Biomedical subjects

Jay C Erie

Publications and source records attributed to Jay C Erie.

At least 19 recordsLinked to original sources

PubMed2006

Risk of retinal detachment after cataract extraction, 1980-2004: a population-based study.

PURPOSE: To estimate the long-term cumulative risk of retinal detachment (RD) after cataract extraction (CE). DESIGN: Retrospective cohort study and nested case-control study. PARTICIPANTS: All residents of Olmsted County, Minnesota who had CE from 1980 through 2004 (10 256 CEs in 7137 residents) and were diagnosed subsequently with RD in the same period. Two controls chosen from the primary cataract surgery cohort were matched to each RD case by age, gender, and duration of follow-up. METHODS: Cases were identified through the Rochester Epidemiology Project databases. Records were reviewed to confirm case status and ascertain risk factor information. The observed probability of RD after CE was estimated using the Kaplan-Meier method. A cumulative probability ratio of RD after CE was determined by comparing the observed probability of RD and the expected probability of RD in residents without CE. Logistic regression models assessed differences between cases and controls. MAIN OUTCOME MEASURES: Probability of and risk factors associated with RD after CE. RESULTS: Eighty-two cases of RD were identified. The cumulative probability of RD increased in a nearly linear manner over the 25-year study period. At 1, 5, 10, 15, and 20 years after extracapsular CE (ECCE) and phacoemulsification, cumulative probabilities of RD were 0.27%, 0.71%, 1.23%, 1.58%, and 1.79%, respectively. There was no significant difference in the probability of RD after ECCE when compared with phacoemulsification (P = 0.13). The cumulative probability ratio of RD at 20 years after ECCE and phacoemulsification remained 4.0-fold (95% confidence interval, 2.6-5.4) higher than would be expected in a similar group of residents not undergoing CE (P<0.001). Male gender, younger age, myopia, increased axial length, and posterior capsular tear were associated significantly with RD (P<0.01). CONCLUSIONS: The cumulative risk of RD after ECCE and phacoemulsification is increased for up to 20 years after surgery.

Adolescent↗

PubMed2006

Corneal keratocyte deficits after photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To measure changes in keratocyte density up to five years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized clinical trial. METHODS: Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 diopters, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 diopters. Corneas were examined by using confocal microscopy before and six months, one year, two years, three years, and five years after the procedures. Keratocyte densities were determined in five stromal layers in PRK patients and in six stromal layers in LASIK patients. Differences between preoperative and postoperative cell densities were compared by using paired t tests with Bonferroni correction for five comparisons. RESULTS: After PRK, keratocyte density in the anterior stroma decreased by 40%, 42%, 45%, and 47% at six months, two years, three years, and five years, respectively (P < .001). At five years, keratocyte density decreased by 20% to 24% in the posterior stroma (P < .05). After LASIK, keratocyte density in the stromal flap decreased by 22% at six months (P < .02) and 37% at five years (P < .001). Keratocyte density in the anterior retroablation zone decreased by 18% (P < .001) at one year and 42% (P < .001) at five years. At five years, keratocyte density decreased by 19% to 22% (P < .05) in the posterior stroma. CONCLUSIONS: Keratocyte density decreases for at least five years in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK.

Adult↗

PubMed2006

Intraocular methotrexate in ocular diseases other than primary central nervous system lymphoma.

PURPOSE: To investigate whether intravitreal methotrexate could be safely administered and improve vision in patients with ocular disease other than primary central nervous system lymphoma (PCNSL). DESIGN: A retrospective, small-case series. METHODS: Patients with various clinical conditions were treated with intravitreal methotrexate (cumulative dose < or =400 microg). Visual acuity and clinical examination were recorded to assess the safety and efficacy of the injection. RESULTS: Of 16 study eyes, final visual acuity was improved in seven, remained stable in five, and decreased in four. There was no observed toxicity attributable to methotrexate in any case. CONCLUSION: Preservation of visual acuity in 12 of 16 study eyes suggests that a 400-microg intravitreal injection is safe in ocular disease other than PCNSL. The loss of acuity in four eyes with advanced preexisting pathology may be just as likely attributable to the natural history of the disease as to intraocular methotrexate.

