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At least 685 records · Page 38Linked to original sources
PubMed1993

Excimer laser photorefractive keratectomy in Singapore--a new treatment modality for myopia.

BACKGROUND: Myopia is a national epidemic in Singapore. Photorefractive Keratectomy (PRK) for the treatment of myopia using the Argon Fluoride Excimer Laser commenced in January 1992 at the Singapore National Eye Centre. METHODS: An open, prospective, non randomised clinical trial to assess the efficacy, predictability, stability, and safety of PRK for the correction of myopia between -2.0 to -6.0 dioptres. RESULTS: One hundred and fifty-five eyes of one hundred and thirty-five patients underwent PRK between January and September 1992, of which thirty-one had completed at least six months of follow-up. Twenty-nine of the thirty-one patients (93.5%) achieved an unaided visual acuity of at least 6/12. Twenty-six patients (83.9%) were within 1 dioptre of emmetropia. There was an initial over-correction in all patients which regressed to a plateau at around three or four months. Corneal haze did not pose a significant problem. Three patients had ocular hypertension, and another developed a mild allergic reaction to the antibiotic-steroid ointment. CONCLUSIONS: Excimer Laser Photorefractive Keratectomy is a very effective, fairly predictable, stable and safe surgical method for the treatment of myopia.

Adult↗
PubMedDate not supplied

[The characteristic interrelationships of the anterior chamber angle in myopia].

Comprehensive ophthalmologic examinations of the anterior chamber angle were carried out in 130 patients (259 eyes) aged 16 to 39 (mean age 22.9 +/- 0.55 years) with myopia of 0.5 to 13.6 diopters. Study of the pattern of gonioscopic signs distribution has shown that the most characteristic factor related to myopia development and progress is the presence of goniodysgenesis signs, namely, expressed development of ligamentum pectinatum iridis, marked anterior position of Schlemm's canal combined with a wide anterior chamber corner, and pigmentation of anterior chamber corner. Analysis of gonioscopic signs, their mutual influences and relationships with other anatomicofunctional parameters will help assess the role of these signs in the development of complicated myopia, prediction of myopia course, and differential diagnosis of its pathogenetic forms.

Adolescent↗
PubMed1993

[Myopia and cataract].

Myopia and cataracts are frequently associated: a cataract may lead to index myopia; high myopia is complicated by the frequent and early development of cataracts. In this case, given the retinal fragility, there are problems in operating techniques and indication. Extra-capsular extraction with in-the-bag implantation is the safest technique. A lens implant of well-calculated strength can best correct a preexistent myopia. The refractive goal varies according to the patient's age and activity. Intra and postoperative complications are rarer than expected with such abnormal eyes. A useful visual acuity can be obtained in 90% of the cases.

Aged↗
PubMed1993

[Surgery for moderate or mild myopia].

After a long period of hesitation and reluctance, surgery of moderate to mild myopia (1 to 6 dioptries) is currently practiced by specialists in refractive surgery. At present, two ambulatory techniques are in competition: radial keratotomy, a truly surgical procedure that is more than 10 years' old, and the much more recent photorefractive keratectomy performed with an excimer laser beam, which is still under evaluation but has a very promising future. The goal of these two techniques is to correct myopia by flattening the cornea. The degree of correction obtained depends on several variables (some of which can be mastered), which explains why the results are not fully predictable. However, the overall results are satisfactory, provided the indications have been strictly selected. Per- and postoperatory complications are extremely rare. The main risk is early under-correction (particularly when the initial myopia is pronounced) or late over correction, mainly observed with radial keratotomy. Visual rehabilitation is much slower with the laser technique than after radial keratotomy. The two techniques are applied to patients aged from 20 to 40 years who have stable myopia, do not tolerate contact lenses and need an excellent sight for their professional or sporting activities.

Adult↗
PubMedDate not supplied

[The clinical characteristics of congenital and early myopia in preschool children].

Analysis of the clinical status of the eyes in congenital and early acquired myopia was carried out in preschool children with the aim of the differential diagnosis between these conditions. Myopia detected at the age of 2-4 was regarded as congenital, and myopia developing over the follow-up period in children with poor accommodation and hereditary aggravation, who had no myopia before, was considered as an acquired condition. Specific signs of the conditions in the children are enumerated.

Child, Preschool↗
PubMed1993

Radial keratotomy for myopia. American Academy of Ophthalmology.

