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PubMed1999

Determinants of optic disc characteristics in a general population: The Rotterdam Study.

OBJECTIVE: To determine whether age, gender, height, and refractive error are associated with optic disc morphology in a general elderly population. DESIGN: Population-based, cross-sectional study. PARTICIPANTS: A total of 5114 subjects 55 years of age or older participated in this study, representing 76% of a population-based sample of 6777 ophthalmologically examined white patients from a geographically well-defined suburb in Rotterdam, The Netherlands. MAIN OUTCOME MEASURES: Disc area, neural rim area, cup area, vertical and horizontal cup-to-disc ratios, and parapapillary atrophy. METHODS: Disc characteristics were measured on stereoscopic simultaneous optic disc transparencies using an image analyzer. The presence and location of parapapillary atrophy, differentiated into zones alpha and beta, were assessed from disc transparencies of both eyes in a random sample of 894 persons. Subjects with open-angle glaucoma were excluded. RESULTS: The mean disc area was 2.42 mm2 (standard deviation [SD], 0.47), mean neural rim area was 1.85 mm2 (SD, 0.39), mean cup area was 0.57 mm2 (SD, 0.34), mean vertical cup-to-disc ratio was 0.49 (SD, 0.14), and mean horizontal cup-to-disc ratio was 0.40 (SD, 0.14). Age was not a determinant of any disc characteristic. Disc and rim areas were 3.2% (P < 0.0005; 95% confidence interval [CI], 2.7%-3.7%) and 4.3% (P < 0.0005; 95% CI, 3.5%-4.6%) larger in men than in women. For each diopter increase toward myopia, the disc area increased by 0.033 mm2 (P < 0.0005; 95% CI, 0.027-0.038) and neural rim area by 0.029 mm2 (P < 0.0005; 95% CI, 0.025-0.034). The disc area increased by 0.02 mm2 (P = 0.02; 95% CI, 0.005,0.05) for each 10-cm increase in height. The prevalence of zone alpha slightly decreased by 0.4% per 10 years of age (P = 0.035; 95% CI, 0.03%-0.8%), whereas the prevalence of zone beta increased by 1.3% (P = 0.0003; 95% CI, 0.57%-1.9%) for each diopter increase toward myopia. CONCLUSIONS: In a general population, statistically normal discs may vary twofold in disc area and threefold in rim area. Age is not associated with any disc characteristic, whereas disc area and neural rim area are slightly larger in men than in women. Refractive error is weakly related to disc area and neural rim area. Height is weakly related to disc area in persons of medium height. The prevalence of zone beta is higher in myopic eyes.

Age Factors↗
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↗
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↗
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↗
PubMed1987

Meridional corneal components of myopia progression in young adults and children.

Records were selected from a data pool of myopic private practice patients to study the relation of refractive error change and keratometer power change in young adulthood. Selection was on the basis of three or more refractions and keratometer readings at and/or after 18 years of age. There were significant correlations between rate of myopia progression and rate of keratometer power change. Linear regression slopes of rate of refractive error change on rate of keratometer power change were in the neighborhood of 0.7. These findings were in contrast to the lack of correlation between myopia increase and corneal steepening in childhood myopia progression. Young adulthood myopia progression also appeared to be accompanied by a slight tendency toward a with-the-rule astigmatic shift.

Adolescent↗
PubMed1996

Changes in ocular refraction and its components among medical students--a 5-year longitudinal study.

PURPOSE: Myopic progression has been noted, especially during the period of puberty. It is interesting to investigate whether myopia will progress after the age of puberty and at what rate the changes in ocular components occur during its progression. METHODS: A 5-year longitudinal study was made of refraction and its components among 345 National Taiwan University medical students (690 eyes). The examinations included corneal curvature and cycloplegic refraction measured by auto-refractor and retinoscopy, and axial length measurement with A scan ultrasonography. The same procedures and instruments were used again after 5 years. RESULTS: The myopic prevalence increased from 92.8 to 95.8%; 21 new cases of myopia developed in the 5 years. The mean refractive error significantly increased from -4.26 +/- 2.66 D of freshmen to -4.94 +/- 2.70 D of clerks. The change in refractive error at the 5-year follow-up was 0.70 +/- 0.65 D more myopic for males and 0.54 +/- 0.64 D for females. The main change in the ocular components was in axial length, which increased from 25.54 to 26.05 mm in males and from 24.60 to 24.95 mm in females. Other optical components-including corneal curvature, anterior chamber depth, lens thickness-all remained relatively unchanged from the initial values. CONCLUSIONS: Myopia can progress after the age of puberty, but at a slower rate than during childhood. Axial elongation of the eyeball is the main component that changes in myopic progression.

