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Biomedical subjects

H Hamberg-Nyström

Publications and source records attributed to H Hamberg-Nyström.

At least 19 recordsLinked to original sources
PubMed2001

Cellular proliferation and leukocyte infiltration in the rabbit cornea after photorefractive keratectomy.

PURPOSE: To map the proliferative activity of corneal cells during wound healing following photorefractive keratectomy (PRK) and to compare two markers for proliferation. METHODS: PRK, 5- mm in diameter with a -6 D setting, was performed in one eye of 28 New Zealand White Rabbits. The rabbits were sacrificed at time points between 12 hours and three months after surgery. The treated and fellow corneas were fixed in 10% formaldehyde, paraffin embedded, and immunohistochemically stained for proliferate cell nuclear antigen (PCNA) and at one time point, 1 week, also for Ki-67. RESULTS: Following initial sliding of the epithelial cells, the proliferative activity in the wound area starts in the leading edge (24 hours) and is spread towards the periphery. The proliferative activity peaks after one week and subsides during the following two weeks. Early (24 hours) proliferative activity is also seen in the limbal epithelium which peaks after three days. The keratocytes express PCNA in the peripheral stroma 48 hours after injury. They then also migrate to repopulate the stroma under the wound area. The expression period lasts 1 week and subsides the following week. Leukocytes are found in the wound as early as 12 hours after injury. The cells disappear around the time of epithelial wound closure, i.e. after 3 days. The two proliferative markers PCNA and KI 67 show a similar distribution after surgery. CONCLUSION: Epithelial proliferative activity starts earlier after injury, and is preceded by leukocyte presence in the wound. The PCNA expression starts later in the keratocytes but lasts somewhat longer (3 weeks). PCNA expression appears more efficient than Ki-67 to show proliferative activity of slow cycling cells in the cornea

Animals↗
PubMed1998

The outcome of reoperation following photorefractive keratectomy.

PURPOSE: The aim of this study was to assess the outcome of reoperation following photorefractive keratectomy related to different techniques. MATERIAL AND METHODS: 265 retreated eyes were divided into 5 groups; low to moderate myopia, high myopia, enlargement, abrasion, and non-compliance. The low to moderate group was further subdivided into 5 categories based on the surgical approach of the reoperation. Outcomes were compared at 12 months after reoperation. RESULTS: There was no statistically significant difference in the median refraction prior to initial PRK, before reoperation, and after reoperation between the 5 categories 66%, of all reoperated patients achieved an uncorrected visual acuity of 0.5 or better after 12 months. 72% had a postoperative refraction between +/- 1 diopter. The other 4 groups were not statistically analyzed due to the wide variety of patients included and non-compliance. CONCLUSION: In low to moderate myopes, approximately 97% achieve uncorrected visual acuity of 0.5 or better following PRK, including one reoperation.

Adult↗
PubMed1998

Assessment of high and low contrast visual acuity after photorefractive keratectomy for myopia.

BACKGROUND: Our aim was to assess visual acuity using standardized charts and illumination conditions after photorefractive keratectomy. METHODS: High and low contrast visual acuity were measured on Bailey-Lovie logarithm of the minimum angle of resolution (LogMAR) charts under high and low illumination conditions on 105 photorefractive keratectomy patients who had been treated with the Summit (N = 60) or the VISX (N = 45) excimer laser. RESULTS: Best corrected visual acuity was reduced in the treated eye compared with the untreated control eye under all test conditions, with the greatest differences under conditions of low contrast and low illumination. Reduction of acuity under low contrast and low illumination was related to small optic zone sizes and steep ablation edge profiles found in Summit-treated eyes. In the VISX-treated eyes, high contrast acuity was reduced in the presence of central topographical irregularities, subepithelial haze, and higher myopic corrections. CONCLUSIONS: Testing conditions such as those described here may be useful in quantifying vision degradation in suboptimal viewing conditions and among patients with vague complaints.

