Comparison of optical coherence tomography and scanning laser polarimetry in glaucoma, ocular hypertension, and suspected glaucoma

BACKGROUND AND OBJECTIVE

To compare the performance of the newest generation optical coherence topography (OCT) and scanning laser polarimetry with variable corneal compensation (SLP-VCC) in eyes with glaucoma, ocular hypertension, and suspected glaucoma.

PATIENTS AND METHODS

One eye each of 84 patients (30 with glaucoma, 26 with suspected glaucoma, and 28 with ocular hypertension) was included in the study. Retinal nerve fiber layer (RNFL) thickness was measured with both technologies and thickness parameters were compared in the three groups of eyes. The correspondence of RNFL thickness measurements with visual field function was also studied.

RESULTS

Average OCT-RNFL thickness was found to have a statistically significant difference between patients with glaucoma and either suspected glaucoma or ocular hypertension. A statistically significant correlation between the average RNFL thicknesses measured by the two different technologies was shown only in the glaucoma group. A significant correlation with visual field mean deviation was found for superior average RNFL thickness as measured by SLP and for nerve fiber indicator and average and inferior average RNFL thickness as measured by OCT in glaucomatous eyes. Regression analysis indicated nerve fiber indicator to be the most valuable factor in predicting mean deviation.

CONCLUSION

RNFL thickness measurements obtained with OCT and SLP-VCC correlate well only in eyes with more advanced glaucomatous damage. The nerve fiber indicator parameter derived by SLP correlated best with mean deviation.

Acanthamoeba Keratitis and Contact Lens Disinfecting Solutions

OBJECTIVES

To report cases of culture-proved Acanthamoeba keratitis in Greece over a 10-year period and to evaluate the effectiveness of the commonly used commercial contact lens disinfecting systems in clinical cases of Acanthamoeba keratitis.

MATERIAL AND METHODS

During the years 1994-2004, 45 contact lens wearers and 3 non-contact lens wearers presenting with symptoms and signs of keratitis underwent corneal sampling. The scrapings obtained were inoculated directly onto appropriate culture media for bacteria, fungi and Acanthamoeba. All proved positive for Acanthamoeba. The contact lenses and contact lens disinfecting solutions (16 one-step 3% hydrogen peroxide and 3 multipurpose solutions) of 19/45 patients with culture-proven Acanthamoeba keratitis were cultured for bacteria, fungi and Acanthamoeba.

RESULTS

Acanthamoeba was isolated from contact lenses and contact lens disinfecting solutions in all 19 cases of Acanthamoeba keratitis studied.

CONCLUSIONS

The main risk factor for corneal infection in contact lens wearers is the use of contact lens disinfecting systems ineffective at killing Acanthamoeba cysts and trophozoites, as well as bacteria and fungi. Improvement or development of new contact lens disinfecting systems by manufacturers is needed to prevent Acanthamoeba keratitis.

Optical coherence tomography appearance of "drusenoid" pigment epithelial detachment

A case of bilateral "drusenoid" pigment epithelial detachment that was studied with fundus fluorescein angiography and optical coherence tomography is described. Fundus fluorescein angiography depicted staining of the drusen without any sign of pooling of the dye, whereas optical coherence tomography displayed detachment of the retinal pigment epithelium. These findings remained unchanged during a 10-month period.

Corneal Topography for Intraocular Lens Power Calculations

BACKGROUND

In patients undergoing cataract extraction with PC IOL insertion, pre-op and post-op corneal power measurement is necessary to calculate induced astigmatism. In cases with irregular corneal astigmatism, measurements with traditional keratometry is inaccurate. We report the use of video keratography in three cases that required keratometry readings in order to calculate IOL power. These cases were characterized by irregular or incomplete keratometer mires, so quantitative descriptors derived from computer-assisted corneal topography (TMS-1) were used instead.

CONCLUSION

The standard keratometer is useless in cases in which the mires appear irregular or incomplete. In such cases, computer-assisted corneal topography can be used successfully. Recently, a new corneal topography index has been developed, the average corneal power, which is a measure of the average corneal power within the entrance pupil. We are currently evaluating the use of average corneal power to assist in the calculation of IOL powers.