Adolescent↗
PubMed2007

A review of astigmatism and its possible genesis.

Astigmatism is a refractive condition encountered commonly in clinical practice. This review presents an overview of research that has been carried out examining various aspects of this refractive error. We examine the components of astigmatism and the research into the prevalence and natural course of astigmatic refractive errors throughout life. The prevalence of astigmatism in various ethnic groups and diseases and syndromes is also discussed. We highlight the extensive investigations that have been conducted into the possible aetiology of astigmatism, however, no single model or theory of the development of astigmatism has been proven conclusively. Theories of the development of astigmatism based on genetics, extraocular muscle tension, visual feedback and eyelid pressure are considered. Observations and evidence from the literature supporting and contradicting these hypotheses are presented. Recent advances in technology such as wavefront sensors and videokeratoscopes have led to an increased understanding of ocular astigmatism and with continued improvements in technology, our knowledge of astigmatism and its genesis should continue to grow.

Age Factors↗
PubMed2006

Correction of high myopia with different phakic anterior chamber intraocular lenses: ICARE angle-supported lens and Verisyse iris-claw lens.

PURPOSE: To evaluate the efficacy, predictability and safety of implanting two models of anterior chamber IOLs for high myopia. Comparison of the refractive results between two groups of patients implanted with different IOLs. MATERIALS AND METHODS: Forty eyes were implanted with phakic IOLs. The ICARE myopia lens was implanted in 20 eyes of 12 patients with preoperative myopia that ranged from -21.875 to -10.0. The mean patients' age was 30 years. The Verisyse IOL was implanted in 20 eyes of 12 patients with spherical equivalent of the refractive error from -21.625 to -10.375D, and the mean patients' age was 32.25 years. The dioptric power of the intraocular lens was calculated by considering refraction, keratometry, and anterior chamber depth. The follow-up period was 12 months. RESULTS: Twelve months after surgery, the mean refractive error (SE) was -0.19D (100% of eyes were within +/-1.0D of the target refraction) in the ICARE group, and -0.86D (95% of eyes were within +/-1.0D of the target refraction) in the Verisyse group. The postoperative refraction remained stable during the entire follow-up period. The mean uncorrected visual acuity was 0.7 in the ICARE group, and 0.69 in the Verisyse group 1 year postoperatively. There was no loss in visual acuity 1 year after surgery in the ICARE implanted eyes, one patient in the Verisyse group lost 1 line of BCVA as compared to the preoperative state. Mean endothelial cell density loss was 6.12% and 6.79% in the ICARE and Verisyse groups, respectively. There were no statistically significant differences regarding the analyzed outcome parameters between the two study groups. CONCLUSION: The implantation of both anterior chamber phakic intraocular lenses to correct high myopia resulted in a stable and predictable refractive outcome. Efficacy and safety of surgery for both implanted lens models are very high.

Adult↗
PubMedDate not supplied

The role of excimer laser photorefractive keratectomy in treatment of residual myopia followed by radial keratotomy.

Authors report a case with photorefractive retreatment after previous radial keratotomy (RK) due to a -4.5 D refractive error. The indication of retreatment was a -2.75 D regression during the one-year follow-up time after RK. The photorefractive keratectomy (PRK) was performed with the Aesculap Meditec MEL 60 excimer laser. During the 8-month follow-up time, in the retreated eye the uncorrected visual acuity was fully recovered, no regression was experienced. The excimer laser appears to be a good method to correct refractive errors, regressed or retained from previous refractive procedures due to the possibility of precise calibrating and the moderate ablation depth compared to the total thickness of the cornea.

Adult↗
PubMed1997

Indocyanine green angiography of retrobulbar vascular structures in severe myopia.

PURPOSE: To evaluate angiographic findings of retrobulbar arteries and veins in severely myopic patients. METHODS: We examined 416 severely myopic eyes (213 patients) with refractive errors greater than -8.25 diopters using indocyanine green videoangiography. A control group of 74 eyes (37 patients) had refractive errors within plano +/- 3 diopters. Four severely myopic patients underwent computed tomographic angiography to identify the entire intraorbital course of retrobulbar veins. RESULTS: Of 416 severely myopic eyes, 231 (55.5%) exhibited retrobulbar arteries, which were tortuous and pulsatile behind the posterior pole of the globe. Retrobulbar arteries connected directly with choroidal arteries temporal to the macular area. In 17 of these 231 eyes, retrobulbar arteries were also observed nasal to the optic nerve head, continuous with the Zinn-Haller ring around the optic nerve head and directly connected with choroidal arteries. In 39 severely myopic eyes (31 patients), indocyanine green angiography disclosed retrobulbar veins, most of which coursed vertically just behind the posterior pole of the globe. These retrobulbar veins originated as an inferior vascular network of the inferior orbital vein and drained into the superior orbital vein in the upper orbit. CONCLUSION: Retrobulbar arteries observed in this study were temporal and nasal short posterior ciliary arteries. Only the lateral collateral vein, which was one of the collateral channels between the superior and inferior orbital veins, was visible in severely myopic eyes. Indocyanine green angiography is useful in evaluating retrobulbar vascular structure in severely myopic eyes.

