Evaluating relaxed ciliary muscle tone in presbyopic eyes

Pharmacological Treatments for Presbyopia

Accommodation is the change in dioptric power of the eye. It is a dynamic process that allows focusing on an object at all distances. In order to focus sharply, three physiological responses, known as the triad of accommodation, are produced by a change in pupil size, a change in shape and position of the lens, and ocular convergence. This is modulated by the autonomic nervous system, mainly the parasympathetic nervous system. Presbyopia is a refractive condition that occurs with aging, usually manifesting around 40-50 years of age, and is a result of the loss of accommodation in the eye, causing loss of visual performance when focusing on objects placed at different distances, starting with near vision. Glasses, contact lenses, surgical approaches and now pharmacological treatments are accepted methods of treating presbyopia. Pharmacological treatment is a promising new noninvasive option for treating presbyopia. Currently there are three pharmacological approaches to the treatment of presbyopia. The first one aims to produce miosis and, from a pinhole effect, increase depth of focus, and therefore improve uncorrected near visual acuity (UNVA). The second one addresses rehabilitating accommodation in a binocular way, allowing good vision at all distances. Finally, the third strategy uses lipoic acid to restore the lost elasticity of the lens. All of these pharmacological treatments are topical non-invasive eyedrops, with no serious adverse effects having been reported with any of the strategies, and require the right patient selection process to fulfill expectations and needs. The aim of this article is to provide an update on recent advances in this field.

Ultrahigh field MRI determination of water diffusion rates in ex vivo human lenses of different age

BACKGROUND

The development of presbyopia is correlated with increased lens stiffness. To reveal structural changes with age, ultrahigh field magnetic resonance imaging (UHF-MRI) was used to analyze water diffusion in differently aged human lenses ex vivo.

METHODS

After enucleation lens extractions were performed. Lenses were photographed, weighed, and embedded in 0.5% agarose dissolved in culture medium. UHF-MRI was conducted to analyze anatomical characteristics of the lens using T2-weighted Turbo-RARE imaging and to obtain apparent diffusion coefficients (ADC) measurements. A Gaussian fit routine was used to examine the ADC histograms.

RESULTS

An age-dependent increase in lens wet weight, lens thickness, and lens diameter was found (P<0.001). T2-weighted images revealed a hyperintense lens cortex and a gradually negative gradient in signal intensity towards the nucleus. ADC histograms of the lens showed bimodal distributions (lower ADC values mainly located in the nucleus and higher ADC values mainly located in the cortex), which did not change significantly with age [βPeak1=1.96E-7 (-20E-7, 10E-7), P=0.804 or βPeak2=15.4E-7 (-10E-7, 40E-7), P=0.276; respectively].

CONCLUSIONS

Clinically relevant age dependent lens hardening is probably not correlated with ADC changes within the nucleus, which could be confirmed by further measurements.

Effect of Yoga-Based Ocular Exercises in Lowering of Intraocular Pressure in Glaucoma Patients: An Affirmative Proposition

Glaucoma is the most common cause of irreversible blindness worldwide, with >65 million sufferers. It is incurable and the only therapeutic approach accepted till now is the lowering of intraocular pressure (IOP) medically and/or surgically. These known interventions might have many side effects and complications. Yoga-based interventions are now well accepted as alternative therapy in many chronic diseases. The effects of yoga in glaucoma, however, have not been studied adequately. Accommodation (the process of adjustment of optical power to maintain clear vision) of eyes leads to instant lowering of IOP. Therefore, we hypothesize that one of the yoga-based interventions, Tratak kriya, which includes ocular exercises might lead to lowering of IOP in glaucoma patients. The proposed Tratak kriya leads to contraction and relaxation of ciliary muscles which might increase outflow of aqueous humor. In addition, this yoga-based intervention might decrease stress and improve quality of life in glaucoma patients.