摘要:

Four subjective measures of the refractive error of 42 eyes (21 patients) were obtained by 2 examiners, one using a Humphrey Vision Analyzer(tm) and the other using a conventional refractor. Each examiner made 2 separate measures of each subject's refractive error, one without and one with an added cylindrical lens chosen at random from a predetermined set of powers and axes. The order of using the instruments and the added lenses was mixed. Measures of the refractive errors differed with the 2 instruments by approximately the same amount on average as did duplicate measures with either instrument. Refractive-error measures obtained with the 2 instruments are about as valid as they are repeatable.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Each of 5 subjects with normal corneas was fitted with a Bausch & Lomb F3-series Soflens® contact lens and with an experimental F3-series ultrathin Soflens®. A best-fit PMMA lens was worn in combination with each of the soft lenses. In addition, a best-fit CAB lens and a tight PMMA lens were separately worn in combination with the ultrathin soft lens. Each of 3 subjects with keratoconus was fitted with an ultrathin soft lens combined with a PMMA lens. For the normal corneas, the combination that produced the least corneal edema after 5 hr was an ultrathin soft lens with either a PMMA or CAB lens of best fit. Two of the 3 keratoconic subjects were able to wear their contact lens combination for the 5-hr test period; corneal swelling was 1.7% and 5.3%. For all subjects, acuity with a combination contact lens system was better than with a soft or hard lens alone.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

A combination formed by covering a soft contact lens on the cornea with either an oxygen-permeable or an impermeable hard lens offers some advantages over a soft lens or a hard lens alone. Several procedures can be used to fit such combinations to the eye. The amount of oxygen that is delivered to the cornea will depend strongly on the fit of the soft lens to the cornea and the fit of the hard lens to the soft lens; the amount of oxygen delivered by 4 different combinations is described here. The results show that the proper choice of lenses and fit will permit an adequate supply of oxygen to reach the cornea in daily wear.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Book retinoscopy involves the observation of fundus reflex changes that are said to be related to the reading levels or interpretive levels at which persons are functioning. Recent investigations have shown that increasing the cognitive demand on a person can result in accommodative changes in his eye that increase the luminance of the fundus reflex. Since the ability of observers to distinguish such changes is not known, this experiment was designed to determine the minimum detectable increase in luminance. The experiment involved a 2-alternative forced-choice procedure in which observers were required to indicate during which of 2 designated intervals the reflex from a schematic eye became brighter. The luminance of the reflex had to increase by at least 11% before it could be detected. A reduction in the lag of accommodation and dilation of the pupil probably account for the changes observed during book retinoscopy.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

High-speed photography of eyeblinks in 4 subjects provided displacement and velocity time functions. The results from dynamic measurements made with a mechanical transducer connected physically to the upper eyelid gave estimates of the passive spring constant (Kp= 1.5 gm,/mm) and the passive viscosity (Bp= 0.09 gmr- sec/mm) of the eyelid. Noting the similarity between the reciprocal-innervation mechanisms in the eyelid and the eye-movement systems, a mathematical eyelid model was derived based on the well-known eye-movement model and using similar ideal mechanical-element representations. The model-simulation time course shows the essential characteristics of an eyeblink and suggests that the force program consists of reciprocally acting pulse forces during the downblink, and pulse-step forces during the upblink. When 1 mm of lid displacement is equated with 5 deg of eyeball rotation and when the main sequences for lid movements and for time-optimal saccadic eye movements are compared, the eyeblinks are not found to be time optimal for their various amplitudes.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Sinusoidally modulated checkerboard patterns were used to investigate the effects of check size and retinal location on the “steady-state” visual evoked response (VER) of strabismic and anisometropic amblyopes. Fourier analysis of the averaged VER suggests that the waveforms produced by these techniques are complex, and that they consist of a fundamental component plus 1 or more harmonics. In all of the subjects, the VERs elicited from the amblyopic eyes by small checks in a 3.5-deg disc were significantly smaller in amplitude than those from the nonamblyopic eyes, whereas the responses to larger checks were far more similar. Large annular targets were quite effective in eliciting VERs from the peripheries of both amblyopic and nonamblyopic eyes, and these responses were at times as large as, or larger than, those produced by the central targets. Statistically no significant differences were found between the responses of the amblyopic and the nonamblyopic eyes to the annular targets.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Luminance measurements of targets and backgrounds revealed differences for various types of perimetric instruments. A lack of uniform testing conditions for instruments of the same design was also noted. Of the instruments measured, hemispheric-projection perimeters seemed to provide the most repeatable test conditions.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

Responses were obtained from 12 subjects (24 eyes) who wore 2 types of 13.6-mm diameter Bausch & Lomb Soflens“ contact lenses-thin F3 lenses and conventional-thickness F3 lenses. These responses were also compared with those of patients who had worn thin F lenses that were 12.5 mm in diameter. Fewer patients experienced discomfort or corneal changes with the thin F3 lenses than with the conventional ones. Lens diameter was also an important factor in improving the patients' responses. Only 35% of a different sample of 23 patients who had been fitted with 12.5-mm diameter thin F lenses had been able to wear them successfully, compared with 75% of those wearing the 13.6-mm diameter thin F3 lenses, even though the mean corneal thickening caused by the smaller lenses did not differ significantly from that caused by the thin F3 lenses. Thin hydrogel lenses with diameters larger than 13.6 mm thus might produce an even better overall patient response while still causing minimal corneal edema.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

An empirical method for developing a form to describe and evaluate clinical teaching is presented. The form consists of descriptive statements that characterize teachers nominated by students and faculty as the BEST teachers and that do not characterize those nominated as the WORST teachers. Each instructor receives a profile summarizing the students' ratings of him and compares his teaching effectiveness with that of his colleagues. It is emphasized that teaching evaluations do not in themselves improve teaching but that they can inspire improvement when they are used as a framework for introducing specific new teaching behaviors to instructors during consultations with an independent person such as a psychologist.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID

摘要:

A case of spherophakia with unilateral traumatic phacometecesis is presented and the treatment of the postextraction sequelae by contact-lens therapy is described.

ISSN:0093-7002    

出版商:OVID    

年代:1977

数据来源: OVID