The latest medical research on Optometry

To determine whether classification of accommodative insufficiency (AI) based on the subjective push-up test is indicative of reduced amplitude measured objectively.

Monocular subjective accommodative amplitude was measured in participants 7-24 years of age with the push-up test; a 0.9 mm letter was moved towards the eye until first sustained blur occurred. Monocular objective amplitude was measured with the same target and an autorefractor for demands from 2.5 to 30 D. The maximum response was termed the amplitude. Near point of convergence (NPC) was measured in a subset of participants. Participants were classified into groups using subjective amplitude: normal amplitude or AI (amplitude < ((15 - 0.25 × age) - 2)). Objective amplitude was plotted by age for each group and one-way ANCOVA used to evaluate differences while controlling for age. For NPC measures, a t-test compared the magnitude of the break between those with and without AI.

Fifty-five of 185 participants were classified as having AI. Objective amplitude decreased with age (0.20 D/year) and there was no significant difference in the age-adjusted mean amplitudes for the two groups (AI: 7.62 D, CI = 7.19, 8.04; Normal: 7.86 D, CI = 7.58, 8.15; p = 0.11). For the subset with NPC measures, participants classified as having AI had significantly more receded break values than those without AI (7.7 ± 5 vs. 3.7 ± 3 cm, p < 0.001).

Factors other than accommodative ability may be contributing to lower subjective amplitude findings in individuals meeting the criterion for AI.

This case illustrates a clear temporal and possible causal relationship of COVID-19 infection with AMN. Further studies and data are required to justify its association, but the rising cases of AMN shall be anticipated as COVID-19 infections have become endemic worldwide.

To report a case of AMN post-COVID-19 infection.

A 24-year-old Indian woman presented with acute-onset painless bilateral central scotoma for a day. The symptom was preceded by a history of COVID-19 infection 3 weeks prior. Ocular examination revealed a near-normal visual acuity for both eyes. Fundus examination showed bilateral dull foveal reflex with mild scattered cotton wool spot and vascular tortuosity. Optical coherence tomography macula revealed a distinct short hyperreflective band involving the outer plexiform and outer nuclear layers nasal to the fovea. The Bjerrum perimetry test revealed central scotoma temporal to the fixation. Optical coherence tomography lesions and scotomas are identical and congruous in both eyes. Serial fundus photographs are captured showing the evolving changes of near-normal macula to pigmented wedge-shaped petaloid lesions around the fovea. The patient was diagnosed as bilateral AMN and treated with oral prednisolone. On subsequent follow-up, the central scotoma improved.

The ocular surface evaporatively cools exponentially during periods of blink refrainment. With a subgroup of subjects with initially stable tear films and normal lipid layer thickness, cumulative tear film stress from repeated, longer-term blink refrainment could contribute to tear evaporation and symptoms of computer vision syndrome.

This study aimed to examine the relationship between the length of the maximum achievable interblink time and the rate of ocular surface cooling under stress test conditions of repeated refrainment from blinking for as long as possible.

Subjects acclimated to the examination room for 10 minutes before measurement and then were asked to hold the eyes open and refrain from blinking for as long as possible (the maximum blink interval), while ocular surface temperature was recorded using an infrared thermographic video camera. Subjects completed 20 trials with four successive blinks separating each trial.

Fifteen subjects (8 female and 7 male subjects) completed the study. The grand mean ocular surface cooling rate was -0.027°C/s (range, -0.338 to +0.014°C/s). A faster ocular surface cooling rate was significantly related to an exponentially shorter maximum blink interval (p<0.001). An increasing number of trials was related to a clinically insignificant increase in the length of the maximum blink interval overall, and a post hoc analysis revealed subject subgroups for whom the stress test was effective or ineffective.

Vitamin E can be used as a diffusion barrier with commercially available silicone hydrogel lenses to provide sustained release of ciprofloxacin. The results suggest that vitamin E may form blockages in channels within a silicone hydrogel lens material, thereby forcing a longer path for drugs to diffuse into and out of the lens material. There is an optimal amount of vitamin E that needs to be loaded to extend the release duration, and this is lens material dependent.

This study aimed to develop a contact lens-based ocular drug delivery system using vitamin E as a diffusion barrier to extend the release duration of ciprofloxacin.

Five commercial lenses were soaked for 24 hours in various concentrations of vitamin E dissolved in ethanol (0.0125 to 0.2 g/mL). The lenses were loaded with ciprofloxacin for 24 hours in 3 mL of 3 mg/mL of ciprofloxacin/acetic acid solution. The drug release was evaluated in 3 mL of phosphate-buffered saline solution. At t = 0.5, 1, 2, 4, 6, 8, 12, 16, and 24 hours, the amount of ciprofloxacin released was measured using a UV-VIS spectrophotometer at 270 nm.

There was a decrease in ciprofloxacin loading with increasing amounts of vitamin E loaded into the silicone hydrogel lenses. For each lens type, there was an optimal amount of vitamin E loaded that extended the release duration of the drug from 1 hour (without vitamin E) to as long as 16 hours. In contrast, vitamin E loaded into hydrogel lenses had no effect on the amounts of drugs loaded or the release duration.

To evaluate the short-term (1 week after completion of treatment) effect of office-based vergence and anti-suppression therapy (OBVAT) on binocular vision and accommodative function when compared to observation alone in children with small-to-moderate angle intermittent exotropia (IXT).

In this single-masked (examiner masked), two-arm, single-centre randomised clinical trial, 40 participants, 6 to <18 years of age with untreated IXT were randomly assigned to OBVAT or observation alone. Participants assigned to therapy received 16 weeks of OBVAT (60 min per visit, once per week) with home reinforcement (15 min per day, 5 days a week). Therapy included vergence, accommodation and anti-suppression techniques. This paper reports the results of clinical measures of binocular vision and accommodation, including fusional vergence, near point of convergence, vergence facility, amplitude of accommodation, the Worth 4-dot test and the Fusion Maintenance Score (FMS).

Treatment group differences at the primary outcome visit significantly favoured the OBVAT group (n = 20) over the observation group (n = 16) in negative fusional vergence break point at both distance (p ≤ 0.001; r = 0.58) and near (adjusted mean difference: 12.3 Δ; 95% CI: 5.3-19.3 Δ; p = 0.001; partial eta squared: 0.28), positive fusional vergence break point at both distance (p = 0.009; r = 0.43) and near (adjusted mean difference: 20.6 Δ; 95% CI: 11.8-29.4 Δ; p ≤ 0.001; partial eta squared: 0.41), vergence facility (adjusted mean difference: 5.6 cpm; 95% CI: 1.9-9.4 cpm; p = 0.005; partial eta squared: 0.22) and the FMS (p = 0.007; r = 0.44).

In this randomised clinical trial of participants aged 6 to <18 years with IXT, those in the OBVAT group had a significantly better fusional vergence range, vergence facility, near Worth 4-dot test result and FMS than the observation group at the 17-week visit. The improvement in these areas further support the effectiveness of OBVAT for improving IXT.