[Cataract surgery in 79 patients with relative anterior microphthalmus (RAM): a review of anatomy, associated pathology and complications]

Comparative analysis of white-to-white and angle-to-angle distance measurements with partial coherence interferometry and optical coherence tomography

PURPOSE

To perform white-to-white (WTW) and angle-to-angle (ATA) distance measurements with 2 optical devices and analyze the correlation with other anterior segment parameters.

SETTING

Department of Ophthalmology, Medical Health and Science Center, University of Debrecen, Debrecen, Hungary.

DESIGN

Comparative case series.

METHODS

In this prospective study, the WTW distance, axial length (AL), and anterior chamber depth (ACD) were measured by partial coherence interferometry (PCI) (IOLMaster). The horizontal and vertical ATA distances and ACD were assessed by anterior segment optical coherence tomography (AS-OCT) (Visante).

RESULTS

The mean PCI values were AL, 23.31 mm ± 1.52 (SD); WTW distance, 11.99 ± 0.47 mm; ACD, 2.99 ± 0.4 mm. On AS-OCT, the mean horizontal ATA was 11.43 ± 0.51 mm and the mean vertical ATA, 10.72 ± 0.66 mm. The WTW distance was significantly greater than the horizontal ATA distance, and the horizontal ATA distance was significantly greater than the vertical ATA distance (P<.0001). The correlations between WTW and horizontal ATA (r = 0.51; P<.0001), vertical ATA (r = 0.32; P<.0021), AL (r = 0.45; P<.0001), and patient age (r = -0.28; P = .023) were significant. The PCI WTW distance and ACD were significantly correlated (r = 0.55; P<.0001). There were no significant correlations between AS-OCT horizontal and vertical ATA measurements (r = -0.02; P = 0.79) or between same-device ACD measurements (r = 0.18; P = .15).

CONCLUSIONS

Although PCI WTW and AS-OCT ATA measurements are not clinically interchangeable, the WTW values correlated well with horizontal and vertical measurements and other anterior segment parameters.

White-to-white corneal diameter: normal values in healthy humans obtained with the Orbscan II topography system

PURPOSE

The corneal horizontal diameter (white-to-white) is abnormal in diseases like microcornea, relative anterior microphthalmos, and corneal dystrophies. Because normal values are described imprecisely in the literature, the purpose of this study was to reevaluate the horizontal corneal diameter as a scientific parameter.

METHODS

The horizontal corneal diameter was measured with the Orbscan II system in 370 right eyes and 373 left eyes of 390 healthy white subjects aged 10-80 years. There were 148 female subjects and 242 male subjects. Each measurement was repeated twice. Differences in gender, between right and left eyes, and age-related alterations were analyzed statistically.

RESULTS

The average corneal diameter was 11.71 +/- 0.42 mm. The average corneal diameter was 11.77 +/- 0.37 mm in males compared with 11.64 +/- 0.47 mm in females. The resulting normal ranges were 11.04 to 12.50 for males and 10.70 to 12.58 mm for females. Differences in gender were not significant in the t test for independent samples (P = 0.071). There were no statistically significant differences between right and left eyes in the t test for dependent samples (P = 0.16). Corneal diameters decreased slightly with age.

CONCLUSIONS

With the obtained normal values, more precise determination of microcornea and macrocornea will be possible in the future. The horizontal corneal diameter was not significantly greater in males than in females. Further studies are needed to show the reasons for the age-related decrease in measurements.

Exfoliation syndrome

Exfoliation syndrome (XFS) is an age-related disorder of the extracellular matrix characterized by production and progressive accumulation of small, white deposits of a fibrillar extracellular material in many ocular tissues, most commonly seen on the pupillary border and anterior lens capsule. Characteristic signs of pigment liberation and deposition throughout the anterior segment aid in the diagnosis. Exfoliation syndrome predisposes to both open-angle and angle-closure glaucoma, and to capsular rupture, zonular dehiscence, and vitreous loss during cataract extraction. Exfoliation syndrome is associated with ocular and perhaps systemic ischemia. The exact chemical composition of exfoliation material remains unknown. Medical, laser, and surgical therapy are similar to treatment of primary open-angle glaucoma.

Exfoliation syndrome

Exfoliation syndrome (XFS) is an age-related disease in which abnormal fibrillar extracellular material is produced and accumulates in many ocular tissues. Its ocular manifestations involve all of the structures of the anterior segment, as well as conjunctiva and orbital structures. Glaucoma occurs more commonly in eyes with XFS than in those without it; in fact, XFS has recently been recognized as the most common identifiable cause of glaucoma. Patients with XFS are also predisposed to develop angle-closure glaucoma, and glaucoma in XFS has a more serious clinical course and worse prognosis than primary open-angle glaucoma. There is increasing evidence for an etiological association of XFS with cataract formation, and possibly with retinal vein occlusion. XFS is now suspected to be a systemic disorder and has been associated preliminarily with transient ischemic attacks, stroke, systemic hypertension, and myocardial infarction. Further ramifications await discovery. Deposits of white material on the anterior lens surface are the most consistent and important diagnostic feature of XFS. The classic pattern consists of three distinct zones that become visible when the pupil is fully dilated. Whereas the classic picture of manifest XFS has been often described, the early stages of beginning exfoliation have not been well defined. Next to the lens, exfoliation material is most prominent at the pupillary border. Pigment loss from the iris sphincter region and its deposition on anterior chamber structures is a hallmark of XFS. Despite extensive research, the exact chemical composition of exfoliation material (XFM) remains unknown. An overproduction and abnormal metabolism of glycosaminoglycans have been suggested as one of the key changes in XFS. The protein components of XFM include both noncollagenous basement membrane components and epitopes of the elastic fiber system such as fibrillium. Regardless of etiology, typical exfoliation fibers have been demonstrated electron microscopically in close association with the pre-equatorial lens epithelium, the nonpigmented ciliary epithelium, the iris pigment epithelium, the corneal endothelium, the trabecular endothelium, and with almost all cell types of the iris stroma, such as fibrocytes, melanocytes, vascular endothelial cells, pericytes, and smooth muscle cells. The presence of XFS should alert the physician to the increased risks of intraocular surgery, most commonly zonular dehiscence, capsular rupture, and vitreous loss during cataract extraction. Heightened awareness of this condition and its associated clinical signs are important in the detection and management of glaucoma, and preoperative determination of those patients at increased risk for surgical complications.