Role of microperimetry in evaluating disease progression in age-related macular degeneration: a scoping review

Purpose Recent research has found variable evidence on the role of mesopic and dark-adapted scotopic microperimetry assessment in age-related macular degeneration. This scoping review summarises how mesopic and scotopic microperimetry can be used to assess disease progression in age-related macular degeneration and identifies gaps in the literature. Methods A population, concept, and context approach was used to develop the search strategy. Ovid MEDLINE, EMBASE, Cochrane Library, PubMed, CINAHL Plus, Web of Science, and SCOPUS databases were used to conduct the literature search. The key search terms used in the databases were age-related macular degeneration and microperimetry. Results Twelve studies were eligible and included in the review. All the studies (n = 12) were conducted in European countries [Germany (9), Italy (2), and the United Kingdom (1)]. The mesopic and scotopic sensitivities were measured using the Nidek scotopic microperimeter (MP1-S) (n = 6), scotopic Macular Integrity Assessment device (S-MAIA) (n = 5), and both MP1-s and S MAIA (n = 1). 83.3% (n = 10) studied (cross-sectional design) on mesopic, scotopic microperimetry and found reduced rod (scotopic) photoreceptors sensitivities compared to cone (mesopic) photoreceptors sensitivities in patients with small and reticular pseudodrusen despite having good visual acuity. Only 16.7% (n = 2) of studies followed participants with reticular drusen/large drusen for three years (longitudinal design) and found reduced scotopic over mesopic sensitivity at baseline and localized mesopic with profound scotopic sensitivity loss during follow-ups. Conclusion Scotopic sensitivity is a better functional indicator than mesopic sensitivity to understand early and intermediate age-related macular degeneration progression. The evidence from longitudinal studies is debatable due to the limited stimuli range of existing microperimeters, smaller sample size, and lost follow-ups.

Prevalence of Scotopic Sensitivity Syndrome among Arab Students with and without Learning Disabilities

Scotopic Sensitivity Syndrome (SSS) is neurologically caused by a dysfunction of magnocellular and parvocellular cells in the Lateral Geniculate Nucleus (LGN) of the thalamus. The SSS negatively affects the speed and movement of visual stimuli especially those related to academic skills. Because of the comorbidity of the SSS and learning disabilities (LDs), erroneous diagnoses may be made in differentiating between them, and this led the international scholars and researchers to focus on differential diagnosis. In the Arab context, it is essential to find an Arab indicator of the prevalence of the SSS among students with and without LDs. This research aims at determining the prevalence of the SSS among Arab students with and without LDs, as well as to identify the SSS prevalence in dyslexic students. A total of 1657 participants visited Irlen’s clinics in the Arab states. The participants' data are obtained from 6 of these clinics. The results indicated that the general prevalence rates of SSS are 31% among students without LDs, 45% among students with LDs, and 55% among dyslexic students. These rates are in favor of male students.

Irlen syndrome: systematic review and level of evidence analysis

ABSTRACT Background: Scotopic sensitivity syndrome, later called Meares-Irlen syndrome or simply Irlen syndrome (IS) has been described as symptoms of poor reading ability due to poor color matching and distorted graphic images. Individuals with this syndrome are considered slow, ineffective readers with low comprehension and visual fatigue. It is still uncertain whether the disease pathophysiology is an independent entity or part of the dyslexia spectrum. Nevertheless, treatments with lenses and colored filters have been proposed to alleviate the effect of the luminous contrast and improve patients’ reading performance. However, no evidence of treatment effectiveness has been achieved. Objective: The aim of the present study was to obtain evidence about IS etiology, diagnosis and intervention efficacy. Methods: A systematic review was performed covering the available studies on IS, assessing the available data according to their level of evidence, focusing on diagnostic tools, proposed interventions and related outcomes. Results: The data showed high heterogeneity among studies, and lack of evidence on the existence of IS and treatment effectiveness. Conclusion: The syndrome as described, as well as its treatments, require further strong evidence.

Electroretinographic assessment of retinal function at high altitude

Although hypoxia plays a key role in the pathophysiology of many common and well studied retinal diseases, little is known about the effects of high-altitude hypoxia on retinal function. The aim of the present study was to assess retinal function during exposure to high-altitude hypoxia using electroretinography (ERG). This work is related to the Tübingen High Altitude Ophthalmology (THAO) study. Electroretinography was performed in 14 subjects in Tübingen, Germany (341 m) and at high altitude at La Capanna Regina Margherita, Italy (4,559 m) using an extended protocol to assess functional integrity of various retinal layers. To place findings in the context of acute mountain sickness, correlations between ERG measurements and oxygen saturation, heart rate, and scores of acute mountain sickness (AMS) were calculated. At high altitude, the maximum response of the scotopic sensitivity function, the implicit times of the a- and b-wave of the combined rod-cone responses, and the implicit times of the photopic negative responses (PhNR) were significantly altered. A-wave slopes and i-waves were significantly decreased at high altitude. The strongest correlation was found for PhNR and O2 saturation ( r = 0.68; P < 0.05). Of all tested correlations, only the photopic b-wave implicit time (10 cd·s/m2) was significantly correlated with severity of AMS ( r = 0.57; P < 0.05). ERG data show that retinal function of inner, outer, and ganglion cell layer is altered at high-altitude hypoxia. Interestingly, the most affected ERG parameters are related to combined rod-cone responses, which indicate that phototransduction and visual processing, especially under conditions of rod-cone interaction, are primarily affected at high altitude.