Traumatic cycloplegia and myopic anisometropia

The pathogenesis of myopia and the mechanism of atropine in preventing myopic progression have long been widely discussed. Recent studies with animals have pointed to the possible role of the muscarinic receptor of the retina itself in regulating eye growth. This paper stresses that, for myopia in humans, the importance of accommodation still holds. Twenty-five recovered cases of previous traumatic hyphema, occurring under age 16, were collected. For four or more years, the patients were examined for ocular refraction, axial length, intraocular pressure, gonioscopy and accommodation time; the latter was measured with an accommodo-polyrecorder. Data from injured eyes and fellow eyes were compared and analyzed. The results indicated that, in the injured eyes the refractive status was invariably less myopic than in the fellow eye, and was not related to intraocular pressure. In injured eyes the accommodation time was highly correlated with the extent of angle recess. And the difference of anisometropia was also related to the extent of angle recess. These observations showed that there was a significant correlation between the degree of myopic anisometropia and the impairment of accommodation.

The course of myopia in children with mild retinopathy of prematurity

The courses of spherical equivalent in patients (n = 62) who had mild, non-cicatricial retinopathy of prematurity (ROP), and in those without a history of ROP (n = 25) were modeled as a linear function of age; an exponential model was also considered. A few (n = 5) without ROP have abnormal courses characterized by hyperopia in early infancy; none have poor acuity. Although the majority of patients with ROP have courses indistinguishable from those of term born controls, 27 (43.5%) have abnormal courses, most of which are toward myopia. Optotype acuities were significantly poorer among the ROP patients with abnormal than normal refractive courses. Thus abnormal refractive development and acuity deficits are associated in eyes that have had mild ROP.

Rod cell activity in retinal degenerative rats

The Royal College of Surgeons (RCS) rat is a good model for the study of the early onset of retinal degenerative disorders. RCS retinal disease is often associated with the loss of rhodopsin in outer segment membranes and the progressive degeneration of photoreceptor cells. This study was conducted to investigate the possible mechanisms of the loss of photoreceptor sensitivity. The electroretinographic responses were recorded in RCS and control rats, age 15, 25 and 35 days, as well as in adult control rats. The a-waves were analyzed using the Hood and Birch model of activation of photoresponse. Photoresponse latency in the RCS rats was prolonged as the disease progressed. The maximum recorded a-wave amplitudes were significantly lower for the RCS rats compared to the control rats. The sensitivity of a-waves as indicated by Ka, the semi-saturation constant, varied and depended on the age of the rats and degenerative stage of the disease. The model's time to peak response increased more than twofold as the degeneration advanced. The changes in a-waves indicate that RCS disease causes progressive impairment of the rod photoresponse. It also suggests that in addition to the phagocytic defect of the retinal pigment epithelium, the abnormal composition of the membrane lipids and the interphotoreceptor matrix and the rhodopsin loss may also cause abnormal photoresponses in RCS rats.

Potential acuity meter for predicting visual acuity after Nd:YAG posterior capsulotomy

The potential acuity meter (PAM) was designed to evaluate visual acuity in 22 eyes that required secondary capsulotomies. The PAM prediction was within one line in 13 eyes (59%) and within two lines in 17 eyes (77%) and had an 18% rate of falsely bad prediction (more than two lines) and 5% rate of falsely good prediction for YAG capsulotomy. In aphakic patients, however, further study is necessary.