This article is more than 5 years old. Information may no longer be current.
Young boy fails school vision screening
Click Here to Manage Email Alerts
A 7-year-old boy presented to the clinic with his father for an eye examination due to failing a school vision screening. The child was shy but admitted that the board at school was blurry and he had noticed that for quite some time. His school vision form noted visual acuities of 20/40 in each eye. When encouraged during the exam, he was able to see 20/30 OD and 20/30- OS.
Autorefraction, retinoscopy and manifest refraction revealed low hyperopia and astigmatism with no improvement in corrected acuities and no improvement with pinhole. Wet retinoscopy and cycloplegic refraction with 1% cyclopentolate uncovered slightly more hyperopia: +1.50 -0.50 x 018 OD and +2.00 -0.50 x 160 OS; however, visual acuities remained unchanged at 20/30- OD and OS throughout all variations of testing. These tests were repeated three weeks later at a follow-up visit, and the results were unchanged.
The father of the patient denied any patient or family history of ocular disease, surgery or injury, nor any systemic conditions for the patient. The patient was on no medications and his reported ethnicity was half Thai, half Caucasian. He has a twin sister and both were full-term births. The father reported that the patient has a small pigmented birthmark on his inner right thigh, but no other areas of hyper or hypopigmentation are present.
Left eye fundus photo displaying lack of perifoveal hyperpigmentation and no foveal light reflex.
Right eye fundus photo displaying lack of perifoveal hyperpigmentation and no foveal light reflex.
Images: Dohm KD
Cover testing displayed no strabismus, but a small exophoria at distance and near. Extraocular motilities were full in both eyes without nystagmus. Pupils were equally round and responsive to light without afferent or efferent defects. Confrontation fields were full to finger counting in both eyes. Amsler grid testing displayed no scotomas or metamorphopsias in either eye. Noncontact tonometry IOPs were 16 mm Hg OD and 15 mm Hg OS.
Color vision testing was done with the digital ColorDx App from Konan Medical USA. In the general section, the child recognized 16 of 22 correctly in the right eye and 21 of 25 in the left eye. The test is adaptive to correct responses, and no specific deficiency was identified. After the patient had left the clinic, the technician alerted me to the fact that he had run the adult testing variation instead of the child presentation, so only two seconds were given instead of 10 seconds between the different displays. The patient had no issues identifying the red and green charts during refractive testing.
Left eye HD 5 Line Raster Cirrus OCT displaying lack of anatomical foveal pit with continuity of inner retinal layers and mild central thickening.
Right eye HD 5 Line Raster Cirrus OCT (Carl Zeiss Meditec) displaying lack of anatomical foveal pit with continuity of inner retinal layers and mild central thickening.
With stereopsis testing using the RANDOT Stereotests (Stereo Optical Co.), the child displayed no suppression, as he identified the “R + L” in the box, but he was inconsistent with local stereo as he identified the 100 seconds of arc monkey on the bottom row, but missed the cat and rabbit on the two rows above. It was felt that his comprehension and cooperation (testing fatigue) may have been a factor with the results.
The anterior segment of each eye was found to be normal with gross observation and slit lamp biomicroscopy. The posterior segment was examined with binocular indirect ophthalmoscopy and with a high plus lens (90 D) for funduscopy. All structures were identified as normal except one particular region in each eye. There was no foveal light reflex in either eye, nor was there the typical perifoveal hyperpigmentation pattern in either eye.
Macular optical coherence tomography (OCT) was ordered and, interestingly, both eyes displayed an absence of an anatomical foveal pit. The diagnosis was determined to be fovea plana in both eyes. The OCT testing was repeated at the patient’s follow-up appointment by a different technician, and the results were unchanged.
