Francisco Lara

General binocular disorders: prevalence in a clinic population

The purpose of this paper was to study the prevalence of nonstrabismic accommodative and binocular dysfunctions in a clinical population. We examined 265 symptomatic patients who were chosen from an optometric clinic. We performed several tests to diagnose any form of refractive, accommodative or binocular dysfunction. Of the 265 subjects examined, 59 patients (22.3%) had some form of accommodative or binocular dysfunction and required not just the correction of the refractive error but a specific treatment for each of the problems diagnosed. The remaining subjects were classed as having refractive anomalies. The frequency of binocular dysfunctions was 12.9%, and 9.4% for accommodative anomalies. Convergence excess (4.5%) was more prevalent than convergence insufficiency (0.8%) and accommodative excess (6.4%) more prevalent than accommodative insufficiency (3%).

Accommodation-Related Changes in Monochromatic Aberrations of the Human Eye as a Function of Age

PURPOSE To investigate the relationship between accommodation and the optical aberrations of the whole human eye, as a function of age. METHODS Sixty healthy subjects with spherical ametropia in the range +/-3 D, astigmatism less than 1 D, corrected visual acuity of 20/18 or better, and normal findings in an ophthalmic examination were enrolled. Subjects were divided into four groups, with age ranges of 19 to 29, 30 to 39, 40 to 49, and 50 to 60 years. Monochromatic optical aberrations and pupil size were measured with a Hartmann-Shack wavefront sensor under monocular viewing conditions, without pharmacological dilation or cycloplegia. Stimulus vergences were in the range of 0 to 5 D, with an increment of 0.5 D. The change in aberration during accommodation for different groups and different pupil conditions (natural and fixed 4-mm pupil) was compared. RESULTS Fourth-order spherical aberration (SA) became more negative with accommodation, and the rate of this change was greater in older individuals. For natural pupil conditions, there were no significant differences between age groups in the changes of the higher-order aberrations, coma, and trefoil with accommodation. However, for a 4-mm pupil, the youngest and oldest group showed significant differences in higher order RMS (root mean square) and spherical aberration compared with the other groups. High-order RMS showed a lower increase during accommodation when the pupil accommodative miosis was taken into account (natural pupil condition) than when a fixed 4-mm pupil was used. CONCLUSIONS Aberrations change with accommodation and with age. SA changes more with accommodation do than other higher-order aberrations. SA becomes more negative with accommodation, and this change is larger in older individuals. Accommodative miosis is useful for ameliorating the increase in higher-order aberrations with accommodation.

Diagnostic Signs of Accommodative Insufficiency

Purpose. To determine which are the most sensitive tests, together with accommodative amplitude, to classify accommodative insufficiency (AI), we analyzed the relation between monocular estimated method (MEM) dynamic retinoscopy, monocular and binocular accommodative facility (MAF, BAF), and positive relative accommodation (PRA) with or without the presence of reduced amplitude of accommodation. Methods. We studied 328 symptomatic patients who presented consecutively to an optometric clinic. From this sample, we selected the 41 patients who presented amplitude of accommodation at least 2 D below the minimum age-appropriate amplitude according to Hofstetter’s formula: 15 − 0.25 × age. We also selected data from 40 consecutive subjects (control group) with no general binocular disorders and normal accommodative amplitudes. We studied the specificity and sensitivity of the four signs related with the accommodative insufficiency: high MEM dynamic retinoscopy, failing MAF and BAF with minus lenses of ±2 D flipper lenses, and low PRA. Results. Using the standard deviation as the cutoff, the specificity values were MEM = 0.88, MAF = 1, BAF = 0.93, and PRA = 1. When using the mean value as the cutoff, the specificity diminished, fundamentally for MEM. The sensitivity for the 41 patients using standard deviation as the cutoff was MEM = 0.44, MAF = 0.34, BAF = 0.27, and PRA = 0.27, and when using the mean value as the cutoff the four, sensitivity values increased. Conclusions. According to the sensitivity results, with both cutoffs used, failing the ±2 D MAF test seems to be the sign that is most associated with the accommodative insufficiency.

Evaluating relative accommodations in general binocular dysfunctions

Purpose. To examine the relationship between relative accommodation and general binocular disorders and to establish their importance in the diagnosis of these anomalies. Methods. We analyzed data of negative relative accommodation (NRA) and positive relative accommodation (PRA) in 69 patients with nonstrabismic binocular anomalies. Results. Statistical analysis showed that low values of NRA and PRA were not associated with any particular disorder. High values of PRA (≥3.50 D) were related to the disorders associated with accommodative excess, whereas high values of NRA (≥2.50 D) were not related to accommodative excess. Statistical differences suggested that a high value of PRA could distinguish between anomalies. Sensitivity analysis revealed that high PRA was the most sensitive sign in patients with convergence insufficiency combined with accommodative excess (0.89) and one of the most sensitive signs for subjects with accommodative excess (0.72) and for those with convergence excess combined with accommodative excess (0.70). Conclusions. Anomalous results of NRA were not clearly associated with any dysfunction. High values of PRA were related to disorders associated with accommodative excess, so the sign of a high value of PRA should be considered as one of the diagnostic signs of these anomalies.

Changes in the objective amplitude of accommodation with pupil size.

Purpose We evaluate the effect of pupil size on objectively measured amplitude of accommodation (AA). Methods Pupil diameter and wavefront aberrometry were obtained in 15 eyes when stimulus swept across the range of clear vision in steps of 0.5 diopters. Wavefront refraction techniques were used to compute objective AA as the maximum refractive change. Measurements were obtained monocularly under low and high ambient room lighting conditions with a fixed luminance of the fixation target. Amplitude of accommodation computations were performed taking into account just paraxial rays (paraxial AA) or including the effects of the change of spherical aberration during accommodation (minRMS AA). Results Mean pupil size values at low light level were 6.26 mm (relaxed) and 4.15 mm (maximum accommodation), whereas at the high light level, those values became 4.74 and 3.04 mm, respectively. The effects of both light level on accommodation were significant (p < 0.001), and accommodative miosis was slightly larger at low light levels. Mean minRMS and paraxial AA were always greater by more than 1 diopter in high than in low ambient lighting conditions (p < 0.01), indicating a significant impact of pupil size on AA. Conclusions The influence of the ambient lighting on the objective AA is not only attributed to the increased effects of spherical aberration as the pupil dilates but mostly attributed to a decrease in the paraxial accommodation as pupil dilates.

Changes of the eye optics after iris constriction

Purpose To evaluate the possible change in the optics of the human eye after iris constriction.