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PubMedDate not supplied

Influence of ablation parameters on refractive changes after phototherapeutic keratectomy.

PURPOSE: The aim of the current study was to control the hypothetical effects of decreased laser energy delivered to the peripheral cornea during phototherapeutic keratectomy (PTK) and provide quantitative calculation of induced low and high order aberrations. METHODS: We employed a model eye to simulate the refractive effect of homogeneous laser corneal irradiation, as in PTK, for different laser fluences (range 125 to 225 mJ/cm2) and treatment depths up to 200 microm. RESULTS: The hyperopic shift induced by the relatively lower energy delivered at the peripheral ablation zone during PTK was proportional to the treatment depth and inversely proportional to the energy fluence. The hyperopic shift calculated using the above ablation parameters was lower compared to previously reported clinical results. Higher order wavefront aberration (total root mean square) changes were of minimal significance for treatment depths up to 200 microm. CONCLUSIONS: After PTK, a hyperopic shift cannot be attributed to the energy delivery method alone. Modification of laser energy delivery algorithms may only minimize PTK-induced hyperopia.

Cornea↗
PubMedDate not supplied

Laser in situ keratomileusis for residual hyperopic astigmatism after conductive keratoplasty.

PURPOSE: To report a case of laser in situ keratomileusis (LASIK) in a patient with previous conductive keratoplasty. METHODS: A 48-year-old man underwent conductive keratoplasty for low hyperopic astigmatism (manifest refraction OD: +2.25 -0.50 x 77 degrees; OS: +2.50 -0.50 x 105 degrees). Three months postoperatively, UCVA was 20/25 and BSCVA was 20/20 in both eyes; manifest refraction OD: -0.25 -0.75 x 110 degrees; OS: +0.75 -0.75 x 50 degrees. Sixteen months after the operation, regression of refractive outcome was (manifest) OD: +1.75 -1.25 x 90 degrees; OS: +2.50 -0.50 x 85 degrees; UCVA was 20/40 in the right eye and 20/63 in the left eye and BSCVA was 20/20 in both eyes. LASIK was performed for hyperopic regression in the left eye using an automated microkeratome (Alcon SKBM, 130-microm plate; Aesculap-Meditec MEL 70 excimer laser). RESULTS: LASIK was uneventful and no intraoperative or postoperative complications related to the previous conductive keratoplasty procedure or LASIK were observed. Three months after LASIK and 19 months after the initial conductive keratoplasty, the patient's left eye was emmetropic; UCVA was 20/20(-2), BSCVA was 20/20 and manifest refraction was +0.25 -0.25 x 35 degrees. There was a uniform increase in topographical steepening. Visual acuity, refraction and topographic findings remained unchanged at 6 months. CONCLUSIONS: Even though our experience is limited, treatment of hyperopia with LASIK in an eye with refractive regression following previous conductive keratoplasty resulted in a predicted refractive outcome, with no complications, and improvement in visual acuity at 6 months follow-up.

Astigmatism↗
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↗
PubMedDate not supplied

Intraocular pressure measurements after conductive keratoplasty.

PURPOSE: To determine the possible impact of conductive keratoplasty (CK) on intraocular pressure (IOP) measurements. METHODS: A prospective, single-center, noncomparative interventional case series was performed. Baseline and postoperative IOPs were measured by Goldmann applanation tonometry in 32 eyes of 18 patients who underwent CK for hyperopia correction. Mean follow-up was 11.9 months (range: 8 to 18 months). RESULTS: After CK, a statistically significant decrease in the measured IOP was observed (before CK: 14.22+/-1.64 vs after CK: 12.66+/-2.21, P<.001). The change in IOP readings postoperatively was not correlated with age, sex, keratometric readings, or attempted correction. CONCLUSIONS: Despite the limitations due to the small number of patients enrolled in this study, the applanation tonometer appears to underestimate the true IOP after CK.

Adult↗
PubMedDate not supplied

Objective quality of vision in presbyopic and non-presbyopic patients after pseudoaccommodative advanced surface ablation.