Adult↗
PubMed1997

Factors affecting epithelial hyperplasia after photorefractive keratectomy.

PURPOSE: To determine the effect of patient age, postoperative time, ablation zone diameter and depth, attempted correction, and corneal topography on postoperative corneal epithelial thickness after photorefractive keratectomy (PRK). SETTING: Private clinic and university hospital, Stockholm, Sweden. METHODS: This retrospective, unmasked study comprised 136 myopic patients treated unilaterally with PRK. Seventy eyes had been treated with the Summit excimer laser 27 months +/- 7 (SD) earlier using ablation zone diameters of 4.1 to 5.0 mm. Sixty-six eyes had been treated with the VISX excimer laser 6 +/- 3 months earlier using a 6.0 mm zone diameter. The untreated fellow eyes served as controls. Epithelial thickness was measured at a standardized central corneal area with a modified optical pachymeter, and corneal topography was determined using computerized videokeratoscopy. RESULTS: In the Summit group, the epithelial layer in the PRK eyes was 12.0 microns (21%) thicker than in the control eyes (P < .001; 95% confidence interval [CI] 9.35 to 14.3 microns). This thickness differential correlated significantly with increased ablation depth and attempted correction. In the VISX group, the epithelium in the treated eyes was 7.0 microns (7%) thinner (P = .0009; 95% CI -1.9 to -6.7 microns) and thickness did not correlate with ablation depth or attempted correction. There was no correlation between epithelial hyperplasia and patient age or postoperative follow-up. With the laser groups combined, epithelial hyperplasia was greater with smaller zone sizes and a greater rate of change in power at the edge of the ablation zone. CONCLUSION: The factors associated with an increase in epithelial thickness were small ablation zones, greater attempted corrections, and deeper ablations. Larger, smoother ablation profiles may result in less epithelial hyperplasia.

Adolescent↗
PubMed1996

A comparative study of epithelial hyperplasia after PRK: Summit versus VISX in the same patient.

Epithelial hyperplasia has been found to occur after photorefractive keratectomy in eyes treated with small (5 mm or less) ablation zone diameters with the Summit laser, but not with large zones (6 mm) with the VISX laser (Gauthier et al. 1995a). The aim of this study was to further investigate the effect of surgical parameters on epithelial hyperplasia by comparing eyes treated with the same zone diameter but two different lasers. We examined 11 subjects who had photorefractive keratectomy for myopia performed with 5 mm ablation zones with the Summit excimer laser in one eye and the VISX 20/20 laser in the fellow eye an average of 21 months previously. Epithelial thickness and corneal topography were measured. The mean epithelial thickness was not statistically different (p = 0.083) between the eyes treated with the Summit (66 +/- 12 microns) and VISX (60 +/- 14 microns) lasers. Postoperative corneal dioptric power showed a similar profile between the two eyes at the edge of the zone, with the VISX-treated corneas being more shallow centrally. There was a trend towards greater epithelial thickness with deeper ablations. This study supports the hypothesis that epithelial hyperplasia is dependent on ablation zone diameter and ablation depth.

Adult↗
PubMed1996

Role of epithelial hyperplasia in regression following photorefractive keratectomy.

AIM: To determine the relation between epithelial hyperplasia and regression of effect after photorefractive keratectomy (PRK). METHODS: Seventy unilaterally treated patients with PRK were examined. All eyes had been treated with the Summit excimer laser 27 (SD 7) months previously with zone diameters of 4.1 to 5.0 mm. The untreated fellow eyes served as controls. Epithelial thickness was measured centrally with a thin slit optical pachometer and manifest subjective refraction was performed. RESULTS: The epithelium was 21% thicker in the treated eye (p < 0.0001). The relation between refractive regression and epithelial hyperplasia was significant (r = 0.41; p < 0.001). CONCLUSIONS: Epithelial hyperplasia after PRK correlated with the myopic shift (including hyperopia reduction) after treatment with the Summit laser. A model is proposed suggesting that both subepithelial and epithelial layers contribute to regression in the Summit treated eyes with 18 microns of epithelial hyperplasia contributing each dioptre of regression.