Adult↗

PubMed2006

Phacoemulsification in patients with Baerveldt tube shunts.

PURPOSE: To investigate the effects of phacoemulsification in glaucomatous eyes with functioning Baerveldt tube shunts. SETTING: Department of Ophthalmology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA. METHODS: This retrospective analysis followed 9 eyes of 8 patients with functioning Baerveldt tube shunts who had clear corneal phacoemulsification. Intraocular pressure (IOP), number of glaucoma medications, corneal thickness, visual acuity, and additional glaucoma surgery were measured. RESULTS: The mean follow-up was 21 months +/- 3 (SD) (range 17 to 25 months). The mean change in IOP and the number of glaucoma medications used did not significantly change at 1 month (P>.19), 1 year (P>.17), or the last follow-up (P>.17). At the last examination, 2 eyes had IOP increases of 2 to 4 mm Hg, 3 eyes had no change, and 4 eyes had decreases of 4 to 7 mm Hg. Intraocular pressure increased in 1 eye at 8 months and required a tube shunt revision. No eye developed corneal decompensation. Visual acuity improved in 8 eyes; the mean improvement was 4 +/- 3 Snellen lines. CONCLUSION: In most cases, phacoemulsification in glaucomatous eyes with a functioning Baerveldt tube shunt improved vision and maintained control of IOP.

Adult↗

PubMed2005

Heavy metal concentrations in human eyes.

PURPOSE: To measure the concentration of toxic heavy metals in the fluids and tissues of human eyes. DESIGN: Laboratory investigation. METHODS: Thirty autopsy eyes of 16 subjects were dissected to obtain the aqueous, vitreous, lens, ciliary body, retina, and retinal pigment epithelium/choroid. Concentrations of lead, cadmium, mercury, and thallium in ocular tissues, ocular fluids, and blood were determined using an inductively coupled plasma-mass spectrometer and expressed as ng/g. Heavy metal concentrations in ocular tissues were compared using a paired t test. RESULTS: Lead and cadmium were found in all of the pigmented ocular tissues studied, concentrating to the greatest extent in the retinal pigment epithelium/choroid (mean, 432 +/- 485 ng/g and 2,358 +/- 1,522 ng/g). Cadmium was found in the retina in all eyes (mean, 1,072 +/- 489 ng/g) whereas lead was found in the retina in 9 (30%) of 30 eyes (mean, 53 +/- 54 ng/g). Trace concentrations of lead and cadmium were detected in the vitreous (mean, 0.5 +/- 1.0 ng/dl and 19 +/- 29 ng/dl), lens (mean, 13 +/- 18 ng/g and 20 +/- 18 ng/g), and blood (mean, 0.5 +/- 1.2 mug/dl and 3.1 +/- 4.1 mug/l) but were not detected in the aqueous. Mercury and thallium were not detected in any ocular tissues or fluids or in the blood. CONCLUSIONS: Lead and cadmium accumulate in human ocular tissues, particularly in the retinal pigment epithelium and choroid. The potential ocular toxicity of these heavy metals and their possible role in eye disease requires further study.

Aged↗

PubMed2005

Recovery of corneal subbasal nerve density after PRK and LASIK.

PURPOSE: To measure and compare the return of corneal innervation up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized clinical trial. METHODS: Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 diopters, and 16 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 diopters. Corneas were examined by confocal microscopy before and at 1, 2, 3, and 5 years after the procedures. Subbasal nerve fiber bundles were measured to determine density (visible length of nerve/frame area) and expressed as micrometers per square millimeters. Differences were compared by Friedman's test and adjusted for multiple comparisons by the Student-Newman-Keuls procedure. RESULTS: After PRK, mean subbasal nerve density was reduced by 59% at 1 year (2764 +/- 1321 microm/mm(2) [+/-SD]) when compared with preoperative (6786 +/- 1948 microm/mm(2); P < .001). By 2 years, subbasal nerve density (6242 +/- 1763 microm/mm(2)) was not significantly different from density before PRK and remained unchanged to 5 years (5903 +/- 3086 microm/mm(2)). After LASIK, subbasal nerve density was reduced by 51%, 35%, and 34% at 1, 2, and 3 years, respectively (P < .001). By 5 years, subbasal nerves had returned to densities (4441 +/- 2819 microm/mm(2)) that were not significantly different from densities before LASIK (5589 +/- 2436 microm/mm(2)). CONCLUSION: Corneal subbasal nerve density does not recover to near preoperative densities until 5 years after LASIK, as compared with 2 years after PRK.

