only had one symptom. The mean age was 54 years (range, 36-79 years), and there were 14 male and 10 female subjects. Mean follow-up was 30 months (range, 12-70 months). RESULTS: In 14 of 17 eyes with long-standing reduction in visual acuity, best spectacle-corrected Snellen visual acuity (BSCVA) improved by two lines or more. All eyes with fluctuating visual acuity/clinical refraction stabilized 1-3 months after PTK. Monocular diplopia or "ghost images" disappeared in all eyes after treatment. In one of 10 eyes with recurrent corneal erosions, there was one recurrence during the follow-up period. All eyes healed shortly after treatment. No recurrence of corneal dystrophic changes was seen in the ablation zone at the final follow-up (mean, 30 months). Dystrophic changes could, however, still be seen outside the treatment zone in 50% of the eyes, but were asymptomatic in all eyes. The mean refractive change was 0.34 +/- 1.05 (mean +/- SD) diopters. CONCLUSION: In this study, excimer laser photoablation was shown to be an effective, safe, and stable choice of treatment for map-dot-fingerprint dystrophy. A refractive change, as hyperopic shift, can be an adverse side effect in some individual cases.

Treatment of corneal dystrophies with phototherapeutic keratectomy.

PURPOSE: To evaluate the excimer laser as a surgical instrument for treatment of corneal dystrophies. METHODS: Excimer laser photoablation was performed with the Summit UV 200 and VISX 20/20 excimer lasers on 30 eyes of 21 patients with different types of corneal dystrophies; phototherapeutic keratectomy (PTK) on 28 eyes (20 patients) and photorefractive keratectomy (PRK) on two eyes (one patient). The treatment goals were to improve visual acuity (26 eyes of 18 patients), heal recurrent corneal erosions (eight eyes of five patients), and treat fluctuating refraction and visual acuity (three eyes of two patients). Mean follow-up was 37 months (range 24 to 54 mo). The dystrophy groups included: map-dot-fingerprint (nine eyes of seven patients), lattice type I (five eyes of four patients), lattice type II (two eyes of one patient), granular (five eyes of three patients), central crystalline (four eyes of three patients), Reis-Bücklers' (two eyes of one patient), Meesmann's (two eyes of one patient), and Fuchs' endothelial (one eye). RESULTS: In 22 of 26 eyes (84.6%) there was an improvement in spectacle-corrected visual acuity after 6 to 12 months. This improvement remained stable in 18 eyes (69.2%). Pronounced recurrences of dystrophic changes with reduction in visual acuity were seen in three eyes of two patients: lattice type II (two eyes) and granular (one eye). In one eye with Fuchs' endothelial dystrophy, there was a recurrence of subepithelial fibrosis which had been previously removed. In eight of eight eyes (100%) treated for recurrent corneal erosions (map-dot-fingerprint, Meesmann's, and lattice type I), the erosions healed shortly after treatment and did not recur. Preoperative fluctuating refraction stabilized in three of three eyes (100%) with mapdot-fingerprint after treatment. The mean hyperopic refractive shift was +2.55 +/- 2.16 D. In none of the patients did the treatment per se lead to a decrease in spectacle-corrected visual acuity or any corneal surface problems. CONCLUSION: In corneal dystrophies with epithelial and anterior stromal opacities, excimer laser PTK may be successful in improving vision and healing recurrent corneal erosions over the long term.

Photorefractive keratectomy for low myopia at 6 mm treatment diameter. A comparison of two excimer lasers.

PURPOSE: The aim of the retrospective study was to evaluate the algorithms and the surgical performance of two excimer lasers; the VISX 20/20 and the Summit Omnimed. METHODS: Twenty patients were treated with the VISX-laser and 20 with the Summit-laser. The indications were myopia between -1 to -6 diopters which also allowed correction of astigmatism up to -2 in the VISX patients group. The treatment diameter was 6 mm and the follow-up time was 12 months. The parameters studied were visual acuity uncorrected and corrected, contrast sensitivity in light, dark and glare, endothelial cell count, corneal topography, and subjective estimation of dark vision problems. RESULTS: Both groups showed the same median refraction, -0.3 diopters. All the Summit patients had uncorrected visual acuity of 0.7 or better. In the VISX group 17 patients saw > or = 0.7 uncorrected and all patients saw 0.5 or better s.c. The remaining result parameters showed no statistical differences between the two groups. CONCLUSION: The study does not lend conclusive support for any difference between the results obtained by the two lasers.

