Impact of Pupil Diameter on Objective Refraction Determination and Predicted Visual Acuity

Sources of reduced visual acuity and spectacle treatment options for individuals with Down syndrome: Review of current literature

Individuals with Down syndrome are known to have a greater prevalence of ocular conditions such as strabismus, nystagmus, elevated refractive error, poor accommodative function, elevated higher-order optical aberrations and corneal abnormalities. Related to these conditions, individuals with Down syndrome commonly have reduced best-corrected visual acuity at both far and near viewing distances across their lifespan. This review summarises the various optical sources of visual acuity reduction in this population and describes clinical trials that have evaluated alternative spectacle prescribing strategies to minimise these optical deficits. Although refractive corrections may still have limitations in their ability to normalise visual acuity for individuals with Down syndrome, the current literature provides evidence for eye care practitioners to consider in their prescribing practices for this population to maximise visual acuity. These considerations include accounting for the presence of elevated higher-order aberrations when determining refractive corrections and considering bifocal lens prescriptions, even for young children with Down syndrome.

Mesopic pupil indices as potential risk factors for glare disability after intraocular implantable collamer lens implantation: prospective study

PURPOSE

To explore the influence of preoperative factors, including varying pupil sizes and refractive attributes, on postoperative glare disability in patients undergoing implantable collamer lens (ICL) implantation.

SETTING

Second Affiliated Hospital, Nanchang University, Nanchang, Jiangxi, China.

DESIGN

Prospective observational study.

METHODS

The preoperative ocular characteristics and 6-month postoperative glare status in eligible patients who underwent EVO-Visian ICL V4c (VICMO) implantation were analyzed. The glare disability criteria encompassed a glare symptom score >6 and glare sensitivity exceeding 1:2.7. Logistic regression analysis was used to explore the relationship between the preoperative ocular parameters and post-ICL glare.

RESULTS

The study included 95 patients (mean age, 26.04 ± 6.29 years), comprising 30 men (58 eyes) and 65 women (129 eyes). Multivariate analysis revealed a significant correlation between postoperative glare disability and increased spherical power in preoperative mesopic pupils (β = -0.124, P = .039), as well as elevated cylinder power in preoperative mesopic (β = -0.412, P = .009) and photopic pupils (β = -0.430, P = .007). Moreover, a larger preoperative mesopic pupil diameter (β = 0.561, P = .005) demonstrated a significant correlation with glare disability.

CONCLUSIONS

Preoperative mesopic pupil dimensions and associated refractive parameters, such as sphere and cylinder, were correlated with glare disability, including the cylinder aspect in photopic pupils, which can assist clinicians in optimizing preoperative selection for ICL implantation, aiding in the anticipation of potential glare disability risks.

Dioptric differences between clinically determined and metric-optimised refractions for adults with Down syndrome

PURPOSE

Refractions based on the optimisation of single-value wavefront-derived metrics may help determine appropriate corrections for individuals with Down syndrome where clinical techniques fall short. This study compared dioptric differences between refractions obtained using standard clinical techniques and two metric-optimised methods: visual Strehl ratio (VSX) and pupil fraction tessellated (PFSt), and investigated characteristics that may contribute to the differences between refraction types.

METHODS

Thirty adults with Down syndrome (age = 29 ± 10 years) participated. Three refractive corrections (VSX, PFSt and clinical) were determined and converted to vector notation (M, J0 , J45 ) to calculate the dioptric difference between pairings of each type using a mixed model repeated measures approach. Linear correlations and multivariable regression were performed to examine the relationship between dioptric differences and the following participant characteristics: higher order root mean square (RMS) for a 4 mm pupil diameter, spherical equivalent refractive error and Vineland Adaptive Behavior Scales (a measure of developmental ability).