Adolescent↗
PubMed2004

Cataract extraction following penetrating keratoplasty.

OBJECTIVE: To assess the safety of cataract extraction following penetrating keratoplasty for corneal graft survival and to evaluate visual and refractive outcomes in corneal graft patients undergoing cataract extraction. METHODS: Retrospective chart review of 29 eyes of 24 patients with corneal grafts who underwent cataract extraction from January 1, 1993 to December 31, 2002, followed on the Cornea Service at Wills Eye Hospital. RESULTS: The mean time from penetrating keratoplasty to cataract extraction was 8.4 years (range 2 months to 36 years). Following cataract extraction, the corneal grafts remained clear in all but 1 eye (3%), during an average follow-up time of 44.5 months (range 3-118 months). All of the remaining patients benefited from improved visual acuity, with 15 of 28 patients having a postoperative best-corrected visual acuity of 20/30 or better. Patients also benefited from decreased absolute spherical refractive error, with a preoperative mean value of 6.6 +/- 3.4 D compared with 2.4 +/- 1.6 D postoperatively, while cylindrical refractive error remained relatively stable at 3.2 +/- 2.9 D preoperatively and 2.8 +/- 2.4 postoperatively. The patient who developed graft failure had 3 episodes of preoperative endothelial rejection and a clear corneal graft at the time of cataract surgery. CONCLUSIONS: Cataract surgery following penetrating keratoplasty is a safe and effective procedure, with a low but definite risk of corneal graft failure. In patients with clear grafts and visually significant cataracts, cataract extraction alone is preferred over repeat penetrating keratoplasty and cataract extraction.

Aged↗
PubMed1989

Review of children referred from the school vision screening programme in Kettering during 1976-8.

The progress of 108 children who were identified by the vision screening programme in school as having defective vision (excluding those with puberty onset myopia) was reviewed. Treatment of these children resulted in improvement in visual acuity of the worst eye (two lines or better) for 16 children. Eighteen children had severe amblyopia (6/24 or worse). Among these the vision of only five was improved by treatment. Two thirds of the children had refractive errors in the better eye which required correction. It seems sensible to identify and treat children with bilateral refractive errors, but the need to treat children with lesser degrees of amblyopia is questioned.

Amblyopia↗
PubMedDate not supplied

Phacoemulsification and intraocular lens implantation combined with trabeculotomy for open-angle glaucoma and coexisting cataract.

OBJECTIVE: To study the outcome of phacoemulsification and intraocular lens implantation combined with trabeculotomy. METHODS: We performed trabeculotomy combined with phacoemulsification and foldable lens implantation in 25 eyes with open-angle glaucoma and coexisting cataract in 18 patients. The series comprised 9 males (13 eyes) and 9 females (12 eyes). Mean age of the patients was 73.4 +/- 10.9 years (45-87 years). Mean follow-up period was 14.3 +/- 6.0 months (6-24 months). RESULTS: The preoperative intraocular pressure was 21.4 +/- 3.7 mm Hg. The postoperative intraocular pressure 6 months after the surgery was 12.8 +/- 3.4 mm Hg. A postoperative tension spike (>30 mm Hg) was observed in 2 eyes. Six months after the operation, the intraocular pressure was controlled under 21 mm Hg in all eyes, and under 16 mm Hg in 18 eyes. The medication score (one point per antiglaucomatous medication) was 2.0 +/- 1.6 before the surgery and 0.4 +/- 0.7 after the surgery. The mean refractive error after the operation was -0.8 +/- 0.7 D (range -2.4 to 0 D). The deviation of the actual refractive error from the predicted one was +0.29 +/- 0.54 D (range -0.52 to +1.10 D). CONCLUSION: The outcome of the combined operation for open-angle glaucoma and coexisting cataract was promising.

Aged↗
PubMed2004

Blur adaptation in myopes.