Adult↗

PubMed2005

The effect of age on the corneal subbasal nerve plexus.

PURPOSE: To measure subbasal nerve density and orientation in normal human corneas across a broad age range. METHODS: Sixty-five normal corneas of 65 subjects were examined by using tandem scanning confocal microscopy. Ages of subjects ranged from 15 to 79 years (mean 46 +/- 19 years), with 5 subjects from each hemidecade. Subbasal nerve fiber bundles appeared as bright, well-defined linear structures in confocal images of the central cornea. Images from 3 to 8 scans per eye (mean 4.6 +/- 1.8 scans) were randomly presented to a masked observer for analysis. The mean subbasal nerve density (total nerve length [microm] within a confocal image [area = 0.166 mm]), the mean nerve number per confocal scan, and the mean nerve orientation were determined by using a custom software program. Correlations between age and nerve density and age and nerve orientation were assessed by using Pearson correlation coefficients. RESULTS: The subbasal nerve plexus was visible in the central cornea of all subjects. The mean subbasal nerve density was 8404 +/- 2012 microm/mm (range 4735 to 14,018 microm/mm). The mean subbasal nerve number was 4.6 +/- 1.6 nerves (range 1 to 8 nerves). The mean subbasal nerve orientation was 94 +/- 16 degrees (range 58 to 146 degrees). There was no correlation between age and subbasal nerve density (r = 0.21, P = 0.09) or between age and subbasal nerve orientation (r = -0.19, P = 0.12). CONCLUSION: The density and orientation of the subbasal nerve plexus in the central human cornea does not change with age.

Adolescent↗

PubMed2005

Long-term corneal keratoctye deficits after photorefractive keratectomy and laser in situ keratomileusis.

PURPOSE: To measure changes in keratocyte density up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). METHODS: This was a prospective, nonrandomized clinical trial. Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 D, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 D. Corneas were examined by using confocal microscopy before and 6 months, 1 year, 2 years, 3 years, and 5 years after the procedures. Keratocyte densities were determined in five stromal layers in PRK patients and in six stromal layers in LASIK patients. Differences between preoperative and postoperative cell densities were compared by using Bonferroni-adjusted paired t tests. RESULTS: After PRK, keratocyte density in the anterior stroma was decreased by 39%, 42%, 45%, and 47% at 6 months, 2 years, 3 years, and 5 years, respectively (P < .001). At 5 years, keratocyte density was decreased by 20% to 24% in the posterior stroma (P < .05). After LASIK, keratocyte density in the stromal flap was decreased by 22% at 6 months (P < .02) and 37% at 5 years (P < .005). Keratocyte density in the anterior retroablation zone was decreased 18% (P < .005) at 1 year and 43% (P < .005) at 5 years. At 5 years, keratocyte density was decreased by 19% to 22% (P < .05) in the posterior stroma. CONCLUSIONS: Keratocyte density is decreased in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK for up to 5 years. Posterior stromal keratocyte deficits are first noted at 5 years.

Adult↗

PubMed2004

Corneal thickness measurement by confocal microscopy, ultrasound, and scanning slit methods.

PURPOSE: To measure corneal thickness by using a calibrated confocal microscope and to compare this measurement to thickness determined by ultrasonic and noncontact scanning slit pachymetry. DESIGN: Comparison of corneal thickness measured by using four instruments in normal subjects. METHODS: Thickness measured by a clinical confocal microscope (Tandem Scanning) was calibrated from measurements of polymethylmethacrylate contact lenses with known thickness. Corneal thickness was measured in one eye of 24 normal subjects by using this instrument, two ultrasonic pachymeters (DHG-1000 and Sonogage), and a noncontact optical scanning slit pachymeter (Orbscan II). RESULTS: Mean corneal thickness measured by confocal microscopy was 516 +/- 30 microm (+/-SD). This was less than the mean thickness measured by both ultrasonic pachymeters, 554 +/- 28 microm by the DGH, and 555 +/- 28 microm by the Sonogage (P <.001). Thickness measured by the Orbscan II pachymeter was 540 +/- 35 microm (P <.001, compared with either confocal or ultrasound) after applying an "acoustic factor" of 0.92, a default correction of the software. CONCLUSION: Corneal thickness measured by calibrated confocal microscopy is approximately 39 microm (7.0%) less than thickness measured by two commonly used ultrasonic pachymeters and approximately 24 microm (4.4%) less than thickness measured by the corrected Orbscan II pachymeter. These differences are important for planning and measuring the effects of refractive and other surgical procedures. The precision of confocal microscopy is limited by corneal motion in an anterior-posterior direction. The difference between instruments suggests that verification of clinical ultrasonic pachymeters should be revisited.