RESULTS

The least squares mean estimates (standard error) of the dioptric differences for each pairing were as follows: VSX versus PFSt = 0.51 D (0.11); VSX versus clinical = 1.19 D (0.11) and PFSt versus clinical = 1.04 D (0.11). There was a statistically significant difference in the dioptric differences between the clinical refraction and each of the metric-optimised refractions (p < 0.001). Increased dioptric differences in refraction were correlated with increased higher order RMS (R = 0.64, p < 0.001 [VSX vs. clinical] and R = 0.47, p < 0.001 [PFSt vs. clinical]) as well as increased myopic spherical equivalent refractive error (R = 0.37, p = 0.004 [VSX vs. clinical] and R = 0.51, p < 0.001 [PFSt vs. clinical]).

CONCLUSIONS

The observed differences in refraction demonstrate that a significant portion of the refractive uncertainty is related to increased higher order aberrations and myopic refractive error. Methodology surrounding clinical techniques and metric-optimisation based on wavefront aberrometry may explain the difference in refractive endpoints.

Implementation of Kiosk-Type System Based on Gaze Tracking for Objective Visual Function Examination

To demonstrate that the near-point-of-convergence (npc) examination is performed subjectively, the visual fixation and four-prism diopter (Δ) base-out (BO) examinations can be conducted with a kiosk-type objective examination method based on gaze tracking, and can be compared with the existing method. Objective examination equipment was used to verify effectiveness. Fifteen adult men and women in their 20s and 30s (26.87 ± 3.31 years) with visual acuity of 0.8 (logMAR: 0.1, Snellen: 20/25(6/7.5)) or higher (corrected vision in the case of ametropia) underwent the npc, visual fixation, and 4 Δ BO examinations based on the existing examination method followed by the gaze-tracking-based kiosk-type examination method. Three examinations were performed, and a comparative analysis was conducted. The gaze tracking method used a method of extracting eye feature points, and it was judged that the ocular moved when the movement of 30 eye feature points at the edge of the iris was detected. In the comparison between the existing method and the kiosk-type method, there were no statistically significant differences in npc, visual fixation, and 4 Δ BO examinations. Npc examinations were performed extensively by the existing subjective method, however, it seems that these can be conducted objectively using the kiosk-type method. Visual fixation and 4 Δ BO examinations require high-examination proficiency because finely moving ocular movements need to be observed, but it is judged that examinations can be performed more easily and accurately when combined with the kiosk-type method. The symmetrical characteristics between the two test results are expected to serve as a basis for using the kiosk-type examination method in clinical practice.

Visual Acuity Outcomes in a Randomized Trial of Wavefront Metric-optimized Refractions in Adults with Down Syndrome

SIGNIFICANCE

This study reports visual acuity outcomes from a clinical trial investigating an objective refraction strategy that may provide a useful tool for practitioners needing additional strategies to identify refractive corrections for adults with intellectual disability.

PURPOSE

Determining refractions for individuals with Down syndrome is challenging because of the presence of elevated refractive error, optical aberrations, and cognitive impairment. This randomized clinical trial evaluated the performance of spectacle corrections determined using clinical techniques and objective refractions derived from wavefront aberration measures.

METHODS

Thirty adults with Down syndrome had a clinical refraction determined by a single expert examiner using pre-dilation and post-dilation techniques appropriate for this population. Objective refractions were determined from dilated wavefront aberration measures that were processed post-visit to identify refractions that optimized each of two image quality metrics: pupil fraction tessellated and visual Strehl ratio in the spatial domain. The three refractions were dispensed in random order and worn for 2 months each. The primary outcome measure, binocular visual acuity, was obtained by a masked examiner administering a distance logMAR acuity test. To compare treatment types, mean acuity was compared using a two-sided type 3 F test of the treatment effect in a linear mixed-effects regression model, where the final model included fixed effects for treatment, period (1, 2, or 3), and first-order carryover effects.

RESULTS

The 2-month estimated least square means in binocular visual acuity (logMAR) were 0.34 (95% confidence interval [CI], 0.25 to 0.39) for clinical refractions, 0.31 (95% CI, 0.25 to 0.36) for pupil fraction tesselated refractions, and 0.33 (95% CI, 0.27 to 0.38) for visual Strehl ratio refractions. No statistically significant treatment effect was observed (F = 1.10, P = .34).