The operation of radial keratotomy is undergoing evolution and development. A few hundred thousand radial keratotomy procedures have been performed during the past decade by approximately 10% of the ophthalmologists in the United States. Clinical and laboratory data have now defined a relative level of safety and effectiveness for the procedure. Published data indicate that radial keratotomy usually achieves partial improvement in uncorrected visual acuity in patients with non-progressive low and moderate amounts of myopia. Undercorrection occurs commonly, and the amount of correction cannot be predicted accurately for an individual patient. Overcorrection occurs less often using four incisions. The unpredictability of the refractive outcome stems from several factors, including: 1) the biologic variability from one individual to another, 2) variation in surgical techniques among surgeons, 3) difficulty in making all incisions uniformly, and 4) inability to measure and control the biomechanical properties of the cornea. This is probably why there is not unanimity among radial keratotomy surgeons regarding the most effective surgical technique. Improvements in the surgery are occurring, including the use of staged, titrated techniques, and some series of radial keratotomy cases have reported better uniformity and predictability of outcome. The potential of this procedure to render good visual acuity without glasses or contact lenses must be weighed against its known risks. Refractive side effects include anisometropia (imbalanced vision between the two eyes), increased astigmatism, and symptomatic presbyopia (loss of near focus in middle life). Other common, usually less severe side effects include prolonged unstable vision and mild glare. Uncommon, but potentially binding, complications include ocular infection and traumatic rupture of the cornea at the keratotomy scars. The goal of radial keratotomy is to correct the refractive error of myopia. It also may serve to improve cosmetic appearance if the patient does not require glasses after surgery. It is elective surgery because other alternatives are available for the management of myopia, including conventional glasses and contact lenses. In addition, other refractive keratoplasty procedures are available, including excimer laser photorefractive keratectomy, keratomileusis and epikeratoplasty. Selection of the best alternative for the management of myopia in an individual patient should be based on the patient's personal needs and on the ophthalmologist's and patient's assessment of the risks and benefits of the available modes of correction.

Humans↗
PubMed1993

[Early change of visual function in high myopia--measured and analyzed by octopus automated perimeter].

To evaluate the early changes of visual function in high myopic eyes, visual field examinations were performed using an Octopus 201 automated perimeter to 206 eyes of 120 patients. Corrected visual acuities were better than 0.8 and there were no abnormal findings except tigroid fundus change. 64 eyes of 38 patients were selected as a control group, whose refractive degrees were between +1.0D and -1.0D, corrected visual acuities were better than 1.0. The correlations of visual field changes with age, refractive degrees, axial length and sex were investigated. The total loss of high myopia group and the control group was compared, and changes in certain members of the high myopia group were followed up. The results were as follows: 1) Compared to the control group, the high myopia group had remarkably great loss. It revealed that the functional changes occurred already in the tigroid fundus stage. 2) Refractive degrees and axial length showed a significant positive correlation with total loss. This indicated that the refractive degrees and axial length played important roles in determining the visual field change of high myopic eyes. 3) Age and sex showed no statistically significant correlations with total loss. 4) The mean loss of the upper temporal quadrant and 11 degrees-20 degrees annular area were the largest. It appeared that the earliest changes in high myopia possibly began from the lower temporal region of the disc. 5) In the follow-up study, the loss increased persistently in the whole field, especially in the upper temporal and 11 degrees-20 degrees area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

PRK using an absorbing cell delivery system for correction of myopia from 4 to 26 D in 3251 eyes.

An ophthalmic laser unit with a Lambda-Physik LPX excimer emitting 193 nm and a unique beam shaping system was designed at the Complex "Eye Microsurgery." An absorbing cell, used as the main element of the delivery system, allowed us to obtain a precise profile of the laser energy density on the patient's cornea, smoothly changing the corneal refraction with each shot in the whole ablation area. The absorbing cell also allowed for varying the shape of distribution of radiation energy density depending on the patient's corneal shape. We performed more than 7000 photorefractive keratectomy laser operations in myopic patients, and report results in 3251 myopic eyes (approximately 46%) from -4.00 to -26.00 D, up to 4 years after surgery. In eyes with myopia greater than 6.00 D, emmetropia was obtained in 48% of cases; 42% had a residual mild myopia within 5.00 D; and 12% had a residual myopia more than 3.00 D. The corneal haze disappeared in 48.8% of cases; haze not affecting the visual acuity remained in 39%; and clinically significant haze remained in 12.2%. These eyes required a powerful medication or repeated PRK. After surgery, 87.7% of patients needed no spectacle correction. Excimer laser PRK with the use of the forming system efficiently corrects high myopia.

Adolescent↗
PubMedDate not supplied

Photorefractive keratectomy for myopia: preliminary results in 147 eyes.

Excimer photorefractive keratectomy (PRK) was performed on 100 consecutive patients (147 eyes) for the correction of myopia. The follow up period ranged from 3 to 16 months (mean, 8). Preoperative myopia ranged from -1.75 to -8.75 D (mean -3.90 D). Patients were divided into three groups for analysis based upon their degree of preoperative myopia: mild (< or = 2.90 D), moderate (-3.00 to -5.90 D), and severe (> or = -6.00 D). Uncorrected visual acuity was 20/40 or better in 88.4% (130/147) overall; 97% of mild, 91% of moderate, and 68% of severely myopic patients. Preoperative astigmatism remained the primary cause of reduced uncorrected visual acuity. Postoperatively, 68% of patients overall had a spherical equivalent refraction within +/- 1.00 D. The majority of treated corneas had trace (53%) to mild (29%) subepithelial haze. One patient with severe myopia developed significant subepithelial opacification postoperatively with partial regression and loss of one line of best spectacle corrected visual acuity.