Adult↗

PubMed2004

Angioedema related to the use of hyaluronidase in cataract surgery.

PURPOSE: To report a series of cases of angioedema related to the use of hyaluronidase in cataract surgery. DESIGN: Observational case series. METHODS: Three eyes of three patients who had periorbital angioedema after phacoemulsification at the Mayo Clinic, Rochester, Minnesota, between April 2001 and May 2002 were retrospectively skin tested for allergies using the prick technique. RESULTS: Skin testing was positive in all three patients for allergy to hyaluronidase (150 U/cc) and histamine control; and negative for prick control, 2% lidocaine, 1% cyclopentolate, 2.5% neosynephrine, 0.5% proparacaine, 0.3% ofloxacin, and thimerosal. CONCLUSIONS: The use of hyaluronidase in ophthalmic anesthesia injection may cause immediate type hypersensitivity reactions such as angioedema.

Angioedema↗

PubMed2004

Preventing recurrent opacification of the visual pathway after pediatric cataract surgery.

PURPOSE: To determine the rate of secondary opacification of the visual pathway following pediatric cataract surgery in children between the ages of 10 months and 7 years. METHODS: The medical records of children less than 7 years old who underwent lens aspiration, posterior chamber intraocular lens (IOL) implantation, primary pars plana posterior capsulectomy, and anterior vitrectomy were reviewed retrospectively. Twenty-six eyes in 19 children were included in the study. All procedures were performed by an anterior segment surgeon and a vitreoretinal surgeon. Main outcome measures were the prevalence of re-opacification of the visual pathway and of early postoperative complications. RESULTS: The visual pathway remained clear in 25 of 26 eyes (96%) after pediatric cataract surgery combined with primary pars plana posterior capsulectomy and anterior vitrectomy. The mean age at surgery was 46 +/- 23 months (+/-SD). Secondary opacification of the visual pathway occurred in one eye (4%), requiring another surgical procedure. At last follow-up (mean, 26 months; range, 6 to 79 months), the visual pathway was clear in all 26 eyes (100%). No cases of clinically significant IOL displacement or of retinal detachment were noted. CONCLUSIONS: For children undergoing pediatric cataract surgery between the ages of 10 months and 7 years, IOL implantation combined with primary pars plana posterior capsulectomy and anterior vitrectomy is effective in preventing re-opacification of the visual pathway.

Cataract↗

PubMed2004

Confocal microscopy evaluation of stromal ablation depth after myopic laser in situ keratomileusis and photorefractive keratectomy.

PURPOSE: To compare the measured ablation depth after myopic laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) with the predicted ablation depth. SETTING: Mayo Clinic, Rochester, Minnesota, USA. METHODS: Twenty-five eyes of 15 patients had PRK and 25 eyes of 15 patients had LASIK to correct refractive errors between -1.50 diopters (D) and -11.00 D. The corneas were examined by in vivo confocal microscopy before and 1 month after both procedures. Thickness measurements were obtained from digital-image analysis of confocal scans. The measured ablation depth, an estimate of the actual photoablation depth, was obtained as the surgically induced stromal thinning between the preoperative and the 1-month post-PRK or post-LASIK central stromal thickness. The predicted ablation depth was recorded from the laser's software program. RESULTS: In LASIK, the measured ablation depth (81 microm +/- 34 [SD]) was 25% greater than the predicted ablation depth (65 +/- 13 microm, P =.007) and the difference between the measured and predicted ablation depths was positively associated with the mean ablation depth (r = 0.81, P<.001). In PRK, there was no difference between the measured ablation depth (48 +/- 19 microm) and the predicted ablation depth (47 +/- 18 microm, P =.84). CONCLUSION: Significantly more tissue than predicted was removed by LASIK than by PRK excimer photoablation with the laser system used in this study.

