Meta-analysis is a method to obtain a weighted average of results from various studies. In addition to pooling effect sizes, meta-analysis can also be used to estimate disease frequencies, such as incidence and prevalence. In this article we present methods for the meta-analysis of prevalence. We discuss the logit and double arcsine transformations to stabilise the variance. We note the special situation of multiple category prevalence, and propose solutions to the problems that arise. We describe the implementation of these methods in the MetaXL software, and present a simulation study and the example of multiple sclerosis from the Global Burden of Disease 2010 project. We conclude that the double arcsine transformation is preferred over the logit, and that the MetaXL implementation of multiple category prevalence is an improvement in the methodology of the meta-analysis of prevalence.

Meta-analysis of prevalence

We have applied research on the visual psychophysics of reading to low vision assessment. Research on different aspects of the reading process found that reading rate rather than reading comprehension is more sensitive to variations in a subject’s visual functioning or the stimulus properties of print. The research identified four different visual factors that significantly affect reading rate: (1) acuity reserve [print size relative to acuity threshold], (2) contrast reserve [print contrast relative to contrast threshold], (3) field of view [number of letters visible], and (4) in cases of maculopathy, central scotoma size. Our research indicates that fluent reading rates can be attained with a restricted field of view, as little as four characters. However, attainment of fluent reading levels requires that print size and contrast should be several times threshold and the diameter of a central scotoma should be less than 22°. Although important clinical studies are lacking, we derived specific visual requirements for different reading rates from published experimental research to provide a starting point and to illustrate how visual requirements could be derived, even with poor correlations. Research has made significant progress toward the development of a comprehensive low vision assessment that will allow the practitioner to identify visual impediments to reading, other than reduced visual acuity. Having more fully characterized a visual impairment, the practitioner may tailor devices or interventions to the individual’s needs and capabilities.

Visual requirements for reading

The only cultured cell types extensively used for tissue regeneration are the keratinocyte and the chondrocyte. Cultured autologous keratinocytes derived from the epidermis have been used for many years to produce grafts that regenerate an epidermis over a full-thickness wound, such as a third-degree burn. But there have been many failures of engraftment, and in the absence of criteria for the quality of the cultures, the causes of failure cannot be analyzed. It has become clear that the essential feature of the graft is the presence of an adequate number of stem cells. This article describes the criteria for estimating that number. Advances in graft preparation, combining better preservation of stem cells with ease of application of the graft, are also described. These improvements have been applied to cultures of ocular limbal cells, which contain the keratinocyte stem cells of the corneal epithelium. Cultures meeting the criteria of stem cell number have been grafted to 116 patients suffering from chemical destruction of the limbus. The procedure has been highly successful in the alleviation of suffering and the restoration of vision.

Regeneration of squamous epithelia from stem cells of cultured grafts. [5YIF: 3.64; Citations: 77]

In cooperation with Morcher GmbH, we developed a black-diaphragm aphakia intraocular lens (IOL) designed to correct congenital and traumatic aniridia. Since June 1991, we have implanted this IOL into five eyes with congenital aniridia combined with cataract, and into eight eyes with traumatic aniridia combined with cataract or aphakia. Positioning the IOL was rather difficult, especially in the traumatic cases with inadequate capsular support, and in combination with penetrating keratoplasty. After up to 15 months' follow up, functional results are encouraging. However, slight persistent intraocular inflammation was observed in all of the eyes, more obviously in the traumatic cases. The effect of the IOL on the corneal endothelium is still being investigated

Black-diaphragm intraocular lens for correction of aniridia

Human limbal epithelial stem cell regulation, bioengineering and function.

Author(s): Bonnet, Clemence; Miller, Kevin M | Abstract: PurposeTo assess the preliminary safety and efficacy of custom silicone artificial iris implantation.SettingStein Eye Institute.DesignProspective consecutive case series.MethodsMedical records of patients implanted with the artificial iris were reviewed and followed for 1 year. Safety measures included corrected distance visual acuity (CDVA), intraocular pressure (IOP), endothelial cell count (ECC), surgical complications, secondary interventions, and adverse events (AEs). Efficacy measures included CDVA with glare, subjective daytime and nighttime glare graded from 0 to 10 (very significant), and subjective cosmetic appearance graded from 0 to 10 (very satisfied).ResultsTwenty eyes (19 patients) were implanted. Safety data were mixed. CDVA improved in 13 eyes and worsened in 6. ECC decreased from 1918 ± 870 to 1405 ± 705 cells/mm (P = .02). Eight eyes experienced postoperative complications. There were 4 IOP elevations, 2 corneal decompensations, 1 case of cystoid macular edema, and 1 device dislocation. Four eyes underwent secondary surgical interventions including 2 AEs (1 glaucoma surgery and 1 device dislocation). Efficacy outcomes were excellent. CDVA with glare improved from 1.5 ± 0.6 to 0.7 ± 0.8 logarithm of the minimum angle of resolution (P l .01). Mean subjective daytime glare decreased from 8.9 ± 1.8 to 2.7 ± 2.6 (P l .01) and nighttime glare decreased from 7.9 ± 1.8 to 2.5 ± 2.7 (P l .01). Mean cosmesis improved from 2.2 ± 1.6 to 8.8 ± 2.1 (P l .01).ConclusionsCustom artificial iris implantation was moderately risky but very effective at reducing light and glare sensitivity and in improving ocular cosmesis.

/pdf/safety-and-efficacy-of-custom-foldable-silicone-artificial-16t9pzrlhi.pdf

Safety and efficacy of custom foldable silicone artificial iris implantation: prospective compassionate-use case series.

Purpose To describe the causes and prevalence of moderate-to-severe visual impairment (MSVI) and blindness from corneal diseases, as well as corneal transplantation across Asia. Methods A meta-analysis of the published literature to identify population-based surveys conducted from 2008 to 2019 in 22 Asian countries regarding the prevalence and causes of MSVI and blindness from corneal disease, and a review of national corneal transplant data and eye bank statistics. Results A total of 5307 records were screened to identify 57 reports that were used to estimate a prevalence of MSVI and blindness caused by corneal diseases in Asia of 0.38% (95% confidence interval, 0.29%-0.48%). The most frequent corneal diseases were infectious keratitis, trauma, and pseudophakic bullous keratopathy. As expected, these represented the most common indications for corneal transplantation, although the percentages in each country differed based on the level of economic development, with pseudophakic bullous keratopathy being the most common indication in countries with higher gross national income per capita. Despite this, endothelial keratoplasty is not the most commonly performed form of corneal transplantation in any Asian country and represents only a small percentage of keratoplasty procedures performed in most countries. Conclusions The prevalence of MSVI and blindness from corneal disease in Asia is approximately 0.4%, with a nearly 20-fold difference in the national prevalence across the region. The indications for keratoplasty, reflective of the causes of corneal dysfunction, also vary, more so according to the gross national income than to geographic location, and only a few Asian countries have rates of corneal transplantation above international means.

Clemence Bonnet

Papers

Human limbal epithelial stem cell regulation, bioengineering and function.

Safety and efficacy of custom foldable silicone artificial iris implantation: prospective compassionate-use case series.

Corneal Blindness in Asia: A Systematic Review and Meta-Analysis to Identify Challenges and Opportunities.

Limbal stem cell diseases

Long-term outcomes of Descemet membrane endothelial keratoplasty in eyes with prior glaucoma surgery