Metamorphopsia is a disorder of the eye which is characterized by the distortion in the vision of the eye. In this condition, a grid constituting straight line appears wavy to the observer; in some cases, some parts of the grid may appear blank as well. Metamorphopsia is commonly observed in individuals suffering from macular disorders.
What is Metamorphopsia?
When individuals are unable to perceive the visual images clearly, commonly accompanied by distorted shape and sizes of the objects, then such a condition is called Metamorphopsia. The peripheral limits of the eye which are responsible for the characterization of hallucinations get affected in Metamorphopsia. The cerebral cortex gets irritated due to two kinds of problems in the eye which are refractive errors and pathological alterations of the retinal apparatus within the eye.
The retinal errors occur when the light entering the eyes is not able to directly focus on the retina. In case of Metamorphopsia, the amount of optical power required to observe a clear image is not at par with the distance of the eye from the object, resulting in distorted image. The distortion of vision can be either macropsia or micropsia. In case of macropsia, the shape of the object in vision appears to be distorted, whereas in case of micropsia, the size of the object which is perceived is not correct, it can appear either larger or smaller.
In case of pathological changes happening in the retinal receptor apparatus, the optic nerve ending present at the retina get inflamed and sometimes may also get scarred, resulting into distorted vision.
Causes of Metamorphopsia
The causative factors behind Metamorphopsia are:
- Macular Degeneration Causing Metamorphopsia: Macular degeneration is the damage and erosion of the central part of the retina called the macula, resulting in impairment of the central vision. This condition never results in total blindness but cause severe hindrance in performing daily activities like reading, driving, etc. It is more of an age related disorder, which usually affects individuals over the age of fifty years.
- Migraine: Migraine is a neurological condition in which the blood vessels present within the brain tend to dilate and release hormones that cause the activation of pain receptions. This further cause recurrent headaches, nausea and vomiting. In many cases, migraine can also attribute to the onset of visual problems like Metamorphopsia. Metamorphopsia is observed quite commonly in migraine affected individuals, even though the Metamorphopsia symptoms are usually temporary in these cases.
- Macular Holes Leading to Metamorphopsia: Macula contributes extensively to visual tasks like driving, reading and focusing on details. In case of macular hole, the macula breaks and tampers the central vision of the eye by causing blurred and distorted vision and dark spot in the central area of vision. It is another condition which is age dependent and commonly affects individuals belonging to the age group of sixty years and above.
- Retinal Detachment: Retinal detachment is an urgent medical situation in which the cells of the retina get separated from the underlying layer of blood vessels that provide oxygen and nutrition. The condition brings along a severe risk of permanent vision loss and is characterized by the sudden occurrence of flashes and floaters, along with significant reduction in vision. It needs to be kept in mind that risk of permanent blindness increases with increase in the period of detachment.
Symptoms of Metamorphopsia
The characteristic symptoms that identify Metamorphopsia are:
- Curly or wavy appearance of the straight lines
- Curved appearance of the flat surfaces when focused upon
- When observing a grid of straight lines, they may appear either blank or wavy.
Pathophysiology of Metamorphopsia
The main cause behind the occurrence of Metamorphopsia is the alteration in the photoreceptor levels, due to the thickening of the inner nuclear layer and the layer of ganglionic cells. This further impairs the proper functioning of the synaptic junctions, thus leading to decreased sensitivity of the photoreceptors contributing to Metamorphopsia.
Risk Factors of Metamorphopsia
The common risk factors that pose a threat for Metamorphopsia are:
- Ocular histoplasmosis syndrome
- Antiangiogenic drugs
- Ruptured choroid.
Treatment of Metamorphopsia
The treatment for Metamorphopsia focuses on treating the causative factor behind the condition. The treatment is done as follows:
- Laser Photocoagulation to Treat Metamorphopsia: When the cause behind Metamorphopsia is macular degeneration, then laser photocoagulation is opted in which a laser beam is used to destroy the abnormal retinal macula cells.
- Retinal Surgery for Correcting Metamorphopsia: When suffering from retinal detachment, then surgical treatment is given the top priority. Some such surgeries are vitrectomy, pneumatic retinoplexy and scleral buckling.
- Cryotherapy: In case of retinal tears and macular holes, cryotherapy is performed to prevent retinal detachment, by forming an adhesive scar and sealing the macular cells.
- Medications: When migraine causes Metamorphopsia, then pain medications like NSAIDs and acetaminophens prove to be helpful.
Diagnosis of Metamorphopsia
The identification of Metamorphopsia can be done through few tests:
- Direct Ophthalmoscopy: This technique checks for round and oval lesions in the macula that are quite well defined.
- Slit-Lamp Test to Diagnose Metamorphopsia: This test uses a biomicroscope to check for cystic changes in retina at the macula.
- Ocular Coherence Tomography: This technique is used to detect the changes in retina as well as the surroundings.
- Amsler’s Test: It is a complete ophthalmologic evaluation of the eye. The chart contains white lines with a white dot over a black background. The patient is asked to focus on the white dot and answer a few questions which are related to visibility of the white dot, appearance of the lines, blank areas, blurriness and unusual visible patterns. The answers of the patient help in diagnosis of Metamorphopsia.
Metamorphopsia is a condition which produces faulty vision which is characterized by the appearance of wavy and curvy lines along with blanks when viewing flat surfaces. The condition is usually an outcome of prevailing ailments like migraines, macular holes and degeneration and retinal detachment. The condition can be efficiently diagnosed using ophthalmological analysis and Amsler’s tests. The treatment for Metamorphopsia aims at treating the underlying causative factor. However, if not treated on time, it can lead to vision loss.
- American Academy of Ophthalmology. Metamorphopsia: Causes, Tests, and Treatment. https://www.aao.org/eye-health/diseases/what-is-metamorphopsia
- ScienceDirect. Metamorphopsia. https://www.sciencedirect.com/topics/medicine-and-dentistry/metamorphopsia