Perception is the ability to see, hear, or become aware of external stimuli through the senses. Visual stimuli are electromagnetic waves that interact with the eye and elicit a sensation. Sensations, indeed, imply the detection, resolution, and recognition of objects and images, and their accuracy depends on the integrity of the visual system. In clinical practice, evaluating the integrity of the visual system relies greatly on the assessment of visual acuity, that is to say on the capacity to identify a signal. Visual acuity, indeed, is of utmost importance for diagnosing and monitoring ophthalmological diseases. Visual acuity is a function that detects the presence of a stimulation (a signal) and resolves its detail(s). This is the case of a symbol like “E”: the stimulus is detected, then it is resolved as three horizontal bars and a vertical bar. In fact, within the clinical setting visual acuity is usually measured with alphanumeric symbols and is a three-step process that involves not only detection and resolution, but, due to the semantic content of letters and numbers, their recognition. Along with subjective (psychophysical) procedures, objective methods that do not require the active participation of the observer have been proposed to estimate visual acuity in non-collaborating subjects, malingerers, or toddlers. This paper aims to explain the psychophysical rationale underlying the measurement of visual acuity and revise the most common procedures used for its assessment.
Backgrounds: To assess changes in anterior segment biometry during accommodation using a swept source anterior segment optical coherence tomography (SS-OCT). Methods: One hundred-forty participants were consecutively recruited in the current study. Each participant underwent SS-OCT scanning at 0 and -3 diopter (D) accommodative stress after refractive compensation, and ocular parameters including anterior chamber depth (ACD), anterior and posterior lens curvature, lens thickness (LT) and lens diameter were recorded. Anterior segment length (ASL) was defined as ACD plus LT. Lens central point (LCP) was defined as ACD plus half of the LT. The accommodative response was calculated as changes in total optical power during accommodation. Results: Compared to non-accommodative status, ACD (2.952±0.402 vs. 2.904±0.382 mm, P<0.001), anterior (10.771±1.801 vs. 10.086±1.571 mm, P<0.001) and posterior lens curvature (5.894±0.435 vs. 5.767±0.420 mm, P<0.001), lens diameter (9.829±0.338 vs. 9.695±0.358 mm, P<0.001) and LCP (4.925±0.274 vs. 4.900±0.259 mm, P=0.010) tended to decreased and LT thickened (9.829±0.338 vs. 9.695±0.358 mm, P<0.001), while ASL (6.903±0.279 vs. 6.898±0.268 mm, P=0.568) did not change significantly during accommodation. Younger age (β=0.029, 95% CI: 0.020 to 0.038, P<0.001) and larger anterior lens curvature (β=-0.071, 95% CI: -0.138 to -0.003, P=0.040) were associated with accommodation induced greater steeping amplitude of anterior lens curvature. The optical eye power at 0 and -3 D accommodative stress was 62.486±2.284 and 63.274±2.290 D, respectively (P<0.001). Age was an independent factor of accommodative response (β=-0.027, 95% CI: -0.038 to -0.016, P<0.001). Conclusions: During -3 D accommodative stress, the anterior and posterior lens curvature steepened, followed by thickened LT, fronted LCP and shallowed ACD. The accommodative response of -3 D stimulus is age-dependent.
Background: Dyop® is a dynamic optotype with a rotating and segmented visual stimulus. It can be used for visual acuity and refractive error measurement. The objective of the study was to compare refractive errormeasurement using the Dyop® acuity and LogMAR E charts.
Methods: Fifty subjects aged 18 or above with aided visual acuity better than 6/12 were recruited. Refractive error was measured by subjective refraction methods using the Dyop® acuity chart and LogMAR E charts and the duration of measurement compared. Thibo’s notation was used to represent the refractive error obtained for analysis.
Results: There was no significant difference in terms of spherical equivalent (M) (P=0.96) or J0 (P=0.78) and J45 (P=0.51) components measured using the Dyop® acuity and LogMAR E charts. However, subjective refraction measurement was significantly faster using the Dyop® acuity chart (t=4.46, P<0.05), with an average measurement time of 419.90±91.17 versus 452.04±74.71 seconds using the LogMAR E chart.
