Author: Ameen Marashi, MD
Documenting the age along with visual loss, including the extent, duration, metamorphopsia, scotoma, and macular photo-stress, is essential , as the patient may need time to recover central vision after bright light exposure.
Medical history of systemic disease is important to rule out pseudoxanthoma elasticum , myotonic dystrophy , and maternally inherited diabetes and deafness .
It is crucial to investigate family history to document the relatives that are suffering from pattern dystrophy as most of the cases of pattern dystrophy are autosomal dominant with mutation of PRPH2 genotype; however, the relative's fundus exam may have a different clinical presentation of pattern dystrophy .
A list of ocular examination should set
1) Best-corrected visual acuity (BCVA) for near and far is an essential step that can be performed by a trained optometrist or certified ophthalmologist to document the visual impairment.
2) A slit-lamp examination done with a thorough exam of clarity and regularity of the cornea and to rule out any conjunctival abnormality such injection of conjunctival vessels should be documented, and any other inflammations of the conjunctiva or eyelids documented, along with iris exam and to rule out narrow-angle along with crystalline lens exam to rule out cataract or intraocular lens (IOL) to document the position and clarity of the posterior capsule.
3) Intra Ocular Pressure (IOP) documentation; in cases of increased IOP, then gonioscopy is necessary. Note when high IOP spotted a corrected IOP documented after central corneal thickness measurement.
4) Bilateral dilated fundus exam is essential as pattern dystrophy is bilateral disease and most likely symmetrical, but sometimes each eye can have a different form of pattern dystrophy; however, fundus exam should include a detailed examination of the optic disc, macula, posterior pole, a mid-peripheral and peripheral retinal exam with specialized indirect wide-field lenses using slit-lamp biomicroscopy or indirect ophthalmoscopy to document the pattern dystrophy category:
Adult-onset Foveomacular Vitelliform Dystrophy, which presents grayish-yellow macular similar in shape (oval or round) to best disease but smaller in size that can reach up to one third or one-half diameter of the optic disc with central pigmentation .
Butterfly-shaped Pigment Dystrophy, which appears as central macular yellow, white, or black-pigmented material which configures in the shape of 3 or 5 arms that may have the shape of butterfly wings shape. However, it can be accompanied by retinal flecks or drusen-like material peripheral to central dystrophy .
Reticular Dystrophy features hyperpigmentation in the form of the fishing net with knots with one disc diameter, but in the early stages of the disease, the periphery is spared, but then it gets involved.  However, in late stages, the hyperpigmentation bleaches, leaving behind white RPE atrophic white lesions .
Multifocal Pattern Dystrophy Simulating Stargardt's Disease appears as yellow to white flecks similar to Stargardt's disease scattered in the posterior pole, including the macula, nasal and temporal to the optic disc and around the retinal vessels sometimes it accompanied with atrophic macular changes .
Central Areolar Choroidal Dystrophy, which appears in early stages as depigmented RPE mottling as the disease progresses to central geographic RPE atrophy, even choroidal vessels may appear in yellow-white color.
It helps to document the presence and progression of pattern dystrophy along with different pathological macular changes such as subretinal hemorrhage, fibrosis, and atrophy in cases complicated with choroidal neovascularization.
Optical Coherence Tomography (OCT)
Adult-onset Foveomacular Vitelliform Dystrophy OCT cross-sections show homogenous subretinal material between RPE and intact ellipsoid .
OCT may show thinning of retina corresponding to visual loss, which accompanied with the absorption of vitelliform material; however, in advanced cases, a full-thickness macular hole may develop.
In cases complicated with choroidal neovascularization, OCT shows a subretinal hyperreflective amorphous mass with subretinal fluid and disruption of the ellipsoid zone with or without macular edema and intraretinal cysts.
OCTa can clearly show the presence of choroidal neovascularization, which is more prominent in the outer retina slab than choriocapillaris slab; however, OCTa is essential for cases suspected to be complicated with choroidal neovascularization were not clearly shown by FFA and OCT.
Central Areolar Choroidal Dystrophy OCT cross-sections show atrophic changes of RPE and loss of ellipsoid zone and thinning of outer retinal layers, which are located adjacent to a preserved retinal area of RPE and outer retinal tissue.
Fundus Fluorescein Angiography (FFA)
Adult-onset Foveomacular Vitelliform Dystrophy shows the area of hypofluorescence surrounded by an area of hyperfluorescence, which increases in intensity in late stages.
The FFA is very useful to rule out the presence of subretinal choroidal neovascularization as well as delineated hyperfluorescence in early stages, which will have a fuzzy border at the late stages.
Butterfly-shaped Pigment Dystrophy shows the area of hypofluorescence of the Butterfly-shaped lesion at the macula, while flecks block fluorescence .
Reticular Dystrophy features hypofluorescence of the pigmented bands; however, the surrounding retina appears hyperfluorescence without any leakage.
Flecks in multifocal Pattern Dystrophy Simulating Stargardt's Disease appear hyperfluorescence in all phases without any sign of dark choroid.
Central Areolar Choroidal Dystrophy appears as a window defect on FFA simulating central geographic atrophy in age-related macular degeneration.
Note that the physician should obtain signed consent explaining the rare complications of FFA, including death 1/200000, and FFA facility should have an emergency plan in situ.
Fundus Autofluorescence (FAF)
May show increased FAF adjacent to reduced FAF depending on RPE metabolic activity. For example, in adult-onset foveomacular vitelliform dystrophy, there would be increased autofluorescence in areas of vitelliform deposits in early stages and decreased autofluorescence in areas of atrophy in late stages. In contrast, spoke-like, wheel-like or reticular changes in FAF in other types of pattern dystrophy. However, in Multifocal Pattern Dystrophy Simulating Stargardt's Disease, the FAF will show decreased autofluorescence surrounded with increased autofluorescence at the areas of yellow flecks .
Electroretinography are ranged from normal and subnormal.
Managing patients with pattern dystrophy
- Patients complicated with choroidal neovascularization are treated with intravitreal VEGF blockade agents that can be used monthly until stabilization of vision and resolving subretinal fluid, which may not always resolve completely.
- Patients should be advised to wear dark glasses in bright light exposure and try not to use bright led lighting at home to avoid macular photo-stress to improve quality of life.
Follow up and prognosis
- The risk of developing choroidal neovascularization is about 18% during the natural course of the disease .
-Partial or complete reabsorption of the vitelliform lesion is common, and it is associated with a reduction of vision .
-Patients may have a reduction of vision in the fourth and fifth decade to 20/100 or 20/200 but remain stable throughout seventy and eighty .
-Patients with geographic atrophy suffer from reduced central visual acuity and may benefit from using low vision aid.
-Patients complicated with macular hole have a poor prognosis even after pars plana vitrectomy.
- The patient should report any visual acuity changes such as metamorphopsia, and this can be done by the patient to perform the Amsler test regularly.
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These guidelines were reviewed and updated in January 2021