CONCLUSIONS

Objective refractions derived from dilated wavefront aberration measures resulted in acuity similar to expert clinician-derived refractions, suggesting that the objective method may be a suitable alternative for patients with Down syndrome.

Visual image quality after small-incision lenticule extraction compared with that of spectacles and contact lenses

PURPOSE

To assess the influence of small-incision lenticule extraction (SMILE) for high myopia on the visual image quality assessed by the logarithm of the visual Strehl ratio (logVSX) and put this into a clinical context by pairwise comparing the logVSX of postoperative eyes with those of myopic controls wearing spectacles and/or contact lenses.

SETTING

University hospital.

DESIGN

Prospective and cross-sectional clinical study.

METHODS

Patients with a myopic spherical equivalent of at least 6.00 diopters treated with SMILE aimed at emmetropia and correspondingly myopic controls corrected with spectacles and/or contact lenses were included. The logVSX calculation was divided into habitual logVSX based on the wavefront aberration measurement directly and optimal logVSX calculated in a theoretical through-focus experiment to obtain the best-achievable logVSX.

RESULTS

A total of 117 eyes of 61 patients and 64 eyes of 34 myopic controls were included. SMILE did not affect the habitual logVSX but worsened the optimal logVSX (P < .001). The postoperative habitual logVSX was statistically significantly worse compared with contact lenses (P = .002). The postoperative optimal logVSX was significantly worse compared with both spectacles (P < .01) and contact lenses (P = .003). There was no statistically significant difference in habitual or optimal logVSX between spectacles and contact lenses.

CONCLUSIONS

SMILE for high myopia does not affect the habitual logVSX but decreases the optimal logVSX slightly. The postoperative habitual logVSX is worse than for contact lenses but not spectacles, and the postoperative optimal logVSX is worse than for both contact lenses and spectacles. There is no statistically significant difference in either habitual or optimal logVSX between spectacles and contact lenses.

A Randomized Trial of Objective Spectacle Prescriptions for Adults with Down Syndrome: Baseline Data and Methods

SIGNIFICANCE

It is difficult to determine the most efficacious refractive correction for individuals with Down syndrome using routine clinical techniques. New objective methods that optimize spectacle corrections for this population may reduce limitations on daily living by improving visual quality.

PURPOSE

This article describes the methods and baseline characteristics of study participants in a National Eye Institute-sponsored clinical trial to evaluate objectively derived spectacle corrections in adults with Down syndrome. Intersession repeatability of the primary outcome measure (distance visual acuity) is also reported.

METHODS

Adults with Down syndrome were enrolled into a nine-visit study to compare clinically derived spectacle corrections and two different objective spectacle corrections derived from wavefront aberration data. Spectacle corrections were randomized and dispensed for 2 months each. Distance visual acuity was measured with a Bailey-Lovie-style chart. Intersession repeatability of acuity was established by performing difference versus mean analysis from binocular acuity measures obtained through habitual corrections at visits 1 and 2.

RESULTS

Thirty adults (mean ± standard deviation age, 29 ± 10 years) with a large range of refractive errors were enrolled. Presenting visual acuity at visit 1 was reduced (right eye, 0.47 ± 0.20 logMAR; left eye, 0.42 ± 0.17 logMAR). The mean difference between visits 1 and 2 was 0.02 ± 0.06 logMAR, with a coefficient of repeatability (1.96 × within-subject standard deviation) of 0.12 logMAR.

CONCLUSIONS

This study seeks to investigate new strategies to determine optical corrections that may reduce commonly observed visual deficits in individuals with Down syndrome. The good intersession repeatability of acuity found in this study (six letters) indicates that, despite the presence of reduced acuity, adults with Down syndrome performed the outcome measure for this clinical trial reliably.