One year follow-up of photoastigmatic keratectomy (PARK) with the VISX 20/20 excimer laser.

BACKGROUND AND OBJECTIVE: One hundred thirteen eyes were treated with photoastigmatic keratectomy using the VISX 20/20 excimer laser. The results were evaluated after 1 year. PATIENTS AND METHODS: The patients were divided into 2 groups, low astigmatism group with less than 2.00 diopters (D) of pre-operative astigmatism, the second group having 2.00 D or more. RESULTS: Astigmatism was reduced by 43.9% in the low astigmatic group and by 71.7% in the high astigmatic group. Eighty percent of the eyes in the low astigmatic group and 90% in the high astigmatic group achieved an uncorrected visual acuity of 20/40 (0.5) or better. Eighty-four percent in the low astigmatic group and 80% in the high astigmatic group were within +/- 1.00 D in spherical equivalent results. The mean spherical equivalent results were about -0.45 D in both groups using this algorithm. CONCLUSION: The results are very promising at this early stage of algorithm development.

Nuclear vacuoles in nuclear cataract.

The human lens nucleus has always been described as a homogeneous part of the lens, and if any distinct opacities are found, these are considered to be congenital. However, in lenses with nuclear cataract, both of senile type and those induced by hyperbaric oxygen, we have found relatively transparent vacuoles in the nucleus of similar appearance as cortical vacuoles. In cataracts induced by hyperbaric oxygen the vacuoles were reversible to some extent. The vacuoles have been investigated with slit-lamp photography and quantitative microradiography. Nuclear vacuoles were found in 11 out of 25 patients treated with hyperbaric oxygen compared to 19 out of 100 pre-operatively examined senile nuclear cataracts. In the microradiographs the vacuoles appeared as dark rounded areas with a lower dry mass content (approximately 0.30 g X cm-3) than the surroundings (approximately 0.50 g X cm-3).

Cataract in retinitis pigmentosa. An analysis of cataract surgery results and pathological lens changes.

The result of cataract surgery and lens pathoanatomical examination were presented in patients with retinitis pigmentosa (RP). A retrospective study of 24 cataract extractions in 15 RP patients was carried out, with special regard to visual outcome and surgical complications. The results were compared to an age matched randomly selected control group. In the retinitis pigmentosa group the post-operative visual acuity was generally good, and the surgical complications except for one case of central venous thrombosis were not more frequent than in the control group. Seven lenses from 5 patients with RP were analysed using transmission electron microscopy and quantitative microradiography. In the lenses with a progressive subcapsular edema, extensive extracellular vacuolization was found in the lens epithelium. Focal degeneration of epithelial cells was seen both in the more stationary posterior subcapsular cataracts and the progressive subcapsular cataracts. Different degrees of mitochondrial swelling was found in the epithelial cells of the stationary cataracts. The subcapsular lens fiber changes consisted of an extensive swelling of hydrated cells together with a significant reduction in their dry mass content. Migrating elongated nuclei-containing cells were found on the posterior capsule in both stationary and progressive cataracts.

The response of the lens to trauma.

The results of a number of investigations into traumatic cataract and after-cataract are presented. The traumatic cataract has been studied both in human lenses and experimentally. Light and electron microscopy, quantitative microradiography and an extracellular tracer--procion dye, were used to follow the cellular changes during cataract progression. The influence of wound size and wound healing as well as the lens fibre response to trauma were followed. Furthermore, tissue culture was used to study the proliferation of lens epithelial cells on the lens capsule. The after-cataract formed in tissue culture as well as experimental traumatic cataracts in rats and rabbits were compared to different stages of human traumatic cataract. Traumatic cataract has a subcapsular distribution and the importance of an intact functioning epithelium for lens transparency is emphasized.

Human lens epithelium in normal and cataractous lenses.

Epithelial cell appearance and cell size were studied in intact, unfixed, and unstained human lenses. Ten normal and 24 cryoextracted senile or presenile cataractous lenses, all with subcapsular cataract, were examined. The cell size of the transparent normal lenses showed little variation. However, in the cataractous lenses, a wide range was found in mean cell size of different lenses and variation in cell size within the individual lenses. No correlation was observed between cell size and degree of subcapsular cataract or combination of cataract type.