PURPOSE: To analyze the objective quality of vision at 6 months postoperatively after pseudoaccommodative (presbyopic) advanced surface ablation (PASA). METHODS: The study comprised 62 eyes of 35 patients with 6-month follow-up that underwent primary or secondary treatments using PASA. Pre- and postoperative results of distance and near uncorrected visual acuity (UCVA), spherical aberration (coefficient of the Z12 Zernike polynomial), and the asphericity (Q) index were reviewed. The corresponding wavefront maps (total, low, and high order aberrations) and the corresponding point spread function and modulation transfer function (MTF) were also calculated. RESULTS: Our results show that PASA improves distance and near mean UCVA, increases negative spherical aberration and negative asphericity index, and improves the corresponding MTF. CONCLUSIONS: Pseudoaccommodative advanced surface ablation is a promising approach for the surgical correction of presbyopia with distance refractive error (myopia and hyperopia with or without astigmatism). This PASA technique could theoretically be used in non-presbyopic patients with refractive error or post cataract patients with monofocal intraocular lenses. The increase in negative spherical aberration and asphericity/eccentricity index seems to increase the depth of focus of the eye, improving the near vision and compensating the age-related lens changes. Rather than creating a multifocal cornea, PASA appears to create an improved aspheric (prolate) ablation profile.

Accommodation, Ocular↗
PubMedDate not supplied

Features of hyperopic LASIK in children.

PURPOSE: To evaluate the results of hyperopic LASIK in children and adolescents with accommodative strabismus and refractive amblyopia. METHODS: The procedures were conducted by standard methods of LASIK using a Technolas 217C excimer laser (Bausch & Lomb, Rochester, NY). RESULTS: LASIK resolved the accommodative components of strabismus by achieving stabilization of visual acuity and decrease (or disappearance) of amblyopia degree. All patients achieved binocular vision. CONCLUSIONS: Excimer laser correction of hyperopia and hyperopic astigmatism in children and adolescents has the potential to correct refractive errors, improve visual function in amblyopic eyes, correct accommodative strabismus, and improve binocular vision.

Adolescent↗
PubMed2006

[Binocular vision following refractive surgery in hyperopic patients].

PURPOSE: To evaluate the changes in binocular vision and ocular motility in hyperopic patients undergoing refractive surgery. METHODS: Prospective study of 31 consecutive patients who underwent bilateral refractive surgery for hyperopia between May 1999 and February 2002. The examination included best-corrected visual acuity, cycloplegic refraction, ocular motility, fusion at distance, stereopsis and fusional amplitudes, before and at one month, 3 months, 6 months, one year after surgery and annually thereafter. RESULTS: After refractive surgery, there were changes in visual acuity, residual hyperopic refractive errors, and anisometropic changes that influenced the oculomotor status. The most frequent sensory modifications were suppression at distance, with much less change in stereopsis. From the point of view of ocular motility, we found a significant tendency to esotropia in strabismic patients (p=0.003). In non-strabismic patients, we also found sensorimotor modifications, but of less intensity and with fewer consequences than in strabismic patients. Sensorial and/or motor decompensation appeared in 25% of strabismic patients, and asthenopia symptoms developed in 28.7% in the same group. CONCLUSIONS: Slight binocular modifications with no symptomatic consequences were found in patients with normal binocular vision. However ocular motility was modified towards esotropia in strabismic patients, binocular decompensation appeared in 25%, and 28.7% of them suffered from asthenopia.

Adolescent↗
PubMed1999

[Specific cases of normo-sensorial strabismus: accommodative microstrabismus].

This study shows that, in a population of microstrabic patients (N = 76), a regain of a normal stereoscopy was possible in 19.6 of the cases (14 cases). Of these patients, 14 were hyperopic. With the full hyperopic correction, the angle of deviation on the alternate cover test was 0.45 PD (range: 0 to 3 PD). Without correction the deviation increased to between 3 PD and 10 PD (mean: 6.3 PD). Ten patients presented an anisometropia between 0.75 D to 2.50 D. (mean: 1.4 D). All anisometropic patients were hyperopic and hyperopia was higher in the dominated eye in all these cases. These results demonstrate the interest of the definition of microtropia as a specific strabismological entity, which can be congenital or acquired and be influenced by accommodative factors. The incidence of anisometropia, as a consequence rather than a cause of the pathological dominance is discussed.

