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Biomedical subjects

J Korynta

Publications and source records attributed to J Korynta.

At least 19 recordsLinked to original sources
PubMed2005

[Comparison of accuracy of refraction measurement in children up to the age of 15 years using the PowerRef II and by standard techniques].

OBJECTIVE: To establish whether refraction state in children up to the age of 15 years measured by photorefraction using PowerRef II device is comparable with values measured using common methods like skiascopy and autorefractor. Photorefraction is a quick method to determine refractive state from a distance without mydriasis and simultaneously in both eyes. It appears, therefore, to be a useful tool for measuring refractive errors of infants and older noncooperative subjects. However, its accuracy and reliability has been discussed. METHODS: In this study the authors assess accuracy of measurement of refractive errors by photorefraction in 40 children (19 boys, 21 girls) at the age ranging from 4 month to 15 years (average 4.8 years), divided according to their cooperation into two groups. The values of refraction acquired by photorefraction using PowerRef II device were compared with skiascopy in 23 noncooperative infants and with values of refraction from common autorefractor Nidek AR 600 in 17 cooperating children. RESULTS: Comparing results of both groups we have detected an average difference 0.41 D between skiascopy and photorefraction for spherical equivalents (0.45 for spheres, 0.42 for cylinders), average difference between spherical equivalents from autorefractor and photorefractor measurements was comparable: 0.52 D (0.51 for spheres, 0.55 for cylinders). CONCLUSION: Refractions measured by eccentric photorefraction with PowerRef II were comparable to those obtained by common methods of refraction measurement in children--i.e. skiascopy and autorefractor. Values of refraction were undervalued only in two cases of higher myopia during photorefraction measurement compared to autorefractor values. There was no significant shift by photorefraction measurement to myopic or hypermetropic values.

Adolescent↗
PubMed2002

[Calculation for emmetropic intraocular lenses in hypermetropia].

Authors evaluated postoperative refractive errors after implantation of intraocular lens at the set of 429 eyes. There predominated eyes with short axial length (AL) at this set: 304 eyes had AL < 22 mm, average AL was 21.54 mm. The basic point was to correct the linearity of SRK formula by different way from SRK II formula, while keeping the new formula simple to use. Authors reached following modification of A-constant in SRK formula: new A-constant = original A-constant + C, where C = 0,146*AL2 - 7,702*AL + 100,130.

Humans↗
PubMed2002

[Screening for threshold stages in retinopathy of prematurity].

The authors evaluated retrospectively the examination protocols of 208 children (400 eyes) treated by cryocoagulation on account of active retinopathy of premature infants (ROP). The objective was to assess the optimal timing for the onset of examination to record in time the threshold stages of ROP in children with different grades of maturity. The baseline point was the finding that before the 5th postnatal (pnt) and 31st postconception week (pcw) the threshold stage was not diagnosed in any child of the group. The highest incidence of threshold stages in all children was between the 36th and 37th postconception week. The first examination made between the 5th-6th postnatal or at first during the 31st postconception week is sufficient to cover initial threshold stages of ROP in children with different birth weights. Screening based on combination of the postnatal and postconception age is more accurate than evaluation by one criterion. Premature examinations are misleading and not valid for screening.

Birth Weight↗
PubMed2001

[A huge foreign body in the orbit].

The authors present an account on a two-year-old child which while playing pushed the broken end of a pencil into the orbit above the bulbus. With regard to the nature of the object it was extracted by two-stage surgery. The injury did not affect the child's ocular functions.

Child, Preschool↗
PubMed1999

Computer modeling of visual impairment caused by intraocular lens misalignment.

PURPOSE: To evaluate a computer program to modulate the visual impairment caused by intraocular lens (IOL) misalignment and visualize results obtained by numerical calculations. SETTING: Department of Ophthalmology, Medical Faculty of Charles University, Prague, Czech Republic. METHODS: The optic imagery of a Landolt circle was calculated using a ray-tracing computer program. Visual aberrations resulting from a decentered and/or tilted IOL were studied using this program and compared with theoretical calculations. RESULTS: The IOL decentration and/or tilt shifted the postoperative refractive errors toward myopia and astigmatism (oblique). The combination of IOL decentration and tilt produced a refractive error that depended on the relationship between the geometrical axes of the decentration and tilt. The refractive error can be enhanced or diminished depending on the relationship of these axes. CONCLUSIONS: These findings verify the results calculated by paraxial vergence equations. A ray-tracing program simulated the optic imagery for various kinds of IOL misalignment and IOL optic properties.

Astigmatism↗
PubMed1998

[Changes in corneal refraction after cataract surgery--comparison of the posterior limbic and the scleral tunnel incision].

The authors evaluate the results of keratometry in a group of 235 patients after surgery of cataract who were operated by the technique of posterior limbal and scleral tunnel section by the same surgeon. Posterior limbal section induced after surgery astigmatism, on average +4.0 D in the median section, the scleral tunnel section about +2.0 D. Astigmatism after the posterior limbal section improved spontaneously during the fourth month after surgery; if it persisted, it improved after discontinuation of the suture. Slight astigmatism after the posterior limbal section developed easily after four months following operation into astigmatism against the rule. Astigmatism after a scleral tunnel section disappeared after the fourth month following operation but did not develop against the rule. Both types of sections induced after surgery similar but negligible changes of the spheral corneal equivalent.

