Blurry Driver Steers Into Exam Lane
Answers to Diagnostic Quiz, April 15th, 2004
Discussion
This patient has a posterior staphyloma secondary to pathological myopia. The appearance in the photo is the result of progressive thinning of the sclera resulting in a bulge or ectasia causing the change in fundus topography.1
Useful tests for this case include:
Hirschberg test for detecting ocular alignment.
Worth four-dot test to help determine the level of suppressive adaptation and possibly the presence of tropia with normal retinal correspondence (NRC) or anomolous retinal correspondence (ARC). Bagolini striated lenses could also have been used or substituted for the same.
Visuoscopy to determine if steady or unsteady central fixation was present.
Amsler grid to potentially identify a maculopathy.
Laser interferometry for evaluation of the integrity of the macular photoreceptors.
Corneal topography to rule out keratoconus that might be beyond the measuring capabilities of the standard keratometer.
Photostress test and Watzke-Allen test for assessing the functionality of the macula.
A-scan and B-scan to measure the length of the eye.
Degenerative myopia results from axial elongation of the globe and can be seen by noted changes in the posterior pole and ora-equatorial areas.2 Mechanical and physiological factors can potentially lead to sight-threatening abnormalities.3
A posterior staphyloma is one of the most common findings in pathological myopia. A staphyloma results when progressive thinning of the sclera occurs.1 This thinning is due to collagen bundle thinning and deformation.1
There are five types of primary posterior staphylomas:4
Type 1: posterior pole
Type 2: macular
Type 3: peripapillary
Type 4: fundus, nasal to the disc
Type 5: fundus, area below the disc
Compound staphylomas consist of any combination of the above.
Posterior staphylomas carry poor visual prognosis, with over 50% of eyes in patients over age 60 considered legally blind.1
Management of degenerative myopia warrants constant monitoring as the patient ages.1 Cases involving lacquer cracks of the Bruchs membrane should be monitored for the presence or formation of subretinal neovascularization. The incidence of Fuchs spot, peripheral retinal degenerative changes, glaucoma and vitreous traction decreases with age. Due to the alteration of the retinal and choroidal structure, protective eyewear should be recommend to prevent traumatic injury.
1. Alexander LJ. Exudative and non-exudative macular disorders. In: Alexander LJ. Primary Care of the Posterior Segment, 3rd ed. New York: McGraw-Hill, 2002:75-208.
2. Curtin BJ. Physiologic vs pathologic myopia: genetics vs environment. Ophthalmology 1979 May;86(5):681-91.
3. Hoffman DJ, Heath DA. Staphyloma and other risk factors in axial myopia. J Am Optom Assoc 1987 Nov;58(11):907-13.
4. Curtin BJ. The posterior staphyloma of pathologic myopia. Trans Am Ophthalmol Soc 1977;75:67-86.
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