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At least 1,369 records · Page 76Linked to original sources
PubMed2002

Effect of peripapillary chorioretinal atrophy on GDx parametersin patients with degenerative myopia.

PURPOSE: To determine the effect of peripapillary chorioretinal atrophy in degenerative myopia on the retinal nerve fibre layer (RNFL) thickness measurements performed by scanning laser polarimetry. METHODS: Polarimetric RNFL analysis was done in 41 degenerative myopic eyes of 25 patients with spherical refractive errors between -7.50 and -22.00 D (mean -12.50 D;SD 3.5). Analysis was also performed on 46 eyes of 24 age-matched healthy subjects with spherical refractive errors between -1.00 and +1.00 D (mean -0.25 D; SD 0.50) with GDx Nerve Fiber Analyzer (Version 1.0.12). All of the myopic patients had clinically evident peripapillary chorioretinal atrophy in their fundus examination. RESULTS: In myopic patients most of the GDx parameters were statistically different from the control group (P < 0.05). Although average thickness, ellipse average, number, inferior maximum and inferior average were found to be higher than the healthy subjects,the modulation parameters and the ratio-based parameters were significantly decreased in degenerative myopic patients (P < 0.05). The TSNIT (temporal, superior, nasal, inferior, temporal) graph showed irregular high spikes with loss of the regular double hump pattern, especially in quadrants with large chorioretinal atrophy and visible sclera. CONCLUSION: Peripapillary chorioretinal atrophy increased retardation values, which might be explained by the high reflectivity of the bare sclera in these areas.

Adolescent↗
PubMed2006

[Fundus changes evaluation in degenerative myopia].

PURPOSE: To evaluate the presence of fundus changes in degenerative myopia. METHODS: Forty patients with refractive error of at least -6.00 diopters were selected for ophthalmologic examination followed by posterior pole photograph and echobiometry. RESULTS: We studied 57 eyes of 37 patients with refractive error ranging from -6.25 to -28.50 diopters, with mean -14.05, and axial length ranging from 26.06 to 32.86 mm, with mean 28.01. We found a temporal crescent in 36.5% and a peripapillary one in 20% of the eyes. Choroidal vessels were seen in 35% of the eyes. Posterior pole changes were as follow: posterior staphyloma in 10.5%, Fuchs' spots in 3.5% and lacquer cracks in 1.5%. Peripheral retinal examination revealed paving stone chorioretinal atrophy in 17.5%, white without pressure in 10.5%, lattice degeneration in 5%, retinal tears in 3.5% and retinoschisis in 1.5% of the examined eyes. CONCLUSIONS: Fundus changes that lead to decreased vision are common in patients with degenerative myopia. Peripheral retinal examination is very important in these patients due to the increased risk of retinal detachment.

Adolescent↗
PubMed1997

[Sensitivity loss of short wavelength sensitive cones in myopic eyes by blue-on-yellow perimetry].

A decrease of the short wavelength sensitive cone (S-cone) sensitivity has been reported in myopic eyes in addition to glaucoma and retinal diseases such as retinal detachment and diabetic retinopathy. In order to investigate early changes of visual function in myopic eyes, blue-on-yellow perimetry (B on Y) which could detect S-cone sensitivity and white-on-white perimetry (W on W) were measured with a computed perimeter program. Young subjects with good visual acuity, normal color vision, and normal intraocular pressure were selected. They had no other ophthalmoscopic abnormalities except for tigroid fundus. Mean deviations of W on W were reduced in mild and high myopic groups. In both tests, the sensitivities decreased as the refractive errors increased in all the tested areas (p < 0.0001). The sensitivity in B on Y decreased more remarkably than in W on W with an increase of refractive error (p < 0.05). We concluded that B on Y perimetry was significantly sensitive to identify early changes of visual function in myopic eyes.

Contrast Sensitivity↗
PubMedDate not supplied

Philosophy and technique for excimer laser phototherapeutic keratectomy.

