Segmentation and accuracy in copying and drawing: Experts and beginners

As part of an ongoing investigation into real-world copying and drawing, I recorded the eye-hand drawing strategies of 16 subjects with drawing experiences ranging from expert to novice while they copied a line drawing of a standing nude. The experts produced accurate copies whereas all the beginners produced marked inaccuracies of overall scaling, proportion and shape. Analysis of eye and hand movements showed that the experts alone segmented the original drawing into simple line sections that were copied one at a time using a direct eye-hand strategy not requiring intermediary encoding to visual memory. The results suggest that segmentation into simple lines defines the task-specific process of accurate copying, and that this process is restricted to experts, i.e. acquired through training and practice. Additional preliminary tests also suggest that a similar process may apply to drawing a model from life.     

Proximal and accommodative convergence and age

The authors have estimated the phoria for distant and near fixation in two groups of subjects (mean age 27.5 ± 4.4 and 59.2 ± 8.2 years). Different accommodative stimuli were induced by adding minus lenses for distant fixation and plus lenses for near fixation. Statistical analysis of the experimental data indicates that, for distant fixation, the value of phoria per unit of accommodative stimulus is significantly lower in presbyopic than in nonpresbyopic subjects. Also, during near fixation, the accommodative convergence (AC/A ratio) is more reliable in the presbyopic subjects when the accommodative stimulus is progressively reduced. This varying behavior indicates in presbyopic subjects that proximal convergence is of greater relative importance in the determination of the fusion-free position. In nonpresbyopic subjects, accommodative convergence is the more important component.     

Anesthesia and preoperative and postoperative medications

Although certain methods such as retrobulbar blocks are used extensively, improvements in procedure can always be implemented. The use of ultrasound, low concentrations of anesthesia, careful monitoring, and, in the case of risk patients, anesthesia standby are all important considerations to ensure uneventful treatments. Topical anesthesia eliminates needle risk as well as risk of ptosis and bruising. Because it has been demonstrated that bacteria routinely enter the anterior chamber during uncomplicated cataract surgery, certain irrigation solutions are helpful, but still debatable. Postoperatively, diclofenac, flurbiprofen, and timolol have all been proven to be effective in reducing ocular inflammation, reducing incidence of CME, and controlling pressure increase, respectively.     

Paraneoplastic and non-paraneoplastic retinopathy and optic neuropathy: Evaluation and management

Paraneoplastic syndromes involving the visual system are a heterogeneous group of disorders occurring in the setting of systemic malignancy. Timely recognition of one of these entities can facilitate early detection and treatment of an unsuspected, underlying malignancy, sometimes months before it would have otherwise presented, and gives the patient an increased chance at survival. We outline the clinical features, pathogenesis, and treatment strategies for the retinal- and optic nerve–based paraneoplastic syndromes: cancer-associated retinopathy; melanoma-associated retinopathy; paraneoplastic vitelliform maculopathy; bilateral diffuse uveal melanocytic proliferation; paraneoplastic optic neuropathy; and polyneuropathy, organomegaly, endocrinopathy, monoclonal gammopathy, and skin changes syndrome. Distinguishing these disorders from their non-paraneoplastic counterparts (e.g., autoimmune-related retinopathy and optic neuropathy, and acute zonal occult outer retinopathy) and determining appropriate systemic evaluation for the responsible tumor can be challenging. In addition, we discuss the utility and interpretation of autoantibody testing.     

Anesthesia and preoperative and postoperative medications

Retrobulbar blocks, although widely used, still have potentially serious complications. Topical anesthesia presents less risk of injury to the globe and less pain but requires careful usage and an experienced surgeon. New techniques, however, allow for an increase in the percentage of patients able to have topical anesthesia. Preoperatively, 2.5% phenylephrine is found to be just as effective as 10% phenylephrine, and, when compared with wound closure and surgeon's experience, the effect of prophylactic medications was found to be negated. Postoperatively, diclofenac is found to be as effective an anti-inflammatory agent as prednisolone. Also, the addition of 10% phenylephrine to 4% pilocarpine drops enhances the effectiveness of pharmacologic treatment of postoperative iridocorneal adhesions. In addition, ophthalmologists should be aware of emerging antibiotic resistance.     

Nodes and nodal points and lines in eyes and other optical systems

The typical stigmatic optical system has two nodal points: an incident nodal point and an emergent nodal point. A ray through the incident nodal point emerges from the system through the emergent nodal point with its direction unchanged. In the presence of astigmatism nodal points are not possible in most cases. Instead there are structures, called nodes in this paper, of which nodal points are special cases. Because of astigmatism most eyes do not have nodal points a fact with obvious implications for concepts, such as the visual axis, which are based on nodal points. In order to gain insight into the issues this paper develops a general theory of nodes which holds for optical systems in general, including eyes, and makes particular allowance for astigmatism and relative decentration of refracting elements in the system. Key concepts are the incident and emergent nodal characteristics of the optical system. They are represented by 2 × 2 matrices whose eigenstructures define the nature and longitudinal position of the nodes. If a system's nodal characteristic is a scalar matrix then the node is a nodal point. Otherwise there are several possibilities: Firstly, a node may take the form of a single nodal line. Second, a node may consist of two separated nodal lines reminiscent of the familiar interval of Sturm although the nodal lines are not necessarily orthogonal. Third, a node may have no obvious nodal line or point. In the second and third of these classes one can define mid-nodal ellipses. Astigmatic systems exist with nodal points and stigmatic systems exist with no nodal points. The nodal centre may serve as an approximation for a nodal point if the node is not a point. Examples in the Appendix , including a model eye, illustrate the several possibilities.     