Adult↗
PubMed1995

Effect of target proximity on transient myopia induced by equidioptric stimuli.

Transient myopia may be exhibited after sustained focus on a near target. This appears to be related to the within-task accommodative response. Although proximally induced accommodation has been shown to produce considerable transient myopia under open-loop conditions, its effect under naturalistic closed-loop conditions remains unclear. Accordingly, the present study examined the effect of target distance on transient myopia for equidioptric stimuli (5 D). A Canon R-1 autorefractor was used to assess the pre- and post-task refractive state objectively. Two tasks were performed monocularly and consisted of either accommodating on a near target at 20 cm (5 D) or a far target at 6 m viewed through a -5 D lens. The former task involved both blur and proximally induced accommodation, whereas the latter consisted of a blur stimulus only. Similar amounts of transient myopia were found under both conditions. These equivalent responses may be related to the relatively small output of proximally induced accommodation believed to be present under closed-loop conditions.

Accommodation, Ocular↗
PubMed1977

Adaptation to hydrogel contact lenses: variations in myopia and corneal curvature measurements.

Forty patients wearing lenses (soflens) were examined regularly for 3 months. During the first month the mean myopia gradually increased to 0.12 D more myopia and increased linearly to 0.50 D more myopia at 3 months. The mean corneal curvature flattened during the first 3 weeks, but steepened to about 0.37 D at 3 months. The process of myopia changes are not attributed solely to the anterior corneal curvature, but may also be the result of variations in the posterior corneal curvature, corneal thickness and index refraction as well as a change in the depth of the anterior chamber.

Adult↗
PubMed1996

LASIK for high myopia: one year experience.

BACKGROUND AND OBJECTIVE: Laser in situ keratomileusis (LASIK) is a technique combining the advantages of lamellar corneal surgery (not disturbing Bowman's layer) with the precision of excimer laser surgery. It can be used to correct myopia in a wide range of diopters. In this study we present our data on the first 34 consecutive cases of myopia correction by LASIK. PATIENTS AND METHODS: Thirty four eyes of 27 patients with myopia ranging from -10.00 to -22.50 diopters (D) were operated with LASIK. The follow-up was from six months to one year. The mean age was 33.02 +/- 7.98 years, 32.4% were males and 67.6% were females. Surgery was always performed with the Chiron Automated corneal shaper resecting a corneal flap of 160 mu and then ablating the stromal bed (OZ 4.50 mm) with the Summit OmniMed 5.0 excimer laser. The parameters used to assess the results were predictability, safety (variation of spectacle corrected visual acuity), stability, and patient satisfaction. RESULTS: Of the patients, 67.65% were between -1.00 and +1.00 at 6 months; 44.11% of eyes retained the same spectacle corrected visual acuity, 11.76% gained 1 line, 26.47% gained 2 lines, 8.82% lost 1 line and 8.82% lost 2 lines. Refraction at 1 month was 0.07 +/- 1.99 (range, -4.00 to +4.00); at 3 months 0.61 +/- 1.69 (range, -4.25 to +2.25); and at 6 months 0.81 +/- 1.71 (range, -4.75 to +2.25). Of the patients, 85.3% were happy with the procedure. Complications included two dislocated caps in the immediately post-operative period and two cases of epithelial ingrowth under the cap. Two eyes developed irregular astigmatism. These complications were found in the first two sessions of surgery and are related to the learning curve of the method. CONCLUSION: Results suggest that LASIK is a viable method for correction of high myopia with few complications and may have advantages over keratomileusis and PRK as it combines the best features of both methods--it preserves Bowman's layer and has the excimer laser precision. Refining the nomogram of ablation should result in even better results.

Adult↗
PubMed1996

[Spatial contrast sensitivity in patients with severe myopia].

