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[Laser coagulation of the cornea with a holmium:YAG laser for correction of hyperopia].
We present a new technique of hyperopic correction similar to radial thermokeratoplasty. A pulsed Ho: YAG laser was used that emitted radiation at 2.06 microns and was guided by a quartz fiber and a focusing hand piece. The penetration depth of this light in the cornea is about 400 microns. Eight or 16 concentric point coagulations result in steepening in the central cornea. This refractive change is inverse related to the distance to the cornea center, and it increases linearly with increasing laser pulse energy. In four blind eyes it was demonstrated that the parameters evaluated in cadaver eyes can be transferred to living eyes. Surprisingly, the refractive change so created of up to 5 dpt is stable within a period of 4 months. Immediately after surgery, concentric descemet folds can be detected, which gradually decrease within the period reported.
Radial thermokeratoplasty for the correction of hyperopia.
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Correction of hyperopia following radial keratotomy.
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Explanation for good visual acuity in uncorrected residual hyperopia and presbyopia after radial keratotomy.
It has been observed that, after radial keratotomy (RK), uncorrected residual hyperopes may have better visual acuity than expected and that some presbyopes, corrected only for distance, have adequate near-vision. We offer a possible explanation for these observations by showing that the increased spherical aberration after RK may produce a second focus 1.5 diopters or more in front of the principal focus of the eye.
Accommodative esotropia during the first year of life.
Two infants developed accommodative esotropia during their first six months of life. One infant, whose age at onset was 4 1/2 months, had 4.50 diopters of hyperopia. The second infant, whose age at onset was 5 months, had 3.50 diopters of hyperopia. In both infants, the eyes completely aligned with hyperopic correction. Two points are stressed. First, when the amount of hyperopia exceeds +3.00, consideration should be given to an accommodative element as the cause of the esotropia, even if the child is only 4 to 6 months old. Second, even with small angles of esotropia, an accommodative element should be considered, if there is a substantial amount of hyperopia.
Refractive plasticity of the developing chick eye.
We have developed a lightweight plastic goggle with rigid contact lens inserts that can be applied to the eyes of newly hatched chicks to explore the range and accuracy of the developmental mechanism that responds to retinal defocus. Convex and concave lenses of 5, 10, 15, 20 and +30 D were applied to one eye on the day of hatching. The chick eye responds accurately to defocus between -10 and +15 D, although hyperopia develops more rapidly than myopia. Beyond this range there is first a levelling off of the response and then a decrease. The resulting refractive errors are caused mainly by increases and decreases in axial length, although high levels of hyperopia are associated with corneal flattening. If +/- 10 D defocusing lenses are applied nine days after hatching the resulting myopia and hyperopia are equal to about 80% of the inducing power. After one week of inducing myopia and hyperopia with +/- 10 D lenses, the inducing lenses were reversed. In this case, the refractive error did not reach the power of the second lens after another week of wear. Instead, astigmatism in varying amounts (0-12 D) was produced, being greater when reversal was from plus to minus. Finally, astigmatism can also be produced by applying 9 D toric inducing lenses on the day of hatching. The astigmatism produced varies from 2 to 6 D, and the most myopic meridian coincides with the power meridian of the inducing lens. This astigmatism appears to be primarily due to corneal toricity.(ABSTRACT TRUNCATED AT 250 WORDS)
Hyperopic thermokeratoplasty: clinical evaluation.
A new procedure, hyperopic thermokeratoplasty (HTK), developed in the Soviet Union for the correction of hyperopia, uses controlled thermal burns of the corneal stroma with a retractable probe tip preset to penetrate the cornea at 95% depth. The coagulations are applied in a radial pattern for spherical hyperopia. Only the peripheral cornea is treated and the effect is titrated by varying the optical zone and number of rays. The thermal effect flattens the peripheral cornea and steepens the central cornea. In this report, we prospectively evaluated the refractive results of a group of 61 HTK patients. Mean preoperative spherical equivalent was 3.9 diopters (D). Mean follow-up to date is 5.2 months, with 44% of cases evaluated at six months and 31% at one year. The initial effect of surgery (at one day) was a mean decrease in hyperopia of 6.0 D (standard error of the mean [S.E.] = 0.3 D), resulting in a mean spherical equivalent of -2.1 D (S.E. = 0.2 D). There was a steep regression of effect between one day and two months at which point average refraction was close to emmetropia. After two months, there was a gradual but continuing regression of effect, leveling off after six months. At five to six months, 63% of cases were undercorrected by at least a diopter; at 9 to 12 months, 83% of cases were undercorrected. The overall change in spherical equivalent at each time increased as optical zone size decreased.(ABSTRACT TRUNCATED AT 250 WORDS)
A clinical study on the detection of strabismus, anisometropia or ametropia of children by simultaneous photography of the corneal and the fundus reflexes.
