Intraocular muscle function in pseudoexfoliation syndrome

Pseudoexfoliation (PE) material has been studied pathologically. However, there are no reports about intraocular muscle function in pseudoexfoliation syndrome (PXS). We studied intraocular muscle function in 12 patients (70.3 +/- 10.1 years of age) with ipsilateral PE material by measuring the time course of pupillary diameter change and accommodogram. Initial intraocular pressure (16.3 +/- 4.2 mmHg) was significantly higher in eyes with PXS than in normal fellow eyes (13.1 +/- 3.5 mmHg). The pupillary diameter of an affected eye was smaller than that of a fellow eye after bilateral topical application of tropicamide. Continuous near-point testing revealed no significant difference; accommodative contractile time, relaxation time, and/or accommodopattern showed different patterns from the fellow eye. The results suggest that intraocular muscle function is disturbed in PXS.

In vivo functional implications of isoproterenol-mediated relaxation of isolated human iris sphincter

The isolated human iris sphincter contracted with carbachol produced relaxation with an average ED50 of 1.30 x 10(-7) M for (-)-isoproterenol. The effect is sensitive to block by (-)-timolol with KB 3 x 10(-9) M. The magnitude of the average relaxation mediated by the beta-adrenoceptor agonist was only 31%. Lowering of the temperature did not potentiate the effect of (-)-isoproterenol to a significant extent. Thus, in contrast to bovine iris sphincter, where the beta-adrenoceptor mediated response of (-)-isoproterenol produces a maximum relaxation or complete mydriasis, the maximum beta-adrenoceptor mediated mydriasis of human iris may not be more than 1/3 of the maximum pupillary dilatation achieved by physiologic or pharmacologic procedures.

Possible significance of cilioretinal arteries in low-tension glaucoma

Cilioretinal arteries arise from the short posterior ciliary artery circulation or directly from the choroidal circulation. The presence of a cilioretinal artery may in compromised discs steal flow from the peripapillary circulation and account for worsening glaucoma damage. We reviewed the records of 33 patients with unilateral cilioretinal arteries admitted for investigation of low-tension glaucoma. We looked for absolute difference between the affected and unaffected eyes as well as percent difference relative to the mean value for the two eyes and to the value for the unaffected eye in the following variables: mean defect, corrected loss variance or corrected pattern standard deviation, and adjusted neuroretinal rim area. No statistically significant differences were found. The mean disc area for the eyes with cilioretinal arteries was significantly larger than that previously reported for normal eyes. The results suggest that if vascular steal exists because of the presence of this artery, it is not of major clinical importance.

Adaptive disorders of accommodation and vergence in binocular dysfunction

Disturbances of binocular vision are described clinically by the Duane-White classification in terms of the magnitude of the accommodative-convergence ratio (AC/A). Convergence excess and convergence insufficiency are assumed to result from high and low AC/A ratios respectively. It is assumed that the abnormal AC/A ratio is an independent variable that underlies abnormal phorias. However, recent studies have demonstrated that the AC/A ratio is inversely related to the adaptability of tonic accommodation (lens adaptation) and directly related to adaptability of tonic vergence (prism adaptation). We have tested whether clinical categories of convergence excess and convergence insufficiency are associated with insufficient and excessive adaptation of tonic accommodation and tonic vergence. Results demonstrate greater amplitude and duration of accommodative after-effects (lens adaptation) in the convergence insufficiency than the convergence excess group. Vergence after-effects (prism adaptation) had the reverse trend for the two groups. These results indicate that adaptive disorders of accommodation and vergence may underlie binocular disorders in symptomatic patients categorized as convergence excess and convergence insufficiency.

A longitudinal study of the changes in the static accommodation response

The results are described of a 10-year study of the longitudinal changes in the static response of an individual subject during the approach to absolute presbyopia. The amplitude of accommodation declines linearly with age. A new finding is that the magnitude of the slope of the linear portion of the response/stimulus curve also reduces with age, as does the level of tonic accommodation.

