Measurement of Aniseikonia Tolerance in Binocular Fusion.

SIGNIFICANCE: The determination of aniseikonia tolerance may aid in developing optimal treatment plans for cataract surgery, refractive surgery, and refractive correction with glasses and contact lenses. PURPOSE: This study aimed to measure aniseikonia tolerance. METHODS: We included 33 patients (mean age ± standard deviation, 28.9 ± 6.4 years; male/female, 12:21) with anisometropia ≤1.0 D and best spectacle-corrected visual acuity of 20/20 or more in both eyes, with no ophthalmologic disease other than refractive errors and no history of ocular surgery. The exclusion criteria were anisometropia >1.0 D, axial length difference >0.5 mm, corneal refractive power difference >0.5 D, astigmatism >3.0 D, stereoacuity threshold >100 arcsec according to the Titmus Stereo Test, and >0% aniseikonia according to the New Aniseikonia Test. Aniseikonia tolerance was assessed using Eyemark Hello, a haploscope using gaze detection technology. Although the optotype of one eye was enlarged or reduced at a speed of 2%/s, the patients were instructed to press a button on the controller to indicate blurring, flickering, and diplopia. The value at which the patient responded was considered the aniseikonia tolerance value and assessed thrice per eye, five times if the values were highly variable, and then averaged. RESULTS: The mean aniseikonia tolerance was approximately 3%; the median value was approximately 2% (range, 1.0 to 11.5%; dominant eye, 3.3 ± 2.6%; nondominant eye, 2.9 ± 1.8%). No significant difference in aniseikonia tolerance between the dominant and nondominant eyes was observed for the enlarged optotypes. No case showed changes in the ocular alignment before discomfort occurred. No significant correlation was observed between aniseikonia tolerance and anisometropia, axial length difference, corneal power difference, and ocular deviation. CONCLUSIONS: Aniseikonia should be maintained at <2% for a comfortable visual environment. Aniseikonia tolerance may be an important indicator for cataract surgery, refractive surgery, and spectacle correction.

Evaluation of ocular biometry in the Japanese population using a multicenter approach: Prospective observational study.

This prospective observational study aimed to evaluate the ocular biometry of Japanese people through a multicenter approach. The uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) in the log minimum angle of resolution (logMAR), subjective and objective spherical equivalent values (SE) of ocular refraction, anterior and posterior corneal curvature (ACC and PCC, respectively), anterior and posterior corneal asphericity (ACA and PCA, respectively), central corneal thickness (CCT), anterior chamber depth (ACD), and ocular axial length (AL) were measured in the eyes of 250 participants (mean age = 46.5 ± 18.0 years, range: 20-90 years) across five institutions in Japan. The mean UDVA, CDVA, subjective SE, objective SE, ACC, PCC, ACA, PCA, CCT, ACD, and AL were 0.68, -0.08, -2.42 D, -2.66 D, 7.77 mm, 6.33 mm, -0.31, -0.39, 0.55 mm, 2.92 mm, and 24.78 mm, respectively. Age-related changes and sex-based differences were noted in the visual acuity, refraction, corneal shape, ACD, and AL. Our results serve as basis for future studies aiming to develop refractive correction methods and various vision-related fields.

Prediction of distance visual acuity in presbyopic astigmatic subjects.

This study was aimed to determine the effect of the amount of astigmatism on distance visual acuity, and to provide a prediction formula of visual acuity according to astigmatism, in a presbyopic population. We comprised 318 eyes of 318 consecutive patients (158 phakic and 160 pseudophakic subjects) without any eye diseases, except for refractive errors with astigmatism of 3 diopter or less. We assessed the relationship of the spherical equivalent visual acuity (SEVA) with astigmatism, and also provided a regression formula of visual acuity according to astigmatism in such subjects. We found a significant correlation between the SEVA and the amount of astigmatism (r = 0.715, p < 0.001) in the entire study population. We obtained similar results, not only in phakic eyes (r = 0.718, p < 0.001), but also in pseudophakic eyes (r = 0.717, p < 0.001). The regression formula was expressed as follows: y = 0.017x2 + 0.125x - 0.116 (R2 = 0.544), where y = logMAR SEVA, and x = astigmatism. We also found no significant differences in the SEVA for matched comparison among the with-the-rule (WTR), against-the-rule (ATR), and oblique (OBL) astigmatism subgroups (p = 0.922). These regression formulas may be clinically beneficial not only for estimating the visual prognosis after astigmatic correction, but also for determining the surgical indication of astigmatic correction.

Comparison of Conventional Keratometry and Total Keratometry in Normal Eyes.