Adult↗

PubMed2004

Long-term keratocyte deficits in the corneal stroma after LASIK.

PURPOSE: To determine changes in keratocyte density up to 3 years after LASIK. DESIGN: Prospective, nonrandomized, comparative trial. PARTICIPANTS: Seventeen eyes of 11 patients received LASIK with a planned 180-microm flap to correct refractive errors between -2.0 diopters (D) and -11.0 D (mean, -6.56+/-2.44). METHODS: Corneas were examined by using confocal microscopy before LASIK and 1, 3, 6, 12, 24, and 36 months after LASIK. Bright objects that resembled keratocyte nuclei were manually counted by a masked observer. Cell densities were determined in anterior and posterior halves of the stromal flap, anterior and posterior halves of the 100-microm-thick layer immediately behind the ablation (retroablation layer), and the posterior third of the stroma. The region of stroma that was ablated (as measured 1 month after LASIK) was omitted from preoperative analysis. Cell densities after LASIK were compared (using1-factor repeated-measures analysis of variance) with densities in the corresponding layer of the normal preoperative stroma (which served as its own control). MAIN OUTCOME MEASURE: Corneal keratocyte density. RESULTS: Before LASIK, keratocyte densities in the anterior and posterior stromal flap and the anterior retroablation layer were 34 818+/-5108 cells/mm(3) (mean +/- SD), 25 390+/-4045 cells/mm(3), and 21 328+/-2980 cells/mm(3), respectively, and densities in these layers decreased 14% to 20% at 1 month after LASIK (P<0.001). Keratocyte densities in these layers remained stable at 3 and 6 months, and then gradually decreased further (P<0.001) to 26% to 36% below pre-LASIK densities by 3 years. Keratocyte densities in the remaining stromal layers did not change after LASIK. CONCLUSION: Keratocyte densities in the stromal flap and in the anterior retroablation layer decrease during the first 6 months after LASIK and then decrease further during the next 2.5 years. Further studies on these patients and others are warranted to confirm these findings and learn their significance.

Adult↗

PubMed2003

Keratocyte density in the human cornea after photorefractive keratectomy.

OBJECTIVE: To perform a quantitative analysis of keratocyte density in human corneas after photorefractive keratectomy (PRK). METHODS: In a prospective comparative trial, 24 eyes of 14 patients received PRK to correct refractive errors of between -1.25 diopters (D) and -5.75 D. Corneas were examined by using confocal microscopy before and 1 day, 5 days, and 1, 3, 6, 12, 24, and 36 months after PRK. Keratocyte nuclei were counted in 5 stromal layers in 3 to 6 scans per eye per visit. Keratocyte density in each layer post-PRK was compared with the density in the corresponding layer of the pre-PRK full stroma (included stroma that would later be photoablated) and the pre-PRK future unablated stroma (thickness adjusted by omitting the future ablation depth) (Bonferroni-adjusted paired t test). RESULTS: Keratocyte density in the anterior 10% of the post-PRK stroma decreased by 25% (P =.002), 41% (P<.001), 40% (P<.001), 43% (P<.001), and 45% (P<.001) at 3, 6, 12, 24, and 36 months compared with the anterior 10% of the pre-PRK full stroma and was reduced by 15% at 36 months (P =.02) compared with the anterior 10% of the pre-PRK future unablated stroma. CONCLUSION: After PRK, keratocyte density in the anterior stroma is not restored to the high-density levels found in the preoperative stroma.

Adult↗

PubMed2003

Aberrant regeneration of corneal nerves after laser in situ keratomileusis.

We report a case of aberrant regeneration of corneal nerves along the corneal flap interface after myopic laser in situ keratomileusis (LASIK) using confocal microscopy in vivo. The aberrant stromal nerves persisted at the last follow-up, 2 years post LASIK. The short-term clinical outcome was excellent. The long-term clinical effects are unknown.