PURPOSE: The purpose of this study was to assess the effects of amount of myopia, axial elongation staphyloma and type of optical correction on contrast sensitivity of high myopic subjects. METHODS: Fifty-one patients (91 eyes) were selected on the following qualifications: myopia > or = 8 dpt and/or axial length > or = 26 mm, and visual acuity > or = 0.1 recorded through spectacle lenses. Contrast sensitivity was measured using a "Moniteur Ophtalmologique" for all subjects when corrected with spectacle lenses, and thereafter on a lot of patients (50 eyes) wearing a contact lens. RESULTS: Contrast sensitivity obtained with spectacle lenses was significantly decreased over the whole spatial frequency range. The higher the spatial frequency was, the lower contrast sensitivity was. The impairment increased with the amount of myopia and axial length, but without positive correlation. Contrast sensitivity was significantly lower for only the three highest spatial frequencies measured (6.4; 12.8 and 25.6 c/deg), when a staphyloma (n = 52) was present by comparison with results obtained for eyes without staphyloma (n = 39). Differences between the two situations (spectacle lens vs. contact lens) were not significant for eyes wearing daily spectacle lenses; conversely, for myopic subjects generally fitted with contact lenses, contrast sensitivity with contact lenses was significantly better than that measured with spectacles for the three highest spatial frequencies tested. CONCLUSION: This suggests that the decrease in contrast sensitivity measured in high myopia is related to defects in the optical and neuro-retinal systems.

Adult↗
PubMed1995

[The correlation between changes of static central visual fields and posterior polar lesions in high myopia].

The static central visual fields tested by an Octopus Field Analyzer and posterior polar lesions in 53 cases with high myopia were investigated. Cases with low and moderate degrees of myopia were the controls. The results demonstrate that the visual field defects are present in the high myopic eyes and they are related to the degree of high myopia, the age of the patient and the severity of the posterior polar lesion. The visual field defects present multiform and multilevel in character and they do not completely correspond to the fundus lesions. The appearance of central relative scotomata in high myopic eyes detected by a quantified automated perimeter is prior to the appearance of macular lesions seen under an ophthalmoscope. Therefore, the quantified automated central visual field examination is helpful to the early diagnosis of macular disease in high myopia.

Adolescent↗
PubMed1996

[An analysis on therapeutic effects of posterior scleral support operation for treatment of myopia].

OBJECTIVE: The therapeutic effects of modified posterior scleral support operation for treatment of myopia and its operative effect on ocular axial length in high myopia were analyzed. METHOD: Among 78 cases 151 myopic eyes having undergone this operation and followed for 6-12 months, there were 23 cases (43 eyes) whose mean ocular axial length was compared with that of matched 20 cases (39 eyes) of myopia having undergone radial keratotomy alone and that of matched 19 cases (38 eyes) without any operation. RESULT: The results showed significant differences. CONCLUSION: The modified operation is safe, of simple operative procedure and has definite effect on preventing the lengthening of ocular axial length in high myopia.

Adolescent↗
PubMed1996

[Foveal cone densitometry in high myopia].

We performed foveal cone densitometry using a modified fundus camera in 17 eyes of 17 normal subjects (age range, 20 to 47 yr, refractive error, +2.0 to -2.5 D) and 15 eyes of 15 high myopia subjects with normal visual acuity (age range, 18 to 46 yr, refractive error, -9.0 to -14.5 D). After fully bleaching, the density of photopigment was measured for 7 minutes by a test spot of 562 nm in wavelength and 1 degree in diameter, focussed on the fovea. Two-way density and the time constant of pigment regeneration were calculated. No significant difference was found in two-way density between the two groups. The time constant in high myopia (161.6 +/- 36.6 sec), however, was significantly increased (p < 0.01), compared with normals (124.0 +/- 28.7 sec). To study the correlation of psychophysical visual function, we performed a photostress recovery test, which revealed a significant delay of the recovery time in high myopia (p < 0.01). These results suggest that a delay in foveal cone pigment kinetics precedes loss of cone cells or chorioretinal degeneration in high myopia.

Adolescent↗
PubMedDate not supplied

[The correction of myopia by radial keratotomy].

PURPOSE: to determine the efficiency and the predictability of the operation in different stages of myopia without help from corneal pachymetry. METHOD: 28 patients (43 eyes) who had been operated on with myopia between -1.5 and -12D were reviewed after 3,6 and 12 month from the operation. Simple radial keratotomy was done. RESULTS: better visual acuity with no correction. Visual acuity with admitted correction (max 3D) in comparison with the other eye was substantially improved in all cases. The only postoperative complication was under correction, frequent in myopia more than 6D. CONCLUSIONS: refractive keratotomy seems to be necessary in single eye myopia and anisometropia.

Adolescent↗
PubMed1996

[Effectiveness of posterior scleroplasty in progressive myopia in children].

The authors evaluated the long-term results of posterior scleroplasty in a group 51 children (74 eyes) with progressive myopia followed up 2-4 years after surgery. Stabilization of myopia developed in the axial length of the bulbus in 78% of the children and in objective refraction in 85% patients. In 15-22% of the patients myopia progressed but only by 0.4 D per year. No serious complications were observed or after operation. The authors draw attention of ophthalmic surgeons to scleroplasty because in has a marked effect on the preventive of progressing severe myopia and thus for the long term preservation of satisfactory visual functions.

Adolescent↗