The role of retinotopic cues in deciphering the direction and magnitude of monocular dynamic ocular accommodation: A review.

Accommodative responses of humans operate seamlessly to ensure clear vision of targets at different viewing distances, up until the onset of presbyopia. To achieve this, the visual system must correctly decipher the polarity and magnitude of retinal defocus in real-time, and often under very challenging viewing conditions. The past seven decades of research in this area has identified several retinotopic cues that may potentially provide the desired odd- and even-error information to the visual system for solving these challenges.

IMI Accommodation and Binocular Vision in Myopia Development and Progression.

The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression.

Do visual performance and optical quality vary across different contact lens correction modalities in keratoconus?

Purpose: While several advanced contact lens (CL) designs are commercially available for vision correction in keratoconus, their visual performance and optical quality, relative to each other and controls remains unclear. This prospective, crossover study tested the hypothesis that these CL designs would have a differential impact on visual performance and optical quality in subjects with advanced keratoconus, but not in early to moderate disease states.

Methods: Spatial vision (logMAR acuity and contrast sensitivity), depth vision (stereoacuity) and optical quality (higher-order wavefront aberrations) were measured on 28 bilaterally mild to advanced keratoconics (age: 20-28yrs; 15 males), novice to CL wear, and in 10 age-matched controls using well-established psychophysical and aberrometry techniques.

Surgically induced astigmatism and refractive outcomes following phacotrabeculectomy.

Purpose: To objectively evaluate surgically induced astigmatism (SIA) after phacotrabeculectomy using keratometry and topography and to compare the magnitude of SIA and the refractive outcomes of single-site and twin-site phacotrabeculectomies.

Methods: Forty prospective subjects were enrolled in the study and were randomized into single-site and twin-site cohorts. SIA was objectively assessed using keratometry and Orbscan before and at three months after surgery.

Lens magnification affects the estimates of refractive error obtained using eccentric infrared photorefraction.

Positive- and negative-powered ophthalmic lenses are used in eccentric infrared photorefraction to calibrate the device, correct the subject's baseline refractive error before an experimental manipulation, or stimulate blur-driven accommodation. Through theoretical modeling of luminance gradients formed across the pupil and empirical measurements of the eye's refractive error using a commercial photorefractor, this study shows that image magnification by positive lenses and image minification by negative lenses under- and overestimates the refractive error, respectively, all independent of image defocus. The impact of image magnification/minification therefore appears non-trivial in experimental paradigms involving ophthalmic lenses to manipulate the eye's optics during photorefraction.

Corneal Transplantation in Disease Affecting Only One Eye: Does It Make a Difference to Habitual Binocular Viewing?

Background: Clarity of the transplanted tissue and restoration of visual acuity are the two primary metrics for evaluating the success of corneal transplantation. Participation of the transplanted eye in habitual binocular viewing is seldom evaluated post-operatively. In unilateral corneal disease, the transplanted eye may remain functionally inactive during binocular viewing due to its suboptimal visual acuity and poor image quality, vis-à-vis the healthy fellow eye.