PURPOSE: The relationship between conventional keratometry and total keratometry has not been fully investigated. This study was aimed at conventional keratometry measured with the automated keratometer and total keratometry with the corneal tomographer in ophthalmologically normal subjects. METHODS: We enrolled fifty eyes of 50 consecutive subjects (mean age ± standard deviation, 34.9 ± 8.0 years) who have no ophthalmologic diseases, other than refractive errors, with no history of ocular surgery. Conventional keratometry was measured with the automated keratometer. The total keratometry, the true net power (TNP), and the total corneal refractive power (TCRP) were measured with the Scheimpflug camera, and the real power (RP) was measured with anterior segment optical coherence tomography (As-OCT). Anterior keratometries (Km and AvgK) were also measured with the Scheimpflug camera and the As-OCT, respectively. RESULTS: Conventional keratometry was 43.64 ± 1.48 D, which was significantly higher than the TCRP (42.94 ± 1.45 D, p = 0.042), the TNP (42.13 ± 1.37 D, p < 0.001), and the RP (42.62 ± 1.39 D, p = 0.001, Dunnett's test). We found significant correlations between conventional keratometry and each total corneal power (the TCRP (Pearson's correlation coefficient r = 0.986, p < 0.001), the TNP (r = 0.986, p < 0.001), the RP (r = 0.987, p < 0.001), the Km (r = 0.990, p < 0.001), and the AvgK (r = 0.991, p < 0.001)). The intraclass correlations of conventional keratometry with the TCRP, the TNP, the RP, the Km, and the AvgK were 0.986, 0.983, 0.985, 0.990, and 0.990, respectively. We found no significant differences in the keratometric data measured with the automated keratometer, the Scheimpflug camera, and the As-OCT (ANOVA, p = 0.729). CONCLUSIONS: Conventional keratometry was significantly larger than total keratometry, by approximately 0.70 to 1.52 D, in ophthalmologically normal subjects. By contrast, there were no significant differences in the keratometric data among the three devices. It is suggested that conventional keratometry overestimates the total corneal power in daily practice.

Cataract surgery in a patient with an angle gamma due to macular heterotopia.

PURPOSE: We report a case of cataract surgery in a patient with a detectable angle gamma due to macular heterotopia. OBSERVATION: A 48-year-old man had angle gamma due to macular heterotopia secondary to retinopathy of prematurity. The preoperative corrected distance visual acuity was 20/32 in the right eye and 20/200 in the left eye. Ocular deviation was esotropic at an angle of 70-80prism diopter. Only the right eye was capable of fixating due to the amblyopia in the left eye. The preoperative root mean square was measured (cornea: 1.32 µm, total: 1.64 µm in ordinary fixation position, cornea: 0.36 µm, total: 3.40 µm in pupil center position). The total aberration was lower in the ordinary fixation position than in the pupil center position. Corneal refractive power was 41.75 D in the ordinary fixation position and 43.05 D in the pupil center position. The axial lengths were 22.25 and 22.54 mm, respectively. We selected the VA60BBR intraocular lens (IOL) at +28.00 D based on the targeted fixation state. Target refraction was -1.32 D. The postoperative course was favorable, and the resulting visual acuity was 20/40. CONCLUSION: We report a case of cataract surgery on a patient with an angle gamma due to macular heterotopia. The postoperative course was favorable, and the patient's satisfaction was good considering that we selected the IOL's postoperative fixation state to meet the patient's occupational demands.

Association Between Ocular Dominance and Anisometropic Hyperopia.

INTRODUCTION AND PURPOSE: Anisometropia, a relative difference in the refractive state of the two eyes, is common in hyperopic patients. We investigated the association between ocular dominance (sighting dominance) and refractive asymmetry in patients with hyperopia. METHODS: This retrospective study included 223 hyperopic patients with a mean age of 10.1 ± 3.6 years (range 3 to 21 years). Refractive error was measured with cycloplegic refraction, and axial length was measured with IOLMaster® (Carl Zeiss Meditec, Dublin, CA). Ocular dominance was assessed with the hole-in-the-card test. The amount of hyperopic anisometropia was subdivided into four groups: less than 0.50 D, 0.50-0.99 D, 1.00-1.99 D, and 2.00 D or greater. RESULTS: Ocular dominance of the right and left eye was seen in 66% and 34% of the patients, respectively. The nondominant eye had higher hyperopia, astigmatism, and shorter axial length than the dominant eye (P < 0.001). In the group with spherical equivalent anisometropia of ≥0.50 D in particular, the nondominant eye was significantly more hyperopic and had shorter axial length than the dominant eye (both P < 0.001). CONCLUSIONS: The current study revealed that the nondominant eye had a greater hyperopic refractive error and shorter axial length than the dominant eye, in patients who had a high degree of anisometropia in particular.

Five-year follow-up of ocular deviation in bilaterally pseudophakic patients.

PURPOSE: To investigate long-term ocular deviation in patients who had undergone implantation of a monofocal intraocular lens (IOL) in both eyes. METHODS: Eighty-eight patients with exophoria (average age, 68 ± 8 years; average axial length, 23.9 ± 0.9 mm) scheduled for bilateral phacoemulsification and monofocal IOL implantation were recruited. Before surgery and at 1, 3, and 6 months and 1, 2, 3, 4, and 5 years after surgery, we assessed ocular deviation near stereopsis in patients wearing their normal spectacles. RESULTS: At 5 years after surgery, near stereopsis had a median value of 50 arcsec and the mean stereopsis was 85.8 ± 101.8 arcsec; 85 patients (85%) had good stereopsis (ie, ≥100 arcsec). Of the total patients, 12.5% shifted from exophoria to intermittent strabismus or exotropia at near vision, and near stereopsis decreased. Most of them had a preoperative near exophoria angle of more than 12 prism diopters. CONCLUSION: In bilaterally pseudophakic patients with a near exophoria angle of more than 12 prism diopters, we should be concerned about the possibility of variations in ocular deviation and stereopsis after cataract surgery.