[Nd-YAG laser iridotomy in pigment dispersion syndrome and pigment dispersion glaucoma]

Anterior-segment morphology and corneal biomechanical characteristics in pigmentary glaucoma

Purpose

The aim of the study reported here was to evaluate characteristics of the anterior-segment via anterior-segment optical coherence tomography (AS-OCT) and corneal biomechanical properties using an ocular response analyzer and their changes by peripheral laser iridotomy (PI) in patients with pigmentary glaucoma (PG).

Materials and methods

Seventeen eyes with PG were included consecutively. AS-OCT and ocular response analyzer measurements were taken before and 3 months after PI. Baseline morphology and change in morphology were analyzed by correlation and multiple linear regression analysis. The main parameters assessed were anterior-chamber (AC) angles and volume as well as corneal hysteresis (CH) and corneal resistance factor.

Results

AC angles were found to have decreased significantly in each quadrant after PI (P<0.001), with the highest effect seen in the temporal quadrant, which decreased from 57.0°±9.6° to 44.1°±5.2° (± standard deviation). Mean AC volume decreased significantly from 213.1±36.4 to 187.0±23.4 mm³ (P<0.001). CH and corneal resistance factor did not change after PI. CH was found to correlate with the preoperative superior and inferior angle width (Spearman’s rho 0.553 and 0.615, respectively, P<0.05). Biomechanical parameters showed no predictive value on the change of AC angles or volume.

Conclusion

PI in eyes with PG results in a highly significant reduction in the AC angles and volume as visualized by AS-OCT, with the largest effect seen in the temporal quadrant. CH is strongly positively correlated with the superior and inferior preoperative AC angles, emphasizing the importance of the biomechanical properties of the cornea for glaucoma pathogenesis in PG, but corneal biomechanical properties cannot predict PI-related AC changes.

[Is prophylactic YAG iridotomy useful in pigment dispersion syndrome?]

Despite theoretical considerations concerning the advantage of iridotomy in eyes with pigment dispersion syndrome or early pigment glaucoma, there is a lack of clinical evidence that this procedure has a long-term effect in preventing glaucoma damage under these circumstances. However, several factors may contribute to this lack of evidence, e.g. the statistical problem of a low conversion rate from pigment dispersion syndrome to pigment glaucoma or the inclusion criteria in the studies treating patients older than 40 years or genetic dispositions in pigment glaucoma that are not yet fully clear. On the basis of current data the decision for YAG iridotomy should only be taken in patients younger than 40 years, if the midperipheral iris shows an inverse bowing and the intraocular pressure is normal or slightly increased with no progressive signs of optic nerve damage. In cases of insufficient intraocular pressure and visual defects due to glaucomatous optic nerve damage, incisional glaucoma surgery is usually necessary especially in younger patients with a long life expectancy.

Klassifikation biomedizinischer Forschungsberichte als Grundlage evidenzbasierter Medizin in der Augenheilkunde

BACKGROUND

Evidence-based medicine requires careful appraisal of published data derived from experimental and clinical studies. Based on classification of biomedical research reports, evidence levels can be determined and recommendations for therapeutic decisions can be made.

METHODS

A classification system for clinical studies was developed. It was evaluated in classifying the reports published in Der Ophthalmologe during 2003-2004 (study design: descriptive cross-sectional study, case series).

RESULTS

In the 2-year interval, 70 longitudinal and 95 cross-sectional studies were published. The vast majority of the longitudinal studies were interventional cohort studies. Not considering case reports, 73% of the original articles were longitudinal prospective studies, 1% were retrospective (case-control) studies, and 26% were cross-sectional studies.

CONCLUSIONS

The study design of all published articles could be classified using the classification system. This classification system proves to be applicable in the context of clinical studies in ophthalmology and may be helpful in the process of critical appraisal of the literature and synthesis of clinical evidence and an evidence-based recommendation.

The Effects of Iridotomy Size and Position on Symptoms Following Laser Peripheral Iridotomy

PURPOSE

To evaluate visual disturbances following laser peripheral iridotomy (LPI). Patients sometimes note visual disturbances following laser peripheral iridotomy. The purpose of this study was to provide what we believe to be the first systematic evaluation of these visual disturbances, including a determination of whether or not they are associated with characteristics of a primary patent laser peripheral iridotomy, such as lid position and size of the iridotomy.

PATIENTS AND METHODS

This was a case series of 93 consecutive (172 eyes) glaucoma patients who had had an Nd: YAG laser peripheral iridotomy. Patients returning for a follow-up visit after laser peripheral iridotomy were selected. A standardized questionnaire was prospectively administered to the study patients at least 1 month after their laser peripheral iridotomy had been performed, inquiring if they experienced any of the following either before or after the iridotomy: halo, lines, crescent, ghost image, glare, spots, shadows, blurring, or other unlisted visual disturbances. On the same visit when they answered the questionnaire, the patients were examined at the slit lamp to assess the location, lid coverage status, and size of the laser peripheral iridotomy. Selection for the performance of the LPI was not prospective. A series of 93 consecutive patients served as controls.

RESULTS

Seven (4%) of the 172 study eyes had postoperative visual symptoms of shadows, ghost images, crescents, or lines. Ninety (52.3%) of the laser peripheral iridotomies were covered by the upper lid, 40 (23%) were completely exposed, and 42 (24%) were partially exposed. Visual disturbances (those listed above plus glare, blurring, haloes, spots, and miscellaneous) occurred in 8 of the 90 (8.9%) eyes with completely covered laser peripheral iridotomies, in 11 of the 42 (26%) with partially covered laser peripheral iridotomies, and in 7 of the 40 (17.5%) with fully exposed LPIs.

CONCLUSION

Visual symptoms following laser peripheral iridotomy are more likely to occur in patients who have partially or fully exposed laser iridotomies than in those in whom the iridotomy is completely covered by the lid.