New vernacular
Foveal hypoplasia or dysplasia may be more familiar terms, however, fovea plana is rather new to the vernacular, representing an anatomical description only. Hypoplasia often conjures functional deficits in vision, often with poor visual acuity. It is also a descriptor for an underdeveloped or poorly demarcated foveal pit and is often associated with a variety of ocular disorders such as congenital nystagmus, albinism, microphthalmos, aniridia, achromatopsia and retinopathy of prematurity. Other features may include a lack of or reduction in macular pigment, retinal/fundus hypopigmentation, iris transillumination defects and chiasmal asymmetry.
Isolated foveal hypoplasia was always thought to be rare, although OCT has now made it more accessible to confirmatory diagnosis. Noval and colleagues scanned 286 children with OCT and showed up to 3% with clinically normal eyes but an anatomically underdeveloped foveal pit bilaterally.
Fovea plana is simply an anatomical description meaning flat pit. Some experts prefer this semantic differentiation to separate the clinically recognized hypoplasia, with its negative functional connotations, from fovea plana, with its simple anatomical description and no such association necessarily with an ocular disorder or poor visual function. The literature documents cases of hypoplasia patients with a wide range of visual acuity between 20/20 and 20/400, and when existing concurrently with an ocular disorder such as albinism, the hypoplasia is localized as the cause for reduced vision, if present.
The foveal pit lacks vasculature and rods, and the inner retinal layers are crowded together around the pit, yielding a clear optical path to the central foveola, which overlies an area of dense cone specialization and outer segment lengthening.
Marmor and colleagues reported on four patients that lacked a foveal pit on OCT and they surprisingly found that a pit was not mandatory for foveal cone specialization anatomically or functionally. Widening of the outer nuclear layer and lengthening of the cone outer segments were displayed on OCT scans with a thickened central retina with continuity of inner retinal layers lacking a pit. The central multifocal electroretinogram readings were normal.
A fundus photo displaying normal perifoveal hyperpigmentation and a positive foveal light reflex.
True purpose of foveal pit
What is the true purpose of the foveal pit then? It is not relegated only to humans. Some fish and reptiles have them, and raptor birds have especially steep foveal pits with an estimated acuity two to eight times greater than ours. The absence of vessels (foveal avascular zone) and overlying retinal layers evidently affords an optical advantage to the centrally located specialized cones, although how much of an advantage is unknown.
OCT technology has certainly opened our eyes, so to speak, about the level of detail and micro-nuances of the retinal tissue that we are able to view clinically now, in vivo. The neural components are present in fovea plana, albeit not laid out in the typical fashion, so perhaps the pit offers that optical fine-tuning of acuity that is needed to obtain “perfect” vision – or perhaps not. The advent of OCT and adaptive optics has injected new life into foveal development, morphology and function research.
This patient’s management
This patient displayed bilateral absence of foveal pits with no other associated ocular or systemic morbidity. It was apparent through the correlation of the funduscopic appearance with the OCT that the mild reduction in best corrected vision was readily identifiable, and further testing, such as electroretinogram, was deemed unnecessary. The father was instructed to bring the child back to the clinic for further testing if vision noticeably declined, although this was not expected to occur.
Cirrus OCT scans displaying a normal anatomical foveal pit.
For this patient’s case, whether his condition is semantically deemed foveal hypoplasia, foveal dysplasia or fovea plana is not necessarily important. The importance lies in educating the parent about the prognosis and implications of the child’s visual status. Although not “perfect” or “normal” 20/20 vision, the boy’s 20/30 vision is functional for most daily activities such as reading, driving and interacting socially. Only a very few select occupations, such as military pilot, would be unachievable due to his level of vision.
The parent and child were reassured that because his vision was only mildly reduced as a result of an anatomical variation, not a pathological process, it is expected that his vision will remain relatively stable into adulthood. Although his refractive error may change as he grows, no spectacles were indicated at this time, as correction did not alter his best potential acuity. It was recommended that he try to sit towards the front of the classroom whenever possible, and a note to his teacher explaining the same was issued. It was also recommended to the father to set up an appointment for the patient’s twin sister to fully evaluate her visual and ophthalmic status.