Intra-Ocular Pressure Measurement in a Patient with a Thin, Thick or Abnormal Cornea.

Accurate measurement of intra-ocular pressure is a fundamental component of the ocular examination. The most common method of measuring IOP is by Goldmann applanation tonometry, the accuracy of which is influenced by the thickness and biomechanical properties of the cornea. Algorithms devised to correct for corneal thickness to estimate IOP oversimplify the effects of corneal biomechanics. The viscous and elastic properties of the cornea influence IOP measurements in unpredictable ways, a finding borne out in studies of patients with inherently abnormal and surgically altered corneal biomechanics. Dynamic contour tonometry, rebound tonometry and the ocular response analyzer provide useful alternatives to GAT in patients with abnormal corneas, such as those who have undergone laser vision correction or keratoplasty. This article reviews the various methods of intra-ocular pressure measurement available to the clinician and the ways in which their utility is influenced by variations in corneal thickness and biomechanics.

Objective accommodation measurement of the Crystalens HD compared to monofocal intraocular lenses.

PURPOSE: Objective evaluation of accommodation with a bilateral accommodating intraocular lens (IOL) versus monofocal IOLs. METHODS: Patients received accommodating IOL (Crystalens HD; Bausch & Lomb, Rochester, NY) bilaterally after cataract surgery. These were compared to a matched group receiving monofocal IOLs. Preoperative and postoperative distance corrected distance, intermediate, and near vision were evaluated. Objective accommodation was measured with the WAM-5500 Binocular Autorefractor/Keratometer (Grand Seiko, Pty Ltd., Hiroshima, Japan). RESULTS: Nineteen patients were included. Ten received the Crystalens HD in both eyes and nine received one of three monofocal lenses in each eye. Mean postoperative distance corrected distance visual acuity was not statistically different between the two groups. Mean distance corrected intermediate vision was better in the Crystalens HD group (logMAR 0.24 ± 0.11 [control], logMAR 0.11 ± 0.10 [Crystalens HD], P = .033). The groups did not differ significantly for mean distance corrected near vision (logMAR 0.54 ± 0.12 [control], logMAR 0.42 ± 0.15 [Crystalens HD], P = .087). However, a significantly greater proportion of Crystalens HD eyes achieved 0.4 or 0.3 logMAR for near wearing their distance correction (P = .013). With distance correction, the mean spherical equivalent failed to show any myopia with accommodative effort in either group. Low contrast and low luminance contrast acuity were not significantly different. CONCLUSION: The Crystalens HD showed some benefit for intermediate visual function compared to the monofocal IOLs with both groups wearing full correction for distance. There were no significant signs of accommodation in either group.

The potential of viral vector-mediated gene transfer to prolong corneal allograft survival.

The cornea is a particularly attractive target for gene therapy designed to improve the outcome of corneal transplantation. First, there is a clear and well-defined clinical need. Second, because donor corneas can be preserved for days if not weeks within an eye bank, ex vivo transduction of a donor cornea can be carried out without the urgency associated with many other forms of transplantation. Finally, the partial sequestration of the eye from the systemic circulation decreases the likelihood of spillover of vector and transgene, and the immune privileged nature of the cornea and anterior segment affords a degree of protection from immune responses directed against the vector. A wide range of vectors has been investigated for gene transfer to the cornea. A number of viral vectors, in particular, have proved to be efficient at transducing the cornea and in association with a variety of transgenes, have been used successfully to prolong corneal allograft survival significantly in animal models. The most suitable such vector for future clinical studies in corneal transplantation has yet to be determined, but the most likely include recombinant adenoviral, adeno-associated viral and lentiviral vectors. In this review, we examine the ability of these viral vectors to transduce the cornea, and summarise those studies in which gene therapy has been used to prolong experimental corneal allograft survival.