Phototherapeutic keratectomy (PTK) with the excimer laser has been shown to be effective in removing anterior corneal pathology and smoothing surface irregularities. Blocking agents are important in PTK. The techniques we present seek to balance therapeutic effect and refractive error change. Successful PTK depends on thorough preoperative assessment and attention to intraoperative detail. Clinical research has demonstrated that the excimer laser is an effective tool, not only for correcting myopic refractive errors, but also for treating various types of anterior corneal pathology. We present our PTK techniques that reflect recent refinements.

Cornea↗
PubMedDate not supplied

Intraocular lens power calculation for cataract surgery after photorefractive keratectomy for high myopia.

OBJECTIVE: To assess intraocular lens (IOL) power calculations in patients undergoing cataract surgery after excimer laser photorefractive keratectomy (PRK) for myopia. METHODS: Four eyes of two patients underwent phacoemulsification with IOL implantation after PRK for myopia. The estimated refractive error that would have been induced had the IOL predicted for emmetropia been implanted was calculated using SRK-II, SRK/T, Holladay, and Binkhorst formulas. Manual keratometry and videokeratography-simulated keratometry values measured before surgery were used. Keratometry values calculated by subtracting the refractive change induced by the excimer laser PRK from the manual keratometry or videokeratography-simulated keratometry values measured before PRK were also used. Both spectacle and corneal plane calculations were performed. RESULTS: Manual keratometry and videokeratography-simulated keratometry values underpredicted the IOL power. Corneal plane manual or videokeratography refraction-derived keratometry calculations were most accurate using the SRK/T formula, while spectacle plane calculations were most accurate using the SRK-II formula. In both methods the calculated refractive error was within 0.52 diopters (D) for the emmetropic lens power predicted. Statistical analysis was not performed. CONCLUSIONS: Refraction-derived keratometric values provided the most accuracy in calculating IOL powers. Our results suggest the SRK/T formula was the most accurate for corneal plane calculations, while the SRK-II formula was the most accurate for spectacle plane calculations.

Cornea↗
PubMedDate not supplied

Management of anxiety in the refractive surgery patient.

Refractive surgery has rapidly evolved to become a preferred alternative for the correction of refractive errors. As the quest to obtain faster visual recovery, fewer complications, and early stability continues, there is little in the literature that addresses the anxiety experienced by most refractive surgical patients. Although vision-correction surgery uses highly technical and precise procedures, the need to develop therapeutic caring and communicative techniques for these patients has not been adequately addressed. There has been insufficient research in the literature focusing on the patient's fear. Respecting the patient's fear and concerns and supporting them by developing a humanistic approach to patient care may prove to be beneficial to the patient and the refractive team.

Anxiety↗
PubMed2007

Visual performance after overnight orthokeratology.

PURPOSE: To investigate visual performance after overnight orthokeratology in terms of changes from baseline values, regression of the orthokeratology effect over time, and evaluation of the best-corrected vision after treatment. In particular, to evaluate any residual visual deficits over the duration of a day due to the abnormal corneal topography induced by orthokeratology treatment. METHOD: One eye of each of six subjects was fitted with custom designed BE orthokeratology lenses (Capricornia, Brisbane, Australia), with the fellow eye acting as a control. Unaided vision, subjective sphero-cylindrical refraction, high contrast high luminance visual acuity, low contrast high luminance visual acuity, high contrast low luminance visual acuity and letter contrast sensitivity were measured at baseline and after one night (Day 1) and eight nights (Day 8) of lens wear. Except for baseline, data were collected after overnight lens wear immediately after lens removal, and again 3, 6 and 9h after lens removal. At each time point throughout the day, the visual performance measures were evaluated with the initial refraction of the day (the 0h refraction) and also using the optimum subjective refraction at each measurement time. This method was used to evaluate the practical visual performance to be expected after orthokeratology treatment and the residual visual deficits arising from any induced corneal changes after correction of defocus. RESULTS: As expected, orthokeratology lens wear significantly changed unaided vision and refraction from baseline. However, it did not significantly affect visual acuity in different contrast conditions, or contrast sensitivity. The spherical component of refraction was the only parameter to exhibit regression over each day (p=0.021), with more stability demonstrated on Day 8 than Day 1 (p=0.012). There were no statistically significant changes of best-corrected acuity from baseline in the differing contrast and luminance conditions. CONCLUSION: Apart from the predicted improvements in unaided vision and reduction of the myopic refractive error, orthokeratology treatment was not found to significantly change any other aspects of visual acuity and contrast sensitivity. All visual performance measures exhibited stability over a 9-h period. Spherical refractive error changed significantly on Day 1 but became stable after a week of treatment. These results indicate that the corneal topography changes induced by orthokeratology do not induce changes in aberrations that are large enough to significantly diminish visual performance.