Conclusions: Accuracy of refractive error measurement using a Dyop® chart was comparable with use of a LogMAR E chart. The dynamic optotype Dyop® could be considered as an alternative fixation target to be used in subjective refraction.
Abstract: Submacular haemorrhage (SMH) is a sight threatening complication that can occur in exudative age related macular degeneration (AMD), but has been described to occur more frequently in eyes with polypoidal choroidal vasculopathy (PCV). Left untreated, SMH carries a grave visual prognosis. Thus, expedient diagnosis and effective management of this complication is of paramount importance. The treatment strategies for SMH include (I) displacement of blood from the fovea, usually by injection of an expansile gas; (II) pharmacologic clot lysis such as with recombinant tissue plasminogen activator (rtPA); and (III) treatment of the underlying choroidal neovascularization (CNV) or PCV, such as with anti-vascular endothelial growth factor (anti-VEGF) agents. These three strategies have been employed in isolation or in combination, some concurrently and others in stages. rtPA has demonstrable effect on the liquefaction of submacular clots but there are remaining uncertainties with regards to the dose, safety and the timing of initial and repeat treatments. Potential side effects of rtPA include retinal pigment epithelial toxicity, increased risk of breakthrough vitreous haemorrhage and systemic toxicity. In cases presenting early, pneumatic displacement alone with anti-VEGF may be sufficient. Anti-VEGF monotherapy is a viable treatment option particularly in patients with thinner SMH and those who are unable to posture post pneumatic displacement.
Background and Objective: Subthreshold laser therapy has emerged as a therapeutic alternative to traditional laser photocoagulation for certain ophthalmic diseases including central serous chorioretinopathy (CSCR), diabetic macular edema (DME), macular edema secondary to branch retinal vein occlusion (BRVO), and age-related macular degeneration (AMD). The objective of this paper is to review and discuss the clinical applications of subthreshold laser and the mechanisms of different subthreshold laser techniques including subthreshold micropulse laser (SMPL), selective retina therapy (SRT), subthreshold nanosecond laser (SNL), endpoint management (EpM), and transpupillary thermotherapy (TTT).
Methods: A narrative review of English literature and publicly available information published before November 2021 from literature databases and computerized texts. We discuss the currently available subthreshold laser systems and the advancements made to perform different subthreshold laser techniques for various ophthalmic diseases. We highlight various clinical studies and therapeutic techniques that have been conducted to further understand the effectiveness of subthreshold laser in the clinical setting. We conclude the article by covering emerging subthreshold laser systems that are currently being developed for future clinical use. The PubMed database was utilized for peer-reviewed articles and pertinent information on subthreshold systems was cited from publicly available online websites covering specific systems.
Key Content and Findings: Various subthreshold laser systems have been developed to treat certain retinal diseases. Several systems are currently in development for future clinical applications.
Conclusions: While conventional laser photocoagulation has been effective in treating various retinal diseases, subthreshold laser systems aim to provide a therapeutic effect without visible signs of damage to the underlying tissue. This technology may be particularly effective in treating macular disorders. Further clinical studies are needed to evaluate their role in the management of retinal diseases.
Background: Bacillary layer detachment (BALAD) is a phenomenon characterized by fluid accumulation at the myoid region of the inner photoreceptor segments identifiable on optical coherence tomography (OCT) imaging. This finding has been recently described in patients with diverse primary diagnoses which share the common feature of serous exudation in the posterior pole. However, thus far there have been very few reports in the literature of BALAD in patients with posterior scleritis.
Case Description: A 16-year-old male presented with unilateral vision changes that acutely worsened overnight to significant unilateral vision loss. He was eventually diagnosed with idiopathic posterior scleritis with associated BALAD on OCT. Similar to other reported cases of BALAD, he experienced anatomic restoration of the outer retina followed by good visual recovery after treatment with high dose steroid, ultimately with complete recovery of both retinal anatomy and vision within 4 months.