It has been suggested that when subjects with myopia remove their refractive correction, blur adaptation develops to produce an improvement in their visual resolution. The present study measured visual acuity (VA) using high contrast letters and gratings with contrast levels between 2.5% and 40% at 30-minute intervals over the course of a 3-h period during which the subjects remained uncorrected. Twenty-two young subjects with moderate degrees of myopia (mean refractive error, -185 D) participated in the study. Immediately after a 1-h period of full correction, subjects spent 3 h without any refractive correction, during which time they watched television and videos at a viewing distance of 5 m. A significant change in letter and grating VA was observed during the course of the 3-h period of sustained blur, with the mean uncorrected letter VA improving from 0.76 (SD, +/-0.26) to 0.53 (SD, +/-0.23) logarithm of the minimum angle of resolution (logMAR). The Snellen equivalent to this change is from 6/35 to 6/20. A significant improvement in grating acuity was also observed. However, no significant change in refractive error, measured using noncycloplegic autorefraction, was found. These results demonstrate significant blur adaptation in subjects with uncorrected myopia, which does not result from a change in refractive state. We hypothesize that the improvement in visual resolution results from perceptual adaptation to the blurred image, which may occur at central sites within the visual cortex.

Adaptation, Physiological↗
PubMed1995

Refractive changes at extreme altitude after radial keratotomy.

PURPOSE: We studied the effects of altitude on four corneas that had undergone radial keratotomy and four normal corneas exposed to increasing elevation during a high-altitude excursion. METHODS: We measured visual acuity, cycloplegic refraction, keratometry, and intraocular pressure at sea level and after 24-hour exposure to 12,000 and 17,000 ft. RESULTS: We observed a significant increase in spherical equivalence (hyperopic shift) in radial keratotomy eyes exposed to altitude as compared to controls (P < .0001). The average change in spherical equivalent cycloplegic refraction from sea level to 12,000 ft was 1.03 +/- 0.16 diopters and from sea level to 17,000 ft was 1.94 +/- 0.26 diopters. We also observed a significant decrease in keratometry values at altitude as compared with control corneas (P < .0001). The average change in keratometry from sea level to 12,000 ft was 0.59 +/- 0.19 diopter and from sea level to 17,000 ft was 1.75 +/- 0.27 diopters. CONCLUSIONS: Although the specific origin of these changes is open to question, we hypothesize that hypoxic corneal expansion in the area of the radial keratotomy incisions may lead to central corneal flattening and a hyperopic shift in refractive error. The cornea that has undergone radial keratotomy appears to adjust constantly to changing environmental oxygen concentration, producing a new refractive error over a period of 24 hours or more. Additional study is required to identify with certainty the specific origin of the hyperopic shift at high altitude.

Adult↗
PubMed1979

Refractive variation and donor tissue size in aphakic keratoplasty. A prospective randomized study.

Forty-six patients were examined in a prospective, randomized clinical study to compare the use of the same size trephine on both donor and recipient with the use of a 0.5-mm larger trephine on the donor in aphakic keratoplasty and in keratoplasty combined with lens extraction. The results showed no statistically significant difference in refractive error, either in spherical equivalents or in astigmatism. The larger donor tissue may have some value in reducing high plus-refractive error and in reducing intraocular pressure after surgery.

Aphakia↗
PubMed1991

An ophthalmic survey of African patients presenting at rural eye clinics in South Africa.

The records of 10,254 people attending rural eye clinics in South Africa during 1984-85 were analyzed to determine the reasons for presentation. The main reasons for presentation were refractive error, conjunctivitis, and cataract. It is expected that population growth plus the increased vocational needs for the correction of refractive errors will result in an increased demand for optometric services in rural eye clinics. It is suggested that optometry has a major role to play in providing primary eye care services to the underserved populations of the South African homelands.

Adolescent↗
PubMed2005

Refractive surgery after corneal transplantation.

PURPOSE OF REVIEW: Many patients who have undergone corneal transplantation are unable to achieve satisfactory visual acuity with spectacle and contact lens correction alone. For these patients, refractive surgery becomes a viable option to reduce the post-keratoplasty ametropia. With the many recent advances in refractive surgery for naturally occurring refractive error, new possibilities arise for application to this complicated set of patients. This review discusses key recent developments in refractive surgery after corneal transplantation. RECENT FINDINGS: The biomechanical effects of incisional keratotomy on post-keratoplasty corneas continue to be studied, and these techniques remain a common and simple method of reducing astigmatism. Photorefractive keratectomy, previously problematic for regression and haze formation, is gaining new prominence as early experience with the adjunctive use of mitomycin C has demonstrated good results. Long-term studies with laser in-situ keratomileusis (LASIK) have continued to show good safety and efficacy. Modern developments in cataract surgery appear to have lower incidences of graft rejection and failure. Developments in lens implantation technology continue to offer expanding options for intraocular refractive surgery. SUMMARY: Although visual rehabilitation after corneal transplantation remains a formidable challenge, developments in refractive surgery for naturally occurring ametropias directly translate into an improved ability to help these most challenging refractive cases. Continued research will bring about improved efficacy while maintaining a high level of safety.

Corneal Transplantation↗