Accommodation, Ocular↗
PubMedDate not supplied

[Exotropia in black Cameroonians].

We carried out this study to increase our knowledge and understanding of exotropia (divergent strabismus) in general, but particularly in black people, in whom it occurs more frequently. We carried out a prospective study in the department of ophthalmology of Douala General Hospital from November 1991 to June 1998. All patients underwent oculomotor examination and skiascopye. In a series of 225 consecutive strabismus cases, we identified 147 cases of exotropia (59.51%) in 67 male patients (45.58%) and 80 female patients (54.42%). In 59.86% of these cases, exotropia was evident before the age of one year and 59.19% had amblyopia. The mean age at first examination was 17.04 years (+/- 12.12 years). Hyperopia was the most common form of ametropia (59.86%) and 39 patients (26.53%) had parents, children or siblings who also had exotropia. We found that exotropia was the most common form of strabismus in black people in Cameroon and that it spontaneously progressed to amblyopia in a significant number of cases. We therefore recommend early, active treatment.

Adolescent↗
PubMed2000

Effects of experimentally induced ametropia on the morphology and optical quality of the avian crystalline lens.

PURPOSE: To examine the effects of refractive error on avian lens morphology and optical quality. METHODS: Hatchling white leghorn chicks were unilaterally goggled for 7 days with either a form-deprivation goggle (n = 12), a -10 D defocus goggle (n = 12), or a +10 D defocus goggle (n = 12) to induce myopia and hyperopia. Optical quality of lenses (focal length and focal length variability) from treated and contralateral control eyes was assessed using a scanning laser apparatus. Lens morphology was examined by light and electron microscopy. RESULTS: Although the induction of refractive errors did not significantly alter lens size, shape, paraxial focal length, or average focal length, average focal length variability increased. Lenses from eyes goggled with form-deprivation and +10 D defocus goggles demonstrated a twofold increase in average focal length variability, when compared with their contralateral controls. The morphology of the lens is not altered by these experimental manipulations. CONCLUSIONS: This study provides evidence that the refractive development of the chick lens is not independent of the refractive development of the ocular globe and that chick lenticular development is influenced by both genetics and visual experience.

Animals↗
PubMed2000

Angle-supported refractive implantation in stable, adult accommodative esotropia.

A patient with hyperopia and accommodative esotropia was implanted bilaterally with hyperopic angle-supported refractive implants. Control of the esotropia was achieved as was some improvement in fusional ability. After three years, the endothelium remains healthy, the eye is quiet and control of the esotropia is maintained.

Accommodation, Ocular↗
PubMed2001

Biomicroscopic measurement of the optic disc with a high-power positive lens.

PURPOSE: To compare the magnification properties of four different indirect double aspheric fundus examination lenses for clinical disc biometry. METHODS: Experimental study in a model eye. The relationship between the true size of a fundus object and its image was calculated for each fundus lens for an ametropic range between -12.5 and +12.6 D using a slit lamp biomicroscope with adjustable beam length. RESULTS: Equations for determining the correction factor p (degrees per millimeter) were calculated for each fundus lens. The factor can be used in calculations to determine true optic disc size. The total change in magnification of the system from myopia to hyperopia was -21.1% to +24.0% (60-D lens; Volk Opticals, Mentor, OH), -12.9% to +16.2% (Volk super 66 stereo fundus lens), -13.2% to +13.9% (Volk 78-D lens), and -13.3% to +14.0% (Volk super-field NC lens). When the fundus lens position was altered im relation to the model eye by +/-2 mm under myopic conditions, the change in magnification of the system was -4.3% to +5.7% (60-D lens), -4.6% to +6.1% (66 stereo fundus lens), -4.9% to +6.3% (78-D lens), and -5.9% to +7.8% (super-field NC lens). In the hyperopic condition the change was -2.7% to +3.6%, -3.4% to +4.5%, -3.6% to +4.8%, and -4.5% to +6.0%. CONCLUSIONS: The study has shown that the use of a single magnification correction value for each fundus lens may not be appropriate. These findings have important implications for the way in which calculations for determining the true optic disc size and other structures of the posterior pole are performed using indirect biomicroscopy.

