BILATERAL ECCENTRIC FIXATION WITH NO OCULAR DEVIATION IN A CASE OF HEREDO-MACULAR DEGENERATION

Eccentric gaze direction in patients with central field loss

PURPOSE

This study describes the binocular eccentric gaze direction (EGD) of 434 patients with binocular central field loss and presents a comparison with other studies on eccentric gaze behavior.

METHODS

We reviewed the records of 434 patients with bilateral central scotomas. Eligible patients had not received eccentric viewing training and demonstrated a spontaneously developed eccentric gaze behavior. Data were collected on monocular and binocular EGD, visual acuity, and underlying ocular pathology. Findings concerning the EGD were compared with other studies that evaluated gaze behavior in patients with central field loss.

RESULTS

In the group of 434 patients, age-related macular disease was the most frequent pathology (77%). The majority of these patients demonstrated a binocular EGD (bEGD) to the right (50%). In 25% of the patients, a superior bEGD was found. Less often, a bEGD to the left (14%) and to inferior (11%) were encountered. Review of the literature indicates that the majority of patients developed a monocular EGD in the superior direction.

CONCLUSIONS

This is a study on bEGD behavior in a large population of patients with bilateral central scotomas. The bEGD was guided by the gaze of the better-seeing eye. The preference for a bEGD to the right differs from findings of previous studies. Review of the literature suggests that not only the ocular pathology but also the method of investigation is most likely to influence the observed EGD. Most studies evaluated the location of the preferred retinal locus using a monocular technique; this may not reflect an individual's actual binocular behavior as it relates to activities of daily living.

Preferred retinal loci and macular scotoma characteristics in patients with age-related macular degeneration

Many patients with macular scotomas due to age-related macular degeneration do not perceive black spots in the visual field where the scotomas are located. Rather, they describe objects as "vanishing," "jumping out of nowhere" or "having blurry parts," or a combination of features. In addition, when the macular scotoma affects the fovea, the visual system uses 1 or more preferred retinal loci (PRLs) as a "pseudofovea" to perform visual tasks. Visual function testing with the scanning laser ophthalmoscope has provided a wealth of information regarding how patients perceive the visual world and how the oculomotor system directs eye movements. This article describes 2 specific functions of the oculomotor system, fixation stability and refixation precision, with data collected from normally sighted people and patients with visual field loss. The implications of the characteristics of PRLs and macular scotomas for clinical testing are discussed.

Preferred retinal loci relationship to macular scotomas in a low-vision population

PURPOSE

The authors identified patterns in preferred retinal locus (PRL) ability and location relative to macular scotomas in a low-vision patient population.

METHODS

Scanning laser ophthalmoscope macular perimetry and PRL testing were performed on 825 patients with low vision. The PRL location was determined, and a PRL scoring system was devised and used to measure the pursuit ability, fixation stability, and saccadic ability of the PRL. The characteristics of dense scotomas within 2.5 degrees of the PRL were noted.

RESULTS

Eighty-four percent (1130 of 1339 eyes) of the eyes had an established PRL. Preferred retinal loci varied across the full range of ability scores and varied in size for fixation stability from 1.0 degrees to 9.0 degrees in diameter. There was a central dense scotoma in 82.5% of the eyes, whereas 8.4% had a paracentral dense scotoma. In 14.8% of the eyes, the PRL had no dense scotomas on any of its borders; one, two, three, or four (a ring) borders had a dense scotoma in 39.7%, 19.0%, 9.0%, and 17.4% of eyes, respectively. When the PRL had only one scotomatous border, the resulting field defect was located superior in 39.0%, right in 33.7%, left in 19.9%, and inferior in 7.5% of eyes.

CONCLUSIONS

The majority of patients with low vision, as many as four of five patients, have dense scotomas encumbering the PRL for visual tasks. Approximately one of six patients with low vision have the PRL completely surrounded by dense scotomas. The visual system shows a strong tendency not to place a PRL anatomically above a scotoma (field defect below fixation) and a weaker tendency not to place the PRL anatomically to the right of a scotoma (field defect to the left of fixation). Macular perimetry and PRL evaluations can provide considerable information on the functional status of the macula, which may be useful to rehabilitation professionals.

Accommodation in humans with juvenile macular degeneration

Accommodation, or the change in refractive power of the eye to focus objects at different distances, is driven by many stimuli including defocus blur, the awareness of target distance or proximal cues, and through the vergence crosslink (convergence accommodation). The effectiveness of defocus blur as an accommodative stimulus is decreased in normally-sighted subjects as visual acuity is experimentally reduced and as the target is imaged at increasing eccentricities from the fovea. Since subjects with central retinal abnormalities have reduced visual acuity and typically fixate eccentrically, one would predict that defocus blur would not be an effective accommodative stimulus for them. Using an infrared optometer, steady-state accommodative responses of six subjects with juvenile macular degeneration (JMD) and of three normally-sighted controls were measured. The effectiveness of defocus blur in stimulating accommodation varied across the subjects and was related to visual acuity, with those subjects having worse acuity showing less accurate accommodative responses. When provided with additional cues to accommodative demand (i.e. proximal and/or binocular cues), subjects with JMD showed more accurate accommodative responses. In general, those subjects who did not modulate accommodative response with changing defocus blur cues showed the most accurate accommodation under binocular viewing. In contrast, those subjects who did change accommodative response with changing defocus blur cues showed the most accurate accommodation under monocular viewing.

Characteristics and low vision corrections in Stargardt's disease. Educational and vocational achievements enhanced by low vision corrections

One hundred and sixteen patients with Stargardt's disease demonstrated the most useful optical aids that enabled them to obtain an education and employment. The most useful optical aid for distance was the 8X monocular focusable telescope. For near, high-add bifocals, tri-focals, half-eye binocular spectacle magnifiers, paperweight-type magnifiers and hand magnifiers were most useful. Optical aids were prescribed for 102 patients with a success rate of 96%. The progression of visual loss is generally gradual and symmetrical terminating within ten years after onset and not becoming worse than 20/800 (6/240). Academic success seems to be related more to intellectual ability than degree of visual impairment. Highly trained and educated individuals with Stargardt's disease were able to find employment and perform duties usually associated with normal vision.