Circadian Rhythm↗
PubMed1993

Three-year changes in refraction and its components in youth-onset and early adult-onset myopia.

We compared refractive components, and their changes during a 3-year period, for 79 young adults of whom 29 were youth-onset myopes, 26 were early adult-onset myopes, and 24 were emmetropes. In the initial evaluation we found that mean corneal power was greater for both groups of myopes than for the emmetropes, whereas mean vitreous chamber depth and mean axial length were greater for the youth-onset myopes than for the other two refractive error groups. However, the differences between the two groups of myopes appear to be related to the fact that the mean amount of myopia was significantly greater for the youth-onset myopes than for the early adult-onset myopes. During the 3-year period, mean spherical equivalent refraction for subjects in all three refractive error groups changed in the direction of increasing myopia. For each of the three groups, the only refractive component changes having significant correlations with changes in refraction were vitreous chamber depth and axial length. We interpret these results as indicating that: (1) whether axial elongation occurs before, during, or after the completion of the normal growth period, the result is an eye whose cornea is significantly steeper, whose vitreous chamber depth and axial length are significantly greater, and whose lens differs little from that of an emmetropic eye of a person of the same age and (2) when myopia progresses with time, the progression is due to an increase in axial length that is not fully compensated by a decrease in lens power.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Prediction of corneal haze using an ablation depth/corneal thickness ratio after laser epithelial keratomileusis.

PURPOSE: To investigate the usefulness of ablation depth/corneal thickness (AD/CT) ratio to predict corneal haze after laser epithelial keratomileusis (LASEK) using a retrospective, comparative, interventional case series. METHODS: Fifty patients (90 eyes; mean age 40.9 years) with myopia, hyperopia, and/or astigmatism underwent bilateral or unilateral LASEK for correction of refractive error. After epithelial flaps were created using an 18% alcohol solution, bilateral or unilateral LASEK was performed using the Alcon Autonomous LADARVision 4000 excimer laser. Visual acuity (best spectacle-corrected and uncorrected) and refractive error were measured before and after LASEK. Corneas were assessed by two independent evaluators under a slit-lamp biomicroscope with broad tangential illumination. The relative haze scale was quantitated: 0 (clear), 0.5+ (trace), 1+ (mild), 2+ (moderate), 3+ (marked), and 4+ (severe). RESULTS: Mean preoperative spherical equivalent refraction was -5.46 +/- 3.74 D (range -12.375 to +5.00 D), mean ablation depth was 93.04 +/- 45.03 microm (range 21.2 to 207.2 microm), and mean AD/CT ratio was 0.18 +/- 0.09 (range 0.04 to 0.41). Of 90 eyes, 40 eyes had a higher ablation depth (AD/CT ratio > 0.18) and 50 eyes had a lower ablation depth (AD/CT ratio < 0.18); 92.5% of eyes in the higher ratio group developed clinically significant haze (1+ or greater). In the lower ratio group, 94% of eyes developed no more than 1+ corneal haze, if any. CONCLUSION: The ablation depth/corneal thickness ratio is useful for predicting corneal haze after LASEK. An AD/CT ratio of 0.18 or more suggests that patients have a high risk of developing clinically significant haze (1+ or more) after LASEK.

Adult↗
PubMed2001

Laser in situ keratomileusis to correct hyperopic shift after radial keratotomy.

