Ординатура / Офтальмология / Английские материалы / Step by Step Reading Pentacam Topography (Basics and Case Study Series)_Sinjab_2010

Case Study 121

•The keratoconus indices page (Fig. 5.5I): the curve lines are within the normal range with no deviation before the 6 mm circle. The average is abnormal (1.4). One of the irregularity indices is displayed in red because of the slight irregularity of the cornea. It is

the corneal aberration coefficient factor (ABR), but there is no risk in treating the cornea with ABR less than 2.5.

Let us look at the right eye topography (Fig. 5.5J).

The Qualifying Step

1.In a general look, the sagittal curvature map has a clear irregular pattern oriented as with-the-rule astigmatism. The posterior elevation map shows abnormal numbers. There is nothing suspicious in the thickness map in general but it seems a little bit irregular.

2.Main page analysis reveals that the quality of the capture (QS) is OK. The K-readings in the central 3 mm are normal (43.6, 45.7) and the corneal astigmatism (the algebraic sum of the anterior and posterior astigmatism) is also normal (-1.75 <-6). Q-value at the 6 mm circle of the cornea front is slightly high (-0.62). Corneal thickness at the thinnest location is normal (542) and has normal coordinates with pachy apex. There is also no significant difference in thickness between pachy apex and thinnest location.

3.Studying each map:

•Corneal thickness map (Fig. 5.5K): The shape of this map is slightly irregular with a horizontal displacement of the thinnest location (-0.72 µ red arrow). The

122 Step by Step Reading Pentacam Topography

difference between the lower and upper points of the central 4 mm circle is <30 µ (red circles).

•The sagittal curvature front map (Fig. 5.5L): Asymmetricalbowtie/superiorsteep(AB/SS):asyou see in this picture, the pattern is superior steep and the difference between the upper and lower points at the 4 mm circle is 5.2, which is more than 2.5 dpt. On the other hand, this is a superior hot spot with high K- readings (51.7), which is absolutely abnormal.

•The elevation front map (Fig. 5.5M): Shows irregular shape with tongue-like extension, but the values within the central 4 mm circle are still within the normal range.

•The elevation back (Fig. 5.5N): Shows irregular shape with abnormal values within the central 4 mm circle. There are also some points where the difference between anterior and posterior values is >+5 µ.

•The Keratometric power deviation map (Fig. 5.5O): It is highly irregular with abnormal values in the center (+2.5), which indicates abnormal posterior corneal surface.

•The Topometric map (Fig. 5.5P): Let’s look first at the Asphericity table, if you compare between the mean values at 6, 7 and 8 mm (red arrows), you will see that these values increase towards the periphery, which means that the irregularity is increasing towards the periphery of the cornea, this will be clear when you notice that there is a high difference between horizontal and vertical values in general, and between the four meridians (temp. nasal, etc. yellow arrows).

Case Study 127

Fig.5.5E:The elevation back map. Slightly irregular shape with normal values within the central 4 mm circle. There are also some points where the difference between anterior and posterior values is >+5 µ.