MATERIALS AND METHODS

Twenty four eyes from 23 consecutive patients (12 men and 11 women) with PEDs were examined between February 1998 to May 2001. The clinical findings are listed in the Table 1.

Statistical significance was determined by using the χ², unpaired t, or Mann-Whitney U tests. A p value of <0.05 was considered significant.

The tenets of the Declaration of Helsinki were followed, and informed consent was obtained from all subjects.

RESULTS

A PED was confirmed in all of the patients by ophthalmoscopy (Fig 1A, E, I, and M).

OCT findings

OCT images showed a dome-like elevation of the RPE corresponding to the PEDs. The PEDs were divided into two groups by the presence or absence of a highly reflective line in the OCT images that divided the PEDs at the level of the RPE. Eyes in group 1 (n = 15) showed the same reflex in the area of PEDs as that observed under the RPE in other parts of the PEDs. Cases in group 1 with a PED of less than 1 disc diameter (DD) (case 2) and more than 1 DD (case 5) are shown in Figures 1B and F, respectively.

Eyes in group 2 (n = 9) showed a partial (Fig 1J total (Fig 1N highly reflective line in the area over the PEDs at the level of the RPE.

Age and fellow eye

The average age was 60.1 years in group 1 and 70.2 years in group 2 (p = 0.1141). Only one of 15 patients in group 1 (6.7%) had macular degeneration in the fellow eye, whereas five of nine patients (55.6%) in group 2 had it (p= 0.0074).

Visual acuity

The mean visual acuity (logarithm of minimum angle of resolution (logMAR)) at the initial visit was significantly better in the eyes in group 1 (VA = 0.169) than in group 2 (VA = 0.649; p = 0.0051). This difference was maintained at their most recent VA measurement (VA = 0.117 in group 1 v 0.844 in group 2; p = 0.0008). The differences tended to increase after successive follow ups.

Size of PEDs

At the initial visit, the mean size of the PEDs was significantly larger in group 2 (1.556 DD) than in group 1 (0.860 DD) (p = 0.0284).

FAG and ICG

PEDs were also classified by FAG and/or ICG by a modified method of Yuzawa and coworkers.⁵ The PEDs were divided into three types by FAG; the classic hyperfluorescence of the lesion (Fig 1C) in 13 patients, irregular fluorescence (Fig 1G, K) in six patients, and hypofluorescence (Fig 1O) in three patients (Table 1).

All patients in group 1 who had FAG showed the classic hyperfluorescence, except case 9, and conversely, all patients in group 2 had irregular or hypofluorescence. The difference in the distribution of the FAG pattern was significant (p <0.0001).

The PEDs could also be divided into three types by ICG examination; the hyperfluorescence type (Fig 1D) in 12 patients, the irregular hypofluorescence type (Fig 1H and L) in five patients, and no fluorescence (Fig 1P) type in four patients. Eleven of 12 patients (91.7%) in group 1 showed hyperfluorescence, and only one patient (11.1%) in group 2 showed hyperfluorescence (p = 0.0002).

DISCUSSION

We compared the cross sectional structure of the OCT determined two types of PEDs with the pattern from FAG and/or ICG and evaluated the underlying condition of the PEDs. The eyes in group 2 had significantly poorer visual acuity and larger PEDs than eyes in group 1. Patients in group 2 were older than those in group 1 although the difference was not significant. These results agree well with the findings previously reported for PEDs by Klein and coworkers⁶ that PEDs in older patients tended to be larger and were associated with diffuse degenerative changes in the posterior pole. Yuzawa and coworkers also reported RPE atrophy after the absorption of turbid fluid within the subpigment epithelial space. The corresponding lesions showed irregular fluorescence by FAG,⁵ and this may account for the poor vision in group 2.

An irregular, or absence of, fluorescence pattern by ICG may be due to the accumulation of materials on the choroid, inner collagenous layer, or subpigment epithelial space.⁵ Laboratory data have also suggested a disturbance of Bruch's membranes caused by the accumulation of debris such as neutral lipids or phospholipids.² These lesions are then recognised as drusen clinically. The thickening may participate not only in the development of PEDs, but also in the development of CNV.⁷ The highly reflective line at the level of RPE may indicate an abnormal state of Bruch's membrane produced by the accumulation of materials at the superficial layer of Bruch's membrane.

The non-invasive and non-contact diagnostic technique of OCT can provide important information on the structure of PEDs. If a highly reflective line is detected under the PEDs, our findings suggest that there may be an increase in the resistance of Bruch's membrane to fluid flow and necessitate a more frequent follow up of these patients.