Transdermal scopolamine cycloplegia in juvenile diabetes

We report a case of transdermal scopolamine-induced cycloplegia in a 15-year-old diabetic girl. Transdermal scopolamine disks are widely used and neurologists should be ready to discern their possible side-effects.

The effect of transscleral laser cyclophotocoagulation on rabbit ciliary body vascularization

Long-term changes in the vascular network of rabbit ciliary processes induced by Nd:YAG laser cyclophotocoagulation were examined both from a morphological viewpoint and with respect to three-dimensional organization (in vascular casts). Relative changes in intraocular pressure (IOP), monitored within eyes irradiated across one-quarter, one-half, three-quarters, or all of the ciliary body circumference, are discussed in relation to morphological changes. The clinical implications of these findings are considered.

The mechanics of accommodation in relation to presbyopia

The cause of presbyopia is closely related to the force of contraction of the ciliary muscle and the resistance to deformation of the crystalline lens. Two views are currently in conflict. The view of Donders (1864) that presbyopia is caused by a decrease in the force of contraction of the ciliary muscle with age, and the opposing view of Helmholtz (1855) that the lens becomes more difficult to deform with age due to lenticular sclerosis. The present paper shows that, in fact, the ciliary muscle undergoes a compensatory hypertrophy as accommodative amplitude decreases with age. The force of contraction is about 50% greater at the onset of presbyopia than in youth. However, because of increased lenticular resistance its effect on the amplitude of accommodation is small. It is shown that the reason the lens becomes more difficult to deform is not because of lenticular sclerosis, since the lens substance does not lose water. The increased difficulty of deformation is because the capsule loses its elastic force with age and the lens fibres, particularly in the nucleus, become more compacted.

Uveoscleral outflow using different-sized fluorescent tracers in normal and inflamed eyes

Sodium fluorescein and fluorescinated dextrans (FD) of selected molecular weights were combined and perfused into the anterior chamber of normal and inflamed eyes of cynomolgus monkeys. The eyes were dissected into iris, anterior and posterior uvea, anterior and posterior sclera, retina and intraocular fluids (excluding aqueous). Each tissue was homogenized and centrifuged and the supernatant was run through a gel-filtration column to separate the fluorescent tracers. Each of the resultant peaks was quantitated and facility of uveoscleral outflow was determined. In control eyes the calculated facility of uveoscleral outflow was very similar with all tracers (from 0.047-to 0.052 microliter min-1 mmHg-1) and each tracer was found in highest concentration in the anterior sclera and anterior uvea. In inflamed eyes the calculated facility of uveoscleral outflow increased two- to five-fold with each tracer (0.12-; 0.17-; 0.29-; and 0.24 microliter min-1 mmHg-1 with fluorescein, and the fluorescinated dextrans of MWs 4000, 40,000 and 150,000, respectively). Each tracer was found in the anterior sclera and uvea in inflamed eyes whereas the posterior sclera and uvea contained predominantly the higher molecular-weight tracers (MWs 40,000 and 150,000). It is concluded that iridocyclitis causes an increase in uveoscleral outflow by increasing the permeability of the anterior uvea to all tracers and fluid. Small tracers may then diffuse into uveal blood vessels or across the sclera, yielding lower values for uveoscleral outflow. Of the four tracers studied, the optimal tracer size for studying uveoscleral outflow in either normal or inflamed eyes is MW 40,000.

Presbyopia: an animal model and experimental approaches for the study of the mechanism of accommodation and ocular ageing

During the last hundred years, observations on normal and a few aniridic human eyes, together with population studies on the age-dependent decline in accommodative amplitude, resulted in the formulation of theories of human accommodation, and led to the concept that presbyopia is an inevitable consequence of ageing. However, such studies failed to substantiate these theories and concepts or to reveal the fundamental mechanisms of accommodation and its age-dependent loss. Detailed understanding of these mechanisms and the environmental, dietary, and behavioural factors that may influence the development of presbyopia will require controlled studies and, in some cases, invasive experimental manipulations that can only be achieved through the use of an animal model. This paper reviews some of the evidence indicating that the rhesus monkey is a highly suitable primary animal model for such studies, as well as for studies on other aspects of ocular ageing, and reviews some of the techniques and experimental approaches that have already been adapted or developed for such studies.