Adult↗
PubMed1996

Thirty-six month follow-up of excimer laser photorefractive keratectomy for myopia.

BACKGROUND AND OBJECTIVE: The aim of the study was to evaluate the refractive outcome 36 months following excimer laser photorefractive keratectomy (PRK) performed on myopic eyes. We analyzed the refractive stability between 24 and 36 months. PATIENTS AND METHODS: PRK was performed on 457 eyes with a pre-operative refraction ranging from -1.25 to -7.50 diopters (D). Ablation zone diameters of 4.3 to 4.5 mm were used. The follow up time was 36 months. RESULTS: The mean refraction 36 months following surgery was -0.22 to 0.75 D for the whole group, which was not significantly different from the mean at 24 months (-0.27 +0.74D). If we analyze the subgroups at 36 months, we find a significantly better refractive outcome in the low myopia group (up to -2.90D) compared with those with higher myopia. At 36 months, 91% of the 456 eyes had an uncorrected visual acuity of at least 20/40, and 88% of the eyes were within 1.00 D of emmetropia. CONCLUSION: These results show stability between 24 and 36 months.

Adult↗
PubMed1996

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.

Adult↗
PubMed1994

Excimer retreatment of regression after photorefractive keratectomy.

Regression of effect is a well-established complication of excimer laser photorefractive keratectomy for the correction of myopia. In 17 eyes retreated with excimer photorefractive keratectomy, minimum follow-up time was six months. Mean (+/- SD) refraction at six months postoperatively was -0.97 +/- 2.10 diopters, significantly different (P < .01) from the pre-retreatment mean of -2.91 +/- 0.86 diopters. The 11 best eyes (six-month refraction < -1.00 diopter) had a mean refraction of +0.32 +/- 0.67 diopter. At six months after retreatment, 64.7% had an uncorrected visual acuity greater than or equal to 20/40, and 58.8% were within 1.00 diopter of emmetropia. Two eyes showed a loss of one to two Snellen lines at six months. There was no significant increase in mean haze after retreatment. While the percentage of eyes with uncorrected visual acuity greater than or equal to 20/40 and the percentage of eyes within 1.00 diopter of emmetropia were lower than in eyes which did not require retreatment, the results of this study indicate that the majority of photorefractive keratectomy regressions can be successfully retreated.

Adult↗
PubMed1994

Twenty-four-month follow-up of excimer laser photorefractive keratectomy for myopia. Refractive and visual acuity results.

PURPOSE: To evaluate the 24-month refractive outcome of excimer laser photorefractive keratectomy (PRK) performed on normal, sighted myopic eyes; and to assess the evolution of postoperative refraction, the accuracy of predicted correction, and the results in terms of uncorrected visual acuity. METHODS: Photorefractive keratectomy was performed on 495 eyes, with a preoperative refraction ranging from -1.25 to -7.50 diopters (D). Ablation zone diameters of 4.3 and 4.5 mm were used. All patients were treated with a standard topical steroid regimen postoperatively. Minimum follow-up time was 24 months. RESULTS: Mean refraction (spherical equivalent +/- standard deviation) at 24 months was -0.27 +/- 0.74 D, which was significantly (P < 0.01) different from the mean at 12 months (0.01 +/- 0.78 D). There was also a significant (P = 0.01) difference between the 12- and 18-month (-0.15 +/- 0.82 D) mean refractions. But there was no significant difference between the means at 18 and 24 months postoperatively. Subgroup analysis at 24 months showed that patients with low to moderate myopia (up to -3.90 D) had significantly better refractive outcomes than those with higher myopia. Also at 24 months, 91% of the eyes had an uncorrected visual acuity of at least 20/40, and 81.5% had an uncorrected visual acuity of at least 20/30. Correspondingly, 87.5% of the eyes were within 1.00 D of emmetropia, and 71.7% were within 0.50 D. Only 0.4% lost one line of best-corrected visual acuity, no eye lost two lines or more. CONCLUSIONS: Refraction after PRK is slow to stabilize, but appears to reach stability by 18 to 24 months after surgery. The refractive results are reasonably predictable and compare well with those achieved with radial keratotomy.