PURPOSE: To assess the safety and efficacy of excimer laser in situ keratomileusis (LASIK) to correct hyperopic shift following radial keratotomy (RK). SETTING: Ophthalmic Health Center, Tel Aviv, Israel. METHODS: The study comprised 15 eyes of 12 patients who had uneventful RK and subsequently developed a hyperopic shift. Laser in situ keratomileusis was performed using the Chiron Automated Corneal Shaper and the Nidek EC-5000 excimer laser with 5.5 mm central and 7.5 mm peripheral ablation zones. The corneal flap was 160 microm in thickness and 8.5 mm in diameter. The refractive correction corresponded to the patients' refractive errors. RESULTS: The mean time after RK was 10.46 years +/- 2.21 (SD) and the mean follow-up after LASIK, 7.3 months (range 1 to 42 months). The mean spherical equivalent refraction was corrected from +3.08 +/- 1.02 diopters (D) to -0.16 +/- 0.73 D after LASIK. At the last examination, 12 eyes (80%) had a refractive error within +/-1.00 D of emmetropia and an uncorrected visual acuity of 20/40 or better. No wound dehiscence, epithelial ingrowth, or other significant complication developed in any eye. CONCLUSIONS: Early postoperative results of the correction by LASIK of a hyperopic shift after RK are encouraging, but long-term studies of a larger population group are required to evaluate the method's clinical value.

Adult↗
PubMed2000

Optical correction of form deprivation myopia inhibits refractive recovery in chick eyes with intact or sectioned optic nerves.

The finding that the eyes of young chicks recover quickly from form deprivation myopia (FDM) has been interpreted as indirect evidence for active emmetropization. More direct evidence would be the demonstration that correction of FDM with spectacle lenses, thereby removing the defocus signal, prevents recovery. We investigated this issue in eyes with intact and sectioned (ONS) optic nerves. Previous studies suggest that an intact optic nerve is necessary for accurate emmetropization. Seventy day-old male chicks were monocularly deprived using velcro-mounted diffusers, which were removed after 5-6 days and in some (n=51), but not all cases, replaced by spectacle lenses (-5, -10 or -15 D). Approximately half (n=34) of the chicks also underwent ONS on day 1. Refractive errors and axial ocular dimensions were measured when the diffusers were first removed and thereafter at 2-4 day intervals over the following 1-2 weeks. In one case, measurements were continued at less regular intervals to 33 days. Lens powers were selected to either approximately correct or under-correct the refractive errors present when the diffusers were removed. Form deprivation in normal chicks produced large myopic shifts in refraction (means for groups range from -9.20 to -16.07 D). When the deprivation treatment was terminated, the myopia quickly decreased to negligible levels unless optically corrected. Correcting lenses stabilized the myopia to a level consistent with the lens power used. Interocular differences in axial length were consistent with an axial origin to the refractive changes. Results for the ONS groups exhibited similar trends although there was increased variability in the data. The findings support the interpretation that recovery from FDM is a product of active emmetropization. That ONS increased the variability of such responses implies that an intact optic nerve is required for accurate emmetropization.

Animals↗
PubMed1985

High prevalence of myopia among young adult Yupik Eskimos.

Myopia is common in Western populations but is considered rare in nonindustrialized population groups. However, studies in undeveloped areas of the Arctic and sub-Arctic have demonstrated increased rates of myopia among young Inuit adults indigenous to the region. We examined the refractive status of Yupik Eskimos, a group that had not previously been evaluated. Our subjects were young adults born between November 1960 and December 1962 to persons living in 10 villages in southwestern Alaska. The refractive status was obtained for 92% of these persons. The prevalence of myopia (refractive error -0.50 D or greater) was 68%, a rate among the highest reported for a general population anywhere in the world. The young women were significantly more myopic than the young men (mean refractive errors -1.91 and -1.36 D respectively). Astigmatism and myopia were positively correlated (r = 0.20, p less than 0.01). The etiology of myopia in this population is under study.

