Megalopapilla is a non-progressive

human eye The human eye is a sensory organ in the visual system that reacts to light, visible light allowing eyesight. Other functions include maintaining the circadian rhythm, and Balance (ability), keeping balance. The eye can be considered as a living ...

condition in which the optic nerve head (optic disc) has an enlarged

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

, exceeding 2.1 mm with no other morphological abnormalities.

Clinical features

In megalopapilla the

optic disc The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye. The ganglion cell axons form t ...

diameter exceeds 2.1 mm (or surface area more than 2.5 mm²) with an increased

cup-to-disc ratio The optic cup is the white, cup-like area in the center of the optic disc. The ratio of the size of the optic cup to the optic disc (cup-to-disc ratio, or C/D) is one measure used in the diagnosis of glaucoma. Different C/Ds can be measured horiz ...

. Although the optic disc is looks abnormal, the disc colour, sharpness of disc margin, rim volume, configuration of blood vessels and

intraocular pressure Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk of glaucoma. Most tonometers are calibrated t ...

will be normal.

Visual field The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it i ...

is normal except for an enlarged blind spot.

Visual acuity Visual acuity (VA) commonly refers to the clarity of visual perception, vision, but technically rates an animal's ability to recognize small details with precision. Visual acuity depends on optical and neural factors. Optical factors of the eye ...

may be normal, or occasionally reduced.

Types

There are two types of megalopapilla. Type 1, which is the most common, is bilateral with a normal configuration of the optic cup. Type 2 is unilateral with a superiorly displaced cup that eliminates the adjacent neuro-retinal rim.

Diagnosis and differential diagnosis

Large disc size can be seen in fundus examination by

ophthalmoscopy Ophthalmoscopy, also called funduscopy, is a test that allows a health professional to see inside the fundus of the eye and other structures using an ophthalmoscope (or funduscope). It is done as part of an eye examination and may be done as part ...

. Since OCT is not influenced by disc size, it can be used in differentiating normal and glaucomatous eyes with large discs. Since the clinical appearance of megalopapilla resembles that of glaucomatous optic disc, it should be differentiated from Normal tension glaucoma and other pseudo-glaucomatous diseases. Other conditions that resembles megalopapilla includes coloboma of optic disc and orbital optic disc

glioma A glioma is a type of primary tumor that starts in the glial cells of the brain or spinal cord. They are malignant but some are extremely slow to develop. Gliomas comprise about 30% of all brain and central nervous system tumors and 80% of ...

History

Bock and Franceschetti were the first to use the term megalopapilla to describe larger-than-normal optic disks.

References

{{Congenital malformations and deformations of eye Congenital disorders of eyes