We report electrophysiological findings in a patient that has degenerative myopia. The visual acuity of a 48 years old male patient was counting fingers from 0.1 with refraction (-11.00, -1.00 x115) in the right eye and 0.6 with refraction (-5.00, -1.50 x35) in the left eye. Bilateral anterior segment examination was normal however; on the fundus examination, there were atrophic scar area in the macula and pigmented degenerative areas in the inferior on the right, while there were chorioretinal atrophy and degenerative areas in the peripheric retina on the left. Normal latency response was obtained in VEP. In the right eye, a low amplitude and long latency response was obtained with the 120' pattern, but no response was obtained with the other patterns. In the left eye, there was a response to patterns shrinking to 15', the p100 wave was minimally low for age, and its latency was within normal limits. 7' pattern could not be answered. With ERG, bilateral rod b wave responses were subnormal for age, and cone b wave responses were low. Oscillatory responses were obtained bilaterally low.

Myopia as a refractive disorder is quite common in many parts of the world, with a prevalence of approximately 80% [1,2]. Its frequency is increasing fast with growing screen exposure and close fixation, all over the world. High myopia is one of the important causes of vision loss, especially in the young population and it is described as refractive error of minimum -6.00 D spherical or an axial length which is greater than 26.5 mm [3,4]. Myopia is a refractive problem that can be easily resolved with optical correction; however degenerative myopia is considered as a disease in which changes occur in the entire eye, that may be concluded in damaged retinal activity and conclusively modify the visual performance. [5,6,7]. Degenerative myopia or pathological myopia is characterized by high axial myopia accompanied by characteristic pathological changes such as chorioretinal atrophy which can be diffuse or patchy, posterior staphyloma, lacquer cracks. Also, choroidal neovascular membrane, Fuchs spots, macular hole and foveoschisis may also evolve [8,9]. These pathologic findings usually bring about accelerated vision loss [10]. Visual evoked potential (VEP) and electroretinogram (ERG) are important diagnostic tools that assist the clinician in the evaluation of visual functions. With this case report, the effect of degenerative myopia on optic nerve and retinal functions was emphasized with visual evoked potential (VEP) and flash electroretinogram (ERG). 

In this case report; the best corrected visual acuity with Snellen chart, anterior and posterior segment examination with slit lamp, visual evoked potential (VEP) and flash electroretinogram (ERG) examinations were examined.

The visual acuity of a 48 years old male patient was counting fingers from 0.1 with refraction (-11.00, -1.00 x115) in the right eye and 0.6 with refraction (-5.00, -1.50 x35) in the left eye. Bilateral anterior segment examination was found normal in the slit lamp examination. On the fundus examination, there were atrophic scar area in the macula and pigmented degenerative areas in the inferior on the right eye, while there were chorioretinal atrophy and degenerative areas in the peripheric retina on the left eye.

Normal latency response was obtained in VEP. In the right eye, a low amplitude and long latency response was obtained with the 120' pattern, but no response was obtained with the other patterns. In the left eye; there was a response to patterns shrinking to 15', where the p100 wave was minimally low for age, and its latency was within normal limits. 7' pattern could not be answered. Bilateral p wave latencies were symmetrical and within normal limits, but p amplitude was low on the right 

With ERG, bilateral rod b wave responses were subnormal for age and cone b wave responses were low. Oscillatory responses were obtained bilaterally low.

Figure 1A: Pattern VEP of the right eye, B. Pattern VEP of the left eye

Figure 2: ERG of the right and left eye

EP is a sensitive test used to evaluate optic nerve function and is a helpful test for the clinician in the diagnosis of optic nerve diseases such as demyelinating diseases, optic neuritis and optic neuropathy. It is also used in the evaluation of visual function by transmitting the ganglion cell response generated by flash or pattern stimulation to the occipital cortex. While VEP wave responses are generally not affected in refractive myopia; in patients with degenerative myopia, there may be a decrease in the amplitude of the positive wave and a prolongation of the latency period in VEP due to the involvement of optic nerve and ganglion cells [11,12,13,14]. In our case, with the decrease in visual acuity; in VEP, the latency time was normal; in pattern VEP, the amplitude of the p100 wave obtained with a 120' pattern was low and the latency period was long in the right eye; no response was obtained with other patterns. In the left eye, there was a response to patterns that decreased by 15’, the amplitude of the p100 wave was minimally low for age, and the latency period was within normal limits. 7' pattern could not be answered.

ERG is a documentation of a common electrical response produced by neural and non-neuronal cells within the retina. In patients with retinal degeneration and affected retinal nerve fiber layer, ERG responses are also impaired [14]. In our case, too; with ERG, bilateral rod b wave responses were subnormal for age and cone b wave responses were low. Oscillatory responses were obtained bilaterally low. 

Visual acuity as well as visual quality and visual function are affected in degenerative myopia. Depending on the degeneration, VEP responses starting from retinal ganglion cells and ERG wave responses showing retinal functions are also affected.