HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Electronic Letters to:

Lens: Lisa A. Ostrin and Adrian Glasser Comparisons between Pharmacologically and Edinger-Westphal–Stimulated Accommodation in Rhesus Monkeys Invest. Ophthalmol. Vis. Sci. 2005; 46: 609-617 [Abstract] [Full text] [PDF]

eLetters: Submit a response to this article

Electronic letters published:

Controls Needed for Eye Movements

Ronald A. Schachar   (20 October 2005)

Author Response: Controls Needed for Eye Movements

Adrian Glasser   (20 October 2005)

Controls Needed for Eye Movements 20 October 2005
Ronald A. Schachar Send letter to journal: Re: Controls Needed for Eye Movements ron{at}2ras.com Ronald A. Schachar	Ostrin and Glasser1 have reported that the crystalline lenses of rhesus monkeys respond differently to topical carbachol and electrical stimulation of the Edinger-Westphal (EW) nucleus. Since EW electrical stimulation may induce confounding head and eye movements in addition to intraocular movements, controls are required to isolate the intraocular movements from the extraocular noise.2 In addition, extraocular movements may occur between acquisition of images following carbachol instillation. No controls for these types of confounding movements were provided by the authors and are essential before their findings can be evaluated. Ronald A. Schachar Dallas, Texas References 1. Ostrin LA, Glasser A. Comparisons between pharmacologically and Edinger-Westphal-stimulated accommodation in rhesus monkeys. Invest Ophthalmol Vis Sci. 2005;46:609-617. 2. Schachar RA, Kamangar F. Computer image analysis of ultrasound biomicroscopy of primate accommodation. Eye. 8 April 2005;doi:10.1038/sj.eye.6701838 [Epub].
Author Response: Controls Needed for Eye Movements 20 October 2005
Adrian Glasser Send letter to journal: Re: Author Response: Controls Needed for Eye Movements aglasser{at}uh.edu Adrian Glasser	Dr. Schachar has written a response to our paper in which we describe differences in anterior segment biometry with centrally and pharmacologically stimulated accommodation in Rhesus monkeys.1 We reported that during Edinger-Westphal (EW) stimulated accommodation, the anterior surface of the lens moves forward, and the posterior surface of the lens moves backwards and that during pharmacologically stimulated accommodation, the anterior surface of the lens moves forward, and the posterior surface initially moves backwards and then moves forward to result in a forward movement of the entire lens. Dr. Schachar states that EW stimulated accommodation induces head and eye movements, and therefore, appropriate controls must be presented in order to evaluate our findings. Contrary to Schachar's assertion, EW stimulation does not produce head movements. The monkeys are anesthetized, and the head is stabilized in a head holder. The extent to which head and eye movements may occur is no different between EW stimulation and carbachol stimulation.2 Sutures are placed behind the lateral and medial rectus muscles to decrease convergent eye movements, as we described. Dr. Schachar also states that extraocular movements may occur between acquisition of images following carbachol instillation. Contrary to Schachar's assumption, image acquisition is not used to perform a-scan ultrasound. While small eye movements may occur during both central and pharmacological stimulation, they do not affect the overall results of our study, which clearly indicate that biometry is different between centrally and pharmacologically stimulated accommodation. Similar differences between voluntary accommodation and drug stimulated accommodation have been reported in conscious human subjects where neither EW stimulation nor image analysis was used (Findl O, et al. IOVS 2004;45:E-Abstract 1744). Lisa Ostrin Adrian Glasser University of Houston, College of Optometry, Houston, Texas References 1. Ostrin LA, Glasser A. Comparisons between pharmacologically and Edinger-Westphal-stimulated accommodation in rhesus monkeys. Invest Ophthalmol Vis Sci. 2005;46:609-617. 2. Glasser A, Kaufman PL. The mechanism of accommodation in primates. Ophthalmology. 1999;106:863-872.