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Look for lacquer cracks in high myopes for early warning of retinal hemorrhage
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Choroidal neovascular membranes (CNVMs) develop whenever there is a compromise to the outer retinal complex. The retinal pigment epithelium, the photoreceptors, Bruch’s membrane and the choriocapillaris function as a unit; any abnormality affecting one layer interferes with the function of one or more other structures.
If a break develops in Bruch’s membrane, newly sprouted choroidal vessels ingress into the subretinal pigment epithelial or neurosensory retinal space. Being immature, these vessels may leak fluid, lipid or blood and — depending on their location — may cause severe vision loss.
Many retinal disorders result in choroidal neovascular membrane. Careful examination of the posterior pole and an understanding of risk factors will help to identify those patients with impending problems.
History of blur with distortion
| Conditions commonly associated with Choroidal Neovascular Membrane | |
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A 44-year-old myopic woman presented with a 2-week history of near blur with distortion in her left eye. Her medical and ocular histories were negative. Visual acuity was 20/40 OS, and she recognized distortion on the Amsler grid test. Fundus examination and subsequent fundus fluorescein angiography revealed an area of leakage superior to the center of the fovea, just outside the foveal avascular zone (FAZ).
The overall fundus appearance was tessellated, and there were multiple fine breaks in Bruch’s membrane in the posterior pole of both eyes. A diagnosis of lacquer cracks with CNVM was made and the patient was scheduled for focal argon green laser photocoagulation.
The patient was eligible for treatment because she had a choroidal neovascular membrane leaking into the macular area that was far enough removed from the center of the FAZ. The lesion appeared completely obliterated, and follow-up fluorescein angiography confirmed this finding. The dysmorphopsia resolved with absorption of subretinal fluid, and the patient was left with a small residual scotoma. She was educated as to the signs and symptoms of recurrent CNVM and was scheduled for follow-up examinations. She has demonstrated no further evidence or recurrence of the CNVM, and her vision remains stable at 20/40.
Lacquer cracks in high myopes
---Highly myopic right eye: This fundus photograph shows tessellation, myopic crescent and linear lesions characteristic of lacquer cracks. Lacquer cracks are breaks in Bruch’s membrane frequently observed in the posterior pole of a highly myopic eye. These distinctive fundus changes are actually quite common in axial myopia and may augur hemorrhage into the macular area, either from mechanical causes or from choroidal neovascularization.
Lacquer cracks are often mistaken for angioid streaks; however, they differ in appearance, and they are not associated with any underlying systemic disease. However, the condition is often associated with pathologic or progressive myopia and often occurs concurrently with posterior staphyloma.
Degenerative fundus changes probably result from distention of the globe, leading to stretching of the underlying choroidal and scleral tissue. This tissue alteration can result in changes to the retinal and choroidal vessels, thus leading to hemorrhage. Fuch’s spot, subretinal hemorrhage or exudative detachment of the retinal pigment epithelium or neurosensory retina results from serosanguinous leakage into the subretinal space from CNVM.
This characteristic neovascular lesion is associated with lacquer cracks or pathological changes in Bruch’s membrane. Fissures develop, and accompanying changes in the choriocapillaris complex can allow communication between the underlying choroid and the subretinal space, thus the possibility for CNVM genesis.
Lacquer cracks are seen in almost 5% of highly myopic eyes, and the reported incidence of CNVM associated with these lesions is as high as 10%. Conversely, lacquer cracks are found in more than 80% of myopic eyes with CNVM. The incidence is probably higher, because both the cracks and the neovascularization may go undetected in early stages without the aid of fluorescein angiography, especially if the vision is unaffected.
Causes of the cracks
---Lacquer crack with CNVM: This is the left eye of a 40-year-old woman with visual acuity of 20/70. Late-phase fluorescein angiogram reveals hyperfluorescence characteristic of CNVM and subretinal leakage. Two plausible theories explain the etiopathogenesis of lacquer cracks. Early studies pointed to sclerosis of the finer choroidal vessels as the root cause for the cracks. More recently, it has been postulated that the stretching of the retina and choroid in the staphylomatous globe causes lacquer cracks. Continued growth of the globe exceeds the elastic resistance of Bruch’s membrane, and a linear rent becomes obvious. There also seems to be some association with tilted disc syndrome, another condition associated with high myopia and ectasia of the posterior globe.