Conclusions: This case provides further evidence that posterior scleritis can be a cause of BALAD. The rapid presentation and excellent visual and anatomical outcome of this case is entirely consistent with known descriptions of BALAD in a variety of other conditions, further supporting the categorization of BALAD as an entity which retinal specialists should be able to recognize as distinct from other forms of intraretinal fluid, retinal detachment, and retinoschisis.
Background and Objective: Subthreshold laser technologies and their applications in ophthalmology have greatly expanded in the past few decades. Initially used for retinal diseases such as central serous chorioretinopathy and diabetic macular edema, subthreshold lasers have recently shown efficacy in the treatment of various types of glaucoma. Our primary objectives are to review the clinical applications of subthreshold laser in the context of glaucoma treatment and discuss the mechanisms of different subthreshold laser techniques, including subthreshold selective laser trabeculoplasty (SSLT), micropulse laser trabeculoplasty (MLT), pattern-scanning laser trabeculoplasty (PSLT), titanium laser trabeculoplasty (TLT), and micropulse transscleral cyclophotocoagulation (MP-TSCPC).
Methods: This was a narrative review compiled from literature of PubMed and Google Scholar. The review was performed from March 2021 to October 2021 and included publications in English. We also included information from web pages to cover details of relevant laser systems. We discuss the history of subthreshold laser, recent advancements in subthreshold techniques, and commercially available systems that provide subthreshold capabilities for glaucoma. We highlight basic science and clinical studies that deepen the understanding of treatment mechanisms and treatment effectiveness in the clinical setting respectively. We review commonly used parameters for each technique and provide comparisons to conventional treatments.
Key Content and Findings: We found five distinct types of subthreshold laser used in the management of glaucoma. Numerous subthreshold laser systems are commercially available and can provide this treatment. Therefore, understanding the differences between subthreshold techniques and laser systems will be critical in utilizing subthreshold laser in the clinical setting.
Conclusions: Traditional laser trabeculoplasty (LT) and cyclophotocoagulation (CPC) have shown effectiveness in the treatment of various types of glaucoma but are associated with visible damage to the underlying tissue and adverse effects. Subthreshold laser systems aim to provide the therapeutic effect found in traditional lasers, while minimizing unwanted treatment related effects. Further clinical studies are needed to evaluate the role of subthreshold lasers in the management of glaucoma.
Background: Surgically induced astigmatism (SIA) and corneal high-order aberrations (HOAs) are the two main causes of poor visual quality after cataract surgery. Changes in the parameters of corneal HOAs after cataract surgery and their effects on and relationships with changes in corneal curvature have not yet been reported. This study aimed to explore changes in anterior, posterior and total corneal curvature, astigmatism and HOAs after microincision cataract surgery.
Methods: Sixty-one age-related cataract patients (61 eyes) were included in this prospective study. The total, anterior and posterior corneal astigmatism and corneal HOAs were analyzed by anterior segment optical coherence tomography (AS-OCT) and iTrace before, one day, one week and three months after 2.2 mm temporal microincision coaxial phacoemulsification to evaluate the changes in anterior, posterior and total corneal curvature, astigmatism and corneal HOAs.
Results: The mean J0 and J45 values of anterior, posterior and total corneal curvature obtained by AS-OCT showed no statistically significant difference between preoperatively and any postoperative follow-up. SIA occurred on the anterior, posterior and total corneal surfaces and showed no statistically significant difference at any postoperative follow-up. No significant changes in 3rd-order oblique trefoil, vertical coma or 4th-order spherical aberrations were observed after surgery except for a significant increase in horizontal coma at postoperative day 1 (POD1).
Conclusions: There were no significant changes in corneal curvature after 2.2 mm temporal microincision coaxial phacoemulsification, and the corneal HOAs were not changed significantly except for the increase in horizontal coma at POD1, which may be one of the main reasons of poor visual quality at POD1 in some cataract patients who have good uncorrected or corrected distance vision.