Diagnostic Techniques, Ophthalmological↗
PubMed2001

Differences in time course and visual requirements of ocular responses to lenses and diffusers.

PURPOSE: Myopia can be induced in chickens by having them wear either negative lenses (lens-compensation myopia [LCM]) or diffusers (form-deprivation myopia [FDM]), whereas positive lenses cause lens-compensation hyperopia (LCH). These three conditions were compared with respect to (i) their early time course and (ii) the effect of two manipulations of the lighting. METHODS: Longitudinal changes in ocular dimensions and refractive error were measured in chicks maintained under three different conditions: (i) wearing either -15 D lenses or diffusers in a normal light/dark cycle; (ii) wearing either +15 D lenses, -15 D lenses, or diffusers with brief periods of stroboscopic lights at the beginning and end of the dark period; (iii) wearing either +6 D lenses, -6 D lenses, or diffusers with the nights interrupted by brief periods of white light. In addition, scleral and choroidal proteoglycan synthesis was measured in eyes that wore positive lenses, negative lenses, or diffusers for 3 hours followed by different periods of darkness. RESULTS: (i) The time course of the changes in axial length over the first 72 hours was significantly faster in LCM than in FDM. Indeed, the diffusers did not begin to significantly affect the total length of the globe for 3 days, although the vitreous chamber had deepened after 9 hours, because the choroid thinned extremely rapidly (within 1 hour) with either diffusers or negative lenses. (ii) Scleral proteoglycan synthesis was higher in eyes with negative lenses than in those with diffusers at 11 hours, but the reverse was true at 27 hours. (iii) Brief periods of stroboscopic light attenuated FDM more than LCM. (iv) In contrast, interruption of the nights by brief periods of light attenuated LCM more than FDM. (v) Neither lighting manipulation affected LCH. (vi) Choroidal proteoglycan synthesis decreased similarly with 3 hours of wearing either diffusers or negative lenses. CONCLUSIONS: Although both negative lenses and diffusers cause similar increases in the rate of ocular elongation, the responses differ in time course and in the effect of manipulations of the daily lighting. The responses to positive lenses differ from both of these.

Animals↗
PubMedDate not supplied

Genetic counseling of families with Best macular dystrophy.

We have examined 233 members of eight families with BMD. Of these, 169 were also examined with EOG. Sibships wherer greater than or equal to 80% of members were examined clinically and with EOG totaled 39. The results established both the validity and reliability of EOG testing in detecting people genetically affected with BMD. Hyperopia is established as an important manifestation of the disease. The visual prognosis of BMD is described.

Adolescent↗
PubMed2002

Intraocular pressure measurement after hyperopic LASIK.

PURPOSE: Previous studies have shown that Goldmann applanation tonometry (GAT) underestimates intraocular pressure (IOP) following photorefractive keratometry (PRK) and myopic laser in situ keratomileusis (LASIK). The purpose of this study was to evaluate the reliability of intraocular pressure (IOP) measurements by Goldmann applanation tonometry and pneumotonometry (PT) after hyperopic LASIK. METHODS: The IOPs of 20 eyes of 15 patients who underwent hyperopia LASIK were prospectively evaluated. Central and peripheral IOP were measured with GAT and PT, and central and peripheral corneal thicknesses were measured with ultrasonographic pachymetry. Patients were evaluated preoperatively and at 12 months postoperatively. RESULTS: Postoperative GAT measurements of IOP made from the central (13.1+/-2.7 mm Hg) and peripheral (13.9+/-3.3 mm Hg) corneal areas were significantly lower (P <0.001) than central IOP measured preoperatively (17.0+/-2.5 mm Hg). Postoperative PT measurements from the central (17.4+/-3.2 mm Hg) and peripheral (17.6+/-2.9 mm Hg) corneal areas were slightly lower than preoperative central IOP (18.4+/-2.4 mm Hg), but not statistically significant. There were no significant differences between central and peripheral IOP measurements using either method. CONCLUSION: The data demonstrate that GAT may underestimate IOP measurement, following hyperopic LASIK.

