Classification
It is difficult to classify and assign a group to each and every case of keratitis; as overlapping or concurrent findings tend to obscure the picture.
However, the following simplified topographical and etiological classifications provide a workable knowledge.
Topographical (morphological) classification:
(A) Ulcerative keratitis (corneal ulcer) Corneal ulcer can be further classified variously.
1. Depending on location:
(a) Central corneal ulcer
(b) Peripheral corneal ulcer
2. Depending on purulence:
(a) Purulent corneal ulcer or suppurative corneal
ulcer (most bacterial and fungal corneal ulcers
are suppurative).
(b) Non-purulent corneal ulcers (most of viral, chlamydial and allergic corneal ulcers are non-suppurative).
3. Depending upon association of hypopyon:
(a) Simple corneal ulcer (without hypopyon).
(b) Hypopyon corneal ulcer.
4. Depending upon depth of ulcer:
(a) Superficial corneal ulcer
(b) Deep corneal ulcer
(c) Corneal ulcer with impending perforation
(d) Perforated corneal ulcer.
5. Depending upon slough formation:
(a) Non-sloughing corneal ulcer
(b) Sloughing corneal ulcer
(B) Non-ulcerative keratitis.
1. Superficial keratitis:
(a) Diffuse superficial keratitis
(b) Superficial punctate keratitis (SPK)
2. Deep keratitis:
(a) Non-suppurative
(i) Interstitial keratitis
(ii) Disciform keratitis
(iii) Keratitis profunda
(iv) Sclerosing keratitis
(b) Suppurative deep keratitis
(i) Central corneal abscess
(ii) Posterior corneal abscess.
Etiological classification:
1. Infective keratitis:
(a) Bacterial
(b) Viral
(c) Fungal
(d) Chlamydial
(e) Protozoal
(f) Spirochaetal
2. Allergic keratitis
(a) Phlyctenular keratitis
(b) Vernal keratitis
(c) Atopic keratitis
3. Trophic keratitis
(a) Exposure keratitis
(b) Neuroparalytic keratitis
(c) Keratomalacia
(d) Atheromatous ulcer
4. Keratitis associated with diseases of skin and mucous membrane.
5. Keratitis associated with systemic collagen vascular disorders.
6. Traumatic keratitis, which may be due to mechanical trauma, chemical trauma, thermal burns, radiations.
7. Idiopathic keratitis e.g:
(a) Mooren's corneal ulcer
(b) Superior limbic keratoconjunctivitis
(c) Superficial punctate keratitis of Thygeson.