Adult↗
PubMed1994

Effect of postoperative steroids on the refractive outcome of photorefractive keratectomy for myopia with the Summit excimer laser.

To assess the role of topical steroids following excimer laser photorefractive keratectomy (PRK) for myopia, we compared the refractive outcome in 100 eyes that did not receive steroids in the immediate postoperative period (untreated eyes) with 100 eyes that were treated with topical dexamethasone for three months postoperatively. Photorefractive keratectomy was performed with the Summit laser, using 4.3 mm and 4.5 mm ablation zones. At three months after surgery, the untreated eyes had a mean refraction of -0.97 +/- 1.15 diopters (D), significantly different (P < .01) from the mean refraction (+0.46 +/- 0.74 D) of the steroid-treated eyes. By six months postoperatively, 86% of the untreated eyes had regressed to a myopia of at least 0.50 D, whereas only 23% of the steroid-treated eyes had regressed. In a second study, we compared the results in 25 patients whose first PRK eye was treated with steroids after surgery but whose second eye was not. At three months postoperatively, mean refraction in the steroid-treated eyes was +1.23 +/- 0.71 D, significantly different (P < .01) from the mean of -0.45 +/- 1.29 D in the untreated eyes. The refractive results in PRK eyes treated with the Summit unit and with relatively small ablation zone diameters showed that eyes that received dexamethasone postoperatively were less likely to regress to myopia.

Administration, Topical↗
PubMed1994

Photorefractive keratectomy for low myopia at 5 mm treatment diameter. A comparison of two excimer lasers.

The aim of the study was to evaluate the algorithm and surgical performance of two excimer lasers, the Summit Excimed 200 LA and the VISX 20/20, by assessing visual outcome parameters such as visual acuity and contrast sensitivity, and subjectively estimating dark vision performance. Furthermore, refractive results and centration of the surgically ablated area were assessed. Twenty patients were included in each group. The indications were myopia between -2 to -5 diopters allowing up to -0.75 diopters astigmatism. The treatment diameter was 5 mm. The postoperative treatment was topical dexamethasone for 3 months. The follow-up time was 12 months. The results showed a median refraction +/- 0.0 D in the Summit group and -0.5 D in the VISX group 12 months postoperatively. The uncorrected visual acuity was 0.5 (20/40) or better for 100% of the Summit treated eyes, whereas 85% of the VISX treated eyes achieved 0.5 (20/40) or better. The other visual qualities as contrast sensitivity, dark vision and centration of the ablation zone were the same in both groups. The slightly more myopic outcome of the VISX laser explains the poorer average uncorrected visual acuity in this group. We have, as a result of the refractive results, changed our algorithm in the VISX machine to achieve emmetropia. It is our experience that one should try to reach emmetropia in this young population.

Adult↗
PubMed1994

Wound healing and myopic regression following photorefractive keratectomy.

Scrapings from the treated area of 17 patients who had undergone photorefractive keratectomy were analyzed. All patients had regressed to myopia and were scraped at the time of retreatment. Three scrapings from the epithelium of patients undergoing primary photorefractive keratectomy served as control. Formalin fixed and paraffin embedded, the specimens were sectioned and stained specifically for hyaluronic acid. Hematoxylin was used for counterstaining in all specimens. Scrapings revealed either epithelial hyperplasia (11 cases) or an increased amount of extracellular material (15 cases) or both (9 cases). Five of the specimens stained positive for hyaluronic acid. Four of these cases showed the highest degree of corneal haze. The latter suggests a role for hyaluronic acid formation in excessive wound healing, causing myopic regression. All patients had received prolonged topical steroid treatment, a measure that may suppress a normal occurrence of hyaluronic acid.

