**5. Clinical examination and manifestations**

Acute hydrops initiates with a sudden onset of poor vision and discoloration of the cornea [32]. The disease is confined to the central and paracentral regions and rarely manifests in the peripheral region in case of coexistent pellucid marginal degeneration [33]. In addition to a defective vision, pain and redness are the typical symptoms of this disease [34]. The patients exhibit a definite history of persisting poor vision since childhood and experience progressive vision loss [35]. History of spectacle use should be investigated by reviewing the old optical prescriptions or old spectacles. Past history of high astigmatism, oblique axis and poor best corrected visual acuity are considered as corroborative clinical signs of acute hydrops following progressive keratoconus. Meticulous medical history of ocular allergy, atopic dermatitis, contact lens usage, eye rubbing, and ocular trauma should be documented [36]. Contact lens history, with emphasis on the type, duration of usage, overnight usage while sleeping, and expiry date of the contact lens, is also considered essential [37]. Ocular trauma history, with emphasis on the blunt trauma not withstanding its impact or severity, should also be documented (**Figure 1**) [38].

Examination using a diffused torchlight reveals a whitish lesion over the central or paracentral regions with intense photophobia (**Figure 1**). Conjunctiva shows a sign of circumciliary congestion, and palpebral conjunctiva may be congested depending upon the presence of allergic conjunctivitis. In the absence of oculi allergy, eyes are less susceptible to palpebral congestion. The iris or anterior segment is not visible in case of central hydrops but in cases of paracentral hydrops, the anterior segment is clearly visible through the clear cornea [35].

Slit lamp examination with an oblique slit shows an abnormally thick cornea with clefts in the intrastromal area and Obscuration of Descemet Membrane (DM) due to the blockage of light rays by the edematous cornea [39, 40].