Twenty two strabismus and 106 straight eyed patients with anatomically normal eyes were first photographed with a conventional camera equipped with a weak 100 mm teleobjective and coaxial flashlight and then examined clinically. The possibility of detecting strabismus, anisometropias and ametropias in the photographs by noting the localisation of the corneal reflexes and examining the appearance and lightness of the fundus reflexes and their possible asymmetry were tested in a double blind study. Even small angled strabismus cases could be found because of the asymmetrical localisation of the corneal reflexes. In 18 of the 22 strabismus cases (82%) there was asymmetrical lightness of the fundus reflexes and the fundus reflex of the deviating eye was lighter than that of the fixating eye. All the straight eyed anisometropias of 3.0 diopters or more (five cases) were observed in the photographs because of the asymmetrical appearance of the fundus reflexes. In straight eyed anisometropias of under 3.0 diopters, the fundus reflexes were symmetrical in 90 cases and asymmetrical in 11 cases (11%). Only three out of eight hyperopias of fomr +4.5 to +6.0 diopters were found because of the light crescent in the low part of the pupil. All myopias of over -4.0 diopters (14 cases) were observed because of the light crescent appearance in the upper part of the pupil. No pupillary crescents appeared with refractions of less than -1.75 diopters myopia or less than +4.5 diopters hyperopia; 172 eyes came within this range. Even a technician can perform, without premedication, the method tested here for rapid and simple screening to detect strabismus and straight eyed anisometropias of 3.0 diopters or more in small children or other patients who do not co-operate well in normal clinical examination. Over -4.0 diopters myopias can also be found. The method was rather unreliable for finding hyperopias, presumably because no cycloplegic drops were used.
Optometric management of optically induced consecutive exotropia.
A 5-1/2 year old black female initially presenting with a moderate angle esotropia and latent hyperopia developed a large angle constant exotropia 2 years after final correction of her refractive error. The occurrence of consecutive exotropia as a result of optical correction of hyperopia has been documented infrequently in the ophthalmologic literature and has rarely been mentioned in the optometric literature. While the overall risk for occurrence of this complication from correction of hyperopia may be small, it is a problem which may occur and can be avoided. Unfortunately, there is only limited information about the various risk factors that should be monitored to avoid the occurrence of an optically induced consecutive exotropia. What is available with regard to evaluation and management is scant, and there are no case reports emphasizing optometric management which includes the use of lenses, occlusion and vision therapy. The purpose of this paper is to present a case report of optically induced consecutive exotropia followed by a summary of the available information from the optometric and ophthalmologic literature. This combined information will aid optometrists managing these patients to avoid the occurrence of this problem and better understand the various management aspects when it does occur.
[Refractive error and amblyopia in children].
The refractive status of 3,099 children was analyzed. The result showed that the incidence and degree of hyperopia decreased gradually and those of myopia increased along with the growing up of children in ametropia. In binocular refractive amblyopia, high and medium hyperopia and myopia in severe and medium amblyopia were significantly more than those in mild amblyopia. In monocular refractive amblyopia, high and medium hyperopia and high myopia in the amblyopic eyes were more than those in the nonamblyopic eyes. The refractive status of binocular esotropic amblyopia had no significant difference in various ages and degrees of amblyopia. There was also no significant difference between the refractive status of the amblyopic and nonamblyopic eyes in monocular esotropic amblyopia. It was considered that refractive amblyopia was closely related to high ametropia and the deviation of the eye might be the main cause of strabismic amblyopia.
Pigmentary glaucoma in the black population.
The pigment dispersion syndrome is associated with a secondary open-angle glaucoma most commonly found in young, myopic, white males. We studied 20 cases (38 eyes) of pigment dispersion syndrome in black individuals as defined by heavy deposition on the corneal endothelium and trabecular meshwork with increased intraocular pressure but no other ocular abnormalities. The 20 patients were a homogeneous group that was typified by older age distribution (average, 73 years), a preponderance of hyperopia (median refraction, +2.15 diopters spherical equivalent), female gender (19 women, one man), no iris transillumination defects (zero of 38 eyes), and flatter iris insertion into the ciliary body. We believe that this homogeneous group of black individuals with pigment dispersion and atypical features represents a pigment dispersion syndrome associated with older age, hyperopia, and female sex preponderance, in the black race.
Relationship of serum glucose concentration to changes in refraction.
The effect of chronic changes in serum glucose concentration on refraction was studied by increasing the dose of insulin or chlorpropamide in 10 diabetic patients who initially had relatively high glucose concentrations. In every case when serum glucose concentration was reduced the vision became less myopic or more hyperopic. To assess acute changes. 10 diabetics (including four with aphakic eyes) were given an intravenous injection of glucose. In patients with intact lenses the vision became more myopic or less hyperopic following the administration of glucose, but in the aphakic eyes hyperopia increased. It is concluded from both the acute and chronic studies that higher levels of serum glucose concentration produce myopia and lower levels produce hyperopia. Furthermore, these changes are related to changes in the optical properties of the crystallin lens.