Alaska↗
PubMed2002

Reasons for not performing refractive surgery.

PURPOSE: To analyze the reasons that laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) were not performed in patients who requested surgical correction of their refractive errors. SETTING: Minamiaoyama Eye Clinic, Tokyo, Japan. METHODS: This retrospective review comprised 2784 consecutive patients who visited our clinic between June 1997 and August 2000. The reasons they did not receive refractive surgery (PRK or LASIK) were analyzed. RESULTS: Among the 2784 patients who requested surgery for refractive errors, 2079 patients (74.7%) had PRK or LASIK and 705 patients (25.3%) did not. The most common reasons for not treating patients surgically were myopia greater than -12.0 diopters and/or high astigmatism (20.7%), insufficient corneal thickness (8.2%), keratoconus (6.4%), cataract (5.7%), and hyperopia and/or hyperopic astigmatism (4.1%). CONCLUSIONS: Patients who request surgery have a variety of problems. Attention must be given to these individual problems, and the indications must be considered.

Adolescent↗
PubMedDate not supplied

Wide-spread myelinated nerve fibers of the optic disc: do they influence the development of myopia?

PURPOSE: To find correlations between the extent of myelinated nerve fibers with refraction anomalies. METHOD: Searching for myelinated nerve fibers in the slide collection of the University Eye Hospital Freiburg we found 13 patients. We distinguished between eyes with wide-spread myelinated nerve fibers located on and around the optic disc which extended to the midperiphery of the retina (6 patients; Group A) and eyes with circumscribed myelinated nerve fibers, localized merely around the optic disc (7 patients, Group B). In Group A myelinated nerve fibers spared the macula area, but were localized very close to the macula. Color fundus photographs were taken by the Zeiss Fundus camera SK50 (30 degrees and 50 degrees picture size) and by the Olympus Fundus camera GRC-W (same picture size). RESULTS: The myelinated nerve fibers were found to be unilateral in all 13 patients. In all 6 patients of Group A, a strabismus was present. The affected eye had a severe amblyopia and a unilateral myopia (-5.75 to -25.0 D). The nonaffected fellow eye showed a normal visual acuity with no or only a slight refractive error. In the 7 patients of the Group B, no strabismus was present and a normal or a slightly decreased visual acuity of the affected eye was found. No distinct refractive error was present in the affected and non-affected eyes of this group. CONCLUSIONS: Myopia only occurred in eyes with wide-spread myelinated nerve fibers but not in eyes with circumscribed myelinated nerve fibers. We assume that myelinated nerve fibers, if wide-spread, cause myopia.

Adolescent↗
PubMed1989

Epikeratophakia for the treatment of hyperopia.

Nordan epikeratophakia technique (NET) is described for the treatment of hyperopia and the results in eight eyes are reported (mean = +5.09 +/- 0.85 diopters preoperatively and -2.09 +/- 1.22 diopters postoperatively). The Nordan epikeratophakia technique is a modification of Kaufman-McDonald epikeratophakia with advantages that are described. Data are analyzed according to traditional means in addition to newer indices that consider both the uncorrected visual acuity and the refractive error.

Adult↗
PubMed1999

Corneal stromal wound healing in refractive surgery: the role of myofibroblasts.

While laser and incisional refractive surgery offer the promise to correct visual refractive errors permanently and predictably, variability and complications continue to hinder wide-spread acceptance. To explain variations, recent studies have focused on the role of corneal wound healing in modulating refractive outcomes. As our understanding of the corneal response to refractive surgery broadens, it has become apparent that the response of one cell, the corneal stromal keratocyte, plays a pivotal role in defining the results of refractive surgery. Studies reviewed herein demonstrate that injury-induced activation and transformation of keratocytes to myofibroblasts control the deposition and organization of extracellular matrix in corneal wounds. Myofibroblasts establish an interconnected meshwork of cells and extracellular matrix that deposits new matrix and contracts wounds using a novel and unexpected "shoe-string-like" mechanism. Transformation of keratocytes to myofibroblasts is induced in culture by transforming growth factor beta (TGFbeta) and blocked in vivo by antibodies to TGFbeta. Overall, myofibroblast appearance in corneal wounds is associated with wound contraction and regression following incisional keratotomy and the development of "haze" or increased scattered light following laser photorefractive keratectomy (PRK). By contrast, absence of myofibroblasts is associated with continued widening of wound gape and progressive corneal flattening after incisional procedures. Based on these studies, we have arrived at the inescapable conclusion that a better understanding of the cellular and molecular biology of this one cell is required if refractive surgery is ever to achieve predictable and safe refractive results.

