Actual Refractive Error Research Articles

Postoperative Refractive Error After Simultaneous Vitrectomy and Cataract Surgery

To evaluate the effect of vitrectomy on postoperative refraction after simultaneous vitrectomy and cataract surgery. We compared the spread between predicted and actual refractions in 206 eyes after a simultaneous vitrectomy, phacoemulsification, aspiration and acrylic lens insertion (combined surgery group), and in 67 eyes after cataract surgery only (cataract surgery group) as control. A vitrectomy was performed for diabetic retinopathy in 127 eyes, macular hole in 32 eyes, rhegmatogenous retinal detachment in 16 eyes, branch retinal vein occlusion in 15 eyes, and other conditions in 26 eyes. In the combined surgery group, 79 eyes had a gas tamponade after insertion of the intraocular lens. The spread between predicted and actual refractions was - 0.05 +/- 1.18 diopters (average +/- SD) in the combined surgery group and +0.55 +/- 1.32 D in the cataract surgery group. The actual refractive errors in the combined surgery group were found to shift toward myopia when compared with the controls. Among the combined surgery group, 127 eyes without a gas tamponade showed a postoperative refractive error of +0.14 +/- 1.11 D, while 79 eyes with a gas tamponade demonstrated an error of -0.36 +/- 1.22 D. Use of a gas tamponade in the combined surgery group increased the myopic change and was thought to have pressed the intraocular lens forward.

Predicted Versus Actual Postoperative Refractive Error After Simultaneous Vitrectomy and Cataract Surgery

We compared the spread between predicted and postoperative actual refractive errors after simultaneous vitrectomy, phacoemulsification, aspiration, and acryl lens insertion and after cataract surgery alone. Cataract surgery and vitrectomy (combined surgery group) were performed in 185 eyes, and cataract surgery only (cataract surgery group) in 63 eyes. Vitrectomy was needed for diabetic retinopathy in 104 eyes, macular hole in 26 eyes, rhegmatogenous retinal detachment in 25 eyes, and other conditions in 30 eyes. The spread between predicted and actual refractive errors were +0.19 +/- 1.24 D (mean +/- standard deviation) in the combined surgery group and +0.91 +/- 1.40 D in the cataract surgery group. Gas tamponade in the combined surgery group increased the myopic change more than anything else. Actual refractive errors in the combined surgery group were found to shift to myopia more than in the cataract surgery group. Gas tamponade was considered to press the intraocular lens forward in the combined surgery group.

Control of the myopic shift in modified Badal optometer

SummaryRefractive error measurements made with the Badal optometer typically register more myopia than is actually present. In this paper we measured the influence of the image size on the end‐point of a Badal optometer's refractive error measurement. The optometer was modified with a camera's zoom lens in such a way that the retinal image size could be controlled. It was found that retinal image size is a major factor in controlling the subjective endpoint. When retinal image size is diminished rather than increased as the target approaches the subject, as is the case under normal circumstances, the perceived endpoint more closely agrees with the actual refractive error.

Control of the myopic shift in modified Badal optometer

Refractive error measurements made with the Badal optometer typically register more myopia than is actually present. In this paper we measured the influence of the image size on the endpoint of a Badal optometer's refractive error measurement. The optometer was modified with a camera's zoom lens in such a way that the retinal image size could be controlled. It was found that retinal image size is a major factor)n controlling the subjective endpoint. When retinal image size is diminished rather than increased as the target approaches the subject, as is the case under normal circumstances, the perceived endpoint more closely agrees with the actual refractive error.

Using the surgical result in the first eye to calculate intraocular lens power for the second eye

This paper examines the possibility of using the surgical result in the first eye when planning the intraocular lens power for the second eye. Two methods were considered: (1) an empirical method by which one regards the second procedure as a repeat of the one in the first eye and calculates the power from the actual refractive error obtained in the first eye and (2) a theoretical method by which one measures the pseudophakic anterior chamber depth (ACD) of the first eye and uses this value to plan for the second eye. Based on the data from 136 second eye procedures using extracapsular cataract extraction, the prediction error of the empirical method ranged from -10.5 to +9.5 diopters. The error of the theoretical method ranged from -2.3 to +2.8 diopters, which was significantly more accurate than the empirical method (P < .001). We conclude that the fellow eye ACD may be used as a guideline for the assumed ACD of the second eye. However, such use of the fellow eye ACD could not be shown to improve power calculation predictions significantly.

The Effect of Cataract Type on the Intraocular Lens Power Calculation Using the SRK Formula

OBJECTIVE: To evaluate the effect of the cataract type on the preoperative axial length measurements by ultrasonography, the intraocular lens (IOL) power calculation and the actual postoperative refractive error using the SRK formula. STUDY DESIGN: Comparative study of preand postoperative biometry data and determination of the refractive errors 3–6 months after surgery. SETTING: University Eye Clinic of Ioannina, Greece. PATIENTS: 145 adults divided into four groups according to the cataract type: group A, subcapsular; group B, nuclear; group C, mature and group D, intumescent. MAIN OUTCOME MEASURES: Preoperatively—measurements of axial length and calculation of IOL power using the SRK formula and aiming at emmetropia. Postoperatively—measurements of axial length and refraction. RESULTS: Statistical analysis (one-way analysis of variance) showed no significant differences between: (1) the mean values of differences in pre- and postoperative biometry ( F = 0.26, P = 0.85) and (2) the mean values of actual refractive error ( F = 2.34, P = 0.08), among the four groups of patients. CONCLUSIONS: The cataract type itself does not seem to influence significantly either the preoperative biometry and consequently the intraocular lens power calculation, or the actual postoperative refractive error, using the SRK formula.