4.1Case 1

A 19-year-old male has a progressive refractive error in both eyes. He is complaining of rapid progression of blurring of vision. He is also intolerant to contact lenses. His manifest refraction (MR) is (Table 4.1.1):

His old correction (3 months ago) is (Table 4.1.2):

Slitlamp examination shows clear cornea with no stress lines. Other ocular findings are within normal limits.

Corneal Topography reveals KC in both eyes, more advanced in the left eye.

For educational purposes, the left eye will be studied. Figure 4.1.1 shows corneal topography of the left eye.

4.1.1Step 1: Analyzing Step

1. The patient is 19 years old, so he is supposed to be in the age of progression.

2.His refractive error is progressing during short periods, this is clear from his complaint and by comparing his old glasses (Table 4.1.2) with his recent MR (Table 4.1.1).

3. The axes of the old glasses, manifest refraction, and topography are different. This means a skew in astigmatism which is usually consistent with KC.

4. UCVA is primarily good and there is three lines difference between UCVA and BSCVA, this usually carries a good prognosis.

5. Corneal topography of the left eye is taken as an example:

(a)Figure 4.1.1 shows the main four maps, it is obviously KC.

(b)Figure 4.1.2 is the anterior sagittal curvature map. The topographical pattern is AB/SRAX; it is AB because the inferior segment of the bow tie is larger than the superior segment and the refractive power of the inferior segment is higher than the superior by more than 1.5 dpt; it is SRAX because of the more than 22° of skew between the axes of the two segments. Since K-readings are not high, the shape of the cone is clear and there is no need for color modification (see Fig. 4.1.3).

6.According to Krumeich classification, this case is grade 1 KC, and according to the author’s classification, it is pattern 2.

4.1.2Step 2: Management Suggestions

Table 4.1.3 summarizes patient data and the corresponding individual suggestion(s) for treatment, and presents a final summary of the best management.

4.1.3Step 3: Discussion

1. It is a mild case of KC which does not need aggressive procedures to be managed with.

2. As the case is progressive, the cornea should be cross-linked.

3. As the refractive error is small (< −6 dpt) and the thinnest location is >450 m, TG PRK is a good choice. Personally, I do not advise ICRs because of small

K-readings and refractive error; using ICRs in such a

case carries the possibility of over correction. I do advise CXL with or without TG PRK.

Figure 4.1.4 shows a similar case treated with CxL and TG PRK. A (on the left) is the preoperative curvature map, B (in the middle) is the postoperative curvature map, and C (on the right) is the difference map that shows the correction achieved by the TG PRK. Note the homogenous shape of the cornea after the operation that led to improvement in quality and quantity of vision.