Animals↗
PubMed2003

[Indications for refractive procedures in adult patients with strabismus and results of the subsequent therapeutic procedures].

The authors estimated the contribution of the refraction intervention and a possible evolution in the position of eyes in 102 adult individuals considering a refraction intervention. The indications for this intervention were a disorder in eye position or amblyopia in those who were interested in this operation and were examined in the years 1996 to 2002. The basic refraction examination was always supplemented by a detailed orthoptic analysis. Based on this examination the intervention was not recommended in 14 examined subjects (14%). ARK represented the contraindication of the refraction intervention in 9 patients, since subsequent changes in the size of the deviation or operation adjustment of strabismus could result in diplopia. An excessive convergence with a high AC/A in hyperopia was also considered as an unsuitable indication, since a lasting cosmetic and functional significant convergent deviation into near distances could not be excluded. Five patients declined from the refraction intervention on the basis of this explanation. The paper is mainly dealing with an analysis of the development of position of the eyes and binocular functions in 46 adult patients, who decided to undergo a refraction intervention and further orthoptic care after a complex stroboscopic and refraction examination. The adjustment of refractive error was made by the LASIK methods (Laser in Situ Keratomileusis) on 69 eyes (80%) and CLE (Cleans Lens Extraction) on 17 eyes (20%). The orthoptic analyses before and the refraction intervention revealed that in all 29 even only partially accommodating esotropia, the deviation was diminished after the refraction intervention on the average by +11.2 degrees (in the rage of +2 degrees to +30 degrees) to 5.4 degrees (in the range of parallel position to +20 degrees) in the predominantly represented hyperopia, but also in 6 myopias. The improved position of the bulbs was not directly associated with the degree of hyperopia with the original deviation. The deviation after the refraction intervention in 23 patients (79%) with esotropia was not higher than degrees. The cosmetic position of the eyes was completely satisfactory and did not therefore represent even indication for the operation. The 9 patients (35%) with esotropia and hyperopia there were an improvement of binocular functions. It could be theoretically due to the newly developed emetropia making permanent optimal sensory information possible. In all 17 exotropias there were not any significant changes in the size of deviation and the binocular functions were not reestablished, if they were not retained before. The position of eyes was solved surgically in 12 patients, while exotropia predominated in two thirds of them. The weakening or strengthening interventions on horizontal straight muscles were selected according to character of strabismus in 11 patients. Recession of the lower oblique muscle was indicated one case only for the simultaneously present torticollis with exotropia. The residual deviation was not greater than 5 degrees immediately after the operation or during the following months. Binocular functions were not reestablished in any patients. A alternate suppression or suppression of perception on one eye were proved.

Adult↗
PubMedDate not supplied

Changes in astigmatism after surgery for congenital ptosis.

To determine the effect of ptosis surgery on the astigmatic refractive error in pediatric patients, we assessed 88 eyes postoperatively at 3, 6, and 12 months. Thirty-six eyes of unilateral cases were used as controls. There was an overall increase in average astigmatic refractive error of the study group by 0.30 diopters, while the control group decreased 0.15 D. Thirty-six percent of study eyes changed by more than 0.75 D. Results were similar for both fascia lata slings and levator resections. Those patients older than 4 years showed an increase in average cylinder (0.50 D), while those younger than 4 years decreased their average cylinder (0.20 D). Careful monitoring with postoperative refractions is required in pediatric ptosis patients.

Astigmatism↗