Cornea↗
PubMed1993

Excimer laser photorefractive keratectomy for myopia. Clinical results in sighted eyes.

PURPOSE: To evaluate the refractive results of excimer laser photorefractive keratectomy (PRK) performed on normal, sighted myopic eyes; to assess the role of postoperative topical steroid treatment in patients with PRK; and to study the regression of effect. METHODS: An argon fluoride 193-nm excimer laser was used. Photorefractive keratectomy was performed on 420 eyes with preoperative refraction ranging from -1.25 to -7.50 diopters (D). Minimum follow-up time was 12 months, and 194 of the eyes were followed for 15 months. Postoperative treatment generally consisted of topical dexamethasone for 3 months, but in a sub-study, some eyes were treated for only 5 weeks. RESULTS: Mean refraction (spherical equivalent +/- standard deviation) at 12 months was -0.04 +/- 0.84 D and at 15 months -0.22 +/- 0.78 D. At 12 months postoperatively, 86% of the eyes were within 1.00 D of emmetropia, at 15 months 87%. At 12 months, 91% of the eyes had an uncorrected visual acuity of at least 20/40, at 15 months 87%. Eyes treated with dexamethasone for 3 months regressed significantly less than those treated for only 5 weeks (P < 0.01). Dexamethasone also was effective in reversing regression later in the postoperative course. Eyes with preoperative myopia up to 4.90 D had significantly better refractive results at 12 months than eyes with myopia ranging from 5.00 to 7.50 D (P < 0.01). CONCLUSION: These data show that excimer laser PRK can correct myopia with good predictability. Results at 12 and 15 months tend to suggest stability of postoperative refraction. Regression of effect was more common in higher myopes. Topical steroids postoperatively seem to play a crucial role for the refractive result.

Adult↗
PubMed1993

[Stability of refraction 18 months after photorefractive keratectomy with excimer laser].

One-hundred-fourty-eight normal, sighted eyes, treated for myopia with argon fluoride 193-mm excimer laser, were analyzed 18 months postoperatively with respect to stability of refraction. Mean refraction 18 months after surgery was -0.32 D (+/- SD 0.89), a figure which was not significantly different from mean refractions at 12 and 15 months postoperatively. Also at 18 months, 86% of the eyes had an uncorrected visual acuity > or = 20/40, and 82% of the eyes were within 1.00 D of intended refraction (i.e. emmetropia). These percentages, which are directly related to postoperative refraction, are similar to those noted at 12 months after surgery. Although it may be too early to conclude that the 18-month refractions represent a definitive predictor of future refraction, the numerous similarities between the 12- and 18-months data presented in this study tend to suggest stability of refraction 18 months after excimer laser photorefractive keratectomy for myopia.

Adult↗
PubMed1993

Intraocular pressure after extracapsular cataract extraction with implantation of posterior chamber lenses.

To determine factors which influence postoperative intraocular pressure (IOP) we retrospectively reviewed changes in pressure during the first postoperative week in 633 consecutive eyes undergoing extracapsular cataract extraction (ECCE) with implantation of a posterior chamber lens. The material was restricted to four surgeons and two types of lenses. IOP was measured preoperatively, one day and one week after surgery. Glaucomatous eyes (n = 113) as well as exfoliative non-glaucomatous eyes (n = 79) had a higher mean IOP (27.8 and 26.1 mmHg) the first postoperative day compared to 'simple' cataract eyes (20.1 mmHg). After one week mean IOP in glaucomatous eyes still remained elevated while exfoliative non-glaucomatous eyes had regained preoperative values. Mean IOP on the first postoperative day (18.8, 24.5, 23.1 and 13.2 mmHg respectively) was also dependent on surgeon. To some extent the IOP could be correlated to tightness of suturing as estimated by keratometry. Only one surgeon had significant difference between irrigated and non-irrigated visco-elastic substance. Postoperative pressure was not only dependent on the status of the patient's eye, but factors for the individual surgeons seemed to be as important.

Adult↗