Astigmatism↗
PubMed1998

[Biometry of very short ocular bulbs].

The authors evaluate the postoperative refractive results of 53 patients with extremely short eyes (16.0-20.0 mm) after IOL implantation. As the SRK II formula underestimates the A-constant increase for very short eyes, the authors as a results of the analysis of the set of patients recommend the A-constant recalculation according to formula: A-constant increase = 0.429 x axl x axl - 18.732 x axl + 206.114 and then the calculation of emmetropizing IOL by SRK formula.

Eye↗
PubMed1998

[Treatment of scleral staphyloma by fixation of a fascial graft with Tissucol].

The authors describe the successful procedure used in treatment of a scleral staphyloma which developed on the hydrophthalmic bulbus of a three-year-old child three months after pars plana lensectomy. They covered the defect by an allogenic fascial graft and fixed it with the fibrin tissue glue Tissucol. The method is quick, simple and reliable.

Child, Preschool↗
PubMed1996

[Viscoexpression of the lens nucleus in extracapsular cataract extraction].

The author rates the frequency of peroperative complications during cataract extraction performed by continuous curvilinear capsulorhexis (CCC) and viscoexpression technique. The total number was 369 cases, the peroperative complication was noted in 8.1% cases. The relaxing incision of anterior capsule was noted in 17.1% of cases. The most frequent complication in cases without relaxing incision (82.9%) was asymetric implantation of IOL (sulcus-bag, 2.6%). In cases with relaxing incision (17.1%) the most frequent complication was posterior capsule rupture with subsequent anterior vitrectomy (7.9% from total of 17.1%).

Cataract Extraction↗
PubMed1995

[Importance of individualizing the formula for improving the accuracy of calculating emmetropia in intraocular lenses before cataract surgery].

The authors evaluated the individualized A-constants of 858 patients. These patients were divided into 12 groups according to the surgeon and the type of implanted IOL. The valuation of the results showed a marked discrepancy between the mean value of the individualized A-constant and the value recommended by the manufacturer. In this set of patients the individualization of the formula decreased the postoperative refractive error in some cases by 0.4 D for three-piece lenses and by 1.7 D for one-piece lenses.

Cataract Extraction↗
PubMed1994

[The accuracy of optical power calculations of intraocular lenses in cataract surgery].

The author selected 12 groups of patients (858 patients altogether). The operation was carried out by the same surgeon and the same type of IOL was implanted in each group. An individual A-constant was calculated for each patient. Using individualized A-constant for each group a postoperative refractive error was calculated for each patient. Following formulas were used for the calculation: SRK, SRK II, Holladay formula (A-constant), Holladay formula (surgeon factor) and SRK/T. No substantial difference between the results of formulas SRK, SRK II, Holladay formula (surgeon factor) and SRK/T was found. The postoperative refractive error +/- 1.0 D was found in the interval 65.6% - 67.8% for all these formulas. Holladay formula (A-constant) yielded the postoperative refractive error +/- 1.0 D in 62.2% of cases.

Cataract Extraction↗
PubMed1994

[Implantation of anterior chamber lenses].

From January 1989 till July 1993 85 anterior chamber lenses were implanted at the 1st Department of the 1st Medical School of the Charles University in Prague. In 30 cases the anterior chamber lenses were implanted primarily and in 55 cases as a secondary procedure. In all cases flexible lens of Kelman type was used. The incidence of postoperative complications was almost the same as was described in literature. The complications were less frequent after secondary implantations. After more extent loss of vitreous during extracapsular cataract extraction it is recommended to delay the implantation of anterior chamber lens at least after half a year. Final visual acuity 6/6-6/12 was achieved in 70% primary and in 85.5% secondary implantations.

Aged↗
PubMed1994

[Relation between postoperative refraction errors and decentration of the intraocular lens].

In a group of 51 patients the authors measured the position of the intraocular lens (the method was based on mathematical analysis of the Purkinje images position) and calculated the postoperative refractive error. The dependence of the postoperative refractive error on IOL position was analyzed and the results of the analysis were compared with the presumptions based on theoretical calculations. The results obtained from the measurement are very close to that assessed by the theoretical calculations. The IOL decentration in the eye causes the the shift of the postoperative refractive error towards myopia and it is probably the cause of the part of the postoperative refractive error.

Humans↗
PubMed1994

[From Beer's knife to the tunnel incision].

The authors present an account on the development of surgical techniques used in operations of cataract. Surgery of cataract was started on April 8, 1745 when the Frenchman Jaques Daviel made the first extraction of an opaque lens by limbal incision. This new method was enforced, however, very slowly and only after 100 years it finally celebrated victory over the hitherto widely used reclination. In the fifties of the present century a great advance in the surgery of cataract was the introduction of cryoextraction; at the First Ophthalmological Clinic a double-jacket instrument was designed which was filled with crushed CO2. The first cryoextraction was made at the authors' department on October 7, 1964, it was the very first operation of this type in Czechoslovakia.

Cataract Extraction↗