Adult↗

PubMed2003

Intraocular lens surfaces and their relationship to postoperative glare.

PURPOSE: To estimate the potential for surface reflections in recently introduced intraocular lenses (IOLs) and to determine optic surface designs that will reduce surface reflections. SETTING: Mayo Clinic, Rochester, Minnesota, USA. METHODS: Surface-reflected glare in the unaccommodated human crystalline lens and in 6 IOLs (Bausch & Lomb SoFlex LI61U, Pharmacia CeeOn 911A, Allergan Sensar AR40, Bausch & Lomb Hydroview H60M, Alcon AcrySof MA60BM, Alcon AcrySof SA30AL) was examined in a physiologic eye model using the ZEMAX optical design program. Internal and external surface reflections were described and compared in terms of IOL surface reflectivity (%), area of the reflected glare image (mm(2)), and relative intensity of the reflected glare image. RESULTS: Compared to surface reflections from the unaccommodated human lens with a corneal power of 43.0 diopters, all the IOLs increased the relative intensity of internal and external reflections by 3- to 36-fold except the MA60BM and the SA30AL, which increased the relative intensity of internal and external reflections by 730- to 1090-fold. CONCLUSIONS: All the IOLs studied variably increased internal and external surface reflections when compared to the human crystalline lens. Surface reflections were minimized in optic designs with an anterior radius of curvature of approximately 17.0 mm or less.

Accommodation, Ocular↗

PubMed2003

Aberrant corneal nerve regeneration after PRK.

PURPOSE: To report a case of aberrant corneal nerve regeneration after myopic photorefractive keratectomy (PRK). METHODS: One patient underwent bilateral PRK to correct a refractive error of -5.50 D in each eye. Thirteen months after the original PRK, the left eye underwent an uncomplicated PRK reoperation to correct a regression of -1.00 D. The central corneas were examined by confocal microscopy preoperatively in both eyes, at 1 and 2 years after the original PRK in the right eye, and before and 1 and 2 years after the PRK reoperation in the left eye. RESULTS: Aberrant anterior stromal nerves with a coiled course and irregular branching pattern were identified 22 micro m deep to the most anterior keratocyte layer at 1 year after the PRK reoperation in the left eye and remained unchanged 2 years after reoperation. No abnormal stromal nerves were identified in the left eye before the reoperation or at any time in the right eye. CONCLUSION: Aberrant regeneration of corneal stromal nerves may occur after myopic PRK reoperation.

Adult↗

PubMed2003

Corneal wound healing after photorefractive keratectomy: a 3-year confocal microscopy study.

PURPOSE: To perform a sequential quantitative analysis of corneal wound healing after photorefractive keratectomy (PRK) by using confocal microscopy in vivo. METHODS: In a prospective, nonrandomized, comparative trial performed in an institutional setting, 24 eyes of 14 patients received PRK to correct refractive errors between -1.25 and -5.75 D. Central corneas were examined preoperatively and at 1 day, 5 days, and 1, 3, 6, 12, 24, and 36 months after PRK by using confocal microscopy. A masked observer randomly examined 3 to 6 confocal scans per eye per visit to determine epithelial and stromal thickness, keratocyte density in 5 anterior-posterior stromal layers, corneal nerve density in the subbasal region and the stroma, and corneal light backscattering (corneal haze). RESULTS: Epithelial thickness increased 21% (P < .001) by 12 months after PRK and thereafter remained unchanged to 36 months after PRK. There was no change in stromal thickness between 1 and 36 months after PRK (P = .35). The dense keratocyte population in the preoperative anterior 10% of the stroma (32,380 +/- 5,848 cells/mm3) that was partially or completely removed during photoablation was not reconstituted at 36 months in the anterior 10% of the post-PRK stroma (17,720 +/- 4,308 cells/mm3, P < .001). Subbasal nerve fiber bundle density was decreased 60% at 12 months after PRK (P < .001) before returning to densities at 24 and 36 months after PRK that were not significantly different from preoperative values (P = 1.0). Activated keratocytes and corneal haze peaked at 3 months after PRK. CONCLUSIONS: Wounding of the cornea by PRK alters the normal structure, cellularity, and innervation of the cornea for up to 36 months.

Adult↗