Visual function in pathologic myopia and, therefore, in patients with lacquer cracks is often reduced. An anatomically deformed globe is a constant finding, and the visual field and color discrimination can also be impaired. The clinical appearance of lacquer cracks is somewhat unique, and the fine, irregular, pale yellow or white lines radiating in a stellate or reticular pattern in the posterior pole are quite distinctive. The lesions may be single or branching, and they tend to crisscross with one another.
---After treatment: This is the same patient after focal laser treatment for CNVM. The mid-phase of the fluorescein angiogram shows hypofluorescence, indicating destruction of the CNVM. Lacquer cracks are almost always associated with a temporal crescent of the optic nerve head, and the lesions tend to be continuous with the crescent in many cases. Most lacquer cracks traverse the macula and lie in the deeper layers of the retina. The Bruch’s membrane-choriocapillaris complex is affected, but the overlying neurosensory retina, the inner retina and the retinal vessels remain unaffected. The fundus is often tessellated and may appear pale in the posterior polar region compared to other regions.
Choroidal hemorrhage
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Clinical Presentation | |
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Choroidal hemorrhage in the absence of CNVM is common. The hemorrhage is dense in appearance and often resolves spontaneously, but could permanently alter the retinal pigment epithelium or the photoreceptors. The hemorrhages may occur in younger age groups, tend to be deep in the retina and, because of their characteristic appearance, are sometimes referred to as coin lesions.
The hemorrhages occur along the linear aspect of the lesion, and the prognosis for good vision remains. Chorioretinal atrophy eventually develops in the posterior pole, and the lacquer cracks become enfolded into these larger areas. As is often the case in pathologic myopia, CNVM formation can occur and may lead to significant vision loss.
Fundus fluorescein angiography findings reveal early pseudofluorescence and hyperfluorescence due to abnormal transmission of atrophic retinal pigment epithelium and the choriocapillaris. Fluorescence increases slightly throughout the transit, and a faint hyperfluorescence remains in the late stage of the angiogram, probably due to scleral staining. A CNVM will elicit a characteristic irregular, lacy hyperfluorescence in the early phase with increased staining and fuzzy fluorescence in the late phase of the transit.
Differential diagnosis
---Four-year-old with anisometropia: This fundus photo shows lacquer cracks and hemorrhage in the absence of CNVM in the right eye of an anisometropic (–6 D in the right eye, –2 D in the left eye) patient. The visual acuity declined to 20/40 (from 20/20), and there is a permanent scotoma, presumably resulting from the retinal pigment epithelium and photoreceptor damage. The differential diagnosis of lacquer cracks includes traumatic rupture of Bruch’s membrane, an event that usually follows contusive trauma to the globe. The lesion is linear or crescent-shaped and often follows the contour of the optic disc. Additional consideration should be given to angioid streaks, linear lesions in Bruch’s membrane that have a high degree of correlation with systemic disease. However, angioid streaks radiate from the optic nerve head in all directions and range in color from gray to brown to red.
Risk factors for lacquer cracks should be considered, and these include high myopia, usually greater than 6 D, in association with posterior staphyloma.
Management of lacquer cracks should involve a comprehensive ocular examination including fundus fluorescein angiography, especially if CNVM is suspected based on clinical findings or on patient symptoms, including dysmorphopsia. Self-assessment with the home Amsler grid should be recommended if there is an index of suspicion for CNVM.
New onset or recurrence of dysmorphopsia should alert the patient and the clinician to the possibility of ocular morbidity and visual loss. If CNVM is present, focal argon laser photocoagulation may be indicated depending on the location and angiographic findings.
Lacquer cracks are typical clinical findings in a highly myopic fundus and should alert the clinician to the possibility of retinal hemorrhage with or without CNVM. Patients with high axial myopia warrant careful examination and regular ocular examination to rule out fundus changes that may augur the onset of choroidal neovascular membrane. If CNVM is suspected based on physical examination or a report of dysmorphopsia, then a fluorescein angiogram should be obtained to determine if a treatable lesion is present.
For Your Information:
Anthony A. Cavallerano, OD, is a professor of optometry at New England College of Optometry and is a member of the Primary Care Optometry News Editorial Board. He may be contacted at the New England College of Optometry, 424 Beacon St., Boston, MA 02115; (617) 236-6320; fax: (617) 424-9202; e-mail: tonycav@earthlink.net. Dr. Cavallerano has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned. All figures published with permission: Cavallerano AA, Gutner RK, Oshinskie LJ. Atlas of Macular Disorders: An Illustrated Guide. Boston: Butterworth-Heinemann, 1997.