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4.3Case 3
A 20-year-old male has bilateral KC. As he says, the refractive error is still progressing slowly within 6 months intervals, he is happy with his glasses, but he is worried about his disease.
His MR is (Table 4.3.1):
Table 4.3.1 Manifest refraction |
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Eye |
Sphere |
Cylinder |
Axis |
UCVA |
BSVCA |
OD |
0 |
−2.5 |
45 |
0.6 |
1.0 |
OS |
−1.5 |
−3.5 |
130 |
0.3 |
1.0 |
His old correction (6 months ago) is (Table 4.3.2):
Table 4.3.2 Old refraction
Eye |
Sphere |
Cylinder |
Axis |
OD |
0 |
−1.25 |
45 |
OS |
−0.75 |
−2.5 |
120 |
Slitlamp examination shows clear cornea with no stress lines. Other ocular examination is within normal limits.
Corneal Topography reveals KC in both eyes more advanced in the left eye.
Figures 4.3.1 and 4.3.2 are the right eye topography; Figs. 4.3.3 and 4.3.4 are the left eye topography.
4.3.1Step 1: Analyzing Step
1. The patient is 20 years old, so he is still in the progressing age.
2.His refractive error is progressing during reasonable periods (6 months); this is clear from his complaint and by comparing his old glasses (Table 4.3.2) with his recent MR (Table 4.3.1).
Fig. 4.3.1 Corneal topography of the right eye: mild KC
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Fig. 4.3.2 Anterior curvature map of the right eye. The curvature pattern is SB/ SRAX. According to author’s classification, it is pattern 4
Fig. 4.3.3 Corneal topography of the left eye: mild KC
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Fig. 4.3.4 Anterior curvature map of the left eye. The curvature pattern is SB/SRAX. According to author’s classification, it is pattern 4
3. The axes of the old glasses, manifest refraction, and topography are quite similar giving an impression of a mild case of KC.
4. UCVA is primarily good and there is at least four lines difference between UCVA and BSCVA, this carries a good prognosis.
5. BSCVA is 10/10 which also carries a good prognosis and an impression of a mild case.
6. Corneal topography:
The topographical pattern of both eyes is SB/SRAX since there is almost no difference in K-readings and size between the bowtie segments but there is a significant skew between their axes (more obvious in the right eye topography).
7. According to Krumeich, it is grade I KC since K-readings are < 48 dpt and corneal thickness at the thinnest location is > 500 m. According to the author’s classification, it is pattern 4.
4.3.2Step 2: Management Suggestions
Table 4.3.3 summarizes patient data and the corresponding individual suggestion(s) for treatment, and presents a final summary of the best management.
Table 4.3.3 Management suggestions |
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Factors |
Patient data |
Suggested treatment |
Transparency and |
Transparent |
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stress lines |
with no stress |
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|
lines |
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Age |
20 |
|
Progression |
Yes |
CxL |
CL tolerance |
Not tried before |
One choice |
Refractive error |
−1.25 dpt R.E |
CxL and PRK |
(S.E) |
−3.25 dpt L.E |
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BSCVA Vs UCVA |
Very good |
CxL and PRK or ICRs |
K-max |
46 dpt R.E |
CxL and PRK or ICRs |
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47 dpt L.E |
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Corneal thickness |
521 m R.E |
CxL and PRK or ICRs |
at thinnest location |
522 m L.E |
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Sex |
Male |
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Management |
CXL to stop the progression and to |
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summary |
prepare the cornea for PRK |
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4.3.3Step 3: Discussion Step
It is a typical case of mild KC in a young patient. Since the case is progressive, it is recommended to cross-link the cornea. The conditions for CxL are ideal in this case; corneal thickness at the thinnest
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location is more than enough even if TG PRK is within the plan, especially that the refractive error is small (<−4 dpt S.E) and can be corrected within the allowed 40–50 m. Nevertheless, the BSCVA is optimal which means that there are small amount of aberrations and, therefore, the results will be promising.
On the other hand, ICRs are also another option, especially if only one segment is used because the cornea is not very irregular and both astigmatism and K-readings are not too high (<48 dpt).
Personally, I prefer CxL with or without TG PRK since the case is still mild and there is no need to expose the cornea to more invasive procedures.