A 21 year old white male comes to you complaining that his vision in his right eye has been steadily getting worse over the last couple of years. He had a refraction a couple of years ago and felt that the vision was OK, but not quite perfect when compared to the left eye. His history is negative for eye disease, trauma or surgery. He suffers from hay fever for which he takes a Claritin tablet, but uses no other medications. He has worn glasses since age 10 and has not worn contact lenses.
His visual acuity is OD 20/40 and OS 20/20 with his current spectacles; OD 20/800 and OS 20/200 without spectacles. Your refraction is; OD -3.50 DS -3.00DC x 145, 20/40; OS -0.75DS -1.75DC x 135, 20/20-. Pinhole improved OD to 20/25. Keratometry: ~OD 49.00D@135, 53.25D@45 but very difficult to measure due to Grade 4 distortion. OS 45.00D@10 & 46.00D@100, Grade 1 distortion.
Guiding Questions
1. What is the refractive diagnosis? Be prepared to explain myopia, hyperopia and astigmatism.
2. What proportion of total refractive power is contributed by the cornea? Explain.
3. What is the principle of operation for the keratometer? What is the significance of the distorted image and what abnormalities could produce distortion?
4. What is the significance of the pinhole result?
5. What is hay fever? How does Claritin work?
6. Is there any significance to the fact that he has hay fever? (you may not be able to answer this until later in the case)