presence of a cataract may increase the chance of lens luxation and/or lens induced uveitis, both of which can lead to glaucoma.
DIFFERENTIAL DIAGNOSIS
It is important to first differentiate between exophthalmia and buphthalmos.
Glaucoma in chelonians is usually secondary to outflow obstruction of the aqueous humor, which is most often caused by uveitis, lens luxation, or intraocular neoplasia.
DIAGNOSTICS
Physical examination findings should raise suspicion of buphthalmos, which is confirmed by finding elevated IOP.
Normal IOP in three tortoise species has been reported to be 15.74 ± 0.2 mm Hg (Testudo hermanni), 14.2 ± 1.2 mm Hg (Geochelone denticulata), and 15.3 ± 8.81 mm Hg (Geochelone carbonaria) and in six turtle species at 5.42 ± 0.96 mm Hg (Emys orbicularis), 6.7 ± 1.4 mm Hg (Terrapene sp.), 8.3 ± 1.5 mm Hg (Terrapene sp.), 5.42 ± 1.7 mm Hg (Trachemys scripta elegans), 10.02 ± 0.66 mm Hg (Trachemys scripta elegans), 6.5 ± 1.0 mm Hg (Lepidochelys kempii), 3.8 ± 1.1 mm Hg (Lepidochelys kempii), and 4–9 mm Hg (Caretta caretta).
Since most cases are unilateral, a significant difference in IOP between the eyes may be most indicative of a problem.
Ocular examination and ultrasound are helpful in further evaluating the root cause, although the scleral ossicles can limit visualization.
PATHOLOGICAL FINDINGS
Chronically elevated IOP will lead to pain and blindness.
APPROPRIATE HEALTH CARE
N/A
NUTRITIONAL SUPPORT
Additional nutritional support is not necessary in most cases if the IOP can be brought down.
If needed, tube feeding can be used to provide nutritional support.
CLIENT EDUCATION/HUSBANDRY RECOMMENDATIONS
While buphthalmos can occur in any animal, those with husbandry deficiencies may be at increased risk.
In addition to medical and surgical therapy, maximizing the husbandry of the animal will improve the chance for a successful outcome.
DRUG(S) OF CHOICE
As most of these cases present in a chronic state, vision is often already lost, and medications are used to control pain and slow the disease process during diagnostic evaluation, but enucleation as a salvage procedure is usually indicated.
If acute glaucoma is suspected, it is important to start treatment immediately with topical β‐adrenergic blockers (such as timolol) and CAIs (such as dorzolamide) BID to TID and mannitol (1–2 g/kg IV slowly over 20–30 minutes) to reduce IOP and preserve vision.
If uveitis is suspected, systemic and topical antibiotics (such as ceftazadime 20 mg/kg IM or SC q48–72h) and steroids (prednisolone 0.25–0.5 mg/kg daily or dexamethasone SP 0.04–0.08 mg/kg daily) should also be instituted.
PRECAUTIONS/INTERACTIONS
N/A
PATIENT MONITORING
Serial IOP measurements are useful to determine response to therapy.
EXPECTED COURSE AND PROGNOSIS
Prognosis is related to the underlying cause of the glaucoma, which is not always readily identifiable.
Enucleation of the diseased globe will resolve the issue in most cases.
COMMENTS
N/A
ZOONOTIC POTENTIAL
Depends on the cause of the buphthalmos, but low to most often no zoonotic potential.
SYNONYMS
N/A
ABBREVIATIONS
CAI = carbonic anhydrase inhibitor
IOP = intraocular pressure
IV = intravenous
SC = subcutaneous
Suggested Reading
1 Chittick B, Harms C. Intraocular pressure of juvenile loggerhead sea turtles (Caretta caretta) held in different positions. Vet Rec 2001; 149(19):587–589.
2 Delgado C, Mans C, McLellan GJ, et al. Evaluation of rebound tonometry in red‐eared slider turtles (Trachemys scripta elegans). Vet Ophthalmol 2014; 17(4):261–267.
3 Espinheira Gomes F, Brandão J, Sumner J, et al. Survey of ophthalmic anterior segment findings and intraocular pressure in 95 North American box turtles (Terrapene spp.). Vet Ophthalmol 2016; 19(2):93–101.
4 Gornik KR, Pirie CG, Marrion RM, et al. Ophthalmic variables in rehabilitated juvenile Kemp’s ridley sea turtles (Lepidochelys kempii). J Am Vet Med Assoc 2016; 248(6):673–680.
5 Hochleithner C, Holland M. Ultrasonography. In: Mader, DR, Divers SJ, eds. Current Therapy in Reptile Medicine and Surgery. Saint Louis, MO: Elsevier Saunders; 2014:107–127.
6 Lawton, MPC. Reptilian Ophthalmology. In: Mader DR, ed. Reptile Medicine and Surgery. 2nd ed. St. Louis, MO: Elsevier Saunders; 2006:323–342.
7 Rajaei S, Ansari mood M, Sadjadi R, Azizi F. Measurement of intraocular pressure using Tonovet® in european pond turtle (Emys