A nation-wide study of myopia prevalence in Israel. Findings in a population of 312,149 young adults.
We conducted a nation-wide survey of the Prevalences of Myopia and other refractive errors in Israel, from data of medical examinations of an unselected population of 312,149 subjects ages 17 to 19 years. 80.47% of the population were emmetropic in both eyes. Myopia in both eyes was found in 16.27% of the population. The prevalence of monocular myopia was 1.69%. Manifest hyperopia in both eyes was found in 0.93% and astigmatism at least in one eye was found in 7.13%. The various errors of refraction (myopia, hyperopia and astigmatism) were more common among females.
[The measurement of visual refraction of pupils].
The ocular refraction was measured by applying 1% atropine eye-drops for 3 days in 5,458 eyes (male 2,944, female 2,514) of the pupils aged 7-17 in rural areas. The results were as follows: the majority of the pupils had hyperopia (male 84.71%, female 80.55%); the frequency of the measurements was not in normal distribution; the degree of far-sight began to recede and gradually become converted to myopias with advancing age but varying greatly between age-groups. The myopias began to appear at the age of 9 and increased rapidly at the age of 14 for girls and 15 for boys. From then on the rate of conversion continued to increase with schoolgirls more than schoolboys and, as a result, formed "the dangerous stage of myopia", the values of physiological visual refraction were shown as follows: pupils aged 7-9 + 2.00 D- + 2.50 D, aged 10-13 + 1.50 D- + 1.75 D, aged 14-17 + 1.00 D- + 1.25 D. The possibility of pathological hyperopia was greater if the pupils aged 7-9 and the value of visual refraction over +3.75 D, aged 10-13 had the value over +3.00 D and aged 14-17 had the value +2.50 D. The possibility of developing myopia was great in those pupils aged 7-9 whose value was under +1.00 D and in those aged 10-17 whose value was under +0.50 D. The deprived vision of the pupils should be routinely corrected by skiascopy.
Refractive error in a Puerto Rican rural population.
The distribution of refractive error in migrant workers and their families living in Patillas, Puerto Rico was studied. A total of 1,109 patients with an age range of 5-81 years and above was screened using the modified clinical technique. The refractive distribution of the total screened indicated that 10.2 percent had myopia, 17.7 percent had hyperopia and the rest had a combination of other refractive error (astigmatism, anisometropia and emmetropia). Myopia was most frequent in the age group 11-20 years (16.7 percent) and 21-30 years (16.8 percent) and decreased in the younger and older age groups. Frequency of hyperopia increased from age 31-70 years and then decreased thereafter. Hyperopic astigmatism was more common than myopic astigmatism across all age groups.
Experimental studies of emmetropization in the chick.
The eyes of neonates grow from ametropia (refractive error) toward emmetropia. Whether or not this 'emmetropization' is visually guided is controversial. I describe experiments which demonstrate that in the chick refractive state is used to regulate the growth of the eye's vitreous chamber in order to achieve emmetropia from hyperopia or myopia that is induced by different visual deprivations. I discuss several studies that begin to examine the neural pathways that might be involved in the control of eye growth. Optic nerve section was used to examine the level of visual processing necessary for the control of eye growth. Eyes in which the optic nerve has been cut can still grow in the appropriate direction to correct induced hyperopia or myopia. Nevertheless, an intact optic nerve is necessary for normal refractions to be achieved; eyes with optic nerve section overshoot control levels and reverse the sign of the initial refractive error. These findings suggest that eye growth in chicks is controlled by an intraocular mechanism and possibly by a brain-mediated mechanism as well. The hypothesis that ocular accommodation is integral to the control of eye growth was also tested. Complete recovery from induced refractive errors was achieved even when accommodation had been abolished by lesions of the Edinger-Westphal nucleus. The elimination of accommodation did not prevent the ability of chick eyes to compensate for the defocus of spectacle lenses. These results suggest that accommodation is not necessary for the control of eye growth.
Apparent cleavage of the retinal nerve fiber layer in asymptomatic eyes with high myopia.
The appearance of the retinal nerve fiber layer was studied in one eye of 203 normal Asians (59 with high myopia greater than or equal to -5 D, and 144 with emmetropia or hyperopia). "Cleavage" of the retinal nerve fiber layer was observed in 3 of these 59 highly myopic eyes, but there was no significant damage to either the retinal pigment epithelium or the choroid. In contrast, no cleavage was observed in the other 144 emmetropic or hyperopic eyes. High myopia (P = 0.0237, Fisher's exact test) was a significant risk factor for "cleavage" development in the retinal nerve fiber layer. The occurrence of a defect (nerve fiber loss) in the retinal nerve fiber layer in severe myopia (5/59, 8%) was also greater than that in either emmetropia or hyperopia (2/144, 1%; P = 0.0229). These results indicate that subtle changes can occur in the appearance of the retinal nerve fiber layer of the eye in some patients with asymptomatic myopia.