On the formation of Elschnig's pearls. A tissue culture study of regenerating rat lens epithelium.

Rats lens epithelial cells were allowed to regenerate on the lens capsule in tissue cultured. The major part of the lens fibers had been removed. After a month spherical bodies appeared, similar in appearance to Elschnig's pearls. Electron microscopical examination revealed that these spheres consisted of large extracellular vacuoles, and phase contrast examination revealed a continuous change in appearance of these spheres. The mechanism behind the tendency to form extracellular vacuoles probably include an increased extrusion of sodium and water from osmotically stressed lens cells.

Experimental traumatic cataract. I. A quantitative microradiographic study.

Traumatic cataract was induced in rat and rabbit. The progression of the posterior subcapsular cataract and the wound healing were followed by quantitative microradiography. This method makes it possible to determine the dry mass content and to calculate the refractive indices in the lens. In the injured rat lens a reduced dry mass concentration was determined in both the wound region and the posterior subcapsular region immediately after trauma. During the first week a subcapsular opacity was observed to enlarge. This opacification always corresponded to a reduction in the subcapsular concentration of dry mass. This reduced content of dry material, mainly consisting of protein, is interpreted as a hydration of the subcapsular cortex. In the rabbit lens a much larger injury had to be made in order to cause any posterior cataract. The same reduction in the content of dry material was determined in regions corresponding to opacitices but the reduction was less pronounced than in the rat lens. The border zones between different concentrations of dry mass are suggested to be the main sources of scattered light in the traumatic cataract.

Experimental traumatic cataract. II. A transmission electron microscopy and extracellular tracer study.

Lens changes caused by injury to the anterior part of the lens were studied with Procion yellow as an extracellular tracer and by transmission electron microscopy at different time intervals after trauma. Both rats and rabbits were used. The findings were related to the slit-lamp appearance of the wounded lenses. In the rat lens a posterior subcapsular cataract developed within the first hour after trauma. Within 1 hr after injury the fluorescent tracer was seen at the wound but was also conspicuous at the posterior pole. Swelling of lens fiber cells and the formation of large syncytical aggregates were found as the posterior opacity enlarged. These changes reached the anterior subcapsular cortex via the equatorial cortex after about 1 month. In the rabbit lens a slight cellular swelling was seen in the subcapsular cortex. Only in one of 15 lenses a posterior subcapsular opacity developed after about 1 week in spite of a large wound. The uptake of Procion yellow was most prominent in the wound area and was never observed at the posterior pole. In both species, no further penetration of the dye occurred through the wound after the epithelium, by regeneration, had sealed the wound. The importance of epithelial wound sealing and that of a restored cellular barrier at the posterior pole are discussed as well as the significance of these factors in the cataract progression.

Human traumatic cataract. A quantitative microradiographic and electron microscopic study.

Six cases representing different stages of cataract formation secondary to eye trauma were subjected to quantitative microradiographic or electron microscopic examination. Anterior and posterior subcapsular cataracts were found to contain extensively swollen lens fibers in the subcapsular cortex. Microradiographic measurements revealed a reduced concentration of dry mass in the subcapsular cortex around the whole circumference of the lens. The inner cortex and the nucleus appeared normal both microradiographically and electron-microscopically. Two of the examined cases had an opaque-cataract membrane and one had a Soemmerring's ring. The opaque membranes consisted of irregular masse of degenerated lens fiber material as well as regenerated lens epithelial cells. A wide range of dry mass concentration was found in the opaque membrane that was studied microradiographically. Alterations in morphology and dry mass concentration are more than sufficient to explain the development of opacification in traumatic cataract.

Formation of after-cataract by regeneration of human and rabbit lens epithelium in tissue culture.

Regeneration of lens epithelium on the lens capsule was studied in tissue culture. The entire capsule with attached epithelium was taken from rabbit lenses and from human lenses with cataract. Generally, the epithelium grew in a monolayer but multilayered masses of cells were also seen. Most lens fibers degenerated during the first days and formed spherical membrane enclosed vesicles containing cytoplasm but no nuclei. The lens fiber remnants, together with regenerating epithelium, created structures that were similar in many ways to the clinical appearance of after-cataract.