Adult↗
PubMed2002

[The vision of welders in France].

PURPOSE: A study was conducted to measure the impact of welding on the vision of welders. METHODOLOGY: This study was conducted in France by the occupational medicine staff of large companies on 1.131 people, namely 850 welders and 281 control subjects. This investigation included two examinations at the beginning and the end of a year. The investigative procedure examined the different welding processes, the percentage of working time spent on welding activity, the length of exposure in years, as well as the medical variables: the optical correction type and history of ocular traumatology. The Visiotest or the Ergovision were used for the visual examination, equipment in common use by occupational medicine departments. RESULTS: The welders were comparatively young (59.53% of them were less than 45 years old). Moreover, for 69.75% of the welders, more than 75% of their activity was devoted to welding. All currently used welding processes were represented, including the modern PLASMA-TIG welding process. No excessive blood alcohol levels were observed in all subjects, but welders did smoke slightly more than the control subjects (40% vs 33%). Self-medication was rather less frequent among the welders, except as regards the use of eye drops, where the proportions were clearly inverted. Optical correction for hyperopia was similar between the two groups; however, as regards myopia, the welders were corrected less often. Lastly, contact lens use was exceptional among the welders. Nearsightedness varied logically with age, but also, inexplicably, with the welding processes. Vision recovery time after exposure to glare was much longer among the welders, except for the PLASMA-TIG processes. No difference was observed in the other parameters of the study. No change in the visual functions studied was noted between the two examinations. DISCUSSION: The examination techniques used showed no impairment of the studied visual functions, probably because companies use protective and preventive eye care methods. Moreover this study is the first to examine the type of welding used by workers and particularly the modern PLASMA-TIG process. The vision recovery time after exposure to glare seems better for the PLASMA-TIG process may be the result of the lower luminous intensity of this process. CONCLUSION: This study was conducted for preventive purposes to contribute to better monitoring of safety and comfort for welding workers and has shown no alteration of the visual function among welders in general.

Adaptation, Ocular↗
PubMed2003

[Predictors of quality of life in refractive surgery].

PURPOSE: To investigate predictors of quality of life in refractive surgery: psychological status, quality of vision, visual acuity, and patient satisfaction. METHODS: In a prospective study, 143 patients were evaluated preoperatively and after the third postoperative month using the same questionnaire. Quality of vision, visual acuity, well-being, self-esteem, coping, and patient satisfaction were analyzed with 47 parameters. Refractive procedures included PRK, LASIK, and phakic IOL. Four groups of low (G1), medium (G2), and high myopia (G3) and hyperopia (G4) were individualized to compare the results. RESULTS: We noted a mean postoperative best corrected visual acuity (BCVA) of 20/25 or more for the G1, G2, and G4 groups. For the G3 group, the mean BCVA was increased, with a gain of two Snellen Lines from 20/50 to 20/32. Postoperative patient satisfaction improved, with a significant difference (p<0.05) in all groups. We noted no significant difference in all myopic groups in well-being and no significant decrease in G4. Concerning self-esteem and coping, scores improved, with a significant difference in G3 group (p<0.05). Quality of vision was directly correlated with improvement of quality of life (psychological status), satisfaction scores, and BCVA preoperatively and postoperatively in all patients, but no correlation was noted between visual acuity and patient satisfaction. CONCLUSION: In spite of good refractive results, modification of patient satisfaction depends on quality of vision and quality of life (psychological status) scores. These results give us a new tool that provides useful additional information in refractive surgery.

Adult↗
PubMed1992

Short term results with excimer laser-photo-refractive keratectomy.

The results at three months after photo-refractive keratectomy surgery (PRK) with the Meditec Mel 60 laser are discussed. A total of 86 eyes (18 hyperopes and 68 myopes) were followed. The predictability of +/- 1D in the myopia group of less than 6D was 86% and it was 68% in the myopia group of more than 6D. The predictability of +/- 2D was 96% in the group below 6D, and in the group of more than 6D it was 85%. In hyperopia, the mean refractive change was 2.7D and 44% of eyes were between +/- 1D at three months after Excimer laser surgery.

Adolescent↗