Review of ciliary muscle effort in presbyopia

Fincham's theory of presbyopia would require maximum ciliary muscle contraction to produce maximum accommodative response at all ages. The Hess-Gullstrand theory, however, would allow a maximum accommodative response with a decreasing ciliary muscle contraction as age increases leaving a reserve ability of ciliary muscle to contract with age. If Fincham's theory is correct, a mild parasympatholytic drug would produce a decrease in the amplitude of accommodation, a mild parasympathomimetic drug would produce an increase in the amplitude of accommodation, and the AC/A ratio would increase with age. The results of this study indicate that all three of these do occur and therefore support the Fincham concept of the cause of presbyopia.

Why is intraocular pressure elevated in chronic simple glaucoma? Anatomical considerations

Ultrastructural analysis of 400 trabeculectomy specimens of glaucomatous eye revealed three types of extracellular deposits within the cribriform layer of the trabecular meshwork. One of these derives from the sheath of the subendothelial elastic-like fibres. Tissue culture and ultrahistochemical studies led to the assumption that these deposits contain glycoproteins, probably secreted by the cribriform layer cells.

Ciliochoroidal detachment

Ciliochoroidal detachments occur under a variety of pathological circumstances and are most commonly noted following intraocular surgery where hypotony is combined with postoperative inflammation. Although the condition is easily recognized, the pathophysiologic mechanisms involved are not well understood. In this review, the pathophysiologic mechanisms are summarized, with special emphasis on fluid dynamics within the suprachoroidal space. The clinical features, etiology and treatment of ciliochoroidal detachments are also reviewed.

Causes of refraction changes: a classification

This classification of refraction changes suggests new and early approaches to the treatment of complications of myopia. By appreciating the ultrasonic work on accommodation by Coleman, The field is opened for a fresh study of such diseases as macular degeneration; diseases of the vitreous, even glaucoma; cataracts; and retinal detachments. Other diseases of the retina for which the causes are obscure may be viewed for possible help, if not a cure.

Physiologic vs pathologic myopia: genetics vs environment

Physiologic myopia occurs as the result of a correlation failure of refraction components in the normal eye. Pathologic myopia is caused by excessive axial elongation that primarily involves the ora-equatorial area and the posterior pole. Peripheral fundus changes and posterior staphyloma formation are ophthalmoscopic evidences of this process. Heredity is the basic determinant of ocular refraction, but numerous agents produce both temporary and permanent myopias.

Anterior segment reactions after experimental trauma to rabbit eyes

The effect of experimentally induced uniocular trauma was investigated in the adult albino rabbit by means of iris fluorescein angiography. Paracentesis, blunt trauma, occlusion of all four vortex veins or of the two long posterior ciliary arteries, or local instillation of nitrogen mustard, were performed in a number of animals, some of which received systemic aspirin preoperatively. Iris angiograms of the injured and the contralateral eye were performed immediately after the traumatic insult. The injured eye always showed an increased permeability to fluorescein. Except for paracentesis, the ipsilateral response often included ischemia of the iris. The contralateral eye always showed an increase in fluorescein permeability into the aqueous. In some cases, sector ischemia of the contralateral iris was seen. Aspirin inhibited some ipsilateral responses but had no effect on the consensual reactions. It is concluded that ipsilateral trauma almost invariably causes a contralateral reaction in the rabbit eye, which is more severe if the injury creates ischemia of the iris. Since these reactions are inefficiently blocked by aspirin, they are not prostaglandin-mediated. The interocular pathway involved may be neural or vascular in nature.

[Prevention of malignant glaucoma: pars-plana vitrectomy? (author's transl)]

Prevention of malignant glaucoma: in first case report lens extraction and trabeculectomy was followed by a malignant glaucoma; in the second case report pars-plana vitrectomy and trabeculectomy was successful. The role of a vitreous posterior blockage is discussed.