The automatic occluder, a new concept.

An electro-mechanical occluder is described for use in treating problems of binocular vision. A number of methods of achieving the automatic occluder goal are reviewed. Early results of clinical studies now in progress indicate that the "autocluder" has unique clinical usefulness.     

Perceived visual direction near an occluder

When an opaque object occludes a more distant object, the two eyes often see different parts of the distant object. Hering's laws of visual direction make an interesting prediction for this situation: the part seen by both eyes should be seen in a different direction than the part seen by one eye. We examined whether this prediction holds by asking observers to align a vertical monocular line segment with a nearby vertical binocular segment. We found it necessary to correct the alignment data for vergence errors, which were measured in a control experiment, and for monocular spatial distortions, which were also measured in a control experiment. Settings were reasonably consistent with Hering's laws when the monocular and binocular targets were separated by 30 arcmin or more. Observers aligned the targets as if they were viewing them from one eye only when they were separated by 2 arcmin; this behavior is consistent with an observation reported by Erkelens and colleagues. The same behavior was observed when the segments were horizontal and when no visible occluder was present. Perceived visual direction when the two eyes see different parts of a distant target is assigned in a fashion that minimizes, but does not eliminate, distortions of the shape of the occluded object.     

Optimal occluder luminance for seeing stationary visual phantoms

If the central portion of a vertical grating is covered up by an opaque horizontal occluder, a phantom grating is perceived to continue across the occluded region. The phantoms can be seen even if the inducing grating is stationary, but are not seen when the occluder luminance is near to the space-average luminance of the grating. Optimal occluder luminance for the perception of phantoms was measured, while occluder height and the inducing grating contrast varied. Phantom visibility was maximal when the occluder luminance was near to either the minimum or to the maximum luminance of the grating. When the occluder luminance was set between the two levels, opposite-phase illusory gratings were dominantly observed. The reciprocal relationship between the visual phantoms and the grating induction effect of McCourt (1982) is discussed.     

Effect of a pupillary light occluder on cystoid macular edema

A prospective, randomized study of 291 patients was performed to determine the effect of a pupillary light occluder on the incidence of angiographic cystoid macular edema (CME) in patients having extracapsular surgery with implantation of a posterior chamber lens. Patients were randomized preoperatively into two groups: those having surgery with and without a pupillary light occluder on the cornea. The occluder was placed on the cornea during suture placement, following the extracapsular lens extraction and intraocular lens implantation. Of the 291 patients, 198 had angiograms readable for the presence or absence of CME. The incidence of angiographic CME in patients with the occluder was 15.0%; in those without the occluder it was 12.5%. The difference was not statistically significant. The presence or absence of an occluder on the cornea during suture placement does not affect the incidence of angiographic CME or the visual results of these cases.     

永久性泪点塞植入术治疗眼干燥症

目的探讨泪点塞植入治疗眼干燥症的疗效。方法眼干燥症21例(42眼)。采用美国奥德赛永久性泪点塞(以下简称泪点塞)植入下泪点,滴人工泪液(0.1%爱丽滴眼液)每天1~2次,并逐渐减少直至停用人工泪液。结果21例(42眼)经泪点塞植入的方法治疗,结果如下:(1)Schirmer试验Ⅰ:治疗前为:(1.64±2.35)mm,治疗后为:(4.76±3.79)mm。(2)泪膜破裂时间治疗前为:(3.71±1.09)s,治疗后为:(7.43±2.74)s。(3)患者主觉症状明显改善,其中完全消失18例(36眼)、好转3例(6眼)。所有患者的滴药次数由原来的4~8次,逐渐减至为0~1次。随诊3~12月。结论泪点塞植入治疗眼干燥症是一种简单易行而效果可靠的方法。     

A new keratometer

A keratometer design is described which uses Drysdale's method for determining the radius of a curved surface with the use of a spherocylindrical lens system to allow simultaneous observation of the surface and center of curvature images. This not only results in a simple compact keratometer but also provides an instrument that can be used to measure the radius of curvature of the peripheral cornea.