Sensitivity to first- and second-order motion and form in children and adults

We compared the sensitivity of adults and children aged 3-10 years to first- and second-order motion and form. For first-order stimuli, at all ages sensitivity was better for motion than form, and motion thresholds were better at 6 Hz than at 1.5 Hz. For second-order stimuli, at all ages sensitivity was better for form than motion, and motion thresholds were better at 0.25 cyc/deg than at 1 cyc/deg. Thresholds became adult-like later for motion than for form and later for first-order than second-order stimuli. For first-order stimuli, the changes with age were larger and more protracted.     

Estrogen and progesterone receptors and human conjunctiva

Freshly frozen conjunctival tissue from premenopausal and postmenopausal women and male subjects were processed for estrogen and progesterone receptors by using monoclonal antibodies and a peroxidase-antiperoxidase technique. No immunocytochemical staining was localized in the nuclei of the cells treated with the monoclonal antibodies to human estrogen receptor or human progesterone receptor in any of the conjunctival specimens, in contrast to the strongly positive staining in breast adenocarcinoma controls. Immunocytochemical staining disclosed no evidence for estrogen or progesterone receptors on cells of the ocular surface.     

Myocilin and glaucoma: facts and ideas

Mutations in the MYOC gene that encodes for myocilin are causative for some forms of juvenile and adult-onset primary open-angle glaucoma (POAG). Myocilin is a secreted 55-57kDa glycoprotein that forms dimers and multimers. Characteristic structural motifs include a myosin-like domain, a leucine zipper region and an olfactomedin domain. Most of the mutations that have been identified in patients with POAG are localized in the olfactomedin domain, which is highly conserved among species. In the eye, myocilin is expressed in high amounts in the trabecular meshwork (TM), sclera, ciliary body and iris, and at considerable lower amounts in retina and optic nerve head. Secreted myocilin is present in the aqueous humor. In the TM, myocilin is found within the cytoplasm of TM cells and in the juxtacanalicular region in association with fibrillar extracellular matrix components. Since patients with mutations in myocilin may have high intraocular pressures, the role of myocilin for aqueous humor outflow has been investigated and conflicting results have been obtained. Recombinant myocilin increases outflow resistance in perfused anterior segment organ cultures, while overexpression of myocilin after viral gene transfer appears to reduce outflow resistance. In TM cells, the expression of myocilin is induced upon treatment with dexamethasone at a time course similar to that observed in steroid-induced glaucoma. Other factors that induce myocilin expression are transforming growth factor-beta and mechanical stretch. Promoter elements that are important for the glucocorticoid induction have not been identified, but it has been shown that upstream stimulatory factor is critical for the basal promoter activity of MYOC. Mice with a targeted disruption of the myocilin gene do not express a phenotype, indicating that the glaucomatous phenotype in humans is not because of a loss-of-function effect. Experimental studies show that mutated myocilin is not secreted, but appears to accumulate in the cells. Such an accumulation might interfere with TM function and lead to impaired outflow resistance, but, so far, experimental evidence for such a scenario is lacking. In addition, the normal function(s) of myocilin is (are) still elusive.     

睑缘炎及其相关角结膜病变

睑缘炎是眼睑缘部皮肤、皮下组织、睫毛毛囊及腺体等组织的炎性病变,为常见眼病之一,各年龄段人群均可患病,其患病率国内尚无报道。睑缘炎多累及双眼,其起病隐秘,病程具有慢性、反复发作的特点,临床容易被忽略。近年来,睑缘炎相关性     

Corneal and external disorders and refractive surgery

A review of disorders of the anterior segment of the eye may show new avenues of research as well as clinical perspectives arising from recently accumulated data. It will have to select new theoretical and clinical findings, which may most probably be apt to survive the test of time, thus providing a long-standing stimulus in science. This body of scientific work in corneal and external disorders may be divided into infectious and noninfectious entities as well as refractive and tectonic or structural problems. In this review, we will focus on the inflammatory implications of anterior segment ocular disease, and mention some evolving diagnostic features and new treatment modalities, as well as opinions on refractive surgery complicated by inflammation.     

Conjunctival and canalicular papillomas and ichthyosis vulgaris

Papillomas of the lacrimal canaliculus are very rare tumors and, when encountered in clinical practice, usually present with unilateral epiphora due to obstruction of the lacrimal drainage system. Surgical excision is usually curative although, on occasion, they may recur. The following case report concerns a patient with autosomal-dominant ichthyosis vulgaris and conjunctival and canalicular papillomas.