Factors affecting contrast sensitivity with the Artisan phakic intraocular lens for high myopia

Relationships Between Spatial Contrast Sensitivity and Parafoveal Cone Density in Normal Subjects and Patients With Retinal Degeneration

BACKGROUND AND OBJECTIVE

To investigate the relationship between spatial contrast sensitivity (CS) and parafoveal cone density (PCD).

PATIENTS AND METHODS

Fifteen healthy individuals (mean age: 26.1 years ± 4.5 years) and nine patients with hereditary retinal degeneration (mean age: 31.6 years ± 13.4 years) without media opacities were studied. The CS was measured by CSV-1000 (VectorVision, Greenville, OH). The cone mosaic was photographed with an adaptive optics scanning laser ophthalmoscope (AOSLO) with a 1° × 1° field of view centered on the fovea. The PCD was calculated in an annular area with radii of 0.38° and 0.43°. The CS was converted to the logarithm (logCS), and the area under the logCS function (AULCSF) was determined.

RESULTS

The AULCSF was significantly and positively correlated with the PCD in the control (R² = 0.522; P = .003) and retinal degeneration (R² = 0.514; P = .03) groups.

CONCLUSION

PCD can predict the spatial contrast sensitivity in normal subjects or patients with retinal degeneration without media opacities. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:106-113.].

Evaluation of the precision of contrast sensitivity function assessment on a tablet device

The contrast sensitivity function (CSF) relates the visibility of a spatial pattern to both its size and contrast, and is therefore a more comprehensive assessment of visual function than acuity, which only determines the smallest resolvable pattern size. Because of the additional dimension of contrast, estimating the CSF can be more time-consuming. Here, we compare two methods for rapid assessment of the CSF that were implemented on a tablet device. For a single-trial assessment, we asked 63 myopes and 38 emmetropes to tap the peak of a “sweep grating” on the tablet’s touch screen. For a more precise assessment, subjects performed 50 trials of the quick CSF method in a 10-AFC letter recognition task. Tests were performed with and without optical correction, and in monocular and binocular conditions; one condition was measured twice to assess repeatability. Results show that both methods are highly correlated; using both common and novel measures for test-retest repeatability, however, the quick CSF delivers more precision with testing times of under three minutes. Further analyses show how a population prior can improve convergence rate of the quick CSF, and how the multi-dimensional output of the quick CSF can provide greater precision than scalar outcome measures.

Pupillary Block Glaucoma After Implantation of Iris-Fixated Phakic Intraocular Lens

To report a case of pupillary block glaucoma after implantation of iris-fixated phakic intraocular lens (IF pIOL). A 43-year-old man was referred for pupillary block one day after implantation of IF pIOL. Slit-lamp examination revealed extremely shallow anterior chamber, closure of peripheral laser iridotomy and contact of iris on the peripheral of the optics of IF pIOL. The intraocular pressure (IOP) was 62 mm Hg. The iris moved forward in contact with the IF pIOL and the lens remained in the physiologic position, which made the distance between the lens and the iris wide. He underwent an uneventful peripheral surgical iridectomy and the IOP decreased to 6 mm Hg. Acute pupillary block glaucoma can occur after IF pIOL implantation due to the occlusion of aqueous flow between the IF pIOL and the iris if the peripheral iridotomy closes.